From 50ac6f7a3e612081533b1b9caebeb81daec34d2d Mon Sep 17 00:00:00 2001
From: Willian Mitsuda <wmitsuda@gmail.com>
Date: Tue, 9 Aug 2022 01:50:38 -0300
Subject: [PATCH] Extract swr fetcher

---
 src/use4Bytes.ts | 59 +++++++++++++++++++++++-------------------------
 1 file changed, 28 insertions(+), 31 deletions(-)

diff --git a/src/use4Bytes.ts b/src/use4Bytes.ts
index 85f4e98..ddf8e2b 100644
--- a/src/use4Bytes.ts
+++ b/src/use4Bytes.ts
@@ -5,6 +5,7 @@ import {
   TransactionDescription,
 } from "@ethersproject/abi";
 import { BigNumberish } from "@ethersproject/bignumber";
+import { Fetcher } from "swr";
 import useSWRImmutable from "swr/immutable";
 import { RuntimeContext } from "./useRuntime";
 import { fourBytesURL } from "./url";
@@ -29,16 +30,32 @@ export const extract4Bytes = (rawInput: string): string | null => {
   return rawInput.slice(0, 10);
 };
 
-const fetch4Bytes = async (
-  assetsURLPrefix: string,
-  fourBytes: string
-): Promise<FourBytesEntry | null> => {
-  const signatureURL = fourBytesURL(assetsURLPrefix, fourBytes);
+type FourBytesKey = [id: "4bytes", fourBytes: string];
+type FourBytesFetcher = Fetcher<
+  FourBytesEntry | null | undefined,
+  FourBytesKey
+>;
+
+const fourBytesFetcher =
+  (assetsURLPrefix: string): FourBytesFetcher =>
+  async (_, key) => {
+    if (key === null || key === "0x") {
+      return undefined;
+    }
+
+    // Handle simple transfers with invalid selector like tx:
+    // 0x8bcbdcc1589b5c34c1e55909c8269a411f0267a4fed59a73dd4348cc71addbb9,
+    // which contains 0x00 as data
+    if (key.length !== 10) {
+      return undefined;
+    }
+
+    const fourBytes = key.slice(2);
+    const signatureURL = fourBytesURL(assetsURLPrefix, fourBytes);
 
-  try {
     const res = await fetch(signatureURL);
     if (!res.ok) {
-      console.error(`Signature does not exist in 4bytes DB: ${fourBytes}`);
+      console.warn(`Signature does not exist in 4bytes DB: ${fourBytes}`);
       return null;
     }
 
@@ -53,11 +70,7 @@ const fetch4Bytes = async (
       signature: sig,
     };
     return entry;
-  } catch (err) {
-    console.error(`Couldn't fetch signature URL ${signatureURL}`, err);
-    return null;
-  }
-};
+  };
 
 /**
  * Extract 4bytes DB info
@@ -75,26 +88,10 @@ export const use4Bytes = (
 
   const { config } = useContext(RuntimeContext);
   const assetsURLPrefix = config?.assetsURLPrefix;
+  const fourBytesKey = assetsURLPrefix !== undefined ? rawFourBytes : null;
 
-  const fourBytesFetcher = (key: string | null) => {
-    if (key === null || key === "0x") {
-      return undefined;
-    }
-
-    // Handle simple transfers with invalid selector like tx:
-    // 0x8bcbdcc1589b5c34c1e55909c8269a411f0267a4fed59a73dd4348cc71addbb9,
-    // which contains 0x00 as data
-    if (key.length !== 10) {
-      return undefined;
-    }
-
-    return fetch4Bytes(assetsURLPrefix!, key.slice(2));
-  };
-
-  const { data, error } = useSWRImmutable<FourBytesEntry | null | undefined>(
-    assetsURLPrefix !== undefined ? rawFourBytes : null,
-    fourBytesFetcher
-  );
+  const fetcher = fourBytesFetcher(assetsURLPrefix!);
+  const { data, error } = useSWRImmutable(["4bytes", fourBytesKey], fetcher);
   return error ? undefined : data;
 };