#!/usr/bin/env bash
#
# Generate Changelog
#
# Generates CHANGELOG.md from git commits since the last tagged release
# using git-cliff for deterministic, regex-based commit categorization.
#
# Usage:
#   ./bin/generate-changelog              # Write CHANGELOG.md and open in $EDITOR
#   ./bin/generate-changelog --dry-run    # Print to stdout only
#   ./bin/generate-changelog --from TAG   # Use a specific base tag
#

set -euo pipefail
cd "$(dirname "$0")/.."

dry_run=false
from_tag=""

while [[ $# -gt 0 ]]; do
    case "$1" in
        --dry-run)
            dry_run=true
            shift
            ;;
        --from)
            from_tag="$2"
            shift 2
            ;;
        -h|--help)
            echo "Usage: $0 [--dry-run] [--from TAG]"
            echo ""
            echo "  --dry-run    Print to stdout instead of writing file"
            echo "  --from TAG   Base tag (default: latest tag)"
            exit 0
            ;;
        *)
            echo "Unknown option: $1" >&2
            exit 1
            ;;
    esac
done

# Determine base tag
if [[ -z "$from_tag" ]]; then
    from_tag=$(git tag --sort=-creatordate | head -1)
    if [[ -z "$from_tag" ]]; then
        echo "Error: no git tags found" >&2
        exit 1
    fi
fi

# Build git-cliff arguments
cliff_args=(--config cliff.toml --unreleased "${from_tag}..HEAD")

if "$dry_run"; then
    git-cliff "${cliff_args[@]}"
else
    git-cliff "${cliff_args[@]}" --output CHANGELOG.md
    count=$(git log "${from_tag}..HEAD" --oneline | wc -l | tr -d ' ')
    echo "Wrote CHANGELOG.md (${count} commits from ${from_tag}..HEAD)"

    if [[ -n "${EDITOR:-}" ]]; then
        exec "$EDITOR" CHANGELOG.md
    fi
fi