593 lines
19 KiB
JavaScript
593 lines
19 KiB
JavaScript
// Basic parser and formatter for very simple text markup. Mostly targeted at
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// mobile use cases similar to Telegram and WhatsApp.
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//
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// Supports:
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// *abc* -> <b>abc</b>
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// _abc_ -> <i>abc</i>
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// ~abc~ -> <del>abc</del>
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// `abc` -> <tt>abc</tt>
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// Nested frmatting is supported, e.g. *abc _def_* -> <b>abc <i>def</i></b>
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//
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// URLs, @mentions, and #hashtags are extracted and converted into links.
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//
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// JSON data representation is inspired by Draft.js raw formatting.
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/*
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Text:
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this is *bold*, `code` and _italic_, ~strike~
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combined *bold and _italic_*
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an url: https://www.example.com/abc#fragment and another _www.tinode.co_
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this is a @mention and a #hashtag in a string
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second #hashtag
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Sample JSON representation of the text above:
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{
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"txt": "this is bold, code and italic, strike combined bold and italic an url: https://www.example.com/abc#fragment " +
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"and another www.tinode.co this is a @mention and a #hashtag in a string second #hashtag",
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"fmt": [
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{ "at":8, "len":4,"tp":"ST" },{ "at":14, "len":4, "tp":"CO" },{ "at":23, "len":6, "tp":"EM"},
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{ "at":31, "len":6, "tp":"DL" },{ "tp":"BR", "len":1, "at":37 },{ "at":56, "len":6, "tp":"EM" },
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{ "at":47, "len":15, "tp":"ST" },{ "tp":"BR", "len":1, "at":62 },{ "at":120, "len":13, "tp":"EM" },
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{ "at":71, "len":36, "key":0 },{ "at":120, "len":13, "key":1 },{ "tp":"BR", "len":1, "at":133 },
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{ "at":144, "len":8, "key":2 },{ "at":159, "len":8, "key":3 },{ "tp":"BR", "len":1, "at":179 },
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{ "at":187, "len":8, "key":3 },{ "tp":"BR", "len":1, "at":195 }
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],
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"ent": [
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{ "tp":"LN", "data":{ "url":"https://www.example.com/abc#fragment" } },
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{ "tp":"LN", "data":{ "url":"http://www.tinode.co" } },
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{ "tp":"MN", "data":{ "val":"mention" } },
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{ "tp":"HT", "data":{ "val":"hashtag" } }
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]
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}
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*/
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(function(environment) { // closure for web browsers
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'use strict';
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// Regular expressions for parsing inline formats. Javascript does not support lookbehind,
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// so it's a bit messy.
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var INLINE_STYLES = [
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// Strong = bold, *bold text*
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{name: "ST", start: /(?:^|\W)(\*)[^\s*]/, end: /[^\s*](\*)(?=$|\W)/},
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// Emphesized = italic, _italic text_
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{name: "EM", start: /(?:^|[\W_])(_)[^\s_]/, end: /[^\s_](_)(?=$|[\W_])/},
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// Deleted, ~strike this though~
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{name: "DL", start: /(?:^|\W)(~)[^\s~]/, end: /[^\s~](~)(?=$|\W)/},
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// Code block `this is monospace`
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{name: "CO", start: /(?:^|\W)(`)[^`]/, end: /[^`](`)(?=$|\W)/}
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];
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// RegExps for entity extraction (RF = reference)
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var ENTITY_TYPES = [
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// URLs
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{name: "LN", dataName: "url",
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pack: function(val) {
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// Check if the protocol is specified, if not use http
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if (!/^[a-z]+:\/\//i.test(val)) {
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val = 'http://' + val;
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}
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return {url: val};
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},
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re: /(https?:\/\/)?(?:www\.)?[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,4}\b(?:[-a-zA-Z0-9@:%_\+.~#?&//=]*)/g},
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// Mentions @user (must be 2 or more characters)
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{name: "MN", dataName: "val",
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pack: function(val) { return {val: val.slice(1)}; },
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re: /\B@(\w\w+)/g},
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// Hashtags #hashtag
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{name: "HT", dataName: "val",
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pack: function(val) { return {val: val.slice(1)}; },
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re: /\B#(\w\w+)/g}
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];
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// HTML tag name suggestions
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var HTML_TAGS = {
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ST: { name: 'b', isVoid: false },
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EM: { name: 'i', isVoid: false },
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DL: { name: 'del', isVoid: false },
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CO: { name: 'tt', isVoid: false },
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BR: { name: 'br', isVoid: true },
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LN: { name: 'a', isVoid: false },
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MN: { name: 'a', isVoid: false },
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HT: { name: 'a', isVoid: false }
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};
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// Helpers for converting Drafty to HTML.
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var DECORATORS = {
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ST: { open: function() { return '<b>'; }, close: function() { return '</b>'; }},
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EM: { open: function() { return '<i>'; }, close: function() { return '</i>'}},
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DL: { open: function() { return '<del>'; }, close: function() { return '</del>'}},
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CO: { open: function() { return '<tt>'; }, close: function() { return '</tt>'}},
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BR: { open: function() { return ''; }, close: function() { return '<br/>'}},
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LN: {
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open: function(data) { return '<a href="' + data.url + '">'; },
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close: function(data) { return '</a>'; },
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props: function(data) { return { href: data.url, target: "_blank" }; },
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},
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MN: {
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open: function(data) { return '<a href="#' + data.val + '">'; },
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close: function(data) { return '</a>'; },
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props: function(data) { return { name: data.val }; },
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},
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HT: {
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open: function(data) { return '<a href="#' + data.val + '">'; },
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close: function(data) { return '</a>'; },
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props: function(data) { return { name: data.val }; },
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}
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};
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var Drafty = (function() {
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// Take a string and defined earlier style spans, re-compose them into a tree where each leaf is
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// a same-style (including unstyled) string. I.e. 'hello *bold _italic_* and ~more~ world' ->
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// ('hello ', (b: 'bold ', (i: 'italic')), ' and ', (s: 'more'), ' world');
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//
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// This is needed in order to clear markup, i.e. 'hello *world*' -> 'hello world' and convert
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// ranges from markup-ed offsets to plain text offsets.
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function chunkify(line, start, end, spans) {
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var chunks = [];
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if (spans.length == 0) {
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return [];
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}
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for (var i in spans) {
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// Get the next chunk from the queue
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var span = spans[i];
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// Grab the initial unstyled chunk
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if (span.start > start) {
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chunks.push({text: line.slice(start, span.start)});
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}
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// Grab the styled chunk. It may include subchunks.
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var chunk = {type: span.type};
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var chld = chunkify(line, span.start + 1, span.end - 1, span.children);
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if (chld.length > 0) {
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chunk.children = chld;
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} else {
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chunk.text = span.text;
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}
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chunks.push(chunk);
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start = span.end + 1; // '+1' is to skip the formatting character
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}
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// Grab the remaining unstyled chunk, after the last span
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if (start < end) {
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chunks.push({text: line.slice(start, end)});
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}
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return chunks;
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}
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// Same as chunkify but used for formatting.
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function forEach(line, start, end, spans, formatter, context) {
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// Add un-styled range before the styled span starts.
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// Process ranges calling formatter for each range.
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var result = [];
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for (var i = 0; i < spans.length; i++) {
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var span = spans[i];
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// Add un-styled range before the styled span starts.
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if (start < span.at) {
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result.push(formatter.call(context, null, undefined, line.slice(start, span.at)));
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start = span.at;
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}
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// Get all spans which are within current span.
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var subspans = [];
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for (var si = i + 1; si < spans.length && spans[si].at < span.at + span.len; si++) {
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subspans.push(spans[si]);
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i = si;
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}
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var tag = HTML_TAGS[span.tp] || {};
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result.push(formatter.call(context, span.tp, span.data,
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tag.isVoid ? null : forEach(line, start, span.at + span.len, subspans, formatter, context)));
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start = span.at + span.len;
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}
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// Add the last unformatted range.
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if (start < end) {
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result.push(formatter.call(context, null, undefined, line.slice(start, end)));
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}
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return result;
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}
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// Detect starts and ends of formatting spans. Unformatted spans are
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// ignored at this stage.
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function spannify(original, re_start, re_end, type) {
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var result = [];
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var index = 0;
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var line = original.slice(0); // make a copy;
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while (line.length > 0) {
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// match[0]; // match, like '*abc*'
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// match[1]; // match captured in parenthesis, like 'abc'
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// match['index']; // offset where the match started.
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// Find the opening token.
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var start = re_start.exec(line);
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if (start == null) {
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break;
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}
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// Because javascript RegExp does not support lookbehind, the actual offset may not point
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// at the markup character. Find it in the matched string.
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var start_offset = start['index'] + start[0].lastIndexOf(start[1]);
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// Clip the processed part of the string.
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line = line.slice(start_offset + 1);
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// start_offset is an offset within the clipped string. Convert to original index.
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start_offset += index;
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// Index now point to the beginning of 'line' within the 'original' string.
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index = start_offset + 1;
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// Find the matching closing token.
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var end = re_end ? re_end.exec(line) : null;
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if (end == null) {
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break;
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}
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var end_offset = end['index'] + end[0].indexOf(end[1]);
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// Clip the processed part of the string.
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line = line.slice(end_offset + 1);
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// Update offsets
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end_offset += index;
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// Index now point to the beginning of 'line' within the 'original' string.
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index = end_offset + 1;
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result.push({
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text: original.slice(start_offset+1, end_offset),
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children: [],
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start: start_offset,
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end: end_offset,
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type: type
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});
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}
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return result;
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}
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// Convert linear array or spans into a tree representation.
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// Keep standalone and nested spans, throw away partially overlapping spans.
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function toTree(spans) {
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if (spans.length == 0) {
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return [];
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}
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var tree = [spans[0]];
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var last = spans[0];
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for (var i = 1; i < spans.length; i++) {
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// Keep spans which start after the end of the previous span or those which
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// are complete within the previous span.
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if (spans[i].start > last.end) {
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// Span is completely outside of the previous span.
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tree.push(spans[i]);
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last = spans[i];
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} else if (spans[i].end < last.end) {
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// Span is fully inside of the previous span. Push to subnode.
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last.children.push(spans[i]);
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}
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// Span could partially overlap, ignoring it as invalid.
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}
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// Recursively rearrange the subnodes.
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for (var i in tree) {
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tree[i].children = toTree(tree[i].children);
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}
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return tree;
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}
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// Get a list of entities from a text.
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function extractEntities(line) {
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var match;
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var extracted = [];
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ENTITY_TYPES.map(function(entity) {
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while ((match = entity.re.exec(line)) !== null) {
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extracted.push({
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offset: match['index'],
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len: match[0].length,
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unique: match[0],
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data: entity.pack(match[0]),
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type: entity.name});
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}
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});
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if (extracted.length == 0) {
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return extracted;
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}
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// Remove entities detected inside other entities, like #hashtag in a URL.
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extracted.sort(function(a,b) {
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return a.offset - b.offset;
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});
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var idx = -1;
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extracted = extracted.filter(function(el) {
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var result = (el.offset > idx);
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idx = el.offset + el.len;
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return result;
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});
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return extracted;
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}
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// Convert the chunks into format suitable for serialization.
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function draftify(chunks, startAt) {
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var plain = "";
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var ranges = [];
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for (var i in chunks) {
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var chunk = chunks[i];
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if (!chunk.text) {
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var drafty = draftify(chunk.children, plain.length + startAt);
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chunk.text = drafty.txt;
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ranges = ranges.concat(drafty.fmt);
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}
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if (chunk.type) {
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ranges.push({at: plain.length + startAt, len: chunk.text.length, tp: chunk.type});
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}
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plain += chunk.text;
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}
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return {txt: plain, fmt: ranges};
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}
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// Splice two strings: insert second string into the first one at the given index
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function splice(src, at, insert) {
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return src.slice(0, at) + insert + src.slice(at);
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}
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return {
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/**
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* Parse text into structured representation.
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*/
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parse: function(content) {
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// Split text into lines. It makes further processing easier.
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var lines = content.split(/\r?\n/);
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// Holds entities referenced from text
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var entityMap = [];
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var entityIndex = {};
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// Processing lines one by one, hold intermediate result in blx.
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var blx = [];
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lines.map(function(line) {
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var spans = [];
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var entities = [];
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// Find formatted spans in the string.
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// Try to match each style.
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INLINE_STYLES.map(function(style) {
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// Each style could be matched multiple times.
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spans = spans.concat(spannify(line, style.start, style.end, style.name));
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});
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var block;
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if (spans.length == 0) {
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block = {txt: line};
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} else {
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// Sort spans by style occurence early -> late
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spans.sort(function(a,b) {
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return a.start - b.start;
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});
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// Convert an array of possibly overlapping spans into a tree
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spans = toTree(spans);
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// Build a tree representation of the entire string, not
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// just the formatted parts.
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var chunks = chunkify(line, 0, line.length, spans);
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var drafty = draftify(chunks, 0);
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block = {txt: drafty.txt, fmt: drafty.fmt};
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}
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// Extract entities from the cleaned up string.
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entities = extractEntities(block.txt);
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if (entities.length > 0) {
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var ranges = [];
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for (var i in entities) {
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// {offset: match['index'], unique: match[0], len: match[0].length, data: ent.packer(), type: ent.name}
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var entity = entities[i];
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var index = entityIndex[entity.unique];
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if (!index) {
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index = entityMap.length;
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entityIndex[entity.unique] = index;
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entityMap.push({tp: entity.type, data: entity.data});
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}
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ranges.push({at: entity.offset, len: entity.len, key: index});
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}
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block.ent = ranges;
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}
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blx.push(block);
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});
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var result = {txt: ""};
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// Merge lines and save line breaks as BR inline formatting.
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if (blx.length > 0) {
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result.txt = blx[0].txt;
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result.fmt = (blx[0].fmt || []).concat(blx[0].ent || []);
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for (var i = 1; i<blx.length; i++) {
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var block = blx[i];
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var offset = result.txt.length + 1;
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result.fmt.push({tp: "BR", len: 1, at: offset - 1});
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result.txt += " " + block.txt;
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if (block.fmt) {
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result.fmt = result.fmt.concat(block.fmt.map(function(s) {
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s.at += offset; return s;
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}));
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}
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if (block.ent) {
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result.fmt = result.fmt.concat(block.ent.map(function(s) {
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s.at += offset; return s;
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}));
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}
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}
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if (result.fmt.length == 0) {
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delete result.fmt;
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}
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if (entityMap.length > 0) {
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result.ent = entityMap;
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}
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}
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return result;
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},
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/**
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* Given the structured representation of rich text, convert it to HTML.
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* No attempt is made to strip pre-existing html markup.
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* This is potentially unsafe because block.txt may contain malicious
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* markup.
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*
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* @param {drafy} content - structured representation of rich text.
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*
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* @return HTML-representation of content
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*/
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unsafeToHTML: function(content) {
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var {txt, fmt, ent} = content;
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var markup = [];
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if (fmt) {
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for (var i in fmt) {
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var range = fmt[i];
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var tp = range.tp, data;
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if (!tp) {
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var entity = ent[range.key];
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if (entity) {
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tp = entity.tp;
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data = entity.data;
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}
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}
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if (DECORATORS[tp]) {
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markup.push({idx: range.at, what: DECORATORS[tp].open(data)});
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markup.push({idx: range.at + range.len, what: DECORATORS[tp].close(data)});
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}
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}
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}
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markup.sort(function(a, b) {
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return b.idx - a.idx; // in descending order
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});
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for (var i in markup) {
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if (markup[i].what) {
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txt = splice(txt, markup[i].idx, markup[i].what);
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}
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}
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return txt;
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},
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/**
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* Transform using custom formatting.
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*
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|
* @param {Drafty} content - content to transform.
|
|
* @param {function} formatter - callback which transforms individual elements
|
|
* @param {Object} context - context provided to formatter as 'this'.
|
|
*
|
|
* @return {Object} context
|
|
*/
|
|
format: function(content, formatter, context) {
|
|
var {txt, fmt, ent} = content;
|
|
|
|
if (!fmt) {
|
|
return [txt];
|
|
}
|
|
|
|
var spans = [].concat(fmt);
|
|
|
|
// Soft spans first by start index (asc) then by length (desc).
|
|
spans.sort(function(a, b) {
|
|
if (a.at - b.at == 0) {
|
|
return b.len - a.len; // longer one comes first (<0)
|
|
}
|
|
return a.at - b.at;
|
|
});
|
|
|
|
// Denormalize entities into spans. Create a copy of the objects to leave
|
|
// original Drafty object unchanged.
|
|
spans = spans.map(function(s) {
|
|
var data;
|
|
var tp = s.tp;
|
|
if (s.key + 1 > 0) {
|
|
data = ent[s.key].data;
|
|
tp = ent[s.key].tp;
|
|
}
|
|
return {tp: tp, data: data, at: s.at, len: s.len};
|
|
});
|
|
|
|
return forEach(txt, 0, txt.length, spans, formatter, context);
|
|
},
|
|
|
|
/**
|
|
* Given structured representation of rich text, convert it to plain text.
|
|
*
|
|
* @param {drafty} content - content to convert to plain text.
|
|
*/
|
|
toPlainText: function(content) {
|
|
return content.text;
|
|
},
|
|
|
|
/**
|
|
* Returns true if content has no markup and no entities.
|
|
*
|
|
* @param {drafty} content - content to check for presence of markup.
|
|
* @returns true is content is plain text, false otherwise.
|
|
*/
|
|
isPlainText: function(content, noLineBreaks) {
|
|
return !(content.fmt || content.ent);
|
|
},
|
|
|
|
/**
|
|
* Get HTML tag for a given two-letter style name
|
|
* @param {string} style - two-letter style, like ST or LN
|
|
* @returns
|
|
*/
|
|
tagName: function(style) {
|
|
return HTML_TAGS[style] ? HTML_TAGS[style].name : undefined;
|
|
},
|
|
|
|
/**
|
|
* For a given data bundle generate an object with HTML attributes,
|
|
* for instance, given {url: "http://www.example.com/"} return
|
|
* {href: "http://www.example.com/"}
|
|
* @param {stting} style - tw-letter style to generate attributes for.
|
|
* @param {Object} data - data bundle to convert to attributes
|
|
* @returns object with HTML attributes.
|
|
*/
|
|
attrValue: function(style, data) {
|
|
if (data && DECORATORS[style]) {
|
|
return DECORATORS[style].props(data);
|
|
}
|
|
|
|
return undefined;
|
|
},
|
|
|
|
/**
|
|
* Content MIME type.
|
|
* @returns string suitabe for HTTP Content-Type field.
|
|
*/
|
|
getContentType: function() {
|
|
return "text/x-drafty";
|
|
}
|
|
|
|
};
|
|
});
|
|
|
|
// Export for the window object or node; Check that is not already defined.
|
|
if (typeof(environment.Drafty) === 'undefined') {
|
|
environment.Drafty = Drafty();
|
|
}
|
|
})(this); // 'this' will be a window object for the browsers.
|