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

BASE_BRANCH="${1:-main}"

if ! git rev-parse --is-inside-work-tree >/dev/null 2>&1; then
  echo "Not a git repository"
  exit 1
fi

CURRENT_BRANCH=$(git rev-parse --abbrev-ref HEAD)
if [ "$CURRENT_BRANCH" = "HEAD" ]; then
  echo "Detached HEAD is not supported by this script"
  exit 1
fi

if [ "$CURRENT_BRANCH" = "$BASE_BRANCH" ]; then
  echo "Refusing to run on base branch: $BASE_BRANCH"
  echo "Please switch to a feature/fix branch first."
  exit 1
fi

if [ -n "$(git status --porcelain)" ]; then
  STASH_NAME="$(date +%F)-${CURRENT_BRANCH}-safe-sync"
  echo "Working tree is dirty, stashing as: ${STASH_NAME}"
  git stash push -u -m "$STASH_NAME" >/dev/null
  STASHED=1
else
  STASHED=0
fi

echo "Fetching latest refs..."
git fetch origin --prune

echo "Rebasing ${CURRENT_BRANCH} onto origin/${BASE_BRANCH}..."
git rebase "origin/${BASE_BRANCH}"

if [ "$STASHED" -eq 1 ]; then
  echo "Restoring stashed changes..."
  git stash pop || {
    echo "stash pop has conflicts; resolve manually, then continue."
    exit 2
  }
fi

echo "Safe sync done."