Bug 1143844 - Check document for readerable content to determine whether or not to show reader button. r=Gijs

--HG--
extra : rebase_source : 7a849952243aa5ff8d4711a1f0308747558faa2f

toolkit/components/reader/ReaderMode.jsm

@@ -63,14 +63,47 @@ this.ReaderMode = {
 
   /**
    * Decides whether or not a document is reader-able without parsing the whole thing.
-   * XXX: In the future, this should be smarter (bug 1143844).
    *
    * @param doc A document to parse.
    * @return boolean Whether or not we should show the reader mode button.
    */
   isProbablyReaderable: function(doc) {
     let uri = Services.io.newURI(doc.documentURI, null, null);
-    return this._shouldCheckUri(uri);
+
+    if (!this._shouldCheckUri(uri)) {
+      return false;
+    }
+
+    let REGEXPS = {
+      unlikelyCandidates: /combx|comment|community|disqus|extra|foot|header|menu|remark|rss|shoutbox|sidebar|sponsor|ad-break|agegate|pagination|pager|popup|tweet|twitter/i,
+      okMaybeItsACandidate: /and|article|body|column|main|shadow/i,
+    };
+
+    let nodes = doc.getElementsByTagName("p");
+    if (nodes.length < 5) {
+      return false;
+    }
+
+    let possibleParagraphs = 0;
+    for (let i = 0; i < nodes.length; i++) {
+      let node = nodes[i];
+      let matchString = node.className + " " + node.id;
+
+      if (REGEXPS.unlikelyCandidates.test(matchString) &&
+          !REGEXPS.okMaybeItsACandidate.test(matchString)) {
+        continue;
+      }
+
+      if (node.textContent.trim().length < 200) {
+        continue;
+      }
+
+      possibleParagraphs++;
+      if (possibleParagraphs >= 5) {
+        return true;
+      }
+    }
+    return false;
   },
 
   /**