#! /usr/bin/env runjs

function long2tile(lon, zoom) {
    return (Math.floor((lon + 180) / 360 * Math.pow(2, zoom)));
}

function lat2tile(lat, zoom) {
    return (Math.floor((1 - Math.log(Math.tan(lat * Math.PI / 180) + 1 / Math.cos(lat * Math.PI / 180)) / Math.PI) / 2 * Math.pow(2, zoom)));
}

main = () => {
    if ($ARGS.length < 3) {
        println("Usage: mapdownload.js pattern true|false zoom [png|jpg]");
        println("                      |       |          |    |");
        println("                      +-------+----------+----+----------- URL Pattern");
        println("                              |          |    |");
        println("                              +----------+----+----------- Reverse Y (Gaode -> TMS should set true)");
        println("                                         |    |");
        println("                                         +----+----------- Zoom (0~20), 2_120,30~121,31");
        println("                                              |");
        println("                                              +----------- Image type");
        return;
    }

    var pattern = $ARGS[0];
    var reverseY = "true".equals($ARGS[1]);
    var z = $ARGS[2];
    var suffix = ($ARGS.length > 3) ? $ARGS[3] : 'png';

    if (z.indexOf('_') < 0) {
        var x_min = 0;
        var y_min = 0;
        var x_max = Math.pow(2, z) - 1;
        var y_max = Math.pow(2, z) - 1;
    } else {
        var _z = z;
        z = parseInt(_z.substring(0, _z.indexOf('_')));
        var lngLats = _z.substring(_z.indexOf('_') + 1).split('~');
        var lngLat1 = lngLats[0].split(',');
        var lngLat2 = lngLats[1].split(',');
        var x1 = long2tile(parseFloat(lngLat1[0]), z);
        var x2 = long2tile(parseFloat(lngLat2[0]), z);
        var y1 = lat2tile(parseFloat(lngLat1[1]), z);
        var y2 = lat2tile(parseFloat(lngLat2[1]), z);

        x_min = Math.min(x1, x2);
        x_max = Math.max(x1, x2);
        y_min = Math.min(y1, y2);
        y_max = Math.max(y1, y2);
    }

    println('X, min: ' + x_min + ', max: ' + x_max);
    println('Y, min: ' + y_min + ', max: ' + y_max);

    var count = 0;
    var total = (x_max - x_min + 1) * (y_max - y_min + 1);
    for (var x = x_min; x <= x_max; x++) {
        for (var y = y_min; y <= y_max; y++) {
            count++;
            var url = pattern;
            url = url.replace(/\{x\}/g, "" + x);
            url = url.replace(/\{y\}/g, "" + y);
            url = url.replace(/\{z\}/g, "" + z);

            var fiPath = $$.file("" + z, "" + x);
            fiPath.mkdirs();
            var fi = $$.file(fiPath, (reverseY ? (Math.pow(2, z) - 1 - y) : y) + "." + suffix);
            if (!fi.exists()) {
                println("Downloading: " + url + "  ==> " + fi + " (" + count + "/" + total + ")");
                var bs = $$.httpRequest().url(url).get().getBytes();
                $$.rFile(fi).write(bs);
            }
        }
    }
};

main();