export interface Pos {
    x: number
    y: number
}

export const NULL_POS: Pos = { x: 0, y: 0 }

/**
 * Returns position of a relative to b
 * @param a
 * @param b
 */
export function relativeTo(a: Pos, b: Pos): Pos {
    return { x: a.x - b.x, y: a.y - b.y }
}

/**
 * Returns the middle position of the given rectangle
 * @param rect
 */
export function middlePos(rect: DOMRect): Pos {
    return { x: rect.x + rect.width / 2, y: rect.y + rect.height / 2 }
}

/**
 * Returns x and y distance between given two pos
 * @param a
 * @param b
 */
export function size(a: Pos, b: Pos): Pos {
    return { x: Math.abs(a.x - b.x), y: Math.abs(a.y - b.y) }
}

export function add(a: Pos, b: Pos): Pos {
    return { x: a.x + b.x, y: a.y + b.y }
}

export function angle(a: Pos, b: Pos): number {
    const r = relativeTo(a, b)
    return Math.atan2(r.x, r.y)
}