feat: add amount and fiat amount types

src/index.ts

@@ -6,5 +6,6 @@ export * as l402 from "./l402";
 export * as boostagrams from "./podcasting2/boostagrams";
 export * as fiat from "./utils/fiat";
 export * as nostr from "./utils/nostr";
+export * from "./utils/Amount";
 export { fetchWithL402, sendBoostagram, LightningAddress, Invoice };
 export * from "./types";

src/utils/Amount.test.ts

@@ -0,0 +1,20 @@
+import { resolveAmount, SATS } from "./Amount";
+
+describe("Amount", () => {
+  test("SATS", async () => {
+    const amount = SATS(10);
+    expect(amount.satoshi).toBe(10);
+  });
+  test("resolveAmount", async () => {
+    const resolved = await resolveAmount({ satoshi: 10 });
+    expect(resolved.satoshi).toBe(10);
+    expect(resolved.millisat).toBe(10_000);
+  });
+  test("resolveAmount async", async () => {
+    const resolved = await resolveAmount({
+      satoshi: new Promise((resolve) => setTimeout(() => resolve(10), 300)),
+    });
+    expect(resolved.satoshi).toBe(10);
+    expect(resolved.millisat).toBe(10_000);
+  });
+});

src/utils/Amount.ts

@@ -0,0 +1,22 @@
+/**
+ * An amount in satoshis
+ */
+export type Amount = { satoshi: number } | { satoshi: Promise<number> };
+
+export const SATS: (amount: number) => Amount = (amount) => ({
+  satoshi: amount,
+});
+
+/**
+ * Resolve a satoshi amount, possibly from a promise (e.g. from fiat conversion)
+ */
+export async function resolveAmount(
+  amount: Amount,
+): Promise<{ satoshi: number; millisat: number }> {
+  const satoshi = await Promise.resolve(amount.satoshi);
+
+  return {
+    satoshi: satoshi,
+    millisat: satoshi * 1000,
+  };
+}

src/utils/fiat/FiatAmount.test.ts

@@ -0,0 +1,29 @@
+import { resolveAmount } from "../Amount";
+import { USD } from "./FiatAmount";
+import fetchMock from "jest-fetch-mock";
+
+describe("FiatAmount", () => {
+  test("interoperable with Amount", async () => {
+    fetchMock.mockIf(/.*/, (_) => {
+      return Promise.resolve(
+        JSON.stringify({
+          code: "USD",
+          symbol: "$",
+          rate: "77135.00",
+          rate_float: 77135.0,
+          rate_cents: 7713500,
+          USD: {
+            code: "USD",
+            symbol: "$",
+            rate: "77135.00",
+            rate_float: 77135.0,
+            rate_cents: 7713500,
+          },
+        }),
+      );
+    });
+    const fiatAmount = USD(1);
+    const resolved = await resolveAmount(fiatAmount);
+    expect(resolved.satoshi).toBeGreaterThan(0);
+  });
+});

src/utils/fiat/FiatAmount.ts

@@ -0,0 +1,21 @@
+import { fiat } from "../..";
+
+/**
+ * An amount in a fiat currency represented in satoshis
+ */
+export class FiatAmount {
+  satoshi: Promise<number>;
+  constructor(amount: number, currency: string) {
+    this.satoshi = fiat.getSatoshiValue({
+      amount,
+      currency,
+    });
+  }
+}
+
+// Most popular fiat currencies
+export const USD = (amount: number) => new FiatAmount(amount, "USD");
+export const EUR = (amount: number) => new FiatAmount(amount, "EUR");
+export const JPY = (amount: number) => new FiatAmount(amount, "JPY");
+export const GBP = (amount: number) => new FiatAmount(amount, "GBP");
+export const CHF = (amount: number) => new FiatAmount(amount, "CHF");

src/utils/fiat/index.ts

@@ -0,0 +1,2 @@
+export * from "./fiat";
+export * from "./FiatAmount";