Add preliminary TrendsDB module

src/deps.ts

@@ -39,3 +39,4 @@ export { default as sanitizeHtml } from 'npm:sanitize-html@^2.10.0';
 export { default as ISO6391 } from 'npm:iso-639-1@2.1.15';
 export { Dongoose } from 'https://raw.githubusercontent.com/alexgleason/dongoose/68b7ad9dd7b6ec0615e246a9f1603123c1709793/mod.ts';
 export { createPentagon } from 'https://deno.land/x/pentagon@v0.1.1/mod.ts';
+export { DB as Sqlite } from 'https://deno.land/x/sqlite@v3.7.0/mod.ts';

src/trends.ts

@@ -0,0 +1,46 @@
+import { Sqlite } from '@/deps.ts';
+
+class TrendsDB {
+  #db: Sqlite;
+
+  constructor(db: Sqlite) {
+    this.#db = db;
+
+    this.#db.execute(`
+      CREATE TABLE IF NOT EXISTS tag_usages (
+        tag TEXT NOT NULL,
+        pubkey8 TEXT NOT NULL,
+        inserted_at DATETIME NOT NULL,
+      );
+
+      CREATE INDEX IF NOT EXISTS idx_time_tag ON tag_usages(inserted_at, tag);
+    `);
+  }
+
+  getTrendingTags(): string[] {
+    return this.#db.query<string[]>(`
+      SELECT tag, COUNT(DISTINCT pubkey8)
+        FROM tag_usages
+        WHERE inserted_at >= $1 AND inserted_at < $2
+        GROUP BY tag
+        ORDER BY COUNT(DISTINCT pubkey8)
+        DESC LIMIT 10;
+    `).map((row) => row[0]);
+  }
+
+  addTagUsage(tag: string, pubkey8: string): void {
+    this.#db.query(
+      'INSERT INTO tag_usages (tag, pubkey8, inserted_at) VALUES (?, ?, ?)',
+      [tag, pubkey8, new Date()],
+    );
+  }
+
+  cleanupTagUsages(): void {
+    this.#db.query(
+      'DELETE FROM tag_usages WHERE inserted_at < ?',
+      [new Date(Date.now() - 1000 * 60 * 60 * 24 * 7)],
+    );
+  }
+}
+
+export { TrendsDB };