import type { ScreenRect } from "./types";

export type ScreenPoint = { x: number; y: number };

/** Returns corners in northwest, northeast, southwest, southeast order. */
export function rotatedRectCorners(rect: ScreenRect, rotation: number): [ScreenPoint, ScreenPoint, ScreenPoint, ScreenPoint] {
  if (!Number.isFinite(rotation)) rotation = 0;
  const center = { x: rect.x + rect.w / 2, y: rect.y + rect.h / 2 };
  const cosine = Math.cos(rotation);
  const sine = Math.sin(rotation);
  const rotate = (point: ScreenPoint): ScreenPoint => {
    const x = point.x - center.x;
    const y = point.y - center.y;
    return { x: center.x + x * cosine - y * sine, y: center.y + x * sine + y * cosine };
  };
  return [
    rotate({ x: rect.x, y: rect.y }),
    rotate({ x: rect.x + rect.w, y: rect.y }),
    rotate({ x: rect.x, y: rect.y + rect.h }),
    rotate({ x: rect.x + rect.w, y: rect.y + rect.h }),
  ];
}

/** Axis-aligned screen bounds used to constrain WebGL scissoring around a rotated quad. */
export function rotatedRectBounds(rect: ScreenRect, rotation: number): ScreenRect {
  if (rotation === 0) return rect;
  const points = rotatedRectCorners(rect, rotation);
  const xs = points.map((point) => point.x);
  const ys = points.map((point) => point.y);
  const x = Math.min(...xs);
  const y = Math.min(...ys);
  return { x, y, w: Math.max(...xs) - x, h: Math.max(...ys) - y };
}