fix: preserve leading zeros for cairo bytes data

Author: penovicp

__tests__/utils/cairoDataTypes/CairoByteArray.test.ts

@@ -701,5 +701,19 @@ describe('CairoByteArray Unit Tests', () => {
         expect(apiRequest1).toEqual(apiRequest2);
       });
     });
+
+    test('should preserve data leading zeros for toApiRequest()', () => {
+      const content =
+        '0x' +
+        '000000019900000000000002222222374206275726e206d65737aaaa000001' +
+        '000000029900000000000002222222374206275726e206d65737aaaa000002' +
+        '000000039900000000000002222222374206275726e206d65737aaaa000003';
+      const buffer = Buffer.from(content.slice(2), 'hex');
+      const byteArray = new CairoByteArray(buffer);
+      const apiRequest = byteArray.toApiRequest();
+      const reconstructedByteArray = CairoByteArray.factoryFromApiResponse(apiRequest.values());
+
+      expect(reconstructedByteArray.toHexString()).toEqual(content);
+    });
   });
 });

__tests__/utils/cairoDataTypes/CairoBytes31.test.ts

@@ -126,7 +126,7 @@ describe('CairoBytes31 class Unit Tests', () => {
     });
   });
 
-  describe('toUnicode method', () => {
+  describe('decodeUtf8 method', () => {
     test('should convert ASCII text back to original string', () => {
       const text = 'hello world';
       const bytes31 = new CairoBytes31(text);
@@ -200,7 +200,7 @@ describe('CairoBytes31 class Unit Tests', () => {
     test('should convert Uint8Array to hex', () => {
       const array = new Uint8Array([1, 2, 3, 4]);
       const bytes31 = new CairoBytes31(array);
-      expect(bytes31.toHexString()).toBe('0x1020304');
+      expect(bytes31.toHexString()).toBe('0x01020304');
     });
 
     test('should handle maximum length data', () => {
@@ -209,6 +209,12 @@ describe('CairoBytes31 class Unit Tests', () => {
       const expectedHex = `0x${'ff'.repeat(31)}`;
       expect(bytes31.toHexString()).toBe(expectedHex);
     });
+
+    test('should preserve leading zero values', () => {
+      const buffer = Buffer.from([0, 0, 1]);
+      const bytes31 = new CairoBytes31(buffer);
+      expect(bytes31.toHexString()).toEqual(`0x${buffer.toString('hex')}`);
+    });
   });
 
   describe('toApiRequest method', () => {
@@ -230,7 +236,7 @@ describe('CairoBytes31 class Unit Tests', () => {
     test('should return hex string array for Buffer input', () => {
       const buffer = Buffer.from([1, 0]); // 0x0100 = 256
       const bytes31 = new CairoBytes31(buffer);
-      expect(bytes31.toApiRequest()).toEqual(['0x100']);
+      expect(bytes31.toApiRequest()).toEqual(['0x0100']);
     });
 
     test('should return hex string array for large values', () => {

src/utils/cairoDataTypes/bytes31.ts

@@ -1,5 +1,5 @@
 /* eslint-disable no-underscore-dangle */
-import { addHexPrefix, stringToUint8Array, uint8ArrayToBigInt } from '../encode';
+import { addHexPrefix, buf2hex, stringToUint8Array, uint8ArrayToBigInt } from '../encode';
 import { getNext } from '../num';
 import assert from '../assert';
 import { addCompiledFlag } from '../helpers';
@@ -22,7 +22,7 @@ export class CairoBytes31 {
       return stringToUint8Array(data);
     }
     if (isBuffer(data)) {
-      return new Uint8Array(data as Buffer);
+      return new Uint8Array(data);
     }
     if (data instanceof Uint8Array) {
       return new Uint8Array(data);
@@ -43,7 +43,11 @@ export class CairoBytes31 {
   }
 
   toHexString() {
-    return addHexPrefix(this.toBigInt().toString(16));
+    // TODO: revisit empty data handling for CairoBytes31 and CairoByteArray
+    // how to differentiate empty and zero input
+    const hexValue = this.data.length === 0 ? '0' : buf2hex(this.data);
+
+    return addHexPrefix(hexValue);
   }
 
   static validate(data: Uint8Array | string | Buffer | unknown): void {