#!/bin/bash
# Generate changelog from git history for CI releases
# Groups commits by conventional commit types
#
# Expected environment variables:
#   INPUT_TAG            - Git tag to generate changelog for (required)
#   INPUT_PREVIOUS_TAG   - Previous tag override (optional, auto-detected)
#   INPUT_CATEGORIES     - JSON mapping of prefixes to headers (optional)
#   GITHUB_OUTPUT        - Output file for action outputs (set by runner)
#   GITEA_SERVER_URL     - Forgejo server URL (set by runner)
#   GITEA_REPOSITORY     - Repository in owner/repo format (set by runner)

set -euo pipefail

TAG="${INPUT_TAG:?Error: tag input is required}"
PREV_TAG="${INPUT_PREVIOUS_TAG:-}"
CATEGORIES="${INPUT_CATEGORIES:-}"

# Default categories if not provided or empty
if [ -z "$CATEGORIES" ]; then
  CATEGORIES='{"feat": "✨ Features", "fix": "🐛 Bug Fixes", "refactor": "♻️ Refactoring", "chore": "🔧 Chores"}'
fi

echo "Generating changelog for ${TAG}..."

# Determine previous tag
if [ -z "$PREV_TAG" ]; then
  PREV_TAG=$(git describe --tags --abbrev=0 "${TAG}^" 2>/dev/null || echo "")
fi

if [ -z "$PREV_TAG" ]; then
  echo "No previous tag found. This is the first release."
  COMMIT_RANGE="${TAG}"
else
  echo "Generating changelog from ${PREV_TAG} to ${TAG}"
  COMMIT_RANGE="${PREV_TAG}..${TAG}"
fi

# Parse category prefixes and headers from JSON using jq if available, else fallback
parse_categories() {
  if command -v jq &>/dev/null; then
    jq -r 'to_entries[] | "\(.key)|\(.value)"' <<< "$CATEGORIES"
  else
    # Pure bash fallback: parse simple flat JSON {"key": "value", ...}
    local json="${CATEGORIES//\{/}"
    json="${json//\}/}"
    local IFS=','
    for pair in $json; do
      local key value
      key=$(echo "$pair" | sed 's/.*"\([^"]*\)"\s*:.*/\1/')
      value=$(echo "$pair" | sed 's/.*:\s*"\([^"]*\)".*/\1/')
      echo "${key}|${value}"
    done
  fi
}

# Read categories into arrays
CATEGORY_PREFIXES=()
CATEGORY_HEADERS=()
while IFS='|' read -r prefix header; do
  [ -z "$prefix" ] && continue
  CATEGORY_PREFIXES+=("$prefix")
  CATEGORY_HEADERS+=("$header")
done < <(parse_categories)

NUM_CATEGORIES=${#CATEGORY_PREFIXES[@]}

# Initialize arrays to hold commits per category (+ 1 for "other")
declare -a CATEGORY_COMMITS
for ((i = 0; i <= NUM_CATEGORIES; i++)); do
  CATEGORY_COMMITS[$i]=""
done

# Get all commits in range
COMMITS=$(git log "${COMMIT_RANGE}" --pretty=format:"%H|%s" 2>/dev/null || echo "")

if [ -n "$COMMITS" ]; then
  while IFS='|' read -r hash message; do
    [ -z "$hash" ] && continue

    matched=false
    for ((i = 0; i < NUM_CATEGORIES; i++)); do
      prefix="${CATEGORY_PREFIXES[$i]}"
      # Match "prefix: msg" or "prefix(scope): msg"
      if [[ "$message" == "${prefix}:"* ]] || [[ "$message" == "${prefix}("* ]]; then
        # Strip prefix from message
        clean_msg="${message#"${prefix}"}"
        # Strip optional (scope): prefix
        if [[ "$clean_msg" == "("* ]]; then
          clean_msg="${clean_msg#*): }"
          clean_msg="${clean_msg#*):}"
        else
          clean_msg="${clean_msg#: }"
          clean_msg="${clean_msg#:}"
        fi
        CATEGORY_COMMITS[$i]+="- ${clean_msg} (${hash:0:7})"$'\n'
        matched=true
        break
      fi
    done

    if [ "$matched" = false ]; then
      CATEGORY_COMMITS[$NUM_CATEGORIES]+="- ${message} (${hash:0:7})"$'\n'
    fi
  done <<< "$COMMITS"
fi

# Build changelog
CHANGELOG="# Release ${TAG}"$'\n'$'\n'

if [ -z "$PREV_TAG" ] && [ -z "$INPUT_PREVIOUS_TAG" ]; then
  CHANGELOG+="First release! 🎉"$'\n'$'\n'
fi

if [ -z "$COMMITS" ]; then
  CHANGELOG+="No commits found in range"$'\n'
else
  # Write categorized sections
  for ((i = 0; i < NUM_CATEGORIES; i++)); do
    if [ -n "${CATEGORY_COMMITS[$i]}" ]; then
      CHANGELOG+="## ${CATEGORY_HEADERS[$i]}"$'\n'$'\n'
      CHANGELOG+="${CATEGORY_COMMITS[$i]}"$'\n'
    fi
  done

  # Other changes
  if [ -n "${CATEGORY_COMMITS[$NUM_CATEGORIES]}" ]; then
    CHANGELOG+="## 📝 Other Changes"$'\n'$'\n'
    CHANGELOG+="${CATEGORY_COMMITS[$NUM_CATEGORIES]}"$'\n'
  fi
fi

CHANGELOG+="---"$'\n'

# Add compare link using Forgejo env vars
if [ -n "${GITEA_SERVER_URL:-}" ] && [ -n "${GITEA_REPOSITORY:-}" ]; then
  COMPARE_BASE="${PREV_TAG:-$(git rev-list --max-parents=0 HEAD | head -1)}"
  CHANGELOG+="**Full Changelog**: ${GITEA_SERVER_URL}/${GITEA_REPOSITORY}/compare/${COMPARE_BASE}...${TAG}"$'\n'
elif [ -n "$PREV_TAG" ]; then
  CHANGELOG+="**Commits**: \`git log ${PREV_TAG}..${TAG}\`"$'\n'
else
  CHANGELOG+="**First Release**"$'\n'
fi

echo ""
echo "=== Generated Changelog ==="
echo "$CHANGELOG"
echo "==========================="

# Write to GITHUB_OUTPUT using multiline delimiter
if [ -n "${GITHUB_OUTPUT:-}" ]; then
  {
    echo "changelog<<CHANGELOG_EOF"
    echo "$CHANGELOG"
    echo "CHANGELOG_EOF"
  } >> "$GITHUB_OUTPUT"
fi