package auth

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

	"haixun-backend/internal/library/clock"
	"haixun-backend/internal/model/member/domain/entity"
	"haixun-backend/internal/svc"

	"github.com/zeromicro/go-zero/core/logx"
)

const emailVerificationTTL = 15 * time.Minute
const emailVerificationResendCooldown = 60 * time.Second

func newVerifyCode() (string, error) {
	n, err := rand.Int(rand.Reader, big.NewInt(1000000))
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("%06d", n.Int64()), nil
}

func requiresNativeEmailVerification(member *entity.Member) bool {
	if member == nil {
		return false
	}
	return member.Origin == "" || member.Origin == entity.OriginNative
}

func issueAndSendEmailVerification(ctx context.Context, svcCtx *svc.ServiceContext, member *entity.Member) error {
	verifyCode, err := newVerifyCode()
	if err != nil {
		return err
	}
	expiresAt := clock.NowUnixNano() + int64(emailVerificationTTL)
	if err := svcCtx.Member.SetEmailVerificationCode(ctx, member.TenantID, member.UID, verifyCode, expiresAt); err != nil {
		return err
	}
	if err := sendEmailVerification(ctx, svcCtx, member.Email, verifyCode); err != nil {
		logx.WithContext(ctx).Errorf("send verification email failed: uid=%s err=%v", member.UID, err)
	}
	return nil
}

func sendEmailVerification(ctx context.Context, svcCtx *svc.ServiceContext, email, verifyCode string) error {
	if svcCtx.Mailer == nil {
		return nil
	}
	body := fmt.Sprintf("你的巡樓 Console 驗證碼是：%s\n\n此驗證碼 15 分鐘內有效。", verifyCode)
	if err := svcCtx.Mailer.Send(ctx, email, "巡樓 Console 帳號驗證碼", body); err != nil {
		logx.WithContext(ctx).Errorf("send verification email failed: email=%s err=%v", email, err)
		return err
	}
	return nil
}

func maybeSendLoginVerificationEmail(ctx context.Context, svcCtx *svc.ServiceContext, member *entity.Member) {
	if member == nil || !requiresNativeEmailVerification(member) || member.EmailVerified {
		return
	}
	if member.EmailVerifyCode != "" && member.EmailVerifyExpiresAt > clock.NowUnixNano() {
		return
	}
	_ = issueAndSendEmailVerification(ctx, svcCtx, member)
}

func emailVerificationSentRecently(member *entity.Member) bool {
	if member == nil || member.EmailVerifyExpiresAt <= 0 {
		return false
	}
	sentAt := member.EmailVerifyExpiresAt - int64(emailVerificationTTL)
	return clock.NowUnixNano()-sentAt < int64(emailVerificationResendCooldown)
}