Update Native.NavigationNativeContainer so allow us to restore state

Author: MoOx

src/Native.re

@@ -1,12 +1,105 @@
+/*
+ # Example with state persistance
+
+ Require to have
+ - @reason-react-native/storage (ReactNativeAsyncStorage)
+ - reason-future
+
+ Require to define your own
+
+ - <RootNavigator />
+ - <BootSplash />
+
+
+ ```reason
+ open Belt;
+ open ReactNative;
+
+ // @todo
+ // <RootNavigator />
+ // <Bootsplash />
+
+ type navigationState;
+ let navigationStateStorageKey = "react-navigation:state";
+
+ [@react.component]
+ let app = () => {
+   let (initialStateContainer, setInitialState) = React.useState(() => None);
+
+   React.useEffect1(
+     () => {
+       if (initialStateContainer->Option.isNone) {
+         ReactNativeAsyncStorage.getItem(navigationStateStorageKey)
+         ->FutureJs.fromPromise(error => {
+             // @todo ?
+             Js.log2("Restoring Navigation State: ", error);
+             error;
+           })
+         ->Future.tap(res => {
+             switch (res) {
+             | Result.Ok(jsonState) =>
+               switch (jsonState->Js.Null.toOption) {
+               | Some(jsonState) =>
+                 switch (Js.Json.parseExn(jsonState)) {
+                 | state =>
+                   setInitialState(_ => Some(Some(state)));
+                 | exception _ =>
+                   Js.log2(
+                     "Restoring Navigation State: unable to decode valid json",
+                     jsonState,
+                   );
+                   setInitialState(_ => Some(None));
+                 }
+               | None => setInitialState(_ => Some(None))
+               };
+             | Result.Error(e) =>
+               Js.log2(
+                 "Restoring Navigation State: unable to get json state",
+                 e,
+               );
+               setInitialState(_ => Some(None));
+             };
+           })
+         ->ignore;
+       };
+       None;
+     },
+     [|initialStateContainer|],
+   );
+
+   let isReady = initialStateContainer->Option.isSome;
+   <>
+       {initialStateContainer
+        ->Option.map(initialState =>
+            <Native.NavigationNativeContainer
+              ?initialState
+              onStateChange={state => {
+                let maybeJsonState = Js.Json.stringifyAny(state);
+                switch (maybeJsonState) {
+                | Some(jsonState) =>
+                  AsyncStorage.setItem(navigationStateStorageKey, jsonState)
+                  ->ignore
+                | None => Js.log("Unable to stringify navigation state")
+                };
+              }}>
+              <RootNavigator />
+            </Native.NavigationNativeContainer>
+          )
+        ->Option.getWithDefault(React.null)}
+       <Bootsplash isReady />
+   </>;
+ };
+ ```
+ */
+
 module NavigationNativeContainer = {
-  //TODO
-  type initialState;
-  type navigationState;
+  type state = Js.Json.t;
+  type navigationState = state => unit;
 
   [@bs.module "@react-navigation/native"] [@react.component]
   external make:
     (
-      ~initialState: initialState=?,
+      ~initialState: state=?,
       ~onStateChange: navigationState=?,
       ~children: React.element
     ) =>