export type TouchPoint = {
  clientX: number;
  clientY: number;
};

export type TouchDecisionState = {
  x: number;
  y: number;
  decided: boolean;
};

type TouchLike = {
  clientX: number;
  clientY: number;
};

type TouchEventLike = {
  touches: ArrayLike<TouchLike>;
  changedTouches: ArrayLike<TouchLike>;
};

export function getTouchPoint(event: TouchEventLike): TouchPoint {
  const touch = event.touches[0] ?? event.changedTouches[0];
  return {
    clientX: touch?.clientX ?? 0,
    clientY: touch?.clientY ?? 0,
  };
}

export function resolveTouchDragDecision(
  state: TouchDecisionState,
  point: TouchPoint,
  thresholdPx = 8,
): { nextState: TouchDecisionState; shouldHandleDrag: boolean } {
  if (state.decided) {
    return { nextState: state, shouldHandleDrag: true };
  }

  const dx = Math.abs(point.clientX - state.x);
  const dy = Math.abs(point.clientY - state.y);
  if (dx <= thresholdPx && dy <= thresholdPx) {
    return { nextState: state, shouldHandleDrag: false };
  }

  const nextState = { ...state, decided: true };
  return {
    nextState,
    shouldHandleDrag: dx >= dy,
  };
}