export const sum = (a: number, b: number) => (a + b);

export const count = (previous: number, current: number) => (previous + (current ? 1 : 0));

export const polarToCartesian = (angle: number, radius: number) => {
    // This looks weird, but believe me it is right
    // 0 degrees refers to straight up in this case because of how d3 handles things
    // because the screen 0,0 position is top left we need to flip the y value
    return {
        x: radius * Math.sin(angle),
        y: - radius * Math.cos(angle)
    };
};

export const cartesianToPolar = (x: number, y: number) => {
    return {
        angle: Math.atan(y / x),
        radius: Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2))
    };
};

export const distance = (x0: number, y0: number, x1: number, y1: number) => {
    return Math.sqrt(Math.pow(x1 - x0, 2) + Math.pow(y1 - y0, 2));
};

export const unitVector = (x, y): number[]  => {
    const magnitude = distance(0, 0, x, y);

    return [x / magnitude, y / magnitude];
};

export const averagePoint = (points: number[][]): number[] => {
    let x = 0;
    let y = 0;

    points.forEach(point => {
        const [px, py] = point;
        x += px;
        y += py;
    });

    return [x / points.length, y / points.length];
}