package logic

import (
	"context"
	"crypto/rand"
	"encoding/binary"
	"fmt"

	smsentity "spark-server/internal/module/sms/entity"
	userentity "spark-server/internal/module/user/entity"
)

const (
	defaultCodeTTLSeconds      = 300
	defaultCodeCooldownSeconds = 60
)

// CodeTTLSeconds is the OTP lifetime returned to clients.
const CodeTTLSeconds = defaultCodeTTLSeconds

// AccountEmail resolves the bound mailbox for an authenticated user (account delete OTP).
type AccountEmail interface {
	EmailByUserID(ctx context.Context, userID int64) (string, error)
}

// Service issues and checks OTPs for email and phone.
type Service struct {
	store    CodeStore
	email    EmailSender
	phone    []PhoneCarrierSender
	accounts AccountEmail
}

func NewService(store CodeStore, email EmailSender, phone []PhoneCarrierSender, accounts AccountEmail) *Service {
	return &Service{store: store, email: email, phone: phone, accounts: accounts}
}

func storeKey(ch smsentity.Channel, purpose smsentity.Purpose, target string) string {
	return fmt.Sprintf("%d:%d:%s", ch, purpose, target)
}

func randomDigits(n int) (string, error) {
	if n <= 0 {
		return "", fmt.Errorf("digits")
	}
	var buf [8]byte
	out := make([]byte, n)
	for i := 0; i < n; i++ {
		if _, err := rand.Read(buf[:4]); err != nil {
			return "", err
		}
		out[i] = '0' + byte(binary.BigEndian.Uint32(buf[:4])%10)
	}
	return string(out), nil
}

func skipSendEmail(email string) bool {
	return userentity.IsTestEmail(email)
}

func skipSendPhone(phone string) bool {
	// Dev-friendly test MSISDNs matching spark test convention.
	switch phone {
	case "+8613800138000", "+8613800138001", "+8613800138002":
		return true
	default:
		return false
	}
}