From 4b916dff471c6693bb118c24eb37c37b7ca3ca73 Mon Sep 17 00:00:00 2001
From: Abdullah Atta <abdullahatta@streetwriters.co>
Date: Sat, 10 Feb 2024 10:59:27 +0500
Subject: [PATCH] core: add support for nested transactions

---
 packages/core/src/api/index.ts         | 39 +++++++++++++++-----------
 packages/core/src/utils/queue-value.ts | 35 +++++++++++++++++++++++
 2 files changed, 57 insertions(+), 17 deletions(-)
 create mode 100644 packages/core/src/utils/queue-value.ts

diff --git a/packages/core/src/api/index.ts b/packages/core/src/api/index.ts
index 5df80bfb6..de5cdc909 100644
--- a/packages/core/src/api/index.ts
+++ b/packages/core/src/api/index.ts
@@ -71,6 +71,7 @@ import { Kysely, Transaction, sql } from "kysely";
 import { CachedCollection } from "../database/cached-collection";
 import { Vaults } from "../collections/vaults";
 import { KVStorage } from "../database/kv";
+import { QueueValue } from "../utils/queue-value";
 
 type EventSourceConstructor = new (
   uri: string,
@@ -126,7 +127,7 @@ class Database {
 
   private _sql?: Kysely<DatabaseSchema>;
   sql: DatabaseAccessor = () => {
-    if (this._transaction) return this._transaction;
+    if (this._transaction) return this._transaction.value;
 
     if (!this._sql)
       throw new Error(
@@ -138,23 +139,27 @@ class Database {
   private _kv?: KVStorage;
   kv: KVStorageAccessor = () => this._kv || new KVStorage(this.sql);
 
-  private _transaction?: Transaction<DatabaseSchema>;
-  private transactionMutex = new Mutex();
-  transaction = (
-    executor: (tr: Transaction<DatabaseSchema>) => void | Promise<void>
+  private _transaction?: QueueValue<Transaction<DatabaseSchema>>;
+  transaction = async (
+    executor: (tr: Transaction<DatabaseSchema>) => Promise<void>
   ) => {
-    return this.transactionMutex.runExclusive(() =>
-      this.sql()
-        .transaction()
-        .execute(async (tr) => {
-          this._transaction = tr;
-          await executor(tr);
-          this._transaction = undefined;
-        })
-        .finally(() => {
-          this._transaction = undefined;
-        })
-    );
+    if (this._transaction) {
+      await executor(this._transaction.use()).finally(() =>
+        this._transaction?.discard()
+      );
+      return;
+    }
+
+    return this.sql()
+      .transaction()
+      .execute(async (tr) => {
+        this._transaction = new QueueValue(
+          tr,
+          () => (this._transaction = undefined)
+        );
+        await executor(this._transaction.use());
+      })
+      .finally(() => this._transaction?.discard());
   };
 
   options!: Options;
diff --git a/packages/core/src/utils/queue-value.ts b/packages/core/src/utils/queue-value.ts
new file mode 100644
index 000000000..cd6658f95
--- /dev/null
+++ b/packages/core/src/utils/queue-value.ts
@@ -0,0 +1,35 @@
+/*
+This file is part of the Notesnook project (https://notesnook.com/)
+
+Copyright (C) 2023 Streetwriters (Private) Limited
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+export class QueueValue<T> {
+  #counter: number;
+  constructor(readonly value: T, private readonly destructor: () => void) {
+    this.#counter = 0;
+  }
+
+  use() {
+    this.#counter++;
+    return this.value;
+  }
+
+  discard() {
+    this.#counter--;
+    if (this.#counter === 0) this.destructor();
+  }
+}