#!/bin/sh
set -eu

# Fragment names are matched with ASCII ranges, so keep collation deterministic.
LC_ALL=C
export LC_ALL

CHANGES_DIR="${1:-.changes}"

usage() {
  printf '%s\n' 'usage: render-release-fragments.sh [changes-dir]' >&2
}

[ "$#" -le 1 ] || { usage; exit 2; }
[ -d "$CHANGES_DIR" ] || { printf 'release fragments directory not found: %s\n' "$CHANGES_DIR" >&2; exit 1; }

tmp_root="$(mktemp -d "${TMPDIR:-/tmp}/dws-release-fragments.XXXXXX")"
cleanup() { rm -rf "$tmp_root"; }
trap cleanup EXIT HUP INT TERM

# A fragment must be a regular file named ^[a-z0-9][a-z0-9._-]*\.md$. Anything
# else is rejected rather than skipped, so a symlink or an illegally named
# fragment can never be silently dropped from the rendered notes.
validate_fragment_name() {
  name="$1"
  path="$2"
  case "$name" in
    *.md) ;;
    *) printf 'invalid release fragment filename: %s\n' "$path" >&2; return 1 ;;
  esac
  case "$name" in
    [a-z0-9]*) ;;
    *) printf 'invalid release fragment filename: %s\n' "$path" >&2; return 1 ;;
  esac
  case "$name" in
    *[!a-z0-9._-]*) printf 'invalid release fragment filename: %s\n' "$path" >&2; return 1 ;;
  esac
}

find "$CHANGES_DIR" -mindepth 1 -maxdepth 1 -print | sort >"$tmp_root/entries"

: >"$tmp_root/files"
while IFS= read -r entry; do
  base="${entry##*/}"
  if [ "$base" = 'README.md' ]; then
    continue
  fi
  if [ -L "$entry" ]; then
    printf 'release fragment must be a regular file, not a symbolic link: %s\n' "$entry" >&2
    exit 1
  fi
  if [ -d "$entry" ]; then
    if [ "$base" = 'released' ]; then
      continue
    fi
    printf 'unexpected directory in release fragments directory: %s\n' "$entry" >&2
    exit 1
  fi
  if [ ! -f "$entry" ]; then
    printf 'release fragment must be a regular file: %s\n' "$entry" >&2
    exit 1
  fi
  validate_fragment_name "$base" "$entry"
  printf '%s\n' "$entry" >>"$tmp_root/files"
done <"$tmp_root/entries"

[ -s "$tmp_root/files" ] || {
  printf '%s\n' 'no release fragments found; add .changes/<unique-name>.md before preparing a prerelease changelog' >&2
  exit 1
}

validate_fragment() {
  fragment="$1"
  validate_fragment_name "${fragment##*/}" "$fragment"

  [ "$(sed -n '1p' "$fragment")" = '---' ] &&
    [ "$(sed -n '3p' "$fragment")" = '---' ] || {
      printf 'invalid release fragment header: %s\n' "$fragment" >&2
      return 1
    }
  case "$(sed -n '2p' "$fragment")" in
    'category: Added'|'category: Changed'|'category: Deprecated'|'category: Removed'|'category: Fixed'|'category: Security') ;;
    *) printf 'invalid release fragment category: %s\n' "$fragment" >&2; return 1 ;;
  esac

  body="$(sed -n '4,$p' "$fragment")"
  printf '%s\n' "$body" | grep -Eq '^- [^[:space:]].*' || {
    printf 'release fragment must contain a non-empty Markdown list item: %s\n' "$fragment" >&2
    return 1
  }
  if printf '%s\n' "$body" | grep -Eqi '(^|[^[:alnum:]_])(TODO|TBD)([^[:alnum:]_]|$)'; then
    printf 'release fragment must not contain TODO/TBD: %s\n' "$fragment" >&2
    return 1
  fi
}

while IFS= read -r fragment; do
  validate_fragment "$fragment"
done <"$tmp_root/files"

for category in Added Changed Deprecated Removed Fixed Security; do
  category_files="$tmp_root/$category"
  : >"$category_files"
  while IFS= read -r fragment; do
    if [ "$(sed -n '2p' "$fragment")" = "category: $category" ]; then
      printf '%s\n' "$fragment" >>"$category_files"
    fi
  done <"$tmp_root/files"
  [ -s "$category_files" ] || continue

  printf '### %s\n\n' "$category"
  while IFS= read -r fragment; do
    awk 'NR >= 4 { if ($0 ~ /[^[:space:]]/) started = 1; if (started) print }' "$fragment"
    printf '\n'
  done <"$category_files"
done