import type { PropertyBag, Vec2 } from '../core/model/Properties';
import { cameraFrame, rectAround, type WorldRect } from '../core/properties/camera';

/**
 * The world point (`x`, `y`) sits at the centre of the screen rectangle `rect` (viewport-local
 * pixels) at `scale` pixels per world unit.
 */
export interface View {
  x: number;
  y: number;
  scale: number;
  rect: { x: number; y: number; w: number; h: number };
}

/** Free-panning view: the whole viewport is the rectangle. */
export function freeView(x: number, y: number, zoom: number, w: number, h: number): View {
  return { x, y, scale: zoom, rect: { x: 0, y: 0, w, h } };
}

/** The camera's frame fitted into `w`×`h` and centred; the remaining margin is letterbox. */
export function cameraView(camera: { x: number; y: number; props: PropertyBag }, w: number, h: number): View {
  const frame = cameraFrame(camera.props);
  const scale = Math.min(w / frame.w, h / frame.h);
  const fw = frame.w * scale;
  const fh = frame.h * scale;
  return { x: camera.x, y: camera.y, scale, rect: { x: (w - fw) / 2, y: (h - fh) / 2, w: fw, h: fh } };
}

export function screenToWorld(view: View, sx: number, sy: number): Vec2 {
  const cx = view.rect.x + view.rect.w / 2;
  const cy = view.rect.y + view.rect.h / 2;
  return { x: (sx - cx) / view.scale + view.x, y: (sy - cy) / view.scale + view.y };
}

export function worldToScreen(view: View, wx: number, wy: number): Vec2 {
  const cx = view.rect.x + view.rect.w / 2;
  const cy = view.rect.y + view.rect.h / 2;
  return { x: (wx - view.x) * view.scale + cx, y: (wy - view.y) * view.scale + cy };
}

export function worldBounds(view: View): WorldRect {
  return rectAround(view.x, view.y, view.rect.w / view.scale, view.rect.h / view.scale);
}

/** Whether a viewport-local point lies on the drawn rectangle rather than in the letterbox. */
export function isInside(view: View, sx: number, sy: number): boolean {
  const { x, y, w, h } = view.rect;
  return sx >= x && sx <= x + w && sy >= y && sy <= y + h;
}