Documentation added ingame (#667)

src/ui/React/Documentation.tsx

@@ -0,0 +1,71 @@
+import React, { useContext, useState } from "react";
+
+interface Navigator {
+  navigate: (s: string, external: boolean) => void;
+}
+
+export const Navigator = React.createContext<Navigator>({ navigate: () => undefined });
+
+export const useNavigator = (): Navigator => useContext(Navigator);
+
+interface History {
+  pages: string[];
+  page: string;
+  push(p: string): void;
+  pop(): void;
+  home(): void;
+}
+
+const defaultPage = "index.md";
+
+const HistoryContext = React.createContext<History>({
+  page: "",
+  pages: [],
+  push: () => undefined,
+  pop: () => undefined,
+  home: () => undefined,
+});
+
+export const Provider = HistoryContext.Provider;
+export const useHistory = (): History => useContext(HistoryContext);
+
+const onPush = (h: History, p: string): History => {
+  return {
+    ...h,
+    page: p,
+    pages: [...h.pages, h.page],
+  };
+};
+
+const onPop = (h: History): History => {
+  const page = h.pages.pop() ?? defaultPage;
+  return {
+    ...h,
+    page: page,
+  };
+};
+
+const onHome = (h: History): History => {
+  return {
+    ...h,
+    page: defaultPage,
+    pages: [],
+  };
+};
+
+export const HistoryProvider = (props: React.PropsWithChildren<object>): React.ReactElement => {
+  const [history, setHistory] = useState<History>({
+    page: defaultPage,
+    pages: [],
+    push(p: string) {
+      setHistory((h) => onPush(h, p));
+    },
+    pop() {
+      setHistory((h) => onPop(h));
+    },
+    home() {
+      setHistory((h) => onHome(h));
+    },
+  });
+  return <Provider value={history}>{props.children}</Provider>;
+};