#!/usr/bin/env bash
set -euo pipefail

ROOT="$(cd "$(dirname "$0")/.." && pwd)"
BASE_REF="${BASE_REF:-}"
SKIP_FETCH=0

usage() {
  cat <<'EOF'
Usage:
  bash scripts/check-branch-baseline.sh [--skip-fetch]

Checks that the current branch is not behind origin/main.

Environment:
  BASE_REF     Base ref to compare against. Defaults to origin/main when available.
EOF
}

while [[ $# -gt 0 ]]; do
  case "$1" in
    --skip-fetch) SKIP_FETCH=1 ;;
    -h|--help)
      usage
      exit 0
      ;;
    *)
      echo "Unknown argument: $1" >&2
      usage >&2
      exit 1
      ;;
  esac
  shift
done

git -C "${ROOT}" rev-parse --is-inside-work-tree >/dev/null

if [[ "${SKIP_FETCH}" -ne 1 ]] && git -C "${ROOT}" remote get-url origin >/dev/null 2>&1; then
  git -C "${ROOT}" fetch origin --prune
fi

if [[ -z "${BASE_REF}" ]]; then
  for candidate in origin/main origin/master main master; do
    if git -C "${ROOT}" rev-parse --verify --quiet "${candidate}" >/dev/null; then
      BASE_REF="${candidate}"
      break
    fi
  done
fi

branch="$(git -C "${ROOT}" branch --show-current)"
if [[ -z "${branch}" ]]; then
  echo "Baseline check failed: detached HEAD is not allowed for development or release." >&2
  exit 1
fi

if ! git -C "${ROOT}" rev-parse --verify --quiet "${BASE_REF}" >/dev/null; then
  echo "Baseline check failed: base ref not found: ${BASE_REF}" >&2
  exit 1
fi

read -r ahead behind < <(git -C "${ROOT}" rev-list --left-right --count "HEAD...${BASE_REF}")

if [[ "${behind}" -ne 0 ]]; then
  echo "Baseline check failed: ${branch} is behind ${BASE_REF} by ${behind} commit(s)." >&2
  echo "Run: git fetch origin --prune && git rebase ${BASE_REF}" >&2
  exit 1
fi

echo "Baseline check passed: ${branch} is current with ${BASE_REF} (ahead ${ahead})."