1 files changed, 31 insertions, 0 deletions
diff --git a/packages/gitbook-core/src/models/StateSummary.js b/packages/gitbook-core/src/models/StateSummary.js
new file mode 100644
index 0000000..f268f34
--- /dev/null
+++ b/packages/gitbook-core/src/models/StateSummary.js
@@ -0,0 +1,31 @@
+const { Record, List } = require('immutable');
+
+const File = require('../models/File');
+const SummaryPart = require('../models/SummaryPart');
+
+const DEFAULTS = {
+    file: new File(),
+    parts: List()
+};
+
+/**
+ * State for the summary.
+ * @type {Record}
+ */
+class StateSummary extends Record(DEFAULTS) {
+    constructor(state = {}) {
+        super({
+            ...state,
+            file:  new File(state.file),
+            parts: (new List(state.parts))
+                .map(article => new SummaryPart(article))
+        });
+    }
+
+    static create(state) {
+        return state instanceof StateSummary ?
+            state : new StateSummary(state);
+    }
+}
+
+module.exports = StateSummary;