#!/bin/bash

if [ $# -eq 2 ]; then
  cd "${1}"
  if [ ! -f '.SRCINFO' ] ||
    [ "$(stat -c%Y PKGBUILD)" -gt "$(stat -c%Y .SRCINFO)" ]; then
    makepkg --printsrcinfo > .SRCINFO
  fi
  sed '
    /^\S/ b
    /^\s\+\(arch\|epoch\|pkgver\|pkgrel\) = \S/ b
    /^$/ b
    d
  ' '.SRCINFO' \
  > "${2}"
  all=$(
    sed -n '
      /^pkgbase = /,/^$/ {
        /^\s/ p
      }
    ' "${2}" \
    | sed '
      $! s/$/\\/
    '
  )
  all_noarch=$(
    printf '%s\n' "${all}" \
    | grep -v '^\sarch = ' \
    | sed '
      $ s/\\$//
    '
  )
  sed -i '
    /^pkgbase = /,/^$/ d
    /^pkgname = / {
      :a
        N
        /\n$/ ! ba
      /\n\sarch = / {
        a\
'"${all_noarch}"'
        b
      }
      a\
'"${all}"'
    }
  ' "${2}"
  sed -i '
    /^\s*$/d
  ' "${2}"
  exit
fi

if [ $# -ne 0 ]; then
  >&2 echo 'usage error'
  >&2 printf '"%s" ' "$@"
  >&2 printf '\n'
  exit 1
fi

if ! mountpoint -q /mnt/archlinuxewe \
&& ! ls /mnt/archlinuxewe | grep -qF ''; then
  >&2 printf '/mnt/archlinuxewe is empty\n'
  exit 1
fi

tmp_dir=$(mktemp -d)
trap 'rm -rf --one-file-system "${tmp_dir}"' EXIT

find "$(pwd)" -maxdepth 2 -mindepth 2 -name 'PKGBUILD' -type f \
| sed -n '
  s@/[^/]\+$@@
  T
  s@/[^/]\+$@\0\n'"${tmp_dir%/}"'\0.srcinfo@
  T
  p
' \
| parallel -j0 -L2 "$0"

print_names() {
  if [ -z "${pkgname}" ] \
  || [ -z "${pkgver}" ] \
  || [ -z "${pkgrel}" ]; then
    >&2 echo 'error: some variable is missing'
    exit 1
  fi
  for arch in "${archs[@]}"; do
    printf '%s-%s%s-%s-%s.pkg.tar.xz\n' \
      "${pkgname}" \
      "${epoch:+${epoch}:}" \
      "${pkgver}" \
      "${pkgrel}" \
      "${arch}"
  done
}

diff -u --color <(
  find /mnt/archlinuxewe -type f -name '*.pkg.tar.xz' -printf '%f\n' \
  | sort -u
) <(
  find "$tmp_dir" -name '*.srcinfo' -exec cat {} + \
  | {
    while read key eq value; do
      if [ "x${eq}" != 'x=' ]; then
        >&2 echo "syntax error"
        exit 1
      fi
      case "${key}" in
        'pkgname')
          if [ -n "${pkgname}" ]; then
            print_names
          fi
          archs=()
          pkgname="${value}"
          unset epoch
          unset pkgver
          unset pkgrel
        ;;
        'arch')
          archs+=("${value}")
        ;;
        'epoch')
          epoch="${value}"
        ;;
        'pkgver')
          pkgver="${value}"
        ;;
        'pkgrel')
          pkgrel="${value}"
        ;;
        *)
          >&2 printf 'unknown key "%s"\n' "${key}"
          exit 1
        ;;
      esac
    done
    if [ -n "${pkgname}" ]; then
      print_names
    fi
  } \
  | sort -u
)