node/tools/eslint/node_modules/vfile-location/index.js

/**
 * @author Titus Wormer
 * @copyright 2016 Titus Wormer
 * @license MIT
 * @module vfile-location
 * @fileoverview Convert between positions (line and column-based)
 *   and offsets (range-based) locations in a virtual file.
 */

'use strict';

/* Expose. */
module.exports = factory;

/**
 * Factory.
 *
 * @param {VFile|string|Buffer} file - Virtual file or document.
 */
function factory(file) {
  var contents = indices(String(file));

  return {
    toPosition: offsetToPositionFactory(contents),
    toOffset: positionToOffsetFactory(contents)
  };
}

/**
 * Factory to get the line and column-based `position` for
 * `offset` in the bound indices.
 *
 * @param {Array.<number>} indices - Indices of
 *   line-breaks in `value`.
 * @return {Function} - Bound method.
 */
function offsetToPositionFactory(indices) {
  return offsetToPosition;

  /**
   * Get the line and column-based `position` for
   * `offset` in the bound indices.
   *
   * @param {number} offset - Offset.
   * @return {Position} - Object with `line`, `column`,
   *   and `offset` properties based on the bound
   *   `indices`.  An empty object when given invalid
   *   or out of bounds input.
   */
  function offsetToPosition(offset) {
    var index = -1;
    var length = indices.length;

    if (offset < 0) {
      return {};
    }

    while (++index < length) {
      if (indices[index] > offset) {
        return {
          line: index + 1,
          column: (offset - (indices[index - 1] || 0)) + 1,
          offset: offset
        };
      }
    }

    return {};
  }
}

/**
 * Factory to get the `offset` for a line and column-based
 * `position` in the bound indices.
 *
 * @param {Array.<number>} indices - Indices of
 *   line-breaks in `value`.
 * @return {Function} - Bound method.
 */
function positionToOffsetFactory(indices) {
  return positionToOffset;

  /**
   * Get the `offset` for a line and column-based
   * `position` in the bound indices.
   *
   * @param {Position} position - Object with `line` and
   *   `column` properties.
   * @return {number} - Offset. `-1` when given invalid
   *   or out of bounds input.
   */
  function positionToOffset(position) {
    var line = position && position.line;
    var column = position && position.column;

    if (!isNaN(line) && !isNaN(column) && line - 1 in indices) {
      return ((indices[line - 2] || 0) + column - 1) || 0;
    }

    return -1;
  }
}

/**
 * Get indices of line-breaks in `value`.
 *
 * @param {string} value - Value.
 * @return {Array.<number>} - List of indices of
 *   line-breaks.
 */
function indices(value) {
  var result = [];
  var index = value.indexOf('\n');

  while (index !== -1) {
    result.push(index + 1);
    index = value.indexOf('\n', index + 1);
  }

  result.push(value.length + 1);

  return result;
}