<?php
// geojson.php — Baca file JSON & konversi koordinat UTM Zone 49S → WGS84
header('Content-Type: application/json; charset=utf-8');
header('Access-Control-Allow-Origin: *');
error_reporting(0);

// ── Hanya file ini yang diizinkan ──
$allowed = ['Populasi_Kecamatan.json'];

$file = $_GET['file'] ?? '';
if (!in_array($file, $allowed)) {
    http_response_code(400);
    echo json_encode(['error' => 'File tidak diizinkan: ' . $file]);
    exit;
}

$path = __DIR__ . '/' . $file;
if (!file_exists($path)) {
    http_response_code(404);
    echo json_encode(['error' => 'File tidak ditemukan: ' . $file]);
    exit;
}

ini_set('max_execution_time', 120);
ini_set('memory_limit', '256M');

$raw = file_get_contents($path);
$gj  = json_decode($raw, true);
if (!$gj) {
    http_response_code(500);
    echo json_encode(['error' => 'JSON tidak valid atau file rusak']);
    exit;
}

// ─────────────────────────────────────────────────────
//  KONVERSI UTM Zone 49S → WGS84 (lat/lng)
//  Dipakai untuk koordinat Pontianak (Northing ~9.99 juta)
// ─────────────────────────────────────────────────────
function utmToLatLng($easting, $northing, $zone = 49, $isSouth = true) {
    $a  = 6378137.0;
    $e2 = 0.00669437999014;
    $k0 = 0.9996;

    $x = $easting - 500000.0;
    $y = $isSouth ? $northing - 10000000.0 : $northing;

    $lon0 = deg2rad(($zone - 1) * 6 - 180 + 3);
    $e1   = (1 - sqrt(1 - $e2)) / (1 + sqrt(1 - $e2));
    $M    = $y / $k0;
    $mu   = $M / ($a * (1 - $e2/4 - 3*$e2*$e2/64 - 5*$e2*$e2*$e2/256));

    $phi1 = $mu
        + (3*$e1/2 - 27*pow($e1,3)/32)          * sin(2*$mu)
        + (21*$e1*$e1/16 - 55*pow($e1,4)/32)    * sin(4*$mu)
        + (151*pow($e1,3)/96)                    * sin(6*$mu)
        + (1097*pow($e1,4)/512)                  * sin(8*$mu);

    $N1 = $a / sqrt(1 - $e2 * pow(sin($phi1), 2));
    $T1 = pow(tan($phi1), 2);
    $C1 = $e2 / (1 - $e2) * pow(cos($phi1), 2);
    $R1 = $a * (1 - $e2) / pow(1 - $e2 * pow(sin($phi1), 2), 1.5);
    $D  = $x / ($N1 * $k0);

    $lat = $phi1 - ($N1 * tan($phi1) / $R1) * (
        $D*$D/2
        - (5 + 3*$T1 + 10*$C1 - 4*$C1*$C1 - 9*$e2/(1-$e2)) * pow($D,4)/24
        + (61 + 90*$T1 + 298*$C1 + 45*$T1*$T1 - 252*$e2/(1-$e2) - 3*$C1*$C1) * pow($D,6)/720
    );

    $lon = $lon0 + (
        $D
        - (1 + 2*$T1 + $C1) * pow($D,3)/6
        + (5 - 2*$C1 + 28*$T1 - 3*$C1*$C1 + 8*$e2/(1-$e2) + 24*$T1*$T1) * pow($D,5)/120
    ) / cos($phi1);

    return [round(rad2deg($lon), 8), round(rad2deg($lat), 8)];
}

// ─────────────────────────────────────────────────────
//  Deteksi apakah koordinat perlu dikonversi
//  Koordinat UTM Pontianak: Easting ~300000-400000, Northing ~9900000+
//  Koordinat WGS84: lng ~109, lat ~-0.1
// ─────────────────────────────────────────────────────
function isUTM($x, $y) {
    return (abs($x) > 1000 || abs($y) > 1000);
}

function convertCoords($coords) {
    if (!is_array($coords)) return $coords;

    // Koordinat tunggal [x, y]
    if (count($coords) >= 2 && is_numeric($coords[0]) && is_numeric($coords[1])) {
        $x = (float)$coords[0];
        $y = (float)$coords[1];
        if (isUTM($x, $y)) {
            return utmToLatLng($x, $y);
        }
        return [$x, $y]; // Sudah WGS84, biarkan
    }

    // Array of array → rekursif
    $result = [];
    foreach ($coords as $item) {
        if (!is_array($item)) continue;
        $result[] = convertCoords($item);
    }
    return $result;
}

// Proses semua fitur
if (isset($gj['features']) && is_array($gj['features'])) {
    foreach ($gj['features'] as &$feat) {
        if (isset($feat['geometry']['coordinates']) && is_array($feat['geometry']['coordinates'])) {
            $feat['geometry']['coordinates'] = convertCoords($feat['geometry']['coordinates']);
        }
    }
    unset($feat);
}

echo json_encode($gj);