| // Copyright 2015 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. |
| |
| /** |
| * Parser for a simple grammar that describes a tree structure using a function- |
| * like "a(b(c,d))" syntax. Original intended usage: to have browsertests |
| * specify an arbitrary tree of iframes, loaded from various sites, without |
| * having to write a .html page for each level or do crazy feats of data: url |
| * escaping. But there's nothing really iframe-specific here. See below for some |
| * examples of the grammar and the parser output. |
| * |
| * @example <caption>Basic syntax: an identifier followed by arg list.</caption> |
| * TreeParserUtil.parse('abc ()'); // returns { value: 'abc', children: [] } |
| * |
| * @example <caption>The arg list is optional. Dots are legal in ids.</caption> |
| * TreeParserUtil.parse('b.com'); // returns { value: 'b.com', children: [] } |
| * |
| * @example <caption>Commas separate children in the arg list.</caption> |
| * // returns { value: 'b', children: [ |
| * // { value: 'c', children: [] }, |
| * // { value: 'd', children: [] } |
| * // ]} |
| * TreeParserUtil.parse('b (c, d)'; |
| * |
| * @example <caption>Children can have children, and so on.</caption> |
| * // returns { value: 'e', children: [ |
| * // { value: 'f', children: [ |
| * // { value: 'g', children: [ |
| * // { value: 'h', children: [] }, |
| * // { value: 'i', children: [ |
| * // { value: 'j', children: [] } |
| * // ]}, |
| * // ]} |
| * // ]} |
| * // ]} |
| * TreeParserUtil.parse('e(f(g(h(),i(j))))'; |
| * |
| * @example <caption>flatten() converts a [sub]tree back to a string.</caption> |
| * var tree = TreeParserUtil.parse('b.com (c.com(e.com), d.com)'); |
| * TreeParserUtil.flatten(tree.children[0]); // returns 'c.com(e.com())' |
| */ |
| var TreeParserUtil = (function() { |
| 'use strict'; |
| |
| /** |
| * Parses an input string into a tree. See class comment for examples. |
| * @returns A tree of the form {value: <string>, children: <Array.<tree>>}. |
| */ |
| function parse(input) { |
| var tokenStream = lex(input); |
| |
| var result = takeIdAndChild(tokenStream); |
| if (tokenStream.length != 0) |
| throw new Error('Expected end of stream, but found "' + |
| tokenStream[0] + '".') |
| return result; |
| } |
| |
| /** |
| * Inverse of |parse|. Converts a parsed tree object into a string. Can be |
| * used to forward a subtree as an argument to a nested document. |
| */ |
| function flatten(tree) { |
| return tree.value + '(' + tree.children.map(flatten).join(',') + ')'; |
| } |
| |
| /** |
| * Lexer function to convert an input string into a token stream. Splits the |
| * input along whitespace, parens and commas. Whitespace is removed, while |
| * parens and commas are preserved as standalone tokens. |
| * |
| * @param {string} input The input string. |
| * @return {Array.<string>} The resulting token stream. |
| */ |
| function lex(input) { |
| return input.split(/(\s+|\(|\)|,)/).reduce( |
| function (resultArray, token) { |
| var trimmed = token.trim(); |
| if (trimmed) { |
| resultArray.push(trimmed); |
| } |
| return resultArray; |
| }, []); |
| } |
| |
| |
| /** |
| * Consumes from the stream an identifier and optional child list, returning |
| * its parsed representation. |
| */ |
| function takeIdAndChild(tokenStream) { |
| return { value: takeIdentifier(tokenStream), |
| children: takeChildList(tokenStream) }; |
| } |
| |
| /** |
| * Consumes from the stream an identifier, returning its value (as a string). |
| */ |
| function takeIdentifier(tokenStream) { |
| if (tokenStream.length == 0) |
| throw new Error('Expected an identifier, but found end-of-stream.'); |
| var token = tokenStream.shift(); |
| if (!token.match(/[a-zA-Z0-9.-]+/)) |
| throw new Error('Expected an identifier, but found "' + token + '".'); |
| return token; |
| } |
| |
| /** |
| * Consumes an optional child list from the token stream, returning a list of |
| * the parsed children. |
| */ |
| function takeChildList(tokenStream) { |
| // Remove the next token from the stream if it matches |token|. |
| function tryToEatA(token) { |
| if (tokenStream[0] == token) { |
| tokenStream.shift(); |
| return true; |
| } |
| return false; |
| } |
| |
| // Bare identifier case, as in 'b' in the input '(a (b, c))' |
| if (!tryToEatA('(')) |
| return []; |
| |
| // Empty list case, as in 'b' in the input 'a (b (), c)'. |
| if (tryToEatA(')')) { |
| return []; |
| } |
| |
| // List with at least one entry. |
| var result = [ takeIdAndChild(tokenStream) ]; |
| |
| // Additional entries allowed with commas. |
| while (tryToEatA(',')) { |
| result.push(takeIdAndChild(tokenStream)); |
| } |
| |
| // End of list. |
| if (tryToEatA(')')) { |
| return result; |
| } |
| if (tokenStream.length == 0) |
| throw new Error('Expected ")" or ",", but found end-of-stream.'); |
| throw new Error('Expected ")" or ",", but found "' + tokenStream[0] + '".'); |
| } |
| |
| return { |
| parse: parse, |
| flatten: flatten |
| }; |
| })(); |