package main

import (
	"errors"
	"fmt"
	"strconv"
	"time"

	"github.com/golang-jwt/jwt/v5"
)

var secretKey = []byte("replace-with-env-variable")

type UserClaims struct {
	Name  string `json:"name"`
	Color string `json:"color"`
	jwt.RegisteredClaims
}

func GetToken(user *User) (string, error) {
	token := jwt.NewWithClaims(jwt.SigningMethodHS256,
		UserClaims{
			Name:  user.Name,
			Color: string(user.Color[:]),
			RegisteredClaims: jwt.RegisteredClaims{
				Subject:   strconv.Itoa(int(user.Id)),
				ExpiresAt: jwt.NewNumericDate(time.Now().Add(time.Hour)),
				IssuedAt:  jwt.NewNumericDate(time.Now()),
			},
		},
	)
	return token.SignedString(secretKey)
}

func GetUserFromToken(tokenString string) (User, error) {
	token, err := jwt.ParseWithClaims(tokenString, &UserClaims{}, func(t *jwt.Token) (interface{}, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
		}
		return secretKey, nil
	})
	if err != nil {
		return User{}, err
	}

	claims, ok := token.Claims.(*UserClaims)
	if !ok || !token.Valid {
		return User{}, errors.New("invalid token")
	}

	id, err := strconv.ParseUint(claims.Subject, 10, 64)
	if err != nil {
		return User{}, fmt.Errorf("invalid subject: %w", err)
	}

	var color [3]byte
	copy(color[:], claims.Color)
	return User{
		Id:    id,
		Name:  claims.Name,
		Color: color,
	}, nil
}