import type { Asset } from '../core/model/Asset';
import { findAsset } from '../core/model/Project';
import { Button, Label, Spacer, VStack, type Widget } from '../ui';
import type { EditorState } from './state';
import { TabHeader } from './TabHeader';

/**
 * The canvas each tab wraps: the header's Fit button and the tab's own plumbing need this much.
 * A canvas without `fit` belongs to a tab whose Fit frames something else (see `AssetTabEditor.fit`).
 * `saveView`/`restoreView` carry zoom and scroll across a switch to another document and back.
 */
export interface TabCanvas {
  readonly currentAssetId: string;
  show(assetId: string): void;
  fit?(): void;
  saveView?(): unknown;
  restoreView?(view: unknown): void;
}

export interface AssetTabOptions {
  /** Width reserved for the right-hand readout; a stack measures the label once, while empty. */
  infoWidth: number;
}

/**
 * The Behavior, State machine, Texture, Container … tabs. One editor per kind serves every open
 * document of that kind (#171): the tab row tells it which one to show, and it keeps each one's
 * view for when it comes back. A subclass must call `mount()`: header and canvas depend on each
 * other, so the base cannot build them.
 */
export abstract class AssetTabEditor<
  A extends Asset,
  C extends TabCanvas & Widget = TabCanvas & Widget,
> extends VStack {
  readonly fitButton: Button;
  protected readonly info: Label;
  /** Assigned by `mount`. Public because the check hooks and the play loop reach for it. */
  canvas!: C;
  private readonly views = new Map<string, unknown>();

  constructor(
    protected readonly state: EditorState,
    options: AssetTabOptions,
  ) {
    super();
    this.fitButton = new Button('Fit', { onClick: () => this.fit() });
    this.info = new Label('', { style: 'small', align: 'right' });
    this.info.minWidth = options.infoWidth;
  }

  /** Builds the header (with `strip` below it) around `canvas` and wires the state events. */
  protected mount(canvas: C, extras: readonly Widget[] = [], strip?: Widget): void {
    this.canvas = canvas;
    const header = new TabHeader();
    for (const widget of extras) header.add(widget);
    header.add(this.fitButton);
    header.add(new Spacer(), 1);
    header.add(this.info);

    this.add(header);
    if (strip) this.add(strip);
    this.add(this.body(canvas), 1);

    this.state.on('project', () => this.refresh());
    this.state.on('load', () => {
      this.views.clear();
      this.canvas.show('');
      this.refresh();
    });
    this.refresh();
  }

  /** The asset currently shown, `''` for none – the check scripts read this. */
  get currentAssetId(): string {
    return this.canvas.currentAssetId;
  }

  /** The right-hand readout as shown – the check scripts read this. */
  get shownInfo(): string {
    return this.info.text;
  }

  /** Shows a document, with the view it had when it was last on screen. */
  showAsset(assetId: string): void {
    const from = this.canvas.currentAssetId;
    if (from !== assetId) {
      if (from) this.views.set(from, this.saveView());
      this.canvas.show(assetId);
      const view = this.views.get(assetId);
      if (view !== undefined) this.restoreView(view);
    }
    this.refresh();
  }

  /** A closed tab: opened again, the document starts from a fitted view. What it played stops. */
  forgetView(assetId: string): void {
    this.views.delete(assetId);
    this.closed(assetId);
  }

  /** Stops what the tab plays of that asset; a tab that plays nothing has nothing to stop. */
  protected closed(_assetId: string): void {}

  /** The selection's id for this kind of asset, `''` when the selection is about something else. */
  abstract selectedId(): string;

  abstract isMine(asset: Asset): asset is A;

  /** The right-hand readout; `null` is the empty state. */
  protected abstract infoText(asset: A | null): string;

  /** What fills the tab below the header. Override to put something beside the canvas. */
  protected body(canvas: C): Widget {
    return canvas;
  }

  /** What the header's Fit button frames. Override when the tab has more than one view. */
  protected fit(): void {
    this.canvas.fit?.();
  }

  /** The view to come back to; override when the tab has more than one. */
  protected saveView(): unknown {
    return this.canvas.saveView?.();
  }

  protected restoreView(view: unknown): void {
    this.canvas.restoreView?.(view);
  }

  /** The canvas's area on screen, without the header – so a check can ask what lies outside it. */
  canvasRect(): { x: number; y: number; w: number; h: number } {
    const p = this.canvas.getGlobalPosition();
    return { x: p.x, y: p.y, w: this.canvas.w, h: this.canvas.h };
  }

  /** Enable/disable whatever `extras` the subclass passed to `mount`. */
  protected syncExtras(_asset: A | null): void {}

  protected asset(): A | null {
    const asset = findAsset(this.state.project, this.canvas.currentAssetId);
    return asset && this.isMine(asset) ? asset : null;
  }

  protected refresh(): void {
    const asset = this.asset();
    this.info.setText(asset ? this.infoText(asset) : '');
    this.syncExtras(asset);
  }
}