Filter insufficient source funds paths from pathfind results

When pathfinding with source amount, we need to filter out paths where source
amount is not equal to the specified source amount. This is due to the behavior
of rippled when specifying a source amount during pathfinding.

Example:

 {
  "command": "ripple_path_find",
  "source_account": "rhFQQ4ATC6MDF9ghTq3qAoCsGbGtjnhcXF",
  "destination_account": "rp91GUd5R3Rk3ipqW7XBdtrUJcX8epzGyb",
  "destination_amount": {
    "currency": "EUR",
    "issuer": "rp91GUd5R3Rk3ipqW7XBdtrUJcX8epzGyb",
    "value": -1
  },
  "send_max": {
    "currency": "USD",
    "issuer": "rhFQQ4ATC6MDF9ghTq3qAoCsGbGtjnhcXF",
    "value": "1234567891"
  },
  "id": 2
}
{
  "id": 2,
  "result": {
    "alternatives": [
      {
        "destination_amount": {
          "currency": "EUR",
          "issuer": "rp91GUd5R3Rk3ipqW7XBdtrUJcX8epzGyb",
          "value": "3999889.62127857"
        },
        "paths_canonical": [],
        "paths_computed": [
          [
            {
              "account": "rcsxQxEqU2qquAKp3tBUJy8Z2t19ioQPJ",
              "type": 1,
              "type_hex": "0000000000000001"
            },
            {
              "currency": "EUR",
              "issuer": "rp91GUd5R3Rk3ipqW7XBdtrUJcX8epzGyb",
              "type": 48,
              "type_hex": "0000000000000030"
            }
          ]
        ],
        "source_amount": {
          "currency": "USD",
          "issuer": "rhFQQ4ATC6MDF9ghTq3qAoCsGbGtjnhcXF",
          "value": "4170759.906037564"
        }
      }
    ],
    "destination_account": "rp91GUd5R3Rk3ipqW7XBdtrUJcX8epzGyb",
    "destination_amount": {
      "currency": "EUR",
      "issuer": "rp91GUd5R3Rk3ipqW7XBdtrUJcX8epzGyb",
      "value": "-1"
    },
    "destination_currencies": [
      "EUR",
      "XRP"
    ],
    "full_reply": true,
    "id": 2,
    "source_account": "rhFQQ4ATC6MDF9ghTq3qAoCsGbGtjnhcXF",
    "status": "success"
  },
  "status": "success",
  "type": "response"
}

src/ledger/pathfind.js

@@ -85,6 +85,20 @@ function conditionallyAddDirectXRPPath(connection: Connection, address: string,
     xrpBalance => addDirectXrpPath(paths, xrpBalance));
 }
 
+function filterSourceFundsLowPaths(pathfind: PathFind,
+                                   paths: RippledPathsResponse
+): RippledPathsResponse {
+  if (pathfind.source.amount &&
+      pathfind.destination.amount.value === undefined && paths.alternatives) {
+    paths.alternatives = _.filter(paths.alternatives, alt => {
+      return alt.source_amount &&
+        pathfind.source.amount &&
+        alt.source_amount.value === pathfind.source.amount.value;
+    });
+  }
+  return paths;
+}
+
 function formatResponse(pathfind: PathFind, paths: RippledPathsResponse) {
   if (paths.alternatives && paths.alternatives.length > 0) {
     return parsePathfind(paths);
@@ -116,7 +130,9 @@ function getPaths(pathfind: PathFind): Promise<GetPaths> {
   const address = pathfind.source.address;
   return requestPathFind(this.connection, pathfind).then(paths =>
     conditionallyAddDirectXRPPath(this.connection, address, paths)
-  ).then(paths => formatResponse(pathfind, paths));
+  )
+  .then(paths => filterSourceFundsLowPaths(pathfind, paths))
+  .then(paths => formatResponse(pathfind, paths));
 }
 
 module.exports = getPaths;

test/api-test.js

@@ -1049,6 +1049,15 @@ describe('RippleAPI', function() {
     });
   });
 
+  it('getPaths - no paths source amount', function() {
+    return this.api.getPaths(requests.getPaths.NoPathsSource).then(() => {
+      assert(false, 'Should throw NotFoundError');
+    }).catch(error => {
+      assert(error instanceof this.api.errors.NotFoundError);
+    });
+  });
+
+
   it('getPaths - no paths with source currencies', function() {
     const pathfind = requests.getPaths.NoPathsWithCurrencies;
     return this.api.getPaths(pathfind).then(() => {

test/fixtures/addresses.js

@@ -6,5 +6,6 @@ module.exports = {
   FOURTH_ACCOUNT: 'rJnZ4YHCUsHvQu7R6mZohevKJDHFzVD6Zr',
   ISSUER: 'rMH4UxPrbuMa1spCBR98hLLyNJp4d8p4tM',
   NOTFOUND: 'rajTAg3hon5Lcu1RxQQPxTgHvqfhc1EaUS',
-  SECRET: 'shsWGZcmZz6YsWWmcnpfr6fLTdtFV'
+  SECRET: 'shsWGZcmZz6YsWWmcnpfr6fLTdtFV',
+  SOURCE_LOW_FUNDS: 'rhVgDEfS1r1fLyRUZCpab4TdowZcAJwHy2'
 };

test/fixtures/requests/getpaths/no-paths-source-amount.json

@@ -0,0 +1,13 @@
+{
+  "source": {
+    "address": "rhVgDEfS1r1fLyRUZCpab4TdowZcAJwHy2",
+    "amount": {
+      "value": "1000002",
+      "currency": "USD"
+    }
+  },
+  "destination": {
+    "address": "r9cZA1mLK5R5Am25ArfXFmqgNwjZgnfk59",
+    "amount": {"currency": "USD"}
+  }
+}

test/fixtures/requests/index.js

@@ -53,6 +53,7 @@ module.exports = {
     XrpToXrpNotEnough: require('./getpaths/xrp2xrp-not-enough'),
     NotAcceptCurrency: require('./getpaths/not-accept-currency'),
     NoPaths: require('./getpaths/no-paths'),
+    NoPathsSource: require('./getpaths/no-paths-source-amount'),
     NoPathsWithCurrencies: require('./getpaths/no-paths-with-currencies'),
     sendAll: require('./getpaths/send-all'),
     invalid: require('./getpaths/invalid'),

test/fixtures/rippled/index.js

@@ -38,7 +38,8 @@ module.exports = {
     sendUSD: require('./path-find-send-usd'),
     sendAll: require('./path-find-send-all'),
     XrpToXrp: require('./path-find-xrp-to-xrp'),
-    srcActNotFound: require('./path-find-srcActNotFound')
+    srcActNotFound: require('./path-find-srcActNotFound'),
+    sourceAmountLow: require('./path-find-srcAmtLow')
   },
   tx: {
     Payment: require('./tx/payment.json'),

test/fixtures/rippled/path-find-srcAmtLow.json

@@ -0,0 +1,97 @@
+{
+  "id": 0,
+  "result": {
+    "full_reply": true,
+    "alternatives": [
+      {
+        "paths_canonical": [],
+        "paths_computed": [
+          [
+            {
+              "account": "rvYAfWj5gh67oV6fW32ZzP3Aw4Eubs59B",
+              "type": 1,
+              "type_hex": "0000000000000001"
+            }
+          ],
+          [
+            {
+              "account": "rvYAfWj5gh67oV6fW32ZzP3Aw4Eubs59B",
+              "type": 1,
+              "type_hex": "0000000000000001"
+            },
+            {
+              "account": "rLMJ4db4uwHcd6NHg6jvTaYb8sH5Gy4tg5",
+              "type": 1,
+              "type_hex": "0000000000000001"
+            },
+            {
+              "account": "rLEsXccBGNR3UPuPu2hUXPjziKC3qKSBun",
+              "type": 1,
+              "type_hex": "0000000000000001"
+            }
+          ],
+          [
+            {
+              "account": "rvYAfWj5gh67oV6fW32ZzP3Aw4Eubs59B",
+              "type": 1,
+              "type_hex": "0000000000000001"
+            },
+            {
+              "currency": "USD",
+              "issuer": "rLEsXccBGNR3UPuPu2hUXPjziKC3qKSBun",
+              "type": 48,
+              "type_hex": "0000000000000030"
+            },
+            {
+              "account": "rLEsXccBGNR3UPuPu2hUXPjziKC3qKSBun",
+              "type": 1,
+              "type_hex": "0000000000000001"
+            }
+          ],
+          [
+            {
+              "account": "rvYAfWj5gh67oV6fW32ZzP3Aw4Eubs59B",
+              "type": 1,
+              "type_hex": "0000000000000001"
+            },
+            {
+              "account": "rLMJ4db4uwHcd6NHg6jvTaYb8sH5Gy4tg5",
+              "type": 1,
+              "type_hex": "0000000000000001"
+            },
+            {
+              "account": "r9vbV3EHvXWjSkeQ6CAcYVPGeq7TuiXY2X",
+              "type": 1,
+              "type_hex": "0000000000000001"
+            }
+          ]
+        ],
+        "source_amount": {
+          "currency": "USD",
+          "issuer": "rpZc4mVfWUif9CRoHRKKcmhu1nx2xktxBo",
+          "value": "0.000001002"
+        }
+      }
+    ],
+    "source_account": "rhVgDEfS1r1fLyRUZCpab4TdowZcAJwHy2",
+    "destination_amount": {
+      "currency": "USD",
+      "value": "-1",
+      "issuer": "r9cZA1mLK5R5Am25ArfXFmqgNwjZgnfk59"
+    },
+    "destination_account": "r9cZA1mLK5R5Am25ArfXFmqgNwjZgnfk59",
+    "destination_currencies": [
+      "JOE",
+      "BTC",
+      "DYM",
+      "CNY",
+      "EUR",
+      "015841551A748AD2C1F76FF6ECB0CCCD00000000",
+      "MXN",
+      "USD",
+      "XRP"
+    ]
+  },
+  "status": "success",
+  "type": "response"
+}

test/mock-rippled.js

@@ -323,6 +323,8 @@ module.exports = function(port) {
     }
     if (request.source_account === addresses.NOTFOUND) {
       response = createResponse(request, fixtures.path_find.srcActNotFound);
+    } else if (request.source_account === addresses.SOURCE_LOW_FUNDS) {
+      response = createResponse(request, fixtures.path_find.sourceAmountLow);
     } else if (request.source_account === addresses.OTHER_ACCOUNT) {
       response = createResponse(request, fixtures.path_find.sendUSD);
     } else if (request.source_account === addresses.THIRD_ACCOUNT) {