import {addProjection,addCoordinateTransforms,Projection} from 'ol/proj';

var gcj02 = {};
var i=0;
var PI = Math.PI;
var AXIS = 6378245.0;
var OFFSET = 0.00669342162296594323;  // (a^2 - b^2) / a^2

var sphericalMercator = {}

var RADIUS = 6378137;
var MAX_LATITUDE = 85.0511287798;
var RAD_PER_DEG = Math.PI / 180;

var projzh = {};

function forEachPoint(func) {
    return function(input, opt_output, opt_dimension) {
        var len = input.length;
        var dimension = opt_dimension ? opt_dimension : 2;
        var output;
        if (opt_output) {
            output = opt_output;
        } else {
            if (dimension !== 2) {
                output = input.slice();
            } else {
                output = new Array(len);
            }
        }
        for (var offset = 0; offset < len; offset += dimension) {
            func(input, output, offset)
        }
        return output;
    };
};


function delta(wgLon, wgLat) {
    var dLat = transformLat(wgLon - 105.0, wgLat - 35.0);
    var dLon = transformLon(wgLon - 105.0, wgLat - 35.0);
    var radLat = wgLat / 180.0 * PI;
    var magic = Math.sin(radLat);
    magic = 1 - OFFSET * magic * magic;
    var sqrtMagic = Math.sqrt(magic);
    dLat = (dLat * 180.0) / ((AXIS * (1 - OFFSET)) / (magic * sqrtMagic) * PI);
    dLon = (dLon * 180.0) / (AXIS / sqrtMagic * Math.cos(radLat) * PI);
    return [dLon, dLat];
}

function outOfChina(lon, lat) {
    if (lon < 72.004 || lon > 137.8347) {
        return true;
    }
    if (lat < 0.8293 || lat > 55.8271) {
        return true;
    }
    return false;
}

function transformLat(x, y) {
    var ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x));
    ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0;
    ret += (20.0 * Math.sin(y * PI) + 40.0 * Math.sin(y / 3.0 * PI)) * 2.0 / 3.0;
    ret += (160.0 * Math.sin(y / 12.0 * PI) + 320 * Math.sin(y * PI / 30.0)) * 2.0 / 3.0;
    return ret;
}

function transformLon(x, y) {
    var ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x));
    ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0;
    ret += (20.0 * Math.sin(x * PI) + 40.0 * Math.sin(x / 3.0 * PI)) * 2.0 / 3.0;
    ret += (150.0 * Math.sin(x / 12.0 * PI) + 300.0 * Math.sin(x / 30.0 * PI)) * 2.0 / 3.0;
    return ret;
}

gcj02.toWGS84 = forEachPoint(
    function(input, output, offset) {
        var lng = input[offset];
        var lat = input[offset + 1];
        if (!outOfChina(lng, lat)) {
            var deltaD = delta(lng, lat);
            lng = lng - deltaD[0];
            lat = lat - deltaD[1];
        }
        output[offset] = lng;
        output[offset + 1] = lat;
    });

gcj02.fromWGS84 = forEachPoint(function(input, output, offset) {
    var lng = input[offset];
    var lat = input[offset + 1];
    if (!outOfChina(lng, lat)) {
        var deltaD = delta(lng, lat);
        lng = lng + deltaD[0];
        lat = lat + deltaD[1];
    }
    output[offset] = lng;
    output[offset + 1] = lat;
});

sphericalMercator.forward = forEachPoint(function(input, output, offset) {
    var lat = Math.max(Math.min(MAX_LATITUDE, input[offset + 1]), -MAX_LATITUDE);
    var sin = Math.sin(lat * RAD_PER_DEG);

    output[offset] = RADIUS * input[offset] * RAD_PER_DEG;
    output[offset + 1] = RADIUS * Math.log((1 + sin) / (1 - sin)) / 2;
});

sphericalMercator.inverse = forEachPoint(function(input, output, offset) {
    output[offset] = input[offset] / RADIUS / RAD_PER_DEG;
    output[offset + 1] = (2 * Math.atan(Math.exp(input[offset + 1] / RADIUS)) - (Math.PI / 2)) / RAD_PER_DEG;
});


projzh.ll2gmerc = function(input, opt_output, opt_dimension) {
    let output =gcj02.fromWGS84(input, opt_output, opt_dimension);
    return projzh.ll2smerc(output, output, opt_dimension);
};

projzh.gmerc2ll = function(input, opt_output, opt_dimension) {
    let output = projzh.smerc2ll(input, input, opt_dimension);
    return gcj02.toWGS84(output, opt_output, opt_dimension);
};

projzh.smerc2gmerc = function(input, opt_output, opt_dimension) {
    let output = projzh.smerc2ll(input, input, opt_dimension);
    output = gcj02.fromWGS84(output, output, opt_dimension);
    return projzh.ll2smerc(output, output, opt_dimension);
};

projzh.gmerc2smerc = function(input, opt_output, opt_dimension) {
    let output = projzh.smerc2ll(input, input, opt_dimension);
    output = gcj02.toWGS84(output, output, opt_dimension);
    return projzh.ll2smerc(output, output, opt_dimension);
};

projzh.ll2smerc = sphericalMercator.forward;
projzh.smerc2ll = sphericalMercator.inverse;

const gcj02Extent = [-20037508.342789244, -20037508.342789244, 20037508.342789244, 20037508.342789244];
const gcjMecator = new Projection({
    code: "GCJ-02",
    extent: gcj02Extent,
    units: "m"
});

addProjection(gcjMecator);
addCoordinateTransforms("EPSG:4326", gcjMecator, projzh.ll2gmerc, projzh.gmerc2ll);
addCoordinateTransforms("EPSG:3857", gcjMecator, projzh.smerc2gmerc, projzh.gmerc2smerc);

export default gcjMecator;