import { Assets, CanvasSource, Texture } from 'pixi.js';
import type { FrameRect, TextureRef } from '../core/model/texture';
import { type EdgeMode, SHEET_EDGE } from '../core/shader/nodes';
import { FileLibrary } from './FileLibrary';

/**
 * Pixi turns `clamp-to-edge` into `repeat` on every texture a Graphics fill draws with
 * (`generateTextureFillMatrix`), and a fill samples past the shape's edge – MSAA evaluates a partly
 * covered pixel at its centre. `mirror-repeat` is left alone and reads like clamp within a texel.
 */
const EDGE_MODE = 'mirror-repeat';

/**
 * A shader may want the picture to continue differently past its border (the Output's Edge). The
 * sampler state lives on the source – WebGL takes no style from the shader – so that is a cut of
 * its own with that address mode.
 */
const ADDRESS_MODE: Record<EdgeMode, 'repeat' | 'mirror-repeat' | 'clamp-to-edge'> = {
  mirror: EDGE_MODE,
  repeat: 'repeat',
  clamp: 'clamp-to-edge',
};

/** Keeps uploaded images on the GPU; callers never await and get a redraw when the picture lands. */
export class TextureLibrary extends FileLibrary<Texture> {
  private readonly loaded = new Map<string, Texture>();
  /** Frames cut from their sheets, keyed by file and rectangle; kept like the files. */
  private readonly crops = new Map<string, Texture>();

  constructor() {
    super('/game-maker/data/textures', 'textures');
  }

  /**
   * The picture if it is in memory, otherwise null while it loads. The scale mode belongs to the
   * shared source, so two assets naming the same file with different `smooth` fight over it and
   * the last one drawn wins; upload avoids that by reusing the existing asset for a known file.
   */
  get(ref: TextureRef, edge: EdgeMode = SHEET_EDGE): Texture | null {
    const sheet = this.load(ref.file);
    if (!sheet) return null;
    const rect = ref.rect ?? (edge === SHEET_EDGE ? null : wholeOf(sheet));
    const texture = rect ? this.crop(ref.file, sheet, rect, edge) : sheet;
    if (!texture) return null;
    const mode = ref.smooth ? 'linear' : 'nearest';
    if (texture.source.scaleMode !== mode) {
      texture.source.scaleMode = mode;
      // Pixi's `scaleMode` setter leaves the style's cached `_sharedResourceId` stale, so the old
      // GPU sampler keeps being used until a reload; `update()` drops the id.
      texture.source.style.update();
    }
    return texture;
  }

  /**
   * The picture if it is in memory, otherwise null while it loads – without touching the scale
   * mode, which belongs to whoever wears the texture. A thumbnail must not decide the filter of
   * a picture the scene is drawing with.
   */
  load(file: string): Texture | null {
    const texture = this.loaded.get(file);
    if (!texture) {
      this.startLoading(file);
      return null;
    }
    return texture;
  }

  /** The picture, or one of its cut frames, if in memory – without a load or a scale-mode change. */
  peek(file: string, rect: FrameRect | null = null): Texture | null {
    if (rect) return this.crops.get(cropKey(file, rect)) ?? null;
    return this.loaded.get(file) ?? null;
  }

  /**
   * A frame as a texture of its own, cut the first time it is asked for. Drawn from the sheet
   * through a fill matrix it showed a row of the neighbouring cell along any edge that fell
   * inside a screen pixel; a cut has no neighbour to show.
   */
  private crop(file: string, sheet: Texture, rect: FrameRect, edge: EdgeMode): Texture | null {
    if (rect.w <= 0 || rect.h <= 0) return null;
    const key = edge === SHEET_EDGE ? cropKey(file, rect) : `${cropKey(file, rect)}|${edge}`;
    let texture = this.crops.get(key);
    if (!texture) {
      const canvas = new OffscreenCanvas(rect.w, rect.h);
      const picture = sheet.source.resource as CanvasImageSource;
      canvas.getContext('2d')?.drawImage(picture, rect.x, rect.y, rect.w, rect.h, 0, 0, rect.w, rect.h);
      texture = new Texture({
        source: new CanvasSource({ resource: canvas, addressMode: ADDRESS_MODE[edge] }),
      });
      this.crops.set(key, texture);
    }
    return texture;
  }

  protected fetchFile(url: string): Promise<Texture> {
    return Assets.load<Texture>(url);
  }

  protected keep(file: string, texture: Texture): void {
    texture.source.style.addressMode = EDGE_MODE;
    texture.source.style.update();
    this.loaded.set(file, texture);
  }
}

function cropKey(file: string, rect: FrameRect): string {
  return `${file}|${rect.x},${rect.y},${rect.w},${rect.h}`;
}

function wholeOf(sheet: Texture): FrameRect {
  return { x: 0, y: 0, w: sheet.source.pixelWidth, h: sheet.source.pixelHeight };
}

export const textureLibrary = new TextureLibrary();