stockfish.php

Stockfish rest API

<?php

class Stockfish
{
    private $process;
    private $pipes;

    public function __construct(
        $binary = "/usr/bin/stockfish",
        $threads = 4,
        $hash = 512
    ) {
        $this->process = proc_open(
            $binary,
            [
                0 => ["pipe", "r"],
                1 => ["pipe", "w"],
                2 => ["pipe", "w"],
            ],
            $this->pipes
        );

        if (!is_resource($this->process)) {
            throw new Exception("Unable to start Stockfish.");
        }

        stream_set_blocking($this->pipes[1], true);

        $this->command("uci");
        $this->waitFor("uciok");

        $this->command("setoption name Threads value " . max(1, (int)$threads));
        $this->command("setoption name Hash value " . max(1, (int)$hash));
        //$this->command("setoption name MultiPV value 3");

        $this->command("isready");
        $this->waitFor("readyok");
    }

    private function command(string $cmd): void
    {
        fwrite($this->pipes[0], $cmd . PHP_EOL);
    }

    private function waitFor(string $needle): void
    {
        while (($line = fgets($this->pipes[1])) !== false) {
            if (strpos($line, $needle) !== false) {
                return;
            }
        }
    }

    public function analyze(string $fen, ?int $depth = 18, ?int $movetime = null): array
    {
        $this->command("ucinewgame");
        $this->command("isready");
        $this->waitFor("readyok");

        $this->command("position fen " . $fen);

        if ($movetime !== null) {
            $this->command("go movetime " . $movetime);
        } else {
            $this->command("go depth " . $depth);
        }

$result = [
    "info" => [],
    "depth" => null,
    "seldepth" => null,
    "time" => null,
    "nodes" => null,
    "nps" => null,
    "score" => null,
    "score_type" => null,
    "pv" => []
];

while (($line = fgets($this->pipes[1])) !== false) {

    $line = trim($line);

    if (strpos($line, "info") === 0) {

        $result["info"][] = $line;

        preg_match('/depth\s+(\d+)/', $line, $m);
        if (isset($m[1])) $result["depth"] = (int)$m[1];

        preg_match('/seldepth\s+(\d+)/', $line, $m);
        if (isset($m[1])) $result["seldepth"] = (int)$m[1];

        preg_match('/time\s+(\d+)/', $line, $m);
        if (isset($m[1])) $result["time"] = (int)$m[1];

        preg_match('/nodes\s+(\d+)/', $line, $m);
        if (isset($m[1])) $result["nodes"] = (int)$m[1];

        preg_match('/nps\s+(\d+)/', $line, $m);
        if (isset($m[1])) $result["nps"] = (int)$m[1];

        if (preg_match('/score\s+(cp|mate)\s+(-?\d+)/', $line, $m)) {
            $result["score_type"] = $m[1];
            $result["score"] = (int)$m[2];
        }

        if (preg_match('/ pv (.+)$/', $line, $m)) {
            $result["pv"] = explode(' ', trim($m[1]));
        }
    }

    if (strpos($line, "bestmove") === 0) {

        $parts = preg_split('/\s+/', $line);

        $result["bestmove"] = $parts[1] ?? null;
        $result["ponder"]   = $parts[3] ?? null;

        break;
    }
}

        return $result;
    }

    public function __destruct()
    {
        if (is_resource($this->process)) {
            $this->command("quit");
            proc_close($this->process);
        }
    }
}

/* ---------------------- */

function jsonResponse($data, int $status = 200)
{
    http_response_code($status);
    header("Content-Type: application/json");
    echo json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);
    exit;
}

function getRequest(): array
{
    $data = [];

    if ($_SERVER["REQUEST_METHOD"] === "POST") {
        $raw = file_get_contents("php://input");
        $json = json_decode($raw, true);

        if (is_array($json)) {
            $data = $json;
        }
    }

    return array_merge($_GET, $data);
}

function sanitizeFen(string $fen): string
{
    $fen = trim($fen);

    if (strlen($fen) > 128) {
        throw new Exception("FEN too long.");
    }

    if (preg_match('/[\r\n\x00]/', $fen)) {
        throw new Exception("Invalid characters in FEN.");
    }

    // Basic FEN character whitelist
    if (!preg_match('/^[prnbqkPRNBQK1-8\/wb\-\sKQkqa-h0-9]+$/', $fen)) {
        throw new Exception("Invalid FEN.");
    }

    return $fen;
}

/* ---------------------- */

try {

    $request = getRequest();

    if (empty($request["fen"])) {
        jsonResponse([
            "error" => "Missing 'fen'"
        ], 400);
    }

    $fen = sanitizeFen($request["fen"]);

    $depth = isset($request["depth"])
        ? max(1, min(99, (int)$request["depth"]))
        : null;

    $movetime = isset($request["movetime"])
        ? max(1, min(600000, (int)$request["movetime"]))
        : null;

    if ($depth === null && $movetime === null) {
        $depth = 15;
    }

    // movetime takes priority
    if ($movetime !== null) {
        $depth = null;
    }

    $sf = new Stockfish();

    $result = $sf->analyze(
        $fen,
        $depth,
        $movetime
    );

    jsonResponse($result);

} catch (Throwable $e) {

    jsonResponse([
        "error" => $e->getMessage()
    ], 500);

}