---
phase: 02-planning-threads
plan: 01
subsystem: api
tags: [drizzle, hono, sqlite, tdd, threads, candidates, transactions]

requires:
  - phase: 01-foundation-and-collection
    provides: items table, item.service.ts DI pattern, test helper, Hono route pattern
provides:
  - threads and threadCandidates database tables
  - Thread service with full CRUD and transactional resolution
  - Thread API routes at /api/threads with nested candidate endpoints
  - Zod validation schemas for threads, candidates, and resolution
  - Shared TypeScript types for Thread and ThreadCandidate
affects: [02-planning-threads, 03-setups-and-dashboard]

tech-stack:
  added: []
  patterns: [correlated SQL subqueries for aggregate metadata, transactional resolution pattern]

key-files:
  created:
    - src/server/services/thread.service.ts
    - src/server/routes/threads.ts
    - tests/services/thread.service.test.ts
    - tests/routes/threads.test.ts
  modified:
    - src/db/schema.ts
    - src/shared/schemas.ts
    - src/shared/types.ts
    - src/server/index.ts
    - tests/helpers/db.ts

key-decisions:
  - "Drizzle sql template literals use raw table.column references in correlated subqueries (not interpolated column objects)"
  - "Thread deletion collects candidate image filenames before cascade delete for filesystem cleanup"
  - "Resolution validates categoryId existence and falls back to Uncategorized (id=1)"

patterns-established:
  - "Correlated subquery pattern: raw SQL references in Drizzle sql`` for aggregate columns (candidateCount, minPrice, maxPrice)"
  - "Transaction pattern: resolveThread atomically creates item + archives thread in single db.transaction()"
  - "Nested route pattern: candidates CRUD mounted under /api/threads/:id/candidates"

requirements-completed: [THRD-01, THRD-02, THRD-03, THRD-04]

duration: 5min
completed: 2026-03-15
---

# Phase 2 Plan 01: Thread Backend API Summary

**Thread and candidate CRUD API with transactional resolution that atomically creates collection items from winning candidates using Drizzle transactions**

## Performance

- **Duration:** 5 min
- **Started:** 2026-03-15T10:34:32Z
- **Completed:** 2026-03-15T10:39:24Z
- **Tasks:** 2
- **Files modified:** 9

## Accomplishments
- Full thread CRUD (create, read, update, delete) with cascading candidate cleanup
- Full candidate CRUD with all item-compatible fields (name, weight, price, category, notes, productUrl, image)
- Thread list returns aggregate metadata (candidateCount, minPriceCents, maxPriceCents) via correlated subqueries
- Transactional thread resolution: atomically creates collection item from candidate data and archives thread
- 33 tests (19 unit + 14 integration) all passing with zero regressions on existing 30 Phase 1 tests

## Task Commits

Each task was committed atomically (TDD: RED then GREEN):

1. **Task 1: Schema, shared schemas, test helper, and service layer**
   - `e146eea` (test) - RED: failing tests for thread service
   - `1a8b91e` (feat) - GREEN: implement thread service
2. **Task 2: Thread API routes with integration tests**
   - `37c9999` (test) - RED: failing integration tests for thread routes
   - `add3e33` (feat) - GREEN: implement thread routes and mount

## Files Created/Modified
- `src/db/schema.ts` - Added threads and threadCandidates table definitions
- `src/shared/schemas.ts` - Added Zod schemas for thread/candidate/resolve validation
- `src/shared/types.ts` - Added Thread, ThreadCandidate, and related input types
- `src/server/services/thread.service.ts` - Thread and candidate business logic with resolution transaction
- `src/server/routes/threads.ts` - Hono API routes for threads and candidates
- `src/server/index.ts` - Mounted threadRoutes at /api/threads
- `tests/helpers/db.ts` - Added threads and thread_candidates table creation
- `tests/services/thread.service.test.ts` - 19 unit tests for thread service
- `tests/routes/threads.test.ts` - 14 integration tests for thread API

## Decisions Made
- Used raw SQL table.column references in Drizzle `sql` template literals for correlated subqueries (interpolated column objects bind as parameters, not column references)
- Thread deletion collects candidate image filenames before cascade delete to enable filesystem cleanup
- Resolution validates categoryId existence and falls back to Uncategorized (id=1) to handle deleted categories

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] Fixed correlated subquery column reference in getAllThreads**
- **Found during:** Task 1 (GREEN phase)
- **Issue:** Drizzle `sql` template literal with `${threads.id}` binds as a parameter value, not a SQL column reference, causing COUNT to return 1 instead of correct count
- **Fix:** Changed to raw SQL reference `threads.id` instead of interpolated `${threads.id}` in correlated subqueries
- **Files modified:** src/server/services/thread.service.ts
- **Verification:** candidateCount returns correct values in tests
- **Committed in:** 1a8b91e (Task 1 GREEN commit)

---

**Total deviations:** 1 auto-fixed (1 bug)
**Impact on plan:** Essential fix for correct aggregate metadata. No scope creep.

## Issues Encountered
None beyond the subquery fix documented above.

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- Thread API fully operational, ready for frontend consumption in Plan 02
- All endpoints follow established Phase 1 patterns (DI, Hono context, Zod validation)
- Test infrastructure updated to support threads in all future tests

---
*Phase: 02-planning-threads*
*Completed: 2026-03-15*

## Self-Check: PASSED

All 8 files verified present. All 4 commit hashes verified in git log.