continents.ts

function whichContinent(latitude: number, longitude: number) : string {
    const point = [longitude, latitude];
    for (const cont in continents) {
	if (inPolygon(point, pathToList(continents[cont]))) {
	    return cont;
	}
    }
    return "unknown";
}

// Adapted from https://stackoverflow.com/questions/13905646/get-the-continent-given-the-latitude-and-longitude
// Rough shape of continents.
const continents : any = {
    "northamerica" : { latitude: [90, 90, 78.13, 57.5, 15, 15, 1.25, 1.25, 51, 60, 60, 51, 51, 60], longitude: [-168.75, -10, -10, -37.5, -30, -75, -82.5, -105, -180, -180, -168.75, 166.6, 180, 180] },
    "asia" : { latitude: [90, 42.5, 42.5, 40.79, 41, 40.55, 40.4, 40.05, 39.17, 35.46, 33, 31.74, 29.54, 27.78, 11.3, 12.5, -60, -60, -31.88, -11.88, -10.27, 33.13, 51, 60, 90, 90, 90, 60, 60], longitude: [77.5, 48.8, 30, 28.81, 29, 27.31, 26.75, 26.36, 25.19, 27.91, 27.5, 34.58, 34.92, 34.46, 44.3, 52, 75, 110, 110, 110, 140, 140, 166.6, 180, 180, -180, -168.75, -168.75, -180] },
    "europe" : { latitude: [90, 90, 42.5, 42.5, 40.79, 41, 40.55, 40.40, 40.05, 39.17, 35.46, 33, 38, 35.42, 28.25, 15, 57.5, 78.13],longitude: [-10, 77.5, 48.8, 30, 28.81, 29, 27.31, 26.75, 26.36, 25.19, 27.91, 27.5, 10, -10, -13, -30, -37.5, -10] },
    "australia" : { latitude: [-11.88, -10.27, -10, -30, -52.5, -31.88], longitude: [110, 140, 145, 161.25, 142.5,  110] },
    "southamerica" : { latitude: [1.25, 1.25, 15, 15, -60, -60], longitude: [-105, -82.5, -75, -30, -30, -105] },
    "africa" : { latitude: [15,  28.25, 35.42, 38, 33, 31.74, 29.54, 27.78, 11.3, 12.5, -60, -60], longitude: [-30, -13,   -10, 10, 27.5, 34.58, 34.92, 34.46, 44.3, 52,    75, -30] },
    //    "asia2" : { latitude: [90, 90, 60, 60], longitude: [-180, -168.75, -168.75, -180] },
    //    "northAmerica2" : { latitude: [51, 51, 60], longitude: [166.6, 180, 180] },
    "antarctica" : { latitude: [-60, -60, -90, -90],longitude: [-180, 180, 180, -180] }
};

function inPolygon(point : Array<number>, vs : Array<Array<number>>) {
    // ray-casting algorithm based on
    // https://wrf.ecse.rpi.edu/Research/Short_Notes/pnpoly.html/pnpoly.html
    let x = point[0], y = point[1];
    
    let inside = false;
    for (let i = 0, j = vs.length - 1; i < vs.length; j = i++) {
        let xi = vs[i][0], yi = vs[i][1];
        let xj = vs[j][0], yj = vs[j][1];
        
        let intersect = ((yi > y) != (yj > y))
            && (x < (xj - xi) * (y - yi) / (yj - yi) + xi);
        if (intersect) inside = !inside;
    }
    
    return inside;
}

function pathToList(path : any) {
    let l = [];
    for (let i = 0; i < path["longitude"].length; i++) {
	l.push([path["longitude"][i], path["latitude"][i]]);
    }
    return l;
}