#! /usr/bin/env bash
set -e

show-help() {
  echo 'usage: evm <command>'
  echo ''
  echo 'Commands:'
  echo '  help               - Show this message'
  echo '  info               - Show evm configuration details.'
  echo '  list               - List installed versions.'
  echo '  use <version>      - Activate specified version.'
  echo '  install <git-ref>  - Download, compile and install Emacs.'
  echo '  build-deps         - Install build dependencies for Emacs.'
}

main() {
  local command="$1"
  shift 1

  check-os

  if [ -z "$command" ]; then
    show-help 1>&2
    exit 1
  fi

  case "$command" in
    build-deps | deps)
      install-deps "$@"
      ;;
    info)
      info
      ;;
    install)
      install "$@"
      ;;
    use | switch | activate)
      activate-version "$@"
      ;;
    list | ls | versions)
      versions "$@"
      ;;
    *)
      show-help
      ;;
  esac
}

check-os() {
  if [[ "$OSTYPE" != "linux"* ]]; then
    echo "Only Linux-based operating systems are supported" 1>&2
    exit 2
  fi
}

check-write-op() {
  if conf-root-mode && [ "$UID" != "0" ]; then
    echo "ERROR: evm must be run as root when" \
      "EVM_MODE is not empty or \"user\"." 1>&2
    exit 1
  fi
}

trim() {
  local string="$*"
  string="${string#"${string%%[![:space:]]*}"}"
  string="${string%"${string##*[![:space:]]}"}"
  echo -n "$string"
}

conf-emacs-src-repo() {
  echo "${EVM_EMACS_SRC_REPO:-emacs-mirror/emacs}"
}

conf-mode() {
  if [ "${EVM_MODE:-user}" == "user" ]; then
    echo "user"
  else
    echo "root"
  fi
}

conf-root-mode() {
  if [ "$(conf-mode)" != "root" ]; then
    return 1
  fi
}

default-root-dir() {
  if conf-root-mode; then
    echo "/opt/evm"
  else
    echo "$HOME/.evm"
  fi
}

default-shims-dir() {
  if conf-root-mode; then
    echo "$(conf-root-dir)/bin"
  else
    echo "$(conf-root-dir)/shims"
  fi
}

conf-root-dir() {
  echo "${EVM_ROOT_DIR:-$(default-root-dir)}"
}

conf-shims-dir() {
  echo "${EVM_VERSIONS_DIR:-$(default-shims-dir)}"
}

conf-versions-dir() {
  echo "${EVM_VERSIONS_DIR:-$(conf-root-dir)/versions}"
}

conf-sources-dir() {
  echo "${EVM_SOURCES_DIR:-$(conf-root-dir)/sources}"
}

conf-native-full-aot() {
  echo "${EVM_NATIVE_FULL_AOT:-1}"
}

info() {
  echo "---"
  echo "# evm information"
  echo "evm:"
  echo "  mode: $(conf-mode)"
  echo "  paths:"
  echo "    root: $(conf-root-dir)"
  echo "    shims: $(conf-shims-dir)"
  echo "    versions: $(conf-versions-dir)"
  echo "    sources: $(conf-sources-dir)"
  echo "  building:"
  echo "    native_full_aot: $(conf-native-full-aot)"
}

install() {
  local ref="$1"
  local version
  local workdir
  local dir
  local file
  local prefix

  check-write-op

  if [ -z "$ref" ]; then
    echo "ERROR: git ref to install must be specified" 1>&2
    exit 1
  fi

  version="${ref//\//-}_$(date +"%Y-%m-%d")"
  workdir="$(conf-sources-dir)"
  prefix="$(conf-versions-dir)/${version}"

  file="emacs-${version}.tar.gz"
  dir="emacs-${version}"

  if [ -d "$prefix" ]; then
    echo "target $prefix directory exists, remove to force-install" 1>&2
    exit 1
  fi

  mkdir -p "$workdir"
  cd "$workdir"
  if [ ! -d "$dir" ]; then
    if [ ! -f "$file" ]; then
      curl -L "https://github.com/$(conf-emacs-src-repo)/tarball/${ref}" > \
        "$file"
    else
      echo "source tarball ${workdir}/${file} exists, reusing..." 1>&2
    fi
    mkdir "$dir"
    tar -C "$dir" --strip-components 1 -zxf "$file"
  else
    echo "source directory ${workdir}/${dir} exists, reusing..." 1>&2
  fi
  cd "$dir"

  if [ -f "autogen/copy_autogen" ]; then
    ./autogen/copy_autogen
  fi

  if [ -f "autogen.sh" ]; then
    ./autogen.sh
  fi

  export CFLAGS="-O2"
  export CC=/usr/bin/gcc-10 CXX=/usr/bin/gcc-10
  ./configure \
    --prefix="$prefix" \
    --with-json \
    --with-modules \
    --with-native-compilation \
    --with-pgtk \
    --with-xinput2 \
    --with-xwidgets
  make -j "$(nproc)" NATIVE_FULL_AOT="$(conf-native-full-aot)"
  make install
}

install-deps() {
  sudo apt-get update
  sudo apt-get install -y \
    build-essential \
    g++-10 \
    gcc-10 \
    libcairo2-dev \
    libgccjit-10-dev \
    libgccjit0 \
    libgconf2-dev \
    libgif-dev \
    libgnutls28-dev \
    libgpm-dev \
    libgtk-3-dev \
    libharfbuzz-dev \
    libjansson-dev \
    libjansson4 \
    libjpeg-dev \
    libjpeg-dev \
    libm17n-dev \
    libmagick++-dev \
    libmagickcore-dev \
    libmailutils-dev \
    libncurses-dev \
    libotf-dev \
    libpng-dev \
    librsvg2-dev \
    libtiff-dev \
    libwebp-dev \
    libx11-dev \
    libxft-dev \
    libxml2-dev \
    libxpm-dev \
    texinfo \
    xaw3dg-dev
}

current-version() {
  trim "$(cat "$(conf-root-dir)/current" 2> /dev/null)"
}

activate-version() {
  local version="$1"
  local dir
  local target
  local base

  check-write-op

  if [ -z "$version" ]; then
    echo "ERROR: version be specified" 1>&2
    exit 1
  fi

  dir="$(conf-versions-dir)/${version}"

  if [ ! -d "$dir" ]; then
    echo "ERROR: version ${version} is not installed" 1>&2
    exit 1
  fi

  mkdir -p "$(conf-shims-dir)"

  # Remove old symlinks.
  find "$(conf-shims-dir)" -maxdepth 1 -mindepth 1 -type l -delete

  # Create new symlinks.
  find "${dir}/bin" -type f -perm -a=x -exec ln -s "{}" "$(conf-shims-dir)/" \;

  # Create symlink to `emacs` in case it is a symlink itself.
  if [ -L "${dir}/bin/emacs" ]; then
    ln -s "${dir}/bin/emacs" "$(conf-shims-dir)/"
  fi

  echo "$(trim "$version")" > "$(conf-root-dir)/current"
}

versions() {
  local version_dirs
  local version_dir
  local version

  version_dirs="$(find "$(conf-versions-dir)" -maxdepth 1 -mindepth 1 -type d \
    -exec basename "{}" \;)"

  while read -r version_dir; do
    version="$(basename "$version_dir")"

    if [ "$(trim "$version")" == "$(trim "$(current-version)")" ]; then
      echo "* ${version}"
    else
      echo "  ${version}"
    fi
  done < <(echo "$version_dirs")
}

print-version() {
  local version_dir="$1"
  local version
  version="$(basename "$version_dir")"

  if [ "$(trim "$version")" == "$(trim "$(current-version)")" ]; then
    echo "* ${version}"
  else
    echo "  ${version}"
  fi
}

main "$@"