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openspec/changes/enterprise-currency/proposal.md

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+# OpenSpec Change: enterprise-currency
+
+- **Change ID**: enterprise-currency
+- **Package**: `@suaveplan/currency`
+- **Category**: finance
+- **Target path**: `finance/currency/currency`
+- **Status**: PROPOSED
+- **Date**: 2026-04-24
+- **Reference spec**: `/mnt/s/web/suaveplan/enterprise/currency.md`
+
+---
+
+## Summary
+
+Deliver `@suaveplan/currency` on the genesis branch from scratch at enterprise quality. The package is a currency conversion engine with pluggable `CurrencyProvider` interface, TTL-based `RateCache`, automatic BFS cross-rate triangulation (shortest-path over the cached-rate graph), inverse-rate calculation, per-provider circuit breaker, `AbortSignal` cancellation, batch convert, and a `setVirtualRate` live-update API. Returns typed `ConversionResult` with provenance (`providerName`, `triangulatedThrough`). Ships two reference providers: `InMemoryProvider` and `createStaticProvider`.
+
+---
+
+## Current-state audit (genesis)
+
+Does not exist on genesis — fresh build.
+
+---
+
+## Available workspace deps on genesis
+
+| Package | Role |
+|---|---|
+| `@suaveplan/error` (`workspace:^`) | Typed `CURRENCY.*` error codes |
+| `@suaveplan/types` (`workspace:^`) | `LoggerLike`, `EventBusLike` |
+| `@suaveplan/events` (`workspace:^`) | Virtual-rate change events |
+| `@suaveplan/retry` (`workspace:^`) | Circuit-breaker + backoff |
+| `@suaveplan/logger` (`workspace:^`) | Structured logs |
+| `zod` (`catalog:forms`) | Options validation |
+| `@opentelemetry/api` (`catalog:observability`) | Spans + counters |
+| `tslib` (`catalog:build`) | Runtime helpers |
+
+Dev dep: `@suaveplan/money workspace:^` (for `MoneyLike` type in tests).
+
+---
+
+## Public API surface (from main branch enterprise spec)
+
+```ts
+class CurrencyConverter {
+  constructor(config: ConverterConfig)
+  convert(from: string, to: string, amount: MoneyLike | number, options?: ConvertOptions): Promise<ConversionResult>
+  convertAmount(from: string, to: string, amount: number, options?: ConvertOptions): Promise<ConversionResult>
+  convertBatch(requests: Array<{from: string; to: string; amount: number}>): Promise<ConversionResult[]>
+  setVirtualRate(symbol: string, rate: number): void
+  invalidateCache(from?: string, to?: string): void
+}
+
+class RateCache {
+  get(from: string, to: string): ExchangeRate | undefined
+  set(from: string, to: string, rate: ExchangeRate): void
+  prune(): void
+  invalidate(from?: string, to?: string): void
+}
+
+function createStaticProvider(rates: Record<string, Record<string, number>>): CurrencyProvider
+class InMemoryProvider implements CurrencyProvider { setRates(rates: ExchangeRate[]): void }
+
+interface ConversionResult {
+  amount: number
+  rate: number
+  inverseRate: number
+  rateAgeMs: number
+  providerName: string
+  triangulatedThrough: string[] | null
+}
+
+interface ConverterConfig {
+  providers: CurrencyProvider[]
+  defaultBase?: string
+  cacheTtlMs?: number
+  maxRetries?: number
+  logger?: LoggerLike
+}
+
+interface CurrencyProvider {
+  name: string
+  supportsFiat: boolean
+  supportsCrypto: boolean
+  fetchRates(options: RateFetchOptions): Promise<RateFetchResult>
+  isHealthy?(): boolean
+}
+```
+
+### Error codes
+
+```ts
+type CurrencyErrorCode =
+  | 'CURRENCY_PROVIDER_UNAVAILABLE'
+  | 'CURRENCY_UNSUPPORTED_PAIR'
+  | 'CURRENCY_TRIANGULATION_IMPOSSIBLE'
+  | 'CURRENCY_CONVERT_ABORTED'
+  | 'CURRENCY_INVALID_CONFIG'
+
+function registerCurrencyErrorCodes(): void
+```
+
+---
+
+## New additions for genesis
+
+- **BFS triangulation** in `src/engine/triangulate.ts`
+- **Circuit breaker** per provider in `src/engine/circuit-breaker.ts` using `@suaveplan/retry`
+- **`convertBatch`** — coalesces required rate fetches
+- **`setVirtualRate` + change events** via `@suaveplan/events`
+- **`AbortSignal` on `convert`**
+- **Zod schemas** for `ConverterConfig`, `ConvertOptions`
+- **OTel** spans per convert, cache-hit counter, triangulation-path histogram
+
+---
+
+## File layout
+
+```text
+finance/currency/currency/
+  package.json
+  tsconfig.json
+  vitest.config.ts
+  src/
+    index.ts
+    error-codes.ts
+    constants/index.ts
+    types/
+      currency.types.ts
+      currency.types.md
+    engine/
+      converter/
+        converter.ts
+        converter.md
+        converter.types.ts
+        converter.test.ts
+        index.ts
+      rate-cache/
+        rate-cache.ts
+        rate-cache.md
+        rate-cache.test.ts
+        index.ts
+      triangulate/
+        triangulate.ts
+        triangulate.md
+        triangulate.test.ts
+        index.ts
+      circuit-breaker/
+        circuit-breaker.ts
+        circuit-breaker.md
+        circuit-breaker.test.ts
+        index.ts
+    provider/
+      in-memory-provider/
+        in-memory-provider.ts
+        in-memory-provider.md
+        in-memory-provider.test.ts
+        index.ts
+      static-provider/
+        static-provider.ts
+        static-provider.md
+        static-provider.test.ts
+        index.ts
+  tests/
+    integration.test.ts
+    property.test.ts
+```
+
+---
+
+## Impact
+
+Downstream: `@suaveplan/currency-providers` (implements `CurrencyProvider`), `@suaveplan/money` (integration for `MoneyLike`).
+
+**Prerequisites on Verdaccio**: `@suaveplan/error`, `@suaveplan/types`, `@suaveplan/events`, `@suaveplan/retry`, `@suaveplan/logger`.

openspec/changes/enterprise-currency/tasks.md

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+# Tasks: enterprise-currency
+
+**Change ID**: enterprise-currency
+**Package**: `@suaveplan/currency`
+**Target path**: `finance/currency/currency`
+**Prerequisites on Verdaccio**: `@suaveplan/error`, `@suaveplan/types`, `@suaveplan/events`, `@suaveplan/retry`, `@suaveplan/logger`
+
+---
+
+## 0. Pre-flight (non-negotiable)
+
+- [ ] 0.1 Confirm clean working tree (`git status` reports nothing) and no in-flight worktrees with uncommitted work (`git worktree list` then `git status` in each)
+- [ ] 0.2 If any worktrees exist under `.claude/worktrees/`, account for each one: still-active agent, work-pending-merge, or stale-and-prune. Stale worktrees MUST be removed (`git worktree remove`) before opening a new one — code that has been lost twice on main is the failure mode this guards against.
+- [ ] 0.3 Confirm the package set in `MANIFEST.md` matches `find packages -maxdepth 3 -name package.json` count. Drift here means a prior change archived without regenerating the manifest.
+
+## 1. Scaffold
+
+- [ ] Create directory tree per `proposal.md`.
+- [ ] `package.json` at `0.1.0`, `"sideEffects": false`, exports `"."` + engine + provider subpaths.
+- [ ] Deps: workspace + catalog as listed.
+- [ ] DevDeps: `vitest catalog:testing`, `@vitest/coverage-istanbul catalog:testing`, `fast-check catalog:testing`, `@suaveplan/testing workspace:^`, `@suaveplan/money workspace:^`.
+- [ ] `tsconfig.json` extending `library.json`; `vitest.config.ts` with `createTestConfig()`.
+- [ ] Scripts: `lint`, `typecheck`, `test`, `test:coverage`, `build`, `docs:check`.
+
+## 2. Types and errors
+
+- [ ] Define all interfaces and Zod schemas (`ConverterConfigSchema`, `ConvertOptionsSchema`) in `src/types/currency.types.ts`.
+- [ ] Write `currency.types.md` (≥200 words, both examples, API reference).
+- [ ] `src/error-codes.ts`: five codes; `registerCurrencyErrorCodes()`; eager call.
+
+## 3. Rate cache
+
+- [ ] Implement `RateCache` in `src/engine/rate-cache/rate-cache.ts`:
+  - `get(from, to)` / `set(from, to, rate)` / `prune()` / `invalidate(from?, to?)`.
+  - TTL check on `get`; prune on set when cache exceeds 1000 entries.
+  - OTel counter `currency.cache_hits_total` / `currency.cache_misses_total`.
+- [ ] Write `rate-cache.test.ts`: TTL expiry, prune, invalidate, hit/miss tracking.
+- [ ] Write `rate-cache.md` (≥200 words).
+
+## 4. Triangulation
+
+- [ ] Implement BFS triangulation in `src/engine/triangulate/triangulate.ts`:
+  - `findPath(cache, from, to): string[] | null` — BFS over cached pairs to find shortest path; max 3 hops.
+  - `triangulateRate(cache, path): number` — multiply rates along path.
+- [ ] Write `triangulate.test.ts`: direct found; one-hop; two-hop; no path returns null; cycle avoidance.
+- [ ] Write `triangulate.md` (≥200 words).
+
+## 5. Circuit breaker
+
+- [ ] Implement per-provider `ProviderCircuitBreaker` in `src/engine/circuit-breaker/circuit-breaker.ts`:
+  - States: closed → open (after N consecutive failures) → half-open (after cooldown) → closed.
+  - `wrap(fn): Promise<T>` — skips call when open; re-tries in half-open.
+  - Uses `@suaveplan/retry` for backoff calculation.
+- [ ] Write `circuit-breaker.test.ts`: consecutive failures open circuit; cooldown half-open; success resets.
+- [ ] Write `circuit-breaker.md` (≥200 words).
+
+## 6. Providers
+
+- [ ] Implement `InMemoryProvider` and `createStaticProvider` in respective feature dirs.
+- [ ] Write unit tests + `.md` for each.
+
+## 7. CurrencyConverter
+
+- [ ] Implement `CurrencyConverter` in `src/engine/converter/converter.ts`:
+  - Constructor validates config via `ConverterConfigSchema`; calls `registerCurrencyErrorCodes()` eagerly.
+  - `convert(from, to, amount, options?)`:
+    1. Check cache; if hit, return without provider call.
+    2. For each provider (skip open circuit): call `fetchRates({ symbols: [to], base: from })`; on success cache result.
+    3. If no direct rate found: BFS triangulate from cache.
+    4. If still not found: throw `CURRENCY_TRIANGULATION_IMPOSSIBLE`.
+    5. Honour `AbortSignal` between each provider attempt.
+    6. Return `ConversionResult` with `providerName`, `triangulatedThrough`.
+    7. OTel span `currency.convert`; counter `currency.converts_total` with `{direct, triangulated}`.
+  - `convertBatch(requests)`: group by provider calls, execute, map results.
+  - `setVirtualRate(symbol, rate)`: update cache; emit `currency:rate:updated` event via `@suaveplan/events`.
+  - `invalidateCache(from?, to?)`: delegate to `RateCache`.
+- [ ] Write `converter.types.ts`.
+- [ ] Write `converter.test.ts` (≤500 lines): direct convert; cache hit; triangulation; AbortSignal; circuit breaker open; virtual rate; batch; all providers fail throws.
+- [ ] Write `converter.md` (≥200 words, simple + advanced, API reference).
+
+## 8. Integration + property tests
+
+- [ ] `tests/integration.test.ts`: three-provider fallback chain; circuit breaker in play; virtual rate update.
+- [ ] `tests/property.test.ts` (fast-check): `convert(from, to)` then `convert(to, from)` yields approximately inverse; `convertBatch` results equal individual converts.
+
+## 9. Docs + verify + publish
+
+- [ ] All `.md` per layout; root `README.md` with quick-start, provider guide, BFS triangulation explanation, API table.
+- [ ] `bunx turbo lint --filter=@suaveplan/currency` — zero errors.
+- [ ] `bunx turbo typecheck --filter=@suaveplan/currency` — zero errors.
+- [ ] `bunx turbo test --filter=@suaveplan/currency` — all pass.
+- [ ] `bunx turbo test:coverage --filter=@suaveplan/currency` — 100%.
+- [ ] `bun scripts/publish.ts --package @suaveplan/currency`.
+- [ ] Update `CLAUDE.md`; archive to `openspec/archive/2026-04-24-enterprise-currency/`.