Initial commit

frontend/api.ts

@@ -0,0 +1,69 @@
+import type { Data } from '../shared/types';
+
+export class UnauthorizedError extends Error {
+  constructor() {
+    super('Not logged in');
+  }
+}
+
+export class ApiError extends Error {
+  constructor(
+    public status: number,
+    message: string,
+  ) {
+    super(message);
+  }
+}
+
+async function send(method: string, url: string, body?: unknown, headers: Record<string, string> = {}) {
+  return fetch(url, {
+    method,
+    credentials: 'same-origin',
+    headers: body === undefined ? headers : { 'Content-Type': 'application/json', ...headers },
+    body: body === undefined ? undefined : JSON.stringify(body),
+  });
+}
+
+async function request<T>(method: string, url: string, body?: unknown): Promise<T> {
+  const r = await send(method, url, body);
+  if (r.status === 401 && url !== '/api/login') throw new UnauthorizedError();
+  if (!r.ok) {
+    const err = (await r.json().catch(() => ({}))) as { error?: string };
+    throw new ApiError(r.status, err.error ?? `HTTP ${r.status}`);
+  }
+  return r.status === 204 ? (undefined as T) : ((await r.json()) as T);
+}
+
+export const api = {
+  session: () => request<{ username: string }>('GET', '/api/session'),
+  login: (username: string, password: string) =>
+    request<{ username: string }>('POST', '/api/login', { username, password }),
+  logout: () => request<void>('POST', '/api/logout', {}),
+  registration: () => request<{ open: boolean; inviteRequired: boolean }>('GET', '/api/registration'),
+  register: (username: string, password: string, inviteCode?: string) =>
+    request<{ username: string }>('POST', '/api/register', { username, password, inviteCode }),
+  deleteAccount: (password: string) => request<void>('DELETE', '/api/account', { password }),
+  /** The data plus its version tag, needed to save. */
+  load: async (): Promise<Versioned> => {
+    const r = await send('GET', '/api/data');
+    if (r.status === 401) throw new UnauthorizedError();
+    if (!r.ok) throw new ApiError(r.status, `HTTP ${r.status}`);
+    return { data: (await r.json()) as Data, etag: r.headers.get('ETag') ?? '' };
+  },
+  /**
+   * Saves `data` if the server still has version `etag`. Otherwise resolves to the
+   * server's newer version (`conflict`) so the caller can merge and retry.
+   */
+  save: async (data: Data, etag: string): Promise<{ etag: string } | { conflict: Versioned }> => {
+    const r = await send('PUT', '/api/data', data, { 'If-Match': etag });
+    if (r.status === 401) throw new UnauthorizedError();
+    if (r.status === 412) return { conflict: { data: (await r.json()) as Data, etag: r.headers.get('ETag') ?? '' } };
+    if (!r.ok) throw new ApiError(r.status, `HTTP ${r.status}`);
+    return { etag: r.headers.get('ETag') ?? '' };
+  },
+};
+
+export interface Versioned {
+  data: Data;
+  etag: string;
+}