updating documentation

documentation/api-development.md

@@ -83,6 +83,9 @@ touches the database. A service never reads `req.body`. A model never knows what
   model. Documented coupling acknowledged with a comment.
 - Problem 7: Gloss join could multiply question rows. Schema allowed multiple glosses per term per language, so the left join would duplicate rows. Fixed by tightening the unique constraint.
 - Problem 8: Model leaked quiz semantics. Return fields were named prompt / answer, baking HTTP-layer concepts into the database layer. Renamed to neutral field names.
+- Problem 9: AnswerResult wasn't self-contained. Frontend needed selectedOptionId to render feedback but the schema didn't include it (reasoning was "client already knows"). Discovered during frontend work; added the field.
+- Problem 10: Distractor could duplicate the correct answer text. Different terms can share the same translation. Fixed with ne(translations.text, excludeText) in the query.
+- Problem 11: TypeScript strict mode flagged Fisher-Yates shuffle array access. noUncheckedIndexedAccess treats result[i] as T | undefined. Fixed with non-null assertion and temp variable pattern.
 
 ---
 
@@ -116,6 +119,15 @@ touches the database. A service never reads `req.body`. A model never knows what
 - One gloss per term per language. The unique constraint on term_glosses was tightened from (term_id, language_code, text) to (term_id, language_code) to prevent the left join from multiplying question rows. Revisit if multiple glosses per language are ever needed (e.g. register or domain variants).
 - Model returns neutral field names, not quiz semantics. getGameTerms returns sourceText / targetText / sourceGloss rather than prompt / answer / gloss. Quiz semantics are applied in the service layer. Keeps the model reusable for non-quiz features.
 - Asymmetric difficulty filter. Difficulty is filtered on the target (answer) side only. A word can be A2 in Italian but B1 in English, and what matters is the difficulty of the word being learned.
+- optionId as integer 0-3, not UUID. Options only need uniqueness within a single question; cheating prevented by shuffling, not opaque IDs.
+- questionId and sessionId as UUIDs. Globally unique, opaque, natural Valkey keys when storage moves later.
+- gloss is string | null rather than optional, for predictable shape on the frontend.
+- GameSessionStore stores only the answer key (questionId → correctOptionId). Minimal payload for easy Valkey migration.
+- All GameSessionStore methods are async even for the in-memory implementation, so the service layer is already written for Valkey.
+- Distractors fetched per-question (N+1 queries). Correct shape for the problem; 10 queries on local Postgres is negligible latency.
+- No fallback logic for insufficient distractors. Data volumes are sufficient; strict query throws if something is genuinely broken.
+- Distractor query excludes both the correct term ID and the correct answer text, preventing duplicate options from different terms with the same translation.
+- Submit-before-send flow on frontend: user selects, then confirms. Prevents misclicks.
 
 ---
 
@@ -157,7 +169,7 @@ as a potential constraint for the distractor algorithm at high difficulty.
 
 ## API Schemas (packages/shared)
 
-### `GameRequestSchema` (implemented)
+### `GameRequestSchema`
 
 ```typescript
 {
@@ -169,14 +181,11 @@ as a potential constraint for the distractor algorithm at high difficulty.
 }
 ```
 
-### Planned schemas (not yet implemented)
-
-```text
-QuizQuestion      — prompt, optional gloss, 4 options (no correct answer)
-QuizOption        — optionId + text
-AnswerSubmission  — questionId + selectedOptionId
-AnswerResult      — correct boolean, correctOptionId, selectedOptionId
-```
+AnswerOption: { optionId: number (0-3), text: string }
+GameQuestion: { questionId: uuid, prompt: string, gloss: string | null, options: AnswerOption[4] }
+GameSession: { sessionId: uuid, questions: GameQuestion[] }
+AnswerSubmission: { sessionId: uuid, questionId: uuid, selectedOptionId: number (0-3) }
+AnswerResult: { questionId: uuid, isCorrect: boolean, correctOptionId: number (0-3), selectedOptionId: number (0-3) }
 
 ---
 
@@ -236,27 +245,36 @@ packages/db/src/
 - [x] Gloss left join implemented
 - [x] Model return type uses neutral field names (sourceText, targetText, sourceGloss)
 - [x] Schema: gloss unique constraint tightened to one gloss per term per language
+- [x] Zod schemas defined: AnswerOption, GameQuestion, GameSession, AnswerSubmission, AnswerResult
+- [x] getDistractors model implemented with POS/difficulty/language/excludeTermId/excludeText filters
+- [x] createGameSession service: fetches terms, fetches distractors per question, shuffles options, stores session, returns GameSession
+- [x] evaluateAnswer service: looks up session, compares submitted optionId to stored correct answer, returns AnswerResult
+- [x] GameSessionStore interface + InMemoryGameSessionStore (Map-backed, swappable to Valkey)
+- [x] POST /api/v1/game/answer endpoint wired (route, controller, service)
+- [x] selectedOptionId added to AnswerResult (discovered during frontend work)
+- [x] Minimal frontend: /play route with settings UI, QuestionCard, OptionButton, ScoreScreen
+- [x] Vite proxy configured for dev
 
 ---
 
 ## Roadmap Ahead
 
-### Step 1 — Learn SQL fundamentals (in progress)
+### Step 1 — Learn SQL fundamentals - done
 
 Concepts needed: SELECT, FROM, JOIN, WHERE, LIMIT.
 Resources: sqlzoo.net or Khan Academy SQL section.
 Required before: implementing the double join for source language prompt.
 
-### Step 2 — Complete the model layer
+### Step 2 — Complete the model layer - done
 
 - Double join on `translations` — once for source language (prompt), once for target language (answer)
 - `GlossModel.getGloss(termId, languageCode)` — fetch gloss if available
 
-### Step 3 — Define remaining Zod schemas
+### Step 3 — Define remaining Zod schemas - done
 
 - `QuizQuestion`, `QuizOption`, `AnswerSubmission`, `AnswerResult` in `packages/shared`
 
-### Step 4 — Complete the service layer
+### Step 4 — Complete the service layer - done
 
 - `QuizService.buildSession()` — assemble raw rows into `QuizQuestion[]`
   - Generate `questionId` per question
@@ -266,7 +284,7 @@ Required before: implementing the double join for source language prompt.
   - Shuffle options so correct answer is not always in same position
 - `QuizService.evaluateAnswer()` — validate correctness, return `AnswerResult`
 
-### Step 5 — Implement answer endpoint
+### Step 5 — Implement answer endpoint - done
 
 - `POST /api/v1/game/answer` route, controller, service method
 
@@ -295,10 +313,10 @@ Required before: implementing the double join for source language prompt.
 
 - **Distractor algorithm:** when Italian C2 has only 242 terms, should the difficulty
   filter fall back gracefully or return an error? Decision needed before implementing
-  `buildSession()`.
+  `buildSession()`. => resolved
 - **Session statefulness:** game loop is currently stateless (fetch all questions upfront).
-  Confirm this is still the intended MVP approach before building `buildSession()`.
+  Confirm this is still the intended MVP approach before building `buildSession()`. => resolved
 - **Glosses can leak answers:** some WordNet glosses contain the target-language
   word in the definition text (e.g. "Padre" appearing in the English gloss for
   "father"). Address during the post-MVP data enrichment pass — either clean the
-  glosses, replace them with custom definitions, or filter at the service layer.
+  glosses, replace them with custom definitions, or filter at the service layer. => resolved

documentation/roadmap.md

@@ -32,10 +32,10 @@ Done when: `GET /api/decks/1/terms?limit=10` returns 10 terms from a specific de
 [x] Write `scripts/build_decks.ts` (reads external CEFR lists, matches to DB, creates decks)
 [x] Run `pnpm db:seed` → populates terms
 [x] Run `pnpm db:build-deck` → creates curated decks
-[ ] Define Zod response schemas in `packages/shared`
-[ ] Implement `DeckRepository.getTerms(deckId, limit, offset)`
-[ ] Implement `QuizService.attachDistractors(terms)` — same POS, server-side, no duplicates
-[ ] Implement `GET /language-pairs`, `GET /decks`, `GET /decks/:id/terms` endpoints
+[x] Define Zod response schemas in `packages/shared`
+[x] Implement `DeckRepository.getTerms(deckId, limit, offset)`  => no decks needed anymore
+[x] Implement `QuizService.attachDistractors(terms)` — same POS, server-side, no duplicates
+[x] Implement `GET /language-pairs`, `GET /decks`, `GET /decks/:id/terms` endpoints => no language pairs, not needed anymore
 [ ] Unit tests for `QuizService` (correct POS filtering, never includes the answer)
 [ ] update decisions.md