# Implementation Plan: Syntax Clarity & Parser Robustness

Status: **In progress — Phases 1, 2, 3 & 4 applied** (Phases 5–6 not yet done)

## Goals

1. Eliminate the backtracking heuristics in the value parser by making the value grammar context-free.
2. Remove redundant/ambiguous syntax forms.
3. Make union resolution deterministic and structural (not error-message-driven).
4. Address the `csv-parse` quote conflict.
5. Keep the `;` separator (forced by CSV constraints — not the source of ambiguity).

All changes are **breaking** to the DSL → bump to `2.0.0`, update README + `csv-loader.md`, add a migration note.

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## Phase 1 — Mandatory brackets for composite values ✅ Applied

**Files:** `src/value-parser.ts`, `src/index.test.ts`, `src/csv-loader/reference-resolver.ts`

- Removed the `allowOmitBrackets` parameter from `parseValue`, `parseTupleValue`, `parseArrayValue`.
- Deleted the `elementIsTupleOrArray` disambiguation block and all `savedPos` restore logic in `parseArrayValue`.
- Dropped the `allowOmitBrackets = schema.type === "tuple" || "array"` special case in top-level `parseValue` — brackets are always required.
- Array references (`@table[]` values) now also require brackets, for consistency.
- Values must now be fully bracketed: `[a; 1]; [b; 2]` (no more `[a; 1]; [b; 2]` without outer brackets).

**Decision:** Full mandatory brackets (no carve-out).

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## Phase 2 — Single array form `Type[]` ✅ Applied

**Files:** `src/parser.ts`, `src/index.test.ts`

- Removed the `[Type][]` array syntax from `parseSchemaInternal`. Kept only `Type[]`.
- `[string]` is now a **1-tuple** (previously it collapsed to an array). The tuple branch always returns `{ type: "tuple", elements }`.
- Updated `schemaToTypeString` in `src/type-utils.ts` — the `array` case no longer special-cases tuple elements; arrays are always `elementType[]` (kept the `(union)[]` paren wrapping).

**Tests updated:** `index.test.ts` bracket-optional tests, `encounter.csv` / `enemy_intents.csv` fixtures, and `parseCsv-typeDeclarations.test.ts` array-of-tuple values.

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## Phase 3 — Deterministic union resolution ✅ Applied

**Files:** `src/csv-loader/reference-resolver.ts`, `src/csv-loader/module-gen.ts`

- **Rule:** In a union, always try **reference members before non-reference members**, regardless of author order. This makes fallback structural instead of error-message-driven.
- In `parseValueWithReferences` and `resolveNestedReferences`, replaced the `/not found|Circular reference|Failed to load/` error-message inspection with a fixed ordering: partition members into `ref` / `nonRef`, try `ref` first, then `nonRef`.
- `module-gen.ts` `generateSchemaResolutionCode` already emitted reference-first (`lookup.get(...) ?? value`), so runtime now matches generated code.
- **Documented the rule** in README and AGENTS.md.

**Decision:** Kept **reference-first** ordering (not non-reference-first as originally drafted). Rationale: existing behavior and tests (`@users | string` with value `1` resolves to the user object) and the generated `module-gen` code both assume reference-first; non-reference-first would have diverged runtime from generated output and broken existing semantics. The plan's real goal — removing the error-message regex — is achieved.

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## Phase 4 — Quote conflict resolution ✅ Applied

**Files:** `src/csv-loader/loader.ts`, `src/csv-loader/tests/parseCsv-basic.test.ts`, README, `csv-loader.md`

- Added `escapeSchemaRowQuotes()` in `loader.ts`: the schema row (2nd non-empty line) is split on the delimiter, and any cell containing the quote char has its inner quotes escaped and is wrapped in quotes before `csv-parse` runs.
- This lets users write `"active" | "inactive"` naturally in a schema row — previously csv-parse threw `Invalid Closing Quote`.
- Single-quoted literals (`'on' | 'off'`) are untouched (no `"` present).
- Added a test in `parseCsv-basic.test.ts`.

**Decision:** Implemented option (b) — loader-side escaping of the schema row. This fixes the root cause (schema cells containing `"` break csv-parse) without redesigning the literal syntax.

**Known limitation (pre-existing, out of scope):** a comma inside a string literal (e.g. `"a,b"`) is ambiguous with the CSV delimiter and still fails — use single-quoted literals (`'a,b'`) for those, or a non-comma delimiter.

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## Phase 5 — Cleanup & consistency

**Files:** `src/csv-loader/reference-resolver.ts`, `src/csv-loader/loader.ts`, `src/csv-loader/module-gen.ts`

- **Reverse-reference performance:** `resolveReverseReference` does `refTable.filter(...)` per row. Build a `Map<fk, rows[]>` lookup once per referenced table (mirroring what `module-gen.ts` already generates) and reuse it. Cache the lookup alongside the parsed table in `referenceTableCache`.
- **Remove the `,` stop-character in `parseReferenceValue`** (value parser has a `,` stop char the schema parser doesn't — drift). Make reference ID parsing consistent with the rest of the value grammar.
- **`int`/`float`/`number` → `number`:** document the collapse in README (type-level collapse is intentional; parse-time distinction remains).

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## Phase 6 — Docs & migration

**Files:** `README.md`, `csv-loader.md`, `AGENTS.md`

- Update all syntax tables and examples for mandatory brackets + single array form.
- Add a **Migration section** listing the breaking changes:
  1. Composite values must be fully bracketed.
  2. `[Type][]` array form removed — use `Type[]`.
  3. `[single]` is now a 1-tuple, not an array.
  4. Union resolution now prefers reference members (tried before non-reference members).
  5. (If Phase 4b) schema cells may be fully quoted.
- Update `AGENTS.md` gotchas: union ordering rule, quote handling.

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## Validation

- `npm run typecheck`
- `npm run test` (update `src/index.test.ts`, `src/csv-loader/*.test.ts` first)
- Manually verify the integration fixture (`user_rev.csv` / `order_rev.csv`) still resolves.

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## Suggested execution order

Phases 1 → 2 are tightly coupled (both touch bracket parsing) — do them together. Phase 3 is independent. Phase 4 is independent. Phases 5–6 are cleanup/docs and can go last.