Fix #952: add configuration for index maximum size

lib/book.js

@@ -19,8 +19,6 @@ var PluginsList = require("./pluginslist");
 
 var generators = require("./generators");
 
-var SEARCHINDEX_MAXSIZE = 1000000;
-
 var Book = function(root, context, parent) {
     this.context = _.defaults(context || {}, {
         // Extend book configuration
@@ -751,7 +749,7 @@ Book.prototype.indexPage = function(page) {
 
     // Limit size of index (to avoid #941)
     this.searchIndexSize = this.searchIndexSize + text.length;
-    if (this.searchIndexSize > SEARCHINDEX_MAXSIZE) {
+    if (this.searchIndexSize > this.config.get('search.maxIndexSize')) {
         this.log.warn.ln("search index is too big, indexing is now disabled");
         this.searchIndexEnabled = false;
         return;

lib/configuration.js

@@ -201,6 +201,11 @@ Configuration.DEFAULT = {
     // version of gitbook to use
     "gitbook": "*",
 
+    // Search index
+    "search": {
+        "maxIndexSize": 1000000
+    },
+
     // Structure
     "structure": {
         "langs": "LANGS.md",