// import Turf from "turf";
let turf = require("turf");

module.exports = {
    gpsToMeters: function (lat1, lon1, lat2, lon2){  // generally used geo measurement function
        var R = 6378.137; // Radius of earth in KM
        var dLat = lat2 * Math.PI / 180 - lat1 * Math.PI / 180;
        var dLon = lon2 * Math.PI / 180 - lon1 * Math.PI / 180;
        var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
        Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
        Math.sin(dLon/2) * Math.sin(dLon/2);
        var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
        var d = R * c;
        return d * 1000; // meters
    },
    calculateArea: function (points) {
        var polygon = turf.polygon([[[125, -15], [113, -22], [154, -27], [144, -15], [125, -15]]]);
        var area = turf.area(polygon);
        console.log(area);
        var poly1 = turf.polygon([[
            [-82.574787, 35.594087],
            [-82.574787, 35.615581],
            [-82.545261, 35.615581],
            [-82.545261, 35.594087],
            [-82.574787, 35.594087]
        ]], {"fill": "#0f0"});
        var poly2 = turf.polygon([[
            [-82.560024, 35.585153],
            [-82.560024, 35.602602],
            [-82.52964, 35.602602],
            [-82.52964, 35.585153],
            [-82.560024, 35.585153]
        ]], {"fill": "#00f"});
        
        var union = turf.union(poly1, poly2);
        console.log(union.geometry.coordinates);
        var poly1 = turf.polygon([[
            [-122.801742, 45.48565],
            [-122.801742, 45.60491],
            [-122.584762, 45.60491],
            [-122.584762, 45.48565],
            [-122.801742, 45.48565]
          ]]);
          
          var poly2 = turf.polygon([[
            [-122.520217, 45.535693],
            [-122.64038, 45.553967],
            [-122.720031, 45.526554],
            [-122.669906, 45.507309],
            [-122.723464, 45.446643],
            [-122.532577, 45.408574],
            [-122.487258, 45.477466],
            [-122.520217, 45.535693]
          ]]);
          
          var intersection = turf.intersect(poly1, poly2);
          console.log(intersection);//null if no intersect
    }
}