updating documentation

documentation/decisions.md

@@ -178,60 +178,55 @@ Most tables omit `updated_at` (unnecessary for MVP). `rooms.updated_at` is kept
 
 Allows multiple synonyms per language per term (e.g. "dog", "hound" for same synset). Prevents exact duplicate rows. Homonyms (e.g. "Lead" metal vs. "Lead" guide) are handled by different `term_id` values (different synsets), so no constraint conflict.
 
-### Decks: `pair_id` is nullable
+### Decks: `source_language` + `validated_languages` (not `pair_id`)
 
-`decks.pair_id` references `language_pairs` but is nullable. Reasons:
+**Original approach:** `decks.pair_id` references `language_pairs`, tying each deck to a single language pair.
 
-- Single-language decks (e.g. "English Grammar")
-- Multi-pair decks (e.g. "Cognates" spanning EN-IT and EN-FR)
-- System decks (created by app, not tied to specific user)
-
-### Decks separate from terms (not frequency_rank filtering)
-
-**Original approach:** Store `frequency_rank` on `terms` table and filter by rank range for difficulty.
-
-**Problem discovered:** WordNet/OMW frequency data is unreliable for language learning. Extraction produced results like:
-
-- Rank 1: "In" → "indio" (chemical symbol: Indium)
-- Rank 2: "Be" → "berillio" (chemical symbol: Beryllium)
-- Rank 7: "He" → "elio" (chemical symbol: Helium)
-
-These are technically "common" in WordNet (every element is a noun) but useless for vocabulary learning.
+**Problem:** One deck can serve multiple target languages as long as translations exist for all its terms. A `pair_id` FK would require duplicating the deck for each target language.
 
 **Decision:**
 
-- `terms` table stores ALL available OMW synsets (raw data, no frequency filtering)
-- `decks` table stores curated learning lists (A1, A2, B1, "Most Common 1000", etc.)
-- `deck_terms` junction table links terms to decks with position ordering
-- `rooms.deck_id` specifies which vocabulary deck a game uses
+- `decks.source_language` — the language the wordlist was curated from (e.g. `"en"`). A deck sourced from an English frequency list is fundamentally different from one sourced from an Italian list.
+- `decks.validated_languages` — array of language codes (excluding `source_language`) for which full translation coverage exists across all terms in the deck. Recalculated and updated on every run of the generation script.
+- The language pair used for a quiz session is determined at session start, not at deck creation time.
 
 **Benefits:**
 
-- Curricula can come from external sources (CEFR lists, Oxford 3000, SUBTLEX)
-- Bad data (chemical symbols, obscure words) excluded at deck level, not schema level
-- Users can create custom decks later
-- Multiple difficulty levels without schema changes
+- One deck serves multiple target languages (e.g. en→it and en→fr) without duplication
+- `validated_languages` stays accurate as translation data grows
+- DB enforces via CHECK constraint that `source_language` is never included in `validated_languages`
 
 ---
 
 ## Current State
 
-### Completed checkboxes (Phase 0)
+Phase 0 complete. Phase 1 data pipeline complete.
 
-- [x] Initialise pnpm workspace monorepo: `apps/web`, `apps/api`, `packages/shared`, `packages/db`
-- [x] Configure TypeScript project references across packages
-- [x] Set up ESLint + Prettier with shared configs in root
-- [x] Set up Vitest in `api` and `web` and both packages
-- [x] Scaffold Express app with `GET /api/health`
-- [x] Scaffold Vite + React app with TanStack Router (single root route)
-- [x] Configure Drizzle ORM + connection to local PostgreSQL
-- [x] Write first migration (empty — just validates the pipeline works)
-- [x] `docker-compose.yml` for local dev: `api`, `web`, `postgres`, `valkey`
-- [x] `.env.example` files for `apps/api` and `apps/web`
-- [x] update decisions.md
+### Completed (Phase 1 — data pipeline)
 
-Phase 0 is finished with this.
+- [x] Run `extract-en-it-nouns.py` locally → generates `datafiles/en-it-nouns.json`
+- [x] Write Drizzle schema: `terms`, `translations`, `language_pairs`, `term_glosses`, `decks`, `deck_terms`
+- [x] Write and run migration (includes CHECK constraints for `pos`, `gloss_type`)
+- [x] Write `packages/db/src/seed.ts` (imports ALL terms + translations, NO decks)
+- [x] Write `packages/db/src/generating-decks.ts` — idempotent deck generation script
+  - reads and deduplicates source wordlist
+  - matches words to DB terms (homonyms included)
+  - writes unmatched words to `-missing` file
+  - determines `validated_languages` by checking full translation coverage per language
+  - creates deck if it doesn't exist, adds only missing terms on subsequent runs
+  - recalculates and persists `validated_languages` on every run
 
-### Current checkpoint
+### Known data facts
 
-- [ ] Run `scripts/extract_omw.py` locally → generates `packages/db/src/seed.json`
+- Wordlist: 999 unique words after deduplication (1000 lines, 1 duplicate)
+- Term IDs resolved: 3171 (higher than word count due to homonyms)
+- Words not found in DB: 34
+- Italian (`it`) coverage: 3171 / 3171 — full coverage, included in `validated_languages`
+
+### Next (Phase 1 — API layer)
+
+- [ ] Define Zod response schemas in `packages/shared`
+- [ ] Implement `DeckRepository.getTerms(deckId, limit, offset)`
+- [ ] Implement `QuizService.attachDistractors(terms)`
+- [ ] Implement `GET /language-pairs`, `GET /decks`, `GET /decks/:id/terms` endpoints
+- [ ] Unit tests for `QuizService`