[v6] Implement Realtime Database (#2195)

* [database] recreate database branch based off of #2185

* [database] cleanup linting issues

* [database] enable tests

* [database] add to tests deps

packages/database/lib/DatabaseTransaction.js

@@ -0,0 +1,176 @@
+/* eslint-disable no-console */
+/*
+ * Copyright (c) 2016-present Invertase Limited & Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this library except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+import NativeError from '@react-native-firebase/app/lib/internal/NativeFirebaseError';
+
+let transactionId = 0;
+
+/**
+ * Uses the push id generator to create a transaction id
+ * @returns {number}
+ * @private
+ */
+
+const generateTransactionId = () => transactionId++;
+
+export default class DatabaseTransaction {
+  constructor(database) {
+    this._database = database;
+    this._emitter = database.emitter;
+    this._transactions = {};
+
+    this._emitter.addListener(
+      this._database.eventNameForApp('database_transaction_event'),
+      this._onTransactionEvent.bind(this),
+    );
+  }
+
+  /**
+   *
+   * @param reference
+   * @param transactionUpdater
+   * @param onComplete
+   * @param applyLocally
+   */
+  add(reference, transactionUpdater, onComplete, applyLocally = false) {
+    const id = generateTransactionId();
+
+    this._transactions[id] = {
+      id,
+      reference,
+      transactionUpdater,
+      onComplete,
+      applyLocally,
+      completed: false,
+      started: true,
+    };
+
+    this._database.native.transactionStart(reference.path, id, applyLocally);
+  }
+
+  /**
+   * Returns a transaction by ID
+   *
+   * @param id
+   * @return {*}
+   * @private
+   */
+  _getTransaction(id) {
+    return this._transactions[id];
+  }
+
+  /**
+   * Removes a transaction by ID on the next event loop
+   *
+   * @param id
+   * @private
+   */
+  _removeTransaction(id) {
+    setImmediate(() => {
+      delete this._transactions[id];
+    });
+  }
+
+  /**
+   *
+   * @param event
+   * @private
+   */
+  _onTransactionEvent(event) {
+    switch (event.body.type) {
+      case 'update':
+        return this._handleUpdate(event);
+      case 'error':
+        return this._handleError(event);
+      case 'complete':
+        return this._handleComplete(event);
+      default:
+        return undefined;
+    }
+  }
+
+  /**
+   *
+   * @param event
+   * @private
+   */
+  _handleUpdate(event) {
+    let newValue;
+
+    const { id, body } = event;
+    const { value } = body;
+
+    try {
+      const transaction = this._getTransaction(id);
+      if (!transaction) return;
+      newValue = transaction.transactionUpdater(value);
+    } finally {
+      let abort = false;
+
+      if (newValue === undefined) {
+        abort = true;
+      }
+
+      this._database.native.transactionTryCommit(id, {
+        value: newValue,
+        abort,
+      });
+    }
+  }
+
+  /**
+   *
+   * @param event
+   * @private
+   */
+  _handleError(event) {
+    const transaction = this._getTransaction(event.id);
+
+    if (transaction && !transaction.completed) {
+      transaction.completed = true;
+
+      try {
+        // error, committed, snapshot
+        const error = NativeError.fromEvent(event.body.error, 'database');
+        transaction.onComplete(error, false, null);
+      } finally {
+        this._removeTransaction(event.id);
+      }
+    }
+  }
+
+  /**
+   *
+   * @param event
+   * @private
+   */
+  _handleComplete(event) {
+    const transaction = this._getTransaction(event.id);
+
+    if (transaction && !transaction.completed) {
+      transaction.completed = true;
+
+      try {
+        // error, committed, snapshot
+        transaction.onComplete(null, event.body.committed, Object.assign({}, event.body.snapshot));
+      } finally {
+        this._removeTransaction(event.id);
+      }
+    }
+  }
+}