name: Context Drift Check

# Detects structural degradation in CLAUDE.md on a weekly schedule.
# Opens a GitHub issue automatically when problems are found.
#
# Setup:
#   1. Copy this file to .github/workflows/context-drift.yml
#   2. Make sure canary-check.sh is committed and executable
#   3. Adjust the cron schedule and threshold values as needed
#
# The workflow checks:
#   - Structural validity (broken @imports, size, conflicts)
#   - CLAUDE.md size trend (warns when exceeding threshold)
#   - Broken @import references

on:
  schedule:
    - cron: '0 9 * * 1'   # Every Monday at 9:00 AM UTC
  workflow_dispatch:        # Allow manual trigger from GitHub UI
    inputs:
      project_dir:
        description: 'Project directory to check (relative to repo root)'
        required: false
        default: '.'

env:
  # Customize these thresholds for your project
  CLAUDE_MD_MAX_LINES: 500
  CLAUDE_MD_WARN_LINES: 400

jobs:
  drift-check:
    name: Check CLAUDE.md for drift
    runs-on: ubuntu-latest
    permissions:
      contents: read
      issues: write       # Required to open issues on failure

    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          fetch-depth: 0   # Full history needed for git log checks

      - name: Make canary script executable
        run: chmod +x ./examples/context-engineering/canary-check.sh

      - name: Run structural canary checks
        id: canary
        run: |
          PROJECT_DIR="${{ github.event.inputs.project_dir || '.' }}"
          ./examples/context-engineering/canary-check.sh "$PROJECT_DIR"
        continue-on-error: true  # Capture exit code without stopping workflow

      - name: Check CLAUDE.md size against thresholds
        id: size_check
        run: |
          FILE="CLAUDE.md"
          if [ ! -f "$FILE" ]; then
            echo "::warning::CLAUDE.md not found at repo root"
            exit 0
          fi

          CURRENT=$(wc -l < "$FILE" | tr -d ' ')
          echo "current_lines=$CURRENT" >> "$GITHUB_OUTPUT"

          if [ "$CURRENT" -gt "$CLAUDE_MD_MAX_LINES" ]; then
            echo "::error::CLAUDE.md has $CURRENT lines (max: $CLAUDE_MD_MAX_LINES). Consider modularizing with @imports."
            echo "size_status=fail" >> "$GITHUB_OUTPUT"
          elif [ "$CURRENT" -gt "$CLAUDE_MD_WARN_LINES" ]; then
            echo "::warning::CLAUDE.md has $CURRENT lines (warn threshold: $CLAUDE_MD_WARN_LINES). Getting large."
            echo "size_status=warn" >> "$GITHUB_OUTPUT"
          else
            echo "CLAUDE.md size: $CURRENT lines (OK)"
            echo "size_status=ok" >> "$GITHUB_OUTPUT"
          fi

      - name: Check for stale @imports
        id: import_check
        run: |
          FILE="CLAUDE.md"
          if [ ! -f "$FILE" ]; then
            exit 0
          fi

          BROKEN=0
          while IFS= read -r line; do
            if [[ "$line" =~ ^@([^[:space:]].+)$ ]]; then
              IMPORT="${BASH_REMATCH[1]}"
              if [ ! -f "$IMPORT" ]; then
                echo "::error::Broken @import in CLAUDE.md: @$IMPORT"
                BROKEN=$((BROKEN + 1))
              fi
            fi
          done < "$FILE"

          echo "broken_imports=$BROKEN" >> "$GITHUB_OUTPUT"

          if [ "$BROKEN" -gt 0 ]; then
            echo "::error::Found $BROKEN broken @import(s) in CLAUDE.md"
          else
            echo "All @imports resolve correctly"
          fi

      - name: Check CLAUDE.md is git-tracked and recent
        id: freshness_check
        run: |
          FILE="CLAUDE.md"
          if [ ! -f "$FILE" ]; then
            exit 0
          fi

          # Check if tracked
          if ! git ls-files --error-unmatch "$FILE" > /dev/null 2>&1; then
            echo "::warning::CLAUDE.md is not tracked in git"
            exit 0
          fi

          # Get days since last update
          LAST_COMMIT_DATE=$(git log -1 --format="%cd" --date=format:"%Y-%m-%d" -- "$FILE")
          TODAY=$(date +%Y-%m-%d)
          DAYS_OLD=$(( ($(date -d "$TODAY" +%s 2>/dev/null || date -j -f "%Y-%m-%d" "$TODAY" +%s) - $(date -d "$LAST_COMMIT_DATE" +%s 2>/dev/null || date -j -f "%Y-%m-%d" "$LAST_COMMIT_DATE" +%s)) / 86400 ))

          echo "days_old=$DAYS_OLD" >> "$GITHUB_OUTPUT"
          echo "last_updated=$LAST_COMMIT_DATE" >> "$GITHUB_OUTPUT"

          if [ "$DAYS_OLD" -gt 90 ]; then
            echo "::warning::CLAUDE.md was last updated $DAYS_OLD days ago ($LAST_COMMIT_DATE). Consider reviewing for stale rules."
          else
            echo "CLAUDE.md freshness: last updated $DAYS_OLD days ago ($LAST_COMMIT_DATE) — OK"
          fi

      - name: Collect check results
        id: summary
        if: always()
        run: |
          CANARY_STATUS="${{ steps.canary.outcome }}"
          BROKEN_IMPORTS="${{ steps.import_check.outputs.broken_imports || 0 }}"
          SIZE_STATUS="${{ steps.size_check.outputs.size_status || 'ok' }}"
          CURRENT_LINES="${{ steps.size_check.outputs.current_lines || 0 }}"
          DAYS_OLD="${{ steps.freshness_check.outputs.days_old || 0 }}"
          LAST_UPDATED="${{ steps.freshness_check.outputs.last_updated || 'unknown' }}"

          ISSUES=0
          [ "$CANARY_STATUS" = "failure" ] && ISSUES=$((ISSUES + 1))
          [ "$BROKEN_IMPORTS" -gt 0 ] && ISSUES=$((ISSUES + BROKEN_IMPORTS))
          [ "$SIZE_STATUS" = "fail" ] && ISSUES=$((ISSUES + 1))

          echo "total_issues=$ISSUES" >> "$GITHUB_OUTPUT"
          echo "summary_lines=$CURRENT_LINES" >> "$GITHUB_OUTPUT"
          echo "summary_days=$DAYS_OLD" >> "$GITHUB_OUTPUT"
          echo "summary_updated=$LAST_UPDATED" >> "$GITHUB_OUTPUT"

      - name: Open issue on failure
        if: always() && steps.summary.outputs.total_issues > 0
        uses: actions/github-script@v7
        with:
          script: |
            const issues = parseInt('${{ steps.summary.outputs.total_issues }}');
            const lines = '${{ steps.summary.outputs.summary_lines }}';
            const daysOld = '${{ steps.summary.outputs.summary_days }}';
            const lastUpdated = '${{ steps.summary.outputs.summary_updated }}';
            const runUrl = `${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}`;

            // Check if there's already an open issue for drift
            const openIssues = await github.rest.issues.listForRepo({
              owner: context.repo.owner,
              repo: context.repo.repo,
              labels: 'ai-context,maintenance',
              state: 'open',
            });

            if (openIssues.data.length > 0) {
              // Add a comment to the existing issue instead of opening a new one
              const existingIssue = openIssues.data[0];
              await github.rest.issues.createComment({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: existingIssue.number,
                body: `Weekly check still finding issues (${issues} problem(s)).\n\nRun: ${runUrl}\nCLAUDE.md: ${lines} lines, last updated: ${lastUpdated} (${daysOld} days ago)`,
              });
            } else {
              await github.rest.issues.create({
                owner: context.repo.owner,
                repo: context.repo.repo,
                title: `Context Drift Detected — CLAUDE.md needs review`,
                body: [
                  `The weekly context drift check found **${issues} problem(s)** in \`CLAUDE.md\`.`,
                  ``,
                  `## Details`,
                  `- File size: ${lines} lines`,
                  `- Last updated: ${lastUpdated} (${daysOld} days ago)`,
                  `- Workflow run: ${runUrl}`,
                  ``,
                  `## Action Required`,
                  `1. Review the workflow logs for specific issues`,
                  `2. Run \`./examples/context-engineering/canary-check.sh .\` locally for details`,
                  `3. Fix broken @imports, reduce file size, or update stale rules`,
                  `4. Close this issue once CLAUDE.md is back in good shape`,
                  ``,
                  `_This issue was opened automatically by the context drift check workflow._`,
                ].join('\n'),
                labels: ['ai-context', 'maintenance'],
              });
            }

      - name: Final status
        if: always()
        run: |
          ISSUES="${{ steps.summary.outputs.total_issues }}"
          if [ "$ISSUES" -gt 0 ]; then
            echo "Context drift check: FAILED ($ISSUES issues)"
            exit 1
          else
            echo "Context drift check: PASSED"
          fi