feat: friendly way to inform user there's an error (#12)

src/decrypt-worker/util/DecryptError.ts

@@ -1 +1,17 @@
-export class UnsupportedSourceFile extends Error {}
+export enum DecryptErrorType {
+  UNSUPPORTED_FILE = 'UNSUPPORTED_FILE',
+  UNKNOWN = 'UNKNOWN',
+}
+
+export class DecryptError extends Error {
+  code = DecryptErrorType.UNKNOWN;
+
+  toJSON() {
+    const { name, message, stack, code } = this;
+    return { name, message, stack, code };
+  }
+}
+
+export class UnsupportedSourceFile extends DecryptError {
+  code = DecryptErrorType.UNSUPPORTED_FILE;
+}

src/decrypt-worker/worker/handler/decrypt.ts

@@ -38,7 +38,7 @@ class DecryptCommandHandler {
       }
     }
 
-    throw new Error('could not decrypt file: no working decryptor found');
+    throw new UnsupportedSourceFile('could not decrypt file: no working decryptor found');
   }
 
   async decryptFile(crypto: CryptoBase) {