class AbstractPipes

abstract class AbstractPipes implements PipesInterface {
    public array $pipes = [];
    private string $inputBuffer = '';
    
    /** @var resource|string|\Iterator */
    private $input;
    private bool $blocked = true;
    private ?string $lastError = null;
    
    /**
     * @param resource|string|\Iterator $input
     */
    public function __construct($input) {
        if (\is_resource($input) || $input instanceof \Iterator) {
            $this->input = $input;
        }
        else {
            $this->inputBuffer = (string) $input;
        }
    }
    public function close() : void {
        foreach ($this->pipes as $pipe) {
            if (\is_resource($pipe)) {
                fclose($pipe);
            }
        }
        $this->pipes = [];
    }
    
    /**
     * Returns true if a system call has been interrupted.
     */
    protected function hasSystemCallBeenInterrupted() : bool {
        $lastError = $this->lastError;
        $this->lastError = null;
        // stream_select returns false when the `select` system call is interrupted by an incoming signal
        return null !== $lastError && false !== stripos($lastError, 'interrupted system call');
    }
    
    /**
     * Unblocks streams.
     */
    protected function unblock() : void {
        if (!$this->blocked) {
            return;
        }
        foreach ($this->pipes as $pipe) {
            stream_set_blocking($pipe, 0);
        }
        if (\is_resource($this->input)) {
            stream_set_blocking($this->input, 0);
        }
        $this->blocked = false;
    }
    
    /**
     * Writes input to stdin.
     *
     * @throws InvalidArgumentException When an input iterator yields a non supported value
     */
    protected function write() : ?array {
        if (!isset($this->pipes[0])) {
            return null;
        }
        $input = $this->input;
        if ($input instanceof \Iterator) {
            if (!$input->valid()) {
                $input = null;
            }
            elseif (\is_resource($input = $input->current())) {
                stream_set_blocking($input, 0);
            }
            elseif (!isset($this->inputBuffer[0])) {
                if (!\is_string($input)) {
                    if (!\is_scalar($input)) {
                        throw new InvalidArgumentException(\sprintf('"%s" yielded a value of type "%s", but only scalars and stream resources are supported.', get_debug_type($this->input), get_debug_type($input)));
                    }
                    $input = (string) $input;
                }
                $this->inputBuffer = $input;
                $this->input
                    ->next();
                $input = null;
            }
            else {
                $input = null;
            }
        }
        $r = $e = [];
        $w = [
            $this->pipes[0],
        ];
        // let's have a look if something changed in streams
        if (false === @stream_select($r, $w, $e, 0, 0)) {
            return null;
        }
        foreach ($w as $stdin) {
            if (isset($this->inputBuffer[0])) {
                $written = fwrite($stdin, $this->inputBuffer);
                $this->inputBuffer = substr($this->inputBuffer, $written);
                if (isset($this->inputBuffer[0])) {
                    return [
                        $this->pipes[0],
                    ];
                }
            }
            if ($input) {
                while (true) {
                    $data = fread($input, self::CHUNK_SIZE);
                    if (!isset($data[0])) {
                        break;
                    }
                    $written = fwrite($stdin, $data);
                    $data = substr($data, $written);
                    if (isset($data[0])) {
                        $this->inputBuffer = $data;
                        return [
                            $this->pipes[0],
                        ];
                    }
                }
                if (feof($input)) {
                    if ($this->input instanceof \Iterator) {
                        $this->input
                            ->next();
                    }
                    else {
                        $this->input = null;
                    }
                }
            }
        }
        // no input to read on resource, buffer is empty
        if (!isset($this->inputBuffer[0]) && !($this->input instanceof \Iterator ? $this->input
            ->valid() : $this->input)) {
            $this->input = null;
            fclose($this->pipes[0]);
            unset($this->pipes[0]);
        }
        elseif (!$w) {
            return [
                $this->pipes[0],
            ];
        }
        return null;
    }
    
    /**
     * @internal
     */
    public function handleError(int $type, string $msg) : void {
        $this->lastError = $msg;
    }

}