name: Security Gate

# Reusable (workflow_call) gate, called as the FIRST job of each CI workflow;
# their real jobs declare `needs: gate`. Does NOT scan — the single scan runs in
# security-scan.yml. This poller only decides whether to let its caller proceed:
#   - non-PR event or trusted author -> proceed immediately
#   - untrusted PR -> wait for the `Security Scan` check on the head SHA and
#     MIRROR its conclusion (success -> proceed; failure -> fail, skipping the
#     dependent CI jobs).
#
# The scan (security-scan.yml) is blocking: a finding fails the `Security Scan`
# check, which this poller mirrors to block dependent CI. Splitting scan from
# gate runs the scan once, not once per workflow. The trust decision is read
# from `main` (should-scan.sh).

on:
  workflow_call:

permissions:
  contents: read

jobs:
  gate:
    name: Security Gate
    runs-on: ubuntu-latest
    timeout-minutes: 12
    steps:
      - name: Check out trust check from main
        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0  # v7.0.0
        with:
          ref: main             # trusted; never the PR head
          sparse-checkout: .github/scripts/security-scan
          persist-credentials: false

      - name: Trust gate
        id: gate
        env:
          EVENT_NAME: ${{ github.event_name }}
          AUTHOR_ASSOCIATION: ${{ github.event.pull_request.author_association }}
        run: |
          # Before the scanner lands on main the scripts are absent there --
          # proceed (fail-open) so the introducing PR is not bricked.
          if [ ! -f .github/scripts/security-scan/should-scan.sh ]; then
            echo "::warning::security scanner not present on main yet; proceeding (bootstrap)."
            echo "scan=false" >> "$GITHUB_OUTPUT"
            exit 0
          fi
          bash .github/scripts/security-scan/should-scan.sh

      - name: Wait for Security Scan result
        # Only untrusted PRs wait; trusted authors / non-PR events proceeded above.
        if: ${{ steps.gate.outputs.scan == 'true' }}
        env:
          GH_TOKEN: ${{ github.token }}
          REPO: ${{ github.repository }}
          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
        run: |
          echo "Untrusted PR -- waiting for the single 'Security Scan' check on $HEAD_SHA"
          # First-timer short-circuit. When a first-time contributor's runs are
          # held behind GitHub's approval gate, Security Scan shows up as a
          # workflow RUN with conclusion=action_required and NO check-run, so the
          # poll below never sees it and spins the full ~6 min before failing
          # open. Detect the held state and proceed now (same fail-open outcome);
          # the gate re-runs on the next push or maintainer approval event.
          held=$(gh api "repos/$REPO/actions/runs?head_sha=$HEAD_SHA&event=pull_request" \
            --jq '[.workflow_runs[] | select(.name=="Security Scan")] | sort_by(.created_at) | last | .conclusion' 2>/dev/null || echo "")
          if [ "$held" = "action_required" ]; then
            echo "::warning::Security Scan is awaiting maintainer approval (action_required); proceeding (fail-open). It will re-gate on the next push or maintainer approval event."
            exit 0
          fi
          q='[.check_runs[] | select(.name=="Security Scan")] | sort_by(.started_at) | last'
          conclusion=""
          details_url=""
          for _ in $(seq 1 108); do  # up to ~9 min (108 * 5s)
            status=$(gh api "repos/$REPO/commits/$HEAD_SHA/check-runs" --jq "$q | .status" 2>/dev/null || echo "")
            if [ "$status" = "completed" ]; then
              conclusion=$(gh api "repos/$REPO/commits/$HEAD_SHA/check-runs" --jq "$q | .conclusion")
              # The scan's own run page -- where the findings/annotations live.
              details_url=$(gh api "repos/$REPO/commits/$HEAD_SHA/check-runs" --jq "$q | .html_url")
              break
            fi
            sleep 5
          done
          if [ -z "$conclusion" ]; then
            echo "::warning::Security Scan check did not complete in time; proceeding (fail-open)."
            exit 0
          fi
          echo "Security Scan concluded: $conclusion"
          case "$conclusion" in
            success | skipped | neutral) exit 0 ;;
            *)
              echo "::error::Security Scan did not pass ($conclusion); dependent CI is blocked until it passes. See the findings: ${details_url:-the 'Security Scan' check on this PR}"
              exit 1
              ;;
          esac