Adds a routing

src/App.re

@@ -1,7 +1,92 @@
+type route =
+  | EAFunds
+  | GlobalCatastrophe
+  | Home
+  | NotFound;
+
+let routeToPath = route =>
+  switch (route) {
+  | EAFunds => "/ea-funds"
+  | GlobalCatastrophe => "/global-catastrophe"
+  | Home => "/"
+  | _ => "/"
+  };
+
+module Menu = {
+  module Styles = {
+    open Css;
+    let menu =
+      style([
+        position(`relative),
+        marginTop(em(0.25)),
+        marginBottom(em(0.25)),
+        selector(
+          "a",
+          [
+            borderRadius(em(0.25)),
+            display(`inlineBlock),
+            backgroundColor(`hex("eee")),
+            padding(em(1.)),
+            cursor(`pointer),
+          ],
+        ),
+        selector("a:hover", [backgroundColor(`hex("bfcad4"))]),
+        selector("a:hover", [backgroundColor(`hex("bfcad4"))]),
+        selector(
+          "a:not(:first-child):not(:last-child)",
+          [marginRight(em(0.25)), marginLeft(em(0.25))],
+        ),
+      ]);
+  };
+
+  module Item = {
+    [@react.component]
+    let make = (~href, ~children) => {
+      <a
+        href
+        onClick={e => {
+          e->ReactEvent.Synthetic.preventDefault;
+          ReasonReactRouter.push(href);
+        }}>
+        children
+      </a>;
+    };
+  };
+
   [@react.component]
   let make = () => {
-  <div className="w-full max-w-screen-xl mx-auto px-6">
-    <FormBuilder.ModelForm model=EAFunds.Interface.model />
-    <FormBuilder.ModelForm model=GlobalCatastrophe.Interface.model />
+    <div className=Styles.menu>
+      <Item href={routeToPath(Home)} key="home"> {"Home" |> E.ste} </Item>
+      <Item href={routeToPath(EAFunds)} key="ea-funds">
+        {"EA Funds" |> E.ste}
+      </Item>
+      <Item href={routeToPath(GlobalCatastrophe)} key="gc">
+        {"Global Catastrophe" |> E.ste}
+      </Item>
+    </div>;
+  };
+};
+
+[@react.component]
+let make = () => {
+  let url = ReasonReactRouter.useUrl();
+
+  let routing =
+    switch (url.path) {
+    | ["ea-funds"] => EAFunds
+    | ["global-catastrophe"] => GlobalCatastrophe
+    | [] => Home
+    | _ => NotFound
+    };
+
+  <div className="w-full max-w-screen-xl mx-auto px-6">
+    <Menu />
+    {switch (routing) {
+     | EAFunds => <FormBuilder.ModelForm model=EAFunds.Interface.model />
+     | GlobalCatastrophe =>
+       <FormBuilder.ModelForm model=GlobalCatastrophe.Interface.model />
+     | Home => <div> {"Welcome" |> E.ste} </div>
+     | _ => <div> {"Page is not found" |> E.ste} </div>
+     }}
   </div>;
 };

src/utility/E.re

@@ -297,3 +297,5 @@ module JsArray = {
        );
   let filter = Js.Array.filter;
 };
+
+let ste = React.string;