feat(findBiggestUtxo): Ported from bch-util. Finds biggest UTXO in an array

src/utxo.js

@@ -279,6 +279,38 @@ class UTXO {
       throw err
     }
   }
+
+  // Returns the utxo with the biggest balance from an array of utxos.
+  findBiggestUtxo (utxos) {
+    let largestAmount = 0
+    let largestIndex = 0
+
+    if (!Array.isArray(utxos)) {
+      throw new Error('utxos input to findBiggestUtxo() must be an array')
+    }
+
+    for (var i = 0; i < utxos.length; i++) {
+      const thisUtxo = utxos[i]
+
+      // Give Elecrumx utxos a satoshis property.
+      if (thisUtxo.value) {
+        if (!thisUtxo.satoshis) thisUtxo.satoshis = Number(thisUtxo.value)
+      }
+
+      if (!thisUtxo.satoshis) {
+        throw new Error(
+          'UTXOs require a satoshis or value property for findBiggestUtxo()'
+        )
+      }
+
+      if (thisUtxo.satoshis > largestAmount) {
+        largestAmount = thisUtxo.satoshis
+        largestIndex = i
+      }
+    }
+
+    return utxos[largestIndex]
+  }
 }
 
 module.exports = UTXO

test/integration/chains/bchn/utxo-integration.js

@@ -90,6 +90,34 @@ describe('#UTXO', () => {
       assert.isAbove(result[0].nullUtxos.length, 1)
     })
   })
+
+  describe('#findBiggestUtxo', () => {
+    it('should sort UTXOs from Electrumx', async () => {
+      const addr = 'bitcoincash:qq54fgjn3hz0357n8a6guy4demw9xfkjk5jcj0xr0z'
+
+      const electrumxUtxos = await bchjs.Electrumx.utxo(addr)
+      // console.log(`Electrumx utxos: ${JSON.stringify(electrumxUtxos, null, 2)}`)
+
+      const result = bchjs.Utxo.findBiggestUtxo(electrumxUtxos.utxos)
+      // console.log(`result: ${JSON.stringify(result, null, 2)}`)
+
+      assert.property(result, 'satoshis')
+      assert.equal(result.satoshis, 800)
+    })
+
+    it('should sort UTXOs from Utxos.get()', async () => {
+      const addr = 'bitcoincash:qq54fgjn3hz0357n8a6guy4demw9xfkjk5jcj0xr0z'
+
+      const utxos = await bchjs.Utxo.get(addr)
+      // console.log(`utxos: ${JSON.stringify(utxos, null, 2)}`)
+
+      const result = bchjs.Utxo.findBiggestUtxo(utxos[0].bchUtxos)
+      // console.log(`result: ${JSON.stringify(result, null, 2)}`)
+
+      assert.property(result, 'satoshis')
+      assert.equal(result.satoshis, 800)
+    })
+  })
 })
 
 function sleep (ms) {

test/unit/fixtures/utxo-mocks.js

@@ -253,9 +253,37 @@ const mockEveryUtxoType = {
   ]
 }
 
+const electrumxUtxos = {
+  success: true,
+  utxos: [
+    {
+      height: 0,
+      tx_hash:
+        '192f5037bb3822afd92d6b6ab51842a5dcfbe6bff783290057342da1f27ed414',
+      tx_pos: 0,
+      value: 600
+    },
+    {
+      height: 0,
+      tx_hash:
+        'f913646f7c180f8de020cb1387951272e8a3f764a0f88e68f7fc1145a0bf02e9',
+      tx_pos: 0,
+      value: 700
+    },
+    {
+      height: 0,
+      tx_hash:
+        '7a091716f8137e94f87e7760648cd34a17e32754ef95f7c7bda38a635c9b2b1b',
+      tx_pos: 0,
+      value: 800
+    }
+  ]
+}
+
 module.exports = {
   mockUtxoData,
   mockHydratedUtxos,
   mockTwoHydratedAddrs,
-  mockEveryUtxoType
+  mockEveryUtxoType,
+  electrumxUtxos
 }

test/unit/utxo-unit.js

@@ -145,4 +145,47 @@ describe('#utxo', () => {
       assert.isArray(result[0].nullUtxos)
     })
   })
+
+  describe('#findBiggestUtxo', () => {
+    it('should throw error for non-array input', async () => {
+      try {
+        await bchjs.Utxo.findBiggestUtxo({})
+
+        assert.equal(true, false, 'Unexpected result!')
+      } catch (err) {
+        assert.include(
+          err.message,
+          'utxos input to findBiggestUtxo() must be an array'
+        )
+      }
+    })
+
+    it('should throw an error if input does not have a value or satoshis property', async () => {
+      try {
+        const badUtxos = [
+          {
+            height: 0,
+            tx_hash:
+              '192f5037bb3822afd92d6b6ab51842a5dcfbe6bff783290057342da1f27ed414',
+            tx_pos: 0
+          }
+        ]
+
+        await bchjs.Utxo.findBiggestUtxo(badUtxos)
+      } catch (err) {
+        assert.include(
+          err.message,
+          'UTXOs require a satoshis or value property for findBiggestUtxo()'
+        )
+      }
+    })
+
+    it('should sort UTXOs from Electrumx', async () => {
+      const result = bchjs.Utxo.findBiggestUtxo(mockData.electrumxUtxos.utxos)
+      // console.log(`result: ${JSON.stringify(result, null, 2)}`)
+
+      assert.property(result, 'satoshis')
+      assert.equal(result.satoshis, 800)
+    })
+  })
 })