name: Sync fork with upstream

on:
  schedule:
    # Daily at 03:00 UTC
    - cron: "0 3 * * *"
  workflow_dispatch:

permissions:
  contents: write

jobs:
  sync:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout fork default branch
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Sync from upstream
        env:
          # IMPORTANT: change this to the original source repository
          UPSTREAM_REPO: "ORIGINAL_OWNER/ORIGINAL_REPO"
          # Optional: set your branch explicitly if not default branch behavior
          TARGET_BRANCH: "main"
        run: |
          set -euo pipefail

          git config user.name "github-actions[bot]"
          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"

          # Ensure we're on target branch
          git checkout "${TARGET_BRANCH}"

          # Add/update upstream remote
          if git remote get-url upstream >/dev/null 2>&1; then
            git remote set-url upstream "https://github.com/${UPSTREAM_REPO}.git"
          else
            git remote add upstream "https://github.com/${UPSTREAM_REPO}.git"
          fi

          # Fetch and fast-forward only
          git fetch upstream
          git merge --ff-only "upstream/${TARGET_BRANCH}" || {
            echo "Fast-forward failed (diverged history). Manual intervention required."
            exit 1
          }

          # Push only if branch moved
          git push origin "${TARGET_BRANCH}"