<?php
// (a) helper function - server response
function verbose($ok = 1, $info = "")
{
    if ($ok == 0) {
        http_response_code(400);
    }
    exit(json_encode(["ok" => $ok, "info" => $info]));
}

// (b) invalid upload
if (empty($_FILES) || $_FILES["file"]["error"]) {
    verbose(0, "Failed to move uploaded file.");
}

// (c) upload destination - change folder if required!
$filePath = __DIR__ . DIRECTORY_SEPARATOR . "uploads";
/*if (!file_exists($filePath)) {
    if (!mkdir($filePath, 0777, true)) {
        verbose(0, "Failed to create $filePath");
    }
}*/
$fileName = isset($_REQUEST["name"])
    ? $_REQUEST["name"]
    : $_FILES["file"]["name"];
$filePath = $filePath . DIRECTORY_SEPARATOR . $fileName;

// (d) deal with chunks
$chunk = isset($_REQUEST["chunk"]) ? intval($_REQUEST["chunk"]) : 0;
$chunks = isset($_REQUEST["chunks"]) ? intval($_REQUEST["chunks"]) : 0;
$out = @fopen("{$filePath}.part", $chunk == 0 ? "wb" : "ab");
if ($out) {
    $in = @fopen($_FILES["file"]["tmp_name"], "rb");
    if ($in) {
        while ($buff = fread($in, 4096)) {
            fwrite($out, $buff);
        }
    } else {
        verbose(0, "Failed to open input stream");
    }
    @fclose($in);
    @fclose($out);
    @unlink($_FILES["file"]["tmp_name"]);
} else {
    verbose(0, "Failed to open output stream");
}

// (e) check if file has been uploaded
if (!$chunks || $chunk == $chunks - 1) {
    rename("{$filePath}.part", $filePath);
}
verbose(1, "Upload OK");
?>