Added Rates Service: Base, Coinbase, Composite

packages/stack/src/rates/rates-coinbase.ts

@@ -0,0 +1,156 @@
+import { Satoshis } from '@xocash/primitives';
+
+import { BaseRates, type RateOptions } from './base-rates.js';
+
+import { Memoizer } from '../utils/index.js';
+
+/**
+ * Represents a single market product (pair) on Coinbase Exchange.
+ */
+export interface CoinbaseProduct {
+  id: string;
+  base_currency: string;
+  quote_currency: string;
+  base_min_size: string;
+  base_max_size: string;
+  quote_increment: string;
+}
+
+/**
+ * Dependencies for RatesCoinbase.
+ */
+export type RatesCoinbaseDependencies = {
+  /**
+   * Base URL for Coinbase Exchange API (defaults to prod).
+   */
+  apiBaseUrl: string;
+
+  /**
+   * Optional cache instance for rate lookups.
+   */
+  cache: Memoizer;
+
+  /**
+   * Optional cache TTL for rate lookups.
+   */
+  cacheTTL: number;
+
+  /**
+   * Optional fetch-like function (e.g. global fetch) for HTTP calls.
+   */
+  fetch: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+};
+
+/**
+ * CoinbaseRates
+ *
+ * Implements BaseRates by calling Coinbase Exchange's public REST endpoints.
+ */
+export class RatesCoinbase extends BaseRates {
+  private apiBaseUrl: string;
+  private cache: Memoizer;
+  private cacheTTL: number;
+  private fetch: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+
+  private constructor(deps: Partial<RatesCoinbaseDependencies>) {
+    super();
+    this.apiBaseUrl = deps.apiBaseUrl ?? 'https://api.exchange.coinbase.com';
+    this.cache = deps.cache ?? new Memoizer();
+    this.cacheTTL = deps.cacheTTL ?? 60 * 1000;
+    this.fetch = deps.fetch ?? fetch.bind(globalThis);
+  }
+
+  /**
+   * Factory to create a CoinbaseRates instance.
+   */
+  public static from(
+    apiBaseUrl: string = 'https://api.exchange.coinbase.com',
+    cacheTTL: number = 60 * 1000,
+    fetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>,
+  ): RatesCoinbase {
+    const cache = new Memoizer();
+    return new RatesCoinbase({ apiBaseUrl, cache, cacheTTL, fetch });
+  }
+
+  /** No persistent connection to open. */
+  public async start(): Promise<void> {}
+
+  /** No persistent connection to close. */
+  public async stop(): Promise<void> {}
+
+  /**
+   * List all available market products (pairs).
+   */
+  public async listProducts(): Promise<CoinbaseProduct[]> {
+    const url = `${this.apiBaseUrl}/products`;
+    const res = await this.fetch(url);
+    if (!res.ok) {
+      throw new Error(`Failed to fetch products (${res.status}): ${res.statusText}`);
+    }
+    return (await res.json()) as CoinbaseProduct[];
+  }
+
+  /**
+   * Get the raw exchange rate for a currency pair.
+   */
+  public async getRate(
+    currency: string,
+    options?: Partial<RateOptions>,
+  ): Promise<number> {
+    const fetchPair = async (pair: string): Promise<number> => {
+      return await this.cache.get(pair, async () => {
+        const price = await this.fetchTickerPrice(pair);
+        this.cache.set(pair, price);
+        return price;
+      }, this.cacheTTL);
+    };
+
+    const direct = `${currency}-BCH`;
+    try {
+      const denominatorRate = await fetchPair(direct);
+      return 1 / denominatorRate;
+    } catch {
+      const inverse = `BCH-${currency}`;
+      const invPrice = await fetchPair(inverse);
+      return invPrice;
+    }
+  }
+
+  /**
+   * Convert an amount in a foreign currency to BCH.
+   */
+  public async toBCH(
+    amount: number,
+    fromCurrency: string,
+    options?: Partial<RateOptions>,
+  ): Promise<Satoshis> {
+    const rate = await this.getRate(fromCurrency, options);
+    return Satoshis.fromBCH(amount / rate);
+  }
+
+  /**
+   * Convert a BCH amount to a target currency.
+   */
+  public async fromBCH(
+    amount: Satoshis,
+    targetCurrency: string,
+    options?: Partial<RateOptions>,
+  ): Promise<number> {
+    const bchAmount = amount.toBCH();
+    const rate = await this.getRate(targetCurrency, options);
+    return bchAmount * rate;
+  }
+
+  /**
+   * Fetch the current ticker price for a given pair.
+   */
+  private async fetchTickerPrice(pair: string): Promise<number> {
+    const url = `${this.apiBaseUrl}/products/${pair}/ticker`;
+    const res = await this.fetch(url);
+    if (!res.ok) {
+      throw new Error(`Ticker API error (${res.status}): ${res.statusText}`);
+    }
+    const data = (await res.json()) as { price: string };
+    return parseFloat(data.price);
+  }
+}