<?php

namespace MongoDB\GridFS;

use Exception;

/**
 * Stream wrapper for reading and writing a GridFS file.
 *
 * @internal
 * @see Bucket::openUploadStream()
 * @see Bucket::openDownloadStream()
 */
class StreamWrapper
{
    /**
     * @var resource|null Stream context (set by PHP)
     */
    public $context;

    private $mode;
    private $protocol;
    private $stream;

    /**
     * Return the stream's file document.
     *
     * @return stdClass
     */
    public function getFile()
    {
        return $this->stream->getFile();
    }

    /**
     * Register the GridFS stream wrapper.
     *
     * @param string $protocol Protocol to use for stream_wrapper_register()
     */
    public static function register($protocol = 'gridfs')
    {
        if (in_array($protocol, stream_get_wrappers())) {
            stream_wrapper_unregister($protocol);
        }

        stream_wrapper_register($protocol, get_called_class(), \STREAM_IS_URL);
    }

    /**
     * Closes the stream.
     *
     * @see http://php.net/manual/en/streamwrapper.stream-close.php
     */
    public function stream_close()
    {
        $this->stream->close();
    }

    /**
     * Returns whether the file pointer is at the end of the stream.
     *
     * @see http://php.net/manual/en/streamwrapper.stream-eof.php
     * @return boolean
     */
    public function stream_eof()
    {
        if ( ! $this->stream instanceof ReadableStream) {
            return false;
        }

        return $this->stream->isEOF();
    }

    /**
     * Opens the stream.
     *
     * @see http://php.net/manual/en/streamwrapper.stream-open.php
     * @param string  $path       Path to the file resource
     * @param string  $mode       Mode used to open the file (only "r" and "w" are supported)
     * @param integer $options    Additional flags set by the streams API
     * @param string  $openedPath Not used
     */
    public function stream_open($path, $mode, $options, &$openedPath)
    {
        $this->initProtocol($path);
        $this->mode = $mode;

        if ($mode === 'r') {
            return $this->initReadableStream();
        }

        if ($mode === 'w') {
            return $this->initWritableStream();
        }

        return false;
    }

    /**
     * Read bytes from the stream.
     *
     * Note: this method may return a string smaller than the requested length
     * if data is not available to be read.
     * 
     * @see http://php.net/manual/en/streamwrapper.stream-read.php
     * @param integer $count Number of bytes to read
     * @return string
     */
    public function stream_read($count)
    {
        if ( ! $this->stream instanceof ReadableStream) {
            return '';
        }

        try {
            return $this->stream->downloadNumBytes($count);
        } catch (Exception $e) {
            trigger_error(sprintf('%s: %s', get_class($e), $e->getMessage()), \E_USER_WARNING);
            return false;
        }
    }

    /**
     * Return information about the stream.
     *
     * @see http://php.net/manual/en/streamwrapper.stream-stat.php
     * @return array
     */
    public function stream_stat()
    {
        $stat = $this->getStatTemplate();

        $stat[2] = $stat['mode'] = $this->mode;
        $stat[7] = $stat['size'] = $this->stream->getSize();

        return $stat;
    }

    /**
     * Write bytes to the stream.
     *
     * @see http://php.net/manual/en/streamwrapper.stream-write.php
     * @param string $data Data to write
     * @return integer The number of bytes written
     */
    public function stream_write($data)
    {
        if ( ! $this->stream instanceof WritableStream) {
            return 0;
        }

        try {
            return $this->stream->insertChunks($data);
        } catch (Exception $e) {
            trigger_error(sprintf('%s: %s', get_class($e), $e->getMessage()), \E_USER_WARNING);
            return false;
        }
    }

    /**
     * Returns a stat template with default values.
     *
     * @return array
     */
    private function getStatTemplate()
    {
        return [
            0  => 0,  'dev'     => 0,
            1  => 0,  'ino'     => 0,
            2  => 0,  'mode'    => 0,
            3  => 0,  'nlink'   => 0,
            4  => 0,  'uid'     => 0,
            5  => 0,  'gid'     => 0,
            6  => -1, 'rdev'    => -1,
            7  => 0,  'size'    => 0,
            8  => 0,  'atime'   => 0,
            9  => 0,  'mtime'   => 0,
            10 => 0,  'ctime'   => 0,
            11 => -1, 'blksize' => -1,
            12 => -1, 'blocks'  => -1,
        ];
    }

    /**
     * Initialize the protocol from the given path.
     *
     * @see StreamWrapper::stream_open()
     * @param string $path
     */
    private function initProtocol($path)
    {
        $parts = explode('://', $path, 2);
        $this->protocol = $parts[0] ?: 'gridfs';
    }

    /**
     * Initialize the internal stream for reading.
     *
     * @see StreamWrapper::stream_open()
     * @return boolean
     */
    private function initReadableStream()
    {
        $context = stream_context_get_options($this->context);

        $this->stream = new ReadableStream(
            $context[$this->protocol]['collectionWrapper'],
            $context[$this->protocol]['file']
        );

        return true;
    }

    /**
     * Initialize the internal stream for writing.
     *
     * @see StreamWrapper::stream_open()
     * @return boolean
     */
    private function initWritableStream()
    {
        $context = stream_context_get_options($this->context);

        $this->stream = new WritableStream(
            $context[$this->protocol]['collectionWrapper'],
            $context[$this->protocol]['filename'],
            $context[$this->protocol]['options']
        );

        return true;
    }
}
