package sms

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

	"github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/common"
	"github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/common/profile"
	sms "github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/sms/v20210111"
	"go.uber.org/zap"

	"hyapi-server/internal/config"
)

// TencentSMSService 腾讯云短信（与 bdqr-server 接入方式一致）
type TencentSMSService struct {
	client *sms.Client
	cfg    config.SMSConfig
	logger *zap.Logger
}

// NewTencentSMSService 创建腾讯云短信客户端
func NewTencentSMSService(cfg config.SMSConfig, logger *zap.Logger) (*TencentSMSService, error) {
	tc := cfg.TencentCloud
	if tc.SecretId == "" || tc.SecretKey == "" {
		return nil, fmt.Errorf("腾讯云短信未配置 secret_id / secret_key")
	}
	credential := common.NewCredential(tc.SecretId, tc.SecretKey)
	cpf := profile.NewClientProfile()
	cpf.HttpProfile.ReqMethod = "POST"
	cpf.HttpProfile.ReqTimeout = 10
	cpf.HttpProfile.Endpoint = "sms.tencentcloudapi.com"
	if tc.Endpoint != "" {
		cpf.HttpProfile.Endpoint = tc.Endpoint
	}

	region := tc.Region
	if region == "" {
		region = "ap-guangzhou"
	}

	client, err := sms.NewClient(credential, region, cpf)
	if err != nil {
		return nil, fmt.Errorf("创建腾讯云短信客户端失败: %w", err)
	}

	return &TencentSMSService{
		client: client,
		cfg:    cfg,
		logger: logger,
	}, nil
}

func normalizeTencentPhone(phone string) string {
	if strings.HasPrefix(phone, "+86") {
		return phone
	}
	return "+86" + phone
}

// SendVerificationCode 发送验证码（模板参数为单个验证码，与 bdqr 一致）
func (s *TencentSMSService) SendVerificationCode(ctx context.Context, phone string, code string) error {
	tc := s.cfg.TencentCloud
	request := &sms.SendSmsRequest{}
	request.SmsSdkAppId = common.StringPtr(tc.SmsSdkAppId)
	request.SignName = common.StringPtr(tc.SignName)
	request.TemplateId = common.StringPtr(tc.TemplateID)
	request.TemplateParamSet = common.StringPtrs([]string{code})
	request.PhoneNumberSet = common.StringPtrs([]string{normalizeTencentPhone(phone)})

	response, err := s.client.SendSms(request)
	if err != nil {
		s.logger.Error("腾讯云短信发送失败",
			zap.String("phone", phone),
			zap.Error(err))
		return fmt.Errorf("短信发送失败: %w", err)
	}

	if response.Response == nil || len(response.Response.SendStatusSet) == 0 {
		return fmt.Errorf("腾讯云短信返回空响应")
	}

	st := response.Response.SendStatusSet[0]
	if st.Code == nil || *st.Code != "Ok" {
		msg := ""
		if st.Message != nil {
			msg = *st.Message
		}
		s.logger.Error("腾讯云短信业务失败",
			zap.String("phone", phone),
			zap.String("message", msg))
		return fmt.Errorf("短信发送失败: %s", msg)
	}

	s.logger.Info("腾讯云短信发送成功",
		zap.String("phone", phone),
		zap.String("serial_no", safeStrPtr(st.SerialNo)))

	return nil
}

// SendBalanceAlert 发送余额类预警。低余额与欠费使用不同模板（见 low_balance_template_id / arrears_template_id），
// 若未分别配置则回退 balance_alert_template_id。除验证码外，腾讯云短信按无变量模板发送。
func (s *TencentSMSService) SendBalanceAlert(ctx context.Context, phone string, balance float64, threshold float64, alertType string, enterpriseName ...string) error {
	tc := s.cfg.TencentCloud
	tplID := resolveTencentBalanceTemplateID(tc, alertType)
	if tplID == "" {
		return fmt.Errorf("腾讯云余额类短信模板未配置（请设置 sms.tencent_cloud.low_balance_template_id 与 arrears_template_id，或回退 balance_alert_template_id）")
	}

	request := &sms.SendSmsRequest{}
	request.SmsSdkAppId = common.StringPtr(tc.SmsSdkAppId)
	request.SignName = common.StringPtr(tc.SignName)
	request.TemplateId = common.StringPtr(tplID)
	request.PhoneNumberSet = common.StringPtrs([]string{normalizeTencentPhone(phone)})

	response, err := s.client.SendSms(request)
	if err != nil {
		s.logger.Error("腾讯云余额预警短信失败",
			zap.String("phone", phone),
			zap.String("alert_type", alertType),
			zap.Error(err))
		return fmt.Errorf("短信发送失败: %w", err)
	}

	if response.Response == nil || len(response.Response.SendStatusSet) == 0 {
		return fmt.Errorf("腾讯云短信返回空响应")
	}

	st := response.Response.SendStatusSet[0]
	if st.Code == nil || *st.Code != "Ok" {
		msg := ""
		if st.Message != nil {
			msg = *st.Message
		}
		return fmt.Errorf("短信发送失败: %s", msg)
	}

	s.logger.Info("腾讯云余额预警短信发送成功",
		zap.String("phone", phone),
		zap.String("alert_type", alertType))

	return nil
}

// GenerateCode 生成数字验证码
func (s *TencentSMSService) GenerateCode(length int) string {
	if length <= 0 {
		length = 6
	}
	max := big.NewInt(int64(pow10Tencent(length)))
	n, _ := rand.Int(rand.Reader, max)
	format := fmt.Sprintf("%%0%dd", length)
	return fmt.Sprintf(format, n.Int64())
}

func safeStrPtr(p *string) string {
	if p == nil {
		return ""
	}
	return *p
}

func pow10Tencent(n int) int {
	result := 1
	for i := 0; i < n; i++ {
		result *= 10
	}
	return result
}

func resolveTencentBalanceTemplateID(tc config.TencentSMSConfig, alertType string) string {
	switch alertType {
	case "low_balance":
		if tc.LowBalanceTemplateID != "" {
			return tc.LowBalanceTemplateID
		}
	case "arrears":
		if tc.ArrearsTemplateID != "" {
			return tc.ArrearsTemplateID
		}
	}
	return tc.BalanceAlertTemplateID
}