#!/bin/bash

# check for packages that need to be built, and build a list in the proper build order
# Details:
#  https://github.com/archlinux32/builder/wiki/Build-system#get-package-updates

set -e

lock_file="/tmp/get-package-updates.lock"

# TODO:
#  include repository of package customizations

declare -A repo_paths
repo_paths["packages"]="/usr/src/archlinux/packages"
repo_paths["community"]="/usr/src/archlinux/community"

base_dir="$(dirname "$(readlink -f "$0")")/.."

# Create a lock file for build list.

exec 9>"${lock_file}"
flock -n 9 || exit

# Update git repositories (official packages, community packages and the repository of package customizations).

for repo in "${repo_paths[@]}"; do
  git -C "${repo}" pull
done

# Read previous git revision numbers from files.

declare -A old_repo_revisions

for repo in "${!repo_paths[@]}"; do
  old_repo_revisions["${repo}"]="$(cat ${base_dir}/work/${repo}.revision)"
done

# Check modified packages from the last update, and put them to the build list.
# If a package is updated, but already on the rebuild list, then just update the git revision number.
# If a package is deleted, remove from the rebuild list, and add it to the deletion list.
# If a new package is added, then ensure that it's not on the deletion list.

for repo in "${!repo_paths[@]}"; do
  current_HEAD="$(
    git -C "${repo_paths["${repo}"]}" rev-parse HEAD
  )"
  git -C "${repo_paths["${repo}"]}" diff --name-status "${old_repo_revisions["${repo}"]}" HEAD | \
    grep '^.\s[^/]\+/repos/[^/]\+/PKGBUILD$' | \
    sed 's|^\(.\)\t\([^/]\+\)/repos/\([^/]\+\)-[^/-]\+/PKGBUILD$|\1 \2 '"${current_HEAD}"' \3|' | \
    grep -v '\(staging\|testing\)$'
done | \
  sort -u | \
  while read -r mode package git_revision repository; do
    case "${mode}" in

      "A"|"M")
        sed -i "/^${package} /d" "${base_dir}/work/build-list"
        echo "${package} ${git_revision} ${repository}" >> \
          "${base_dir}/work/build-list"
        sed -i "/^${package}/d" "${base_dir}/work/deletion-list"
      ;;

      "D")
        echo "${package}" >> \
          "${base_dir}/work/deletion-list"
        sed -i "/^${package} /d" "${base_dir}/work/build-list"
      ;;

      *)
        >&2 echo "unknown git diff mode '${mode}'"
        exit 1
      ;;

    esac
  done

# TODO:
#  Put the list in the proper build order.

# Write the current git revision numbers to files.

for repo in "${!repo_paths[@]}"; do
  git -C "${repo_paths["${repo}"]}" rev-parse HEAD > \
    "${base_dir}/work/${repo}.revision"
done

# Remove the lock file

rm -f "${lock_file}"