name: Trigger Merge Gate

on:
  pull_request_target:
    types: [labeled, synchronize]

permissions:
  contents: read
  pull-requests: read
  actions: read

concurrency:
  group: merge-gate-${{ github.event.pull_request.number }}
  cancel-in-progress: false

jobs:
  trigger:
    if: >-
      (github.event.action == 'labeled' && github.event.label.name == 'ready')
      || github.event.action == 'synchronize'
    runs-on: ubuntu-latest
    # Gate below may wait for cheap checks (up to MAX_WAIT_SECS = 25 min).
    timeout-minutes: 35
    steps:
      - name: Check ready label
        id: check
        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
        with:
          script: |
            const { data: pr } = await github.rest.pulls.get({
              owner: context.repo.owner,
              repo: context.repo.repo,
              pull_number: context.payload.pull_request.number,
            });
            const hasReady = pr.labels.some(l => l.name === 'ready');
            core.setOutput('has_ready', String(hasReady));
            core.setOutput('changed_files', String(pr.changed_files));
            if (!hasReady) core.info('No ready label — skipping merge-gate trigger.');

      - name: Cancel previous Buildkite builds
        if: steps.check.outputs.has_ready == 'true'
        env:
          BUILDKITE_API_TOKEN: ${{ secrets.BUILDKITE_API_TOKEN }}
          PR_BRANCH: ${{ github.event.pull_request.head.ref }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
        run: |
          # Match both branch and PR number: forks can reuse the same branch name.
          builds=$(curl -sS --get -H "Authorization: Bearer $BUILDKITE_API_TOKEN" \
            --data-urlencode "branch=$PR_BRANCH" \
            --data-urlencode "state=running,scheduled" \
            "https://api.buildkite.com/v2/organizations/${{ vars.BUILDKITE_ORG_SLUG }}/pipelines/${{ vars.BUILDKITE_PIPELINE_SLUG }}/builds" \
            | jq -r --arg pr_number "$PR_NUMBER" \
              '.[] | select((.env.TEST_SCOPE? == "merge") and (.env.PR_NUMBER? == $pr_number)) | .number')
          for build_num in $builds; do
            echo "Cancelling Buildkite build #$build_num"
            curl -sS -X PUT -H "Authorization: Bearer $BUILDKITE_API_TOKEN" \
              "https://api.buildkite.com/v2/organizations/${{ vars.BUILDKITE_ORG_SLUG }}/pipelines/${{ vars.BUILDKITE_PIPELINE_SLUG }}/builds/${build_num}/cancel"
          done

      # Check out the immutable BASE SHA: pull_request_target must never run a
      # planner or gate script from the untrusted PR head.
      - name: Checkout trusted merge planner
        if: steps.check.outputs.has_ready == 'true'
        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
        with:
          ref: ${{ github.event.pull_request.base.sha }}
          persist-credentials: false

      - name: Collect changed paths
        if: steps.check.outputs.has_ready == 'true'
        env:
          GH_TOKEN: ${{ github.token }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
          EXPECTED_CHANGED_FILES: ${{ steps.check.outputs.changed_files }}
        run: |
          set -euo pipefail
          changed_json="$RUNNER_TEMP/merge-changed-files.json"
          changed_paths="$RUNNER_TEMP/merge-changed-paths.txt"
          if gh api --paginate --slurp \
              "repos/${GITHUB_REPOSITORY}/pulls/${PR_NUMBER}/files?per_page=100" \
              > "$changed_json"; then
            observed=$(jq '[.[][] | .filename] | unique | length' "$changed_json")
            if [ "$observed" = "$EXPECTED_CHANGED_FILES" ]; then
              jq -r '.[][] | .filename, (.previous_filename // empty)' "$changed_json" \
                | sort -u > "$changed_paths"
            else
              echo "::warning::Changed-file API returned $observed of $EXPECTED_CHANGED_FILES paths; selecting all merge lanes."
              echo '__FASTVIDEO_CI_PLAN_ALL__' > "$changed_paths"
            fi
          else
            echo "::warning::Changed-file API failed; selecting all merge lanes."
            echo '__FASTVIDEO_CI_PLAN_ALL__' > "$changed_paths"
          fi

      - name: Select minimal merge tests
        id: plan
        if: steps.check.outputs.has_ready == 'true'
        run: |
          python3 .github/scripts/plan_merge_ci.py \
            --paths-file "$RUNNER_TEMP/merge-changed-paths.txt" \
            --github-output "$GITHUB_OUTPUT" \
            --summary-file "$GITHUB_STEP_SUMMARY"

      - name: Wait for pre-commit and docs build
        if: steps.check.outputs.has_ready == 'true'
        env:
          GH_TOKEN: ${{ github.token }}
          PR_SHA: ${{ github.event.pull_request.head.sha }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
        run: bash .github/scripts/gate_full_suite.sh

      - name: Trigger Buildkite merge gate
        if: steps.check.outputs.has_ready == 'true'
        env:
          BUILDKITE_API_TOKEN: ${{ secrets.BUILDKITE_API_TOKEN }}
          PR_SHA: ${{ github.event.pull_request.head.sha }}
          PR_BRANCH: ${{ github.event.pull_request.head.ref }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
          PR_TITLE: ${{ github.event.pull_request.title }}
          BK_ORG: ${{ vars.BUILDKITE_ORG_SLUG }}
          BK_PIPELINE: ${{ vars.BUILDKITE_PIPELINE_SLUG }}
          MERGE_TEST_PLAN: ${{ steps.plan.outputs.merge_test_plan }}
          MERGE_GOLDEN_TESTS: ${{ steps.plan.outputs.merge_golden_tests }}
          MERGE_SSIM_TESTS: ${{ steps.plan.outputs.merge_ssim_tests }}
          MERGE_PLAN_LABEL: ${{ steps.plan.outputs.merge_plan_label }}
        run: |
          curl -sS --fail-with-body -X POST \
            "https://api.buildkite.com/v2/organizations/${BK_ORG}/pipelines/${BK_PIPELINE}/builds" \
            -H "Authorization: Bearer $BUILDKITE_API_TOKEN" \
            -H "Content-Type: application/json" \
            --data-raw "$(jq -n \
              --arg commit "$PR_SHA" \
              --arg branch "$PR_BRANCH" \
              --arg message "Merge gate [${MERGE_PLAN_LABEL}] for PR #${PR_NUMBER}" \
              --arg pr_title "$PR_TITLE" \
              --arg merge_test_plan "$MERGE_TEST_PLAN" \
              --arg merge_golden_tests "$MERGE_GOLDEN_TESTS" \
              --arg merge_ssim_tests "$MERGE_SSIM_TESTS" \
              --argjson pr_id "$PR_NUMBER" \
              '{
                commit: $commit,
                branch: $branch,
                message: $message,
                ignore_pipeline_branch_filters: true,
                pull_request_id: $pr_id,
                pull_request_base_branch: "main",
                env: {
                  TEST_SCOPE: "merge",
                  FULL_SUITE: "true",
                  MERGE_TEST_PLAN: $merge_test_plan,
                  MERGE_GOLDEN_TESTS: $merge_golden_tests,
                  MERGE_SSIM_TESTS: $merge_ssim_tests,
                  PR_NUMBER: ($pr_id | tostring),
                  PR_TITLE: $pr_title
                }
              }')"