name: "CodeQL"

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]
  schedule:
    - cron: "0 6 * * 1" # Weekly on Monday at 06:00 UTC

permissions:
  contents: read
  security-events: write

jobs:
  changes:
    name: Detect changed paths
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: read
    outputs:
      matrix: ${{ steps.build-matrix.outputs.matrix }}
      skipped-matrix: ${{ steps.build-matrix.outputs.skipped-matrix }}
    steps:
      - uses: actions/checkout@v4

      - uses: dorny/paths-filter@v3
        id: filter
        if: github.event_name == 'pull_request'
        with:
          filters: |
            java:
              - 'java/**'
            js:
              - 'nodejs/**'
              - 'scripts/**'
              - 'test/harness/**'
            python:
              - 'python/**'
            go:
              - 'go/**'
            rust:
              - 'rust/**'
            csharp:
              - 'dotnet/**'
            actions:
              - '.github/workflows/**'
              - '.github/actions/**'

      - name: Build language matrix
        id: build-matrix
        run: |
          ALL_LANGUAGES=("java-kotlin" "javascript-typescript" "python" "go" "rust" "csharp" "actions")
          ALL_GATES=("java" "js" "python" "go" "rust" "csharp" "actions")

          # On push/schedule, analyse ALL languages; skip none.
          if [[ "${{ github.event_name }}" != "pull_request" ]]; then
            entries=()
            for lang in "${ALL_LANGUAGES[@]}"; do
              entries+=("{\"language\":\"${lang}\"}")
            done
            joined=$(IFS=,; echo "${entries[*]}")
            echo "matrix={\"include\":[${joined}]}" >> "$GITHUB_OUTPUT"
            echo 'skipped-matrix={"include":[]}' >> "$GITHUB_OUTPUT"
          else
            entries=()
            skipped=()
            filter_outputs=("${{ steps.filter.outputs.java }}" "${{ steps.filter.outputs.js }}" "${{ steps.filter.outputs.python }}" "${{ steps.filter.outputs.go }}" "${{ steps.filter.outputs.rust }}" "${{ steps.filter.outputs.csharp }}" "${{ steps.filter.outputs.actions }}")

            for i in "${!ALL_LANGUAGES[@]}"; do
              lang="${ALL_LANGUAGES[$i]}"
              changed="${filter_outputs[$i]}"
              if [[ "$changed" == "true" ]]; then
                entries+=("{\"language\":\"${lang}\"}")
              else
                skipped+=("{\"language\":\"${lang}\"}")
              fi
            done

            if [[ ${#entries[@]} -eq 0 ]]; then
              echo 'matrix={"include":[]}' >> "$GITHUB_OUTPUT"
            else
              joined=$(IFS=,; echo "${entries[*]}")
              echo "matrix={\"include\":[${joined}]}" >> "$GITHUB_OUTPUT"
            fi

            if [[ ${#skipped[@]} -eq 0 ]]; then
              echo 'skipped-matrix={"include":[]}' >> "$GITHUB_OUTPUT"
            else
              joined=$(IFS=,; echo "${skipped[*]}")
              echo "skipped-matrix={\"include\":[${joined}]}" >> "$GITHUB_OUTPUT"
            fi
          fi

  analyze:
    name: Analyze (${{ matrix.language }})
    needs: changes
    if: ${{ fromJson(needs.changes.outputs.matrix).include[0] != null }}
    runs-on: ubuntu-latest
    permissions:
      security-events: write
      contents: read
    strategy:
      fail-fast: false
      matrix: ${{ fromJson(needs.changes.outputs.matrix) }}
    steps:
      - name: Checkout repository
        uses: actions/checkout@v4

      - name: Initialize CodeQL
        uses: github/codeql-action/init@v3
        with:
          languages: ${{ matrix.language }}

      - name: Autobuild
        uses: github/codeql-action/autobuild@v3

      - name: Perform CodeQL Analysis
        uses: github/codeql-action/analyze@v3
        with:
          category: "/language:${{ matrix.language }}"

  # Upload empty SARIF for languages that were NOT analysed in this PR.
  # Code scanning branch protection expects results for every category that
  # has ever been uploaded on the default branch; missing categories block merge.
  skip-analysis:
    name: Skip (${{ matrix.language }})
    needs: changes
    if: ${{ github.event_name == 'pull_request' && fromJson(needs.changes.outputs.skipped-matrix).include[0] != null }}
    runs-on: ubuntu-latest
    permissions:
      security-events: write
    strategy:
      fail-fast: false
      matrix: ${{ fromJson(needs.changes.outputs.skipped-matrix) }}
    steps:
      - name: Create empty SARIF
        run: |
          cat > "$RUNNER_TEMP/empty.sarif" <<'EOF'
          {
            "version": "2.1.0",
            "$schema": "https://json.schemastore.org/sarif-2.1.0.json",
            "runs": [{
              "tool": { "driver": { "name": "CodeQL", "version": "0.0.0" } },
              "results": []
            }]
          }
          EOF

      - name: Upload empty SARIF
        uses: github/codeql-action/upload-sarif@v3
        with:
          sarif_file: ${{ runner.temp }}/empty.sarif
          category: "/language:${{ matrix.language }}"