1 files changed, 86 insertions, 0 deletions

diff --git a/src/services/postDatabase.ts b/src/services/postDatabase.ts
new file mode 100644
index 0000000..e3be7bb
--- /dev/null
+++ b/src/services/postDatabase.ts
@@ -0,0 +1,86 @@
+import fs from "fs/promises";
+import path from "path";
+import * as f from "fp-ts";
+import * as t from "io-ts";
+
+export const PostDatabaseEntryC = t.type({
+    provider: t.literal("e926"),
+    id: t.number,
+});
+
+export type PostDatabaseEntry = t.TypeOf<typeof PostDatabaseEntryC>;
+
+export class PostDatabase {
+    private entries: PostDatabaseEntry[] = [];
+
+    private readonly filePath: string;
+
+    private isLoaded = false;
+
+    constructor(filename: string, private max?: number) {
+        this.filePath = path.join(process.cwd(), filename);
+    }
+
+    private async load() {
+        if (this.isLoaded) {
+            return;
+        }
+
+        try {
+            await fs.stat(this.filePath);
+        } catch {
+            await this.save();
+        }
+
+        const fileContent = await fs.readFile(this.filePath, "utf8");
+        const entries = t.array(PostDatabaseEntryC).decode(fileContent);
+
+        if (f.either.isRight(entries)) {
+            this.entries = this.max ? entries.right.slice(0, -1 * this.max) : entries.right;
+        }
+    }
+
+    private async save() {
+        await fs.writeFile(this.filePath, JSON.stringify(this.entries), "utf8");
+    }
+
+    async insertIfNotExists(entry: PostDatabaseEntry): Promise<boolean> {
+        await this.load();
+
+        const has = !!this.entries.find((e) => e.provider === entry.provider && e.id === entry.id);
+
+        if (!has) {
+            this.entries.push(entry);
+            await this.save();
+        }
+
+        return has;
+    }
+
+    async takeFirst(): Promise<PostDatabaseEntry | undefined> {
+        await this.load();
+        const entry = this.entries.shift();
+        await this.save();
+        return entry;
+    }
+
+    async remove(entry: PostDatabaseEntry): Promise<boolean> {
+        await this.load();
+        const i = this.entries.findIndex((e) => e.provider === entry.provider && e.id === entry.id);
+
+        if (i === -1) {
+            return false;
+        }
+
+        this.entries.splice(i, 1);
+        await this.save();
+        return true;
+    }
+
+    async getCount() {
+        await this.load();
+        return this.entries.length;
+    }
+}
+
+export default PostDatabase;