import type {MjolnirEventRaw, HammerInput, Point} from '../types';

/* Constants */
const DOWN_EVENT = 1;
const MOVE_EVENT = 2;
const UP_EVENT = 4;
const MOUSE_EVENTS = {
  pointerdown: DOWN_EVENT,
  pointermove: MOVE_EVENT,
  pointerup: UP_EVENT,
  mousedown: DOWN_EVENT,
  mousemove: MOVE_EVENT,
  mouseup: UP_EVENT
};

// MouseEvent.button https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/button
const MOUSE_EVENT_BUTTON_LEFT = 0;
const MOUSE_EVENT_BUTTON_MIDDLE = 1;
const MOUSE_EVENT_BUTTON_RIGHT = 2;
// MouseEvent.buttons https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/buttons
const MOUSE_EVENT_BUTTONS_LEFT_MASK = 1;
const MOUSE_EVENT_BUTTONS_RIGHT_MASK = 2;
const MOUSE_EVENT_BUTTONS_MIDDLE_MASK = 4;

/**
 * Extract the involved mouse button
 */
export function whichButtons(event: MjolnirEventRaw): {
  leftButton: boolean;
  middleButton: boolean;
  rightButton: boolean;
} {
  const eventType = MOUSE_EVENTS[event.srcEvent.type];
  if (!eventType) {
    // Not a mouse evet
    return null;
  }

  const {buttons, button} = event.srcEvent as PointerEvent;
  let leftButton = false;
  let middleButton = false;
  let rightButton = false;

  if (eventType === MOVE_EVENT) {
    leftButton = Boolean(buttons & MOUSE_EVENT_BUTTONS_LEFT_MASK);
    middleButton = Boolean(buttons & MOUSE_EVENT_BUTTONS_MIDDLE_MASK);
    rightButton = Boolean(buttons & MOUSE_EVENT_BUTTONS_RIGHT_MASK);
  } else {
    leftButton = button === MOUSE_EVENT_BUTTON_LEFT;
    middleButton = button === MOUSE_EVENT_BUTTON_MIDDLE;
    rightButton = button === MOUSE_EVENT_BUTTON_RIGHT;
  }

  return {leftButton, middleButton, rightButton};
}

/**
 * Calculate event position relative to the root element
 */
export function getOffsetPosition(
  event: MjolnirEventRaw,
  rootElement: HTMLElement
): {
  center: Point;
  offsetCenter: Point;
} {
  const center = (event as HammerInput).center;

  // `center` is a hammer.js event property
  if (!center) {
    // Not a gestural event
    return null;
  }

  const rect = rootElement.getBoundingClientRect();

  // Fix scale for map affected by a CSS transform.
  // See https://stackoverflow.com/a/26893663/3528533
  const scaleX = rect.width / rootElement.offsetWidth || 1;
  const scaleY = rect.height / rootElement.offsetHeight || 1;

  // Calculate center relative to the root element
  const offsetCenter = {
    x: (center.x - rect.left - rootElement.clientLeft) / scaleX,
    y: (center.y - rect.top - rootElement.clientTop) / scaleY
  };

  return {center, offsetCenter};
}