# agent-context drift detection
#
# Weekly + on-demand check: does this repo's installed agent-pipeline
# artifacts match the latest upstream pipeline release?
#
# - Reads .agent-context-manifest.yml (committed at repo root)
# - Clones the pipeline repo at its latest tag
# - Compares each tracked artifact's installed_hash to the pipeline source hash
# - Compares manifest pipeline_version to pipeline version.txt
# - Opens (or updates) an issue titled "agent-context: N files behind v<X>"
#   if drift is detected
#
# No auto-fix. The fix workflow is: a human runs `sync-agent-context` in
# Cursor and reviews per-file diffs.

name: agent-context-drift

on:
  schedule:
    # Mondays at 13:00 UTC. Adjust to taste.
    - cron: "0 13 * * 1"
  workflow_dispatch:

permissions:
  contents: read
  issues: write

jobs:
  drift:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout consumer repo
        uses: actions/checkout@v4

      - name: Read manifest
        id: manifest
        run: |
          if [ ! -f .agent-context-manifest.yml ]; then
            echo "::warning::No .agent-context-manifest.yml — agent-pipeline not installed or pre-v0.3.0. Skipping drift check."
            echo "skip=true" >> "$GITHUB_OUTPUT"
            exit 0
          fi
          INSTALLED=$(grep -E '^pipeline_version:' .agent-context-manifest.yml | head -1 | sed -E 's/.*"(.*)".*/\1/')
          SOURCE=$(grep -E '^pipeline_source:' .agent-context-manifest.yml | head -1 | sed -E 's/.*"(.*)".*/\1/')
          echo "installed_version=$INSTALLED" >> "$GITHUB_OUTPUT"
          echo "pipeline_source=$SOURCE" >> "$GITHUB_OUTPUT"
          echo "skip=false" >> "$GITHUB_OUTPUT"

      - name: Clone pipeline at latest tag
        if: steps.manifest.outputs.skip != 'true'
        id: pipeline
        run: |
          PIPELINE_URL="${{ steps.manifest.outputs.pipeline_source }}"
          # Convert HTTPS URL → clone target. Already in HTTPS form.
          mkdir -p /tmp/pipeline
          git clone --depth 50 "$PIPELINE_URL" /tmp/pipeline
          cd /tmp/pipeline
          LATEST_TAG=$(git tag --sort=-v:refname | head -1)
          if [ -z "$LATEST_TAG" ]; then
            echo "::warning::Pipeline repo has no tags. Comparing against main."
            LATEST_TAG="main"
          fi
          git checkout "$LATEST_TAG"
          PIPELINE_VER=$(cat version.txt | tr -d '[:space:]')
          echo "tag=$LATEST_TAG" >> "$GITHUB_OUTPUT"
          echo "version=$PIPELINE_VER" >> "$GITHUB_OUTPUT"

      - name: Compute drift
        if: steps.manifest.outputs.skip != 'true'
        id: drift
        run: |
          INSTALLED="${{ steps.manifest.outputs.installed_version }}"
          UPSTREAM="${{ steps.pipeline.outputs.version }}"
          BEHIND=0
          CUSTOMIZED=0
          CONFLICT=0

          # Walk manifest artifacts. For each, compare installed_hash to local
          # current hash, and pipeline source hash to installed_hash.
          # YAML parsing in bash is intentionally minimal — relies on the
          # bootstrap skill emitting a predictable shape.
          python3 - <<'PY' >> drift-report.md
          import hashlib, sys, yaml, os

          def sha(path):
              if not os.path.exists(path):
                  return None
              h = hashlib.sha256()
              with open(path, "rb") as f:
                  for chunk in iter(lambda: f.read(8192), b""):
                      h.update(chunk)
              return "sha256:" + h.hexdigest()

          with open(".agent-context-manifest.yml") as f:
              m = yaml.safe_load(f)

          counts = {"behind": [], "customized": [], "conflict": [], "deleted": []}
          for art in m.get("artifacts", []):
              local_hash = sha(art["path"])
              pipe_hash = sha(os.path.join("/tmp/pipeline", art["source"]))
              if local_hash is None:
                  counts["deleted"].append(art["path"])
                  continue
              local_matches = local_hash == art["installed_hash"]
              pipe_changed = pipe_hash is not None and pipe_hash != art["installed_hash"]
              if local_matches and pipe_changed:
                  counts["behind"].append(art["path"])
              elif not local_matches and pipe_changed:
                  counts["conflict"].append(art["path"])
              elif not local_matches:
                  counts["customized"].append(art["path"])

          print("# agent-context drift report")
          print(f"\nInstalled: `{m.get('pipeline_version')}` · Upstream: `${{ steps.pipeline.outputs.version }}` (`${{ steps.pipeline.outputs.tag }}`)")
          for kind in ("behind", "conflict", "customized", "deleted"):
              files = counts[kind]
              if files:
                  print(f"\n## {kind} ({len(files)})")
                  for f in files:
                      print(f"- `{f}`")
          PY

          BEHIND=$(grep -c '^## behind' drift-report.md || echo 0)
          CONFLICT=$(grep -c '^## conflict' drift-report.md || echo 0)
          NEED_ISSUE="false"
          if [ "$INSTALLED" != "$UPSTREAM" ] || [ "$BEHIND" -gt 0 ] || [ "$CONFLICT" -gt 0 ]; then
            NEED_ISSUE="true"
          fi
          echo "need_issue=$NEED_ISSUE" >> "$GITHUB_OUTPUT"
          echo "upstream_version=$UPSTREAM" >> "$GITHUB_OUTPUT"

      - name: Open / update drift issue
        if: steps.manifest.outputs.skip != 'true' && steps.drift.outputs.need_issue == 'true'
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const body = fs.readFileSync('drift-report.md', 'utf8') +
              '\n\n---\n\n_To resolve: open this repo in Cursor and ask **"Sync agent context for this repo"**. The sync skill walks the diff per file._';
            const title = `agent-context: behind ${{ steps.drift.outputs.upstream_version }}`;
            const existing = await github.rest.issues.listForRepo({
              owner: context.repo.owner,
              repo: context.repo.repo,
              state: 'open',
              labels: 'agent-context-drift',
            });
            const found = existing.data.find(i => i.title.startsWith('agent-context: behind'));
            if (found) {
              await github.rest.issues.update({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: found.number,
                title,
                body,
              });
            } else {
              await github.rest.issues.create({
                owner: context.repo.owner,
                repo: context.repo.repo,
                title,
                body,
                labels: ['agent-context-drift'],
              });
            }