#!/usr/bin/env bash
#
# Cut a release: bump the version, generate a CHANGELOG entry from the commits
# since the last tag, commit, tag, and push.
#
#   scripts/release.sh patch|minor|major
#
set -euo pipefail

part="${1:-}"
case "$part" in
  patch | minor | major) ;;
  *)
    echo "usage: $0 patch|minor|major" >&2
    exit 1
    ;;
esac

cd "$(git rev-parse --show-toplevel)"

if ! git diff --quiet || ! git diff --cached --quiet; then
  echo "working tree is not clean; commit or stash first" >&2
  exit 1
fi

branch="$(git symbolic-ref --short HEAD)"
if [ "$branch" != "main" ]; then
  echo "not on main (on $branch)" >&2
  exit 1
fi

current="$(git tag --list 'v*' --sort=-v:refname | head -n1)"
current="${current:-v0.0.0}"
IFS=. read -r major minor patch <<<"${current#v}"

case "$part" in
  major) major=$((major + 1)); minor=0; patch=0 ;;
  minor) minor=$((minor + 1)); patch=0 ;;
  patch) patch=$((patch + 1)) ;;
esac
next="v$major.$minor.$patch"

date="$(date +%Y-%m-%d)"

if grep -qiE '^## +unreleased *$' CHANGELOG.md; then
  # Promote the hand-written "## Unreleased" section to this version.
  awk -v repl="## $next - $date" '
    !done && tolower($0) ~ /^## +unreleased *$/ { print repl; done = 1; next }
    { print }
  ' CHANGELOG.md >CHANGELOG.tmp && mv CHANGELOG.tmp CHANGELOG.md
else
  # No curated section: fall back to a list of commit subjects since the tag.
  range=""
  [ "$current" != "v0.0.0" ] && range="$current..HEAD"
  notes="$(git log --no-merges --pretty='- %s' $range)"
  notes="${notes:-- (no changes)}"

  head_part="$(sed '/^## /,$d' CHANGELOG.md)"
  rest_part="$(sed -n '/^## /,$p' CHANGELOG.md)"
  {
    printf '%s\n' "$head_part"
    printf '\n## %s - %s\n\n%s\n\n' "$next" "$date" "$notes"
    printf '%s\n' "$rest_part"
  } >CHANGELOG.md
fi

git commit -aqm "Release $next"
git tag -a "$next" -m "$next"
git push -q origin "$branch" "$next"

echo "released $next"