bump app version

[Attempt to Generalize Number of Tags Sent to Server]

.gitignore

@@ -1,138 +0,0 @@
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-# Dependency directories
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-

README.md

@@ -1,2 +1,38 @@
-# im_webapp
+# Single-page chat with Tinode
 
+Example using [Tinode](https://github.com/tinode/chat/) to build a single-page chat application. The app uses
+[React](https://facebook.github.io/react/), Google's material design [fonts](https://www.google.com/fonts/)
+and [icons](https://google.github.io/material-design-icons/#icon-font-for-the-web). The [Tinode javascript library](https://github.com/tinode/tinode-js/) has no external dependencies. Overall it's a lot like open source WhatsApp or Telegram web apps.
+
+Although the app is generally usable, keep in mind that this is work in progress. Some bugs probably exist. The app was tested in the latest Chrome & Firefox only.
+
+Try possibly newer or older version live at https://api.tinode.co/x/example-react-js/. Login as one of `alice`, `bob`, `carol`, `dave`, `frank`. Password is `<login>123`, e.g. password for `alice` is `alice123`. You can discover other users by email or phone by prefixing them with `email:` or `tel:` respectively. Emails are `<login>@example.com`, e.g. `alice@example.com`, phones are `17025550001` through `17025550009`. The demo is reset every night at 2:15am Pacific time.
+
+License: [Apache 2.0](http://www.apache.org/licenses/LICENSE-2.0)
+
+Sample avatar photos from https://www.pexels.com/ under [CC0 license](https://www.pexels.com/photo-license/).
+
+Background pattern from http://subtlepatterns.com/, commercial and non-commercial use allowed with attribution.
+
+## Missing functionality
+
+* Previews not generated for videos, audio, links or docs.
+* No indication of some chat statuses (muted, blocked, etc.).
+* Browser push notifications are not implemented.
+* No end-to-end encryption.
+* Editing chat permissions is incomplete.
+* Emoji support is weak.
+
+## Responsive design
+
+### Desktop screenshot
+
+<p align="center">
+  <img src="web-desktop-2.png" alt="Desktop web: full app" width=866 />
+</p>
+
+### Mobile screenshots
+
+<p align="center">
+  <kbd><img src="web-mob-contacts-1.png" alt="Mobile web: contacts" width=323 /></kbd> <kbd><img src="web-mob-chat-1.png" alt="Mobile web: chat" width=323 /></kbd> <kbd><img src="web-mob-info-1.png" alt="Mobile web: topic info" width=323 /></kbd> <kbd><img src="web-mob-new-chat-1.png" alt="Mobile web: start new chat" width=323 /></kbd>
+</p>

drafty.js

@@ -0,0 +1,753 @@
+// Basic parser and formatter for very simple text markup. Mostly targeted at
+// mobile use cases similar to Telegram and WhatsApp.
+//
+// Supports:
+//   *abc* -> <b>abc</b>
+//   _abc_ -> <i>abc</i>
+//   ~abc~ -> <del>abc</del>
+//   `abc` -> <tt>abc</tt>
+// Nested frmatting is supported, e.g. *abc _def_* -> <b>abc <i>def</i></b>
+//
+// URLs, @mentions, and #hashtags are extracted and converted into links.
+//
+// JSON data representation is inspired by Draft.js raw formatting.
+
+/*
+Text:
+    this is *bold*, `code` and _italic_, ~strike~
+    combined *bold and _italic_*
+    an url: https://www.example.com/abc#fragment and another _www.tinode.co_
+    this is a @mention and a #hashtag in a string
+    second #hashtag
+
+Sample JSON representation of the text above:
+{
+   "txt": "this is bold, code and italic, strike combined bold and italic an url: https://www.example.com/abc#fragment " +
+           "and another www.tinode.co this is a @mention and a #hashtag in a string second #hashtag",
+   "fmt": [
+       { "at":8, "len":4,"tp":"ST" },{ "at":14, "len":4, "tp":"CO" },{ "at":23, "len":6, "tp":"EM"},
+       { "at":31, "len":6, "tp":"DL" },{ "tp":"BR", "len":1, "at":37 },{ "at":56, "len":6, "tp":"EM" },
+       { "at":47, "len":15, "tp":"ST" },{ "tp":"BR", "len":1, "at":62 },{ "at":120, "len":13, "tp":"EM" },
+       { "at":71, "len":36, "key":0 },{ "at":120, "len":13, "key":1 },{ "tp":"BR", "len":1, "at":133 },
+       { "at":144, "len":8, "key":2 },{ "at":159, "len":8, "key":3 },{ "tp":"BR", "len":1, "at":179 },
+       { "at":187, "len":8, "key":3 },{ "tp":"BR", "len":1, "at":195 }
+   ],
+   "ent": [
+       { "tp":"LN", "data":{ "url":"https://www.example.com/abc#fragment" } },
+       { "tp":"LN", "data":{ "url":"http://www.tinode.co" } },
+       { "tp":"MN", "data":{ "val":"mention" } },
+       { "tp":"HT", "data":{ "val":"hashtag" } }
+   ]
+}
+*/
+
+(function(environment) { // closure for web browsers
+  'use strict';
+
+  // Regular expressions for parsing inline formats. Javascript does not support lookbehind,
+  // so it's a bit messy.
+  var INLINE_STYLES = [
+    // Strong = bold, *bold text*
+    {name: "ST", start: /(?:^|\W)(\*)[^\s*]/, end: /[^\s*](\*)(?=$|\W)/},
+    // Emphesized = italic, _italic text_
+    {name: "EM", start: /(?:^|[\W_])(_)[^\s_]/, end: /[^\s_](_)(?=$|[\W_])/},
+    // Deleted, ~strike this though~
+    {name: "DL", start: /(?:^|\W)(~)[^\s~]/, end: /[^\s~](~)(?=$|\W)/},
+    // Code block `this is monospace`
+    {name: "CO", start: /(?:^|\W)(`)[^`]/, end: /[^`](`)(?=$|\W)/}
+  ];
+
+  // RegExps for entity extraction (RF = reference)
+  var ENTITY_TYPES = [
+    // URLs
+    {name: "LN", dataName: "url",
+      pack: function(val) {
+        // Check if the protocol is specified, if not use http
+        if (!/^[a-z]+:\/\//i.test(val)) {
+          val = 'http://' + val;
+        }
+        return {url: val};
+      },
+      re: /(https?:\/\/)?(?:www\.)?[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,4}\b(?:[-a-zA-Z0-9@:%_\+.~#?&//=]*)/g},
+    // Mentions @user (must be 2 or more characters)
+    {name: "MN", dataName: "val",
+      pack: function(val) { return {val: val.slice(1)}; },
+      re: /\B@(\w\w+)/g},
+    // Hashtags #hashtag, like metion 2 or more characters.
+    {name: "HT", dataName: "val",
+      pack: function(val) { return {val: val.slice(1)}; },
+      re: /\B#(\w\w+)/g}
+  ];
+
+  // HTML tag name suggestions
+  var HTML_TAGS = {
+    ST: { name: 'b', isVoid: false },
+    EM: { name: 'i', isVoid: false },
+    DL: { name: 'del', isVoid: false },
+    CO: { name: 'tt', isVoid: false },
+    BR: { name: 'br', isVoid: true },
+    LN: { name: 'a', isVoid: false },
+    MN: { name: 'a', isVoid: false },
+    HT: { name: 'a', isVoid: false },
+    IM: { name: 'img', isVoid: true }
+  };
+
+  // Convert base64-encoded string into Blob.
+  function base64toObjectUrl(b64, contentType) {
+    var bin = atob(b64);
+    var length = bin.length;
+    var buf = new ArrayBuffer(length);
+    var arr = new Uint8Array(buf);
+    for (var i = 0; i < length; i++) {
+      arr[i] = bin.charCodeAt(i);
+    }
+
+    return URL.createObjectURL(new Blob([buf], {type: contentType}));
+  }
+
+  // Helpers for converting Drafty to HTML.
+  var DECORATORS = {
+    ST: { open: function() { return '<b>'; }, close: function() { return '</b>'; }},
+    EM: { open: function() { return '<i>'; }, close: function() { return '</i>'}},
+    DL: { open: function() { return '<del>'; }, close: function() { return '</del>'}},
+    CO: { open: function() { return '<tt>'; }, close: function() { return '</tt>'}},
+    BR: { open: function() { return ''; }, close: function() { return '<br/>'}},
+    LN: {
+      open: function(data) { return '<a href="' + data.url + '">'; },
+      close: function(data) { return '</a>'; },
+      props: function(data) { return { href: data.url, target: "_blank" }; },
+    },
+    MN: {
+      open: function(data) { return '<a href="#' + data.val + '">'; },
+      close: function(data) { return '</a>'; },
+      props: function(data) { return { name: data.val }; },
+    },
+    HT: {
+      open: function(data) { return '<a href="#' + data.val + '">'; },
+      close: function(data) { return '</a>'; },
+      props: function(data) { return { name: data.val }; },
+    },
+    IM: {
+      open: function(data) {
+        var blobUrl = base64toObjectUrl(data.val, data.mime);
+        var res = (data.name ? '<a href="' + blobUrl + '" download="' + data.name + '">' : '') +
+          '<img src="' + blobUrl + '"' +
+            (data.width ? ' width="' + data.width + '"' : '') +
+            (data.height ? ' height="' + data.height + '"' : '') + ' border="0" />';
+        console.log("open: " + res);
+        return res;
+      },
+      close: function(data) {
+        return (data.name ? '</a>' : '');
+      },
+      props: function(data) {
+        var url = base64toObjectUrl(data.val, data.mime);
+        return {
+          src: url,
+          title: data.name,
+          'data-width': data.width,
+          'data-height': data.height,
+          'data-name': data.name,
+          'data-size': (data.val.length * 0.75) | 0,
+          'data-mime': data.mime
+        };
+      },
+    }
+  };
+
+  var Drafty = (function() {
+
+    // Take a string and defined earlier style spans, re-compose them into a tree where each leaf is
+    // a same-style (including unstyled) string. I.e. 'hello *bold _italic_* and ~more~ world' ->
+    // ('hello ', (b: 'bold ', (i: 'italic')), ' and ', (s: 'more'), ' world');
+    //
+    // This is needed in order to clear markup, i.e. 'hello *world*' -> 'hello world' and convert
+    // ranges from markup-ed offsets to plain text offsets.
+    function chunkify(line, start, end, spans) {
+      var chunks = [];
+
+      if (spans.length == 0) {
+        return [];
+      }
+
+      for (var i in spans) {
+        // Get the next chunk from the queue
+        var span = spans[i];
+
+        // Grab the initial unstyled chunk
+        if (span.start > start) {
+          chunks.push({text: line.slice(start, span.start)});
+        }
+
+        // Grab the styled chunk. It may include subchunks.
+        var chunk = {type: span.type};
+        var chld = chunkify(line, span.start + 1, span.end - 1, span.children);
+        if (chld.length > 0) {
+          chunk.children = chld;
+        } else {
+          chunk.text = span.text;
+        }
+        chunks.push(chunk);
+        start = span.end + 1; // '+1' is to skip the formatting character
+      }
+
+      // Grab the remaining unstyled chunk, after the last span
+      if (start < end) {
+        chunks.push({text: line.slice(start, end)});
+      }
+
+      return chunks;
+    }
+
+    // Same as chunkify but used for formatting.
+    function forEach(line, start, end, spans, formatter, context) {
+      // Add un-styled range before the styled span starts.
+      // Process ranges calling formatter for each range.
+      var result = [];
+      for (var i = 0; i < spans.length; i++) {
+        var span = spans[i];
+
+        // Add un-styled range before the styled span starts.
+        if (start < span.at) {
+          result.push(formatter.call(context, null, undefined, line.slice(start, span.at)));
+          start = span.at;
+        }
+        // Get all spans which are within current span.
+        var subspans = [];
+        for (var si = i + 1; si < spans.length && spans[si].at < span.at + span.len; si++) {
+          subspans.push(spans[si]);
+          i = si;
+        }
+
+        var tag = HTML_TAGS[span.tp] || {};
+        result.push(formatter.call(context, span.tp, span.data,
+          tag.isVoid ? null : forEach(line, start, span.at + span.len, subspans, formatter, context)));
+
+        start = span.at + span.len;
+      }
+
+      // Add the last unformatted range.
+      if (start < end) {
+        result.push(formatter.call(context, null, undefined, line.slice(start, end)));
+      }
+
+      return result;
+    }
+
+    // Detect starts and ends of formatting spans. Unformatted spans are
+    // ignored at this stage.
+    function spannify(original, re_start, re_end, type) {
+      var result = [];
+      var index = 0;
+      var line = original.slice(0); // make a copy;
+
+      while (line.length > 0) {
+        // match[0]; // match, like '*abc*'
+        // match[1]; // match captured in parenthesis, like 'abc'
+        // match['index']; // offset where the match started.
+
+        // Find the opening token.
+        var start = re_start.exec(line);
+        if (start == null) {
+          break;
+        }
+
+        // Because javascript RegExp does not support lookbehind, the actual offset may not point
+        // at the markup character. Find it in the matched string.
+        var start_offset = start['index'] + start[0].lastIndexOf(start[1]);
+        // Clip the processed part of the string.
+        line = line.slice(start_offset + 1);
+        // start_offset is an offset within the clipped string. Convert to original index.
+        start_offset += index;
+        // Index now point to the beginning of 'line' within the 'original' string.
+        index = start_offset + 1;
+
+        // Find the matching closing token.
+        var end = re_end ? re_end.exec(line) : null;
+        if (end == null) {
+          break;
+        }
+        var end_offset = end['index'] + end[0].indexOf(end[1]);
+        // Clip the processed part of the string.
+        line = line.slice(end_offset + 1);
+        // Update offsets
+        end_offset += index;
+        // Index now point to the beginning of 'line' within the 'original' string.
+        index = end_offset + 1;
+
+        result.push({
+          text: original.slice(start_offset+1, end_offset),
+          children: [],
+          start: start_offset,
+          end: end_offset,
+          type: type
+        });
+      }
+
+      return result;
+    }
+
+    // Convert linear array or spans into a tree representation.
+    // Keep standalone and nested spans, throw away partially overlapping spans.
+    function toTree(spans) {
+      if (spans.length == 0) {
+        return [];
+      }
+
+      var tree = [spans[0]];
+      var last = spans[0];
+      for (var i = 1; i < spans.length; i++) {
+        // Keep spans which start after the end of the previous span or those which
+        // are complete within the previous span.
+
+        if (spans[i].start > last.end) {
+          // Span is completely outside of the previous span.
+          tree.push(spans[i]);
+          last = spans[i];
+        } else if (spans[i].end < last.end) {
+          // Span is fully inside of the previous span. Push to subnode.
+          last.children.push(spans[i]);
+        }
+        // Span could partially overlap, ignoring it as invalid.
+      }
+
+      // Recursively rearrange the subnodes.
+      for (var i in tree) {
+        tree[i].children = toTree(tree[i].children);
+      }
+
+      return tree;
+    }
+
+    // Get a list of entities from a text.
+    function extractEntities(line) {
+      var match;
+      var extracted = [];
+      ENTITY_TYPES.map(function(entity) {
+        while ((match = entity.re.exec(line)) !== null) {
+          extracted.push({
+            offset: match['index'],
+            len: match[0].length,
+            unique: match[0],
+            data: entity.pack(match[0]),
+            type: entity.name});
+        }
+      });
+
+      if (extracted.length == 0) {
+        return extracted;
+      }
+
+      // Remove entities detected inside other entities, like #hashtag in a URL.
+      extracted.sort(function(a,b) {
+        return a.offset - b.offset;
+      });
+
+      var idx = -1;
+      extracted = extracted.filter(function(el) {
+        var result = (el.offset > idx);
+        idx = el.offset + el.len;
+        return result;
+      });
+
+      return extracted;
+    }
+
+    // Convert the chunks into format suitable for serialization.
+    function draftify(chunks, startAt) {
+      var plain = "";
+      var ranges = [];
+      for (var i in chunks) {
+        var chunk = chunks[i];
+        if (!chunk.text) {
+          var drafty = draftify(chunk.children, plain.length + startAt);
+          chunk.text = drafty.txt;
+          ranges = ranges.concat(drafty.fmt);
+        }
+
+        if (chunk.type) {
+          ranges.push({at: plain.length + startAt, len: chunk.text.length, tp: chunk.type});
+        }
+
+        plain += chunk.text;
+      }
+      return {txt: plain, fmt: ranges};
+    }
+
+    // Splice two strings: insert second string into the first one at the given index
+    function splice(src, at, insert) {
+      return src.slice(0, at) + insert + src.slice(at);
+    }
+
+    return {
+
+      /**
+       * Parse plain text into structured representation.
+       */
+      parse: function(content) {
+        // Make sure we are parsing strings only.
+        if (typeof content != "string") {
+          return null;
+        }
+
+        // Split text into lines. It makes further processing easier.
+        var lines = content.split(/\r?\n/);
+
+        // Holds entities referenced from text
+        var entityMap = [];
+        var entityIndex = {};
+
+        // Processing lines one by one, hold intermediate result in blx.
+        var blx = [];
+        lines.map(function(line) {
+          var spans = [];
+          var entities = [];
+
+          // Find formatted spans in the string.
+          // Try to match each style.
+          INLINE_STYLES.map(function(style) {
+            // Each style could be matched multiple times.
+            spans = spans.concat(spannify(line, style.start, style.end, style.name));
+          });
+
+          var block;
+          if (spans.length == 0) {
+            block = {txt: line};
+          } else {
+            // Sort spans by style occurence early -> late
+            spans.sort(function(a,b) {
+              return a.start - b.start;
+            });
+
+            // Convert an array of possibly overlapping spans into a tree
+            spans = toTree(spans);
+
+            // Build a tree representation of the entire string, not
+            // just the formatted parts.
+            var chunks = chunkify(line, 0, line.length, spans);
+
+            var drafty = draftify(chunks, 0);
+
+            block = {txt: drafty.txt, fmt: drafty.fmt};
+          }
+
+          // Extract entities from the cleaned up string.
+          entities = extractEntities(block.txt);
+          if (entities.length > 0) {
+            var ranges = [];
+            for (var i in entities) {
+              // {offset: match['index'], unique: match[0], len: match[0].length, data: ent.packer(), type: ent.name}
+              var entity = entities[i];
+              var index = entityIndex[entity.unique];
+              if (!index) {
+                index = entityMap.length;
+                entityIndex[entity.unique] = index;
+                entityMap.push({tp: entity.type, data: entity.data});
+              }
+              ranges.push({at: entity.offset, len: entity.len, key: index});
+            }
+            block.ent = ranges;
+          }
+
+          blx.push(block);
+        });
+
+        var result = {txt: ""};
+
+        // Merge lines and save line breaks as BR inline formatting.
+        if (blx.length > 0) {
+          result.txt = blx[0].txt;
+          result.fmt = (blx[0].fmt || []).concat(blx[0].ent || []);
+
+          for (var i = 1; i<blx.length; i++) {
+            var block = blx[i];
+            var offset = result.txt.length + 1;
+
+            result.fmt.push({tp: "BR", len: 1, at: offset - 1});
+
+            result.txt += " " + block.txt;
+            if (block.fmt) {
+              result.fmt = result.fmt.concat(block.fmt.map(function(s) {
+                s.at += offset; return s;
+              }));
+            }
+            if (block.ent) {
+              result.fmt = result.fmt.concat(block.ent.map(function(s) {
+                s.at += offset; return s;
+              }));
+            }
+          }
+
+          if (result.fmt.length ==  0) {
+            delete result.fmt;
+          }
+
+          if (entityMap.length > 0) {
+            result.ent = entityMap;
+          }
+        }
+        return result;
+      },
+
+      /**
+       * Add inline image to drafty content
+       *
+       * @param {Drafty} content object to add image to
+       * @param {integer} at index where the object is inserted
+       * @param {string} mime mime-type of the image, e.g. "image/png"
+       * @param {string} bits base64-encoded image content
+       * @param {integer} width width of the image
+       * @param {integer} height height of the image
+       * @param {string} fname file name suggestion for downloading the image.
+       */
+      insertImage: function(content, at, mime, base64bits, width, height, fname) {
+        content = content || {txt: " "};
+        content.ent = content.ent || [];
+        content.fmt = content.fmt || [];
+
+        content.fmt.push({
+          at: at,
+          len: 1,
+          key: content.ent.length
+        });
+        content.ent.push({
+          tp: "IM",
+          data: {
+            mime: mime,
+            val: base64bits,
+            width: width,
+            height: height,
+            name: fname
+          }
+        });
+
+        return content;
+      },
+
+      attachFile: function(content, mime, base64bits, fname) {
+        content = content || {txt: ""};
+        content.ent = content.ent || [];
+        content.fmt = content.fmt || [];
+
+        content.fmt.push({
+          at: -1,
+          len: 0,
+          key: content.ent.length
+        });
+
+        content.ent.push({
+          tp: "EX",
+          data: {
+            mime: mime,
+            val: base64bits,
+            name: fname
+          }
+        });
+
+        return content;
+      },
+
+      /**
+       * Given the structured representation of rich text, convert it to HTML.
+       * No attempt is made to strip pre-existing html markup.
+       * This is potentially unsafe because block.txt may contain malicious
+       * markup.
+       *
+       * @param {drafy} content - structured representation of rich text.
+       *
+       * @return HTML-representation of content
+       */
+      unsafeToHTML: function(content) {
+        var {txt, fmt, ent} = content;
+
+        var markup = [];
+        if (fmt) {
+          for (var i in fmt) {
+            var range = fmt[i];
+            var tp = range.tp, data;
+            if (!tp) {
+              var entity = ent[range.key];
+              if (entity) {
+                tp = entity.tp;
+                data = entity.data;
+              }
+            }
+
+            if (DECORATORS[tp]) {
+              // Because we later sort in descending order, closing markup must come first.
+              // Otherwise zero-length objects will not be represented correctly.
+              markup.push({idx: range.at + range.len, what: DECORATORS[tp].close(data)});
+              markup.push({idx: range.at, what: DECORATORS[tp].open(data)});
+            }
+          }
+        }
+
+        markup.sort(function(a, b) {
+          return b.idx - a.idx; // in descending order
+        });
+
+        for (var i in markup) {
+          if (markup[i].what) {
+            txt = splice(txt, markup[i].idx, markup[i].what);
+          }
+        }
+
+        return txt;
+      },
+
+      /**
+       * Transform using custom formatting.
+       *
+       * @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;
+
+        txt = txt || "";
+
+        if (!fmt) {
+          return [txt];
+        }
+
+        var spans = [].concat(fmt);
+
+        // Zero values may have been stripped. Restore them.
+        spans.map(function(s) {
+          s.at = s.at || 0;
+          s.len = s.len || 0;
+        });
+
+        // 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 (!tp) {
+            s.key = s.key || 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);
+      },
+
+      /**
+       * Check if the drafty content has attachments.
+       *
+       * @param {Drafty} content - content to check for attachments.
+       * @returns true if there are attachments.
+       */
+      hasAttachment: function(content) {
+        if (content.ent && content.ent.length > 0) {
+          for (var i in content.ent) {
+            if (content.ent[i].tp == "EX") {
+              return true;
+            }
+          }
+        }
+        return false;
+      },
+
+      /**
+       * Enumerate attachments
+       *
+       * @param {Drafty} content - drafty object to process for attachments.
+       * @param {function} callback - callback to call for each attachment.
+       * @param {Object} content - value of "this" for callback.
+       */
+      attachments: function(content, callback, context) {
+        if (content.ent && content.ent.length > 0) {
+          for (var i in content.ent) {
+            if (content.ent[i].tp == "EX") {
+              callback.call(context, content.ent[i].data, i);
+            }
+          }
+        }
+      },
+
+      // Get blob URL for a given entity
+      getBlobUrl: function(entity) {
+        return base64toObjectUrl(entity.val, entity.mime);
+      },
+
+      getAttachmentSize: function(entity) {
+        // Value is base64 encoded. The actual object size is smaller than the encoded length.
+        return entity.val ? (entity.val.length * 0.75) | 0 : 0;
+      },
+
+      getAttachmentType: function(entity) {
+        return entity.mime || "text/plain";
+      },
+      /**
+       * 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 {string} 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.