/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

import { FastDomNode } from './fastDomNode';
import { TimeoutTimer } from '../../common/Async';
import { Disposable } from '../../common/Lifecycle';
import { ScrollbarVisibility } from './scrollable';

export class ScrollbarVisibilityController extends Disposable {
  private _visibility: ScrollbarVisibility;
  private _visibleClassName: string;
  private _invisibleClassName: string;
  private _domNode: FastDomNode<HTMLElement> | null;
  private _rawShouldBeVisible: boolean;
  private _shouldBeVisible: boolean;
  private _isNeeded: boolean;
  private _isVisible: boolean;
  private _revealTimer: TimeoutTimer;

  constructor(visibility: ScrollbarVisibility, visibleClassName: string, invisibleClassName: string) {
    super();
    this._visibility = visibility;
    this._visibleClassName = visibleClassName;
    this._invisibleClassName = invisibleClassName;
    this._domNode = null;
    this._isVisible = false;
    this._isNeeded = false;
    this._rawShouldBeVisible = false;
    this._shouldBeVisible = false;
    this._revealTimer = this._register(new TimeoutTimer());
  }

  public setVisibility(visibility: ScrollbarVisibility): void {
    if (this._visibility !== visibility) {
      this._visibility = visibility;
      this._updateShouldBeVisible();
    }
  }

  public setShouldBeVisible(rawShouldBeVisible: boolean): void {
    this._rawShouldBeVisible = rawShouldBeVisible;
    this._updateShouldBeVisible();
  }

  private _applyVisibilitySetting(): boolean {
    if (this._visibility === ScrollbarVisibility.HIDDEN) {
      return false;
    }
    if (this._visibility === ScrollbarVisibility.VISIBLE) {
      return true;
    }
    return this._rawShouldBeVisible;
  }

  private _updateShouldBeVisible(): void {
    const shouldBeVisible = this._applyVisibilitySetting();

    if (this._shouldBeVisible !== shouldBeVisible) {
      this._shouldBeVisible = shouldBeVisible;
      this.ensureVisibility();
    }
  }

  public setIsNeeded(isNeeded: boolean): void {
    if (this._isNeeded !== isNeeded) {
      this._isNeeded = isNeeded;
      this.ensureVisibility();
    }
  }

  public setDomNode(domNode: FastDomNode<HTMLElement>): void {
    this._domNode = domNode;
    this._domNode.setClassName(this._invisibleClassName);

    this.setShouldBeVisible(false);
  }

  public ensureVisibility(): void {

    if (!this._isNeeded) {
      this._hide(false);
      return;
    }

    if (this._shouldBeVisible) {
      this._reveal();
    } else {
      this._hide(true);
    }
  }

  private _reveal(): void {
    if (this._isVisible) {
      return;
    }
    this._isVisible = true;

    this._revealTimer.setIfNotSet(() => {
      this._domNode?.setClassName(this._visibleClassName);
    }, 0);
  }

  private _hide(withFadeAway: boolean): void {
    this._revealTimer.cancel();
    if (!this._isVisible) {
      return;
    }
    this._isVisible = false;
    this._domNode?.setClassName(this._invisibleClassName + (withFadeAway ? ' xterm-fade' : ''));
  }
}