refactor(sdk-core,bitgo): replace per-currency fiat classes with config-driven Fiat class

Replace 36 individual fiat coin class files with a single generic Fiat class
that takes a config object (chain, fullName, baseFactor). All currencies are
defined in a config array and registration is automatic via a loop in
coinFactory. Testnet variants are derived automatically from mainnet configs.

This reduces the effort to add a new fiat currency from ~6 files and 150+
lines of boilerplate to a single config line.

FIAT-311

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: drew-bitgo

modules/bitgo/src/v2/coinFactory.ts

@@ -91,12 +91,8 @@ import {
   HashToken,
   MonToken,
   TethLikeCoin,
-  FiatAED,
-  FiatEur,
-  FiatGBP,
-  FiatINR,
-  FiatSGD,
-  FiatUsd,
+  Fiat,
+  allFiatCoins,
   Gteth,
   Hash,
   Hbar,
@@ -171,12 +167,6 @@ import {
   Teth,
   Tflr,
   Tmon,
-  TfiatAED,
-  TfiatEur,
-  TfiatGBP,
-  TfiatINR,
-  TfiatSGD,
-  TfiatUsd,
   Thash,
   Thbar,
   Tia,
@@ -274,12 +264,9 @@ export function registerCoinConstructors(coinFactory: CoinFactory, coinMap: Coin
   coinFactory.register('topbnb', TethLikeCoin.createInstance);
   coinFactory.register('tfantom', TethLikeCoin.createInstance);
   coinFactory.register('tbaseeth', TethLikeCoin.createInstance);
-  coinFactory.register('fiataed', FiatAED.createInstance);
-  coinFactory.register('fiateur', FiatEur.createInstance);
-  coinFactory.register('fiatgbp', FiatGBP.createInstance);
-  coinFactory.register('fiatinr', FiatINR.createInstance);
-  coinFactory.register('fiatsgd', FiatSGD.createInstance);
-  coinFactory.register('fiatusd', FiatUsd.createInstance);
+  for (const fiatCoin of allFiatCoins) {
+    coinFactory.register(fiatCoin.chain, Fiat.createConstructor(fiatCoin));
+  }
   coinFactory.register('flr', Flr.createInstance);
   coinFactory.register('flrp', Flrp.createInstance);
   coinFactory.register('gteth', Gteth.createInstance);
@@ -346,12 +333,6 @@ export function registerCoinConstructors(coinFactory: CoinFactory, coinMap: Coin
   coinFactory.register('teos', Teos.createInstance);
   coinFactory.register('tetc', Tetc.createInstance);
   coinFactory.register('teth', Teth.createInstance);
-  coinFactory.register('tfiataed', TfiatAED.createInstance);
-  coinFactory.register('tfiateur', TfiatEur.createInstance);
-  coinFactory.register('tfiatgbp', TfiatGBP.createInstance);
-  coinFactory.register('tfiatinr', TfiatINR.createInstance);
-  coinFactory.register('tfiatsgd', TfiatSGD.createInstance);
-  coinFactory.register('tfiatusd', TfiatUsd.createInstance);
   coinFactory.register('tflr', Tflr.createInstance);
   coinFactory.register('tflrp', Flrp.createInstance);
   coinFactory.register('tmon', Tmon.createInstance);
@@ -693,18 +674,6 @@ export function getCoinConstructor(coinName: string): CoinConstructor | undefine
       return TethLikeCoin.createInstance;
     case 'tfantom':
       return TethLikeCoin.createInstance;
-    case 'fiataed':
-      return FiatAED.createInstance;
-    case 'fiateur':
-      return FiatEur.createInstance;
-    case 'fiatgbp':
-      return FiatGBP.createInstance;
-    case 'fiatinr':
-      return FiatINR.createInstance;
-    case 'fiatsgd':
-      return FiatSGD.createInstance;
-    case 'fiatusd':
-      return FiatUsd.createInstance;
     case 'flr':
       return Flr.createInstance;
     case 'flrp':
@@ -837,18 +806,6 @@ export function getCoinConstructor(coinName: string): CoinConstructor | undefine
       return Tetc.createInstance;
     case 'teth':
       return Teth.createInstance;
-    case 'tfiataed':
-      return TfiatAED.createInstance;
-    case 'tfiateur':
-      return TfiatEur.createInstance;
-    case 'tfiatgbp':
-      return TfiatGBP.createInstance;
-    case 'tfiatinr':
-      return TfiatINR.createInstance;
-    case 'tfiatsgd':
-      return TfiatSGD.createInstance;
-    case 'tfiatusd':
-      return TfiatUsd.createInstance;
     case 'tflr':
       return Tflr.createInstance;
     case 'tflrp':
@@ -957,8 +914,13 @@ export function getCoinConstructor(coinName: string): CoinConstructor | undefine
       return Zeta.createInstance;
     case 'zketh':
       return Zketh.createInstance;
-    default:
+    default: {
+      const fiatConfig = allFiatCoins.find((c) => c.chain === coinName);
+      if (fiatConfig) {
+        return Fiat.createConstructor(fiatConfig);
+      }
       return undefined;
+    }
   }
 }
 

modules/bitgo/src/v2/coins/index.ts

@@ -155,39 +155,5 @@ export { World, Tworld, WorldToken };
 export { Zketh, Tzketh, ZkethToken };
 
 import { coins } from '@bitgo/sdk-core';
-const {
-  Ofc,
-  OfcToken,
-  Susd,
-  FiatUsd,
-  FiatEur,
-  FiatGBP,
-  FiatINR,
-  FiatAED,
-  FiatSGD,
-  Tsusd,
-  TfiatUsd,
-  TfiatEur,
-  TfiatGBP,
-  TfiatINR,
-  TfiatAED,
-  TfiatSGD,
-} = coins;
-export {
-  FiatAED,
-  FiatEur,
-  FiatGBP,
-  FiatINR,
-  FiatSGD,
-  FiatUsd,
-  Ofc,
-  OfcToken,
-  Susd,
-  TfiatAED,
-  TfiatEur,
-  TfiatGBP,
-  TfiatINR,
-  TfiatSGD,
-  TfiatUsd,
-  Tsusd,
-};
+const { Ofc, OfcToken, Susd, Tsusd, Fiat, allFiatCoins, fiatCoins, testnetFiatCoins } = coins;
+export { Fiat, allFiatCoins, fiatCoins, testnetFiatCoins, Ofc, OfcToken, Susd, Tsusd };

modules/sdk-core/src/coins/fiat.ts

@@ -0,0 +1,116 @@
+/**
+ * @prettier
+ */
+import {
+  AuditDecryptedKeyParams,
+  BaseCoin,
+  BitGoBase,
+  CoinConstructor,
+  KeyPair,
+  MethodNotImplementedError,
+  ParsedTransaction,
+  ParseTransactionOptions,
+  SignedTransaction,
+  SignTransactionOptions,
+  VerifyAddressOptions,
+  VerifyTransactionOptions,
+} from '../';
+
+export interface FiatCoinConfig {
+  chain: string;
+  fullName: string;
+  baseFactor: number;
+}
+
+export class Fiat extends BaseCoin {
+  private readonly config: FiatCoinConfig;
+
+  constructor(bitgo: BitGoBase, config: FiatCoinConfig) {
+    super(bitgo);
+    this.config = config;
+  }
+
+  static createConstructor(config: FiatCoinConfig): CoinConstructor {
+    return (bitgo: BitGoBase) => new Fiat(bitgo, config);
+  }
+
+  getBaseFactor() {
+    return this.config.baseFactor;
+  }
+
+  getChain() {
+    return this.config.chain;
+  }
+
+  getFamily() {
+    return 'fiat';
+  }
+
+  getFullName() {
+    return this.config.fullName;
+  }
+
+  isValidMofNSetup({ m, n }: { m: number; n: number }) {
+    return m === 0 && n === 0;
+  }
+
+  isValidAddress(address: string): boolean {
+    throw new MethodNotImplementedError();
+  }
+
+  generateKeyPair(seed?: Buffer): KeyPair {
+    throw new MethodNotImplementedError();
+  }
+
+  isValidPub(pub: string): boolean {
+    throw new MethodNotImplementedError();
+  }
+
+  async parseTransaction(params: ParseTransactionOptions): Promise<ParsedTransaction> {
+    return {};
+  }
+
+  async isWalletAddress(params: VerifyAddressOptions): Promise<boolean> {
+    throw new MethodNotImplementedError();
+  }
+
+  async verifyTransaction(params: VerifyTransactionOptions): Promise<boolean> {
+    return true;
+  }
+
+  async signTransaction(params: SignTransactionOptions = {}): Promise<SignedTransaction> {
+    throw new MethodNotImplementedError();
+  }
+
+  /** @inheritDoc */
+  auditDecryptedKey(params: AuditDecryptedKeyParams): void {
+    throw new MethodNotImplementedError();
+  }
+}
+
+/**
+ * Configuration for all fiat currencies.
+ * To add a new fiat currency, just add an entry here — registration is automatic.
+ */
+export const fiatCoins: FiatCoinConfig[] = [
+  { chain: 'fiataed', fullName: 'United Arab Emirates Dirham', baseFactor: 1e2 },
+  { chain: 'fiateur', fullName: 'European Union Euro', baseFactor: 1e2 },
+  { chain: 'fiatgbp', fullName: 'British Pound Sterling', baseFactor: 1e2 },
+  { chain: 'fiatinr', fullName: 'Indian Rupee', baseFactor: 1e2 },
+  { chain: 'fiatsgd', fullName: 'Singapore Dollar', baseFactor: 1e2 },
+  { chain: 'fiatusd', fullName: 'USD Dollar', baseFactor: 1e2 },
+];
+
+/**
+ * Testnet configs derived automatically from mainnet configs.
+ */
+export const testnetFiatCoins: FiatCoinConfig[] = fiatCoins.map((c) => ({
+  chain: `t${c.chain}`,
+  fullName: `Testnet ${c.fullName}`,
+  baseFactor: c.baseFactor,
+}));
+
+/**
+ * All fiat coin configs (mainnet + testnet).
+ */
+export const allFiatCoins: FiatCoinConfig[] = [...fiatCoins, ...testnetFiatCoins];