package domain

import (
	"context"
	"errors"
	"fmt"
	"strings"
	"time"

	"net/mail"

	validate "backend/pkg/validate/common"

	"github.com/ethereum/go-ethereum/accounts"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/google/uuid"
)

var (
	ErrUserNotFound = errors.New("user not found")
	ErrEmailInvalid = errors.New("email is invalid")
)

type UserRepo interface {
	Create(ctx context.Context, user *User) error
	GetByID(ctx context.Context, id uuid.UUID) (*User, error)
	GetByPhone(ctx context.Context, phone string) (*User, error)
	GetByPubKey(ctx context.Context, pubKey string) (*User, error)
	Update(ctx context.Context, user *User) error
	Delete(ctx context.Context, id uuid.UUID) error
}

type User struct {
	ID     uuid.UUID
	PubKey string
	Name   string
	//TODO: add Kyc Embedded struct
	//TODO: add NFT Embedded struct
	LastName    string
	PhoneNumber string
	Email       *string
	NationalID  string
	BirthDate   *time.Time
	LastLogin   *time.Time
	CreatedAt   time.Time
	UpdatedAt   time.Time
	DeletedAt   *time.Time
}

// TODO: move to another file?
type Challenge struct {
	Message   uuid.UUID
	TimeStamp time.Time
	ExpiresAt time.Time
}

func (c *Challenge) IsExpired() bool {
	return time.Now().After(c.ExpiresAt)
}

func (c *Challenge) Verify(address string, signedMsg string) (bool, error) {
	if c.IsExpired() {
		return false, errors.New("challenge has expired")
	}

	signature, err := hexutil.Decode(signedMsg)
	if err != nil {
		return false, fmt.Errorf("decode signature: %w", err)
	}

	challengeBytes := []byte(c.Message.String())

	return c.VerifySignedBytes(address, challengeBytes, signature)
}

func (c *Challenge) VerifySignedBytes(expectedAddress string, msg []byte, sig []byte) (bool, error) {
	msgHash := accounts.TextHash(msg)

	if len(sig) != 65 {
		return false, fmt.Errorf("invalid signature length: expected 65 bytes, got %d", len(sig))
	}

	if sig[crypto.RecoveryIDOffset] == 27 || sig[crypto.RecoveryIDOffset] == 28 {
		sig[crypto.RecoveryIDOffset] -= 27
	}

	recovered, err := crypto.SigToPub(msgHash, sig)
	if err != nil {
		return false, fmt.Errorf("failed to recover public key: %w", err)
	}
	recoveredAddr := crypto.PubkeyToAddress(*recovered)

	if !common.IsHexAddress(expectedAddress) {
		return false, fmt.Errorf("invalid Ethereum address format: %s", expectedAddress)
	}
	expectedAddr := common.HexToAddress(expectedAddress)

	return strings.EqualFold(expectedAddr.Hex(), recoveredAddr.Hex()), nil
}

func NewUser(pubKey, name, lastName, phoneNumber, email, nationalID string) (*User, error) {

	_, err := validate.IsValidPhone(phoneNumber)
	if err != nil {
		return nil, err
	}

	_, err = validate.IsValidNationalID(nationalID)
	if err != nil {
		return nil, err
	}

	_, err = validate.IsValidPublicKey(pubKey)
	if err != nil {
		return nil, err
	}

	return &User{
		ID:          uuid.New(),
		PubKey:      pubKey,
		Name:        name,
		LastName:    lastName,
		PhoneNumber: phoneNumber,
		NationalID:  nationalID,
		CreatedAt:   time.Now().UTC(),
		UpdatedAt:   time.Now().UTC(),
	}, nil
}

func (u *User) UpdateLastLogin() {
	now := time.Now().UTC()
	u.LastLogin = &now
	u.UpdatedAt = now
}

func (u *User) UpdateInfo(email string) {
	addr, err := mail.ParseAddress(email)
	if err == nil {
		u.Email = &addr.Address
	}
	u.UpdatedAt = time.Now().UTC()
}