name: backport
on:
  pull_request_target:
    branches:
      - main
    types:
      - opened
      - reopened
      - unlabeled
      - labeled
      - closed
      - ready_for_review

jobs:
  get-branches:
    uses: ./.github/workflows/get-target-branches.yml

  label:
    runs-on: ubuntu-latest
    if: |
      github.event.pull_request.state == 'open' && !github.event.pull_request.draft
    steps:
      - name: 'Apply default "backport: auto" label'
        uses: actions/github-script@v4
        if: |
          !contains(github.event.pull_request.labels.*.name, 'backport: auto') &&
          !contains(github.event.pull_request.labels.*.name, 'backport: skip')
        with:
          script: |
            github.issues.addLabels({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              labels: ['backport: auto']
            })
      - name: 'Remove "backport: auto" if "backport: skip" is set'
        uses: actions/github-script@v4
        if: |
          contains(github.event.pull_request.labels.*.name, 'backport: auto') &&
          contains(github.event.pull_request.labels.*.name, 'backport: skip')
        with:
          script: |
            github.issues.removeLabel({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              name: 'backport: auto'
            })

  commit:
    if: |
      github.event.pull_request.merged == true
      && contains(github.event.pull_request.labels.*.name, 'backport: auto')
      && (
        (github.event.action == 'labeled' && github.event.label.name == 'backport: auto')
        || (github.event.action == 'closed')
      )
    needs: get-branches
    runs-on: ubuntu-latest
    strategy:
      max-parallel: 1
      matrix:
        # 7.17 was intentionally skipped because it was added late and was bug fix only
        target_branch: ${{ fromJSON(needs.get-branches.outputs.branches) }}

    steps:
      - name: Checkout repo
        uses: actions/checkout@v2
        with:
          token: ${{ secrets.PROTECTIONS_MACHINE_TOKEN }}
          ref: main
          fetch-depth: 100

      - name: Set github config
        run: |
          git config --global user.email "41898282+github-actions[bot]@users.noreply.github.com"
          git config --global user.name "github-actions[bot]"

      - name: Get branch histories
        run: |
          git fetch origin ${{matrix.target_branch}} --depth 1
          git status
          git log -1 --format='%H'

      - name: Checkout the commit into the staging area
        run: |
          # Checkout the merged commit
          git checkout ${{github.event.pull_request.merge_commit_sha}}

          # Move it to the staging area
          git reset --soft HEAD^

      - name: Install dependencies
        run: |
          python -m pip install --upgrade pip
          pip install .[dev]

      - name: Prune non-${{matrix.target_branch}} rules
        env:
          UNSTAGED_LIST_FILE: "../unstaged-rules.txt"
        run: |
          python -m detection_rules dev unstage-incompatible-rules --target-stack-version ${{matrix.target_branch}}

          # Track which rules were unstaged
          git diff --name-only > $UNSTAGED_LIST_FILE

          # Since they've been tracked, remove any untracked files
          git checkout -- .

      - name: Commit and push to ${{matrix.target_branch}}
        env:
          COMMIT_MSG_FILE: "../commit-message.txt"
          UNSTAGED_LIST_FILE: "../unstaged-rules.txt"
        run: |
          set -x

          echo "Switch to the target branch and keep the staged changes"
          git checkout ${{matrix.target_branch}}

          NEEDS_BACKPORT=$(git diff HEAD --quiet --exit-code && echo n || echo y)

          if [ "n" = "$NEEDS_BACKPORT" ]
          then
            echo "No changes to backport"
            exit 0
          fi

          echo "Create the new commit with the same author"
          git commit --reuse-message ${{github.event.pull_request.merge_commit_sha}}

          echo "Save the commit message"
          git log ${{github.event.pull_request.merge_commit_sha}} --format=%B -n1 > $COMMIT_MSG_FILE

          echo "Append to the commit message"
          if [ -s "$UNSTAGED_LIST_FILE" ]
          then
            echo "Track note for the removed files"

            echo "" >> $COMMIT_MSG_FILE
            echo "Removed changes from:" >> $COMMIT_MSG_FILE
            awk '{print "- " $0}' $UNSTAGED_LIST_FILE >> $COMMIT_MSG_FILE
            echo "" >> $COMMIT_MSG_FILE
            echo '(selectively cherry picked from commit ${{github.event.pull_request.merge_commit_sha}})' >> $COMMIT_MSG_FILE
          else
            echo "No removed files"

            echo "" >> $COMMIT_MSG_FILE
            echo '(cherry picked from commit ${{github.event.pull_request.merge_commit_sha}})' >> $COMMIT_MSG_FILE
          fi

          echo "Amend the commit message and push"
          git commit --amend -F $COMMIT_MSG_FILE
          git push

      - name: "Notify slack on failure"
        uses: craftech-io/slack-action@v1
        with:
          slack_webhook_url: ${{ secrets.SLACK_WEBHOOK_URL }}
          status: failure
        if: failure()