<?php

if (! function_exists('trim_zeros')) {
    /**
     * 移除数字字符串中的前导零和尾随零
     */
    function trim_zeros(string $var): string
    {
        if (! is_numeric($var)) {
            return $var;
        }

        $var = ltrim($var, '0');

        $pos = strpos($var, '.');
        if ($pos !== false) {
            if ($pos === 0) {
                $var = '0'.$var;
            }
            $var = rtrim(rtrim($var, '0'), '.');
        }

        return $var === '' ? '0' : $var;
    }
}

function transformLat($x, $y)
{
    $ret = -100.0 + 2.0 * $x + 3.0 * $y + 0.2 * $y * $y + 0.1 * $x * $y + 0.2 * sqrt(abs($x));
    $ret += (20.0 * sin(6.0 * $x * pi()) + 20.0 * sin(2.0 * $x * pi())) * 2.0 / 3.0;
    $ret += (20.0 * sin($y * pi()) + 40.0 * sin($y / 3.0 * pi())) * 2.0 / 3.0;
    $ret += (160.0 * sin($y / 12.0 * pi()) + 320 * sin($y * pi() / 30.0)) * 2.0 / 3.0;

    return $ret;
}

function transformLon($x, $y)
{
    $ret = 300.0 + $x + 2.0 * $y + 0.1 * $x * $x + 0.1 * $x * $y + 0.1 * sqrt(abs($x));
    $ret += (20.0 * sin(6.0 * $x * pi()) + 20.0 * sin(2.0 * $x * pi())) * 2.0 / 3.0;
    $ret += (20.0 * sin($x * pi()) + 40.0 * sin($x / 3.0 * pi())) * 2.0 / 3.0;
    $ret += (150.0 * sin($x / 12.0 * pi()) + 300.0 * sin($x / 30.0 * pi())) * 2.0 / 3.0;

    return $ret;
}

function delta($lat, $lon)
{
    $a = 6378245.0;
    $ee = 0.00669342162296594323;
    $dLat = transformLat($lon - 105.0, $lat - 35.0);
    $dLon = transformLon($lon - 105.0, $lat - 35.0);
    $radLat = $lat / 180.0 * pi();
    $magic = sin($radLat);
    $magic = 1 - $ee * $magic * $magic;
    $sqrtMagic = sqrt($magic);
    $dLat = ($dLat * 180.0) / (($a * (1 - $ee)) / ($magic * $sqrtMagic) * pi());
    $dLon = ($dLon * 180.0) / ($a / $sqrtMagic * cos($radLat) * pi());

    return ['lat' => $dLat, 'lon' => $dLon];
}