using System;
using System.Security.Cryptography;
using System.Text;
using NUnit.Framework;

namespace ShrinkDataSaver.Tests
{
    [TestFixture]
    public class SaveEncryptorTests
    {
        [Test]
        public void Encrypt_Decrypt_RoundTrip()
        {
            var original = Encoding.UTF8.GetBytes("Hello, ShrinkDataSaver!");
            var password = "TestPassword123";

            var encrypted = SaveEncryptor.Encrypt(original, password);
            var decrypted = SaveEncryptor.Decrypt(encrypted, password);

            Assert.AreEqual(original, decrypted);
        }

        [Test]
        public void Encrypt_Decrypt_LargeData()
        {
            var original = new byte[10000];
            new System.Random(42).NextBytes(original);
            var password = "LargeDataKey";

            var encrypted = SaveEncryptor.Encrypt(original, password);
            var decrypted = SaveEncryptor.Decrypt(encrypted, password);

            Assert.AreEqual(original, decrypted);
        }

        [Test]
        public void Decrypt_WrongPassword_Throws()
        {
            var original = Encoding.UTF8.GetBytes("secret data");
            var encrypted = SaveEncryptor.Encrypt(original, "correct");

            Assert.Throws<CryptographicException>(() =>
                SaveEncryptor.Decrypt(encrypted, "wrong"));
        }

        [Test]
        public void Encrypt_ProducesDifferentOutput_EachTime()
        {
            var data = Encoding.UTF8.GetBytes("same data");
            var enc1 = SaveEncryptor.Encrypt(data, "key");
            var enc2 = SaveEncryptor.Encrypt(data, "key");

            // 因为随机 salt/IV，两次加密结果不同
            Assert.AreNotEqual(enc1, enc2);

            // 但两次都能正确解密
            Assert.AreEqual(data, SaveEncryptor.Decrypt(enc1, "key"));
            Assert.AreEqual(data, SaveEncryptor.Decrypt(enc2, "key"));
        }

        [Test]
        public void Encrypt_NullData_Throws()
        {
            Assert.Throws<ArgumentNullException>(() =>
                SaveEncryptor.Encrypt(null, "key"));
        }

        [Test]
        public void Encrypt_EmptyPassword_Throws()
        {
            Assert.Throws<ArgumentException>(() =>
                SaveEncryptor.Encrypt(new byte[] { 1, 2, 3 }, ""));
        }

        [Test]
        public void Decrypt_NullData_Throws()
        {
            Assert.Throws<ArgumentNullException>(() =>
                SaveEncryptor.Decrypt(null, "key"));
        }

        [Test]
        public void Decrypt_DataTooShort_Throws()
        {
            Assert.Throws<ArgumentException>(() =>
                SaveEncryptor.Decrypt(new byte[] { 1, 2, 3 }, "key"));
        }
    }
}