<?php
declare(strict_types = 1);

namespace Psalm\Internal\LanguageServer;

use Psalm\Internal\LanguageServer\Message;
use AdvancedJsonRpc\Message as MessageBody;
use Sabre\Event\{Loop, Emitter};

class ProtocolStreamReader extends Emitter implements ProtocolReader
{
    const PARSE_HEADERS = 1;
    const PARSE_BODY = 2;

    /** @var resource */
    private $input;

    /** @var int */
    private $parsingMode = self::PARSE_HEADERS;

    /** @var string */
    private $buffer = '';

    /** @var array<string, string> */
    private $headers = [];

    /** @var ?int */
    private $contentLength;

    /**
     * @param resource $input
     */
    public function __construct($input)
    {
        $this->input = $input;

        $this->on(
            'close',
            /** @return void */
            function () {
                Loop\removeReadStream($this->input);
            }
        );

        Loop\addReadStream(
            $this->input,
            /** @return void */
            function () {
                if (feof($this->input)) {
                    // If stream_select reported a status change for this stream,
                    // but the stream is EOF, it means it was closed.
                    $this->emit('close');
                    return;
                }
                while (($c = fgetc($this->input)) !== false && $c !== '') {
                    $this->buffer .= $c;
                    switch ($this->parsingMode) {
                        case self::PARSE_HEADERS:
                            if ($this->buffer === "\r\n") {
                                $this->parsingMode = self::PARSE_BODY;
                                $this->contentLength = (int)$this->headers['Content-Length'];
                                $this->buffer = '';
                            } elseif (substr($this->buffer, -2) === "\r\n") {
                                $parts = explode(':', $this->buffer);
                                $this->headers[$parts[0]] = trim($parts[1]);
                                $this->buffer = '';
                            }
                            break;
                        case self::PARSE_BODY:
                            if (strlen($this->buffer) === $this->contentLength) {
                                $msg = new Message(MessageBody::parse($this->buffer), $this->headers);
                                $this->emit('message', [$msg]);
                                $this->parsingMode = self::PARSE_HEADERS;
                                $this->headers = [];
                                $this->buffer = '';
                            }
                            break;
                    }
                }
            }
        );
    }
}