Add DittoSQLite module

src/db/adapters/DittoSQLite.ts

@@ -0,0 +1,52 @@
+import { Conf } from '@/config.ts';
+import { DittoTables } from '@/db/DittoTables.ts';
+import { Kysely, PolySqliteDialect } from '@/deps.ts';
+import { setPragma } from '@/pragma.ts';
+import SqliteWorker from '@/workers/sqlite.ts';
+
+export class DittoSQLite {
+  static db: Kysely<DittoTables> | undefined;
+
+  static async getInstance(): Promise<Kysely<DittoTables>> {
+    if (!this.db) {
+      const sqliteWorker = new SqliteWorker();
+      await sqliteWorker.open(this.path);
+
+      this.db = new Kysely<DittoTables>({
+        dialect: new PolySqliteDialect({
+          database: sqliteWorker,
+        }),
+      });
+
+      // Set PRAGMA values.
+      await Promise.all([
+        setPragma(this.db, 'synchronous', 'normal'),
+        setPragma(this.db, 'temp_store', 'memory'),
+        setPragma(this.db, 'mmap_size', Conf.sqlite.mmapSize),
+      ]);
+    }
+    return this.db;
+  }
+
+  /** Get the relative or absolute path based on the `DATABASE_URL`. */
+  static get path() {
+    if (Deno.env.get('DATABASE_URL') === 'sqlite://:memory:') {
+      return ':memory:';
+    }
+
+    const { host, pathname } = Conf.databaseUrl;
+
+    if (!pathname) return '';
+
+    // Get relative path.
+    if (host === '') {
+      return pathname;
+    } else if (host === '.') {
+      return pathname;
+    } else if (host) {
+      return host + pathname;
+    }
+
+    return '';
+  }
+}