<?php
use Psr\Http\Message\StreamInterface;

include_once "StreamInterface.php";

class StringBuffer implements StreamInterface {
    private string $buf;
    private int $cur = 0;

    function __construct(string $buf)
    {
        $this->buf = $buf;
    }
    /**
     * 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(): string {
        return $this->buf;
    }

    public function close(): void {}

    public function detach(){
        $this->buf = "";
    }

    /**
     * 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(): int{
        return strlen($this->buf);
    }

    public function tell(): int {
        return $this->cur;
    }

    public function eof(): bool{
        return $this->cur > strlen($this->buf);
    }

    public function isSeekable(): bool {
        return true;
    }

    /**
     * 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(int $offset, int $whence = SEEK_SET): void {
        switch ($whence){
        case SEEK_SET:
                $this->cur = $offset;
                break;
        case SEEK_CUR:
                $this->cur += $offset;
                break;
        case SEEK_END:
                $this->cur = $this->getSize()+ $offset;
                break;
        }
    }

    /**
     * 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).
     *
     * @see seek()
     * @link http://www.php.net/manual/en/function.fseek.php
     * @throws \RuntimeException on failure.
     */
    public function rewind(): void {
        $this->cur = 0;
    }

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

    /**
     * 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 $str): int {
        $strlen = strlen($str);
        str_pad($this->buf, $this->cur + $strlen);
        substr_replace($this->buf, $str, $this->cur);
        return $strlen;
    }

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

    /**
     * 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(int $length): string {
        $remaining = $this->getSize() - $this->cur;
        if( $remaining <= 0 ) {
            return "";
        }
        return substr($this->buf, $this->cur,min($remaining, $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(): string {
        return $this->read($this->getSize() - $this->cur);
    }

    /**
     * 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|null $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(?string $key = null){
        return null;
    }

}

?>