From 87980bbba1fbe7b3f7208dee4dc5d4058a75a944 Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Wed, 15 Nov 2023 16:22:57 -0600
Subject: [PATCH] Add an SqliteWorker

---
 src/workers.ts               |  5 +++++
 src/workers/sqlite.ts        | 37 ++++++++++++++++++++++++++++++++++++
 src/workers/sqlite.worker.ts | 32 +++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+)
 create mode 100644 src/workers.ts
 create mode 100644 src/workers/sqlite.ts
 create mode 100644 src/workers/sqlite.worker.ts

diff --git a/src/workers.ts b/src/workers.ts
new file mode 100644
index 0000000..f00c43a
--- /dev/null
+++ b/src/workers.ts
@@ -0,0 +1,5 @@
+import SqliteWorker from './workers/sqlite.ts';
+
+const sqliteWorker = new SqliteWorker('./data/db.sqlite3');
+
+export { sqliteWorker };
\ No newline at end of file
diff --git a/src/workers/sqlite.ts b/src/workers/sqlite.ts
new file mode 100644
index 0000000..aaab650
--- /dev/null
+++ b/src/workers/sqlite.ts
@@ -0,0 +1,37 @@
+class SqliteWorker {
+  #path: string;
+  #worker: Worker;
+
+  constructor(path: string) {
+    this.#path = path;
+    this.#worker = new Worker(new URL('./sqlite.worker.ts', import.meta.url).href, { type: 'module' });
+  }
+
+  open(): Promise<void> {
+    return this.#call(['open', [this.#path]]);
+  }
+
+  query(sql: string, params?: any): Promise<unknown[]> {
+    return this.#call(['query', [sql, params]]);
+  }
+
+  #call<T>(msg: [string, unknown[]]): Promise<T> {
+    const id = crypto.randomUUID();
+
+    this.#worker.postMessage([id, msg]);
+
+    // TODO: use a hashmap instead of an event listener for better performance.
+    return new Promise((resolve) => {
+      const handleEvent = (event: MessageEvent<[string, T]>) => {
+        const [_id, result] = event.data;
+        if (_id === id) {
+          this.#worker.removeEventListener('message', handleEvent);
+          resolve(result);
+        }
+      };
+      this.#worker.addEventListener('message', handleEvent);
+    });
+  }
+}
+
+export default SqliteWorker;
diff --git a/src/workers/sqlite.worker.ts b/src/workers/sqlite.worker.ts
new file mode 100644
index 0000000..ea024dc
--- /dev/null
+++ b/src/workers/sqlite.worker.ts
@@ -0,0 +1,32 @@
+/// <reference lib="webworker" />
+
+import { DenoSqlite3 } from '@/deps.ts';
+
+let db: DenoSqlite3;
+
+type Msg =
+  | ['open', [string]]
+  | ['query', [string, unknown[]]];
+
+function call([cmd, args]: Msg) {
+  switch(cmd) {
+    case 'open':
+      return handleOpen(args[0]);
+    case 'query':
+      return handleQuery(args[0], args[1]);
+  }
+}
+
+function handleOpen(path: string): void {
+  db = new DenoSqlite3(path);
+}
+
+function handleQuery(sql: string, params: any[] = []) {
+  return db.prepare(sql).all(...params);
+}
+
+self.addEventListener('message', (event: MessageEvent<[string, Msg]>) => {
+  const [id, msg] = event.data;
+  const result = call(msg);
+  self.postMessage([id, result]);
+});
\ No newline at end of file