#!/bin/bash
# Generate an rpm %changelog entry for this release and prepend it to
# the spec's existing %changelog section.
#
# Usage: generate-rpm-changelog.sh <spec-file> <version>
#
# Environment overrides:
#   CHANGELOG_AUTHOR  — "Name <email>", default "Gitea Actions <actions@git.lair.cafe>"
#   RELEASE           — release suffix, default "1"
#   TAG_PATTERN       — glob for release tags, default "v*"
#   EXCLUDE_PATTERNS  — newline-separated grep -E patterns to drop
#   SOURCE_DIR        — path to an external git checkout to read history from
#   REPO_URL          — URL of a remote repo to clone (bare) for history
#
# If SOURCE_DIR or REPO_URL is set, commits are collected from that
# repository instead of the current working directory. SOURCE_DIR
# takes precedence over REPO_URL.
#
# Collects commits since the previous matching tag, drops filtered
# lines (bump-version chore commits, merges, etc.), and writes a
# dated entry.

set -euo pipefail

SPEC="$1"
VERSION="$2"
AUTHOR="${CHANGELOG_AUTHOR:-Gitea Actions <actions@git.lair.cafe>}"
RELEASE="${RELEASE:-1}"
TAG_PATTERN="${TAG_PATTERN:-v*}"
EXCLUDE_PATTERNS="${EXCLUDE_PATTERNS:-$'^- chore: bump version\n^- Merge'}"
SOURCE_DIR="${SOURCE_DIR:-}"
REPO_URL="${REPO_URL:-}"

# Resolve the git directory to collect commits from.
# Priority: SOURCE_DIR > REPO_URL > current working directory.
CLEANUP_DIR=""
GIT_ARGS=()

if [ -n "$SOURCE_DIR" ]; then
  if [ ! -d "$SOURCE_DIR/.git" ] && ! git -C "$SOURCE_DIR" rev-parse --git-dir >/dev/null 2>&1; then
    printf 'error: source-dir is not a git repository: %s\n' "$SOURCE_DIR" >&2
    exit 1
  fi
  GIT_ARGS=(-C "$SOURCE_DIR")
  printf 'Using source-dir for commit history: %s\n' "$SOURCE_DIR"
elif [ -n "$REPO_URL" ]; then
  CLONE_DIR=$(mktemp -d)
  CLEANUP_DIR="$CLONE_DIR"
  printf 'Cloning %s (bare) for commit history…\n' "$REPO_URL"
  git clone --bare --filter=blob:none "$REPO_URL" "$CLONE_DIR/repo.git"
  GIT_ARGS=(-C "$CLONE_DIR/repo.git")
fi

cleanup() {
  if [ -n "$CLEANUP_DIR" ] && [ -d "$CLEANUP_DIR" ]; then
    rm -rf "$CLEANUP_DIR"
  fi
}
trap cleanup EXIT

if [ ! -f "$SPEC" ]; then
  echo "error: spec file not found: $SPEC" >&2
  exit 1
fi

if ! grep -q '^%changelog' "$SPEC"; then
  echo "error: no %changelog section in $SPEC — refusing to mangle" >&2
  exit 1
fi

# Find the previous release tag (exclude the current tag at HEAD).
PREV_TAG=$(git "${GIT_ARGS[@]}" describe --tags --abbrev=0 --match="$TAG_PATTERN" HEAD^ 2>/dev/null || echo "")

if [ -n "$PREV_TAG" ]; then
  RAW=$(git "${GIT_ARGS[@]}" log --no-merges --pretty=format:'- %s' "${PREV_TAG}..HEAD")

  # Build a combined grep -E pattern from the exclude list; drop blanks.
  COMBINED=""
  while IFS= read -r pat; do
    [ -z "$pat" ] && continue
    if [ -z "$COMBINED" ]; then
      COMBINED="$pat"
    else
      COMBINED="${COMBINED}|${pat}"
    fi
  done <<< "$EXCLUDE_PATTERNS"

  if [ -n "$COMBINED" ]; then
    LOG=$(printf '%s\n' "$RAW" | grep -Ev "$COMBINED" || true)
  else
    LOG="$RAW"
  fi
else
  LOG=""
fi

if [ -z "$LOG" ]; then
  LOG="- No user-visible changes"
fi

DATE=$(LC_ALL=C date -u +'%a %b %d %Y')
ENTRY="* ${DATE} ${AUTHOR} - ${VERSION}-${RELEASE}
${LOG}
"

# Prepend the entry to the %changelog section.
TMP=$(mktemp)
awk -v entry="$ENTRY" '
  inserted == 0 && /^%changelog[[:space:]]*$/ {
    print
    print entry
    inserted = 1
    next
  }
  { print }
' "$SPEC" > "$TMP"

mv "$TMP" "$SPEC"

echo "Added changelog entry for ${VERSION}-${RELEASE}:"
echo "$ENTRY"