feat: Add durable object for Anilist requests (#2)

This commit introduces a durable object to handle Anilist GraphQL requests, with the goal of preventing request duplication.

The durable object is designed to cache responses from the Anilist API, with a TTL based on the `nextAiringEpisode` field in the response.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

src/libs/anilist/anilist-do.ts

@@ -0,0 +1,104 @@
+import { DurableObject, env } from "cloudflare:workers";
+import { GraphQLClient } from "graphql-request";
+import { z } from "zod";
+
+import { GetTitleQuery, _fetchTitleFromAnilist } from "~/libs/anilist/getTitle";
+import { sleep } from "~/libs/sleep.ts";
+import type { Title } from "~/types/title";
+
+const nextAiringEpisodeSchema = z.nullable(
+  z.object({
+    episode: z.number().int(),
+    airingAt: z.number().int(),
+    timeUntilAiring: z.number().int(),
+  }),
+);
+
+export class AnilistDurableObject extends DurableObject {
+  state: DurableObjectState;
+
+  constructor(state: DurableObjectState) {
+    super(state, env);
+    this.state = state;
+  }
+
+  async fetch(request: Request) {
+    const body = await request.json();
+    const { operationName } = body;
+
+    switch (operationName) {
+      case "GetTitle": {
+        const { variables } = body;
+        const cache = await this.state.storage.get(variables.id);
+        if (cache) {
+          return new Response(JSON.stringify(cache), {
+            headers: { "Content-Type": "application/json" },
+          });
+        }
+
+        const anilistResponse = await this.fetchTitleFromAnilist(
+          variables.id,
+          variables.token,
+        );
+        const nextAiringEpisode = nextAiringEpisodeSchema.parse(
+          anilistResponse?.nextAiringEpisode,
+        );
+
+        const airingAt = (nextAiringEpisode?.airingAt ?? 0) * 1000;
+        await this.state.storage.put(variables.id, anilistResponse);
+        if (airingAt) {
+          await this.state.storage.setAlarm(airingAt);
+          await this.state.storage.put(`alarm:${variables.id}`, airingAt);
+        }
+
+        return new Response(JSON.stringify(anilistResponse), {
+          headers: { "Content-Type": "application/json" },
+        });
+      }
+      default:
+        return new Response("Not found", { status: 404 });
+    }
+  }
+
+  async alarm() {
+    const now = Date.now();
+    const alarms = await this.state.storage.list({ prefix: "alarm:" });
+    console.log("alarm", now, alarms);
+    for (const [id, ttl] of Object.entries(alarms)) {
+      if (now >= ttl) {
+        await this.state.storage.delete(id);
+      }
+    }
+  }
+
+  async fetchTitleFromAnilist(
+    id: number,
+    token?: string | undefined,
+  ): Promise<Title | undefined> {
+    const client = new GraphQLClient("https://graphql.anilist.co/");
+    const headers = new Headers();
+    if (token) {
+      headers.append("Authorization", `Bearer ${token}`);
+    }
+
+    return client
+      .request(GetTitleQuery, { id }, headers)
+      .then((data) => data?.Media ?? undefined)
+      .catch((error) => {
+        if (error.message.includes("Not Found")) {
+          return undefined;
+        }
+        if (error.response?.status === 429) {
+          console.log(
+            "429, retrying in",
+            error.response.headers.get("Retry-After"),
+          );
+          return sleep(
+            Number(error.response.headers.get("Retry-After")!) * 1000,
+          ).then(() => this.fetchTitleFromAnilist(id, token));
+        }
+
+        throw error;
+      });
+  }
+}