mdast/lib/utilities.js

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/**
 * @author Titus Wormer
 * @copyright 2015 Titus Wormer
 * @license MIT
 * @module mdast:utilities
 * @version 2.2.2
 * @fileoverview Collection of tiny helpers useful for
 *   both parsing and compiling markdown.
 */

'use strict';

/* eslint-env commonjs */

/*
 * Dependencies.
 */

var collapseWhiteSpace = require('collapse-white-space');

/*
 * Expressions.
 */

var EXPRESSION_LINE_BREAKS = /\r\n|\r/g;
var EXPRESSION_SYMBOL_FOR_NEW_LINE = /\u2424/g;
var EXPRESSION_BOM = /^\ufeff/;

/**
 * Throw an exception with in its `message` `value`
 * and `name`.
 *
 * @param {*} value - Invalid value.
 * @param {string} name - Setting name.
 */
function raise(value, name) {
    throw new Error(
        'Invalid value `' + value + '` ' +
        'for setting `' + name + '`'
    );
}

/**
 * Validate a value to be boolean. Defaults to `def`.
 * Raises an exception with `context[name]` when not
 * a boolean.
 *
 * @example
 *   validateBoolean({foo: null}, 'foo', true) // true
 *   validateBoolean({foo: false}, 'foo', true) // false
 *   validateBoolean({foo: 'bar'}, 'foo', true) // Throws
 *
 * @throws {Error} - When a setting is neither omitted nor
 *   a boolean.
 * @param {Object} context - Settings.
 * @param {string} name - Setting name.
 * @param {boolean} def - Default value.
 */
function validateBoolean(context, name, def) {
    var value = context[name];

    if (value === null || value === undefined) {
        value = def;
    }

    if (typeof value !== 'boolean') {
        raise(value, 'options.' + name);
    }

    context[name] = value;
}

/**
 * Validate a value to be boolean. Defaults to `def`.
 * Raises an exception with `context[name]` when not
 * a boolean.
 *
 * @example
 *   validateNumber({foo: null}, 'foo', 1) // 1
 *   validateNumber({foo: 2}, 'foo', 1) // 2
 *   validateNumber({foo: 'bar'}, 'foo', 1) // Throws
 *
 * @throws {Error} - When a setting is neither omitted nor
 *   a number.
 * @param {Object} context - Settings.
 * @param {string} name - Setting name.
 * @param {number} def - Default value.
 */
function validateNumber(context, name, def) {
    var value = context[name];

    if (value === null || value === undefined) {
        value = def;
    }

    if (typeof value !== 'number' || value !== value) {
        raise(value, 'options.' + name);
    }

    context[name] = value;
}

/**
 * Validate a value to be in `map`. Defaults to `def`.
 * Raises an exception with `context[name]` when not
 * not in `map`.
 *
 * @example
 *   var map = {bar: true, baz: true};
 *   validateString({foo: null}, 'foo', 'bar', map) // 'bar'
 *   validateString({foo: 'baz'}, 'foo', 'bar', map) // 'baz'
 *   validateString({foo: true}, 'foo', 'bar', map) // Throws
 *
 * @throws {Error} - When a setting is neither omitted nor
 *   in `map`.
 * @param {Object} context - Settings.
 * @param {string} name - Setting name.
 * @param {string} def - Default value.
 * @param {Object} map - Enum.
 */
function validateString(context, name, def, map) {
    var value = context[name];

    if (value === null || value === undefined) {
        value = def;
    }

    if (!(value in map)) {
        raise(value, 'options.' + name);
    }

    context[name] = value;
}

/**
 * Clean a string in preperation of parsing.
 *
 * @example
 *   clean('\ufefffoo'); // 'foo'
 *   clean('foo\r\nbar'); // 'foo\nbar'
 *   clean('foo\u2424bar'); // 'foo\nbar'
 *
 * @param {string} value - Content to clean.
 * @return {string} - Cleaned content.
 */
function clean(value) {
    return String(value)
        .replace(EXPRESSION_BOM, '')
        .replace(EXPRESSION_LINE_BREAKS, '\n')
        .replace(EXPRESSION_SYMBOL_FOR_NEW_LINE, '\n');
}

/**
 * Normalize an identifier.  Collapses multiple white space
 * characters into a single space, and removes casing.
 *
 * @example
 *   normalizeIdentifier('FOO\t bar'); // 'foo bar'
 *
 * @param {string} value - Content to normalize.
 * @return {string} - Normalized content.
 */
function normalizeIdentifier(value) {
    return collapseWhiteSpace(value).toLowerCase();
}

/*
 * Expose `validate`.
 */

exports.validate = {
    'boolean': validateBoolean,
    'string': validateString,
    'number': validateNumber
};

/*
 * Expose.
 */

exports.normalizeIdentifier = normalizeIdentifier;
exports.clean = clean;
exports.raise = raise;