<?php
// Some general notes: arguments (aka parameters) are whats sent in to a function (aka method), properties (aka instance variables) are the variables belonging to an object, static variables would be ones ones that exist throughout each instance
// This is the User class, a blueprint of what makes up a user
class User{
    // These are the properties a user will have, we are "declaring" them using a modifier (public) which means we can access them using $userobject->property once we've made a user
    public $id;
    public $username;
    public $password;
    public $email;
    public $permission;

    //__construct is a built in php function called when we instantiate a user object (new User())
    function __construct($user){
        // we take an associative array as input
        foreach($user as $key => $value){
            // for every element in the array, check if there is a corresponding property in User, if so assign its value
            if(property_exists('User', $key))
                $this->$key = $value;
        }
    }
    //result $user = array($id,$username,$password,$email,$permission);

    //static method is in essence a method which does not directly affect any object
    //as you can see it does not alter any properties of an existing user object
    //all it does it get stuff from an existing object and go further (doesn't save over it)

    // log_in is a static function, it will not change any property of a user as it is not part of a particular instance of user,
    // since it's not part of an instance we can't use "$this" (reference to current instance), we can only act on the
    // arguments sent to the method and return some value, in this case we construct a User instance from a username and password
    static function log_in($username, $password){
        //extract the values from the array once they have been escaped
        // NOTE: i had made a mistake here, since we're using func_get_args in esc() we don't need to send in an array
        extract($this->esc($username, $password));
        if(!empty($username) && !empty($password) && ctype_alnum($username)){
            $query =  mysql_query("SELECT * FROM users_tbl WHERE username = '$username' AND password = '".sha1($password)."'");
            if($query){
                $row = mysql_fetch_assoc($query);
                if($row){
                    // we construct a new user from the array we got back from the query
                    $currentuser = new User($row);
                    // we merge the session variable with the properties of our new user, this
                    // will allow us to reconstruct said user from the session variables at a later time
                    $_SESSION = array_merge($_SESSION, get_object_vars($currentuser));
                    return $currentuser;
                }
            }
        }
        // note: false is a result! in fact false is a very useful result, for example it means we can say if(!log_in($usn, $psw)) or if(log_in($usn, $psw)) rather than checking for null or empty etc
        return false;
    }

    // gets the arguments it has been given and makes them all safe
    private function esc($array){
        $args = func_get_args();
        foreach($args as &$value){
            $value = mysql_real_escape_string($value);
        }
        //returns the results in a useable state now that they have been filtered
        return $args;
    }
}

class Controller{
    public $user;
    public $signed_in;

    function handle_actions(){
        if(isset($_POST['login'])){
            //We're using the static function log_in which will return an instance of user (a user object created from our blueprint of what makes up a user) using the username and password provided
            $user = User::log_in($_POST['username'], $_POST['password']);
            if($user)
                //if you're logged in it sets the variables and redirects
                header('Location: /admin/index');
            else
                //if not it takes you back to the error page
                header('Location: /login/error');
            exit;
        }
        // if the use has not just logged in, we check if they were already logged in, we construct a user object from the session variables instead
        elseif(isset($_SESSION['id'], $_SESSION['username'], $_SESSION['password'], $_SESSION['email'], $_SESSION['permission'])){
            $user = new User($_SESSION);
                // Note that i had made a mistake here, the construct won't return a boolean i had copy pasted this from above where log_in does so.
            $this->user = $user;
            $this->signed_in = true;
        }
    }
}
// We have declared above that in our world, there is a type of object called controller
// $ctrl is said to be one particular instance of such an object. It is a "new Controller".
// if you like you could think of it as a class being the definition of a species, and instantiation as saying
// $pedro = new Lion(); where lion is a class and pedro is an object (animal) of that class (species)
$ctrl = new Controller();
// $ctrl->handle_actions calls the handle_actions function belonging to the $ctrl object
$ctrl->handle_actions();
if($ctrl->signed_in)
    echo "I'm a little teapot, short and stout.";
else
    echo "Tip me over and pour me out!";
?>