name: Upstream Sync

on:
  schedule:
    - cron: '0 0 1 * *'
  workflow_dispatch:

permissions:
  contents: write
  pull-requests: write

jobs:
  sync-upstream:
    runs-on: ubuntu-latest
    env:
      UPSTREAM: "https://github.com/bitcoin-core/secp256k1.git" 
      UPSTREAM_BRANCH: "master"
      ORIGIN_BRANCH: "master"
      MIN_UPSTREAM_MERGES: 1
    
    steps:
      - name: Checkout repository
        uses: actions/checkout@v6
        with:
          fetch-depth: 0
          token: ${{ secrets.SYNC_PAT }}

      - name: Configure Git
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"

      - name: Fetch upstream & generate branch name & check for new commits
        id: check_commits
        env:
          GH_TOKEN: ${{ secrets.SYNC_PAT }}
        run: |
          gh repo set-default ${{ github.repository }}  # Set the default repo to the origin repository
          git remote add upstream ${{ env.UPSTREAM }}
          git fetch upstream
          
          MERGES=$(git rev-list --count --merges HEAD..upstream/${{ env.UPSTREAM_BRANCH }})
          echo "Found $MERGES new merge commits in upstream."
          
          if [ "$MERGES" -lt ${{ env.MIN_UPSTREAM_MERGES }} ]; then
            echo "Exiting."
            echo "skip=true" >> "$GITHUB_OUTPUT"
          else
            echo "skip=false" >> "$GITHUB_OUTPUT"
          fi
          
          # Generate a sync branch name "sync-UPSTREAM_HEAD", where UPSTREAM_HEAD is a commit ID.
          UPSTREAM_HEAD=$(git rev-parse --short upstream/${{ env.UPSTREAM_BRANCH }})
          SYNC_BRANCH="sync-$UPSTREAM_HEAD"
          echo "Sync branch name: $SYNC_BRANCH"
          echo "SYNC_BRANCH=$SYNC_BRANCH" >> "$GITHUB_ENV"

          # Check if the sync branch already exists in the origin repository
          if git ls-remote --heads origin "$SYNC_BRANCH" | grep -q "$SYNC_BRANCH"; then
            echo "Branch $SYNC_BRANCH already exists. Skipping the sync."
            echo "skip=true" >> "$GITHUB_OUTPUT"
          else
            echo "skip=false" >> "$GITHUB_OUTPUT"
          fi

      - name: Generate PR metadata
        id: branch_pr_metadata
        if: steps.check_commits.outputs.skip == 'false'
        run: |
          # Call the sync script to generate PR title and body
          ./contrib/sync-upstream.sh -b ${{ env.ORIGIN_BRANCH }} "$SYNC_BRANCH"

      - name: Push a sync branch
        id: push_branch
        if: steps.check_commits.outputs.skip == 'false'
        run: |
          echo "Creating sync branch: $SYNC_BRANCH"
          git checkout upstream/${{ env.UPSTREAM_BRANCH }}
          git checkout -b "$SYNC_BRANCH"
          git push -u origin "$SYNC_BRANCH"

      - name: Create pull request
        id: create_pr
        if: steps.check_commits.outputs.skip == 'false'
        env:
          GH_TOKEN: ${{ secrets.SYNC_PAT }}
        run: |
          # Execute the generated PR creation script
          ./contrib/gh-pr-create.sh 

      - name: Cleanup sync branch on failure
        if: steps.push_branch.outcome == 'success' && steps.create_pr.outcome == 'failure'
        run: |
          echo "PR creation failed but branch was pushed. Deleting: $SYNC_BRANCH"
          git push origin --delete "$SYNC_BRANCH"