package service

import (
	"context"
	"crypto/rand"
	"fmt"
	"math/big"
	"time"

	"carrotskin/pkg/config"
	"carrotskin/pkg/email"
	"carrotskin/pkg/redis"
)

const (
	// 验证码类型
	VerificationTypeRegister      = "register"
	VerificationTypeResetPassword = "reset_password"
	VerificationTypeChangeEmail   = "change_email"

	// 验证码配置
	CodeLength     = 6                // 验证码长度
	CodeExpiration = 10 * time.Minute // 验证码有效期
	CodeRateLimit  = 1 * time.Minute  // 发送频率限制
)

// verificationService VerificationService的实现
type verificationService struct {
	redis        *redis.Client
	emailService *email.Service
}

// NewVerificationService 创建VerificationService实例
func NewVerificationService(
	redisClient *redis.Client,
	emailService *email.Service,
) VerificationService {
	return &verificationService{
		redis:        redisClient,
		emailService: emailService,
	}
}

// SendCode 发送验证码
func (s *verificationService) SendCode(ctx context.Context, email, codeType string) error {
	// 测试环境下直接跳过，不存储也不发送
	cfg, err := config.GetConfig()
	if err == nil && cfg.IsTestEnvironment() {
		return nil
	}

	// 检查发送频率限制
	rateLimitKey := fmt.Sprintf("verification:rate_limit:%s:%s", codeType, email)
	exists, err := s.redis.Exists(ctx, rateLimitKey)
	if err != nil {
		return fmt.Errorf("检查发送频率失败: %w", err)
	}
	if exists > 0 {
		return fmt.Errorf("发送过于频繁，请稍后再试")
	}

	// 生成验证码
	code, err := s.generateCode()
	if err != nil {
		return fmt.Errorf("生成验证码失败: %w", err)
	}

	// 存储验证码到Redis
	codeKey := fmt.Sprintf("verification:code:%s:%s", codeType, email)
	if err := s.redis.Set(ctx, codeKey, code, CodeExpiration); err != nil {
		return fmt.Errorf("存储验证码失败: %w", err)
	}

	// 设置发送频率限制
	if err := s.redis.Set(ctx, rateLimitKey, "1", CodeRateLimit); err != nil {
		return fmt.Errorf("设置发送频率限制失败: %w", err)
	}

	// 发送邮件
	if err := s.sendEmail(email, code, codeType); err != nil {
		// 发送失败，删除验证码
		_ = s.redis.Del(ctx, codeKey)
		return fmt.Errorf("发送邮件失败: %w", err)
	}

	return nil
}

// VerifyCode 验证验证码
func (s *verificationService) VerifyCode(ctx context.Context, email, code, codeType string) error {
	// 测试环境下直接通过验证
	cfg, err := config.GetConfig()
	if err == nil && cfg.IsTestEnvironment() {
		return nil
	}

	// 检查是否被锁定
	locked, ttl, err := CheckVerifyLocked(ctx, s.redis, email, codeType)
	if err == nil && locked {
		return fmt.Errorf("验证码错误次数过多，请在 %d 分钟后重试", int(ttl.Minutes())+1)
	}

	codeKey := fmt.Sprintf("verification:code:%s:%s", codeType, email)

	// 从Redis获取验证码
	storedCode, err := s.redis.Get(ctx, codeKey)
	if err != nil {
		// 记录失败尝试并检查是否触发锁定
		count, _ := RecordVerifyFailure(ctx, s.redis, email, codeType)
		if count >= MaxVerifyAttempts {
			return fmt.Errorf("验证码错误次数过多，账号已被锁定 %d 分钟", int(VerifyLockDuration.Minutes()))
		}
		remaining := MaxVerifyAttempts - count
		if remaining > 0 {
			return fmt.Errorf("验证码已过期或不存在，还剩 %d 次尝试机会", remaining)
		}
		return fmt.Errorf("验证码已过期或不存在")
	}

	// 验证验证码
	if storedCode != code {
		// 记录失败尝试并检查是否触发锁定
		count, _ := RecordVerifyFailure(ctx, s.redis, email, codeType)
		if count >= MaxVerifyAttempts {
			return fmt.Errorf("验证码错误次数过多，账号已被锁定 %d 分钟", int(VerifyLockDuration.Minutes()))
		}
		remaining := MaxVerifyAttempts - count
		if remaining > 0 {
			return fmt.Errorf("验证码错误，还剩 %d 次尝试机会", remaining)
		}
		return fmt.Errorf("验证码错误")
	}

	// 验证成功，删除验证码和失败计数
	_ = s.redis.Del(ctx, codeKey)
	_ = ClearVerifyAttempts(ctx, s.redis, email, codeType)

	return nil
}

// generateCode 生成6位数字验证码
func (s *verificationService) generateCode() (string, error) {
	const digits = "0123456789"
	code := make([]byte, CodeLength)
	for i := range code {
		num, err := rand.Int(rand.Reader, big.NewInt(int64(len(digits))))
		if err != nil {
			return "", err
		}
		code[i] = digits[num.Int64()]
	}
	return string(code), nil
}

// sendEmail 根据类型发送邮件
func (s *verificationService) sendEmail(to, code, codeType string) error {
	switch codeType {
	case VerificationTypeRegister:
		return s.emailService.SendEmailVerification(to, code)
	case VerificationTypeResetPassword:
		return s.emailService.SendResetPassword(to, code)
	case VerificationTypeChangeEmail:
		return s.emailService.SendChangeEmail(to, code)
	default:
		return s.emailService.SendVerificationCode(to, code, codeType)
	}
}

// DeleteVerificationCode 删除验证码（工具函数，保持向后兼容）
func DeleteVerificationCode(ctx context.Context, redisClient *redis.Client, email, codeType string) error {
	codeKey := fmt.Sprintf("verification:code:%s:%s", codeType, email)
	return redisClient.Del(ctx, codeKey)
}