From 12ee614ef30f7218bbcf1f358ae097019ad7be19 Mon Sep 17 00:00:00 2001
From: Volpeon <git@volpeon.ink>
Date: Tue, 19 Oct 2021 08:59:42 +0200
Subject: Avoid duplicate posts

---
 src/api/e621/index.ts | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/src/api/e621/index.ts b/src/api/e621/index.ts
index 2fc0d2e..47d5dd1 100644
--- a/src/api/e621/index.ts
+++ b/src/api/e621/index.ts
@@ -1,5 +1,7 @@
 import got from "got";
 import config from "../../config";
+import fs from "fs/promises";
+import path from "path";
 
 export interface GetPostQuery {
     tags: readonly string[];
@@ -31,6 +33,35 @@ export const client = got.extend({
     },
 });
 
+const dedupePath = path.join(__dirname, "e926dedupe.json");
+const dedupeMax = 50;
+let dedupeDb: number[] | undefined;
+
+async function loadDedupeDb() {
+    if (dedupeDb) {
+        return;
+    }
+
+    try {
+        await fs.stat(dedupePath);
+    } catch {
+        await saveDedupeDb();
+    }
+
+    const d = await fs.readFile(dedupePath, "utf8");
+    const dd = JSON.parse(d);
+
+    if (dd instanceof Array) {
+        dedupeDb = dd.slice(0, -1 * dedupeMax);
+    } else {
+        dedupeDb = [];
+    }
+}
+
+async function saveDedupeDb() {
+    await fs.writeFile(dedupePath, JSON.stringify(dedupeDb ?? []), "utf8");
+}
+
 export async function getPostById(id: number) {
     const response = await client
         .get("https://e926.net/posts.json", {
@@ -48,6 +79,8 @@ export async function getPostById(id: number) {
 }
 
 export async function getRandomPost(query: GetPostQuery) {
+    await loadDedupeDb();
+
     const page = Math.floor(Math.random() * (query.maxPage - 1)) + 1;
 
     const response = await client
@@ -67,5 +100,12 @@ export async function getRandomPost(query: GetPostQuery) {
     const postIndex = Math.floor(Math.random() * response.posts.length);
     const post = response.posts[postIndex];
 
+    if (dedupeDb.includes(post.id)) {
+        return getRandomPost(query);
+    }
+
+    dedupeDb.push(post.id);
+    await saveDedupeDb();
+
     return post;
 }
-- 
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