package services

import (
	"errors"
	"time"

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

var (
	users = map[string]string{
		"henri": "henri123",
	}
	secret = []byte("mein-secret")
)

type Session struct {
	Username string
	Expiry   time.Time
}

type Credentials struct {
	Password string
	Username string
}

func (s Session) IsExpired() bool {
	return s.Expiry.Before(time.Now())
}

func Signin(cred Credentials) (string, time.Time, error) {
	expectedPassword, ok := users[cred.Username]
	if !ok || expectedPassword != cred.Password {
		return "", time.Time{}, errors.New("wrong password")
	}

	expiresAt := time.Now().Add(2 * time.Hour)

	sessionToken, err := tokenFromSession(Session{
		Username: cred.Username,
		Expiry:   expiresAt,
	})

	if err != nil {
		return "", time.Time{}, err
	}

	return sessionToken, expiresAt, nil
}

func GetSession(sessionToken string) (*Session, error) {
	return sessionFromToken(sessionToken)
}

func RemoveSession(sessionID string) {
}

func tokenFromSession(session Session) (string, error) {
	token := jwt.NewWithClaims(jwt.SigningMethodHS256,
		jwt.MapClaims{
			"username": session.Username,
			"exp":      session.Expiry.Unix(),
		})

	return token.SignedString(secret)
}

func sessionFromToken(tokenString string) (*Session, error) {
	sessionToken, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
		return secret, nil
	})

	if err != nil {
		return nil, err
	}

	if !sessionToken.Valid {
		return nil, errors.New("invalid token")
	}

	if claims, ok := sessionToken.Claims.(jwt.MapClaims); ok {
		expiresAt := time.Unix(int64(claims["exp"].(float64)), 0)
		return &Session{
			Username: claims["username"].(string),
			Expiry:   expiresAt,
		}, nil
	} else {
		return nil, errors.New("cannot read claims")
	}
}