# Task 013: Draft Assembly, Editor, And Generic Preview

Development description: Assemble section scaffolds into a canonical Markdown/MDX draft, provide versioned draft editing, and render a generic rich preview for editor review.

## Implementation Details

- Backend endpoints:
  - `POST /api/articles/{article_id}/draft/assemble`
  - `GET /api/articles/{article_id}/drafts`
  - `GET /api/articles/{article_id}/drafts/{draft_id}`
  - `PATCH /api/articles/{article_id}/drafts/{draft_id}`
- Markdown is the canonical editable draft format.
- Draft assembly includes:
  - Title.
  - Meta title.
  - Meta description.
  - Body Markdown/MDX.
  - FAQ block when applicable.
  - Visual placeholders.
  - Evidence references.
  - Unsupported claim warnings.
- Approval-relevant draft edits create new immutable versions.
- Frontend includes:
  - Draft editor.
  - Generic Markdown/MDX preview.
  - Version selector/history.
  - Unsupported-claim warnings near content.
- The preview is for editor UX and content-shape validation, not target-site build/runtime validation.

## Public Interface

- Editor assembles a draft after production artifacts are ready.
- Editor edits Markdown and metadata.
- Editor views a generic preview.

## Acceptance Criteria

- [x] TDD pre-requirement: before implementation, write one failing behavior test that assembles a draft from successful section scaffolds through the public API; proceed one draft behavior at a time and record evidence in `Result`.
- [x] Draft assembly includes all planned sections in order.
- [x] Draft includes metadata, FAQ, visual placeholders, evidence references, and unsupported claim warnings.
- [x] Draft version 1 is immutable after approval-relevant edits; edits create a new version.
- [x] Generic Markdown/MDX preview renders headings, links, tables, images/placeholders, and FAQ.
- [x] Editor can compare or select draft versions.
- [x] Draft assembly fails clearly if required section scaffolds are missing.

## Verification

- Run draft assembly API tests.
- Run frontend editor/preview tests.
- Run Docker Compose smoke flow from production artifacts to previewed draft.

## Result

- Status: Completed. Pre-requirement (RED) and implementation (GREEN) finished.
- TDD plan:
  1. Keep the original RED pre-requirement behavior test for `POST /api/articles/{article_id}/draft/assemble`.
  2. Extend backend integration coverage for draft assembly payload completeness, immutable versioning, missing scaffold conflict, unsupported warning propagation, and not-found paths.
  3. Implement backend drafts application layer and public routes for assemble/list/get/patch.
  4. Extend shared API contracts (OpenAPI + generated TS types).
  5. Implement frontend draft editor with version selector, compare summary, and generic markdown preview parser/renderer.
  6. Add frontend model tests for preview parsing and version comparison.
- Red evidence:
  - Pre-requirement test `apps/backend/tests/integration/test_draft_assembly_public_api.py::DraftAssemblyPublicApiTest::test_assemble_draft_from_successful_section_scaffolds` initially failed before implementation.
  - Observed RED error before implementation: `AssertionError: 201 != 404 : {"detail":"Not Found"}`.
- Green evidence:
  - `POST /api/articles/{article_id}/draft/assemble` implemented and returns `201` with canonical draft payload.
  - `GET /api/articles/{article_id}/drafts`, `GET /api/articles/{article_id}/drafts/{draft_id}`, and `PATCH /api/articles/{article_id}/drafts/{draft_id}` implemented and covered.
  - Immutable versioning verified: patch creates `v2+`, base draft remains unchanged.
  - Missing required successful section scaffolds returns clear `409`.
  - Frontend generic preview parser renders headings, links, tables, images/placeholders, and FAQ blocks.
  - Frontend editor supports version selection and compare summary.
- Refactor notes:
  - Added dedicated backend drafts service (`application/drafts.py`) and drafts route module to isolate draft logic from evidence/plan flows.
  - Extended `article_drafts` persistence model with canonical body and metadata lists (`faq_items`, placeholders, evidence refs, warnings, based_on_draft_id`) for explicit version snapshots.
- Verification output:
  - `PYTHONPATH=/private/tmp/pupline-backend-deps python3 -m unittest apps/backend/tests/integration/test_draft_assembly_public_api.py` -> OK (5 tests)
  - `PYTHONPATH=/private/tmp/pupline-backend-deps python3 -m unittest apps/backend/tests/integration/test_parallel_production_public_api.py` -> OK (6 tests)
  - `PYTHONPATH=/private/tmp/pupline-backend-deps python3 -m unittest apps/backend/tests/integration/test_evidence_matrix_public_api.py` -> OK (2 tests)
  - `node apps/frontend/tests/draft_editor.model.test.mjs` -> OK
  - `node apps/frontend/tests/article_detail.model.test.mjs` -> OK
  - `pnpm --dir apps/frontend typecheck` -> OK