Initial setup for new frontend.

frontend/src/utils/Api.ts

@@ -0,0 +1,37 @@
+class Api {
+    private baseURL: string = import.meta.env.BASE_URL;
+    private apiPrefix = "api/";
+
+    constructor(apiPrefix?: string) {
+        if (apiPrefix) {
+            this.apiPrefix = apiPrefix;
+        }
+    }
+
+    private toURL(path: string): string {
+        return this.baseURL + this.apiPrefix + path;
+    }
+
+    async get<T>(path: string, isT: (arg: unknown) => arg is T): Promise<T> {
+        const url = this.toURL(path);
+        const result = await fetch(url);
+        const json = await result.json();
+
+        if (!isT(json)) {
+            console.log(json);
+            throw new Error(`API get result has wrong type. ${url} => ${json}`);
+        }
+
+        return json;
+    }
+}
+
+export const api = new Api();
+
+class InternalApi extends Api {
+    constructor() {
+        super("internal/api/");
+    }
+}
+
+export const internalApi = new InternalApi();