import type { PropertyBag } from '../model/Properties';
import type { Project } from '../model/Project';
import { resolveTexture, type TextureRef } from '../model/texture';

export type SizeAxis = 'width' | 'height';

export interface PixelSize {
  w: number;
  h: number;
}

/**
 * Pixel size of the picture a sprite wears. Null while that
 * is not known: an upload still running has no measured size yet, and a ratio taken from 0 × 0
 * would be invented.
 */
export function texturePixelSize(project: Project, props: PropertyBag): PixelSize | null {
  const ref = resolveTexture(project, props);
  return ref ? pictureSize(ref) : null;
}

/** A frame's rectangle, else the whole image. */
export function pictureSize(ref: TextureRef): PixelSize | null {
  const w = ref.rect ? ref.rect.w : ref.sourceWidth;
  const h = ref.rect ? ref.rect.h : ref.sourceHeight;
  return w > 0 && h > 0 ? { w, h } : null;
}

/** A sprite wearing the texture at its own pixel size – or at the default size while that is unknown. */
export function spriteFromTexture(project: Project, textureId: string): PropertyBag {
  const props: PropertyBag = { texture: textureId };
  const size = texturePixelSize(project, props);
  return size ? { ...props, width: size.w, height: size.h } : props;
}

/**
 * What `axis` has to become for the sprite to carry the picture's proportions, leaving the
 * other side where it is. Null when the other side is not a usable number.
 */
export function fitAxisToAspect(size: PixelSize, props: PropertyBag, axis: SizeAxis): number | null {
  const other = Number(props[axis === 'width' ? 'height' : 'width']);
  if (!Number.isFinite(other) || other <= 0) return null;
  const fitted = axis === 'width' ? (other * size.w) / size.h : (other * size.h) / size.w;
  return Number.isFinite(fitted) && fitted > 0 ? fitted : null;
}

/**
 * Whether the sprite is drawn at the picture's own pixel size – one image pixel per world unit.
 * Exact, unlike `matchesAspect`: these two numbers are written as they are, with no division in
 * between that could cost a digit.
 */
export function matchesPixelSize(size: PixelSize, props: PropertyBag): boolean {
  return Number(props.width) === size.w && Number(props.height) === size.h;
}

/**
 * Cross product with a relative tolerance, because 3135 of the 40 000 sizes up to 200 × 200 fail an
 * exact test right after their own fit (rounding).
 */
export function matchesAspect(size: PixelSize, props: PropertyBag): boolean {
  const w = Number(props.width);
  const h = Number(props.height);
  if (!Number.isFinite(w) || !Number.isFinite(h) || w <= 0 || h <= 0) return false;
  return Math.abs(w * size.h - h * size.w) <= 1e-9 * w * size.h;
}