1 files changed, 82 insertions, 0 deletions
diff --git a/packages/gitbook-core/src/reducers/history.js b/packages/gitbook-core/src/reducers/history.js
new file mode 100644
index 0000000..be8fe42
--- /dev/null
+++ b/packages/gitbook-core/src/reducers/history.js
@@ -0,0 +1,82 @@
+const { Record, List } = require('immutable');
+const { createBrowserHistory, createMemoryHistory } = require('history');
+const ACTION_TYPES = require('../actions/TYPES');
+const Location = require('../models/Location');
+
+const isServerSide = (typeof window === 'undefined');
+
+const HistoryState = Record({
+    // Current location
+    location:  new Location(),
+    // Are we loading a new page
+    loading:   Boolean(false),
+    // Did we fail loading a page?
+    error:     null,
+    // Listener for history changes
+    listeners: List(),
+    // Function to call to stop listening
+    unlisten:  null,
+    // HistoryJS instance
+    client:    null
+});
+
+function reduceHistory(state, action) {
+    state = state || HistoryState();
+    switch (action.type) {
+
+    case ACTION_TYPES.PAGE_FETCH_START:
+        return state.merge({
+            loading: true
+        });
+
+    case ACTION_TYPES.PAGE_FETCH_END:
+        return state.merge({
+            loading: false
+        });
+
+    case ACTION_TYPES.PAGE_FETCH_ERROR:
+        return state.merge({
+            loading: false,
+            error:   action.error
+        });
+
+    case ACTION_TYPES.HISTORY_ACTIVATE:
+        const client = isServerSide ? createMemoryHistory() : createBrowserHistory();
+        const unlisten = client.listen(action.listener);
+
+        // We can't use .merge since it convert history to an immutable
+        const newState = state
+            // TODO: we should find a way to have the correct location on server side
+            .set('location', isServerSide ? new Location() : Location.fromNative(window.location))
+            .set('client', client)
+            .set('unlisten', unlisten);
+
+        return newState;
+
+    case ACTION_TYPES.HISTORY_DEACTIVATE:
+        if (state.unlisten) {
+            state.unlisten();
+        }
+
+        return state.merge({
+            client:   null,
+            unlisten: null
+        });
+
+    case ACTION_TYPES.HISTORY_UPDATE:
+        return state.merge({
+            location: action.location
+        });
+
+    case ACTION_TYPES.HISTORY_LISTEN:
+        return state.merge({
+            listeners: state.listeners.push(action.listener)
+        });
+
+    default:
+        return state;
+
+    }
+}
+
+module.exports = reduceHistory;