Added Utility method for topological sort

package.json

@@ -75,6 +75,7 @@
     "json-stable-stringify": "^1.0.1",
     "query-string": "^5.0.0",
     "sprintf-js": "^1.0.3",
+    "toposort": "^1.0.6",
     "tweetnacl": "^1.0.0"
   },
   "keywords": [

src/transaction/utils/topologySorting.js

@@ -0,0 +1,27 @@
+import toposort from 'toposort'
+
+function generateGraph(txs) {
+    const graph = []
+    txs.forEach(tx => {
+        tx.inputs.forEach(input => {
+            if (input.fulfills) {
+                graph.push([tx.id, input.fulfills.transaction_id])
+            }
+        })
+    })
+
+    return graph
+}
+
+
+/**
+ * @public
+ * Topological sort algorithm for transactions
+ * Used for endpoint: /transactions?assetId
+ * @param {object} txs Array of transactions
+ * @returns {object} Returns transactions in order of dependency
+ */
+export default function topsortTransactions(txs) {
+    const graph = generateGraph(txs)
+    return toposort(graph).reverse()
+}