10 files changed, 94 insertions, 5 deletions
diff --git a/packages/gitbook-core/src/models/File.js b/packages/gitbook-core/src/models/File.js
index 74db11e..c5ac654 100644
--- a/packages/gitbook-core/src/models/File.js
+++ b/packages/gitbook-core/src/models/File.js
@@ -35,7 +35,7 @@ class File extends Record(DEFAULTS) {
     /**
      * Return true if file is an instance of File
      * @param {Mixed} file
-     * @return {Boolean}
+     * @return {Boolean} isFile
      */
     static is(file) {
         return (file instanceof File);
@@ -44,7 +44,7 @@ class File extends Record(DEFAULTS) {
     /**
      * Create a file instance
      * @param {Mixed|File} file
-     * @return {File}
+     * @return {File} file
      */
     static create(file) {
         return File.is(file) ?
diff --git a/packages/gitbook-core/src/models/Language.js b/packages/gitbook-core/src/models/Language.js
new file mode 100644
index 0000000..20fc237
--- /dev/null
+++ b/packages/gitbook-core/src/models/Language.js
@@ -0,0 +1,12 @@
+const { Record } = require('immutable');
+
+const DEFAULTS = {
+    id:    null,
+    title: null
+};
+
+class Language extends Record(DEFAULTS) {
+
+}
+
+module.exports = Language;
diff --git a/packages/gitbook-core/src/models/Languages.js b/packages/gitbook-core/src/models/Languages.js
new file mode 100644
index 0000000..b698d14
--- /dev/null
+++ b/packages/gitbook-core/src/models/Languages.js
@@ -0,0 +1,40 @@
+const { Record, List } = require('immutable');
+const Language = require('./Language');
+const File = require('./File');
+
+const DEFAULTS = {
+    current: String(),
+    file:    new File(),
+    list:    List()
+};
+
+class Languages extends Record(DEFAULTS) {
+    constructor(spec = {}) {
+        super({
+            ...spec,
+            file: File.create(spec.file),
+            list: List(spec.list).map(lang => new Language(lang))
+        });
+    }
+
+    /**
+     * Return true if file is an instance of Languages
+     * @param {Mixed} langs
+     * @return {Boolean}
+     */
+    static is(langs) {
+        return (langs instanceof Languages);
+    }
+
+    /**
+     * Create a Languages instance
+     * @param {Mixed|Languages} langs
+     * @return {Languages}
+     */
+    static create(langs) {
+        return Languages.is(langs) ?
+            langs : new Languages(langs);
+    }
+}
+
+module.exports = Languages;
diff --git a/packages/gitbook-core/src/reducers/index.js b/packages/gitbook-core/src/reducers/index.js
index fc80b4a..a211d3b 100644
--- a/packages/gitbook-core/src/reducers/index.js
+++ b/packages/gitbook-core/src/reducers/index.js
@@ -10,5 +10,6 @@ module.exports = composeReducer(
     createReducer('file', require('./file')),
     createReducer('page', require('./page')),
     createReducer('summary', require('./summary')),
-    createReducer('readme', require('./readme'))
+    createReducer('readme', require('./readme')),
+    createReducer('languages', require('./languages'))
 );
diff --git a/packages/gitbook-core/src/reducers/languages.js b/packages/gitbook-core/src/reducers/languages.js
new file mode 100644
index 0000000..0ec2ae4
--- /dev/null
+++ b/packages/gitbook-core/src/reducers/languages.js
@@ -0,0 +1,12 @@
+const Languages = require('../models/Languages');
+
+module.exports = (state, action) => {
+    state = Languages.create(state);
+
+    switch (action.type) {
+
+    default:
+        return state;
+
+    }
+};
diff --git a/packages/gitbook-core/src/shapes/Language.js b/packages/gitbook-core/src/shapes/Language.js
new file mode 100644
index 0000000..eea37a7
--- /dev/null
+++ b/packages/gitbook-core/src/shapes/Language.js
@@ -0,0 +1,7 @@
+const React  = require('react');
+const { string, shape } = React.PropTypes;
+
+module.exports = shape({
+    id:    string.isRequired,
+    title: string.isRequired
+});
diff --git a/packages/gitbook-core/src/shapes/Languages.js b/packages/gitbook-core/src/shapes/Languages.js
new file mode 100644
index 0000000..076aec5
--- /dev/null
+++ b/packages/gitbook-core/src/shapes/Languages.js
@@ -0,0 +1,12 @@
+const React  = require('react');
+const { listOf } = require('react-immutable-proptypes');
+const { shape, string } = React.PropTypes;
+
+const fileShape = require('./File');
+const languageShape = require('./Language');
+
+module.exports = shape({
+    current: string.isRequired,
+    file: fileShape.isRequired,
+    list: listOf(languageShape).isRequired
+});
diff --git a/packages/gitbook-core/src/shapes/index.js b/packages/gitbook-core/src/shapes/index.js
index 8b28842..f56b78c 100644
--- a/packages/gitbook-core/src/shapes/index.js
+++ b/packages/gitbook-core/src/shapes/index.js
@@ -9,6 +9,8 @@ module.exports = {
     Page:           require('./Page'),
     File:           require('./File'),
     History:        require('./History'),
+    Language:       require('./Language'),
+    Languages:      require('./Languages'),
     Location:       require('./Location'),
     Readme:         require('./Readme'),
     Summary:        require('./Summary'),
diff --git a/packages/gitbook/src/json/encodeLanguages.js b/packages/gitbook/src/json/encodeLanguages.js
index e1ef2ef..809cfb2 100644
--- a/packages/gitbook/src/json/encodeLanguages.js
+++ b/packages/gitbook/src/json/encodeLanguages.js
@@ -4,15 +4,17 @@ const encodeFile = require('./encodeFile');
  * Encode a languages listing to JSON
  *
  * @param  {Languages} languages
+ * @param  {String} currentLanguage
  * @param  {URIIndex} urls
  * @return {JSON} json
 */
-function encodeLanguages(languages, urls) {
+function encodeLanguages(languages, currentLanguage, urls) {
     const file = languages.getFile();
     const list = languages.getList();
 
     return {
         file: encodeFile(file, urls),
+        current: currentLanguage,
         list: list
             .valueSeq()
             .map(function(lang) {
diff --git a/packages/gitbook/src/json/encodeState.js b/packages/gitbook/src/json/encodeState.js
index fb3e164..faac972 100644
--- a/packages/gitbook/src/json/encodeState.js
+++ b/packages/gitbook/src/json/encodeState.js
@@ -31,7 +31,8 @@ function encodeStateToJSON(output, page) {
         glossary: encodeGlossary(book.getGlossary(), urls),
         readme: encodeReadme(book.getReadme(), urls),
         config: book.getConfig().getValues().toJS(),
-        languages: book.isMultilingual() ? encodeLanguages(book.getLanguages(), urls) : undefined,
+        languages: book.isMultilingual() ?
+            encodeLanguages(book.getLanguages(), book.getLanguage(), urls) : undefined,
 
         page: page ? encodePage(page, book.getSummary(), urls) : undefined,
         file: page ? encodeFile(page.getFile(), urls) : undefined