[Nav] Prevent duplicate routing on double-tapping links (#58)

Note: Remove if update to React-Navigation fixes issue: react-navigation/react-navigation#723

Author: computerjazz

Diff for: src/scopes/navigation/reducer.js

@@ -1,5 +1,7 @@
 //@flow
 import AppNavigator from './navigator'
+import _ from 'lodash'
+
 import type { Action } from '../types.js'
 
 // @TODO can we type this better or get type from react-navigation [zack]
@@ -8,10 +10,29 @@ export type State = {
   index: number,
 };
 
-export default (state, action) => {
+function isDuplicateRoute(originalRoute, newRoute) {
+  while (originalRoute && originalRoute.index >= 0) {
+    originalRoute = originalRoute.routes[originalRoute.index]
+  }
+
+  while (newRoute && newRoute.index >= 0) {
+    newRoute = newRoute.routes[newRoute.index]
+  }
+
+  if (_.isEqual(originalRoute, newRoute)) {
+    console.log('## Duplicate navigation stack push, skipping')
+    return true
+  } else
+    return false
+}
+
+export default (state: ?State, action: Action) => {
   const appNavigatorState = AppNavigator.router.getStateForAction(
     action,
     state
   )
+
+  if (isDuplicateRoute(state, appNavigatorState)) return state
+
   return appNavigatorState || state
 }