using System;
using System.Threading.Tasks;
using CellularManagement.Domain.Services;
using Microsoft.Extensions.Caching.Distributed;
using System.Text.Json;

namespace CellularManagement.Infrastructure.Services;

/// <summary>
/// 邮箱验证码服务
/// 提供验证码生成、发送和验证的具体实现
/// </summary>
public class EmailVerificationService : IEmailVerificationService
{
    private readonly IEmailService _emailService;
    private readonly IDistributedCache _cache;
    private const string CacheKeyPrefix = "EmailVerification_";
    private const int VerificationCodeLength = 6;
    private const int VerificationCodeExpirationMinutes = 5;

    /// <summary>
    /// 构造函数
    /// </summary>
    /// <param name="emailService">邮箱服务</param>
    /// <param name="cache">分布式缓存</param>
    public EmailVerificationService(IEmailService emailService, IDistributedCache cache)
    {
        _emailService = emailService;
        _cache = cache;
    }

    /// <summary>
    /// 生成并发送验证码
    /// </summary>
    /// <param name="email">邮箱地址</param>
    /// <returns>是否发送成功</returns>
    public async Task<bool> GenerateAndSendVerificationCodeAsync(string email)
    {
        if (!_emailService.ValidateEmail(email))
        {
            return false;
        }

        // 生成6位数字验证码
        var verificationCode = GenerateVerificationCode();
        
        // 将验证码保存到缓存
        var cacheKey = $"{CacheKeyPrefix}{email}";
        var cacheValue = JsonSerializer.Serialize(new
        {
            Code = verificationCode,
            CreatedAt = DateTime.UtcNow
        });

        await _cache.SetStringAsync(
            cacheKey,
            cacheValue,
            new DistributedCacheEntryOptions
            {
                AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(VerificationCodeExpirationMinutes)
            });

        // 发送验证码邮件
        return await _emailService.SendVerificationCodeAsync(email, verificationCode);
    }

    /// <summary>
    /// 验证验证码
    /// </summary>
    /// <param name="email">邮箱地址</param>
    /// <param name="code">验证码</param>
    /// <returns>验证结果</returns>
    public async Task<bool> VerifyCodeAsync(string email, string code)
    {
        var cacheKey = $"{CacheKeyPrefix}{email}";
        var cachedValue = await _cache.GetStringAsync(cacheKey);

        if (string.IsNullOrEmpty(cachedValue))
        {
            return false;
        }

        var verificationData = JsonSerializer.Deserialize<VerificationData>(cachedValue);
        
        if (verificationData == null)
        {
            return false;
        }

        // 验证码是否过期
        if (DateTime.UtcNow - verificationData.CreatedAt > TimeSpan.FromMinutes(VerificationCodeExpirationMinutes))
        {
            await _cache.RemoveAsync(cacheKey);
            return false;
        }

        // 验证码是否匹配
        if (verificationData.Code != code)
        {
            return false;
        }

        // 验证成功后删除缓存
        await _cache.RemoveAsync(cacheKey);
        return true;
    }

    /// <summary>
    /// 生成验证码
    /// </summary>
    private string GenerateVerificationCode()
    {
        var random = new Random();
        var code = string.Empty;
        
        for (int i = 0; i < VerificationCodeLength; i++)
        {
            code += random.Next(0, 10).ToString();
        }

        return code;
    }

    /// <summary>
    /// 验证数据
    /// </summary>
    private class VerificationData
    {
        public string Code { get; set; } = string.Empty;
        public DateTime CreatedAt { get; set; }
    }
}