<?php

namespace App\Data;

/** The parser of the room text files (a port of common/roomtext.cpp, parse only). */
final class RoomText
{
    /**
     * @param string[] $error error message out-param (single element)
     */
    public static function parse(string $text, ?array &$error = null): ?RoomDef
    {
        $out = new RoomDef();
        $nmap = 0;
        $nrec = 0;
        $haveRoom = false;
        $section = '';
        $lineNo = 0;
        foreach (preg_split('/\r?\n/', $text) as $line) {
            $lineNo++;
            $cut = strpos($line, ';');
            if ($cut !== false) {
                $line = substr($line, 0, $cut);
            }
            $toks = preg_split('/\s+/', trim($line), -1, PREG_SPLIT_NO_EMPTY);
            if ($toks === false || $toks === []) {
                continue;
            }
            if (count($toks) === 2 && $toks[0] === 'room') {
                $out->number = (int)$toks[1];
                $haveRoom = true;
                continue;
            }
            if (count($toks) === 1 && ($toks[0] === 'map' || $toks[0] === 'record')) {
                $section = $toks[0];
                continue;
            }
            if (count($toks) === 1 && $toks[0] === 'end') {
                $section = '';
                continue;
            }
            if ($section === '') {
                $error = ["line $lineNo: unexpected text outside map/record"];
                return null;
            }
            foreach ($toks as $t) {
                if ($section === 'record' && substr($t, -1) === ':') {
                    continue;
                }
                if ($section === 'map') {
                    if ($t === '..' || $t === '--') {
                        $v = 0;
                    } elseif (strlen($t) === 2 && ctype_xdigit($t)) {
                        $v = (int)hexdec($t);
                    } else {
                        $error = ["line $lineNo: bad tile '$t' (use two hex digits or '..')"];
                        return null;
                    }
                    if ($nmap >= 720) {
                        $error = ['map has more than 720 tiles'];
                        return null;
                    }
                    if ($v === 0xFF) {
                        $error = ['tile id FF is reserved (end marker of the original format)'];
                        return null;
                    }
                    $out->map[$nmap++] = $v;
                } else {
                    if (strlen($t) !== 2 || !ctype_xdigit($t)) {
                        $error = ["line $lineNo: bad byte '$t'"];
                        return null;
                    }
                    if ($nrec >= 64) {
                        $error = ['record has more than 64 bytes'];
                        return null;
                    }
                    $out->rec[$nrec++] = (int)hexdec($t);
                }
            }
        }
        if (!$haveRoom) {
            $error = ["missing 'room N' line"];
            return null;
        }
        if ($nmap !== 720) {
            $error = ["map must have 40 x 18 = 720 tiles, found $nmap"];
            return null;
        }
        if ($nrec !== 64) {
            $error = ["record must have 64 bytes, found $nrec"];
            return null;
        }
        return $out;
    }
}