/
Principal.php
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/
Principal.php
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<?php
/*
* Copyright 2017, 2018 Alexey Kopytko <alexey@kopytko.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 Pipeline;
/**
* Principal abstract pipeline with no defaults.
*
* You're not expected to use this class directly, but you may subclass it as you see fit.
*/
abstract class Principal implements Interfaces\Pipeline
{
/**
* Pre-primed pipeline.
*
* @var \Traversable
*/
private $pipeline;
/**
* Optional source of data.
*
* @param \Traversable|null $input
*/
public function __construct(\Traversable $input = null)
{
$this->pipeline = $input;
}
public function map(callable $func)
{
if (!$this->pipeline) {
$this->pipeline = call_user_func($func);
// Not a generator means we were given a simple value to be treated as an array
if (!($this->pipeline instanceof \Generator)) {
// We do not cast to an array here because casting a null to an array results in
// an empty array; that's surprising and not how map() works in other cases
$this->pipeline = new \ArrayIterator([
$this->pipeline,
]);
}
return $this;
}
$this->pipeline = (function ($previous) use ($func) {
foreach ($previous as $value) {
$result = $func($value);
if ($result instanceof \Generator) {
// `yield from` does not reset the keys
// iterator_to_array() goes nuts, hence no use for us
// http://php.net/manual/en/language.generators.syntax.php#control-structures.yield.from
foreach ($result as $value) {
yield $value;
}
} else {
// Case of a plain old mapping function
yield $result;
}
}
})($this->pipeline);
return $this;
}
public function filter(callable $func)
{
// Strings usually are internal functions, which require exact number of parameters.
if (is_string($func)) {
$func = function ($value) use ($func) {
return $func($value);
};
}
$this->pipeline = new \CallbackFilterIterator($this->pipeline, $func);
return $this;
}
/**
* @return \Traversable
*/
public function getIterator()
{
return $this->pipeline;
}
public function reduce(callable $func, $initial = null)
{
foreach ($this as $value) {
$initial = $func($initial, $value);
}
return $initial;
}
public function __invoke()
{
foreach ($this as $value) {
yield $value;
}
}
}