#!/bin/sh
#
# Copyright (c) 2018, Julian Ospald <hasufell@posteo.de>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice,
#    this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 3. Neither the name of the <ORGANIZATION> nor the names of its
#    contributors may be used to endorse or promote products derived from
#    this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.





    ##########################
    #--[ Global Variables ]--#
    ##########################


# @VARIABLE: VERSION
# @DESCRIPTION:
# Version of this script.
VERSION=0.0.7

# @VARIABLE: SCRIPT
# @DESCRIPTION:
# Name of this script. This will be the
# shell name if this script is sourced, so
# only rely on this for echos and trivial things.
SCRIPT="$(basename "$0")"

# @VARIABLE: VERBOSE
# @DESCRIPTION:
# Whether to print verbose messages in this script.
VERBOSE=false

# @VARIABLE: FORCE
# @DESCRIPTION:
# Whether to force installation and overwrite files.
FORCE=false

# @VARIABLE: GHCUP_INSTALL_BASE_PREFIX
# @DESCRIPTION:
# The main install directory prefix, under which .ghcup
# directory will be created. This directory is user
# configurable via the environment variable of the
# same name. It must be non-empty and the path
# it points to must exist.
: "${GHCUP_INSTALL_BASE_PREFIX:=$HOME}"

# @VARIABLE: INSTALL_BASE
# @DESCRIPTION:
# The main install directory where all ghcup stuff happens.
INSTALL_BASE="$GHCUP_INSTALL_BASE_PREFIX/.ghcup"

# @VARIABLE: GHC_LOCATION
# @DESCRIPTION:
# The location where ghcup will install different ghc versions.
# This is expected to be a subdirectory of INSTALL_BASE.
GHC_LOCATION="$INSTALL_BASE/ghc"

# @VARIABLE: BIN_LOCATION
# @DESCRIPTION:
# The location where ghcup will create symlinks for GHC binaries.
# This is expected to be a subdirectory of INSTALL_BASE.
BIN_LOCATION="$INSTALL_BASE/bin"

# @VARIABLE: CACHE_LOCATION
# @DESCRIPTION:
# The location where ghcup will put tarballs for caching.
# This is expected to be a subdirectory of INSTALL_BASE.
CACHE_LOCATION="$INSTALL_BASE/cache"

# @VARIABLE: DOWNLOADER
# @DESCRIPTION:
# What program to use for downloading files.
DOWNLOADER="curl"

# @VARIABLE: DOWNLOADER_OPTS
# @DESCRIPTION:
# Options passed to the download program.
DOWNLOADER_OPTS="-L --fail -O"

# @VARIABLE: DOWNLOADER_STDOUT_OPTS
# @DESCRIPTION:
# Options passed to the download program when printing the content to stdout.
DOWNLOADER_STDOUT_OPTS="-L --fail"

# @VARIABLE: GHC_DOWNLOAD_BASEURL
# @DESCRIPTION:
# Base URL for all GHC tarballs.
GHC_DOWNLOAD_BASEURL="https://downloads.haskell.org/~ghc"

# @VARIABLE: JOBS
# @DESCRIPTION:
# How many jobs to use for compiling GHC.
JOBS="1"

# @VARIABLE: SOURCE
# @DESCRIPTION:
# The $0 argument, which contains
# the script name.
SOURCE="$0"

# @VARIABLE: BASE_DOWNLOAD_URL
# DESCRIPTION:
# The base url for downloading stuff like meta files, requirements files etc.
BASE_DOWNLOAD_URL="https://gitlab.haskell.org/haskell/ghcup/raw/master/"

# @VARIABLE: SCRIPT_UPDATE_URL
# @DESCRIPTION:
# Location to update this script from.
SCRIPT_UPDATE_URL="${BASE_DOWNLOAD_URL}/ghcup"

# @VARIABLE: META_DOWNLOAD_URL
# DESCRIPTION:
# The url of the meta file for getting
# download information for ghc/cabal-install etc.
META_DOWNLOAD_URL="${GHCUP_META_DOWNLOAD_URL:=${BASE_DOWNLOAD_URL}/.download-urls}"

# @VARIABLE: META_DOWNLOAD_FORMAT
# DESCRIPTION:
# The version of the meta file format.
# This determines whether this script can read the
# file from "${META_DOWNLOAD_URL}".
META_DOWNLOAD_FORMAT="1"

# @VARIABLE: META_VERSION_URL
# DESCRIPTION:
# The url of the meta file for getting
# available versions for ghc/cabal-install etc.
META_VERSION_URL="${GHCUP_META_VERSION_URL:=${BASE_DOWNLOAD_URL}/.available-versions}"

# @VARIABLE: META_VERSION_FORMAT
# DESCRIPTION:
# The version of the meta file format.
# This determines whether this script can read the
# file from "${META_VERSION_URL}".
META_VERSION_FORMAT="1"

# @VARIABLE: BUG_URL
# DESCRIPTION:
# The url to report bugs to.
BUG_URL="https://gitlab.haskell.org/haskell/ghcup/issues"

# @VARIABLE: CACHING
# @DESCRIPTION:
# Whether to cache tarballs in $CACHE_LOCATION.
CACHING=false



    ####################
    #--[ Print Help ]--#
    ####################


# @FUNCTION: usage
# @DESCRIPTION:
# Print the help message for 'ghcup' to STDERR
# and exit the script with status code 1.
usage() {
    (>&2 echo "ghcup ${VERSION}
GHC up toolchain installer

USAGE:
    ${SCRIPT} [FLAGS] <SUBCOMMAND>

FLAGS:
    -v, --verbose    Enable verbose output
    -h, --help       Prints help information
    -V, --version    Prints version information
    -w, --wget       Use wget instead of curl
    -c, --cache      Use \"${CACHE_LOCATION}\" for caching tarballs
                     (these will not be removed by ghcup)

SUBCOMMANDS:
    install            Install GHC$(${VERBOSE} && printf "\n    compile          Compile and install GHC from source (UNSTABLE!!!)")
    set                Set currently active GHC version
    list               Show available GHCs and other tools
    upgrade            Upgrade this script in-place
    rm                 Remove an already installed GHC
    install-cabal      Install cabal-install
    debug-info         Print debug info (e.g. detected system/distro)
    changelog          Show the changelog of a GHC release (online)
    print-system-reqs  Print an approximation of system requirements

DISCUSSION:
    ghcup installs the Glasgow Haskell Compiler from the official
    release channels, enabling you to easily switch between different
    versions.
")
    exit 1
}

# @FUNCTION: install_usage
# @DESCRIPTION:
# Print the help message for 'ghcup install' to STDERR
# and exit the script with status code 1.
install_usage() {
    (>&2 echo "ghcup-install
Install GHC from binary tarball

USAGE:
    ${SCRIPT} install [FLAGS] [VERSION|TAG]

FLAGS:
    -h, --help       Prints help information
    -f, --force      Overwrite already existing installation

ARGS:
    [VERSION|TAG]    E.g. \"8.4.3\" or \"8.6.1\" or
                     a tag like \"recommended\" or \"latest\"
                     (default: discovers recommended version)

DISCUSSION:
    Installs the specified GHC version (or a recommended default one) into
    a self-contained \"~/.ghcup/ghc/<ghcver>\" directory
    and symlinks the ghc binaries to \"~/.ghcup/bin/<binary>-<ghcver>\".
")
    exit 1
}

# @FUNCTION: set_usage
# @DESCRIPTION:
# Print the help message for 'ghcup set' to STDERR
# and exit the script with status code 1.
set_usage() {
    (>&2 echo "ghcup-set
Set the currently active GHC to the specified version

USAGE:
    ${SCRIPT} set [FLAGS] [VERSION|TAG]

FLAGS:
    -h, --help       Prints help information

ARGS:
    [VERSION|TAG]    E.g. \"8.4.3\" or \"8.6.3\" or
                     a tag like \"recommended\" or \"latest\"
                     (default: discovers recommended version)

DISCUSSION:
    Sets the the current GHC version by creating non-versioned
    symlinks for all ghc binaries of the specified version in
    \"~/.ghcup/bin/<binary>\".
")
    exit 1
}

# @FUNCTION: upgrade_usage
# @DESCRIPTION:
# Print the help message for 'ghcup upgrade' to STDERR
# and exit the script with status code 1.
upgrade_usage() {
    (>&2 echo "ghcup-upgrade
Update the ghcup script in-place

USAGE:
    ${SCRIPT} upgrade [FLAGS] [TARGET-LOCATION]

FLAGS:
    -i, --inplace      Update this script in-place (wherever it's at)
    -h, --help         Prints help information

ARGS:
    [TARGET-LOCATION]  Where to place the updated script (defaults to ${BIN_LOCATION}).
                       This is ignored if --inplace is issued as well.
")
    exit 1
}

# @FUNCTION: rm_usage
# @DESCRIPTION:
# Print the help message for 'ghcup rm' to STDERR
# and exit the script with status code 1.
rm_usage() {
    (>&2 echo "ghcup-rm
Remove the given GHC version installed by ghcup

USAGE:
    ${SCRIPT} rm [FLAGS] <VERSION>

FLAGS:
    -h, --help       Prints help information
    -f, --force      Don't prompt user

ARGS:
    <VERSION>        E.g. \"8.4.3\" or \"8.6.1\"
")
    exit 1
}

# @FUNCTION: install_cabal_usage
# @DESCRIPTION:
# Print the help message for 'ghcup install-cabal' to STDERR
# and exit the script with status code 1.
install_cabal_usage() {
    (>&2 echo "ghcup-install-cabal
Install the specified or a default cabal version

USAGE:
    ${SCRIPT} install-cabal [FLAGS] [VERSION|TAG]

FLAGS:
    -h, --help       Prints help information

ARGS:
    [VERSION|TAG]    E.g. \"2.4.0.0\" or a tag
                     like \"recommended\" or \"latest\"

DISCUSSION:
    Installs the specified cabal-install version (or the default recommended)
    into \"${BIN_LOCATION}\", so it can be overwritten
    by later \"cabal new-install cabal-install\", which installs into
    \"~/.cabal/bin\". Make sure to set up your PATH appropriately, so
    the cabal installation takes precedence.
")
    exit 1
}

# @FUNCTION: compile_usage
# @DESCRIPTION:
# Print the help message for 'ghcup compile' to STDERR
# and exit the script with status code 1.
compile_usage() {
    (>&2 echo "ghcup-compile
Compile and install the specified GHC version

USAGE:
    ${SCRIPT} compile [FLAGS] <VERSION> <BOOTSTRAP-GHC>

FLAGS:
    -h, --help                     Prints help information
    -f, --force                    Overwrite already existing installation
    -j, --jobs <n>                 How many jobs for compilation
    -c, --build-config <filepath>  Use the given config file as build config

ARGS:
    <VERSION>        E.g. \"8.4.3\" or \"8.6.1\"
    <BOOTSTRAP-GHC>  E.g. \"ghc-8.2.2\" or a full path

DISCUSSION:
    Compiles and installs the specified GHC version into
    a self-contained \"~/.ghcup/ghc/<ghcver>\" directory
    and symlinks the ghc binaries to \"~/.ghcup/bin/<binary>-<ghcver>\".

EXAMPLE:
    ghcup -v compile -f -j 4 8.4.2 ghc-8.2.2
")
    exit 1
}

# @FUNCTION: debug_info_usage
# @DESCRIPTION:
# Print the help message for 'ghcup debug-info' to STDERR
# and exit the script with status code 1.
debug_info_usage() {
    (>&2 echo "ghcup-debug-info
Print debug info (e.g. detected system/distro)

USAGE:
    ${SCRIPT} debug-info

FLAGS:
    -h, --help                     Prints help information

DISCUSSION:
    Prints debug information, e.g. detected system architecture,
    distribution, version, as well as script variables. This
    is mainly useful for debugging purposes.
")
    exit 1
}

# @FUNCTION: list_usage
# @DESCRIPTION:
# Print the help message for 'ghcup list' to STDERR
# and exit the script with status code 1.
list_usage() {
    (>&2 echo "ghcup-list
Show available GHCs and other tools

USAGE:
    ${SCRIPT} list

FLAGS:
    -h, --help                             Prints help information
    -t, --tool <all|ghc|cabal-install>     Tool to list versions for. Default is ghc only.
    -c, --show-criteria <installed|set>    Show only installed or set tool versions
    -r, --raw-format                       Raw format, for machine parsing

DISCUSSION:
    Prints tools (e.g. GHC and cabal-install) and their
    available/installed/set versions.
")
    exit 1
}

# @FUNCTION: changelog_usage
# @DESCRIPTION:
# Print the help message for 'ghcup changelog' to STDERR
# and exit the script with status code 1.
changelog_usage() {
    (>&2 echo "ghcup-changelog
View the online changelog for the given GHC version

USAGE:
    ${SCRIPT} changelog [FLAGS] [VERSION|TAG]

FLAGS:
    -h, --help       Prints help information

ARGS:
    [VERSION|TAG]    E.g. \"8.4.3\" or \"8.6.3\" or
                     a tag like \"recommended\" or \"latest\"
                     (default: discovers latest version)

DISCUSSION:
    Opens the online changelog for the given GHC version via
    xdg-open.
")
    exit 1
}

# @FUNCTION: print_system_reqs_usage
# @DESCRIPTION:
# Print the help message for 'ghcup print-system-reqs' to STDERR
# and exit the script with status code 1.
print_system_reqs_usage() {
    (>&2 echo "ghcup-print-system-reqs
Print an approximation of system requirements

USAGE:
    ${SCRIPT} print-system-reqs

FLAGS:
    -h, --help       Prints help information

DISCUSSION:
    Just prints an approximation of the system requirements
    for the 'recommended' GHC version and the 'latest' distro version
    you are on.

    Review this output carefully!
")
    exit 1
}




    ###########################
    #--[ Utility functions ]--#
    ###########################


# @FUNCTION: die
# @USAGE: [msg]
# @DESCRIPTION:
# Exits the shell script with status code 2
# and prints the given message in red to STDERR, if any.
die() {
    (>&2 red_message "$1")
    exit 2
}

# @FUNCTION: edo
# @USAGE: <command>
# @DESCRIPTION:
# Executes the given command. Also prints what
# command that is (in blue) if verbosity is enabled.
# Exits with status code 2 if the command failed.
edo()
{
    if ${VERBOSE} ; then
        printf "\\033[0;34m%s\\033[0m\\n" "$*" 1>&2
    fi
    "$@" || exit 2
}

# @FUNCTION: emake
# @USAGE: [arguments]
# @DESCRIPTION:
# Wrapper around 'make', may call 'gmake' if it exists.
emake() { # avoid re-checking for gmake
    if [ -n "${MAKE}" ] ; then
        # shellcheck disable=SC2086
        edo ${MAKE} "$@"
    else
        if command_exists gmake ; then
            MAKE="gmake"
            # shellcheck disable=SC2086
            edo ${MAKE} "$@"
        else
            MAKE="make"
            # shellcheck disable=SC2086
            edo ${MAKE} "$@"
        fi
    fi
}

# @FUNCTION: debug_message
# @USAGE: <msg>
# @DESCRIPTION:
# Print a blue debug message if verbosity is enabled.
debug_message() {
    if ${VERBOSE} ; then
        (>&2 printf "\\033[0;34m%s\\033[0m\\n" "$1")
    fi
}

# @FUNCTION: optionv
# @USAGE: <arg1> [arg2]
# @DESCRIPTION:
# If verbosity is enabled, echo the first argument, otherwise
# the second (if any).
# @STDOUT: first or second argument
optionv() {
    if ${VERBOSE} ; then
        echo "$1"
    else
        if [ -n "$2" ] ; then
            echo "$2"
        fi
    fi
}

# @FUNCTION: status_message
# @USAGE: <msg>
# @DESCRIPTION:
# Print a green status message.
status_message() {
    printf "\\033[0;32m%s\\033[0m\\n" "$1"
}

# @FUNCTION: warning_message
# @USAGE: <msg>
# @DESCRIPTION:
# Print a yellow warning message.
warning_message() {
    printf "\\033[1;33m%s\\033[0m\\n" "$1"
}

# @FUNCTION: red_message
# @USAGE: <msg>
# @DESCRIPTION:
# Print a red message.
red_message() {
    printf "\\033[0;31m%s\\033[0m\\n" "$1"
}

# @FUNCTION: command_exists
# @USAGE: <command>
# @DESCRIPTION:
# Check if a command exists (no arguments).
# @RETURNS: 0 if the command exists, non-zero otherwise
command_exists() {
    [ -z "$1" ] && die "Internal error: no argument given to command_exists"

    command -V "$1" >/dev/null 2>&1
    return $?
}

# @FUNCTION: check_required_commands
# @USAGE: [additional-commands]
# @DESCRIPTION:
# Check that all required commands for this script exist.
# @STDOUT: The commands that do not exist
# @RETURNS: 0 if all command exists, non-zero otherwise
check_required_commands() {
    _missing_commands=
    mydistro=$(get_distro_alias "$(get_distro_name)")

    for com in "$@" awk uname basename tar gzip mktemp dirname ; do
        command_exists "${com}" || {
            _missing_commands="${_missing_commands} ${com}"
        }
    done
    unset com

    # darwin uses tar's built-in xz decompression
    if test "${mydistro}" != "darwin"; then
        command_exists xz || {
            _missing_commands="${_missing_commands} xz"
        }
    fi

    if [ -n "${_missing_commands}" ] ; then
        printf "%s" "${_missing_commands}"
        unset _missing_commands mydistro
        return 1
    else
        unset _missing_commands mydistro
        return 0
    fi
}

# @FUNCTION: get_distro_name
# @DESCRIPTION:
# Gets the current distro identifier following
# https://unix.stackexchange.com/a/6348
# (see also http://linuxmafia.com/faq/Admin/release-files.html)
# @STDOUT: current distro identifier
get_distro_name() {
    if [ -f /etc/os-release ]; then
        # freedesktop.org and systemd
        # shellcheck disable=SC1091
        . /etc/os-release
        printf "%s" "$NAME"
    elif command_exists lsb_release ; then
        # linuxbase.org
        printf "%s" "$(lsb_release -si)"
    elif [ -f /etc/lsb-release ]; then
        # For some versions of Debian/Ubuntu without lsb_release command
        # shellcheck disable=SC1091
        . /etc/lsb-release
        printf "%s" "$DISTRIB_ID"
    elif [ -f /etc/redhat-release ]; then
        case "$(cat /etc/redhat-release)" in
        # Older CentOS releases didn't have a /etc/centos-release file
        "CentOS release "*)
            printf "CentOS"
            ;;
        "CentOS Linux release "*)
            printf "CentOS Linux"
            ;;
        "Fedora release "*)
            printf "Fedora"
            ;;
        # Fallback to uname
        *)
            printf "%s" "$(uname -s)"
            ;;
        esac
    elif [ -f /etc/debian_version ]; then
        # Older Debian/Ubuntu/etc.
        printf "Debian"
    else
        # Fall back to uname, e.g. "Linux <version>", also works for BSD, etc.
        printf "%s" "$(uname -s)"
    fi
}

# @FUNCTION: get_distro_ver
# @DESCRIPTION:
# Gets the current distro version (if any) following
# https://unix.stackexchange.com/a/6348
# @STDOUT: current distro version, if any
get_distro_ver() {
    if [ -f /etc/os-release ]; then
        # freedesktop.org and systemd
        # shellcheck disable=SC1091
        . /etc/os-release
        printf "%s" "$VERSION_ID"
    elif command_exists lsb_release ; then
        # linuxbase.org
        printf "%s" "$(lsb_release -sr)"
    elif [ -f /etc/lsb-release ]; then
        # For some versions of Debian/Ubuntu without lsb_release command
        # shellcheck disable=SC1091
        . /etc/lsb-release
        printf "%s" "$DISTRIB_RELEASE"
    elif [ -f /etc/redhat-release ]; then
        case "$(cat /etc/redhat-release)" in
        # NB: Older CentOS releases didn't have a /etc/centos-release file
        "CentOS release "*|"Fedora release "*)
            printf "%s" "$(awk 'NR==1 { split($3, a, "."); print a[1] }' /etc/redhat-release)"
            ;;
        "CentOS Linux release "*)
            printf "%s" "$(awk 'NR==1 { split($4, a, "."); print a[1] }' /etc/redhat-release)"
            ;;
        # Fallback to uname
        *)
            printf "%s" "$(uname -r)"
            ;;
        esac
    elif [ -f /etc/debian_version ]; then
        # Older Debian/Ubuntu/etc.
        printf "%s" "$(cat /etc/debian_version)"
    else
        case "$(uname -s)" in
        AIX)
            printf "%s" "$(uname -v)"
            ;;
        FreeBSD)
            # we only care about the major numeric version part left of
            # the '.' in "11.2-RELEASE".
            printf "%s" "$(uname -r | cut -d . -f 1)"
            ;;
        *)
            # Fall back to uname, e.g. "Linux <version>", also works for BSD, etc.
            printf "%s" "$(uname -r)"
        esac
    fi
}

# @FUNCTION: get_arch
# @DESCRIPTION:
# Gets the architecture following
# https://unix.stackexchange.com/a/6348
# Fails for any architecture that we don't know a GHC version for.
# @STDOUT: current architecture
get_arch() {
    myarch=$(uname -m)

    case "${myarch}" in
    x86_64|amd64)
        printf "x86_64"  # or AMD64 or Intel64 or whatever
        ;;
    i*86)
        printf "i386"  # or IA32 or Intel32 or whatever
        ;;
    *)
        case "$(uname -s)" in
        AIX)
            case "$(uname -p)" in
            powerpc)
                printf "powerpc"
                ;;
            *)
                die "Cannot figure out architecture on AIX (was: ${myarch})"
                ;;
            esac
            ;;
        *)
            die "Cannot figure out architecture (was: ${myarch})"
            ;;
        esac
    esac

    unset myarch
}

# @FUNCTION: try_download_url
# @USAGE: <tool> <ver> <arch> <distro-ident> <file>
# @DESCRIPTION:
# Tries to get the download url of a tool with our
# specified format for download urls (see ${META_DOWNLOAD_URL}").
# STDOUT: the download url, if an appropriate was found
try_download_url() {
    [ "$#" -lt 5 ] && die "Internal error: not enough arguments to try_download_url"

    tool=$1
    ver=$2
    arch=$3
    distro_ident=$4
    filename=$5

    awk "
    NF {
        split(\$4,a,\",\")
        if (\$1 == \"${tool}\" && \$2 == \"${ver}\" && \$3 == \"${arch}\") {
            for (i in a) if (a[i] == \"${distro_ident}\") {
                print \$5
                exit
            }
        }
    }" "${filename}" || die "awk failed!"

    unset tool ver arch distro_ident filename
}

# @FUNCTION: check_meta_file_version
# @USAGE: <file> <metaver>
# @DESCRIPTION:
# Check that the given meta file has the same format version
# as specified, otherwise die.
check_meta_file_version() {
    { [ -z "$1" ] || [ -z "$2" ] ;} && die "Internal error: not enough arguments given to check_meta_file_version"

    mymetavar=$(awk "
    NR==1 {
        if (\$2 ~ \"fmt-version\") {
            {
                split(\$2,a,\"=\")
                print a[2]
                exit
            }
        }
    }" "$1")

    if [ "${mymetavar}" != "$2" ] ; then
        die "Unsupported meta file format, run: ${SCRIPT} upgrade"
    fi

    unset mymetavar
}

# @FUNCTION: get_download_url
# @USAGE: <tool> <version>
# @DESCRIPTION:
# Gets the download url for the given tool and version
# and the current distro and architecture (which it tries to discover).
# This uses "${META_DOWNLOAD_URL}" for url discovery.
# @STDOUT: download url or nothing if no appropriate was found
get_download_url() {
    { [ -z "$1" ] || [ -z "$2" ] ;} && die "Internal error: not enough arguments given to get_download_url"

    mytool=$1
    myver=$2
    myarch=$(get_arch)
    [ -z "${myarch}" ] && die "failed to get architecture"
    mydistro=$(get_distro_alias "$(get_distro_name)")
    mydistrover=$(get_distro_ver)
    meta_file="$(get_meta_download_file)"
    [ -z "${meta_file}" ] && die "failed to get meta file"


    # 1st try with full distro=ver
    url=$(try_download_url "${mytool}" "${myver}" "${myarch}" "${mydistro}=${mydistrover}" "${meta_file}")
    if [ -n "${url}" ] ; then
        printf "%s" "${url}"
        exit 0
    fi

    # 2nd try with just distro
    url=$(try_download_url "${mytool}" "${myver}" "${myarch}" "${mydistro}" "${meta_file}")
    if [ -n "${url}" ] ; then
        printf "%s" "${url}"
        exit 0
    fi

    # 3rd try with unknown
    url=$(try_download_url "${mytool}" "${myver}" "${myarch}" "unknown" "${meta_file}")
    if [ -n "${url}" ] ; then
        printf "%s" "${url}"
        exit 0
    fi

    unset mytool myver myarch mydistro mydistrover meta_file
}

# @FUNCTION: get_tool_ver_from_tag
# @USAGE: <tool> <tag>
# @DESCRIPTION:
# Gets the tool version with the given tag (first match) from
# "${META_VERSION_URL}".
# STDOUT: the version, if any, or nothing
get_tool_ver_from_tag() {
    { [ -z "$1" ] || [ -z "$2" ] ;} && die "Internal error: not enough arguments given to get_tool_ver_from_tag"

    mytool=$1
    mytag=$2

    meta_file="$(get_meta_version_file)"
    [ -z "${meta_file}" ] && die "failed to get meta file"

    awk "
    NF {
        if (\$1 == \"${mytool}\") {
            split(\$3,a,\",\");
            for (i in a) if (a[i] == \"${mytag}\") {
                print \$2
                exit
            }
        }
    }" "${meta_file}" || die "awk failed!"

    unset mytool mytag meta_file
}

# @FUNCTION: ghc_already_installed
# @USAGE: <ghcversion>
# @DESCRIPTION:
# Checks whether the specified GHC version
# has been installed by ghcup already.
# @RETURN: 0 if GHC is already installed, 1 otherwise
ghc_already_installed() {
    [ -z "$1" ] && die "Internal error: no argument given to ghc_already_installed"

    if [ -e "$(get_ghc_location "$1")" ] ; then
        return 0
    else
        return 1
    fi
}

# @FUNCTION: cabal_already_installed
# @USAGE: <cabalversion>
# @DESCRIPTION:
# Checks whether the specified cabal version
# has been installed by ghcup already.
# @RETURN: 0 if cabal is already installed, 1 otherwise
cabal_already_installed() {
    [ -z "$1" ] && die "Internal error: no argument given to cabal_already_installed"

    if [ -x "${BIN_LOCATION}/cabal" ] ; then
        if [ "$("${BIN_LOCATION}/cabal" --numeric-version)" = "$1" ] ; then
            return 0
        else
            return 1
        fi
    else
        return 1
    fi
}

# @FUNCTION: tool_already_installed
# @USAGE: <tool> <cabalversion>
# @DESCRIPTION:
# Checks whether the specified tool and version
# has been installed by ghcup already.
# @RETURN: 0 if tool is already installed, 1 otherwise
tool_already_installed() {
    if [ "$1" = "ghc" ] ; then
        ghc_already_installed "$2"
        return $?
    elif [ "$1" = "cabal-install" ] ; then
        cabal_already_installed "$2"
        return $?
    else
        return 1
    fi
}


# @FUNCTION: get_ghc_location
# @USAGE: <ghcversion>
# @DESCRIPTION:
# Gets/prints the location where the specified GHC is or would be installed.
# Doesn't check whether that directory actually exist. Use
# 'ghc_already_installed' for that.
# @STDOUT: ghc location
get_ghc_location() {
    [ -z "$1" ] && die "Internal error: no argument given to get_ghc_location"

    myghcver=$1
    inst_location=${GHC_LOCATION}/${myghcver}

    printf "%s" "${inst_location}"

    unset myghcver inst_location
}

# @FUNCTION: download
# @USAGE: <url>
# @DESCRIPTION:
# Downloads the given url as a file into the current directory.
download() {
    [ -z "$1" ] && die "Internal error: no argument given to download"
    # shellcheck disable=SC2086
    edo ${DOWNLOADER} ${DOWNLOADER_OPTS} "$1"
}

# @FUNCTION: download_to_cache
# @USAGE: <url>
# @DESCRIPTION:
# Downloads the given url as a file into the cache directory
# and makes sure the file is deleted on failed/interrupted download.
download_to_cache() {
    [ -z "$1" ] && die "Internal error: no argument given to download_to_cache"

    _dtc_download_url="$1"
    _dtc_download_tarball_name=$(basename "${_dtc_download_url}")

    rm_tarball() {
        if [ -e "${CACHE_LOCATION}/${_dtc_download_tarball_name}" ] ; then
            rm "${CACHE_LOCATION}/${_dtc_download_tarball_name}"
        fi
    }

    (
        trap 'rm_tarball' 2
        edo cd "${CACHE_LOCATION}"
        # shellcheck disable=SC2086
        edo ${DOWNLOADER} ${DOWNLOADER_OPTS} "${_dtc_download_url}"
        trap - 2
    ) || {
        rm_tarball
        die "Failed to download"
    }

    unset _dtc_download_tarball_name _dtc_download_url
}

# @FUNCTION: download_silent
# @USAGE: <url>
# @DESCRIPTION:
# Downloads the given url as a file into the current directory, silent, unless
# verbosity is on.
download_silent() {
    [ -z "$1" ] && die "Internal error: no argument given to download"

    if ${VERBOSE} ; then
        # shellcheck disable=SC2086
        edo ${DOWNLOADER} ${DOWNLOADER_OPTS} "$1"
    else
        # shellcheck disable=SC2086
        edo ${DOWNLOADER} ${DOWNLOADER_OPTS} "$1" 1> /dev/null 2> /dev/null
    fi
}

# @FUNCTION: download_to_stdout
# @USAGE: <url>
# @DESCRIPTION:
# Downloads the given url to stdout.
download_to_stdout() {
    [ -z "$1" ] && die "Internal error: no argument given to download"
    # shellcheck disable=SC2086
    edo ${DOWNLOADER} ${DOWNLOADER_STDOUT_OPTS} "$1" 2> /dev/null
}

# @FUNCTION: unpack
# @USAGE: <tarball>
# @DESCRIPTION:
# Uncompresses and unpacks the given tarball if needed by discovering the
# file extension.
unpack() {
    [ -z "$1" ] && die "Internal error: no argument given to unpack"

    mydistro=$(get_distro_alias "$(get_distro_name)")
    filename=$1
    file_ext=${filename##*.}

    # this is for portability, since not all
    # distros have tar with compression detection
    # capability
    case "${file_ext}" in
        xz)
            if test "${mydistro}" = "darwin"; then
              debug_message "tar xf \"${filename}\""
              ( tar xf "${filename}" ) || die "unpacking failed!"
            else
              debug_message "xz -cd \"${filename}\" | tar -xf -"
              ( xz -cd "${filename}" | tar xf - ; ) || die "unpacking failed!"
            fi
            ;;
        gz)
            debug_message "gzip -cd \"${filename}\" | tar -xf -"
            ( gzip -cd "${filename}" | tar xf - ; ) || die "unpacking failed!"
            ;;
        tar)
            edo tar xf "${filename}"
            ;;
        *)
            die "Unknown file extension: \"${file_ext}\""
    esac

    unset mydistro filename file_ext
}

# @FUNCTION: ask_for_confirmation
# @USAGE: [confirmation-msg]
# @DESCRIPTION:
# Asks the user for confirmation and returns 0 for yes, 1 for no.
# @RETURN: 0 if user confirmed, 1 otherwise
ask_for_confirmation() {
    confirmation_msg=$1

    if [ -n "${confirmation_msg}" ] ; then
        printf "%s\\n(y/n and press Enter)\\n" "${confirmation_msg}"
    else
        printf "Confirm action: (y/n and press Enter)\\n"
    fi
    read -r answer

    if [ "${answer}" != "${answer#[Yy]}" ] ;then
        return 0
    else
        return 1
    fi

    unset confirmation_msg answer
}

# @FUNCTION: get_distro_alias
# @USAGE: <distro name>
# @DESCRIPTION:
# For a given known distro name, return our internal
# unique distro alias. E.g.:
#   Debian GNU/Linux -> debian
# STDOUT: our internal distro alias
get_distro_alias() {
    distro_name=$1
    distro_alias=unknown

    case "${distro_name}" in
        "Debian"|"Debian GNU/Linux"|"debian")
            distro_alias=debian
            ;;
        "Ubuntu"|"ubuntu")
            distro_alias=ubuntu
            ;;
        "Exherbo"|"exherbo")
            distro_alias=exherbo
            ;;
        "Fedora"|"fedora")
            distro_alias=fedora
            ;;
        "CentOS Linux"|"CentOS"|"centos"|"Red Hat Enterprise Linux"*)
            distro_alias=centos
            ;;
        "Alpine Linux"|"Alpine")
            distro_alias=alpine
            ;;
        "Linux Mint"|"LinuxMint")
            distro_alias=mint
            ;;
        "Amazon Linux AMI")
            distro_alias=amazonlinux
            ;;
        "AIX")
            distro_alias=aix
            ;;
        "FreeBSD")
            distro_alias=freebsd
            ;;
        "Darwin")
            distro_alias=darwin
            ;;
    esac

    printf "%s" "${distro_alias}"

    unset distro_name distro_alias
}

# @FUNCTION: posix_realpath
# @USAGE: <file>
# @DESCRIPTION:
# Portably gets the realpath and prints it to stdout.
# This was initially inspired by
#   https://gist.github.com/tvlooy/cbfbdb111a4ebad8b93e
#   and
#   https://stackoverflow.com/a/246128
#
# If the file does not exist, just prints it appended to the current directory.
# @STDOUT: realpath of the given file
posix_realpath() {
    [ -z "$1" ] && die "Internal error: no argument given to posix_realpath"
    current_loop=0
    max_loops=50
    mysource=$1

    while [ -h "${mysource}" ]; do
        current_loop=$((current_loop+1))
        mydir="$( cd -P "$( dirname "${mysource}" )" > /dev/null 2>&1 && pwd )"
        mysource="$(readlink "${mysource}")"
        [ "${mysource%${mysource#?}}"x != '/x' ] && mysource="${mydir}/${mysource}"

        if [ ${current_loop} -gt ${max_loops} ] ; then
            (>&2 echo "${1}: Too many levels of symbolic links")
            break
        fi
    done
    mydir="$( cd -P "$( dirname "${mysource}" )" > /dev/null 2>&1 && pwd )"

    # TODO: better distinguish between "does not exist" and "permission denied"
    if [ -z "${mydir}" ] ; then
        (>&2 echo "${1}: Permission denied")
    else
        echo "${mydir%/}/$(basename "${mysource}")"
    fi

    unset current_loop max_loops mysource mydir
}


# @FUNCTION: get_meta_version_file
# @DESCRIPTION:
# Downloads the META_VERSION_URL
# in case it hasn't been downloaded
# during the execution of this script yet
# and checks the format version matches
# the expected one.
# @STDOUT: file location
get_meta_version_file() {
    meta_file_name="$(basename "${META_VERSION_URL}")"
    meta_filepath="${CACHE_LOCATION}/${meta_file_name}"

    if [ ! -e "${meta_filepath}" ] ; then
        (
            edo cd "${CACHE_LOCATION}"
            download_silent "${META_VERSION_URL}"
        ) || die "downloading failed"
    fi

    check_meta_file_version "${meta_filepath}" "${META_VERSION_FORMAT}"

    printf "%s" "${meta_filepath}"

    unset meta_file_name meta_filepath
}


# @FUNCTION: get_meta_download_file
# @DESCRIPTION:
# Downloads the META_DOWNLOAD_URL
# in case it hasn't been downloaded
# during the execution of this script yet
# and checks the format version matches
# the expected one.
# @STDOUT: file location
get_meta_download_file() {
    meta_file_name="$(basename "${META_DOWNLOAD_URL}")"
    meta_filepath="${CACHE_LOCATION}/${meta_file_name}"

    if [ ! -e "${meta_filepath}" ] ; then
        (
            edo cd "${CACHE_LOCATION}"
            download_silent "${META_DOWNLOAD_URL}"
        ) || die "downloading failed!"
    fi

    check_meta_file_version "${meta_filepath}" "${META_DOWNLOAD_FORMAT}"

    printf "%s" "${CACHE_LOCATION}/${meta_file_name}"

    unset meta_file_name meta_filepath
}

# @FUNCTION: known_tool_versions
# @USAGE: <tool>
# @DESCRIPTION:
# Prints the known tool versions from
# META_VERSION_URL.
# @STDOUT: known ghc versions
known_tool_versions() {
    [ -z "$1" ] && die "Internal error: no argument given to posix_realpath"

    mytool=$1
    meta_file="$(get_meta_version_file)"
    [ -z "${meta_file}" ] && die "failed to get meta file"

    awk "
    NF {
        if (\$1 == \"${mytool}\") {
            print \$2
        }
    }" "${meta_file}" || die "awk failed!"

    unset mytool meta_file
}


# @FUNCTION: known_tool_tags
# @USAGE: <tool>
# @DESCRIPTION:
# Prints the known tool tags from
# META_VERSION_URL.
# @STDOUT: known tool tags
known_tool_tags() {
    [ -z "$1" ] && die "Internal error: no argument given to known_tool_tags"

    mytool=$1
    meta_file="$(get_meta_version_file)"
    [ -z "${meta_file}" ] && die "failed to get meta file"

    awk "
    NF {
        if (\$1 == \"${mytool}\") {
            split(\$3,a,\",\");
            for (i in a) {
                print a[i]
            }
        }
    }" "${meta_file}" | sort -u || die "awk failed!"

    unset mytool meta_file
}

# @FUNCTION: array_contains
# @USAGE: <element> <array>
# @DESCRIPTION:
# Checks whether the given elements
# is in the array.
# @RETURNS: returns 0 if the element is in the array, 1 otherwise
array_contains() {
    { [ -z "$1" ] || [ -z "$2" ] ;} && die "Internal error: not enough arguments given to array_contains"

    element=$1
    array=$2

    for e in ${array} ; do
        if [ "${e}" = "${element}" ] ; then
            unset e element array
            return 0
        fi
    done

    unset e element array
    return 1
}

# @FUNCTION: show_ghc_installed
# @DESCRIPTION:
# Prints the currently selected GHC only as version string.
# @STDOUT: current GHC version
show_ghc_installed() {
    current_ghc="${BIN_LOCATION}/ghc"
    real_ghc=$(posix_realpath "${current_ghc}")

    if [ -L "${current_ghc}" ] ; then # is symlink
        if [ -e "${real_ghc}" ] ; then # exists (posix_realpath was called)
            real_ghc="$(basename "${real_ghc}" | sed 's#ghc-##')"
            printf "%s" "${real_ghc}"
        else # is a broken symlink
            red_message "broken symlink"
        fi
    fi

    unset real_ghc current_ghc
}

# @FUNCTION: show_cabal_installed
# @DESCRIPTION:
# Prints the currently selected cabal only as version string.
# @STDOUT: current cabal version
show_cabal_installed() {
    if [ -x "${BIN_LOCATION}/cabal" ] ; then
        "${BIN_LOCATION}/cabal" --numeric-version
    fi
}


# @FUNCTION: get_full_ghc_ver
# @USAGE: <ghcmajorversion>
# @DESCRIPTION:
# Get the latest full GHC version .
get_full_ghc_ver() {
    [ -z "$1" ] && die "Internal error: no argument given to get_full_ghc_ver"

    mymajorghcver=$1
    latest_ghc=0

    for current_ghc in "${BIN_LOCATION}/ghc-${mymajorghcver}."* ; do
        [ -e "${current_ghc}" ] || break
        real_ghc=$(posix_realpath "${current_ghc}")
        real_ghc="$(basename "${real_ghc}" | sed 's#ghc-##')"
        if [ "$(expr "${real_ghc}" \> "${latest_ghc}")" = 1 ] ; then
            latest_ghc=${real_ghc}
        fi
    done

    if [ "${latest_ghc}" != 0 ] ; then
        printf "%s" "${latest_ghc}"
    fi

    unset mymajorghcver latest_ghc real_ghc current_ghc
}

# @FUNCTION: set_ghc_major
# @USAGE: <ghcversion>
# @DESCRIPTION:
# Sets a ghc-x.y major version to the latest ghc-x.y.z if any is installed.
set_ghc_major() {
    [ -z "$1" ] && die "Internal error: no argument given to set_ghc_major"

    full_ghc_ver="$(get_full_ghc_ver "${1%.*}")"

    if [ -z "${full_ghc_ver}" ] ; then
        die "Could not set GHC major symlink"
    fi
    set_ghc "${full_ghc_ver}" "-${1%.*}"

    unset full_ghc_ver
}




    ############################
    #--[ Subcommand install ]--#
    ############################


# @FUNCTION: install_ghc
# @USAGE: <ghcversion>
# @DESCRIPTION:
# Installs the given ghc version with a lot of side effects.
install_ghc() {
    [ -z "$1" ] && die "Internal error: no argument given to install_ghc"

    myghcver=$1
    inst_location=$(get_ghc_location "$1")
    [ -z "${inst_location}" ] && die "failed to get install location"
    download_url=$(get_download_url "ghc" "${myghcver}")
    if [ -z "${download_url}" ] ; then
        die "Could not find an appropriate download for the requested GHC-${myghcver} on your system! Please report a bug at ${BUG_URL}"
    fi
    download_tarball_name=$(basename "${download_url}")
    first_install=true


    status_message "Installing GHC-${myghcver} for $(get_distro_name) on architecture $(get_arch)"

    if ghc_already_installed "${myghcver}" ; then
        if ${FORCE} ; then
            echo "GHC already installed in ${inst_location}, overwriting!"
        else
            warning_message "GHC already installed in ${inst_location}, use --force to overwrite"
            exit 0
        fi
        first_install=false
    fi

    tmp_dir=$(mktemp -d -t ghcup.XXXXXXXX)
    [ -z "${tmp_dir}" ] && die "Failed to create temporary directory"
    (
        if ${CACHING} ; then
            if [ ! -e "${CACHE_LOCATION}/${download_tarball_name}" ] ; then
                download_to_cache "${download_url}"
            fi
            edo cd "${tmp_dir}"
            unpack "${CACHE_LOCATION}/${download_tarball_name}"
        else
            edo cd "${tmp_dir}"
            download "${download_url}"
            unpack "${download_tarball_name}"
        fi

        edo cd "./ghc-${myghcver}"

        debug_message "Installing GHC into ${inst_location}"

        edo ./configure --prefix="${inst_location}"
        emake install

        # clean up
        edo cd ..
        [ -e "${tmp_dir}/${download_tarball_name}" ] && rm "${tmp_dir}/${download_tarball_name}"
        [ -e "${tmp_dir}/ghc-${myghcver}" ] && rm -r "${tmp_dir}/ghc-${myghcver}"
    ) || {
        [ -e "${tmp_dir}/${download_tarball_name}" ] && rm "${tmp_dir}/${download_tarball_name}"
        [ -e "${tmp_dir}/ghc-${myghcver}" ] && rm -r "${tmp_dir}/ghc-${myghcver}"

        if ${first_install} ; then
            [ -e "${inst_location}" ] && rm -r "${inst_location}"
        else
            warning_message "GHC force installation failed. The install might be broken."
            warning_message "Consider running: ghcup rm ${myghcver}"
        fi

        die "Failed to install, consider updating this script via: ${SCRIPT} upgrade"
    }

    for f in "${inst_location}"/bin/*-"${myghcver}" ; do
        [ -e "${f}" ] || die "Something went wrong, ${f} does not exist!"
        fn=$(basename "${f}")
        # shellcheck disable=SC2046
        edo ln $(optionv "-v") -sf ../ghc/"${myghcver}/bin/${fn}" "${BIN_LOCATION}/${fn}"
        unset fn
    done
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/runhaskell "${BIN_LOCATION}/runhaskell-${myghcver}"
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/hsc2hs "${BIN_LOCATION}/hsc2hs-${myghcver}"
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/hp2ps "${BIN_LOCATION}/hp2ps-${myghcver}"
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/hpc "${BIN_LOCATION}/hpc-${myghcver}"
    if [ -e "${inst_location}/bin/haddock" ] ; then
        # shellcheck disable=SC2046
        edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/haddock "${BIN_LOCATION}/haddock-${myghcver}"
    fi

    status_message "Done installing, run \"ghci-${myghcver}\" or set up your current GHC via: ${SCRIPT} set ${myghcver}"

    unset inst_location f download_url download_tarball_name first_install tmp_dir

    set_ghc_major "${myghcver}"

    unset myghcver
}



    ########################
    #--[ Subcommand set ]--#
    ########################


# @FUNCTION: set_ghc
# @USAGE: <ghcversion> [target-suffix]
# @DESCRIPTION:
# Sets the current ghc version by creating symlinks.
set_ghc() {
    [ -z "$1" ] && die "Internal error: no argument given to set_ghc"

    myghcver=$1
    target_suffix=$2
    inst_location=$(get_ghc_location "$1")
    [ -z "${inst_location}" ] && die "failed to get install location"

    [ -e "${inst_location}" ] || die "GHC ${myghcver} not installed yet, use: ${SCRIPT} install ${myghcver}"

    status_message "Setting GHC to ${myghcver}"

    for f in "${inst_location}"/bin/*-"${myghcver}" ; do
        [ -e "${f}" ] || die "Something went wrong, ${f} does not exist!"
        source_fn=$(basename "${f}")
        target_fn="$(echo "${source_fn}" | sed "s#-${myghcver}##")${target_suffix}"
        # shellcheck disable=SC2046
        edo ln $(optionv "-v") -sf ../ghc/"${myghcver}/bin/${source_fn}" "${BIN_LOCATION}/${target_fn}"
        unset source_fn target_fn
    done
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf "runghc${target_suffix}" "${BIN_LOCATION}/runhaskell${target_suffix}"
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf "hsc2hs-${myghcver}" "${BIN_LOCATION}/hsc2hs${target_suffix}"
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf "hp2ps-${myghcver}" "${BIN_LOCATION}/hp2ps${target_suffix}"
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf "hpc-${myghcver}" "${BIN_LOCATION}/hpc${target_suffix}"
    # not all bindists install haddock...
    if [ -e "${inst_location}/bin/haddock" ] ; then
        # shellcheck disable=SC2046
        edo ln $(optionv "-v") -sf "haddock-ghc${target_suffix}" "${BIN_LOCATION}/haddock${target_suffix}"
    fi

    status_message "Done"

    unset myghcver inst_location f target_suffix
}




    ############################
    #--[ Subcommand upgrade ]--#
    ############################


# @FUNCTION: upgrade
# @USAGE: <install-location>
# @DESCRIPTION:
# Downloads the latest version of this script and places it into
# the given directory.
upgrade() {
    target_location=$1

    [ -e "${target_location}" ] || die "Destination \"${target_location}\" does not exist, cannot update script"

    status_message "Updating ${SCRIPT}"

    (
        edo cd "$(mktemp -d -t ghcup.XXXXXXXX)"
        download "${SCRIPT_UPDATE_URL}"
        edo chmod +x ghcup
        edo mv -f ghcup "${target_location}"/ghcup

    ) || die "failed to install"

    status_message "Done"

    unset target_location
}




    #######################
    #--[ Subcommand rm ]--#
    #######################


# @FUNCTION: rm_ghc
# @USAGE: <ghcversion>
# @DESCRIPTION:
# Removes the given GHC version installed by ghcup.
rm_ghc() {
    [ -z "$1" ] && die "Internal error: no argument given to rm_ghc"

    myghcver=$1
    inst_location=$(get_ghc_location "${myghcver}")

    [ -z "${myghcver}" ] && die "We are paranoid, ghcver not set"

    if ghc_already_installed "${myghcver}" ; then
        [ -z "${inst_location}" ] && die "internal error: inst_location empty!"

        if ! ${FORCE} ; then
            if ! ask_for_confirmation "Really removing ${myghcver}? This will also recursively remove the following directory (please double-check): \"${inst_location}\"" ; then
                warning_message "Not removing GHC..."
                return 0
            fi
        fi

        for f in "${BIN_LOCATION}"/*-"${myghcver}" ; do
            # https://tanguy.ortolo.eu/blog/article113/test-symlink
            [ ! -e "${f}" ] && [ ! -h "${f}" ] && {
                warning_message "No existing symlinks for ${myghcver} in ${BIN_LOCATION}, skipping"
                break
            }
            edo rm "${f}"
        done

        edo rm -r "${inst_location}"

        status_message "Successfully removed GHC ${myghcver}."

        # Only run set_ghc_major if there is at least one 8.6.x version left for 8.6.
        if [ -n "$(get_full_ghc_ver "${myghcver%.*}")" ] ; then
            set_ghc_major "${myghcver}"
        fi

        if [ -h "${BIN_LOCATION}/ghc-${myghcver%.*}" ] && [ ! -e "${BIN_LOCATION}/ghc-${myghcver%.*}" ] ; then
            # TODO: known_tools is not very robust, but we want to avoid accidentially deleting
            # unrelated things (even if those are dangling symlinks)
            known_tools="ghc ghci ghc-pkg haddock haddock-ghc runghc runhaskell hp2ps hpc hsc2hs"
            # remove dangling symlinks for ghc, ghci, ...
            for t in ${known_tools} ; do
                if [ -h "${BIN_LOCATION}/${t}-${myghcver%.*}" ] && [ ! -e "${BIN_LOCATION}/${t}-${myghcver%.*}" ] ; then
                    edo rm "${BIN_LOCATION}/${t}-${myghcver%.*}"
                fi
            done
            unset t known_tools
        fi

        if [ -h "${BIN_LOCATION}/ghc" ] && [ ! -e "${BIN_LOCATION}/ghc" ] ; then
            warning_message "Currently active GHC is a dangling symlink, removing..."

            # TODO: known_tools is not very robust, but we want to avoid accidentially deleting
            # unrelated things (even if those are dangling symlinks)
            known_tools="ghc ghci ghc-pkg haddock haddock-ghc runghc runhaskell hp2ps hpc hsc2hs"
            # remove dangling symlinks for ghc, ghci, ...
            for t in ${known_tools} ; do
                if [ -h "${BIN_LOCATION}/${t}" ] && [ ! -e "${BIN_LOCATION}/${t}" ] ; then
                    edo rm "${BIN_LOCATION}/${t}"
                fi
            done
            unset t known_tools

            warning_message "Done."
            warning_message "You may now want to set currently active GHC to a different version via:"
            warning_message "    ghcup set <ghcver>"
        fi
    else
        warning_message "${myghcver} doesn't appear to be installed, skipping"
    fi

    unset myghcver inst_location f
}

    ############################
    #--[ Subcommand install ]--#
    ############################


# @FUNCTION: install_cabal
# @USAGE: <cabalversion>
# @DESCRIPTION:
# Installs the given cabal version.
install_cabal() {
    [ -z "$1" ] && die "Internal error: no argument given to install_cabal"

    mycabalver=$1
    myarch=$(get_arch)
    [ -z "${myarch}" ] && die "failed to get architecture"
    inst_location=$BIN_LOCATION
    download_url=$(get_download_url "cabal-install" "${mycabalver}")
    download_tarball_name=$(basename "${download_url}")

    if [ -z "${download_url}" ] ; then
        die "Could not find an appropriate download for the requested cabal-install-${mycabalver} on your system! Please report a bug at ${BUG_URL}"
    fi

    status_message "Installing cabal-install-${mycabalver} into \"${inst_location}\""

    edo mkdir -p "${inst_location}"

    tmp_dir=$(mktemp -d -t ghcup.XXXXXXXX)
    [ -z "${tmp_dir}" ] && die "Failed to create temporary directory"
    (
        if ${CACHING} ; then
            if [ ! -e "${CACHE_LOCATION}/${download_tarball_name}" ] ; then
                download_to_cache "${download_url}"
            fi
            edo cd "${tmp_dir}"
            unpack "${CACHE_LOCATION}/${download_tarball_name}"
        else
            edo cd "${tmp_dir}"
            download "${download_url}"
            unpack "${download_tarball_name}"
        fi

        edo mv -f cabal "${inst_location}"/cabal
        if [ -e "${tmp_dir}/${download_tarball_name}" ] ; then
            rm "${tmp_dir}/${download_tarball_name}"
        fi
    ) || die "Failed to install cabal-install"

    status_message "Successfully installed cabal-install into"
    status_message "  ${BIN_LOCATION}"
    status_message ""

    unset mycabalver myarch inst_location download_url download_tarball_name tmp_dir
}

# @FUNCTION: compile_ghc
# @USAGE: <ghcversion> <bootstrap-ghc> [build.mk]
# @DESCRIPTION:
# Compile and installs the given GHC version with the
# specified GHC bootstrap version.
# Can additionally take a custom file that will be used
# as build configuration.
compile_ghc() {
    { [ -z "$1" ] || [ -z "$2" ] ;} && die "Internal error: not enough arguments given to compile_ghc"

    myghcver=$1
    bootstrap_ghc=$2
    inst_location=$(get_ghc_location "$1")
    [ -z "${inst_location}" ] && die "failed to get install location"
    download_url="https://downloads.haskell.org/~ghc/${myghcver}/ghc-${myghcver}-src.tar.xz"
    download_tarball_name=$(basename "${download_url}")

    if [ -n "$3" ] ; then
        case "$3" in
            /*) build_config=$3 ;;
            *) build_config="$(pwd)/$3" ;;
        esac
        [ -e "${build_config}" ] || die "specified build config \"${build_config}\" file does not exist!"
    fi

    if ghc_already_installed "${myghcver}" ; then
        if ${FORCE} ; then
            echo "GHC already installed in ${inst_location}, overwriting!"
        else
            die "GHC already installed in ${inst_location}, use --force to overwrite"
        fi
    fi

    status_message "Compiling GHC for version ${myghcver} from source"
    tmp_dir=$(mktemp -d -t ghcup.XXXXXXXX)
    [ -z "${tmp_dir}" ] && die "Failed to create temporary directory"
    (
        if ${CACHING} ; then
            if [ ! -e "${CACHE_LOCATION}/${download_tarball_name}" ] ; then
                download_to_cache "${download_url}"
            fi
            edo cd "${tmp_dir}"
            unpack "${CACHE_LOCATION}/${download_tarball_name}"
        else
            edo cd "${tmp_dir}"
            download "${download_url}"
            unpack "${download_tarball_name}"
        fi

        edo cd "./ghc-${myghcver}"

        if [ -n "${build_config}" ] ; then
            edo cat "${build_config}" > mk/build.mk
        else
            cat <<-EOF > mk/build.mk || die
				V=0
				BUILD_MAN = NO
				BUILD_SPHINX_HTML = NO
				BUILD_SPHINX_PDF = NO
				HADDOCK_DOCS = YES
				GhcWithLlvmCodeGen = YES
				EOF
        fi


        edo ./boot
        edo ./configure --prefix="${inst_location}" --with-ghc="${bootstrap_ghc}"
        emake -j${JOBS}
        emake install

        # clean up
        edo cd ..
        [ -e "${tmp_dir}/${download_tarball_name}" ] && rm "${tmp_dir}/${download_tarball_name}"
        [ -e "${tmp_dir}/ghc-${myghcver}" ] && rm -r "${tmp_dir}/ghc-${myghcver}"
    ) || {
        [ -e "${tmp_dir}/${download_tarball_name}" ] && rm "${tmp_dir}/${download_tarball_name}"
        [ -e "${tmp_dir}/ghc-${myghcver}" ] && rm -r "${tmp_dir}/ghc-${myghcver}"
        die "Failed to install, consider updating this script via:
    ${SCRIPT} upgrade
Also check https://ghc.haskell.org/trac/ghc/wiki/Building/Preparation/Linux for build requirements and follow the instructions."
    }

    for f in "${inst_location}"/bin/*-"${myghcver}" ; do
        [ -e "${f}" ] || die "Something went wrong, ${f} does not exist!"
        fn=$(basename "${f}")
        # shellcheck disable=SC2046
        edo ln $(optionv "-v") -sf ../ghc/"${myghcver}/bin/${fn}" "${BIN_LOCATION}/${fn}"
        unset fn
    done
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/runhaskell "${BIN_LOCATION}/runhaskell-${myghcver}"
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/hsc2hs "${BIN_LOCATION}/hsc2hs-${myghcver}"
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/hp2ps "${BIN_LOCATION}/hp2ps-${myghcver}"
    # shellcheck disable=SC2046
    edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/hpc "${BIN_LOCATION}/hpc-${myghcver}"
    if [ -e "${inst_location}/bin/haddock" ] ; then
        # shellcheck disable=SC2046
        edo ln $(optionv "-v") -sf ../ghc/"${myghcver}"/bin/haddock "${BIN_LOCATION}/haddock-${myghcver}"
    fi

    status_message "Done installing, run \"ghci-${myghcver}\" or set up your current GHC via: ${SCRIPT} set ${myghcver}"

    unset bootstrap_ghc inst_location f download_url download_tarball_name tmp_dir

    set_ghc_major "${myghcver}"

    unset myghcver
}


    ###############################
    #--[ Subcommand debug-info ]--#
    ###############################


# @FUNCTION: print_debug_info
# @DESCRIPTION:
# Print debug info (e.g. detected system/distro).
print_debug_info() {
    echo "Script version: ${VERSION}"
    echo
    echo "Script variables:"
    echo "  GHC install location:     ${GHC_LOCATION}"
    echo "  Binary install location:  ${BIN_LOCATION}"
    echo "  Tarball cache location:   ${CACHE_LOCATION}"
    echo "  Downloader:               ${DOWNLOADER} ${DOWNLOADER_OPTS} <url>"
    echo "  Script update url:        ${SCRIPT_UPDATE_URL}"
    echo "  GHC download baseurl:     ${GHC_DOWNLOAD_BASEURL}"
    echo "  Meta download url         ${META_DOWNLOAD_URL}"
    echo "  Meta download format      ${META_DOWNLOAD_FORMAT}"
    echo "  Meta version url          ${META_VERSION_URL}"
    echo "  Meta version format       ${META_VERSION_FORMAT}"
    echo
    echo "Detected system information:"
    echo "  Architecture:   $(get_arch)"
    echo "  Distribution:   $(get_distro_name)"
    echo "  Distro alias:   $(get_distro_alias "$(get_distro_name)")"
    echo "  Distro version: $(get_distro_ver)"
}


    #########################
    #--[ Subcommand list ]--#
    #########################


# @FUNCTION: list
# @USAGE: <tool> <raw-format> <criteria>
# @DESCRIPTION:
# List available tools and their versions from upstream.
list() {
    mytool=$1
    raw_format=$2
    criteria=$3

    meta_file="$(get_meta_version_file)"
    [ -z "${meta_file}" ] && die "failed to get meta file"

    if ! ${raw_format} ; then
        printf "\\033[1;32m%s\\033[0m\\n" "Available versions:"
    fi

    lines=$(
        if [ "${mytool}" = "all" ] ; then
            awk "
            NF {
                if (\$1 != \"#\") {
                    print \$1 \"\\t\" \$2 \"\\t\" \$3
                }
            }" "${meta_file}" || die "awk failed!"
        else
            awk "
            NF {
                if (\$1 == \"${mytool}\") {
                    print \$1 \"\\t\" \$2 \"\\t\" \$3
                }
            }" "${meta_file}" || die "awk failed!"
        fi
    )

    _print_me() {
        if ${raw_format} ; then
            printf "%s\\n" "$1"
        else
            if [ "$2" = "available" ] ; then
                printf "\\033[0;32m\342\234\224\\033[0m %s\\n" "$1"
            elif [ "$2" = "set" ] ; then
                printf "\\033[0;32m\342\234\224 \\033[0;34m%s\\033[0m\\n" "$1"
            elif [ "$2" = "unavailable" ] ; then
                printf "\\033[0;31m\342\234\227\\033[0m %s\\n" "$1"
            fi
        fi
    }

    if [ -z "${lines}" ] ; then
        (>&2 echo "Nothing found for tool ${mytool}")
        return
    fi


    echo "$lines" | while read -r l; do
        tool=$(echo "${l}" | cut -f1)
        version=$(echo "${l}" | cut -f2)

        if [ "${criteria}" = "set" ] ; then
            if [ "${tool}" = "ghc" ] && [ "${version}" = "$(show_ghc_installed)" ] ; then
                _print_me "${l}" "set"
            fi

            if [ "${tool}" = "cabal-install" ] && [ "${version}" = "$(show_cabal_installed)" ] ; then
                _print_me "${l}" "set"
            fi
        else
            if tool_already_installed "${tool}" "${version}" ; then
                if [ "${tool}" = "ghc" ] && [ "${version}" = "$(show_ghc_installed)" ] ; then
                    _print_me "${l}" "set"
                elif  [ "${tool}" = "cabal-install" ] && [ "${version}" = "$(show_cabal_installed)" ] ; then
                    _print_me "${l}" "set"
                else
                    _print_me "${l}" "available"
                fi
            else
                if [ "${criteria}" != "installed" ] ; then
                    _print_me "${l}" "unavailable"
                fi
            fi
        fi
    done

    unset mytool meta_file l lines tool version raw_format installed_only criteria
}


    ##############################
    #--[ Subcommand changelog ]--#
    ##############################


# @FUNCTION: changelog_url
# @USAGE: <ghcversion>
# @DESCRIPTION:
# Print the changelog url for the given GHC version to stdout.
# @STDOUT: the changelog url
changelog_url() {
    [ -z "$1" ] && die "Internal error: no argument given to changelog"

    printf "https://downloads.haskell.org/~ghc/%s/docs/html/users_guide/%s-notes.html" "$1" "$1"
}


# @FUNCTION: changelog
# @USAGE: <ghcversion>
# @DESCRIPTION:
# Opens the changelog for the given ghc version via xdg-open.
changelog() {
    [ -z "$1" ] && die "Internal error: no argument given to changelog"

    url=$(changelog_url "$1")

    xdg-open "${url}" || die "failed to xdg-open the following url: ${url}"

    unset url
}


    ######################################
    #--[ Subcommand print-system-reqs ]--#
    ######################################


# @FUNCTION: system_reqs_url
# @USAGE: <distro-alias>
# @DESCRIPTION:
# Mapping of distro-alias to system requirements URL.
system_reqs_url() {
    [ -z "$1" ] && die "Internal error: no argument given to system_reqs_url"

    case "$1" in
    "alpine")
        printf "%s/.requirements/ghc/alpine" "${BASE_DOWNLOAD_URL}"
        ;;
    "debian"|"ubuntu")
        printf "%s/.requirements/ghc/ubuntu" "${BASE_DOWNLOAD_URL}"
        ;;
    "darwin")
        printf "%s/.requirements/ghc/darwin" "${BASE_DOWNLOAD_URL}"
        ;;
    *)
        printf "%s/.requirements/ghc/default" "${BASE_DOWNLOAD_URL}"
        ;;
    esac
}


# @FUNCTION: print_system_reqs
# @DESCRIPTION:
# Print the system requirements (approximation).
print_system_reqs() {
    mydistro=$(get_distro_alias "$(get_distro_name)")
    reqs_url=$(system_reqs_url "${mydistro}")

    download_to_stdout "${reqs_url}"

    unset mydistro reqs_url
}




    #######################
    #--[ Sanity checks ]--#
    #######################


if [ -z "${GHCUP_INSTALL_BASE_PREFIX}" ] ; then
    die "GHCUP_INSTALL_BASE_PREFIX empty, cannot operate"
fi

if [ ! -d "${GHCUP_INSTALL_BASE_PREFIX}" ] ; then
    die "${GHCUP_INSTALL_BASE_PREFIX} does not exist"
fi




    ##############################################
    #--[ Command line parsing and entry point ]--#
    ##############################################

[ $# -lt 1 ] && usage

while [ $# -gt 0 ] ; do
    case $1 in
    -v|--verbose)
        VERBOSE=true
        shift 1
        if [ $# -lt 1 ] ; then
            usage
        fi
        ;;
    -V|--version)
        printf "%s\\n" "${VERSION}"
        exit 0;;
    --list-commands)
        echo "changelog
compile
debug-info
install
install-cabal
list
print-system-reqs
rm
set
upgrade"
        exit 0;;
    -h|--help)
        usage;;
    -w|--wget)
        DOWNLOADER="wget"
        DOWNLOADER_OPTS=""
        DOWNLOADER_STDOUT_OPTS="-qO-"
        shift 1
        if [ $# -lt 1 ] ; then
            usage
        fi
        ;;
    -c|--cache)
        CACHING=true
        shift 1
        if [ $# -lt 1 ] ; then
            usage
        fi
        ;;
    *) ## startup tasks ##

       edo mkdir -p "${INSTALL_BASE}"
       edo mkdir -p "${BIN_LOCATION}"
       edo mkdir -p "${CACHE_LOCATION}"

       # clean up old meta files
       if [ -e "${CACHE_LOCATION}/$(basename "${META_VERSION_URL}")" ] ; then
           edo rm "${CACHE_LOCATION}/$(basename "${META_VERSION_URL}")"
       fi
       if [ -e "${CACHE_LOCATION}/$(basename "${META_DOWNLOAD_URL}")" ] ; then
           edo rm "${CACHE_LOCATION}/$(basename "${META_DOWNLOAD_URL}")"
       fi

       # check for available commands
       missing_commands="$(check_required_commands ${DOWNLOADER})"
       if [ -n "${missing_commands}" ] ; then
           die "Following commands are required, but missing, please install: ${missing_commands}"
       fi
       unset missing_commands
       case $1 in
       install)
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) install_usage;;
                   -f|--force) FORCE=true
                       shift 1;;
                   *) GHC_VER=$1
                      break;;
               esac
           done
           if [ -z "${GHC_VER}" ] ; then
               _tool_ver="$(get_tool_ver_from_tag "ghc" "recommended")"
               if [ -z "${_tool_ver}" ] ; then
                   die "Could not find a recommended GHC version, please report a bug at ${BUG_URL}!"
               fi
               install_ghc "${_tool_ver}"
           else
               # could be a version or a tag, let's check
               if array_contains "${GHC_VER}" "$(known_tool_versions "ghc")" ; then
                   install_ghc "${GHC_VER}"
               elif array_contains "${GHC_VER}" "$(known_tool_tags "ghc")" ; then
                   install_ghc "$(get_tool_ver_from_tag "ghc" "${GHC_VER}")"
               else
                   die "\"${GHC_VER}\" is not a known version or tag!"
               fi
           fi
           break;;
       set)
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) set_usage;;
                   *) GHC_VER=$1
                      break;;
               esac
           done

           if [ -z "${GHC_VER}" ] ; then
               _tool_ver="$(get_tool_ver_from_tag "ghc" "recommended")"
               if [ -z "${_tool_ver}" ] ; then
                   die "Could not find a recommended GHC version, please report a bug at ${BUG_URL}!"
               fi
               set_ghc "${_tool_ver}"
           else
               # could be a version or a tag, let's check
               if array_contains "${GHC_VER}" "$(known_tool_versions "ghc")" ; then
                   set_ghc "${GHC_VER}"
               elif array_contains "${GHC_VER}" "$(known_tool_tags "ghc")" ; then
                   set_ghc "$(get_tool_ver_from_tag "ghc" "${GHC_VER}")"
               else
                   die "\"${GHC_VER}\" is not a known version or tag!"
               fi
           fi

           break;;
       upgrade)
           IN_PLACE=false
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) upgrade_usage;;
                   -i|--inplace) IN_PLACE=true
                       shift 1 ;;
                   *) TARGET_LOCATION=$1
                       break;;
               esac
           done
           if ${IN_PLACE} ; then
               upgrade "$(dirname "$(posix_realpath "${SOURCE}")")"
           elif [ -n "${TARGET_LOCATION}" ] ; then
               upgrade "${TARGET_LOCATION}"
           else
               upgrade "${BIN_LOCATION}"
           fi
           break;;
       rm)
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) rm_usage;;
                   -f|--force) FORCE=true
                       shift 1;;
                   *) GHC_VER=$1
                      break;;
               esac
           done
           [ -n "${GHC_VER}" ] || rm_usage
           rm_ghc "${GHC_VER}"
           break;;
       install-cabal)
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) install_cabal_usage;;
                   -f|--force) FORCE=true
                       shift 1;;
                   *) CABAL_VER=$1
                      break;;
               esac
           done
           if [ -n "${CABAL_VER}" ] ; then
               # could be a version or a tag, let's check
               if array_contains "${CABAL_VER}" "$(known_tool_versions "cabal-install")" ; then
                   install_cabal "${CABAL_VER}"
               elif array_contains "${CABAL_VER}" "$(known_tool_tags "cabal-install")" ; then
                   install_cabal "$(get_tool_ver_from_tag "cabal-install" "${CABAL_VER}")"
               else
                   die "\"${CABAL_VER}\" is not a known version or tag!"
               fi
           else
               _cabal_ver="$(get_tool_ver_from_tag "cabal-install" "recommended")"
               if [ -z "${_cabal_ver}" ] ; then
                   die "Could not find a recommended cabal-install version, please report a bug at ${BUG_URL}!"
               fi
               install_cabal "${_cabal_ver}"
           fi
           break;;
       compile)
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) compile_usage;;
                   -f|--force) FORCE=true
                       shift 1;;
                   -j|--jobs) JOBS=$2
                       shift 2;;
                   -c|--build-config) BUILD_CONFIG=$2
                       shift 2;;
                   *) GHC_VER=$1
                      BOOTSTRAP_GHC=$2
                      break;;
               esac
           done
           [ -n "${GHC_VER}" ] || compile_usage
           [ -n "${BOOTSTRAP_GHC}" ] || compile_usage
           compile_ghc "${GHC_VER}" "${BOOTSTRAP_GHC}" "${BUILD_CONFIG}"
           break;;
       debug-info)
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) debug_info_usage;;
                   *) debug_info_usage;;
               esac
           done
           print_debug_info
           break;;
       list)
           RAW_FORMAT=false
           TOOL="ghc"
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) list_usage;;
                   -t|--tool) TOOL=$2
                       shift 2;;
                   -r|--raw-format) RAW_FORMAT=true
                       shift 1;;
                   -c|--show-criteria) SHOW_CRITERIA=$2
                       shift 2;;
                   *) list_usage;;
               esac
           done
           list "${TOOL}" ${RAW_FORMAT} "${SHOW_CRITERIA}"
           break;;
       changelog)
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) changelog_usage;;
                   -f|--force) FORCE=true
                       shift 1;;
                   *) GHC_VER=$1
                      break;;
               esac
           done
           if [ -z "${GHC_VER}" ] ; then
               _tool_ver="$(get_tool_ver_from_tag "ghc" "latest")"
               if [ -z "${_tool_ver}" ] ; then
                   die "Could not find a latest GHC version, please report a bug at ${BUG_URL}!"
               fi
               changelog "${_tool_ver}"
           else
               # could be a version or a tag, let's check
               if array_contains "${GHC_VER}" "$(known_tool_versions "ghc")" ; then
                   changelog "${GHC_VER}"
               elif array_contains "${GHC_VER}" "$(known_tool_tags "ghc")" ; then
                   changelog "$(get_tool_ver_from_tag "ghc" "${GHC_VER}")"
               else
                   die "\"${GHC_VER}\" is not a known version or tag!"
               fi
           fi
           break;;
       print-system-reqs)
           shift 1
           while [ $# -gt 0 ] ; do
               case $1 in
                   -h|--help) print_system_reqs_usage;;
                   *) print_system_reqs_usage;;
               esac
           done
           print_system_reqs
           break;;
       *) usage;;
       esac
       break;;
    esac
done


# vim: tabstop=4 shiftwidth=4 expandtab