#!/bin/bash
# Generate release notes from commits since the previous tag.

set -euo pipefail

CURRENT_TAG="${1:-${DRONE_TAG:-}}"
OUTPUT_FILE="${2:-.build/release-notes.md}"

if [ -z "$CURRENT_TAG" ]; then
    echo "Error: current tag not provided"
    exit 1
fi

# In CI, the tag name may be available but not present as a local ref.
CURRENT_REF="$CURRENT_TAG"
if ! git rev-parse --verify -q "${CURRENT_REF}^{commit}" >/dev/null; then
    CURRENT_REF="${DRONE_COMMIT:-HEAD}"
fi

PREVIOUS_TAG=$(git describe --tags --abbrev=0 "${CURRENT_REF}^" 2>/dev/null || echo "")

mkdir -p "$(dirname "$OUTPUT_FILE")"

{
    echo "# Release $CURRENT_TAG"
    echo

    if [ -n "$PREVIOUS_TAG" ]; then
        echo "Changes since $PREVIOUS_TAG:"
        echo

        git log "$PREVIOUS_TAG..$CURRENT_REF" --pretty=format:"%s" | while read -r commit; do
            if [[ $commit =~ ^([a-z]+)(\(.+\))?:\ (.+)$ ]]; then
                TYPE="${BASH_REMATCH[1]}"
                SCOPE="${BASH_REMATCH[2]}"
                MESSAGE="${BASH_REMATCH[3]}"

                case "$TYPE" in
                    feat)
                        echo "- Feature${SCOPE}: $MESSAGE" ;;
                    fix)
                        echo "- Fix${SCOPE}: $MESSAGE" ;;
                    docs)
                        echo "- Docs${SCOPE}: $MESSAGE" ;;
                    ci)
                        echo "- CI${SCOPE}: $MESSAGE" ;;
                    test)
                        echo "- Test${SCOPE}: $MESSAGE" ;;
                    refactor)
                        echo "- Refactor${SCOPE}: $MESSAGE" ;;
                    perf)
                        echo "- Performance${SCOPE}: $MESSAGE" ;;
                    *)
                        echo "- $commit" ;;
                esac
            else
                echo "- $commit"
            fi
        done
    else
        echo "Initial release"
        echo
        git log "$CURRENT_REF" --pretty=format:"- %s" | head -20
    fi

    echo
    echo "---"
    if [ -n "$PREVIOUS_TAG" ]; then
        echo "See all changes: https://scm.yoorie.de/git/go-lib/micro/compare/$PREVIOUS_TAG...$CURRENT_TAG"
    else
        echo "See all changes: https://scm.yoorie.de/git/go-lib/micro/releases/tag/$CURRENT_TAG"
    fi
} > "$OUTPUT_FILE"

echo "Release notes generated: $OUTPUT_FILE"
cat "$OUTPUT_FILE"