react-native-devtools-frontend/front_end/models/text_utils/TextCursor.ts

// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import * as Platform from '../../core/platform/platform.js';

export class TextCursor {
  private lineEndings: number[];
  private offsetInternal: number;
  private lineNumberInternal: number;
  private columnNumberInternal: number;

  constructor(lineEndings: number[]) {
    this.lineEndings = lineEndings;
    this.offsetInternal = 0;
    this.lineNumberInternal = 0;
    this.columnNumberInternal = 0;
  }

  advance(offset: number): void {
    this.offsetInternal = offset;
    while (this.lineNumberInternal < this.lineEndings.length &&
           this.lineEndings[this.lineNumberInternal] < this.offsetInternal) {
      ++this.lineNumberInternal;
    }
    this.columnNumberInternal = this.lineNumberInternal ?
        this.offsetInternal - this.lineEndings[this.lineNumberInternal - 1] - 1 :
        this.offsetInternal;
  }

  offset(): number {
    return this.offsetInternal;
  }

  resetTo(offset: number): void {
    this.offsetInternal = offset;
    this.lineNumberInternal =
        Platform.ArrayUtilities.lowerBound(this.lineEndings, offset, Platform.ArrayUtilities.DEFAULT_COMPARATOR);
    this.columnNumberInternal = this.lineNumberInternal ?
        this.offsetInternal - this.lineEndings[this.lineNumberInternal - 1] - 1 :
        this.offsetInternal;
  }

  lineNumber(): number {
    return this.lineNumberInternal;
  }

  columnNumber(): number {
    return this.columnNumberInternal;
  }
}