Add oracle rates

src/services/rates.ts

@@ -0,0 +1,197 @@
+import { EventEmitter } from '../utils/event-emitter.js';
+import {
+  type RatesEventMap,
+} from '../utils/rates/base-rates.js';
+import { RatesOracle } from '../utils/rates/rates-oracles.js';
+
+/**
+ * Event map emitted by {@link RatesService}.
+ */
+export type RatesServiceEventMap = {
+  'rate-updated': {
+    numeratorUnitCode: string;
+    denominatorUnitCode: string;
+    price: number;
+    pair: string;
+    updatedAt: number;
+  };
+};
+
+/**
+ * In-memory representation of a market rate.
+ */
+type CachedRate = {
+  price: number;
+  updatedAt: number;
+};
+
+/**
+ * Minimal adapter contract that RatesService depends on.
+ *
+ * Using a small interface keeps the service decoupled and avoids inheriting
+ * implementation-specific type constraints from concrete adapters.
+ */
+export interface RatesAdapter {
+  start(): Promise<void>;
+  stop(): Promise<void>;
+  listPairs(): Promise<Set<string>>;
+  formatCurrency(amount: number, targetCurrency: string): string;
+  on(
+    type: 'rateUpdated',
+    listener: (detail: RatesEventMap['rateUpdated']) => void,
+  ): () => void;
+}
+
+/**
+ * Orchestrates the rates adapter lifecycle and provides BCH -> fiat helpers
+ * for the TUI.
+ *
+ * This service keeps a small in-memory snapshot of the latest prices and emits
+ * a normalized event whenever a pair changes. React components can subscribe
+ * through `useSyncExternalStore` for clean and predictable reactivity.
+ */
+export class RatesService extends EventEmitter<RatesServiceEventMap> {
+  private readonly adapter: RatesAdapter;
+  private readonly ratesByPair = new Map<string, CachedRate>();
+  private unsubscribeFromAdapter: (() => void) | null = null;
+  private started = false;
+
+  private constructor(adapter: RatesAdapter) {
+    super();
+    this.adapter = adapter;
+  }
+
+  /**
+   * Creates a rates service.
+   *
+   * If no adapter is passed, this defaults to the Oracle-backed adapter.
+   */
+  public static async create(adapter?: RatesAdapter): Promise<RatesService> {
+    const resolvedAdapter = adapter ?? (await RatesOracle.from());
+    return new RatesService(resolvedAdapter);
+  }
+
+  /**
+   * Starts the underlying adapter and begins collecting live updates.
+   */
+  public async start(): Promise<void> {
+    if (this.started) {
+      return;
+    }
+    this.started = true;
+
+    this.unsubscribeFromAdapter = this.adapter.on('rateUpdated', (event) => {
+      this.handleRateUpdated(event);
+    });
+
+    try {
+      await this.adapter.start();
+    } catch (error) {
+      this.unsubscribeFromAdapter?.();
+      this.unsubscribeFromAdapter = null;
+      this.started = false;
+      throw error;
+    }
+  }
+
+  /**
+   * Stops live rate collection.
+   */
+  public async stop(): Promise<void> {
+    if (!this.started) {
+      return;
+    }
+    this.started = false;
+
+    this.unsubscribeFromAdapter?.();
+    this.unsubscribeFromAdapter = null;
+
+    await this.adapter.stop();
+  }
+
+  /**
+   * Returns the latest price for a pair in NUMERATOR/DENOMINATOR form.
+   *
+   * Example: `getRate("USD", "BCH")`.
+   */
+  public getRate(
+    numeratorUnitCode: string,
+    denominatorUnitCode: string,
+  ): number | null {
+    const pair = this.getPairKey(numeratorUnitCode, denominatorUnitCode);
+    return this.ratesByPair.get(pair)?.price ?? null;
+  }
+
+  /**
+   * Converts satoshis to fiat using the latest BCH/fiat rate.
+   *
+   * Example: `convertBchToFiat(1234n, "USD")`.
+   */
+  public convertBchToFiat(
+    satoshis: bigint,
+    targetCurrency: string = 'USD',
+  ): number | null {
+    const rate = this.getRate(targetCurrency, 'BCH');
+    if (rate === null) {
+      return null;
+    }
+
+    const amountInBch = Number(satoshis) / 100_000_000;
+    return amountInBch * rate;
+  }
+
+  /**
+   * Formats a BCH -> fiat converted amount using the adapter formatter.
+   */
+  public formatBchToFiat(
+    satoshis: bigint,
+    targetCurrency: string = 'USD',
+  ): string | null {
+    const normalizedCurrency = targetCurrency.toUpperCase();
+    const amount = this.convertBchToFiat(satoshis, normalizedCurrency);
+    if (amount === null) {
+      return null;
+    }
+    return this.adapter.formatCurrency(amount, normalizedCurrency);
+  }
+
+  /**
+   * Formats an arbitrary fiat amount in a currency-aware way.
+   */
+  public formatCurrency(amount: number, currencyCode: string): string {
+    return this.adapter.formatCurrency(amount, currencyCode.toUpperCase());
+  }
+
+  /**
+   * Handles normalized updates from the underlying adapter.
+   */
+  private handleRateUpdated(event: RatesEventMap['rateUpdated']): void {
+    const numeratorUnitCode = event.numeratorUnitCode.toUpperCase();
+    const denominatorUnitCode = event.denominatorUnitCode.toUpperCase();
+    const pair = this.getPairKey(numeratorUnitCode, denominatorUnitCode);
+    const updatedAt = Date.now();
+
+    this.ratesByPair.set(pair, {
+      price: event.price,
+      updatedAt,
+    });
+
+    this.emit('rate-updated', {
+      numeratorUnitCode,
+      denominatorUnitCode,
+      price: event.price,
+      pair,
+      updatedAt,
+    });
+  }
+
+  /**
+   * Creates a stable key for pair lookups.
+   */
+  private getPairKey(
+    numeratorUnitCode: string,
+    denominatorUnitCode: string,
+  ): string {
+    return `${numeratorUnitCode.toUpperCase()}/${denominatorUnitCode.toUpperCase()}`;
+  }
+}