#!/usr/bin/env bash
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
# shellcheck source=common.sh
source "${SCRIPT_DIR}/common.sh"

CHANGELOG="CHANGELOG.md"

# Best-effort summary for historical releases without stored PR titles.
summary_for_range() {
  local from_ref="$1"
  local to_ref="$2"
  local subject

  while IFS= read -r subject; do
    [[ -z "$subject" ]] && continue
    if echo "$subject" | grep -qE '^chore: release v'; then
      continue
    fi
    if echo "$subject" | grep -qE "^Merge pull request '"; then
      local title
      title=$(extract_pr_title_from_merge_commit "$subject")
      if [[ -n "$title" ]]; then
        strip_bump_prefix "$title"
        return 0
      fi
    fi
    echo "$subject"
    return 0
  done < <(git log "${from_ref}..${to_ref}" --pretty=format:'%s' 2>/dev/null || true)

  echo "Release ${to_ref}"
}

TAGS=()
while IFS= read -r tag; do
  TAGS+=("$tag")
done < <(git tag -l 'v*' --sort=version:refname)
if [[ ${#TAGS[@]} -eq 0 ]]; then
  echo "No version tags found." >&2
  exit 1
fi

changelog_header > "$CHANGELOG"

for ((i = ${#TAGS[@]} - 1; i >= 0; i--)); do
  TAG="${TAGS[$i]}"
  VERSION="${TAG#v}"
  DATE=$(git log -1 --format=%cs "$TAG" 2>/dev/null || date -u +%Y-%m-%d)

  if [[ $i -eq 0 ]]; then
    PREV_TAG=""
  else
    PREV_TAG="${TAGS[$((i - 1))]}"
  fi

  SUMMARY=$(summary_for_range "$PREV_TAG" "$TAG")
  COMMITS=$(commits_between "$PREV_TAG" "$TAG")
  SECTION=$(changelog_section "$VERSION" "$DATE" "$SUMMARY" "$COMMITS")
  printf '\n%s\n' "$SECTION" >> "$CHANGELOG"
done

echo "Generated ${CHANGELOG} from ${#TAGS[@]} tags." >&2