#!/bin/sh
set -eu

repository="chasebryan/centl"
channel=${CENTL_CHANNEL:-}
release_version="latest"
release_base_url=${CENTL_RELEASE_BASE_URL:-}
archive_path=""
prefix=${CENTL_PREFIX:-}
configure_path=true

usage() {
  cat <<'EOF'
Install CENTL on GNU/Linux.

Usage: ./install [--channel oasis|mirage] [--version VERSION]
                 [--release-base-url URL] [--prefix PATH]
                 [--archive PATH] [--no-path]

  --channel CHANNEL          install Oasis (stable) or Mirage (development)
  --version VERSION          install a specific Oasis version or Mirage build
                             (default: latest for the selected channel)
  --release-base-url URL     use URL/vVERSION as a custom release directory
                             (HTTPS or file://; requires explicit --version)
  --prefix PATH              install below PATH (default: ~/.local)
  --archive PATH             install and verify a local Linux release archive
  --no-path                  do not update a shell startup file when PATH needs setup
  --help                     show this help

Environment:
  CENTL_CHANNEL              same as --channel
  CENTL_RELEASE_BASE_URL     same as --release-base-url
  CENTL_PREFIX               same as --prefix

When both channels are installed they coexist. Oasis provides the conventional
centl, centl-physics, and centl-sci commands. Channel-specific launchers are:

  oasis-centl                mirage-centl
  oasis-centl-physics        mirage-centl-physics
  oasis-centl-sci            mirage-centl-sci
EOF
}

fail() {
  printf 'centl install: %s\n' "$1" >&2
  exit 1
}

shell_quote() {
  escaped=$(printf '%s' "$1" | sed "s/'/'\\\\''/g")
  printf "'%s'" "$escaped"
}

while [ "$#" -gt 0 ]; do
  case "$1" in
    --channel)
      [ "$#" -ge 2 ] || fail "--channel needs a value"
      channel=$2
      shift 2
      ;;
    --version)
      [ "$#" -ge 2 ] || fail "--version needs a value"
      release_version=$2
      shift 2
      ;;
    --release-base-url)
      [ "$#" -ge 2 ] || fail "--release-base-url needs a URL"
      release_base_url=$2
      shift 2
      ;;
    --prefix)
      [ "$#" -ge 2 ] || fail "--prefix needs a path"
      prefix=$2
      shift 2
      ;;
    --archive)
      [ "$#" -ge 2 ] || fail "--archive needs a path"
      archive_path=$2
      shift 2
      ;;
    --no-path)
      configure_path=false
      shift
      ;;
    --help|-h)
      usage
      exit 0
      ;;
    *) fail "unknown option: $1" ;;
  esac
done

if [ -z "$channel" ]; then
  if [ -t 0 ] && [ -t 1 ]; then
    printf '%s\n' 'Choose a CENTL channel:'
    printf '%s\n' '  1) Oasis  - qualified stable product (recommended)'
    printf '%s\n' '  2) Mirage - development and experimental product'
    printf 'Selection [1]: '
    IFS= read -r selection || selection=""
    case "$selection" in
      ''|1|oasis|Oasis|OASIS) channel=oasis ;;
      2|mirage|Mirage|MIRAGE) channel=mirage ;;
      *) fail "unknown channel selection: $selection" ;;
    esac
  else
    channel=oasis
  fi
fi

case "$channel" in
  oasis|mirage) ;;
  *) fail "--channel must be oasis or mirage" ;;
esac

[ -n "$prefix" ] || {
  [ -n "${HOME:-}" ] || fail "HOME is not set; use --prefix PATH"
  prefix="$HOME/.local"
}
case "$prefix" in
  *'
'*) fail "the installation prefix cannot contain a newline" ;;
  /*) ;;
  *) prefix="$(pwd)/$prefix" ;;
esac

if [ -n "$archive_path" ] && [ -n "$release_base_url" ]; then
  fail "--archive and --release-base-url are mutually exclusive"
fi
if [ -n "$release_base_url" ]; then
  case "$release_base_url" in
    *'
'*) fail "the release base URL cannot contain a newline" ;;
    https://*|file://*) ;;
    *) fail "the release base URL must use https:// or file://" ;;
  esac
  [ "$release_version" != latest ] ||
    fail "a custom release base URL requires an explicit --version"
fi

case $(uname -s) in
  Linux) platform=linux ;;
  Darwin) fail "macOS is currently unsupported; CENTL native releases are GNU/Linux only" ;;
  *) fail "CENTL native releases currently support GNU/Linux only" ;;
esac

case $(uname -m) in
  x86_64|amd64) architecture=x86_64 ;;
  *) fail "Linux prebuilt releases currently support x86_64 only: $(uname -m)" ;;
esac

asset="centl-${platform}-${architecture}.tar.gz"
temporary=$(mktemp -d "${TMPDIR:-/tmp}/centl-install.XXXXXXXX")
staging=""
cleanup() {
  rm -rf "$temporary"
  if [ -n "$staging" ] && [ -d "$staging" ]; then
    rm -rf "$staging"
  fi
}
trap cleanup EXIT HUP INT TERM

archive="$temporary/$asset"
checksum="$temporary/$asset.sha256"
requested_release=""
source_label="local archive"

if [ -n "$archive_path" ]; then
  [ -f "$archive_path" ] || fail "archive not found: $archive_path"
  [ -f "$archive_path.sha256" ] ||
    fail "checksum not found: $archive_path.sha256"
  cp "$archive_path" "$archive"
  cp "$archive_path.sha256" "$checksum"
else
  command -v curl >/dev/null 2>&1 || fail "curl is required to download CENTL"

  if [ -n "$release_base_url" ]; then
    requested_release=${release_version#v}
    case "$requested_release" in
      ''|*/*|*..*|*[!0-9A-Za-z.+_-]*) fail "the requested release version is invalid" ;;
    esac
    base_url="${release_base_url%/}/v$requested_release"
    source_label="$base_url"
  else
    channel_root="https://raw.githubusercontent.com/$repository/distribution/channels/$channel"
    if [ "$channel" = oasis ]; then
      if [ "$release_version" = latest ]; then
        curl --fail --silent --show-error --location \
          "$channel_root/LATEST" --output "$temporary/LATEST"
        requested_release=$(sed -n '1p' "$temporary/LATEST")
      else
        requested_release=${release_version#v}
      fi
      case "$requested_release" in
        ''|*/*|*..*|*[!0-9A-Za-z.+_-]*) fail "the requested Oasis version is invalid" ;;
      esac
      base_url="$channel_root/v$requested_release"
      source_label="Oasis v$requested_release"
    else
      if [ "$release_version" = latest ]; then
        base_url="$channel_root/latest"
        source_label="latest Mirage build"
      else
        requested_release=${release_version#v}
        case "$requested_release" in
          ''|*/*|*..*|*[!0-9A-Za-z.+_-]*) fail "the requested Mirage build is invalid" ;;
        esac
        base_url="$channel_root/builds/$requested_release"
        source_label="Mirage build $requested_release"
      fi
    fi
  fi

  printf 'Downloading CENTL %s channel (%s) for %s-%s...\n' \
    "$channel" "$source_label" "$platform" "$architecture"
  curl --fail --silent --show-error --location \
    "$base_url/$asset" --output "$archive"
  curl --fail --silent --show-error --location \
    "$base_url/$asset.sha256" --output "$checksum"
fi

expected=$(awk 'NR == 1 { print $1 }' "$checksum")
case "$expected" in
  *[!0-9a-fA-F]*|'') fail "the release checksum is malformed" ;;
esac
[ "${#expected}" -eq 64 ] || fail "the release checksum is malformed"
expected=$(printf '%s' "$expected" | tr 'A-F' 'a-f')

if command -v sha256sum >/dev/null 2>&1; then
  actual=$(sha256sum "$archive" | awk '{ print $1 }')
elif command -v shasum >/dev/null 2>&1; then
  actual=$(shasum -a 256 "$archive" | awk '{ print $1 }')
else
  fail "sha256sum or shasum is required to verify CENTL"
fi
[ "$actual" = "$expected" ] || fail "release checksum verification failed"

command -v tar >/dev/null 2>&1 || fail "tar is required to install CENTL"
tar -tvzf "$archive" | while IFS= read -r listing; do
  entry_type=${listing%"${listing#?}"}
  case "$entry_type" in
    -|d) ;;
    *) fail "the release archive contains a link or unsupported filesystem entry" ;;
  esac
done

tar -tzf "$archive" | while IFS= read -r member; do
  case "$member" in
    /*|../*|*/../*|*/..) fail "the release archive contains an unsafe path" ;;
    centl|centl/*) ;;
    *) fail "the release archive has an unexpected layout" ;;
  esac
done

extracted="$temporary/extracted"
mkdir "$extracted"
tar --no-same-owner --no-same-permissions -xzf "$archive" -C "$extracted"
package="$extracted/centl"
[ -x "$package/bin/centl" ] || fail "the release contains no CENTL launcher"
[ -x "$package/libexec/centl" ] || fail "the release contains no CENTL executable"
[ -f "$package/VERSION" ] || fail "the release contains no version metadata"

physics_available=false
if [ -e "$package/bin/centl-physics" ] || [ -e "$package/libexec/centl-physics" ]; then
  [ -x "$package/bin/centl-physics" ] || fail "the release contains an invalid CENTL Physics launcher"
  [ -x "$package/libexec/centl-physics" ] || fail "the release contains an invalid CENTL Physics executable"
  physics_available=true
fi

sci_available=false
if [ -e "$package/bin/centl-sci" ] || [ -e "$package/libexec/centl-sci" ]; then
  [ -x "$package/bin/centl-sci" ] || fail "the release contains an invalid CENTL-SCi launcher"
  [ -x "$package/libexec/centl-sci" ] || fail "the release contains an invalid CENTL-SCi executable"
  sci_available=true
fi

version=$(sed -n '1p' "$package/VERSION")
case "$version" in
  ''|*/*|*..*|*[!0-9A-Za-z.+_-]*) fail "the release version is invalid" ;;
esac
if [ "$channel" = oasis ] && [ -n "$requested_release" ]; then
  [ "$version" = "$requested_release" ] ||
    fail "requested $requested_release but the archive contains $version"
fi

hash_short=$(printf '%s' "$actual" | cut -c1-12)
if [ "$channel" = oasis ]; then
  install_id=$version
else
  install_id="$version-$hash_short"
fi
versions="$prefix/share/centl/channels/$channel"
target="$versions/$install_id"
bin_directory="$prefix/bin"
channel_centl="$bin_directory/$channel-centl"
channel_physics="$bin_directory/$channel-centl-physics"
channel_sci="$bin_directory/$channel-centl-sci"

for command_path in "$channel_centl" "$channel_physics" "$channel_sci"; do
  if [ -e "$command_path" ] && [ ! -L "$command_path" ]; then
    fail "$command_path already exists and is not a symbolic link"
  fi
done

if [ "$channel" = oasis ]; then
  for command_path in "$bin_directory/centl" "$bin_directory/centl-physics" "$bin_directory/centl-sci"; do
    if [ -e "$command_path" ] && [ ! -L "$command_path" ]; then
      fail "$command_path already exists and is not a symbolic link"
    fi
  done
fi

mkdir -p "$versions" "$bin_directory"
if [ -e "$target" ]; then
  fail "CENTL $channel build $install_id is already installed at $target"
fi

staging=$(mktemp -d "$versions/.centl-$install_id.XXXXXXXX")
cp -R "$package/." "$staging/"
if ! runtime_version=$("$staging/bin/centl" --version 2>&1); then
  fail "the CENTL executable cannot run on this system: $runtime_version"
fi
[ "$runtime_version" = "centl $version" ] ||
  fail "the executable reports '$runtime_version', expected 'centl $version'"
if [ "$physics_available" = true ]; then
  physics_smoke=$("$staging/bin/centl-physics" convert 100 cm m 2>&1) ||
    fail "the CENTL Physics executable cannot run on this system: $physics_smoke"
  [ "$physics_smoke" = 1 ] || fail "the CENTL Physics executable failed its unit-conversion smoke test"
fi
if [ "$sci_available" = true ]; then
  sci_smoke=$("$staging/bin/centl-sci" 'What is 0.1 plus 0.2?' 2>&1) ||
    fail "the CENTL-SCi executable cannot run on this system: $sci_smoke"
  [ "$sci_smoke" = '3/10' ] || fail "the CENTL-SCi executable failed its exact-arithmetic smoke test"
  sci_repl_smoke=$(printf ':exit\n' | "$staging/bin/centl-sci" --repl 2>&1) ||
    fail "the CENTL-SCi REPL cannot start on this system: $sci_repl_smoke"
  printf '%s\n' "$sci_repl_smoke" | grep -Eq '^CENTL-SCi v' ||
    fail "the CENTL-SCi REPL did not report its identity"
  printf '%s\n' "$sci_repl_smoke" | grep -Fqx 'Free for science.' ||
    fail "the CENTL-SCi REPL did not report its scientific identity"
fi

mv "$staging" "$target"
staging=""
ln -sfn "$target/bin/centl" "$channel_centl"
if [ "$physics_available" = true ]; then
  ln -sfn "$target/bin/centl-physics" "$channel_physics"
fi
if [ "$sci_available" = true ]; then
  ln -sfn "$target/bin/centl-sci" "$channel_sci"
fi

if [ "$channel" = oasis ]; then
  ln -sfn "$target/bin/centl" "$bin_directory/centl"
  if [ "$physics_available" = true ]; then
    ln -sfn "$target/bin/centl-physics" "$bin_directory/centl-physics"
  fi
  if [ "$sci_available" = true ]; then
    ln -sfn "$target/bin/centl-sci" "$bin_directory/centl-sci"
  fi
fi

path_profile=""
case ":${PATH:-}:" in
  *":$bin_directory:"*) path_active=true ;;
  *) path_active=false ;;
esac

if [ "$path_active" = false ] && [ "$configure_path" = true ] && [ -n "${HOME:-}" ]; then
  shell_path=${SHELL:-}
  shell_name=${shell_path##*/}
  case "$shell_name" in
    bash) profile="$HOME/.bashrc" ;;
    zsh) profile="$HOME/.zshrc" ;;
    *) profile="$HOME/.profile" ;;
  esac
  marker="# CENTL PATH: $bin_directory"
  if [ ! -f "$profile" ] || ! grep -Fqx "$marker" "$profile"; then
    quoted_bin=$(shell_quote "$bin_directory")
    {
      printf '\n%s\n' "$marker"
      printf 'export PATH=%s:"$PATH"\n' "$quoted_bin"
    } >> "$profile"
  fi
  path_profile=$profile
fi

printf 'Installed CENTL %s channel, build %s at %s\n' "$channel" "$install_id" "$target"
printf 'Channel command: %s\n' "$channel_centl"
if [ "$physics_available" = true ]; then
  printf 'Channel physics command: %s\n' "$channel_physics"
fi
if [ "$sci_available" = true ]; then
  printf 'Channel scientific command: %s\n' "$channel_sci"
fi
if [ "$channel" = oasis ]; then
  printf 'Stable command: %s\n' "$bin_directory/centl"
fi

if [ "$path_active" = false ] && [ -n "$path_profile" ]; then
  printf 'PATH configured in %s for new shells.\n' "$path_profile"
  printf 'Open a new terminal to use the installed commands.\n'
elif [ "$path_active" = false ]; then
  printf 'Add %s to PATH to use the installed commands.\n' "$bin_directory"
fi

if [ "$channel" = oasis ]; then
  printf '\nOasis is ready. Start with: centl-sci\n'
else
  printf '\nMirage is ready. Start with: mirage-centl-sci\n'
fi