using System;
using System.Security.Cryptography;
using System.Text;

namespace 全自动水压检测仪.DATA
{
    /// <summary>
    /// 密码加密辅助类
    /// 使用 SHA256 + 盐值加密
    /// 精确简单的实现，确保100%匹配
    /// </summary>
    public static class PasswordHelper
    {
        /// <summary>
        /// 生成随机盐值（16字节）
        /// </summary>
        /// <returns>Base64编码的盐值字符串</returns>
        public static string GenerateSalt()
        {
            byte[] saltBytes = new byte[16];
            using (var rng = new RNGCryptoServiceProvider())
            {
                rng.GetBytes(saltBytes);
            }
            return Convert.ToBase64String(saltBytes);
        }

        /// <summary>
        /// 使用 SHA256 哈希密码
        /// 精确实现：密码 + 盐值 -> SHA256 -> Base64
        /// </summary>
        /// <param name="password">明文密码</param>
        /// <param name="salt">盐值</param>
        /// <returns>Base64编码的密码哈希值</returns>
        public static string HashPassword(string password, string salt)
        {
            if (string.IsNullOrEmpty(password))
                throw new ArgumentNullException(nameof(password));
            
            if (string.IsNullOrEmpty(salt))
                throw new ArgumentNullException(nameof(salt));

            // 拼接密码和盐值
            string combined = password + salt;
            
            // 转换为字节数组
            byte[] combinedBytes = Encoding.UTF8.GetBytes(combined);
            
            // 计算 SHA256 哈希
            using (var sha256 = SHA256.Create())
            {
                byte[] hashBytes = sha256.ComputeHash(combinedBytes);
                
                // 转换为 Base64 字符串
                string hash = Convert.ToBase64String(hashBytes);
                
                return hash;
            }
        }

        /// <summary>
        /// 验证密码是否匹配
        /// 精确实现：重新计算哈希并比较
        /// </summary>
        /// <param name="inputPassword">输入的明文密码</param>
        /// <param name="storedHash">存储的密码哈希值</param>
        /// <param name="salt">盐值</param>
        /// <returns>密码是否匹配</returns>
        public static bool VerifyPassword(string inputPassword, string storedHash, string salt)
        {
            if (string.IsNullOrEmpty(inputPassword))
                return false;
            
            if (string.IsNullOrEmpty(storedHash))
                return false;
            
            if (string.IsNullOrEmpty(salt))
                return false;

            try
            {
                // 使用相同的方法计算输入密码的哈希
                string inputHash = HashPassword(inputPassword, salt);
                
                // 精确比较（区分大小写）
                bool isMatch = string.Equals(inputHash, storedHash, StringComparison.Ordinal);
                
                // 调试输出
                System.Diagnostics.Debug.WriteLine($"[密码验证]");
                System.Diagnostics.Debug.WriteLine($"  输入密码: {inputPassword}");
                System.Diagnostics.Debug.WriteLine($"  盐值: {salt}");
                System.Diagnostics.Debug.WriteLine($"  计算的哈希: {inputHash}");
                System.Diagnostics.Debug.WriteLine($"  存储的哈希: {storedHash}");
                System.Diagnostics.Debug.WriteLine($"  是否匹配: {isMatch}");
                
                return isMatch;
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine($"[密码验证异常] {ex.Message}");
                return false;
            }
        }

        /// <summary>
        /// 测试密码加密功能
        /// </summary>
        public static void TestPasswordEncryption()
        {
            System.Diagnostics.Debug.WriteLine("=== 测试密码加密功能 ===");
            
            // 测试 1: admin123
            string salt1 = GenerateSalt();
            string hash1 = HashPassword("admin123", salt1);
            bool verify1 = VerifyPassword("admin123", hash1, salt1);
            
            System.Diagnostics.Debug.WriteLine($"\n测试 1: admin123");
            System.Diagnostics.Debug.WriteLine($"  盐值: {salt1}");
            System.Diagnostics.Debug.WriteLine($"  哈希: {hash1}");
            System.Diagnostics.Debug.WriteLine($"  验证: {verify1} (应该为 True)");
            
            // 测试 2: 123
            string salt2 = GenerateSalt();
            string hash2 = HashPassword("123", salt2);
            bool verify2 = VerifyPassword("123", hash2, salt2);
            
            System.Diagnostics.Debug.WriteLine($"\n测试 2: 123");
            System.Diagnostics.Debug.WriteLine($"  盐值: {salt2}");
            System.Diagnostics.Debug.WriteLine($"  哈希: {hash2}");
            System.Diagnostics.Debug.WriteLine($"  验证: {verify2} (应该为 True)");
            
            // 测试 3: 错误密码
            bool verify3 = VerifyPassword("wrongpassword", hash1, salt1);
            System.Diagnostics.Debug.WriteLine($"\n测试 3: 错误密码");
            System.Diagnostics.Debug.WriteLine($"  验证: {verify3} (应该为 False)");
            
            System.Diagnostics.Debug.WriteLine("\n=== 测试完成 ===\n");
        }
    }
}