#!/usr/bin/env bash

# Install a release of lutinglt/gitea-github-theme into Gitea asset directories.
set -euo pipefail

readonly REPOSITORY="lutinglt/gitea-github-theme"
readonly BASE_ARCHIVE="theme-github.tar.gz"
readonly TEMPLATES_ARCHIVE="theme-github-templates.tar.gz"
STAGING_DIR=""

require_command() {
  command -v "$1" >/dev/null 2>&1 || {
    printf 'Required command not found: %s\n' "$1" >&2
    exit 1
  }
}

download_archive() {
  local archive_name="$1"
  local release_path="$2"
  local destination="$3"
  local url="https://github.com/${REPOSITORY}/releases/${release_path}/${archive_name}"

  printf 'Downloading %s...\n' "$archive_name"
  curl --fail --location --retry 3 --output "$destination" "$url"
}

prepare_directory() {
  local directory="$1"

  if [[ -z "$directory" ]]; then
    printf 'A destination directory is required.\n' >&2
    exit 1
  fi
  if [[ -e "$directory" && ! -d "$directory" ]]; then
    printf 'Destination exists but is not a directory: %s\n' "$directory" >&2
    exit 1
  fi

  mkdir -p "$directory"
  directory="$(cd "$directory" && pwd -P)"
  if [[ "$directory" == "/" ]]; then
    printf 'Refusing to use the filesystem root as a destination.\n' >&2
    exit 1
  fi

  printf '%s\n' "$directory"
}

default_manifest_path() {
  local css_destination="$1"
  local templates_destination="$2"
  local state_directory manifest_key

  if [[ -n "${GITEA_GITHUB_THEME_STATE_DIR:-}" ]]; then
    state_directory="$GITEA_GITHUB_THEME_STATE_DIR"
  elif [[ $EUID -eq 0 ]]; then
    state_directory="/var/lib/gitea-github-theme"
  else
    state_directory="${XDG_STATE_HOME:-${HOME:-.}/.local/state}/gitea-github-theme"
  fi

  manifest_key="$(printf '%s\0%s' "$css_destination" "$templates_destination" | sha256sum | awk '{print $1}')"
  printf '%s/%s.manifest\n' "$state_directory" "$manifest_key"
}

remove_theme_files() {
  local css_destination="$1"
  local templates_destination="$2"
  local manifest="$3"
  local file_type relative_path destination

  if [[ -f "$manifest" ]]; then
    while IFS=$'\t' read -r file_type relative_path; do
      case "$file_type" in
        css) destination="$css_destination" ;;
        template) destination="$templates_destination" ;;
        *) continue ;;
      esac

      # The manifest is generated locally, but still reject paths that can escape a destination.
      if [[ -z "$relative_path" || "$relative_path" == /* || "$relative_path" == ".." || \
        "$relative_path" == ../* || "$relative_path" == */../* || "$relative_path" == */.. ]]; then
        continue
      fi
      rm -f -- "$destination/$relative_path"
    done < "$manifest"
    rm -f -- "$manifest"
  fi

  # Also remove CSS installed by older versions of this script, which had no manifest.
  find "$css_destination" -maxdepth 1 -type f -name 'theme-github-*.css' -delete
}

write_manifest() {
  local manifest="$1"
  local base_source="$2"
  local templates_source="$3"
  local temporary_manifest file

  mkdir -p "$(dirname "$manifest")"
  temporary_manifest="$(mktemp "${manifest}.XXXXXX")"
  {
    while IFS= read -r -d '' file; do
      printf 'css\t%s\n' "${file#"$base_source"/}"
    done < <(find "$base_source" -type f -print0)
    while IFS= read -r -d '' file; do
      printf 'template\t%s\n' "${file#"$templates_source"/}"
    done < <(find "$templates_source" -type f -print0)
  } > "$temporary_manifest"
  mv -f -- "$temporary_manifest" "$manifest"
}

main() {
  local version css_destination templates_destination manifest release_path

  require_command find
  require_command sha256sum
  require_command awk

  if [[ "${1:-}" == "--print-manifest-path" ]]; then
    css_destination="$(prepare_directory "${2:-}")"
    templates_destination="$(prepare_directory "${3:-}")"
    default_manifest_path "$css_destination" "$templates_destination"
    return
  fi

  if [[ "${1:-}" == "--remove" ]]; then
    css_destination="$(prepare_directory "${2:-}")"
    templates_destination="$(prepare_directory "${3:-}")"
    manifest="${4:-$(default_manifest_path "$css_destination" "$templates_destination")}"
    remove_theme_files "$css_destination" "$templates_destination" "$manifest"
    printf 'Removed installed Gitea GitHub theme files.\n'
    return
  fi

  require_command curl
  require_command tar
  require_command mktemp

  version="${1:-}"
  if [[ -z "$version" ]]; then
    read -r -p "Theme version (for example v1.27.0, or latest) [latest]: " version
  fi
  version="${version:-latest}"
  version="${version#v}"

  css_destination="${2:-}"
  if [[ -z "$css_destination" ]]; then
    read -r -p "CSS destination (for example /path/to/gitea/public/assets/css): " css_destination
  fi
  css_destination="$(prepare_directory "$css_destination")"

  templates_destination="${3:-}"
  if [[ -z "$templates_destination" ]]; then
    read -r -p "Templates destination (for example /path/to/gitea/templates): " templates_destination
  fi
  templates_destination="$(prepare_directory "$templates_destination")"
  manifest="${4:-$(default_manifest_path "$css_destination" "$templates_destination")}"

  if [[ "$version" == "latest" ]]; then
    release_path="latest/download"
  else
    release_path="download/v${version}"
  fi

  STAGING_DIR="$(mktemp -d)"
  trap 'rm -rf -- "$STAGING_DIR"' EXIT

  download_archive "$BASE_ARCHIVE" "$release_path" "$STAGING_DIR/$BASE_ARCHIVE"
  download_archive "$TEMPLATES_ARCHIVE" "$release_path" "$STAGING_DIR/$TEMPLATES_ARCHIVE"

  # Verify the archives and their expected top-level directories before changing Gitea files.
  mkdir -p "$STAGING_DIR/base" "$STAGING_DIR/templates"
  tar -xzf "$STAGING_DIR/$BASE_ARCHIVE" -C "$STAGING_DIR/base"
  tar -xzf "$STAGING_DIR/$TEMPLATES_ARCHIVE" -C "$STAGING_DIR/templates"
  if [[ ! -d "$STAGING_DIR/base/dist" || ! -d "$STAGING_DIR/templates/templates" ]]; then
    printf 'Downloaded archives do not have the expected dist/ and templates/ layout.\n' >&2
    exit 1
  fi

  printf 'Replacing GitHub theme files...\n'
  remove_theme_files "$css_destination" "$templates_destination" "$manifest"
  tar -xzf "$STAGING_DIR/$BASE_ARCHIVE" --strip-components=1 -C "$css_destination"
  tar -xzf "$STAGING_DIR/$TEMPLATES_ARCHIVE" --strip-components=1 -C "$templates_destination"
  write_manifest "$manifest" "$STAGING_DIR/base/dist" "$STAGING_DIR/templates/templates"

  printf 'Installed Gitea GitHub theme %s; manifest written to %s.\n' "$version" "$manifest"
}

main "$@"