[TX] implement sorting & add helper func

Author: Ivan Bozhytskyi

types/v1/marshal.go

@@ -79,3 +79,8 @@ func (t *Tx) MarshalJSON() ([]byte, error) {
 	// Wrap the Tx type to avoid infinite recursion
 	return json.Marshal(wrappedTx(*t))
 }
+
+// Sort sorts the response by date, descending
+func (txs Txs) Len() int           { return len(txs) }
+func (txs Txs) Less(i, j int) bool { return txs[i].Date > txs[j].Date }
+func (txs Txs) Swap(i, j int)      { txs[i], txs[j] = txs[j], txs[i] }

types/v1/tx.go

@@ -406,3 +406,15 @@ func InferDirection(transfer *Transfer, addressSet mapset.Set) Direction {
 	}
 	return DirectionOutgoing
 }
+
+func IsTxTypeAmong(txType TransactionType, types []TransactionType) bool {
+	result := false
+	for _, t := range types {
+		if txType == t {
+			result = true
+			break
+		}
+	}
+
+	return result
+}