<?php
/**
 * Convert a ArcGis web recordset polygon to a geojson polygon feature.
 *
 * Validate the generated JSON with http://geojsonlint.com/
 *
 * Dependency installation:
 * $ composer require php-coord/php-coord
 *
 * @author Christan Weiske <cweiske@cweiske.de>
 */
require_once __DIR__ . '/vendor/autoload.php';

function err($msg)
{
    echo $msg . "\n";
    exit(1);
}

if ($argc < 2) {
    err("convert.php <esriGeoMetryFile.json>");
}

$file = $argv[1];
$data = json_decode(file_get_contents($file));

if (!isset($data->RecordSet->geometryType)
    || $data->RecordSet->geometryType != 'esriGeometryPolygon'
) {
    err('No esriGeometryPolygon');
}

$sRefs = [
    25833 => ['N', 33]
];
$sRef = $data->RecordSet->spatialReference->wkid;
if (!isset($sRefs[$sRef])) {
    err('Unknown spatial reference EPSG ' . $sRef);
}
list($latZone, $lngZone) = $sRefs[$sRef];

$geoJson = [
    'type'       => 'Feature',
    'title'      => basename($file, '.json'),
    'properties' => null,
    'geometry'   => [
        'type'        => 'Polygon',
        'coordinates' => [],
    ],
];
foreach ($data->RecordSet->features as $feature) {
    foreach ($feature->geometry->rings as $ring) {
        $coords = [];
        foreach ($ring as $point) {
            $utm = new \PHPCoord\UTMRef(
                $point[0], $point[1], 0, $latZone, $lngZone
            );
            $ll = $utm->toLatLng();
            $coords[] = [$ll->getLng(), $ll->getLat()];
        }

        $geoJson['geometry']['coordinates'][] = $coords;
    }
}

echo json_encode($geoJson, JSON_PRETTY_PRINT) . "\n";
?>