name: Backend Tests

# Always triggers so it can be a required PR check; the `changes` job below
# decides whether backend/extension paths actually changed (test-only changes
# match the same globs, since tests are co-located with the code), and every
# other job is skipped — not absent — when they didn't, which still satisfies
# a required check. puter.js SDK changes are covered by puterjs-tests.yaml.
on:
  pull_request:
    types: [opened, synchronize, reopened]

permissions:
  contents: read
  pull-requests: write

jobs:
  changes:
    runs-on: ubuntu-latest
    outputs:
      backend: ${{ steps.filter.outputs.backend }}
    steps:
      - uses: actions/checkout@v7
      - uses: dorny/paths-filter@v3
        id: filter
        with:
          filters: |
            backend:
              - 'src/backend/**'
              - 'extensions/**'
              - 'tools/**'
              - 'package.json'
              - 'package-lock.json'
              - 'tsconfig.json'
              - 'tsconfig.build.json'
              - '.github/workflows/backend-tests.yaml'

  # `tsconfig.build.json` builds with `noCheck: true`, so nothing else in CI
  # runs the type checker and a missing export compiles to `undefined`,
  # surfacing only when the call is finally reached at runtime. This diffs
  # against tools/typecheck-baseline.json and fails only on *new* errors.
  #
  # The consuming repo runs an equivalent gate, but only once someone bumps the
  # submodule pointer — too late to keep the error off this repo's default
  # branch. Hence a gate here, on this repo's own pull requests.
  #
  # Its own job rather than a step in `test`: that one runs a base/PR matrix for
  # coverage comparison, and the check only needs the PR ref, once.
  typecheck:
    needs: changes
    if: needs.changes.outputs.backend == 'true'
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repository
        uses: actions/checkout@v7

      - name: Set up Node.js
        uses: actions/setup-node@v7
        with:
          node-version: '24'
          cache: 'npm'

      - name: Install dependencies
        run: npm ci

      - name: Type check (new errors only)
        run: npm run typecheck

  # `needs.changes` gates the steps below, not this job, on purpose: a
  # job-level `if` on a matrix job skips the whole job as one unexpanded
  # check ("test (${{ matrix.artifact }})", literally, since there's no
  # matrix context to fill it in) instead of the two real per-artifact
  # checks a required rule pins to ("test (base)" / "test (pr)") — so the
  # required check never gets reported and the PR blocks forever. Letting
  # the matrix always expand keeps the check names stable either way.
  test:
    needs: changes
    # Overrides the default matrix naming, which would otherwise bake the
    # base/head branch name (matrix.ref) into the check name — making it a
    # different string on every PR and impossible to pin as a required check.
    name: test (${{ matrix.artifact }})
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        include:
          - ref: ${{ github.base_ref }}
            artifact: base
          - ref: ${{ github.head_ref }}
            artifact: pr

    steps:
      - name: Checkout ${{ matrix.ref }}
        if: needs.changes.outputs.backend == 'true'
        uses: actions/checkout@v7
        with:
          ref: ${{ matrix.ref }}
          repository: ${{ github.event.pull_request.head.repo.full_name }}

      - name: Set up Node.js
        if: needs.changes.outputs.backend == 'true'
        uses: actions/setup-node@v7
        with:
          node-version: '24'
          cache: 'npm'

      - name: Install dependencies
        if: needs.changes.outputs.backend == 'true'
        run: npm ci

      - name: Run backend tests with coverage
        if: needs.changes.outputs.backend == 'true'
        run: npm run test:backend -- --coverage
        env:
          CI: 'true'

      - name: Upload coverage artifact
        if: needs.changes.outputs.backend == 'true' && !cancelled()
        uses: actions/upload-artifact@v7
        with:
          name: backend-coverage-${{ matrix.artifact }}
          path: src/backend/coverage/
          retention-days: 14

  report-coverage:
    needs: [changes, test]
    if: always() && needs.changes.outputs.backend == 'true'
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repository
        uses: actions/checkout@v7

      - name: Download PR coverage
        uses: actions/download-artifact@v8
        with:
          name: backend-coverage-pr
          path: src/backend/coverage

      - name: Download base coverage
        uses: actions/download-artifact@v8
        with:
          name: backend-coverage-base
          path: coverage-base

      - name: Report coverage on PR
        uses: davelosert/vitest-coverage-report-action@v2
        with:
          json-summary-path: src/backend/coverage/coverage-summary.json
          json-final-path: src/backend/coverage/coverage-final.json
          json-summary-compare-path: coverage-base/coverage-summary.json