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

import {
  RawContextKey,
  IContextKeyService,
  IContextKey,
} from '../../../../vs/platform/contextkey/common/contextkey';
import { IDisposable } from '../../../../vs/base/common/lifecycle';
import { ICodeEditor } from '../../../../vs/editor/browser/editorBrowser';
import { EditorOption } from '../../../../vs/editor/common/config/editorOptions';

export class WordContextKey {
  static readonly AtEnd = new RawContextKey<boolean>('atEndOfWord', false);

  private readonly _ckAtEnd: IContextKey<boolean>;
  private readonly _configListener: IDisposable;

  private _enabled: boolean = false;
  private _selectionListener?: IDisposable;

  constructor(
    private readonly _editor: ICodeEditor,
    @IContextKeyService contextKeyService: IContextKeyService
  ) {
    this._ckAtEnd = WordContextKey.AtEnd.bindTo(contextKeyService);
    this._configListener = this._editor.onDidChangeConfiguration(
      (e) => e.hasChanged(EditorOption.tabCompletion) && this._update()
    );
    this._update();
  }

  dispose(): void {
    this._configListener.dispose();
    this._selectionListener?.dispose();
    this._ckAtEnd.reset();
  }

  private _update(): void {
    // only update this when tab completions are enabled
    const enabled = this._editor.getOption(EditorOption.tabCompletion) === 'on';
    if (this._enabled === enabled) {
      return;
    }
    this._enabled = enabled;

    if (this._enabled) {
      const checkForWordEnd = () => {
        if (!this._editor.hasModel()) {
          this._ckAtEnd.set(false);
          return;
        }
        const model = this._editor.getModel();
        const selection = this._editor.getSelection();
        const word = model.getWordAtPosition(selection.getStartPosition());
        if (!word) {
          this._ckAtEnd.set(false);
          return;
        }
        this._ckAtEnd.set(
          word.endColumn === selection.getStartPosition().column
        );
      };
      this._selectionListener =
        this._editor.onDidChangeCursorSelection(checkForWordEnd);
      checkForWordEnd();
    } else if (this._selectionListener) {
      this._ckAtEnd.reset();
      this._selectionListener.dispose();
      this._selectionListener = undefined;
    }
  }
}