added FileKeypair class

ts/scripts/keypair.ts

@@ -0,0 +1,8 @@
+import { FileKeypair } from "../src";
+
+const main = async () => {
+  const keypair = FileKeypair.loadOrGenerate("./test.json");
+  console.log(keypair.keypair.publicKey.toString());
+};
+
+main();

ts/src/fileKeypair.ts

@@ -0,0 +1,42 @@
+import { Keypair } from "@solana/web3.js";
+import fs from "fs";
+
+export class FileKeypair {
+  public filePath: string;
+  public keypair: Keypair;
+
+  constructor(filePath: string, keypair: Keypair) {
+    this.filePath = filePath;
+    this.keypair = keypair;
+  }
+
+  static load(filePath: string): FileKeypair {
+    const fileBuffer = fs.readFileSync(filePath);
+    const secretKey: number[] = JSON.parse(fileBuffer.toString());
+    const keypair = Keypair.fromSecretKey(Uint8Array.from(secretKey));
+    return new FileKeypair(filePath, keypair);
+  }
+
+  static generate(filepath: string): FileKeypair {
+    const keypair = Keypair.generate();
+    const secretKey = Array.from(keypair.secretKey);
+    fs.writeFileSync(filepath, JSON.stringify(secretKey));
+    return new FileKeypair(filepath, keypair);
+  }
+
+  static loadOrGenerate(filePath: string): FileKeypair {
+    let keypair: Keypair;
+    let secretKey: number[];
+    try {
+      const fileBuffer = fs.readFileSync(filePath);
+      secretKey = JSON.parse(fileBuffer.toString());
+      keypair = Keypair.fromSecretKey(Uint8Array.from(secretKey));
+    } catch (e) {
+      keypair = Keypair.generate();
+      secretKey = Array.from(keypair.secretKey);
+      fs.writeFileSync(filePath, JSON.stringify(secretKey));
+    }
+
+    return new FileKeypair(filePath, keypair);
+  }
+}

ts/src/index.ts

@@ -1,3 +1,4 @@
 export * from "./dex";
 export * from "./coin";
 export * from "./market";
+export * from "./fileKeypair";