#!/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
#
# 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'}"

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=$(git describe --tags --abbrev=0 --match="$TAG_PATTERN" HEAD^ 2>/dev/null || echo "")

if [ -n "$PREV_TAG" ]; then
  RAW=$(git 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"