first commit of refactor

backend/protocols/ethereum/EthereumObserver.js

@@ -0,0 +1,61 @@
+
+/**
+ * @typedef {import('../../domain/NormalizedTx.js').NormalizedTx} NormalizedTx
+ */
+
+/**
+ * @typedef {Object} EthereumObserver
+ * @property {() => Promise<number>} getLatestBlockNumber - Get the most recent block number on the chain
+ * @property {(blockNumber: number) => Promise<NormalizedTx[]>} getBlockTransactions - Get all transactions in a specific block
+ * @property {(address: string) => Promise<string>} getBalance - Get the current balance of an address (in Wei as string)
+ */
+
+/**
+ * Validates that an object implements the EthereumObserver interface
+ * @param {any} obj - Object to validate
+ * @returns {boolean} True if object implements the interface
+ */
+export function isEthereumObserver(obj) {
+  if (!obj || typeof obj !== 'object') {
+    return false;
+  }
+
+  return (
+    typeof obj.getLatestBlockNumber === 'function' &&
+    typeof obj.getBlockTransactions === 'function' &&
+    typeof obj.getBalance === 'function'
+  );
+}
+
+/**
+ * Asserts that an object implements the EthereumObserver interface
+ * Throws an error if validation fails
+ * @param {any} obj - Object to validate
+ * @param {string} [name='object'] - Name for error messages
+ * @throws {Error} If object doesn't implement the interface
+ */
+export function assertEthereumObserver(obj, name = 'object') {
+  if (!isEthereumObserver(obj)) {
+    throw new Error(
+      `${name} must implement EthereumObserver interface ` +
+      `(getLatestBlockNumber, getBlockTransactions, getBalance)`
+    );
+  }
+}
+
+/**
+ * Example usage 
+ * 
+ * import { assertEthereumObserver } from './protocols/ethereum/EthereumObserver.js';
+ * 
+ * export function createObserverService(ethereumObserver) {
+ *   assertEthereumObserver(ethereumObserver, 'ethereumObserver');
+ *   // ... use ethereumObserver safely
+ * }
+ */
+
+export default {
+  isEthereumObserver,
+  assertEthereumObserver,
+};
+