name: Sync main to develop

on:
  push:
    branches: [main]
  workflow_dispatch:

permissions:
  contents: write
  pull-requests: write

jobs:
  check:
    runs-on: ubuntu-latest
    name: Check if sync is needed
    outputs:
      skip: ${{ steps.check-sync.outputs.SKIP }}
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          ref: main
          fetch-depth: 0
      - name: Check if sync is needed
        id: check-sync
        run: |
          # Use merge-tree to check if merging main into develop would produce
          # any content changes, without touching the working tree. This correctly
          # handles cherry-picks where the SHAs differ but the content is identical.
          if MERGE_TREE=$(git merge-tree --write-tree origin/develop origin/main 2>&1); then
            DEVELOP_TREE=$(git rev-parse origin/develop^{tree})
            echo "Merge result tree: $MERGE_TREE"
            echo "Develop tree:      $DEVELOP_TREE"
            if [ "$MERGE_TREE" = "$DEVELOP_TREE" ]; then
              echo "Merge would not change develop. Skipping sync."
              echo "SKIP=true" >> "$GITHUB_OUTPUT"
            else
              echo "Merge would introduce changes. Sync needed."
              echo "SKIP=false" >> "$GITHUB_OUTPUT"
            fi
          else
            echo "Merge would have conflicts. Sync needed."
            echo "SKIP=false" >> "$GITHUB_OUTPUT"
          fi

  sync:
    needs: check
    if: needs.check.outputs.skip != 'true'
    runs-on: ubuntu-latest
    name: Sync main to develop
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          ref: main
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}
      - name: Set up git user
        run: |
          git config user.name "RobotMCP Bot"
          git config user.email "admin@robotmcp.ai"
      - name: Create syncing branch off of main
        id: create-sync-branch
        run: |
          SYNC_BRANCH="main-$(git rev-parse --short HEAD)/sync"
          echo "Creating syncing branch: $SYNC_BRANCH"
          git switch --create "$SYNC_BRANCH"
          git push origin "$SYNC_BRANCH"
          echo "SYNC_BRANCH=$SYNC_BRANCH" >> "$GITHUB_OUTPUT"
      - name: Create syncing PR
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          SYNC_BRANCH: ${{ steps.create-sync-branch.outputs.SYNC_BRANCH }}
        run: |
          gh pr create \
            --base develop \
            --head "$SYNC_BRANCH" \
            --title "chore: sync main to develop" \
            --draft \
            --body "Auto-syncing 'main' to 'develop'

          If this PR does not merge automatically, there are conflicts between 'main' and 'develop'.

          **Do not merge this PR through GitHub.** A maintainer should:

          1. Pull this temporary syncing branch locally:
             \`\`\`
             git fetch origin
             git checkout $SYNC_BRANCH
             \`\`\`

          2. Merge 'develop' into this branch and resolve conflicts:
             \`\`\`
             git merge origin/develop
             # resolve any conflicts, then commit
             \`\`\`

          3. Push the resolved branch:
             \`\`\`
             git push origin $SYNC_BRANCH
             \`\`\`

          4. Run the 'Merge branch into target' workflow from this branch with target branch 'develop'

          5. After the workflow completes, this PR will close automatically"
      - name: Merge and push to develop
        run: |
          git switch develop
          git merge --no-ff --no-edit --commit --message "chore: sync main to develop" "${{ steps.create-sync-branch.outputs.SYNC_BRANCH }}"
          git push origin develop
      - name: Cleanup sync branch
        continue-on-error: true
        env:
          SYNC_BRANCH: ${{ steps.create-sync-branch.outputs.SYNC_BRANCH }}
        run: git push origin :"$SYNC_BRANCH"