add user concept and add todos for exercise

public/util.ts

@@ -11,7 +11,13 @@ const operations = [
     endpoint: "/api/logout",
     method: "POST",
     fields: {},
-  }
+  },
+  {
+    name: "Register",
+    endpoint: "/api/register",
+    method: "POST",
+    fields: { username: "input" },
+  },
 ];
 
 const API_URL = "http://localhost:3000";

src/app.ts

@@ -1,4 +1,6 @@
+import UserConcept from "./concepts/user";
 import WebSessionConcept from "./concepts/websession";
 
 // App Definition using concepts. Right now, we only have our WebSession concept implemented.
-export const WebSession = new WebSessionConcept();
+export const WebSession = new WebSessionConcept();
+export const User = new UserConcept();

src/concepts/user.ts

@@ -0,0 +1,23 @@
+import { NotAllowedError } from "./errors";
+
+export interface UserDoc {
+  username: string;
+}
+
+export default class UserConcept {
+  // Hardcoded users just for recitation purposes
+  public readonly users: UserDoc[] = [{ username: "testAccount" }, { username: "grace" }];
+
+  register(username: string) {
+    this.isUsernameAvailable(username);
+    this.users.push({ username });
+  }
+
+  isUsernameAvailable(username: string) {
+    if (this.users.filter((user) => user.username === username).length !== 0) {
+      throw new NotAllowedError("Username already taken!");
+    }
+  }
+
+  // TODO: Write code to make sure the username exists
+}

src/concepts/websession.ts

@@ -1,5 +1,5 @@
 // This is (some of) the code for the WebSession concept which was introduced in lecture on 9/18.
-// We're storing the user (in the form of the username string for now) when the user logs in, and we 
+// We're storing the user (in the form of the username string for now) when the user logs in, and we
 // reset the session's user when the user logs out.
 
 import { SessionData } from "express-session";
@@ -28,6 +28,8 @@ export default class WebSessionConcept {
     // Hint: Take a look at how the "end" function makes sure the user is logged in. Keep in mind that a
     // synchronization like starting a session should just consist of a series of actions that may throw
     // exceptions and should not have its own control flow.
+
+    // TODO: make sure user is registered before trying to log the user in
     session.user = username;
   }
 

src/routes.ts

@@ -1,6 +1,6 @@
 import { Router, getExpressRouter } from "./framework/router";
 
-import { WebSession } from "./app";
+import { User, WebSession } from "./app";
 import { WebSessionDoc } from "./concepts/websession";
 
 class Routes {
@@ -16,6 +16,12 @@ class Routes {
     return { msg: "Logged out!" };
   }
 
+  @Router.post("/register")
+  async register(username: string) {
+    User.register(username);
+    return { msg: "Username registered!", user: username };
+  }
+
   // If we had more concepts working, we'd add routes for those here too!
 }