name: Security scan

# Trivy scans the repo filesystem for:
#   - vuln     — known-vulnerable Python dependencies
#   - secret   — hardcoded credentials / API keys committed by mistake
#   - misconfig — workflow / config hardening issues
# Findings are reported to the Security tab (code scanning), never used to
# block a merge — a CVE in a third-party dep you can't patch on the spot must
# not gate CI. The weekly run matters most: new CVEs are disclosed against
# dependencies that never changed, so a scan only on push would miss them.
#
# NOTE on the pip freeze: our requirements.txt uses >= (loose) constraints, and
# Trivy's vuln matcher needs PINNED versions — a loose file scans as "0
# packages" (it silently checks nothing). So we install the project and freeze
# the RESOLVED versions into a requirements.txt Trivy recognises; the scan of
# the repo root then picks it up and checks the actual dependency tree.
on:
  push:
    branches: [main]
  pull_request:
  schedule:
    - cron: "0 6 * * 1" # Mondays 06:00 UTC — CVEs land continuously
  workflow_dispatch:

permissions:
  contents: read
  security-events: write # upload the SARIF report to the Security tab

concurrency:
  group: security-${{ github.ref }}
  cancel-in-progress: true

jobs:
  trivy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with:
          python-version: "3.11"
          cache: pip

      - name: Freeze resolved dependency versions (Trivy needs pinned versions)
        run: |
          pip install -e .
          mkdir -p .trivy-deps
          # pinned, editable project excluded → the transitive tree Trivy can match
          pip freeze --exclude-editable > .trivy-deps/requirements.txt
          echo "resolved $(wc -l < .trivy-deps/requirements.txt) pinned packages for scanning"

      - name: Trivy scan → readable table in the run log
        uses: aquasecurity/trivy-action@v0.36.0
        with:
          scan-type: fs
          scan-ref: .
          scanners: vuln,secret,misconfig
          severity: HIGH,CRITICAL
          ignore-unfixed: true # only vulns with a fix available — actionable ones
          format: table
          exit-code: "0" # report-only: a dependency CVE must not block the merge

      - name: Trivy scan → SARIF for the Security tab
        uses: aquasecurity/trivy-action@v0.36.0
        with:
          scan-type: fs
          scan-ref: .
          scanners: vuln,secret,misconfig
          ignore-unfixed: true
          format: sarif
          output: trivy-results.sarif
          exit-code: "0"
          skip-setup-trivy: true # reuse the vuln DB the table step already pulled

      - name: Upload SARIF to the Security tab
        if: always() # upload even when the scan surfaced findings
        uses: github/codeql-action/upload-sarif@v4
        with:
          sarif_file: trivy-results.sarif