FIX: legacy wallet can now derive UTXO from transactions in case if fetching listUnspent from network is impossible (closes #2528)

class/wallets/legacy-wallet.js

@@ -1,6 +1,7 @@
 import { randomBytes } from '../rng';
 import { AbstractWallet } from './abstract-wallet';
 import { HDSegwitBech32Wallet } from '..';
+import BigNumber from 'bignumber.js';
 const bitcoin = require('bitcoinjs-lib');
 const BlueElectrum = require('../../blue_modules/BlueElectrum');
 const coinSelectAccumulative = require('coinselect/accumulative');
@@ -161,12 +162,72 @@ export class LegacyWallet extends AbstractWallet {
       if (!u.confirmations && u.height) u.confirmations = BlueElectrum.estimateCurrentBlockheight() - u.height;
       ret.push(u);
     }
+
+    if (ret.length === 0) {
+      ret = this.getDerivedUtxoFromOurTransaction(); // oy vey, no stored utxo. lets attempt to derive it from stored transactions
+    }
+
     if (!respectFrozen) {
       ret = ret.filter(({ txid, vout }) => !this.getUTXOMetadata(txid, vout).frozen);
     }
     return ret;
   }
 
+  getDerivedUtxoFromOurTransaction(returnSpentUtxoAsWell = false) {
+    const utxos = [];
+
+    const ownedAddressesHashmap = {};
+    ownedAddressesHashmap[this.getAddress()] = true;
+
+    /**
+     * below copypasted from
+     * @see AbstractHDElectrumWallet.getDerivedUtxoFromOurTransaction
+     */
+
+    for (const tx of this.getTransactions()) {
+      for (const output of tx.outputs) {
+        let address = false;
+        if (output.scriptPubKey && output.scriptPubKey.addresses && output.scriptPubKey.addresses[0]) {
+          address = output.scriptPubKey.addresses[0];
+        }
+        if (ownedAddressesHashmap[address]) {
+          const value = new BigNumber(output.value).multipliedBy(100000000).toNumber();
+          utxos.push({
+            txid: tx.txid,
+            txId: tx.txid,
+            vout: output.n,
+            address,
+            value,
+            amount: value,
+            confirmations: tx.confirmations,
+            wif: false,
+            height: BlueElectrum.estimateCurrentBlockheight() - tx.confirmations,
+          });
+        }
+      }
+    }
+
+    if (returnSpentUtxoAsWell) return utxos;
+
+    // got all utxos we ever had. lets filter out the ones that are spent:
+    const ret = [];
+    for (const utxo of utxos) {
+      let spent = false;
+      for (const tx of this.getTransactions()) {
+        for (const input of tx.inputs) {
+          if (input.txid === utxo.txid && input.vout === utxo.vout) spent = true;
+          // utxo we got previously was actually spent right here ^^
+        }
+      }
+
+      if (!spent) {
+        ret.push(utxo);
+      }
+    }
+
+    return ret;
+  }
+
   /**
    * Fetches transactions via Electrum. Returns VOID.
    * Use getter to get the actual list.   *

tests/integration/legacy-wallet.test.js

@@ -54,11 +54,11 @@ describe('LegacyWallet', function () {
     assert.ok(w._lastBalanceFetch > 0);
   });
 
-  it('can fetch TXs', async () => {
+  it('can fetch TXs and derive UTXO from them', async () => {
     const w = new LegacyWallet();
-    w._address = '12eQ9m4sgAwTSQoNXkRABKhCXCsjm2jdVG';
+    w._address = '3GCvDBAktgQQtsbN6x5DYiQCMmgZ9Yk8BK';
     await w.fetchTransactions();
-    assert.strictEqual(w.getTransactions().length, 2);
+    assert.strictEqual(w.getTransactions().length, 1);
 
     for (const tx of w.getTransactions()) {
       assert.ok(tx.hash);
@@ -67,9 +67,19 @@ describe('LegacyWallet', function () {
       assert.ok(tx.confirmations > 1);
     }
 
-    assert.ok(w.weOwnTransaction('4924f3a29acdee007ebcf6084d2c9e1752c4eb7f26f7d1a06ef808780bf5fe6d'));
-    assert.ok(w.weOwnTransaction('d0432027a86119c63a0be8fa453275c2333b59067f1e559389cd3e0e377c8b96'));
+    assert.ok(w.weOwnTransaction('b2ac59bc282083498d1e87805d89bef9d3f3bc216c1d2c4dfaa2e2911b547100'));
     assert.ok(!w.weOwnTransaction('825c12f277d1f84911ac15ad1f41a3de28e9d906868a930b0a7bca61b17c8881'));
+
+    assert.strictEqual(w.getUtxo().length, 1);
+
+    for (const tx of w.getUtxo()) {
+      assert.strictEqual(tx.txid, 'b2ac59bc282083498d1e87805d89bef9d3f3bc216c1d2c4dfaa2e2911b547100');
+      assert.strictEqual(tx.vout, 0);
+      assert.strictEqual(tx.address, '3GCvDBAktgQQtsbN6x5DYiQCMmgZ9Yk8BK');
+      assert.strictEqual(tx.value, 51432);
+      assert.strictEqual(tx.value, tx.amount);
+      assert.ok(tx.confirmations > 0);
+    }
   });
 
   it.each([