<?php
namespace GuzzleHttp\Stream;

use GuzzleHttp\Stream\Exception\CannotAttachException;

/**
* Provides a read only stream that pumps data from a PHP callable.
*
* When invoking the provided callable, the PumpStream will pass the amount of
* data requested to read to the callable. The callable can choose to ignore
* this value and return fewer or more bytes than requested. Any extra data
* returned by the provided callable is buffered internally until drained using
* the read() function of the PumpStream. The provided callable MUST return
* false when there is no more data to read.
*/
class PumpStream implements StreamInterface
{
/** @var callable */
private $source;

/** @var int */
private $size;

/** @var int */
private $tellPos = 0;

/** @var array */
private $metadata;

/** @var BufferStream */
private $buffer;

/**
* @param callable $source Source of the stream data. The callable MAY
* accept an integer argument used to control the
* amount of data to return. The callable MUST
* return a string when called, or false on error
* or EOF.
* @param array $options Stream options:
* - metadata: Hash of metadata to use with stream.
* - size: Size of the stream, if known.
*/
public function __construct(callable $source, array $options = [])
{
$this->source = $source;
$this->size = isset($options['size']) ? $options['size'] : null;
$this->metadata = isset($options['metadata']) ? $options['metadata'] : [];
$this->buffer = new BufferStream();
}

public function __toString()
{
return Utils::copyToString($this);
}

public function close()
{
$this->detach();
}

public function detach()
{
$this->tellPos = false;
$this->source = null;
}

public function attach($stream)
{
throw new CannotAttachException();
}

public function getSize()
{
return $this->size;
}

public function tell()
{
return $this->tellPos;
}

public function eof()
{
return !$this->source;
}

public function isSeekable()
{
return false;
}

public function seek($offset, $whence = SEEK_SET)
{
return false;
}

public function isWritable()
{
return false;
}

public function write($string)
{
return false;
}

public function isReadable()
{
return true;
}

public function read($length)
{
$data = $this->buffer->read($length);
$readLen = strlen($data);
$this->tellPos += $readLen;
$remaining = $length - $readLen;

if ($remaining) {
$this->pump($remaining);
$data .= $this->buffer->read($remaining);
$this->tellPos += strlen($data) - $readLen;
}

return $data;
}

public function getContents()
{
$result = '';
while (!$this->eof()) {
$result .= $this->read(1000000);
}

return $result;
}

public function getMetadata($key = null)
{
if (!$key) {
return $this->metadata;
}

return isset($this->metadata[$key]) ? $this->metadata[$key] : null;
}

private function pump($length)
{
if ($this->source) {
do {
$data = call_user_func($this->source, $length);
if ($data === false || $data === null) {
$this->source = null;
return;
}
$this->buffer->write($data);
$length -= strlen($data);
} while ($length > 0);
}
}
}