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

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

VERSION="${1:-}"
SUMMARY="${2:-}"
PREV_TAG="${3:-}"
DATE="${4:-$(date -u +%Y-%m-%d)}"
CHANGELOG="CHANGELOG.md"

if [[ -z "$VERSION" ]]; then
  echo "Usage: update-changelog.sh <version> <summary> <prev-tag> [date]" >&2
  exit 1
fi

if [[ -f "$CHANGELOG" ]] && grep -qF "## [${VERSION}]" "$CHANGELOG"; then
  echo "CHANGELOG already contains version ${VERSION}; skipping." >&2
  exit 0
fi

if [[ -n "$SUMMARY" ]]; then
  SUMMARY_TEXT=$(strip_bump_prefix "$SUMMARY")
else
  SUMMARY_TEXT="Automated release v${VERSION}."
fi

COMMITS=$(commits_since "$PREV_TAG")
SECTION=$(changelog_section "$VERSION" "$DATE" "$SUMMARY_TEXT" "$COMMITS")

if [[ ! -f "$CHANGELOG" ]]; then
  changelog_header > "$CHANGELOG"
  printf '\n%s\n' "$SECTION" >> "$CHANGELOG"
else
  UNRELEASED_MARKER='## [Unreleased]'
  if ! grep -qF "$UNRELEASED_MARKER" "$CHANGELOG"; then
    echo "CHANGELOG.md exists but is missing ${UNRELEASED_MARKER}" >&2
    exit 1
  fi

  TMP=$(mktemp)
  SECTION_FILE=$(mktemp)
  printf '%s\n' "$SECTION" > "$SECTION_FILE"

  awk -v section_file="$SECTION_FILE" '
    /^## \[Unreleased\]/ {
      print
      print ""
      while ((getline line < section_file) > 0) {
        print line
      }
      close(section_file)
      next
    }
    { print }
  ' "$CHANGELOG" > "$TMP"
  rm -f "$SECTION_FILE"
  mv "$TMP" "$CHANGELOG"
fi

echo "Updated ${CHANGELOG} with version ${VERSION}." >&2