feat: allow linking fediverse account to existing user

frontend/src/routes/settings/+layout.svelte

@@ -35,7 +35,14 @@
         <ListGroupItem tag="a" active={$page.url.pathname === "/settings"} href="/settings">
           Your profile
         </ListGroupItem>
-        {#if data.require_invite}
+        <ListGroupItem
+          tag="a"
+          active={$page.url.pathname === "/settings/auth"}
+          href="/settings/auth"
+        >
+          Authentication
+        </ListGroupItem>
+        {#if data.invitesEnabled}
           <ListGroupItem
             tag="a"
             active={$page.url.pathname === "/settings/invites"}

frontend/src/routes/settings/+layout.ts

@@ -1,8 +1,36 @@
+import {
+  ErrorCode,
+  type APIError,
+  type Invite,
+  type MeUser,
+  type PartialMember,
+} from "$lib/api/entities";
+import { apiFetchClient } from "$lib/api/fetch";
 import type { LayoutLoad } from "./$types";
 
 export const ssr = false;
 
 export const load = (async ({ parent }) => {
+  const user = await apiFetchClient<MeUser>("/users/@me");
+  const members = await apiFetchClient<PartialMember[]>("/users/@me/members");
+
+  let invites: Invite[] = [];
+  let invitesEnabled = true;
+  try {
+    invites = await apiFetchClient<Invite[]>("/auth/invites");
+  } catch (e) {
+    if ((e as APIError).code === ErrorCode.InvitesDisabled) {
+      invitesEnabled = false;
+    }
+  }
+
   const data = await parent();
-  return data;
+
+  return {
+    ...data,
+    user,
+    members,
+    invites,
+    invitesEnabled,
+  };
 }) satisfies LayoutLoad;

frontend/src/routes/settings/+page.ts

@@ -1,30 +0,0 @@
-import {
-  type Invite,
-  type APIError,
-  type MeUser,
-  type PartialMember,
-  ErrorCode,
-} from "$lib/api/entities";
-import { apiFetchClient } from "$lib/api/fetch";
-import { error } from "@sveltejs/kit";
-
-export const load = async () => {
-  try {
-    const user = await apiFetchClient<MeUser>("/users/@me");
-    const members = await apiFetchClient<PartialMember[]>("/users/@me/members");
-
-    let invites: Invite[] = [];
-    let invitesEnabled = true;
-    try {
-      invites = await apiFetchClient<Invite[]>("/auth/invites");
-    } catch (e) {
-      if ((e as APIError).code === ErrorCode.InvitesDisabled) {
-        invitesEnabled = false;
-      }
-    }
-
-    return { user, members, invites, invitesEnabled };
-  } catch (e) {
-    throw error(500, (e as APIError).message);
-  }
-};

frontend/src/routes/settings/auth/+page.svelte

@@ -0,0 +1,115 @@
+<script lang="ts">
+  import type { APIError } from "$lib/api/entities";
+  import { apiFetch } from "$lib/api/fetch";
+  import ErrorAlert from "$lib/components/ErrorAlert.svelte";
+  import {
+    Button,
+    Card,
+    CardBody,
+    CardText,
+    CardTitle,
+    Input,
+    Modal,
+    ModalBody,
+    ModalFooter,
+  } from "sveltestrap";
+  import type { PageData } from "./$types";
+
+  export let data: PageData;
+
+  let canUnlink = false;
+
+  $: canUnlink =
+    [data.user.discord, data.user.fediverse]
+      .map<number>((entry) => (entry === null ? 0 : 1))
+      .reduce((prev, current) => prev + current) >= 2;
+
+  let error: APIError | null = null;
+  let instance = "";
+  let fediDisabled = false;
+
+  let fediLinkModalOpen = false;
+  let toggleFediLinkModal = () => (fediLinkModalOpen = !fediLinkModalOpen);
+
+  const fediLogin = async () => {
+    fediDisabled = true;
+    try {
+      const resp = await apiFetch<{ url: string }>(
+        `/auth/urls/fediverse?instance=${encodeURIComponent(instance)}`,
+        {},
+      );
+      window.location.assign(resp.url);
+    } catch (e) {
+      error = e as APIError;
+    } finally {
+      fediDisabled = false;
+    }
+  };
+</script>
+
+<div>
+  <h1>Authentication providers</h1>
+
+  <div>
+    <div class="my-2">
+      <Card>
+        <CardBody>
+          <CardTitle>Fediverse</CardTitle>
+          <CardText>
+            {#if data.user.fediverse}
+              Your currently linked Fediverse account is <b
+                >{data.user.fediverse_username}@{data.user.fediverse_instance}</b
+              >
+              (<code>{data.user.fediverse}</code>).
+            {:else}
+              You do not have a linked Fediverse account.
+            {/if}
+          </CardText>
+          {#if data.user.fediverse}
+            <Button color="danger" disabled={!canUnlink}>Unlink account</Button>
+          {:else}
+            <Button color="secondary" on:click={toggleFediLinkModal}>Link account</Button>
+          {/if}
+        </CardBody>
+      </Card>
+    </div>
+    <div class="my-2">
+      <Card>
+        <CardBody>
+          <CardTitle>Discord</CardTitle>
+          <CardText>
+            {#if data.user.discord}
+              Your currently linked Discord account is <b>{data.user.discord_username}</b>
+              (<code>{data.user.discord}</code>).
+            {:else}
+              You do not have a linked Discord account.
+            {/if}
+          </CardText>
+          {#if data.user.discord}
+            <Button color="danger" disabled={!canUnlink}>Unlink account</Button>
+          {:else}
+            <Button color="secondary" href={data.urls.discord}>Link account</Button>
+          {/if}
+        </CardBody>
+      </Card>
+    </div>
+    <Modal header="Pick an instance" isOpen={fediLinkModalOpen} toggle={toggleFediLinkModal}>
+      <ModalBody>
+        <p>
+          <strong>Note:</strong> Misskey (and derivatives) are not supported yet, sorry.
+        </p>
+        <Input placeholder="Instance (e.g. mastodon.social)" bind:value={instance} />
+        {#if error}
+          <div class="mt-2">
+            <ErrorAlert {error} />
+          </div>
+        {/if}
+      </ModalBody>
+      <ModalFooter>
+        <Button color="primary" disabled={fediDisabled || instance === ""} on:click={fediLogin}
+          >Log in</Button
+        >
+      </ModalFooter>
+    </Modal>
+  </div>
+</div>

frontend/src/routes/settings/auth/+page.ts

@@ -0,0 +1,17 @@
+import { PUBLIC_BASE_URL } from "$env/static/public";
+import { apiFetch } from "$lib/api/fetch";
+
+export const load = async () => {
+  const resp = await apiFetch<UrlsResponse>("/auth/urls", {
+    method: "POST",
+    body: {
+      callback_domain: PUBLIC_BASE_URL,
+    },
+  });
+
+  return { urls: resp };
+};
+
+interface UrlsResponse {
+  discord: string;
+}

frontend/src/routes/settings/invites/+page.ts

@@ -1,25 +0,0 @@
-import { ErrorCode, type APIError, type Invite } from "$lib/api/entities";
-import { apiFetchClient } from "$lib/api/fetch";
-import { error } from "@sveltejs/kit";
-import type { PageLoad } from "../$types";
-
-export const load = (async () => {
-  const data = {
-    invitesEnabled: true,
-    invites: [] as Invite[],
-  };
-
-  try {
-    const invites = await apiFetchClient<Invite[]>("/auth/invites");
-    data.invites = invites;
-  } catch (e) {
-    if ((e as APIError).code === ErrorCode.InvitesDisabled) {
-      data.invitesEnabled = false;
-      data.invites = [];
-    } else {
-      throw error((e as APIError).code, (e as APIError).message);
-    }
-  }
-
-  return data;
-}) satisfies PageLoad;