JS error handling

web/src/app/errors.js

@@ -0,0 +1,66 @@
+// This is a subset of, and the counterpart to errors.go
+
+export const fetchOrThrow = async (url, options) => {
+    const response = await fetch(url, options);
+    if (response.status !== 200) {
+        await throwAppError(response);
+    }
+    return response; // Promise!
+};
+
+export const throwAppError = async (response) => {
+    if (response.status === 401 || response.status === 403) {
+        console.log(`[Error] HTTP ${response.status}`, response);
+        throw new UnauthorizedError();
+    }
+    const error = await maybeToJson(response);
+    if (error?.code) {
+        console.log(`[Error] HTTP ${response.status}, ntfy error ${error.code}: ${error.error || ""}`, response);
+        if (error.code === UserExistsError.CODE) {
+            throw new UserExistsError();
+        } else if (error.code === TopicReservedError.CODE) {
+            throw new TopicReservedError();
+        } else if (error.code === AccountCreateLimitReachedError.CODE) {
+            throw new AccountCreateLimitReachedError();
+        } else if (error.code === IncorrectPasswordError.CODE) {
+            throw new IncorrectPasswordError();
+        } else if (error?.error) {
+            throw new Error(`Error ${error.code}: ${error.error}`);
+        }
+    }
+    console.log(`[Error] HTTP ${response.status}, not a ntfy error`, response);
+    throw new Error(`Unexpected response ${response.status}`);
+};
+
+const maybeToJson = async (response) => {
+    try {
+        return await response.json();
+    } catch (e) {
+        return null;
+    }
+}
+
+export class UnauthorizedError extends Error {
+    constructor() { super("Unauthorized"); }
+}
+
+export class UserExistsError extends Error {
+    static CODE = 40901; // errHTTPConflictUserExists
+    constructor() { super("Username already exists"); }
+}
+
+export class TopicReservedError extends Error {
+    static CODE = 40902; // errHTTPConflictTopicReserved
+    constructor() { super("Topic already reserved"); }
+}
+
+export class AccountCreateLimitReachedError extends Error {
+    static CODE = 42906; // errHTTPTooManyRequestsLimitAccountCreation
+    constructor() { super("Account creation limit reached"); }
+}
+
+export class IncorrectPasswordError extends Error {
+    static CODE = 40026; // errHTTPBadRequestIncorrectPasswordConfirmation
+    constructor() { super("Password incorrect"); }
+}
+