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<?php

namespace GuzzleHttp\Psr7;

use Psr\Http\Message\StreamInterface;

/**

 * Reads from multiple streams, one after the other.

 *

 * This is a read-only stream decorator.

 */

class AppendStream implements StreamInterface

{

    /** @var StreamInterface[] Streams being decorated */

    private $streams = [];

    private $seekable = true;

    private $current = 0;

    private $pos = 0;

    private $detached = false;

    /**

     * @param StreamInterface[] $streams Streams to decorate. Each stream must

     *                                   be readable.

     */

    public function __construct(array $streams = [])

    {

        foreach ($streams as $stream) {

            $this->addStream($stream);

        }

    }

    public function __toString()

    {

        try {

            $this->rewind();

            return $this->getContents();

        } catch (\Exception $e) {

            return '';

        }

    }

    /**

     * Add a stream to the AppendStream

     *

     * @param StreamInterface $stream Stream to append. Must be readable.

     *

     * @throws \InvalidArgumentException if the stream is not readable

     */

    public function addStream(StreamInterface $stream)

    {

        if (!$stream->isReadable()) {

            throw new \InvalidArgumentException('Each stream must be readable');

        }

        // The stream is only seekable if all streams are seekable

        if (!$stream->isSeekable()) {

            $this->seekable = false;

        }

        $this->streams[] = $stream;

    }

    public function getContents()

    {

        return copy_to_string($this);

    }

    /**

     * Closes each attached stream.

     *

     * {@inheritdoc}

     */

    public function close()

    {

        $this->pos = $this->current = 0;

        foreach ($this->streams as $stream) {

            $stream->close();

        }

        $this->streams = [];

    }

    /**

     * Detaches each attached stream

     *

     * {@inheritdoc}

     */

    public function detach()

    {

        $this->close();

        $this->detached = true;

    }

    public function tell()

    {

        return $this->pos;

    }

    /**

     * Tries to calculate the size by adding the size of each stream.

     *

     * If any of the streams do not return a valid number, then the size of the

     * append stream cannot be determined and null is returned.

     *

     * {@inheritdoc}

     */

    public function getSize()

    {

        $size = 0;

        foreach ($this->streams as $stream) {

            $s = $stream->getSize();

            if ($s === null) {

                return null;

            }

            $size += $s;

        }

        return $size;

    }

    public function eof()

    {

        return !$this->streams ||

            ($this->current >= count($this->streams) - 1 &&

             $this->streams[$this->current]->eof());

    }

    public function rewind()

    {

        $this->seek(0);

    }

    /**

     * Attempts to seek to the given position. Only supports SEEK_SET.

     *

     * {@inheritdoc}

     */

    public function seek($offset, $whence = SEEK_SET)

    {

        if (!$this->seekable) {

            throw new \RuntimeException('This AppendStream is not seekable');

        } elseif ($whence !== SEEK_SET) {

            throw new \RuntimeException('The AppendStream can only seek with SEEK_SET');

        }

        $this->pos = $this->current = 0;

        // Rewind each stream

        foreach ($this->streams as $i => $stream) {

            try {

                $stream->rewind();

            } catch (\Exception $e) {

                throw new \RuntimeException('Unable to seek stream '

                    . $i . ' of the AppendStream', 0, $e);

            }

        }

        // Seek to the actual position by reading from each stream

        while ($this->pos < $offset && !$this->eof()) {

            $result = $this->read(min(8096, $offset - $this->pos));

            if ($result === '') {

                break;

            }

        }

    }

    /**

     * Reads from all of the appended streams until the length is met or EOF.

     *

     * {@inheritdoc}

     */

    public function read($length)

    {

        $buffer = '';

        $total = count($this->streams) - 1;

        $remaining = $length;

        $progressToNext = false;

        while ($remaining > 0) {

            // Progress to the next stream if needed.

            if ($progressToNext || $this->streams[$this->current]->eof()) {

                $progressToNext = false;

                if ($this->current === $total) {

                    break;

                }

                $this->current++;

            }

            $result = $this->streams[$this->current]->read($remaining);

            // Using a loose comparison here to match on '', false, and null

            if ($result == null) {

                $progressToNext = true;

                continue;

            }

            $buffer .= $result;

            $remaining = $length - strlen($buffer);

        }

        $this->pos += strlen($buffer);

        return $buffer;

    }

    public function isReadable()

    {

        return true;

    }

    public function isWritable()

    {

        return false;

    }

    public function isSeekable()

    {

        return $this->seekable;

    }

    public function write($string)

    {

        throw new \RuntimeException('Cannot write to an AppendStream');

    }

    public function getMetadata($key = null)

    {

        return $key ? null : [];

    }

}