#!/usr/bin/env bash
#=== HELP START ===
# generate-changelog.sh – generates a Debian-style changelog via git-cliff
#
# Usage:
#   ./generate-changelog.sh -c cliff.debian.toml -t v2.9.1 -o debian/changelog
#
# Options:
#   -c, --config <file>   Path to a valid git-cliff config file (required)
#   -t, --tag    <tag>    Git tag used as the starting point for the changelog (required)
#   -o, --out    <file>   Target changelog file to write to (required, unless --debug)
#   -d, --debug          Print changelog to stdout instead of writing the file
#   -h, --help           Show this help message
#
# Behaviour:
#   • Verifies git-cliff, sed, and git are installed.
#   • Checks that the config file exists and is readable.
#   • Ensures the parent directory of the output file exists (unless --debug).
#   • Generates the changelog; removes a leading empty line.
#=== HELP END ===
set -euo pipefail

# ───────────────────────────────────────────────
CONFIG_FILE=""
TAG=""
OUT_FILE=""
DEBUG=false
# ───────────────────────────────────────────────

show_help() {
  sed -n '/^#=== HELP START ===/,/^#=== HELP END ===/ {
    /^#=== HELP START ===/d
    /^#=== HELP END ===/d
    s/^#//
    p
  }' "$0"
}

# 1 Parse CLI options
while [[ $# -gt 0 ]]; do
  case "$1" in
    -c|--config) [[ $# -lt 2 ]] && { echo "❌ $1 requires a value"; exit 1; }; CONFIG_FILE="$2"; shift 2 ;;
    -t|--tag)    [[ $# -lt 2 ]] && { echo "❌ $1 requires a value"; exit 1; }; TAG="$2";         shift 2 ;;
    -o|--out)    [[ $# -lt 2 ]] && { echo "❌ $1 requires a value"; exit 1; }; OUT_FILE="$2";    shift 2 ;;
    -d|--debug)  DEBUG=true; shift ;;
    -h|--help)   show_help; exit 0 ;;
    *)           echo "❌ Unknown option: $1"; show_help; exit 1 ;;
  esac
done

# 2 Basic validation
[[ -z "$CONFIG_FILE" || -z "$TAG" ]] && { echo "❌ --config and --tag are required"; show_help; exit 1; }
[[ "$DEBUG" = false && -z "$OUT_FILE" ]] && { echo "❌ --out is required unless --debug is set"; show_help; exit 1; }
[[ ! -r "$CONFIG_FILE" ]] && { echo "❌ Config file not found or unreadable: $CONFIG_FILE"; exit 1; }
if [[ "$DEBUG" = false ]]; then
  OUT_DIR=$(dirname "$OUT_FILE")
  [[ ! -d "$OUT_DIR" ]] && { echo "❌ Output directory does not exist: $OUT_DIR"; exit 1; }
fi

# 3 Required tools
need() { command -v "$1" >/dev/null || { echo "❌ $1 is required but not installed"; exit 1; }; }
need git; need git-cliff; need sed

# 4 Generate changelog
if $DEBUG; then
  echo "📝 Generating changelog (debug mode – stdout only)"
  git cliff --config "$CONFIG_FILE" -t "$TAG" -s all
else
  echo "📝 Generating changelog → $OUT_FILE"
  git cliff --config "$CONFIG_FILE" -t "$TAG" -s all > "$OUT_FILE"
  echo "✅ Changelog written to $OUT_FILE"
fi