feat: support removing watch status when null

A user can choose to remove a show from being in their media list completely, by setting the watch status to null

src/controllers/watch-status/anilist.ts

@@ -1,9 +1,10 @@
 import { graphql } from "gql.tada";
 import { GraphQLClient } from "graphql-request";
 
-import type { WatchStatus } from "~/types/title";
+import { AnilistTitleNotFoundError } from "~/libs/errors/TitleNotFound";
+import type { WatchStatus } from "~/types/title/watchStatus";
 
-const UpdateWatchStatusQuery = graphql(`
+const UpdateWatchStatusMutation = graphql(`
   mutation UpdateWatchStatus($titleId: Int!, $watchStatus: MediaListStatus!) {
     SaveMediaListEntry(mediaId: $titleId, status: $watchStatus) {
       id
@@ -11,20 +12,60 @@ const UpdateWatchStatusQuery = graphql(`
   }
 `);
 
-/** Updates the watch status for a title on Anilist. If the token is null, the watch status will not be updated. */
+const GetMediaListEntryQuery = graphql(`
+  query GetMediaListEntry($titleId: Int!) {
+    Media(id: $titleId) {
+      mediaListEntry {
+        id
+      }
+    }
+  }
+`);
+
+const DeleteMediaListEntryMutation = graphql(`
+  mutation DeleteMediaListEntry($entryId: Int!) {
+    DeleteMediaListEntry(id: $entryId) {
+      deleted
+    }
+  }
+`);
+
+/** Updates the watch status for a title on Anilist. If the token is null, the watch status will not be updated.
+ *
+ * @returns true if the watch status was updated or if the token was null, false if it was not
+ */
 export async function maybeUpdateWatchStatusOnAnilist(
   titleId: number,
-  watchStatus: WatchStatus,
+  watchStatus: WatchStatus | null,
   aniListToken: string | undefined,
 ) {
   if (!aniListToken) {
-    return;
+    return true;
   }
 
   const client = new GraphQLClient("https://graphql.anilist.co/");
   const headers = new Headers({ Authorization: `Bearer ${aniListToken}` });
 
+  if (!watchStatus) {
+    return client
+      .request(GetMediaListEntryQuery, { titleId }, headers)
+      .then((data) => data?.Media?.mediaListEntry?.id)
+      .then((mediaListEntryId) => {
+        if (!mediaListEntryId) {
+          throw new AnilistTitleNotFoundError();
+        }
+
+        return client
+          .request(
+            DeleteMediaListEntryMutation,
+            { entryId: mediaListEntryId },
+            headers,
+          )
+          .then((data) => !!data?.DeleteMediaListEntry?.deleted);
+      });
+  }
+
   return client
-    .request(UpdateWatchStatusQuery, { titleId, watchStatus }, headers)
+    .request(UpdateWatchStatusMutation, { titleId, watchStatus }, headers)
     .then((data) => !!data?.SaveMediaListEntry?.id);
 }