Parses the contents of an input scad file looking for parameters that can be set dynamically

OpenSCADParameterParser.php

<?php

$paramters = [];

const CONSTRAINT_TYPE_MINMAX = "minmax";
const CONSTRAINT_TYPE_SET = "set";

function determineParameterConstraintType(array $constraint): string
{
    return count($constraint) == 1 ? CONSTRAINT_TYPE_MINMAX : CONSTRAINT_TYPE_SET;
}

// Change this to the name of input file
$handle = fopen("input.txt", "r");

if ($handle) {
    while (($line = fgets($handle)) !== false) {

        $r = preg_match_all(
            "@^(?:[ \t]+)?(?<name>[a-z_](?:[a-z_\d]+)?)(?:[ \t]+)?=(?:[ \t]+)?(?<value>[^;]+);(?:(?:[ \t]+)?\/\/(?:[ \t]+)?\[(?<constraint>[^\]]+))?@i",
            $line,
            $matches,
            PREG_SET_ORDER
        );

        // (guard) No matches
        if($r == 0 || $r == false) {
            $previousLine = $line;
            continue;
        }

        $parameter = [
            "name" => $matches[0]["name"],
            "value" => $matches[0]["value"],
            "constraint" => $matches[0]["constraint"] ?? null,
            "help" => null
        ];

        // Value will can be a number or a string but never anything else
        if(preg_match("@^[\"']([^\"']+)[\"']$@", $parameter["value"], $match)) {
            $parameter["value"] = $match[1];

        } elseif(is_numeric($parameter["value"])) {
            // Quick and dirty way to convert to number
            $parameter["value"] += 0; 

        // (guard) This line is not a defined value, instead, it is likely calculated
        } else {
            continue;
        }

        // Further parse the constraint if there is one
        if(null != $parameter["constraint"]) {

            $constraint = [
                "values" => explode(",", $parameter["constraint"]),
                "type" => null
            ];

            $constraint["values"] = array_map("trim", $constraint["values"]);

            // The possibilities here are either an array containing exactly 2 numbers (min/max) or 
            // an array of values that denotes a set of possible values
            $constraint["type"] = determineParameterConstraintType($constraint["values"]);

            if($constraint["type"] == CONSTRAINT_TYPE_MINMAX) {
                [$constraint["values"]["min"], $constraint["values"]["max"]] = array_map("floatval", explode(":", $constraint["values"][0]));
            } else {
                $values = array_map(function ($item) {
                    $bits = explode(":", $item);

                    $value = $bits[0];
                    $name = $bits[1] ?? $value;

                    return [
                        "value" => trim($value),
                        "name" => trim($name)
                    ];
                }, $constraint["values"]);

                $constraint["values"] = [];
                foreach($values as $item) {
                    $constraint["values"][$item["value"]] = $item["name"];
                }
            }

            $parameter["constraint"] = $constraint;
        }

        // See if the previous line has help text information
        $r = preg_match_all(
            "@^\/\/(?:[ \t]+)?-(?:[ \t]+)?(?<help>[^\r\n]+)@i",
            $previousLine,
            $matches,
            PREG_SET_ORDER
        );

        if($r !== false && $r > 0) {
            $parameter["help"] = $matches[0]["help"] ?? null;
        }

        $paramters[] = $parameter;

        $previousLine = $line;
    }
    fclose($handle);
} else {
    // error opening the file.
    throw new Exception("Unable to open source file input.txt");
} 

print json_encode($paramters, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES) . PHP_EOL;
exit;