#!/bin/sh

# Copyright (c) 2016- Jade Allen
# Copyright (c) 2011, 2012 Spawngrid, Inc
# Copyright (c) 2011 Evax Software <contact(at)evax(dot)org>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

# shellcheck disable=SC2250  # Prefer putting braces around variable references even when not strictly required
# shellcheck disable=SC2292  # Prefer `[[ ]]` over `[ ]` for tests in Bash/Ksh
# shellcheck disable=SC2312  # Consider invoking this command separately to avoid masking its return value (or use '|| true' to ignore)

unset ERL_TOP

# Make sure CDPATH doesn't affect cd in case path is relative.
unset CDPATH

if [ -n "$KERL_DEBUG" ]; then
    set -x
    ## Line numbers do not work in dash (aka Debian/Ubuntu sh)
    ## so you may want to change sh to bash to get better debug info
    if [ -n "${LINENO}" ]; then
        PS4='+ ${LINENO}: '
    fi
fi

KERL_VERSION='4.1.0'
OLDEST_OTP_LISTED='17'
OLDEST_OTP_SUPPORTED='24'

ERLANG_DOWNLOAD_URL='https://erlang.org/download'
KERL_CONFIG_STORAGE_FILENAME='.kerl_config'

_KERL_SCRIPT=$0

# Redirect to stderr only if it is a terminal, otherwise mute
stderr() {
    if [ -t 1 ]; then
        if [ -z "$l" ] || [ "$KERL_COLORIZE" -eq 0 ]; then
            echo "$*" 1>&2
        else
            left="$(colorize "$l")"
            # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
            right="$(tput $KERL_COLOR_RESET)"
            echo "${left}$*${right}" 1>&2
            unset -v l
        fi
    elif [ -n "$KERL_DEBUG" ] && [ -n "$CI" ]; then
        echo "$*"
    fi
}

nocolor() {
    # $1: log entry

    stderr "$1"
}

usage_exit() {
    # $1: usage tip

    l=error stderr "usage: ${_KERL_SCRIPT} $1"
    exit 1
}

error() {
    # $1: log entry

    l=error stderr "ERROR: $1"
}

warn() {
    # $1: log entry
    # $2: use 'noprefix' if you want to omit WARNING:

    if [ "$2" != "noprefix" ]; then
        l=warn stderr "WARNING: $1"
    else
        l=warn stderr "$1"
    fi
}

notice() {
    # $1: log entry

    l=notice stderr "$1"
}

success() {
    # $1: log entry

    l=success stderr "$1"
}

tip() {
    # $1: log entry

    l=tip stderr "$1"
}

init_build_logfile() {
    # $1: release
    # $2: build name

    BUILD_LOGFILE="$KERL_BUILD_DIR/$2/otp_build_$1.log"
    rm -f "$BUILD_LOGFILE"
    touch "$BUILD_LOGFILE"
    tip "Initializing (build) log file at $BUILD_LOGFILE".
}

log_build_entry() {
    # $1: log entry

    echo "$1" >>"$BUILD_LOGFILE" 2>&1
}

log_build_cmd() {
    # $*: command
    build_cmd="$*"

    eval "$build_cmd" >>"$BUILD_LOGFILE" 2>&1
}

init_install_logfile() {
    # $1: release
    # $2: build name

    INSTALL_LOGFILE="$KERL_BUILD_DIR/$2/otp_install_$1.log"
    rm -f "$INSTALL_LOGFILE"
    touch "$INSTALL_LOGFILE"
    tip "Initializing (install) log file at $INSTALL_LOGFILE".
}

log_install_cmd() {
    # $*: command
    install_cmd="$*"

    eval "$install_cmd" >>"$INSTALL_LOGFILE" 2>&1
}

# Check if tput is available for colorize
tp=$(tput sgr0 1>/dev/null 2>&1 && printf "OK" || printf "")
if [ -z "$tp" ]; then
    if [ -z "$CI" ]; then
        nocolor "Colorization disabled as 'tput' (via 'ncurses') seems to be unavailable."
    fi
    KERL_COLOR_AVAILABLE=0
    KERL_COLORIZE=0 # Force disabling colorization
else
    KERL_COLOR_AVAILABLE=1
    if [ -n "$KERL_COLOR_D" ]; then
        KERL_COLOR_RESET="setaf $KERL_COLOR_D"
    else
        KERL_COLOR_RESET="sgr0"
    fi
fi

colorize() {
    case "$1" in
    "error")
        ret="$(tput setaf "${KERL_COLOR_E:=1}")"
        ;;
    "warn")
        ret="$(tput setaf "${KERL_COLOR_W:=3}")"
        ;;
    "notice")
        ret="$(tput setaf "${KERL_COLOR_N:=4}")"
        ;;
    "tip")
        ret="$(tput setaf "${KERL_COLOR_T:=6}")"
        ;;
    "success")
        ret="$(tput setaf "${KERL_COLOR_S:=2}")"
        ;;
    *)
        ret="$(tput setaf "${KERL_COLOR_D:=9}")"
        ;;
    esac
    printf "%b" "$ret"
}

autoclean() {
    if [ "${KERL_AUTOCLEAN:=1}" -eq 1 ]; then
        notice "Auto cleaning all artifacts except the log file..."
        tip "(use KERL_AUTOCLEAN=0 to keep build on failure, if desired)"
        # Cleaning current build
        cd - 1>/dev/null 2>&1 || return 0
        test -n "$1" && ${_KERL_SCRIPT} cleanup "$1"
    else
        warn "auto cleaning (on failure) disabled!"
    fi
}

TMP_DIR=${TMP_DIR:-'/tmp'}
if [ -z "$HOME" ]; then
    error "\$HOME is empty or not set."
    exit 1
fi

# Default values
KERL_BASE_DIR=${KERL_BASE_DIR:="$HOME"/.kerl}
KERL_CONFIG=${KERL_CONFIG:="$HOME"/.kerlrc}
KERL_DOWNLOAD_DIR=${KERL_DOWNLOAD_DIR:="${KERL_BASE_DIR:?}"/archives}
KERL_BUILD_DIR=${KERL_BUILD_DIR:="${KERL_BASE_DIR:?}"/builds}
KERL_GIT_DIR=${KERL_GIT_DIR:="${KERL_BASE_DIR:?}"/gits}
KERL_GIT_BASE=https://raw.githubusercontent.com/kerl/kerl/master
KERL_COLORIZE=${KERL_COLORIZE:=$KERL_COLOR_AVAILABLE}
KERL_INCLUDE_RELEASE_CANDIDATES=${KERL_INCLUDE_RELEASE_CANDIDATES:=no}
KERL_CHECK_BUILD_PACKAGES=${KERL_CHECK_BUILD_PACKAGES:="yes"}

act_on_kerl_cfgs() {
    # $1: kerl config. flags (we're only interested in the keys)
    # $2: action - cache | restore (default)

    for _KERL_CFG in $1; do
        k=$(echo "$_KERL_CFG" | \sed 's|\(.*\)=.*|\1|')

        if [ "$2" = cache ]; then
            eval "_KERL_CFG_VAR=\$${k}"
            eval "_KERL_TARGET_VAR=__${k}"
        elif [ "$2" = restore ]; then
            eval "_KERL_CFG_VAR=\$__${k}"
            eval "_KERL_TARGET_VAR=${k}"
        fi
        if [ -n "${_KERL_CFG_VAR}" ]; then
            # shellcheck disable=SC2154  # _KERL_TARGET_VAR is referenced but not assigned
            eval "$_KERL_TARGET_VAR=\"$_KERL_CFG_VAR\""
        fi
    done
}

# List is [<config_key>=<def_value>, ...]
_KERL_CFGS="
OTP_GITHUB_URL=https://github.com/erlang/otp
KERL_CONFIGURE_OPTIONS=
KERL_CONFIGURE_APPLICATIONS=
KERL_CONFIGURE_DISABLE_APPLICATIONS=
KERL_SASL_STARTUP=
KERL_DEPLOY_SSH_OPTIONS=
KERL_DEPLOY_RSYNC_OPTIONS=
KERL_INSTALL_MANPAGES=
KERL_INSTALL_HTMLDOCS=
KERL_BUILD_PLT=
KERL_BUILD_DOCS=
KERL_DOC_TARGETS=chunks
KERL_BUILD_BACKEND=
KERL_RELEASE_TARGET=
"
act_on_kerl_cfgs "$_KERL_CFGS" "cache"
eval "$_KERL_CFGS"

# ensure the base dir exists
mkdir -p "$KERL_BASE_DIR" || exit 1

# source the config file if available
if [ -f "$KERL_CONFIG" ]; then
    # shellcheck source=/dev/null
    . "$KERL_CONFIG"
fi

act_on_kerl_cfgs "$_KERL_CFGS" "restore"

if [ -z "$KERL_SASL_STARTUP" ]; then
    INSTALL_OPT='-minimal'
else
    INSTALL_OPT='-sasl'
fi

if [ -z "$KERL_BUILD_BACKEND" ]; then
    KERL_BUILD_BACKEND='git'
fi
if [ "$KERL_BUILD_BACKEND" = 'git' ]; then
    KERL_USE_AUTOCONF=1
elif [ "$KERL_BUILD_BACKEND" != 'tarball' ]; then
    error "unhandled value KERL_BUILD_BACKEND=${KERL_BUILD_BACKEND}."
    tip "KERL_BUILD_BACKEND must be either 'git' (default), or 'tarball'."
    exit 1
fi

KERL_SYSTEM=$(uname -s)
case "$KERL_SYSTEM" in
Darwin | FreeBSD | OpenBSD)
    MD5SUM='openssl md5'
    MD5SUM_FIELD=2
    SED_OPT=-E
    ;;
*)
    MD5SUM=md5sum
    MD5SUM_FIELD=1
    SED_OPT=-r
    ;;
esac

k_usage() {
    nocolor "kerl: build and install Erlang/OTP"
    nocolor "usage: ${_KERL_SCRIPT} <command> [options ...]"
    nocolor ""
    nocolor "  <command>       Command to be executed"
    nocolor ""
    nocolor "Valid commands are:"
    nocolor "  build           Build specified release or git repository"
    nocolor "  install         Install the specified release at the given location"
    nocolor "  build-install   Builds and installs the specified release or git repository at the given location"
    nocolor "  deploy          Deploy the specified installation to the given host and location"
    nocolor "  update          Update the list of available releases from your source provider"
    nocolor "  list            List releases, builds and installations"
    nocolor "  delete          Delete builds and installations"
    nocolor "  path            Print the path of a given installation"
    nocolor "  active          Print the path of the active installation"
    nocolor "  plt             Print Dialyzer PLT path for the active installation"
    nocolor "  status          Print available builds and installations"
    nocolor "  prompt          Print a string suitable for insertion in prompt"
    nocolor "  cleanup         Remove compilation artifacts (use after installation)"
    nocolor "  emit-activate   Print the activate script"
    nocolor "  upgrade         Fetch and install the most recent kerl release"
    nocolor "  version         Print current version (current: $KERL_VERSION)"
    exit 1
}

if [ $# -eq 0 ]; then k_usage; fi

get_releases() {
    # $1: path to file otp_releases

    if [ "$KERL_BUILD_BACKEND" = 'git' ]; then
        if ! get_git_releases "$1"; then
            return 1
        fi
    else
        if ! get_tarball_releases "$1"; then
            return 1
        fi
    fi
}

get_git_releases() {
    tmp="$(mktemp "$TMP_DIR"/kerl.XXXXXX)"
    # shellcheck disable=SC2154  # OTP_GITHUB_URL is referenced but not assigned
    git ls-remote --tags --refs "$OTP_GITHUB_URL" >"$tmp"
    ret=$?
    notice "Getting releases from GitHub..."
    if [ "$ret" -eq 0 ]; then
        if ! cut <"$tmp" -f2 |
            cut -d'/' -f3- |
            sed "$SED_OPT" \
                -e '# Delete all tags starting with ":" as to not mix' \
                -e '# them with the prefixed lines we`re generating next.' \
                -e '/^:/d' \
                \
                -e '# Prefix "OTP*" release lines with the crux of their versions.' \
                -e '#  - "OTP_R16B01_RC1"  =>  ":16B01_RC1 OTP_R16B01_RC1"' \
                -e '#  - "OTP_R16B03"      =>  ":16B03 OTP_R16B03"' \
                -e '#  - "OTP-17.0"        =>  ":17.0 OTP-17.0"' \
                -e '#  - "OTP-17.3.1"      =>  ":17.3.1 OTP-17.3.1"' \
                -e '#  - "OTP-19.0-rc1"    =>  ":19.0-rc1 OTP-19.0-rc1"' \
                -e '#  - "OTP-19.0-rc2"    =>  ":19.0-rc2 OTP-19.0-rc2"' \
                -e 's/^(OTP[-_](R?([0-9][^ :]*).*))/:\3 \2/' \
                \
                -e '# Delete all lines that did not get prefixed above.' \
                -e '/^[^:]/d' \
                \
                -e '# Move the colon markers preceding each version prefix' \
                -e '# as to precede the tag suffix instead, which will make' \
                -e '# throwing the version prefixes easier later on.' \
                -e '#  - ":16B01_RC1 OTP_R16B03"  =>  "16B01_RC1 :OTP_R16B01_RC1"' \
                -e '#  -     ":16B03 OTP_R16B03"  =>  "16B03 :OTP_R16B03"' \
                -e '#  -      ":17.0 OTP_R16B03"  =>  "17.0 :OTP-17.0"' \
                -e '#  -    ":17.3.1 OTP_R16B03"  =>  "17.3.1 :OTP-17.3.1"' \
                -e '#  -  ":19.0-rc1 OTP_R16B03"  =>  "19.0-rc1 :OTP-19.0-rc1"' \
                -e '#  -  ":19.0-rc2 OTP_R16B03"  =>  "19.0-rc2 :OTP-19.0-rc2"' \
                -e 's/^:([^ ]+) /\1 :/' \
                \
                -e '# Repeatedly replace sequences of one or more dots, dashes' \
                -e '# or underscores, within each version prefix, with single' \
                -e '# space characters.' \
                -e '#  - "16B01_RC1 :OTP_R16B01_RC1"  =>  "16B01 RC1 :OTP_R16B01_RC1"' \
                -e '#  -     "16B03 :OTP_R16B03"      =>  "16B03 :OTP_R16B03"' \
                -e '#  -      "17.0 :OTP-17.0"        =>  "17 0 :OTP-17.0"' \
                -e '#  -    "17.3.1 :OTP-17.3.1"      =>  "17 3 1 :OTP-17.3.1"' \
                -e '#  -  "19.0-rc1 :OTP-19.0-rc1"    =>  "19 0 rc1 :OTP-19.0-rc1"' \
                -e '#  -  "19.0-rc2 :OTP-19.0-rc2"    =>  "19 0 rc2 :OTP-19.0-rc2"' \
                -e ':loop' \
                -e 's/^([^:]*)[.-]+([^:]*) :/\1 \2 :/' \
                -e 't loop' \
                \
                -e '# Repeatedly replace "A", "B", or "C" separators, within each' \
                -e '# version prefix, with " 0 ", " 1 " and " 2 ", respectively.' \
                -e '#  - "16B01 RC1 :OTP_R16B01_RC1"  =>  "16 1 01 RC1 :OTP_R16B01_RC1"' \
                -e '#  -     "16B03 :OTP_R16B03"      =>  "16 1 03 :OTP_R16B03"' \
                -e ':loop2' \
                -e 's/^(.*[0-9]+)A([^:]*) :/\1 0 \2 :/' \
                -e 's/^(.*[0-9]+)B([^:]*) :/\1 1 \2 :/' \
                -e 's/^(.*[0-9]+)C([^:]*) :/\1 2 \2 :/' \
                -e 't loop2' \
                \
                -e '# Repeatedly replace space-release candidate infixes, within' \
                -e '# each version prefix, with a leading zero followed by' \
                -e '# the candidate number.' \
                -e '# - "16 1 01 RC1 :OTP_R16B01_RC1"  =>  "16 1 01 0 1 :OTP_R16B01_RC1"' \
                -e '# -      "19 0 rc1 :OTP-19.0-rc1"  =>  "19 0 0 1 :OTP-19.0-rc1"' \
                -e '# -      "19 0 rc2 :OTP-19.0-rc2"  =>  "19 0 0 2 :OTP-19.0-rc2"' \
                -e ':loop3' \
                -e 's/^([^:]* )(rc|RC)([0-9]+)(( [^:]*)?) :/\10 \3\4 :/' \
                -e 't loop3' \
                \
                -e '# Repeatedly prefix single digits, within each version prefix,' \
                -e '# with leading zeroes.' \
                -e '#  - "16 1 01 0 1 :OTP_R16B01_RC1"  =>  "16 01 01 00 01 :OTP_R16B01_RC1"' \
                -e '#  -     "16 1 03 :OTP_R16B03"      =>  "16 01 03 :OTP_R16B03"' \
                -e '#  -        "17 0 :OTP-17.0"        =>  "17 00 :OTP-17.0"' \
                -e '#  -      "17 3 1 :OTP-17.3.1"      =>  "17 03 01 :OTP-17.3.1"' \
                -e '#  -    "19 0 0 1 :OTP-19.0-rc1"    =>  "19 00 00 01 :OTP-19.0-rc.1"' \
                -e '#  -    "19 0 0 2 :OTP-19.0-rc2"    =>  "19 00 00 02 :OTP-19.0-rc.2"' \
                -e ':loop4' \
                -e 's/^([^:]*[^0-9:])([0-9])(([^0-9][^:]*)?) :/\10\2\3 :/' \
                -e 't loop4' \
                \
                -e '# Suffix each version prefix with 00 as to not compare ':' with a number.' \
                -e '#  - "16 01 01 00 01 :OTP_R16B01_RC1"  =>  "16 01 01 00 01 00 :OTP_R16B01_RC1"' \
                -e '#  -       "16 01 03 :OTP_R16B03"      =>  "16 01 03 00 :OTP_R16B03"' \
                -e '#  -          "17 00 :OTP-17.0""       =>  "17 00 00 :OTP-17.0"' \
                -e '#  -       "17 03 01 :OTP-17.3.1"      =>  "17 03 01 00 :OTP-17.3.1"' \
                -e '#  -    "19 00 00 01 :OTP-19.0-rc.1"   =>  "19 00 00 01 00 :OTP-19.0-rc.1"' \
                -e '#  -    "19 00 00 02 :OTP-19.0-rc.2"   =>  "19 00 00 02 00 :OTP-19.0-rc.2"' \
                -e 's/^([^:]+) :/\1 00 :/' |
            LC_ALL=C sort -n |
            cut -d':' -f2- |
            tee "$1" >/dev/null 2>&1; then
            error "file $1 does not appear to be writable."
            return 1
        fi
        rm -f "$tmp"
        return 0
    else
        rm -f "$tmp"
        error "git ls-remote --tags --refs $OTP_GITHUB_URL returned $ret!"
        return 1
    fi
}

_curl() {
    # $1: <file> to write output to, instead of stdout (if body_only function only returns body)
    # $2: URL to consider
    # $3: extra options

    if [ "$1" != body_only ]; then
        _curl_extra="--output $1 --write-out %{http_code}"
    fi
    # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
    \curl -q --silent --location --fail $2 $3 $_curl_extra
}

unpack() {
    # $1: <file> to extract to current directory

    tar -x --no-same-owner --no-same-permissions -zf "$1"
}

get_tarball_releases() {
    tmp="$(mktemp "$TMP_DIR"/kerl.XXXXXX)"
    notice "Getting releases from erlang.org..."
    http_code=$(_curl "$tmp" "$ERLANG_DOWNLOAD_URL")
    if [ 200 = "$http_code" ]; then
        if ! sed "$SED_OPT" \
            -e 's/^.*<[aA] [hH][rR][eE][fF]=\"otp_src_([-0-9A-Za-z_.]+)\.tar\.gz\">.*$/\1/' \
            -e '/^R1|^[0-9]/!d' "$tmp" |
            sed -e 's/^R\(.*\)/\1:R\1/' |
            sed -e 's/^\([^\:]*\)$/\1-z:\1/' |
            sort |
            cut -d: -f2 |
            tee "$1" >/dev/null 2>&1; then
            error "file $1 does not appear to be writable."
            return 1
        fi
        rm -f "$tmp"
        return 0
    else
        rm -f "$tmp"
        error "$ERLANG_DOWNLOAD_URL returned $http_code!"
        return 1
    fi
}

update_checksum_file() {
    if [ "$KERL_BUILD_BACKEND" != 'git' ]; then
        notice "Getting checksum file from erlang.org..."
        http_code=$(_curl "$KERL_DOWNLOAD_DIR"/MD5 "$ERLANG_DOWNLOAD_URL"/MD5)
        if [ 200 != "$http_code" ]; then
            error "$ERLANG_DOWNLOAD_URL/MD5 returned $http_code!"
            return 1
        fi
    fi
}

ensure_checksum_file() {
    if [ ! -s "$KERL_DOWNLOAD_DIR"/MD5 ] && ! update_checksum_file; then
        return 1
    fi
}

check_releases() {
    # $1: force?: if force, the list is always recreated

    if [ "$1" = force ]; then
        if ! rm -f "${KERL_BASE_DIR:?}"/otp_releases 2>/dev/null; then
            error "${KERL_BASE_DIR:?}/otp_releases cannot be removed."
            return 1
        fi
    fi
    if [ ! -f "$KERL_BASE_DIR"/otp_releases ] &&
        ! get_releases "$KERL_BASE_DIR"/otp_releases; then
        return 1
    fi
}

is_valid_release() {
    if ! check_releases; then
        return 1
    fi
    while read -r rel; do
        if [ "$1" = "$rel" ]; then
            return 0
        fi
    done <"$KERL_BASE_DIR"/otp_releases
    error "'$1' is not a valid Erlang/OTP release."
    return 1
}

get_release_from_name() {
    # $1: build_name

    if [ -f "$KERL_BASE_DIR"/otp_builds ]; then
        while read -r l; do
            rel=$(echo "$l" | cut -d, -f1)
            name=$(echo "$l" | cut -d, -f2)
            if [ "$name" = "$1" ]; then
                echo "$rel"
                return 0
            fi
        done <"$KERL_BASE_DIR"/otp_builds
    fi
    return 1
}

is_valid_installation() {
    if [ -f "$KERL_BASE_DIR"/otp_installations ]; then
        while read -r l; do
            name=$(echo "$l" | cut -d' ' -f1)
            path=$(echo "$l" | cut -d' ' -f2)
            if [ "$name" = "$1" ] || [ "$path" = "$1" ]; then
                if [ -f "$path"/activate ]; then
                    return 0
                fi
            fi
        done <"$KERL_BASE_DIR"/otp_installations
    fi
    return 1
}

is_build_name_used() {
    if [ -f "$KERL_BASE_DIR"/otp_builds ]; then
        while read -r l; do
            name=$(echo "$l" | cut -d, -f2)
            if [ "$name" = "$1" ]; then
                return 0
            fi
        done <"$KERL_BASE_DIR"/otp_builds
    fi
    return 1
}

is_older_than_x_days() {
    # $1: file to check
    # $2: age in days

    old_file=$(find "$1" -type f -mtime "$2")
    if [ -n "$old_file" ]; then
        return 0
    else
        return 1
    fi
}

lock() {
    # $1: build | install
    # $2: folder to act on

    if [ -f "$2/$1.lock" ]; then
        if is_older_than_x_days "$2/$1.lock" "+14"; then
            unlock "$1" "$2"
        else
            error "trying to $1 in $2, but lock file ($2/$1.lock) exists!"
            exit 1
        fi
    else
        mkdir -p "$2"
        touch "$2/$1.lock"
    fi
}

unlock() {
    # $1: build | install
    # $2: folder to act on

    rm -f "$2/$1.lock"
}

lock_build() {
    # $_KERL_BUILD_DIR is global
    lock "build" "$_KERL_BUILD_DIR"
}

unlock_build() {
    # $_KERL_BUILD_DIR is global
    unlock "build" "$_KERL_BUILD_DIR"
}

lock_install() {
    # $_KERL_INSTALL_DIR is global
    lock "install" "$_KERL_INSTALL_DIR"
}

unlock_install() {
    # $_KERL_INSTALL_DIR is global
    unlock "install" "$_KERL_INSTALL_DIR"
}

exit_build() {
    # $1: error message
    # $2: build name

    if [ -n "$1" ]; then
        error "$1"
    fi

    tmp=$(save_logfile)

    if [ -n "$2" ]; then
        if [ "${KERL_AUTOCLEAN:=1}" -eq 1 ]; then
            rm -Rf "${KERL_BUILD_DIR:?}/$2"
        fi
    fi

    unlock_build
    restore_logfile "$tmp"

    exit 1
}

exit_install() {
    # $1: error message

    if [ -n "$1" ]; then
        error "$1"
    fi

    unlock_install

    exit 1
}

do_git_build() {
    git_url=$1
    git_version=$2
    build_name=$3

    if is_build_name_used "$build_name"; then
        error "there's already a build named '$build_name'."
        exit_build
    fi

    GIT=$(printf '%s' "$git_url" | $MD5SUM | cut -d ' ' -f "$MD5SUM_FIELD")

    _KERL_BUILD_DIR="$KERL_GIT_DIR/$GIT"

    mkdir -p "$KERL_GIT_DIR" || exit_build
    cd "$KERL_GIT_DIR" || exit_build
    notice "Checking out Erlang/OTP git repository from $git_url..."
    if [ ! -d "$GIT" ] &&
        ! git clone -q --mirror "$git_url" "$GIT" >/dev/null 2>&1; then
        exit_build "mirroring remote git repository ($_KERL_BUILD_DIR exists?)."
    fi

    lock_build

    cd "$_KERL_BUILD_DIR" || exit_build
    if ! git remote update --prune >/dev/null 2>&1; then
        exit_build "updating remote git repository."
    fi
    rm -Rf "${KERL_BUILD_DIR:?}/$build_name"

    mkdir -p "$KERL_BUILD_DIR/$build_name" || exit_build
    cd "$KERL_BUILD_DIR/$build_name" || exit_build "" "$build_name"
    if ! git clone -l "$_KERL_BUILD_DIR" otp_src_git >/dev/null 2>&1; then
        exit_build "cloning local git repository." "$build_name"
    fi

    cd "$KERL_BUILD_DIR/$build_name/otp_src_git" || exit_build "" "$build_name"
    if ! git checkout "$git_version" >/dev/null 2>&1 &&
        ! git checkout -b "$git_version" "$git_version" >/dev/null 2>&1; then
        exit_build "could not checkout specified version." "$build_name"
    fi

    if [ ! -x otp_build ]; then
        exit_build "not a valid Erlang/OTP repository." "$build_name"
    fi

    notice "Building (git) Erlang/OTP $git_version; please wait..."

    if [ -z "$KERL_BUILD_AUTOCONF" ]; then
        KERL_USE_AUTOCONF=1
    fi

    if ! _do_build 'git' "$build_name"; then
        exit_build "" "$build_name"
    fi

    success "Erlang/OTP '$build_name' (from git) has been successfully built."
    if ! list_add builds git,"$build_name"; then
        exit_build "" "$build_name"
    fi

    unlock_build
}

get_otp_version() {
    echo "$1" | sed "$SED_OPT" -e 's/R?([0-9]{1,2}).+/\1/'
}

show_configuration_warnings() {
    # $1 is log file
    # $2 is section header (E.g. "APPLICATIONS DISABLED")
    # Find the row number for the section we are looking for
    INDEX=$(\grep -n -m1 "$2" "$1" | cut -d: -f1)

    # If there are no warnings, the section won't appear in the log
    if [ -n "$INDEX" ]; then
        # Skip the section header, find the end line and skip it
        # then print the results indented
        tail -n +$((INDEX + 3)) "$1" |
            sed -n '1,/\*/p' |
            awk -F: -v logfile="$1" -v section="$2" \
                'BEGIN { printf "%s (See: %s)\n", section, logfile }
                 /^[^\*]/ { print " *", $0 }
                 END { print "" } '
    fi
}

show_logfile() {
    # $1 reason
    # $2 log file

    error "$1"
    tail "$2" 1>&2
    nocolor ""
    tip "Please see $2 for full details."
}

show_build_logfile() {
    # $1 reason

    show_logfile "$1" "$BUILD_LOGFILE"
}

show_install_logfile() {
    # $1 reason

    show_logfile "$1" "$INSTALL_LOGFILE"
}

maybe_patch() {
    # $1 = OS platform e.g., Darwin, etc
    # $2 = OTP release

    release=$(get_otp_version "$2")
    case "$1" in
    Darwin) ;;
    SunOS) ;;
    *) ;;
    esac
}

do_normal_build() {
    # $1: release
    # $2: build name

    if ! is_valid_release "$1"; then
        exit_build
    fi
    if is_build_name_used "$2"; then
        error "there's already a build named '$2'."
        exit_build
    fi

    _KERL_BUILD_DIR="$KERL_BUILD_DIR/$2"
    lock_build

    FILENAME=""
    if ! download "$1"; then
        exit_build
    fi

    if [ ! -d "$_KERL_BUILD_DIR/$FILENAME" ]; then
        notice "Extracting source code for normal build..."
        UNTARDIRNAME="$_KERL_BUILD_DIR/$FILENAME-kerluntar-$$"
        rm -rf "$UNTARDIRNAME"
        mkdir -p "$UNTARDIRNAME" || exit_build
        # github tarballs have a directory in the form of "otp[_-]TAGNAME"
        # Ericsson tarballs have the classic otp_src_RELEASE pattern
        # Standardize on Ericsson format because that's what the rest of the script expects
        (cd "$UNTARDIRNAME" && unpack "$KERL_DOWNLOAD_DIR/$FILENAME".tar.gz &&
            cp -rfp ./* "$_KERL_BUILD_DIR/otp_src_$1")
        rm -rf "$UNTARDIRNAME"
    fi

    notice "Building (normal) Erlang/OTP $1 ($2); please wait..."
    if ! _do_build "$1" "$2"; then
        exit_build
    fi
    success "Erlang/OTP $1 ($2) has been successfully built."
    if ! list_add builds "$1,$2"; then
        exit_build
    fi

    unlock_build
}

_flags() {
    # We used to munge the LD and DED flags for clang 9/10 shipped with
    # High Sierra (macOS 10.13), Mojave (macOS 10.14) and Catalina
    # (macOS 10.15)
    #
    # As of OTP 20.1 that is (apparently) no longer necessary and
    # in OTP 24 breaks stuff. See thread and comment here:
    # https://github.com/erlang/otp/issues/4821#issuecomment-845914942
    case "$KERL_SYSTEM" in
    Darwin)
        # Make sure we don't overwrite stuff that someone who
        # knows better than us set.
        if [ -z "$CC" ]; then
            CC='clang'
        fi

        CFLAGS="${CFLAGS:-}" CC="$CC" "$@"
        ;;
    *)
        CFLAGS="${CFLAGS:-}" "$@"
        ;;
    esac
}

_dpkg() {
    # gratefully stolen from
    # https://superuser.com/questions/427318/test-if-a-package-is-installed-in-apt
    # returns 0 (true) if found, 1 otherwise
    echo "dpkg-query -Wf'\${db:Status-abbrev}' \"$1\" 2>/dev/null | \grep -q '^i'"
}

_rpm() {
    echo "rpm -q \"$1\""
}

_apk() {
    echo "apk -e info \"$1\""
}

common_ALL_pkgs="gcc make"
common_ALL_BUILD_BACKEND_git_pkgs="automake autoconf"
common_debian_pkgs="${common_ALL_pkgs} libssl-dev libncurses5-dev g++"

# To add package guessing magic for your Linux distro/package,
# create a variable named _KPP_<distro>_pkgs where the content
# is an array with packages, and then create a unique probe
# command, in variable _KPP_<distro>_probe to check from the package manager.
# It should return 0 if package installation is Ok, non-0 otherwise.

_KPP_alpine_pkgs="${common_ALL_pkgs} openssl-dev ncurses-dev g++"
_KPP_alpine_probe="_apk"

_KPP_debian_pkgs=${common_debian_pkgs}
_KPP_debian_probe="_dpkg"

_KPP_fedora_pkgs="${common_ALL_pkgs} openssl-devel ncurses-devel g++"
_KPP_fedora_probe="_rpm"

_KPP_linuxmint_pkgs=${common_debian_pkgs}
_KPP_linuxmint_probe="_dpkg"

_KPP_pop_pkgs=${common_debian_pkgs}
_KPP_pop_probe="_dpkg"

_KPP_rhel_pkgs="${common_ALL_pkgs} openssl-devel ncurses-devel gcc-c++"
_KPP_rhel_probe="_rpm"

_KPP_ubuntu_pkgs=${common_debian_pkgs}
_KPP_ubuntu_probe="_dpkg"

parse_os_release() {
    # $1: path to os-release
    # returns:
    # - 2 if release ID is not found in os-release file
    os_release_id0=$(\grep "^ID=" "$1")
    os_release_id=$(echo "${os_release_id0}" | \sed 's|.*=||' | \sed 's|"||g')
    os_release_pretty_name0=$(\grep "^PRETTY_NAME=" "$1")
    os_release_pretty_name=$(echo "${os_release_pretty_name0}" | \sed 's|.*=||' | \sed 's|"||g')
    log_build_entry "[packages] Found ${os_release_pretty_name} with ID ${os_release_id}"
    if [ -z "${os_release_id}" ]; then
        log_build_entry "[packages] Release ID not found in $1"
        echo "2"
    else
        log_build_entry "[packages] Release ID found in $1: ${os_release_id}"
        echo "${os_release_id}"
    fi
}

get_id_from_os_release_files() {
    # returns:
    # 1 - if no release files exist
    files="/etc/os-release /usr/lib/os-release"
    for file in ${files}; do
        if [ -f "${file}" ]; then
            parsed=$(parse_os_release "${file}")
            if [ "${parsed}" != "2" ]; then
                break
            fi
        fi
    done

    if [ -z "${parsed}" ]; then
        log_build_entry "[packages] Found no file in: ${files}. Bailing out..."
        echo "1"
    fi

    echo "${parsed}"
}

probe_pkgs() {
    os_release_id=$(get_id_from_os_release_files)

    if [ "${os_release_id}" = "1" ]; then
        msg="[packages] Unable to determine Linux distro (no release files); not checking build packages."
        log_build_entry "${msg}"
        warn "${msg}"
        return 0
    elif [ "${os_release_id}" = "2" ]; then
        msg="[packages] Unable to determine Linux distro (no ID); not checking build packages."
        log_build_entry "${msg}"
        warn "${msg}"
        return 0
    fi

    kpp=$(eval echo \$_KPP_"${os_release_id}"_pkgs)
    if [ "$KERL_BUILD_BACKEND" = 'git' ]; then
        kpp="${common_ALL_BUILD_BACKEND_git_pkgs} ${kpp}"
    fi

    if [ -n "${kpp}" ]; then
        log_build_entry "[packages] Found package declarations for your Linux distro: ${os_release_id}"
        for pkg in ${kpp}; do
            cmd=$(eval echo "\$_KPP_${os_release_id}_probe ${pkg}")
            probe=$(${cmd})
            eval "${probe}" >/dev/null 2>&1
            probe_res=$?
            if [ "${probe_res}" != 0 ]; then
                msg="[packages] Probe failed for ${pkg} (distro: ${os_release_id}): probe \"${probe}\" returned ${probe_res}"
                log_build_entry "${msg}"
                warn "${msg}"
            else
                log_build_entry "[packages] Probe success for ${pkg} (distro: ${os_release_id})!"
            fi
        done
    else
        msg="[packages] Unknown Linux distro ${os_release_id}; not checking build packages."
        log_build_entry "${msg}"
        warn "${msg}"
    fi
}

save_logfile() {
    tmp="$(mktemp "$TMP_DIR"/kerl.XXXXXX)"
    test -f "$BUILD_LOGFILE" && cp -f "$BUILD_LOGFILE" "$tmp"
    echo "$tmp"
}

restore_logfile() {
    # $1: logfile to restore

    mkdir -p "$(dirname "$BUILD_LOGFILE")"
    test -n "$BUILD_LOGFILE" && mv -f "$1" "$BUILD_LOGFILE"
    rm -f "$1"
}

fail_do_build() {
    # $1: error message
    # $2: build name
    # $3: release

    show_build_logfile "$1"
    tmp=$(save_logfile)

    if [ -n "$2" ]; then
        autoclean "$2"
    fi

    if [ -n "$3" ]; then
        list_remove builds "$3 $2"
    fi

    restore_logfile "$tmp"
}

uname_r_label() {
    echo "uname -r"
}

uname_r() {
    eval "$(uname_r_label)"
}

_do_build() {
    init_build_logfile "$1" "$2"
    log_build_entry "*** $(date) - kerl build $1 ***"
    log_build_entry "Build options:"
    log_build_cmd "env | grep KERL_BUILD_ | xargs -n1 echo \"*\""

    case "$KERL_SYSTEM" in
    Darwin)
        # Ensure that the --enable-darwin-64bit flag is set on all macOS
        # That way even on older Erlangs we get 64 bit Erlang builds
        # macOS has been mandatory 64 bit for a while
        if ! echo "$KERL_CONFIGURE_OPTIONS" | \grep 'darwin-64bit' >/dev/null 2>&1; then
            KERL_CONFIGURE_OPTIONS="$KERL_CONFIGURE_OPTIONS "--enable-darwin-64bit
        fi

        # Attempt to use brew to discover if and where openssl has been
        # installed unless the user has already explicitly set it.

        if ! echo "$KERL_CONFIGURE_OPTIONS" | \grep 'with-ssl' >/dev/null 2>&1; then
            whichbrew=$(command -v brew)
            if [ -n "$whichbrew" ] && [ -x "$whichbrew" ]; then
                brew_prefix=$(brew --prefix openssl@1.1)
                if [ -n "$brew_prefix" ] && [ -d "$brew_prefix" ]; then
                    KERL_CONFIGURE_OPTIONS="$KERL_CONFIGURE_OPTIONS "--with-ssl=$brew_prefix
                fi
            fi
        fi
        ;;
    Linux)
        # We implement a "best effort" attempt to discover if a Linux distro has the
        # packages needed to build Erlang. We will always assume the user
        # knows better than us and are going to go ahead and try to build
        # Erlang anyway. But at least there will be a clear warning to the
        # user if a build fails.
        if [ "${KERL_CHECK_BUILD_PACKAGES}" = "yes" ]; then
            probe_pkgs
        fi
        ;;
    *) ;;
    esac

    ERL_TOP="$KERL_BUILD_DIR/$2/otp_src_$1"
    if ! cd "$ERL_TOP"; then
        fail_do_build "couldn't cd into $ERL_TOP"
        return 1
    fi

    # Set configuration flags given applications white/black lists
    if [ -n "$KERL_CONFIGURE_APPLICATIONS" ]; then
        for app in $KERL_CONFIGURE_APPLICATIONS; do
            case "$KERL_CONFIGURE_OPTIONS" in
            *"--with-$app"*)
                tip "Option '--with-$app' in KERL_CONFIGURE_OPTIONS is superfluous."
                ;;
            *)
                KERL_CONFIGURE_OPTIONS="$KERL_CONFIGURE_OPTIONS --with-$app"
                ;;
            esac
        done
    fi
    if [ -n "$KERL_CONFIGURE_DISABLE_APPLICATIONS" ]; then
        for app in $KERL_CONFIGURE_DISABLE_APPLICATIONS; do
            case "$KERL_CONFIGURE_OPTIONS" in
            *"--without-$app"*)
                tip "Option '--without-$app' in KERL_CONFIGURE_OPTIONS is superfluous."
                ;;
            *)
                KERL_CONFIGURE_OPTIONS="$KERL_CONFIGURE_OPTIONS --without-$app"
                ;;
            esac
        done
    fi

    # Check to see if configuration options need to be stored or have changed
    TMPOPT="${TMP_DIR}/kerloptions.$$"
    {
        echo "This is kerl's control file for build configuration."
        echo "Please don't edit it manually!"
        echo "CFLAGS: ${CFLAGS:-}"
        echo "KERL_CONFIGURE_OPTIONS: $KERL_CONFIGURE_OPTIONS"
        echo "$(uname_r_label): $(uname_r)"
    } >>"$TMPOPT"
    SUM=$($MD5SUM "$TMPOPT" | cut -d ' ' -f "$MD5SUM_FIELD")
    # Check for a .kerl_config.md5 file
    if [ -e ./"$KERL_CONFIG_STORAGE_FILENAME".md5 ]; then
        # Compare our current options to the saved ones
        read -r OLD_SUM <./"$KERL_CONFIG_STORAGE_FILENAME".md5
        if [ "$SUM" != "$OLD_SUM" ]; then
            notice "Configuration options changed. Re-configuring..."
            rm -f configure
            mv "$TMPOPT" ./"$KERL_CONFIG_STORAGE_FILENAME"
            echo "$SUM" >./"$KERL_CONFIG_STORAGE_FILENAME".md5
        else
            # configure options are the same
            rm -f "$TMPOPT"
        fi
    else
        # no file exists, so write one
        mv "$TMPOPT" "$KERL_CONFIG_STORAGE_FILENAME"
        echo "$SUM" >"$KERL_CONFIG_STORAGE_FILENAME".md5
    fi

    # Don't apply patches to "custom" git builds. We have no idea if they will apply
    # cleanly or not.
    if [ "$1" != 'git' ]; then
        maybe_patch "$KERL_SYSTEM" "$1"
    fi

    if [ -n "$KERL_USE_AUTOCONF" ]; then
        # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
        if ! log_build_cmd "./otp_build autoconf && _flags ./otp_build configure $KERL_CONFIGURE_OPTIONS"; then
            fail_do_build "configure failed." "$2" "$1"
            return 1
        fi
    else
        # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
        if ! log_build_cmd "_flags ./otp_build configure $KERL_CONFIGURE_OPTIONS"; then
            fail_do_build "configure failed." "$2" "$1"
            return 1
        fi

    fi
    if echo "$KERL_CONFIGURE_OPTIONS" | \grep -- '--enable-native-libs' >/dev/null 2>&1; then
        log_build_cmd "make clean"
        # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
        if ! log_build_cmd "_flags ./otp_build configure $KERL_CONFIGURE_OPTIONS"; then
            fail_do_build "configure failed." "$2" "$1"
            return 1
        fi
    fi

    for SECTION in 'APPLICATIONS DISABLED' \
        'APPLICATIONS INFORMATION' \
        'DOCUMENTATION INFORMATION'; do
        show_configuration_warnings "$BUILD_LOGFILE" "$SECTION"
    done

    if [ -n "$KERL_CONFIGURE_APPLICATIONS" ]; then
        \find ./lib -maxdepth 1 -type d -exec touch -f {}/SKIP \;
        for app in $KERL_CONFIGURE_APPLICATIONS; do
            if ! rm ./lib/"$app"/SKIP; then
                fail_do_build "couldn't prepare '$app' application for building." "$2" "$1"
                return 1
            fi
        done
    fi
    if [ -n "$KERL_CONFIGURE_DISABLE_APPLICATIONS" ]; then
        for app in $KERL_CONFIGURE_DISABLE_APPLICATIONS; do
            if ! touch -f ./lib/"$app"/SKIP; then
                fail_do_build "couldn't disable '$app' application for building." "$2" "$1"
                return 1
            fi
        done
    fi

    # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
    if ! log_build_cmd "_flags ./otp_build boot -a $KERL_CONFIGURE_OPTIONS"; then
        fail_do_build "build failed." "$2" "$1"
        return 1
    fi
    if [ -n "$KERL_BUILD_DOCS" ]; then
        notice "Building docs..."
        # shellcheck disable=SC2154  # KERL_DOC_TARGETS is referenced but not assigned
        if ! log_build_cmd "make docs DOC_TARGETS=\"$KERL_DOC_TARGETS\""; then
            fail_do_build "building docs failed." "$2" "$1"
            return 1
        fi
        if ! log_build_cmd "make release_docs DOC_TARGETS=\"$KERL_DOC_TARGETS\" RELEASE_ROOT=$KERL_BUILD_DIR/$2/release_$1"; then
            fail_do_build "release of docs failed." "$2" "$1"
            return 1
        fi
    fi

    if [ -n "$KERL_RELEASE_TARGET" ]; then
        # where `$TYPE` is `opt`, `gcov`, `gprof`, `debug`, `valgrind`, `asan` or `lcnt`.
        for r_type in $KERL_RELEASE_TARGET; do
            case $r_type in
            opt | debug)
                notice "Also building for Erlang/OTP $1 ($2) $r_type VM; please wait..."
                if ! cd "$ERL_TOP"; then
                    fail_do_build "couldn't cd into $ERL_TOP" "$2" "$1"
                    return 1
                fi
                if ! log_build_cmd "make TYPE=$r_type ERL_TOP=$ERL_TOP"; then
                    fail_do_build "build of '$r_type' VM failed." "$2" "$1"
                    return 1
                fi
                ;;
            gcov | gprof | valgrind | asan | lcnt)
                notice "Also building for Erlang/OTP $1 ($2) $r_type VM; please wait..."
                if ! cd "$ERL_TOP/erts/emulator"; then
                    fail_do_build "couldn't cd into $ERL_TOP/erts/emulator" "$2" "$1"
                    return 1
                fi
                if ! log_build_cmd "make $r_type ERL_TOP=$ERL_TOP"; then
                    fail_do_build "build of '$r_type' VM failed." "$2" "$1"
                    return 1
                fi
                ;;
            *)
                warn "runtime type '$r_type' is invalid!"
                ;;
            esac
        done
    fi
}

do_build_install() {
    release_or_git=$1
    git_url=$2
    git_version=$3
    build_name=$4
    directory=$5

    if is_valid_installation "$build_name"; then
        error "there's already an installation named '$build_name'. Skipping build step..."
        exit 1
    fi

    # This is also done on do_install, but saves the build time in case of error
    if ! is_valid_install_path "$directory"; then
        exit 1
    fi

    if [ "$release_or_git" = "git" ]; then
        ${_KERL_SCRIPT} build git "$git_url" "$git_version" "$build_name"
    else
        release="$release_or_git"
        ${_KERL_SCRIPT} build "$release" "$build_name"
    fi

    status=$?
    if [ "$status" -ne 0 ]; then
        error "build failed! Skipping installation step..."
        exit 1
    fi

    ${_KERL_SCRIPT} install "$build_name" "$directory"
}

# emit_activate: outputs (via cat) the content of the 'activate' script, as used by kerl (sh/bash)
# @param $1/release: the <release> argument in e.g. kerl build <release> <build_name>
# @param $2/build_name: the <build_name> argument in e.g. kerl build <release> <build_name>
# @param $3/directory: the [directory] argument in e.g. kerl install <build_name> [directory]
emit_activate() {
    release=$1
    build_name=$2
    directory=$3

    cat << \
        =======
#!/bin/sh

# shellcheck disable=SC2250  # Prefer putting braces around variable references even when not strictly required

if type kerl_deactivate 2>/dev/null | \grep -qw function; then
    kerl_deactivate
fi

_KERL=$(command -v kerl)
if [ -n "\$_KERL" ]; then
    _KERL_VERSION=\$(\$_KERL version)
fi
if [ -n "\$_KERL_VERSION" ] && [ "\$_KERL_VERSION" != "$KERL_VERSION" ]; then
    echo "WARNING: this Erlang/OTP installation appears to be stale. Please consider reinstalling."
    echo "         It was created with kerl $KERL_VERSION, and the current version is \$_KERL_VERSION."
fi
unset _KERL_VERSION
unset _KERL

add_cleanup() {
    _KERL_CLEANUP="
    \$1
    \$_KERL_CLEANUP
    "
}

set -o allexport

_KERL_ACTIVE_DIR="$directory"
add_cleanup "unset _KERL_ACTIVE_DIR"

if [ -n "\$BASH" ] || [ -n "\$ZSH_VERSION" ]; then
    add_cleanup "hash -r"
fi

_KERL_PATH_REMOVABLE="$directory/bin"
PATH="\${_KERL_PATH_REMOVABLE}:\$PATH"
add_cleanup "PATH=\"\\\$(echo \"\\\$PATH\" | sed -e \"s%\$_KERL_PATH_REMOVABLE:%%\")\""
unset _KERL_PATH_REMOVABLE

_KERL_ERL_CALL_REMOVABLE=\$(\\find $directory -type d -path "*erl_interface*/bin" 2>/dev/null)
if [ -n "\$_KERL_ERL_CALL_REMOVABLE" ]; then
    PATH="\${_KERL_ERL_CALL_REMOVABLE}:\$PATH"
    add_cleanup "PATH=\"\\\$(echo \"\\\$PATH\" | sed -e \"s%\$_KERL_ERL_CALL_REMOVABLE:%%\")\""
fi
unset _KERL_ERL_CALL_REMOVABLE

_KERL_MANPATH_REMOVABLE="$directory/lib/erlang/man:$directory/man"
if [ -n "\${MANPATH+x}" ]; then
    if [ -n "\$MANPATH" ]; then
        MANPATH="\${_KERL_MANPATH_REMOVABLE}:\$MANPATH"
    else
        MANPATH="\${_KERL_MANPATH_REMOVABLE}"
    fi
else
    MANPATH="\${_KERL_MANPATH_REMOVABLE}"
    add_cleanup "
        if [ -z \"\\\$MANPATH\" ]; then
            unset MANPATH
        fi
    "
fi
add_cleanup "MANPATH=\"\\\$(echo \"\\\$MANPATH\" | sed -r \"s%\$_KERL_MANPATH_REMOVABLE:?%%\")\""
unset _KERL_MANPATH_REMOVABLE

if [ -n "\${REBAR_PLT_DIR+x}" ]; then
    add_cleanup "REBAR_PLT_DIR=\"\$REBAR_PLT_DIR\""
else
    add_cleanup "unset REBAR_PLT_DIR"
fi
REBAR_PLT_DIR="$directory"

if [ -n "\${REBAR_CACHE_DIR+x}" ]; then
    add_cleanup "REBAR_CACHE_DIR=\"\$REBAR_CACHE_DIR\""
else
    add_cleanup "unset REBAR_CACHE_DIR"
fi
REBAR_CACHE_DIR="$directory/.cache/rebar3"

# https://twitter.com/mononcqc/status/877544929496629248
_KERL_KERNEL_HISTORY=\$(echo "\$ERL_AFLAGS" | \\grep 'kernel shell_history' || true)
if [ -z "\$_KERL_KERNEL_HISTORY" ]; then
    if [ -n "\${ERL_AFLAGS+x}" ]; then
        add_cleanup "ERL_AFLAGS=\"\$ERL_AFLAGS\""
    else
        add_cleanup "unset ERL_AFLAGS"
    fi
    if [ -n "\$ERL_AFLAGS" ]; then
        ERL_AFLAGS="-kernel shell_history enabled \$ERL_AFLAGS"
    else
        ERL_AFLAGS="-kernel shell_history enabled"
    fi
fi
unset _KERL_KERNEL_HISTORY

# shellcheck source=/dev/null
if [ -f "$KERL_CONFIG" ]; then
    . "$KERL_CONFIG"
fi
if [ -n "\$KERL_ENABLE_PROMPT" ]; then
    if [ -n "\${PS1+x}" ]; then
        add_cleanup "PS1=\"\$PS1\""
    else
        add_cleanup "unset PS1"
    fi
    if [ -n "\$KERL_PROMPT_FORMAT" ]; then
        _KERL_PROMPT_FORMAT="\$KERL_PROMPT_FORMAT"
    else
        _KERL_PROMPT_FORMAT="(%BUILDNAME%)"
    fi
    _KERL_PRMPT=\$(echo "\$_KERL_PROMPT_FORMAT" | sed 's^%RELEASE%^$release^;s^%BUILDNAME%^$build_name^')
    PS1="\$_KERL_PRMPT\$PS1"
    unset KERL_ENABLE_PROMPT
    unset KERL_PROMPT_FORMAT
    unset _KERL_PRMPT
    unset _KERL_PROMPT_FORMAT
fi

if [ -n "\$BASH" ] || [ -n "\$ZSH_VERSION" ]; then
    hash -r
fi

set +o allexport

unset add_cleanup

eval "
kerl_deactivate() {
    set -o allexport
    \$_KERL_CLEANUP
    unset -f kerl_deactivate
    set +o allexport
}
"
unset _KERL_CLEANUP
=======
}

# emit_activate_fish: outputs (via cat) the content of the 'activate' script, as used by kerl (fish)
# @param $1/release: the <release> argument in e.g. kerl build <release> <build_name>
# @param $2/build_name: the <build_name> argument in e.g. kerl build <release> <build_name>
# @param $3/directory: the [directory] argument in e.g. kerl install <build_name> [directory]
emit_activate_fish() {
    release=$1
    build_name=$2
    directory=$3

    cat << \
        =======
if functions -q kerl_deactivate
    kerl_deactivate
end

set _KERL (command -v kerl)

if test -n "\$_KERL"
  set _KERL_VERSION (\$_KERL version)
end

if test -n "\$_KERL_VERSION" -a "\$_KERL_VERSION" != "$KERL_VERSION"
  echo "WARNING: this Erlang/OTP installation appears to be stale. Please consider reinstalling."
  echo "         It was created with kerl $KERL_VERSION, and the current version is \$_KERL_VERSION."
end

set -e _KERL_VERSION _KERL

set -x _KERL_ACTIVE_DIR "$directory"
set -p _KERL_CLEANUP "set -e _KERL_ACTIVE_DIR;"

function _kerl_remove_el_ --description 'remove elements from array'
    set path_var \$argv[1]
    set elements \$argv[2]
    echo "
        for el in \\\$\$elements;
            if set -l index (contains -i -- \\\$el \\\$\$path_var);
                set -e \$path_var[1][\\\$index];
            end;
        end;
    "
end

set -x _KERL_PATH_REMOVABLE "$directory/bin"
set -l _KERL_ERL_CALL_REMOVABLE (find "$directory" -type d -path "*erl_interface*/bin" 2>/dev/null)
if test -n "\$_KERL_ERL_CALL_REMOVABLE"
    set -a _KERL_PATH_REMOVABLE \$_KERL_ERL_CALL_REMOVABLE
end
set -p _KERL_CLEANUP "set -e _KERL_PATH_REMOVABLE;"
set -xp PATH \$_KERL_PATH_REMOVABLE
set -p _KERL_CLEANUP (_kerl_remove_el_ PATH _KERL_PATH_REMOVABLE)

set -x _KERL_MANPATH_REMOVABLE "$directory/lib/erlang/man" "$directory/man"
set -p _KERL_CLEANUP "set -e _KERL_MANPATH_REMOVABLE;"
if set -q MANPATH
    if test -n "\$MANPATH"
        set -xp MANPATH \$_KERL_MANPATH_REMOVABLE
    else
        set -x MANPATH \$_KERL_MANPATH_REMOVABLE
    end
else
    set -x MANPATH \$_KERL_MANPATH_REMOVABLE
    set -p _KERL_CLEANUP "
        if test -z \"\\\$MANPATH\"
            set -e MANPATH
        end
    "
end
set -p _KERL_CLEANUP (_kerl_remove_el_ MANPATH _KERL_MANPATH_REMOVABLE)

functions -e _kerl_remove_el_

if set -q REBAR_PLT_DIR
    set -p _KERL_CLEANUP "set -x REBAR_PLT_DIR \"\$REBAR_PLT_DIR\";"
else
    set -p _KERL_CLEANUP "set -e REBAR_PLT_DIR;"
end
set -x REBAR_PLT_DIR "$directory"

if set -q REBAR_CACHE_DIR
    set -p _KERL_CLEANUP "set -x REBAR_CACHE_DIR \"\$REBAR_CACHE_DIR\";"
else
    set -p _KERL_CLEANUP "set -e REBAR_CACHE_DIR;"
end
set -x REBAR_CACHE_DIR "$directory/.cache/rebar3"

if test -f "$KERL_CONFIG.fish"
    source "$KERL_CONFIG.fish"
end
if set --query KERL_ENABLE_PROMPT
    if functions -q fish_prompt
        functions --copy fish_prompt _kerl_saved_prompt
        set -p _KERL_CLEANUP "
            functions --copy _kerl_saved_prompt fish_prompt
            functions --erase _kerl_saved_prompt;
        "
    end
    function fish_prompt
        printf "%b" "($build_name)"
        _kerl_saved_prompt
    end
    set -p _KERL_CLEANUP "functions --erase fish_prompt;"
end

eval "function kerl_deactivate -S --description \"deactivate erlang environment\"
    \$_KERL_CLEANUP
    functions -e kerl_deactivate
end"
set -e _KERL_CLEANUP
=======
}

# emit_activate_csh: outputs (via cat) the content of the 'activate' script, as used by kerl (csh)
# @param $1/release: the <release> argument in e.g. kerl build <release> <build_name>
# @param $2/build_name: the <build_name> argument in e.g. kerl build <release> <build_name>
# @param $3/directory: the [directory] argument in e.g. kerl install <build_name> [directory]
emit_activate_csh() {
    release=$1
    build_name=$2
    directory=$3

    cat << \
        =======
# This file must be used with "source bin/activate.csh" *from csh*.
# You cannot run it directly.

# Unset irrelevant variables.
which kerl_deactivate >& /dev/null
if ( \$status == 0 ) then
    kerl_deactivate
endif

set _KERL = $(command -v kerl)

if ( "\$_KERL" != "" ) then
  set _KERL_VERSION = \`\$_KERL version\`
endif

if ( \$?_KERL_VERSION ) then
  if ( "\$_KERL_VERSION" != "" && "\$_KERL_VERSION" != "$KERL_VERSION" ) then
    echo "WARNING: this Erlang/OTP installation appears to be stale. Please consider reinstalling."
    echo "         It was created with kerl $KERL_VERSION, and the current version is \$_KERL_VERSION."
  endif
endif

unset _KERL_VERSION _KERL

alias add_cleanup 'set _KERL_CLEANUP = '\"'\!:1*; \$_KERL_CLEANUP'\"''
alias _kerl_remove_el 'setenv \!:1 \`echo \$\!:1 | sed -r "s%\!:2*%%"\`'
alias _kerl_cleanup_manpath 'eval "if ( '\''\${MANPATH}'\'' == '\'''\'' ) then \\\\
    unsetenv MANPATH \\\\
endif"'

set _KERL_CLEANUP = ""

set _KERL_ACTIVE_DIR = "$directory"
add_cleanup unset _KERL_ACTIVE_DIR

if ( \$?REBAR_CACHE_DIR ) then
    add_cleanup setenv REBAR_CACHE_DIR \$REBAR_CACHE_DIR
else
    add_cleanup unsetenv REBAR_CACHE_DIR
endif
setenv REBAR_CACHE_DIR "$directory/.cache/rebar3"

if ( \$?REBAR_PLT_DIR ) then
    add_cleanup setenv REBAR_PLT_DIR \$REBAR_PLT_DIR
else
    add_cleanup unsetenv REBAR_PLT_DIR
endif
setenv REBAR_PLT_DIR "$directory"

set _KERL_PATH_REMOVABLE = "$directory/bin"
add_cleanup setenv PATH \$PATH
setenv PATH "\${_KERL_PATH_REMOVABLE}:\$PATH"
unset _KERL_PATH_REMOVABLE

set _KERL_MANPATH_REMOVABLE = "$directory/lib/erlang/man:$directory/man"
if ( \$?MANPATH ) then
    if ( "\$MANPATH" == "" ) then
        setenv MANPATH "\${_KERL_MANPATH_REMOVABLE}"
    else
        setenv MANPATH "\${_KERL_MANPATH_REMOVABLE}:\$MANPATH"
    endif
else
    add_cleanup _kerl_cleanup_manpath
    setenv MANPATH "\${_KERL_MANPATH_REMOVABLE}"
endif
add_cleanup _kerl_remove_el MANPATH \${_KERL_MANPATH_REMOVABLE}
add_cleanup _kerl_remove_el MANPATH \${_KERL_MANPATH_REMOVABLE}:
unset _KERL_MANPATH_REMOVABLE

set _KERL_ERL_CALL_REMOVABLE = $(\find "$directory" -type d -path '*erl_interface*/bin' 2>/dev/null)
if ("\$_KERL_ERL_CALL_REMOVABLE" != "") then
    add_cleanup setenv PATH \$PATH
    setenv PATH "\${_KERL_ERL_CALL_REMOVABLE}:\$PATH"
endif
unset _KERL_ERL_CALL_REMOVABLE

if ( -f "$KERL_CONFIG.csh" ) then
    source "$KERL_CONFIG.csh"
endif

if ( \$?KERL_ENABLE_PROMPT ) then
    if ( \$?KERL_PROMPT_FORMAT ) then
        set FRMT = "\$KERL_PROMPT_FORMAT"
    else
        set FRMT = "(%BUILDNAME%)"
    endif
    set PROMPT = \`echo "\$FRMT" | sed 's^%RELEASE%^$release^;s^%BUILDNAME%^$build_name^'\`
    if ( \$?prompt ) then
        add_cleanup set prompt = '\$prompt'
        set prompt = "\$PROMPT\$prompt"
    else
        add_cleanup unset prompt
        set prompt = "\$PROMPT"
    endif
    unset FRMT PROMPT
endif

rehash

unalias add_cleanup
eval 'alias kerl_deactivate "\$_KERL_CLEANUP; unalias kerl_deactivate _kerl_remove_el _kerl_cleanup_manpath"'
unset _KERL_CLEANUP
=======
}

do_install() {
    build_name=$1

    if ! is_valid_install_path "$2"; then
        exit_install
    fi

    _KERL_INSTALL_DIR="$2"
    lock_install

    if ! rel=$(get_release_from_name "$build_name"); then
        exit_install "no build named '$build_name'."
    fi

    absdir=$(cd "$_KERL_INSTALL_DIR" && pwd)

    notice "Installing Erlang/OTP $rel ($build_name) in $absdir..."
    ERL_TOP="$KERL_BUILD_DIR/$build_name/otp_src_$rel"
    cd "$ERL_TOP" || exit_install
    init_install_logfile "$rel" "$build_name"

    prev_build_kernel_release=$(grep <"$ERL_TOP"/"$KERL_CONFIG_STORAGE_FILENAME" -o "^$(uname_r_label): \(.*\)\$" | sed -n "s|^$(uname_r_label): \(.*\)\$|\1|p")
    if [ "$(uname_r)" != "$prev_build_kernel_release" ]; then
        warn "this Erlang/OTP build appears to be stale. It was created with kernel release"
        warn "         '$prev_build_kernel_release' while currently your system's kernel release is" "noprefix"
        warn "         '$(uname_r)'." "noprefix"
        warn "         You should consider removing the build with 'kerl delete build ...' and" "noprefix"
        warn "         re-installing it with 'kerl build-install ...'" "noprefix"
    fi

    if ! log_install_cmd "ERL_TOP=$ERL_TOP ./otp_build release -a $absdir && cd $absdir && ./Install $INSTALL_OPT $absdir"; then
        show_install_logfile "install of Erlang/OTP $rel ($build_name), in $absdir, failed!"
        exit_install
    fi

    for r_type in $KERL_RELEASE_TARGET; do
        case "$r_type" in
        opt | debug)
            notice "Installing Erlang/OTP $rel ($build_name) ${r_type} VM in $absdir..."
            cd "$ERL_TOP" || exit_install
            if ! log_install_cmd "TYPE=$r_type ERL_TOP=$ERL_TOP ./otp_build release -a $absdir"; then
                show_install_logfile "install Erlang/OTP $rel ($build_name) of type '$r_type', in $absdir, failed"
                exit_install
            fi
            ;;
        *)
            BEAM_TYPE_SMP=$(\find . -name "beam.${r_type}.smp")
            if [ -n "$BEAM_TYPE_SMP" ]; then
                ERL_CHILD_SETUP_TYPE=$(\find . -name "erl_child_setup.${r_type}")
                notice "Installing Erlang/OTP $rel ($build_name) ${r_type} VM in $absdir..."
                cp "$BEAM_TYPE_SMP" "$absdir"/erts-*/bin/
                cp "$ERL_CHILD_SETUP_TYPE" "$absdir"/erts-*/bin/
            fi
            ;;
        esac
    done

    [ -n "$KERL_RELEASE_TARGET" ] && [ -f bin/cerl ] && cp bin/cerl "$absdir/bin"

    if ! list_add installations "$build_name $absdir"; then
        exit_install
    fi

    emit_activate "$rel" "$build_name" "$absdir" >"$absdir"/activate
    emit_activate_fish "$rel" "$build_name" "$absdir" >"$absdir"/activate.fish
    emit_activate_csh "$rel" "$build_name" "$absdir" >"$absdir"/activate.csh

    if [ -n "$KERL_BUILD_DOCS" ]; then
        if ! cd "$ERL_TOP"; then
            error "couldn't cd into $ERL_TOP."
            exit_install
        fi
        if ! log_install_cmd "ERL_TOP=$ERL_TOP make release_docs DOC_TARGETS=\"$KERL_DOC_TARGETS\" RELEASE_ROOT=$absdir"; then
            show_install_logfile "couldn't install docs for Erlang/OTP $rel ($build_name) in $absdir"
            exit_install
        fi
    else
        if [ "$KERL_BUILD_BACKEND" = 'tarball' ]; then
            if [ "$rel" != 'git' ]; then
                if [ -n "$KERL_INSTALL_MANPAGES" ]; then
                    notice "Fetching and installing man pages..."
                    if ! download_manpages "$rel"; then
                        exit_install
                    fi
                fi

                if [ -n "$KERL_INSTALL_HTMLDOCS" ]; then
                    notice "Fetching and installing HTML docs..."
                    if ! download_htmldocs "$rel"; then
                        exit_install
                    fi
                fi
            fi
        fi
    fi

    KERL_CONFIG_STORAGE_PATH="$KERL_BUILD_DIR/$build_name/otp_src_$rel/$KERL_CONFIG_STORAGE_FILENAME"
    [ -e "$KERL_CONFIG_STORAGE_PATH" ] && cp "$KERL_CONFIG_STORAGE_PATH" "$absdir/$KERL_CONFIG_STORAGE_FILENAME"

    if [ -n "$KERL_BUILD_PLT" ]; then
        notice "Building Dialyzer PLT..."
        if ! build_plt "$absdir"; then
            exit_install
        fi
    fi

    PID=$$
    if command -v apk >/dev/null 2>&1; then
        # Running on Alpine Linux, assuming non-exotic shell
        SHELL_SUFFIX=''
    elif [ "$(\ps -p "$PID" -o ppid= | tr -d ' ')" -eq 0 ]; then
        SHELL_SUFFIX=''
    else
        PARENT_PID=$(\ps -p "$PID" -o ppid= | tr -d ' ') || exit 1
        PARENT_CMD=$(\ps -p "$PARENT_PID" -o ucomm | tail -n 1 | tr -d ' ')
        case "$PARENT_CMD" in
        fish)
            SHELL_SUFFIX='.fish'
            ;;
        csh)
            SHELL_SUFFIX='.csh'
            ;;
        *)
            SHELL_SUFFIX=''
            ;;
        esac
    fi

    tip "You can activate this installation running the following command:"
    tip ". $absdir/activate$SHELL_SUFFIX"
    tip "Later on, you can leave the installation typing:"
    tip "kerl_deactivate"

    unlock_install
}

download_manpages() {
    FILENAME=otp_doc_man_$1.tar.gz
    if ! tarball_download "$FILENAME"; then
        return 1
    fi
    notice "Extracting man pages..."
    (cd "$absdir" && unpack "$KERL_DOWNLOAD_DIR/$FILENAME")
}

download_htmldocs() {
    FILENAME=otp_doc_html_"$1".tar.gz
    if ! tarball_download "$FILENAME"; then
        return 1
    fi
    notice "Extracting HTML docs..."
    (cd "$absdir" && mkdir -p html && cd html && unpack "$KERL_DOWNLOAD_DIR/$FILENAME")
}

build_plt() {
    dialyzerd="$1"/dialyzer
    if ! mkdir -p "$dialyzerd"; then
        error "couldn't create folder $dialyzerd."
        return 1
    fi
    plt="$dialyzerd"/plt
    build_log="$dialyzerd"/build.log
    dirs=$(\find "$1"/lib -maxdepth 2 -name ebin -type d -exec dirname {} \;)
    apps=$(for app in $dirs; do basename "$app" | cut -d- -f1; done | \grep -Ev 'erl_interface|jinterface' | xargs echo)
    # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
    "$1"/bin/dialyzer --output_plt "$plt" --build_plt --apps $apps >>"$build_log" 2>&1
    status=$?
    if [ "$status" -eq 0 ] || [ "$status" -eq 2 ]; then
        success "Done building $plt."
        return 0
    else
        error "building Dialyzer PLT; see $build_log for details."
        return 1
    fi
}

do_plt() {
    ACTIVE_PATH="$1"
    if [ -n "$ACTIVE_PATH" ]; then
        plt="$ACTIVE_PATH"/dialyzer/plt
        if [ -f "$plt" ]; then
            notice "The Dialyzer PLT for the active installation is:"
            success "$plt"
            return 0
        else
            warn "there is no Dialyzer PLT for the active installation."
            return 1
        fi
    else
        warn "no Erlang/OTP installation is currently active."
        return 1
    fi
}

print_buildopts() {
    buildopts="$1/$KERL_CONFIG_STORAGE_FILENAME"
    if [ -f "$buildopts" ]; then
        notice "The build options for the active installation are:"
        cat "$buildopts"
    else
        error "the build options for the active installation are not available."
    fi
}

do_deploy() {
    if [ -z "$1" ]; then
        error "no host given!"
        exit 1
    fi
    host="$1"

    if ! is_valid_installation "$2"; then
        error "'$2' is not a kerl-managed Erlang/OTP installation."
        exit 1
    fi
    rel="$(get_name_from_install_path "$2")"
    path="$2"
    remotepath="$path"

    if [ -n "$3" ]; then
        remotepath="$3"
    fi

    # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
    # shellcheck disable=SC2154  # KERL_DEPLOY_SSH_OPTIONS is referenced but not assigned
    if ! ssh $KERL_DEPLOY_SSH_OPTIONS "$host" true >/dev/null 2>&1; then
        error "couldn't ssh to $host."
        exit 1
    fi

    notice "Cloning Erlang/OTP $rel ($path) to $host ($remotepath)..."

    # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
    # shellcheck disable=SC2154  # KERL_DEPLOY_RSYNC_OPTIONS is referenced but not assigned
    if ! rsync -aqz -e "ssh $KERL_DEPLOY_SSH_OPTIONS" $KERL_DEPLOY_RSYNC_OPTIONS "$path/" "$host:$remotepath/"; then
        error "couldn't rsync Erlang/OTP $rel ($path) to $host ($remotepath)."
        exit 1
    fi

    # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
    # shellcheck disable=SC2029  # Note that, unescaped, this expands on the client side
    if ! ssh $KERL_DEPLOY_SSH_OPTIONS "$host" "cd \"$remotepath\" && env ERL_TOP=\"\$(pwd)\" ./Install $INSTALL_OPT \"\$(pwd)\" >/dev/null 2>&1"; then
        error "couldn't install Erlang/OTP $rel to $host ($remotepath)."
        exit 1
    fi

    # shellcheck disable=SC2086  # Double quote to prevent globbing and word splitting
    # shellcheck disable=SC2029  # Note that, unescaped, this expands on the client side
    if ! ssh $KERL_DEPLOY_SSH_OPTIONS "$host" "cd \"$remotepath\" && sed -i -e \"s#$path#\"\$(pwd)\"#g\" activate"; then
        error "couldn't completely install Erlang/OTP $rel to $host ($remotepath)."
        exit 1
    fi

    tip "On $host, you can activate this installation running the following command:"
    tip ". $remotepath/activate"
    tip "Later on, you can leave the installation typing:"
    tip "kerl_deactivate"
}

# Quoted from https://github.com/mkropat/sh-realpath
# LICENSE: MIT

realpath() {
    canonicalize_path "$(resolve_symlinks "$1")"
}

resolve_symlinks() {
    _resolve_symlinks "$1"
}

_resolve_symlinks() {
    _assert_no_path_cycles "$@" || return 0

    if path=$(readlink -- "$1"); then
        dir_context=$(dirname -- "$1")
        _resolve_symlinks "$(_prepend_dir_context_if_necessary "$dir_context" "$path")" "$@"
    else
        printf '%s\n' "$1"
    fi
}

_prepend_dir_context_if_necessary() {
    if [ "$1" = . ]; then
        printf '%s\n' "$2"
    else
        _prepend_path_if_relative "$1" "$2"
    fi
}

_prepend_path_if_relative() {
    case "$2" in
    /*) printf '%s\n' "$2" ;;
    *) printf '%s\n' "$1/$2" ;;
    esac
}

_assert_no_path_cycles() {
    target=$1
    shift

    for path in "$@"; do
        if [ "$path" = "$target" ]; then
            return 1
        fi
    done
}

canonicalize_path() {
    if [ -d "$1" ]; then
        _canonicalize_dir_path "$1"
    else
        _canonicalize_file_path "$1"
    fi
}

_canonicalize_dir_path() {
    (cd "$1" 2>/dev/null && pwd -P)
}

_canonicalize_file_path() {
    dir=$(dirname -- "$1")
    file=$(basename -- "$1")
    (cd "$dir" 2>/dev/null && printf '%s/%s\n' "$(pwd -P)" "$file")
}

# END QUOTE

is_valid_install_path() {
    # don't allow installs into .erlang because
    # it's a special configuration file location for OTP
    if [ "$(basename -- "$1")" = '.erlang' ]; then
        error "you cannot install a build into .erlang, as it is a special configuration file location for OTP!"
        return 1
    fi

    candidate=$(realpath "$1")
    canonical_home=$(realpath "$HOME")
    canonical_base_dir=$(realpath "$KERL_BASE_DIR")

    # don't allow installs into home directory
    if [ "$candidate" = "$canonical_home" ]; then
        error "you cannot install a build into $HOME. It's a really bad idea!"
        return 1
    fi

    # don't install into our base directory either.
    if [ "$candidate" = "$canonical_base_dir" ]; then
        error "you cannot install a build into $KERL_BASE_DIR."
        return 1
    fi

    INSTALLED_NAME=$(get_name_from_install_path "$candidate")
    if [ -n "$INSTALLED_NAME" ]; then
        error "installation '$INSTALLED_NAME' already registered for this location ($1)."
        return 1
    fi

    # if the install directory exists,
    # do not allow installs into a directory that is not empty
    if [ -e "$1" ]; then
        if [ ! -d "$1" ]; then
            error "$1 is not a directory."
            return 1
        else
            count=$(\find "$1" | wc -l)
            if [ "$count" -ne 1 ]; then
                error "$1 does not appear to be an empty directory."
                return 1
            fi
        fi
    fi
}

maybe_remove() {
    candidate=$(realpath "$1")
    canonical_home=$(realpath "$HOME")

    if [ "$candidate" = "$canonical_home" ]; then
        warn "you cannot remove an install from '$HOME'; it's your home directory!"
        return 0
    fi

    ACTIVE_PATH="$(get_active_path)"
    if [ "$candidate" = "$ACTIVE_PATH" ]; then
        error "you cannot delete the active installation. Deactivate it first."
        return 1
    fi

    rm -Rf "$1"
}

list_print() {
    list_type=$1 # releases | builds | installations
    maybe_all=$2

    list=$KERL_BASE_DIR/otp_${list_type}
    if [ -f "$list" ]; then
        if [ "$(\wc -l "$list")" != '0' ]; then
            if [ "${list_type}" = releases ] && [ "$maybe_all" != all ]; then
                awk -v oldest_listed="$OLDEST_OTP_LISTED" \
                    -v oldest_supported="$OLDEST_OTP_SUPPORTED" \
                    -v include_rc="$KERL_INCLUDE_RELEASE_CANDIDATES" '
                function _print(vsn, is_this_supported) {
                    if (is_this_supported) {
                        suf=" *"
                    }
                    printf "%s%s\n", vsn, suf
                }
                {
                    this_version=$0
                    split(this_version, version_components, ".")
                    this_major=version_components[1]

                    if (last_major == "") {
                        last_major = oldest_supported - 1
                    }

                    is_this_r=/^R/
                    is_this_rc=/-rc/
                    is_rc_printable=(include_rc == "yes")
                    is_this_supported=(last_major >= oldest_supported)

                    if (!is_this_r) {
                        is_transition_to_rc=(is_last_not_rc && is_this_rc)
                        is_transition_from_rc=(!is_last_not_rc && !is_this_rc && is_rc_printable)
                        (is_transition_to_rc || is_transition_from_rc) \
                            && _print(last_version, is_this_supported)

                        last_version=this_version
                        last_major=this_major
                        is_last_not_rc=!is_this_rc
                    }
                }
                END {
                    last_version=$0
                    is_supported=1
                    (!is_this_rc || is_rc_printable) \
                        && _print(last_version, is_supported)
                }' "$list"
            else
                cat "$KERL_BASE_DIR/otp_$1"
            fi

            return 0
        fi
    fi
    notice "There are no $1 available."
}

list_add() {
    if [ -f "$KERL_BASE_DIR/otp_$1" ]; then
        while read -r l; do
            if [ "$l" = "$2" ]; then
                return 0
            fi
        done <"$KERL_BASE_DIR/otp_$1"
        if ! echo "$2" | tee -a "$KERL_BASE_DIR/otp_$1" >/dev/null 2>&1; then
            error "file $KERL_BASE_DIR/otp_$1 does not appear to be writable."
            return 1
        fi
    else
        if ! echo "$2" | tee "$KERL_BASE_DIR/otp_$1" >/dev/null 2>&1; then
            error "file $KERL_BASE_DIR/otp_$1 does not appear to be writable."
            return 1
        fi
    fi
}

list_remove() {
    if [ -f "$KERL_BASE_DIR/otp_$1" ]; then
        if ! sed "$SED_OPT" -i -e "/^.*$2$/d" "$KERL_BASE_DIR/otp_$1" 2>/dev/null; then
            error "file $KERL_BASE_DIR/otp_$1 does not appear writable."
            return 1
        fi
    fi
}

get_active_path() {
    if [ -n "$_KERL_ACTIVE_DIR" ]; then
        echo "$_KERL_ACTIVE_DIR"
    fi
}

fix_otp_installations() {
    if [ -f "$KERL_BASE_DIR"/otp_installations ]; then
        missing_paths=""
        while read -r l; do
            path=$(echo "$l" | cut -d' ' -f2)
            if [ ! -e "$path" ]; then
                missing_paths="$path $missing_paths"
            fi
        done <"$KERL_BASE_DIR"/otp_installations
        for missing_path in ${missing_paths}; do
            escaped="$(echo "$missing_path" | \sed "$SED_OPT" -e 's#/$##' -e 's#\/#\\\/#g')"
            list_remove installations "$escaped"
        done
    fi
}

fix_otp_builds() {
    if [ -f "$KERL_BASE_DIR"/otp_builds ]; then
        missing_keys=""
        while read -r l; do
            rel=$(echo "$l" | cut -d, -f1)
            name=$(echo "$l" | cut -d, -f2)
            if [ ! -e "${KERL_BUILD_DIR}/${name}" ]; then
                missing_keys="${rel},${name} $missing_keys"
            fi
        done <"$KERL_BASE_DIR"/otp_builds
        for missing_key in ${missing_keys}; do
            list_remove builds "${missing_key}"
        done
    fi
}

get_name_from_install_path() {
    if [ -f "$KERL_BASE_DIR"/otp_installations ]; then
        \grep -m1 -E "$1$" "$KERL_BASE_DIR"/otp_installations | cut -d' ' -f1
    fi
}

get_install_path_from_name() {
    if [ -f "$KERL_BASE_DIR"/otp_installations ]; then
        \grep -m1 -E "$1$" "$KERL_BASE_DIR"/otp_installations | cut -d' ' -f2
    fi
}

do_active() {
    ACTIVE_PATH="$(get_active_path)"
    if [ -n "$ACTIVE_PATH" ]; then
        notice "The current active installation is:"
        echo "$ACTIVE_PATH"
        return 0
    else
        error "no Erlang/OTP installation is currently active."
        return 1
    fi
}

download() {
    # $1: release

    if ! mkdir -p "$KERL_DOWNLOAD_DIR"; then
        error "couldn't create folder $KERL_DOWNLOAD_DIR."
        return 1
    fi
    if [ "$KERL_BUILD_BACKEND" = 'git' ]; then
        FILENAME="OTP-$1"
        if ! github_download "$1" "$FILENAME".tar.gz; then
            return 1
        fi
    else
        FILENAME="otp_src_$1"
        if ! tarball_download "$FILENAME".tar.gz; then
            return 1
        fi
    fi
}

github_download() {
    tarball_file="$KERL_DOWNLOAD_DIR/$2"
    tarball_url="$OTP_GITHUB_URL/archive/$2"
    prebuilt_url="$OTP_GITHUB_URL/releases/download/OTP-$1/otp_src_$1.tar.gz"
    http_code=$(_curl /dev/null "$prebuilt_url" "-I")
    if [ 200 = "$http_code" ]; then
        tarball_url=$prebuilt_url
        unset KERL_USE_AUTOCONF
    fi
    # if the file doesn't exist or the file has no size
    if [ ! -s "$tarball_file" ]; then
        notice "Downloading (from GitHub) Erlang/OTP $1 to $KERL_DOWNLOAD_DIR..."
        http_code=$(_curl "$tarball_file" "$tarball_url")
        if [ 200 != "$http_code" ]; then
            error "$tarball_url returned $http_code!"
            return 1
        fi
    else
        # If the downloaded tarball was corrupted due to interruption while
        # downloading.
        if ! gunzip -t "$tarball_file" 2>/dev/null; then
            notice "$tarball_file (from GitHub) corrupted; re-downloading..."
            rm -rf "$tarball_file"
            http_code=$(_curl "$tarball_file" "$tarball_url")
            if [ 200 != "$http_code" ]; then
                error "$tarball_url returned $http_code!"
                return 1
            fi
        fi
    fi
}

tarball_download() {
    if [ ! -s "$KERL_DOWNLOAD_DIR/$1" ]; then
        notice "Downloading tarball $1 to $KERL_DOWNLOAD_DIR..."
        http_code=$(_curl "$KERL_DOWNLOAD_DIR/$1" "$ERLANG_DOWNLOAD_URL/$1")
        if [ 200 != "$http_code" ]; then
            error "$ERLANG_DOWNLOAD_URL/$1 returned $http_code!"
            return 1
        fi
        if ! update_checksum_file; then
            return 1
        fi
    fi
    if ! ensure_checksum_file; then
        return 1
    fi
    notice "Tarball archive checksum being verified..."
    SUM="$($MD5SUM "$KERL_DOWNLOAD_DIR/$1" | cut -d' ' -f "$MD5SUM_FIELD")"
    ORIG_SUM="$(\grep -F "$1" "$KERL_DOWNLOAD_DIR"/MD5 | cut -d' ' -f2)"
    if [ "$SUM" != "$ORIG_SUM" ]; then
        error "checksum error; check file $1 in $KERL_DOWNLOAD_DIR."
        return 1
    fi
    success "Checksum verified: $SUM."
}

upgrade_kerl() {
    install_folder=$1
    http_code=$(_curl "$install_folder/kerl" "$KERL_GIT_BASE"/kerl)
    if [ 200 != "$http_code" ]; then
        error "$KERL_GIT_BASE/kerl returned $http_code!"
        return 1
    fi
    chmod +x "$install_folder/kerl"
    version=$(kerl version)
    current_kerl_path="$(command -v kerl)"
    notice "kerl $version is now available at $current_kerl_path."
}

fix_otp_builds
fix_otp_installations

case "$1" in
version)
    if [ $# -ne 1 ]; then
        usage_exit "version"
    fi

    tip "$KERL_VERSION"
    ;;
build)
    if [ "$2" = 'git' ]; then
        if [ $# -ne 5 ]; then
            usage_exit "build git <git_url> <git_version> <build_name>"
        fi

        do_git_build "$3" "$4" "$5"
    else
        if [ $# -lt 2 ] || [ $# -gt 3 ]; then
            usage_exit "build <release> [build_name]"
        fi

        if [ $# -eq 2 ]; then
            do_normal_build "$2" "$2"
        else
            do_normal_build "$2" "$3"
        fi
    fi
    ;;
build-install)
    # naming contains _or_ because do_build_install either accepts $2 as "git" or otherwise
    release_or_git="$2"
    build_name_or_git_url="$3"
    directory_or_git_version="$4"
    build_name="$5"
    directory="$6"

    if [ "$release_or_git" = "git" ]; then
        if [ $# -lt 5 ] || [ $# -gt 6 ]; then
            usage_exit "build-install git <git_url> <git_version> <build_name> [directory]"
        fi

        git_url="$build_name_or_git_url"
        git_version="$directory_or_git_version"
    else
        if [ $# -lt 2 ] || [ $# -gt 4 ]; then
            usage_exit "build-install <release> [build_name] [directory]"
        fi

        release="$release_or_git"
        build_name="$build_name_or_git_url"
        git_url="_unused_"
        directory="$directory_or_git_version"
        git_version="_unused_"
        if [ $# -eq 2 ]; then
            build_name="$release"
        fi
    fi
    if [ -z "$directory" ]; then
        if [ -z "$KERL_DEFAULT_INSTALL_DIR" ]; then
            directory="$PWD"
        else
            directory="$KERL_DEFAULT_INSTALL_DIR/$build_name"
        fi
    fi
    do_build_install "$release_or_git" "$git_url" "$git_version" "$build_name" "$directory"
    ;;
install)
    if [ $# -lt 2 ] || [ $# -gt 3 ]; then
        usage_exit "install <build_name> [directory]"
    fi

    if [ $# -eq 3 ]; then
        do_install "$2" "$3"
    else
        if [ -z "$KERL_DEFAULT_INSTALL_DIR" ]; then
            do_install "$2" "$PWD"
        else
            do_install "$2" "$KERL_DEFAULT_INSTALL_DIR/$2"
        fi
    fi
    ;;
deploy)
    if [ $# -lt 2 ] || [ $# -gt 4 ]; then
        usage_exit "deploy <[user@]host> [directory] [remote_directory]"
    fi

    if [ $# -eq 4 ]; then
        do_deploy "$2" "$3" "$4"
    elif [ $# -eq 3 ]; then
        do_deploy "$2" "$3"
    else
        do_deploy "$2" .
    fi
    ;;
update)
    if [ $# -ne 2 ] || [ "$2" != "releases" ]; then
        usage_exit "update releases"
    fi

    if ! check_releases force; then
        exit 1
    else
        notice "The available releases are:"
        list_print releases
    fi
    ;;
upgrade)
    if [ $# -ne 1 ]; then
        usage_exit "upgrade"
    fi

    current_kerl_path="$(command -v kerl)"
    which_status=$?
    if [ "$which_status" != 0 ]; then
        if [ -z ${KERL_APP_INSTALL_DIR+x} ]; then
            install_folder="$PWD"
        else
            install_folder="$KERL_APP_INSTALL_DIR"
        fi
        notice "kerl not installed. Dropping it into $install_folder/kerl..."
        upgrade_kerl "$install_folder"
    else
        version=$(kerl version)
        notice "Local kerl found ($current_kerl_path) at version $version."
        latest=$(_curl body_only "$KERL_GIT_BASE"/LATEST)
        notice "Remote kerl found at version $latest."
        if [ "$version" != "$latest" ]; then
            notice "Versions are different. Upgrading to $latest..."
            current_kerl_path=$(dirname "$current_kerl_path")
            if ! upgrade_kerl "$current_kerl_path"; then
                exit 1
            fi
        else
            success "No upgrade required."
        fi
        notice "Updating list of available releases... "
        kerl update releases >/dev/null
        notice "... done!"
    fi
    ;;
list)
    case "$2" in
    releases)
        if [ $# -lt 2 ] || [ $# -gt 3 ] || { [ $# -eq 3 ] && [ "$3" != 'all' ]; }; then
            usage_exit "list releases [all]"
        fi

        if ! check_releases; then
            exit 1
        fi
        list_print "$2" "$3"
        tip "Run '$0 update releases' to update this list."
        if [ $# -eq 2 ]; then
            tip "Run '$0 list releases all' to view all available releases."
            tip "Note: * means \"currently supported\"."
        fi
        ;;
    builds)
        if [ $# -ne 2 ]; then
            usage_exit "list builds"
        fi

        list_print "$2"
        ;;
    installations)
        if [ $# -ne 2 ]; then
            usage_exit "list installations"
        fi

        list_print "$2"
        ;;
    *)
        if [ -n "$2" ]; then
            error "cannot list (unknown) $2."
        fi
        usage_exit "list <releases|builds|installations> [all]"
        ;;
    esac
    ;;
path)
    if [ $# -lt 1 ] || [ $# -gt 2 ]; then
        usage_exit "path [installation]"
    fi

    # Usage:
    # kerl path
    # # Print currently active installation path, else non-zero exit
    # kerl path <install>
    # Print path to installation with name <install>, else non-zero exit
    if [ -z "$2" ]; then
        activepath=$(get_active_path)
        if [ -z "$activepath" ]; then
            warn "no active kerl-managed Erlang/OTP installation."
            exit 1
        fi
        tip "$activepath"
    else
        # There are some possible extensions to this we could
        # consider, such as:
        # - if 2+ matches: prefer one in a sub dir from $PWD
        # - prefer $KERL_DEFAULT_INSTALL_DIR
        match=
        for ins in $(list_print installations | cut -d' ' -f2); do
            if [ "$(basename "$ins")" = "$2" ]; then
                if [ -z "$match" ]; then
                    match="$ins"
                else
                    error "too many matching installations."
                    exit 1
                fi
            fi
        done
        if [ -n "$match" ]; then
            echo "$match"
        else
            error "no matching installation found."
            exit 1
        fi
    fi
    ;;
delete)
    case "$2" in
    build)
        if [ $# -ne 3 ]; then
            usage_exit "delete build [build_name]"
        fi

        rel="$(get_release_from_name "$3")"
        if [ -d "${KERL_BUILD_DIR:?}/$3" ]; then
            if ! maybe_remove "${KERL_BUILD_DIR:?}/$3"; then
                exit 1
            fi
        else
            if [ -z "$rel" ]; then
                error "no build named '$3'!"
                exit 1
            fi
        fi
        if ! list_remove "$2"s "$rel,$3"; then
            exit 1
        fi
        notice "Build '$3' has been deleted."
        ;;
    installation)
        if [ $# -ne 3 ]; then
            usage_exit "delete installation <build_name|directory>"
        fi

        if ! is_valid_installation "$3"; then
            error "'$3' is not a kerl-managed Erlang/OTP installation."
            exit 1
        fi
        if [ -d "$3" ]; then
            if ! maybe_remove "$3"; then
                exit 1
            fi
        else
            if ! maybe_remove "$(get_install_path_from_name "$3")"; then
                exit 1
            fi
        fi
        escaped="$(echo "$3" | \sed "$SED_OPT" -e 's#/$##' -e 's#\/#\\\/#g')"
        if ! list_remove "$2"s "$escaped"; then
            exit 1
        fi
        notice "Installation '$3' has been deleted."
        ;;
    *)
        if [ -n "$2" ]; then
            error "cannot delete $2."
        fi
        usage_exit "delete <build|installation> <build_name or directory>"
        ;;
    esac
    ;;
active)
    if [ $# -ne 1 ]; then
        usage_exit "active"
    fi

    if ! do_active; then
        exit 1
    fi
    ;;
plt)
    if [ $# -ne 1 ]; then
        usage_exit "plt"
    fi

    ACTIVE_PATH=$(get_active_path)
    if ! do_plt "$ACTIVE_PATH"; then
        exit 1
    fi
    ;;
status)
    if [ $# -ne 1 ]; then
        usage_exit "status"
    fi

    notice "Available builds:"
    list_print builds
    nocolor '----------'
    notice "Available installations:"
    list_print installations
    nocolor '----------'
    if ! do_active; then
        exit 1
    fi

    ACTIVE_PATH=$(get_active_path)
    do_plt "$ACTIVE_PATH"
    print_buildopts "$ACTIVE_PATH"
    ;;
prompt)
    if [ $# -ne 1 ]; then
        usage_exit "prompt"
    fi

    FMT=' (%s)'
    if [ -n "$2" ]; then
        FMT="$2"
    fi
    ACTIVE_PATH="$(get_active_path)"
    if [ -n "$ACTIVE_PATH" ]; then
        ACTIVE_NAME="$(get_name_from_install_path "$ACTIVE_PATH")"
        if [ -z "$ACTIVE_NAME" ]; then
            VALUE="$(basename "$ACTIVE_PATH")*"
        else
            VALUE="$ACTIVE_NAME"
        fi
        # shellcheck disable=SC2059  # Don't use variables in the printf format string. Use printf "..%s.." "$foo"
        printf "$FMT" "$VALUE"
    fi
    ;;
cleanup)
    if [ $# -ne 2 ]; then
        usage_exit "cleanup <build_name|all>"
    fi

    case "$2" in
    all)
        notice "Cleaning up compilation products for ALL builds under:"
        notice "  - $KERL_BUILD_DIR..."
        rm -rf "${KERL_BUILD_DIR:?}"/*
        notice "  - $KERL_DOWNLOAD_DIR..."
        rm -rf "${KERL_DOWNLOAD_DIR:?}"/*
        notice "  - $KERL_GIT_DIR..."
        rm -rf "${KERL_GIT_DIR:?}"/*
        notice "... done."
        ;;
    *)
        notice "Cleaning up compilation products for '$2' under:"
        notice "  - $KERL_BUILD_DIR..."
        rm -rf "${KERL_BUILD_DIR:?}/$2"
        rel=$(get_release_from_name "$2")
        if [ "${rel}" != "git" ]; then
            notice "  - $KERL_DOWNLOAD_DIR..."
            rm -f "${KERL_DOWNLOAD_DIR:?}"/OTP-"$2".tar.gz
            rm -f "${KERL_DOWNLOAD_DIR:?}"/otp_src_"$2".tar.gz
            rm -f "${KERL_DOWNLOAD_DIR:?}"/otp_doc_man_"$2".tar.gz
            rm -f "${KERL_DOWNLOAD_DIR:?}"/otp_doc_html_"$2".tar.gz
        fi
        notice "... done."
        ;;
    esac
    ;;
emit-activate)
    release=$2
    build_name=$3
    directory=$4
    shell=$5

    if [ $# -lt 4 ] || [ $# -gt 5 ] ||
        { [ $# -eq 5 ] && [ "$5" != "sh" ] && [ "$5" != "bash" ] && [ "$5" != "fish" ] && [ "$5" != "csh" ]; }; then
        usage_exit "emit-activate <release> <build_name> <directory> [sh|bash|fish|csh]"
    fi

    if [ -z "$5" ]; then
        shell="sh"
    elif [ "$shell" = "bash" ]; then
        shell="sh"
    fi

    case "$shell" in
    sh)
        emit_activate "$release" "$build_name" "$directory"
        ;;
    fish)
        emit_activate_fish "$release" "$build_name" "$directory"
        ;;
    csh)
        emit_activate_csh "$release" "$build_name" "$directory"
        ;;
    *) ;;
    esac
    ;;
*)
    error "unknown command '$1'."
    k_usage
    ;;
esac