<?php

/*
* Copyright 2012 Johannes M. Schmitt <schmittjoh@gmail.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

namespace PhpOption;

use EmptyIterator;

/**
* @extends Option<mixed>
*/
final class None extends Option
{
/** @var None|null */
private static $instance;

/**
* @return None
*/
public static function create(): self
{
if (null === self::$instance) {
self::$instance = new self();
}

return self::$instance;
}

public function get()
{
throw new \RuntimeException('None has no value.');
}

public function getOrCall($callable)
{
return $callable();
}

public function getOrElse($default)
{
return $default;
}

public function getOrThrow(\Exception $ex)
{
throw $ex;
}

public function isEmpty(): bool
{
return true;
}

public function isDefined(): bool
{
return false;
}

public function orElse(Option $else)
{
return $else;
}

public function ifDefined($callable)
{
// Just do nothing in that case.
}

public function forAll($callable)
{
return $this;
}

public function map($callable)
{
return $this;
}

public function flatMap($callable)
{
return $this;
}

public function filter($callable)
{
return $this;
}

public function filterNot($callable)
{
return $this;
}

public function select($value)
{
return $this;
}

public function reject($value)
{
return $this;
}

public function getIterator(): EmptyIterator
{
return new EmptyIterator();
}

public function foldLeft($initialValue, $callable)
{
return $initialValue;
}

public function foldRight($initialValue, $callable)
{
return $initialValue;
}

private function __construct()
{
}
}