package domain

import (
	"fmt"
	"math"
	"strings"

	"telesrv/internal/branding"
)

var officialLoginCodeMessageTemplate = `Login code: %s. Do not give this code to anyone, even if they say they are from ` + branding.ProductName() + `!

This code can be used to log in to your ` + branding.ProductName() + ` account. We never ask it for anything else.

If you didn't request this code by trying to log in on another device, simply ignore this message.`

// LoginCodeDeliveryRequest describes one durable 777000 login-code delivery.
// PhoneCodeHash is an opaque idempotency token and must never be persisted in
// plaintext; store implementations persist only its SHA-256 digest.
type LoginCodeDeliveryRequest struct {
	UserID        int64
	PhoneCodeHash string
	Code          string
	Date          int
	// ExpiresAt is the unix second after which the compact idempotency receipt
	// may be reclaimed. It must cover the corresponding code's usable lifetime.
	ExpiresAt int64
}

// LoginCodeDeliveryResult returns the immutable first delivery. Created is
// false when the same phone_code_hash was already committed and replayed.
type LoginCodeDeliveryResult struct {
	Message Message
	Created bool
}

// OfficialLoginCodeMessage builds the account-visible incoming message from
// Telegram's official notification account. Persistence assigns ID, UID and
// Pts atomically.
func OfficialLoginCodeMessage(userID int64, code string, date int) (Message, error) {
	if userID <= 0 || IsSystemUserID(userID) || strings.TrimSpace(code) == "" || len(code) > 64 || date < 0 || date > math.MaxInt32 {
		return Message{}, fmt.Errorf("%w: user=%d code_length=%d date=%d", ErrLoginCodeDeliveryInvalid, userID, len(code), date)
	}
	body := fmt.Sprintf(officialLoginCodeMessageTemplate, code)
	codeOffset := len("Login code: ")
	return Message{
		OwnerUserID: userID,
		Peer:        Peer{Type: PeerTypeUser, ID: OfficialSystemUserID},
		From:        Peer{Type: PeerTypeUser, ID: OfficialSystemUserID},
		Date:        date,
		Body:        body,
		Entities: []MessageEntity{
			{Type: MessageEntityBold, Offset: 0, Length: len("Login code:")},
			{Type: MessageEntityBold, Offset: codeOffset, Length: len(code)},
		},
	}, nil
}