initial commit

src/core/balances.js

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+/**
+ * balances.js
+ *
+ * Reads on-chain balances. Requires the user to configure RPC endpoints
+ * (config.json) — we don't bake in a paid provider's API key. Free public
+ * endpoints are set as defaults so it works out of the box, but they are
+ * rate-limited and not meant for production use.
+ */
+
+const { ethers } = require('ethers');
+const { Connection, PublicKey, LAMPORTS_PER_SOL } = require('@solana/web3.js');
+
+async function getEthBalance(address, rpcUrl) {
+  const provider = new ethers.JsonRpcProvider(rpcUrl);
+  const wei = await provider.getBalance(address);
+  return ethers.formatEther(wei); // returns a decimal string, e.g. "1.234"
+}
+
+async function getSolBalance(address, rpcUrl) {
+  const connection = new Connection(rpcUrl);
+  const lamports = await connection.getBalance(new PublicKey(address));
+  return (lamports / LAMPORTS_PER_SOL).toString();
+}
+
+/** Bitcoin: no JSON-RPC by default without running your own node, so we
+ * use a block explorer's public REST API (Blockstream) instead. */
+async function getBtcBalance(address, apiBase = 'https://blockstream.info/api') {
+  const res = await fetch(`${apiBase}/address/${address}`);
+  if (!res.ok) throw new Error(`Blockstream API error: ${res.status}`);
+  const data = await res.json();
+  const sats =
+    data.chain_stats.funded_txo_sum -
+    data.chain_stats.spent_txo_sum +
+    data.mempool_stats.funded_txo_sum -
+    data.mempool_stats.spent_txo_sum;
+  return (sats / 1e8).toString();
+}
+
+module.exports = { getEthBalance, getSolBalance, getBtcBalance };