From c164729eec70d4d680b2d814c71160da2f6f41cf Mon Sep 17 00:00:00 2001
From: joepetrowski <joe@parity.io>
Date: Sat, 30 May 2020 13:35:15 +0200
Subject: [PATCH] add fee prediction endpoint

---
 src/util/util.ts | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/util/util.ts b/src/util/util.ts
index 0a079f8..8f1f1fb 100644
--- a/src/util/util.ts
+++ b/src/util/util.ts
@@ -168,12 +168,21 @@ export async function getClaimType(sidecarHost: string, address: string): Promis
   return claimsType.type;
 }
 
+// Submit a transaction over Sidecar to the transaction queue.
 export async function submitTransaction(sidecarHost: string, encodedTx: string): Promise<any> {
   const endpoint = `${sidecarHost}tx/`;
   const submission = await sidecarPost(endpoint, encodedTx);
   return submission;
 }
 
+// Submit a transaction and ask for a transaction fee estimate. Do not submit the transaction to the
+// transaction queue.
+export async function getFeeEstimate(sidecarHost: string, encodedTx: string): Promise<any> {
+  const endpoint = `${sidecarHost}tx/fee-estimate/`;
+  const dispatchInfo = await sidecarPost(endpoint, encodedTx);
+  return dispatchInfo;
+}
+
 /* Signing utilities */
 
 // Ask the user to supply a signature and wait for the response.
@@ -235,11 +244,20 @@ async function sidecarPost(url: string, tx: string): Promise<any> {
       },
     )
     .then(({ data }) => data)
-    .then(({ cause, data, error, hash }) => {
+    .then(({ cause, data, error, hash, weight, partialFee }) => {
       if (cause || error) {
         throw new Error(`${cause}: ${error} (${data})`);
       }
 
-      return hash;
+      if (hash) {
+        return hash;
+      }
+
+      if (partialFee) {
+        return {
+          weight,
+          partialFee
+        };
+      }
     });
 }