name: Security Scan

on:
  schedule:
    - cron: '30 1 * * 1,4'  # Mon/Thu 7 AM IST
  workflow_dispatch:
  push:
    branches: [main]
    paths-ignore:
      - 'docs/**'
      - 'mkdocs.yml'
      - 'requirements-docs.txt'
      - '**/*.md'
  pull_request:
    branches: [main]
    paths-ignore:
      - 'docs/**'
      - 'mkdocs.yml'
      - 'requirements-docs.txt'
      - '**/*.md'

permissions:
  contents: read

jobs:
  security-scan:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      security-events: write
      actions: read
      # Needed for the "Comment PR with Security Results" step below. Safe on
      # pull_request (not pull_request_target): GitHub always forces a
      # read-only token for PRs from forks regardless of this permission.
      pull-requests: write

    steps:
      - name: Checkout repository
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7

      - name: Set up Python
        uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7
        with:
          python-version: '3.11'
        
      - name: Install dependencies
        run: |
          pip install -r .github/requirements/bootstrap.txt --require-hashes
          # Install the pinned dependency set FIRST so pip-audit scans
          # Semantica's exact CI/release dependency tree (requirements-ci.txt
          # is generated from pyproject.toml extras, so this covers the
          # project's real deps).
          pip install -r requirements-ci.txt --require-hashes
          # Tooling AFTER the pinned set: installing it first would let the
          # pinned requirements overwrite the tooling's own transitive deps.
          pip install -r .github/requirements/pip-audit.txt --require-hashes
          pip install -r .github/requirements/security-scan-tools.txt --require-hashes

      - name: Run pip-audit (Package Vulnerabilities)
        continue-on-error: true
        run: |
          # Keep publishing reports and the PR comment even when the audit
          # gate fails. The final gate below preserves the failure status.
          echo 'AUDIT_SCAN_STATUS=failed' >> "$GITHUB_ENV"

          # Same dependency tree Safety used to scan, and the same tool and
          # invocation already proven reliable in security.yml.
          pip-audit -r requirements-ci.txt --format=json --output=pip-audit-report.json || true

          # Guard 1: fail loudly if pip-audit exited before writing a report
          # at all (network error, tool crash). Without this check a missing
          # or empty file causes jq to fall back to "0", making a broken
          # scanner indistinguishable from a clean scan.
          if [ ! -s pip-audit-report.json ]; then
            echo "::error::pip-audit produced no report (pip-audit-report.json is missing or empty). Treating as failure — check for network errors or pip-audit crashes in the logs above."
            exit 1
          fi

          # Guard 2: fail closed when the report doesn't have the shape the
          # checks below assume: a non-empty dependencies array, each entry
          # either carrying an array-valued vulns field or being a dependency
          # pip-audit couldn't resolve/audit, which it reports as
          # {"name": ..., "skip_reason": ...} with no vulns field at all
          # (see pip_audit._format.json.JsonFormat._format_dep). That's a
          # normal, documented report shape, not a malformed one — treating
          # it as invalid would fail the whole job over a single unauditable
          # package, the same kind of scan-unrelated CI break this migration
          # away from Safety was meant to fix.
          if ! jq -e '
            (.dependencies | type == "array" and length > 0)
            and all(.dependencies[]; type == "object" and ((.vulns | type == "array") or (.skip_reason | type == "string")))
          ' pip-audit-report.json >/dev/null 2>&1; then
            echo "::error::pip-audit report has an invalid dependency structure. Expected a non-empty dependencies array where every entry has either a vulns array or a skip_reason. Treating as failure."
            exit 1
          fi

          echo "Checking for package vulnerabilities..."

          # Guard 2 above already confirmed pip-audit-report.json is valid
          # JSON with a well-shaped dependencies array, so this count is
          # always a plain non-negative integer.
          SKIPPED=$(jq '[.dependencies[] | select(has("skip_reason"))] | length' pip-audit-report.json)
          if [ "$SKIPPED" -gt 0 ]; then
            echo "⚠️ pip-audit could not audit $SKIPPED dependencies (see pip-audit-report.json for skip_reason):"
            jq -r '.dependencies[] | select(has("skip_reason")) | "  - \(.name): \(.skip_reason)"' pip-audit-report.json
          fi

          # Vulnerability IDs reviewed and accepted as non-actionable for this
          # project. Empty for now: pip-audit's OSV-backed database doesn't
          # currently carry either of the findings Safety used to flag here
          # (cuda-toolkit CVE-2025-33228, torchvision CVE-2026-65918), so
          # there's nothing to exclude. Left in place so a future finding can
          # be added the same way without restructuring this step - see git
          # history on this file for the reasoning behind past entries.
          IGNORED_VULN_IDS=""

          # Exported so the "Comment PR with Security Results" step below can
          # apply the same exclusion list to the raw report - it reads
          # pip-audit-report.json independently in JS, so without this the PR
          # comment would show an accepted finding as live even though this
          # gate correctly treats it as non-actionable.
          echo "IGNORED_VULN_IDS=$IGNORED_VULN_IDS" >> "$GITHUB_ENV"

          # No []? / || echo "0" fallback: if jq fails (malformed JSON) VULNS
          # will be empty or "null" so Guard 3 below catches it rather than
          # silently treating the broken report as zero.
          # `.vulns // []` guards against skipped dependencies, which carry
          # no vulns field at all (see the skip_reason handling above) -
          # without the fallback, iterating `null[]` raises inside jq and
          # this whole computation silently evaluates to empty.
          VULNS=$(jq --arg ignored "$IGNORED_VULN_IDS" '
            ($ignored | split(",") | map(select(length > 0))) as $ignore_list
            | [.dependencies[] | (.vulns // [])[] | select(.id as $id | ($ignore_list | index($id)) | not)]
            | length
          ' pip-audit-report.json 2>/dev/null)

          # Guard 3: ensure VULNS is a non-negative integer before the -gt
          # comparison. "null" (missing/null key) or "" (jq parse failure) would
          # cause bash's -gt to throw an arithmetic error and fall through to the
          # success branch — the same silent-pass bug as a missing file.
          if ! [[ "$VULNS" =~ ^[0-9]+$ ]]; then
            echo "::error::pip-audit report exists but dependency vulnerabilities are missing or non-numeric (got: '${VULNS}'). The report may be malformed or contain an error-only JSON response. Treating as failure."
            exit 1
          fi

          if [ "$VULNS" -gt 0 ]; then
            echo "❌ Security vulnerabilities found: $VULNS"
            echo "CI will fail to prevent merging of vulnerable dependencies"
            echo ""
            echo "Vulnerability details:"
            jq --arg ignored "$IGNORED_VULN_IDS" -r '
              ($ignored | split(",") | map(select(length > 0))) as $ignore_list
              | .dependencies[] as $dependency
              | ($dependency.vulns // [])[] | select(.id as $id | ($ignore_list | index($id)) | not)
              | "- \($dependency.name)==\($dependency.version): \(.id)"
            ' pip-audit-report.json || true
            exit 1
          else
            echo "✅ No actionable security vulnerabilities found${IGNORED_VULN_IDS:+ (ignored: $IGNORED_VULN_IDS)}"
            echo 'AUDIT_SCAN_STATUS=passed' >> "$GITHUB_ENV"
          fi

      - name: Run Bandit (Code Security Linter)
        run: |
          bandit -r semantica/ -f json -o bandit-report.json || true
          echo "Checking for HIGH severity security issues..."
          
          # Count HIGH severity issues
          HIGH_ISSUES=$(bandit -r semantica/ -f json -ll 2>/dev/null | jq -r '.results[]? | select(.issue_severity == "HIGH") | .test_name' 2>/dev/null | wc -l || echo "0")
          
          if [ "$HIGH_ISSUES" -gt 0 ]; then
            echo "❌ HIGH severity security issues found: $HIGH_ISSUES"
            echo "CI will fail to prevent merging of high-risk code"
            echo ""
            echo "High severity issues:"
            bandit -r semantica/ -ll | grep "Severity: High" -A 5 -B 1 || true
            exit 1
          else
            echo "✅ No HIGH severity security issues found"
          fi
        
      - name: Run Semgrep (Static Analysis)
        run: |
          echo "Running Semgrep static analysis..."
          semgrep --config=auto --json --output=semgrep-report.json semantica/ || true
          
          # Run security-focused rules
          echo "Checking for security patterns..."
          SECURITY_ISSUES=$(semgrep --config=p/security --json semantica/ 2>/dev/null | jq '.results | length' 2>/dev/null || echo "0")
          
          if [ "$SECURITY_ISSUES" -gt 0 ]; then
            echo "⚠️ Security patterns found: $SECURITY_ISSUES"
            echo "Review these findings for potential improvements"
            semgrep --config=p/security semantica/ || true
          else
            echo "✅ No security patterns found"
          fi
        
      - name: Upload Security Reports
        if: always()
        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7
        with:
          name: security-reports
          retention-days: 14
          path: |
            pip-audit-report.json
            bandit-report.json
            semgrep-report.json
        
      - name: Comment PR with Security Results
        if: always() && github.event_name == 'pull_request'
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9
        with:
          script: |
            const fs = require('fs');

            // Renders one tool's findings as a section. `items` is already
            // the list of pre-formatted "- `thing` in `where`" strings; this
            // just handles the found/not-found/report-missing framing and
            // collapses long lists into a <details> block so the comment
            // doesn't turn into a wall of text.
            function renderSection(title, reportPath, parse) {
              let data;
              try {
                data = JSON.parse(fs.readFileSync(reportPath, 'utf8'));
              } catch (e) {
                return [
                  `### ${title}`,
                  `⚠️ No report found at \`${reportPath}\` — the scan may have failed before producing output. Check the job logs.`,
                ].join('\n');
              }

              const items = parse(data);
              if (items === null) {
                return [
                  '### ' + title,
                  '⚠️ Invalid report structure in ' + reportPath + ' — check the job logs.',
                ].join('\n');
              }
              if (items.length === 0) {
                return [`### ${title}`, `✅ No findings.`].join('\n');
              }

              const lines = [`### ${title}`, `Found **${items.length}**.`, ''];
              const shown = items.slice(0, 15);
              if (items.length > 15) {
                lines.push('<details>', '<summary>Show all findings</summary>', '');
                lines.push(...items);
                lines.push('', '</details>');
              } else {
                lines.push(...shown);
              }
              return lines.join('\n');
            }

            // Mirrors the shell step's own IGNORED_VULN_IDS (passed through
            // $GITHUB_ENV) so an accepted, non-actionable CVE that the CI
            // gate already excluded doesn't reappear here as a live finding -
            // this reads the same raw, unfiltered pip-audit-report.json.
            const ignoredVulnIds = (process.env.IGNORED_VULN_IDS || '')
              .split(',')
              .map((id) => id.trim())
              .filter(Boolean);

            // A dependency pip-audit couldn't resolve/audit is reported as
            // {"name": ..., "skip_reason": ...} with no vulns field at all
            // (see pip_audit._format.json.JsonFormat._format_dep) - that's a
            // normal report shape, not a malformed one, so it must not be
            // treated as an invalid dependency below.
            const isSkipped = (dependency) => typeof dependency.skip_reason === 'string';

            let skippedDeps = [];
            try {
              const auditData = JSON.parse(fs.readFileSync('pip-audit-report.json', 'utf8'));
              skippedDeps = (auditData.dependencies || []).filter(
                (dependency) => dependency && typeof dependency === 'object' && isSkipped(dependency)
              );
            } catch (e) {
              // Unreadable/unparseable report - renderSection's own
              // report-missing branch below surfaces this.
            }

            const pipAuditSection = renderSection(
              'pip-audit — dependency vulnerabilities',
              'pip-audit-report.json',
              (data) => {
                if (
                  !Array.isArray(data.dependencies) ||
                  data.dependencies.length === 0 ||
                  data.dependencies.some(
                    (dependency) =>
                      !dependency ||
                      typeof dependency !== 'object' ||
                      (!Array.isArray(dependency.vulns) && !isSkipped(dependency))
                  )
                ) {
                  return null;
                }

                return data.dependencies.flatMap((dependency) =>
                  (dependency.vulns || [])
                    .filter((vulnerability) => !ignoredVulnIds.includes(vulnerability.id))
                    .map(
                      (vulnerability) => `- \`${dependency.name}==${dependency.version}\`: ${vulnerability.id}` +
                        (vulnerability.fix_versions?.length ? ` (fixed by ${vulnerability.fix_versions.join(', ')})` : '')
                    )
                );
              }
            ) + (ignoredVulnIds.length
              ? `\n\n_Excluded as accepted, non-actionable findings: ${ignoredVulnIds.join(', ')} — see the workflow file's inline comments for why._`
              : '') + (skippedDeps.length
              ? `\n\n_Could not be audited: ${skippedDeps.map((d) => `\`${d.name}\` (${d.skip_reason})`).join(', ')}_`
              : '');

            const banditSection = renderSection(
              'Bandit — HIGH-severity code issues',
              'bandit-report.json',
              (data) => (data.results || [])
                .filter((issue) => issue.issue_severity === 'HIGH')
                .map((issue) => `- \`${issue.test_name}\` in \`${issue.filename}:${issue.line_number}\``)
            );

            const semgrepSection = renderSection(
              'Semgrep — static analysis patterns',
              'semgrep-report.json',
              (data) => (data.results || []).map(
                (issue) => `- \`${issue.check_id}\` in \`${issue.path}:${issue.start?.line ?? '?'}\``
              )
            );

            const comment = [
              '# 🔒 Security Scan Results',
              '',
              pipAuditSection,
              '',
              banditSection,
              '',
              semgrepSection,
              '',
              '---',
              '',
              '*This security scan runs automatically on source-code PRs and bi-weekly (skipped for doc/markdown-only changes).*',
              '',
              '📊 **Security Policy**: CI fails on pip-audit vulnerabilities and Bandit HIGH-severity findings. Semgrep findings above are informational and do not block merge.',
            ].join('\n');

            try {
              await github.rest.issues.createComment({
                issue_number: context.issue.number,
                owner: context.repo.owner,
                repo: context.repo.repo,
                body: comment,
              });
              console.log('✅ Security comment posted successfully');
            } catch (error) {
              console.log('⚠️ Could not post security comment:', error.message);
              console.log('📋 Security scan results saved to artifacts');
            }

      - name: Enforce Audit Gate
        if: always()
        run: |
          if [ "${AUDIT_SCAN_STATUS:-failed}" != "passed" ]; then
            echo "::error::pip-audit scan failed. See the pip-audit output and uploaded reports above."
            exit 1
          fi