name: Detect affected areas
description: >-
  Classify a PR's changed files into CI work lanes (python, frontend, site,
  scan, deps, mcp_catalog) so the orchestrator can conditionally call only
  the sub-workflows a PR can affect. Outputs are always "true" on push/dispatch
  events and fail open (everything "true") when the diff cannot be computed.

inputs:
  github-token:
    description: Token for the GitHub API (gh CLI). Pass secrets.AUTOFIX_BOT_PAT from the calling workflow.
    required: false
    default: ${{ github.token }}

outputs:
  python:
    description: Run Python tests / ruff / ty / windows-footguns.
    value: ${{ steps.classify.outputs.python }}
  frontend:
    description: Run the TypeScript testing matrix + desktop build.
    value: ${{ steps.classify.outputs.frontend }}
  docker_meta:
    description: Docker setup and meta files have changed.
    value: ${{ steps.classify.outputs.docker_meta }}
  site:
    description: Build the Docusaurus docs site.
    value: ${{ steps.classify.outputs.site }}
  scan:
    description: Run the supply-chain critical-pattern scanner.
    value: ${{ steps.classify.outputs.scan }}
  deps:
    description: Check pyproject.toml dependency upper bounds.
    value: ${{ steps.classify.outputs.deps }}
  npm_lock:
    description: Post/update the semantic package-lock.json diff PR comment.
    value: ${{ steps.classify.outputs.npm_lock }}
  mcp_catalog:
    description: Require MCP catalog security review label.
    value: ${{ steps.classify.outputs.mcp_catalog }}
  ci_review:
    description: Require CI-sensitive file review label.
    value: ${{ steps.classify.outputs.ci_review }}

runs:
  using: composite
  steps:
    - name: Classify changed files
      id: classify
      shell: bash
      env:
        # Fall back to the built-in read-only token when the caller passes an
        # empty value. Fork PRs get no repo secrets, so AUTOFIX_BOT_PAT is ""
        # there, and an input `default:` only applies when the input is omitted,
        # not when it's passed empty. Without this fallback the compare API
        # fails on forks and the classifier fails open (every lane forced on).
        GH_TOKEN: ${{ inputs.github-token || github.token }}
        REPO: ${{ github.repository }}
        EVENT_NAME: ${{ github.event_name }}
        BASE_SHA: ${{ github.event.pull_request.base.sha }}
        HEAD_SHA: ${{ github.event.pull_request.head.sha }}
      run: |
        set -euo pipefail

        # Only pull_request events are gated. Other events (push, release,
        # dispatch) leave CHANGED empty, so the classifier fails open and every
        # lane runs. Post-merge / on-demand validation is never weakened.
        if [ "$EVENT_NAME" = "pull_request" ]; then
          # Use the compare endpoint with the pinned base/head SHAs from the
          # event payload instead of the "current PR files" endpoint. The SHAs
          # are frozen at trigger time, so the file list is deterministic even
          # if the PR receives a new push between trigger and detect.
          #
          # Retried: a rate-limit blip or eventual-consistency 404 on a
          # freshly-pushed HEAD would otherwise silently fall open (all lanes
          # run — safe, but wasteful and it masks the API failure).
          #
          # `.files[]?` (null-safe): with --paginate, a PR more than 100
          # commits ahead of its merge-base paginates the compare, and pages
          # after the first carry `files: null` — bare `.files[]` makes jq
          # die with "cannot iterate over: null", which fails every retry
          # and forces the fail-open path (seen on stacked PRs). The full
          # file list (up to the API's 300-file cap) is on page one.
          CHANGED=""
          for i in 1 2 3; do
            if CHANGED="$(gh api \
              --paginate \
              "repos/${REPO}/compare/${BASE_SHA}...${HEAD_SHA}" \
              --jq '.files[]?.filename')"; then
              break
            fi
            if [ "$i" = 3 ]; then
              echo "::warning::compare API failed after 3 attempts — failing open (all lanes run)"
              CHANGED=""
              break
            fi
            echo "::warning::compare API failed (attempt $i); retrying in 10s"
            sleep 10
          done
        fi

        echo "Changed files:"
        printf '%s\n' "${CHANGED:-(none)}"
        printf '%s\n' "${CHANGED:-}" | python3 scripts/ci/classify_changes.py