<?php

namespace Psr\Http\Message;

use RuntimeException;

/**
 * Describes a data stream.
 *
 * Typically, an instance will wrap a PHP stream; this interface provides
 * a wrapper around the most common operations, including serialization of
 * the entire stream to a string.
 */
interface StreamInterface {
	/**
	 * Reads all data from the stream into a string, from the beginning to end.
	 *
	 * This method MUST attempt to seek to the beginning of the stream before
	 * reading data and read the stream until the end is reached.
	 *
	 * Warning: This could attempt to load a large amount of data into memory.
	 *
	 * This method MUST NOT raise an exception in order to conform with PHP's
	 * string casting operations.
	 *
	 * @see http://php.net/manual/en/language.oop5.magic.php#object.tostring
	 * @return string
	 */
	public function __toString();

	/**
	 * Closes the stream and any underlying resources.
	 *
	 * @return void
	 */
	public function close();

	/**
	 * Separates any underlying resources from the stream.
	 *
	 * After the stream has been detached, the stream is in an unusable state.
	 *
	 * @return resource|null Underlying PHP stream, if any
	 */
	public function detach();

	/**
	 * Get the size of the stream if known.
	 *
	 * @return int|null Returns the size in bytes if known, or null if unknown.
	 */
	public function getSize();

	/**
	 * Returns the current position of the file read/write pointer
	 *
	 * @return int Position of the file pointer
	 * @throws RuntimeException on error.
	 */
	public function tell();

	/**
	 * Returns true if the stream is at the end of the stream.
	 *
	 * @return bool
	 */
	public function eof();

	/**
	 * Returns whether or not the stream is seekable.
	 *
	 * @return bool
	 */
	public function isSeekable();

	/**
	 * Seek to a position in the stream.
	 *
	 * @link http://www.php.net/manual/en/function.fseek.php
	 *
	 * @param int $offset Stream offset
	 * @param int $whence Specifies how the cursor position will be calculated
	 *     based on the seek offset. Valid values are identical to the built-in
	 *     PHP $whence values for `fseek()`.  SEEK_SET: Set position equal to
	 *     offset bytes SEEK_CUR: Set position to current location plus offset
	 *     SEEK_END: Set position to end-of-stream plus offset.
	 *
	 * @throws RuntimeException on failure.
	 */
	public function seek( $offset, $whence = SEEK_SET );

	/**
	 * Seek to the beginning of the stream.
	 *
	 * If the stream is not seekable, this method will raise an exception;
	 * otherwise, it will perform a seek(0).
	 *
	 * @throws RuntimeException on failure.
	 * @link http://www.php.net/manual/en/function.fseek.php
	 * @see seek()
	 */
	public function rewind();

	/**
	 * Returns whether or not the stream is writable.
	 *
	 * @return bool
	 */
	public function isWritable();

	/**
	 * Write data to the stream.
	 *
	 * @param string $string The string that is to be written.
	 *
	 * @return int Returns the number of bytes written to the stream.
	 * @throws RuntimeException on failure.
	 */
	public function write( $string );

	/**
	 * Returns whether or not the stream is readable.
	 *
	 * @return bool
	 */
	public function isReadable();

	/**
	 * Read data from the stream.
	 *
	 * @param int $length Read up to $length bytes from the object and return
	 *     them. Fewer than $length bytes may be returned if underlying stream
	 *     call returns fewer bytes.
	 *
	 * @return string Returns the data read from the stream, or an empty string
	 *     if no bytes are available.
	 * @throws RuntimeException if an error occurs.
	 */
	public function read( $length );

	/**
	 * Returns the remaining contents in a string
	 *
	 * @return string
	 * @throws RuntimeException if unable to read or an error occurs while
	 *     reading.
	 */
	public function getContents();

	/**
	 * Get stream metadata as an associative array or retrieve a specific key.
	 *
	 * The keys returned are identical to the keys returned from PHP's
	 * stream_get_meta_data() function.
	 *
	 * @link http://php.net/manual/en/function.stream-get-meta-data.php
	 *
	 * @param string $key Specific metadata to retrieve.
	 *
	 * @return array|mixed|null Returns an associative array if no key is
	 *     provided. Returns a specific key value if a key is provided and the
	 *     value is found, or null if the key is not found.
	 */
	public function getMetadata( $key = null );
}
