Lay groundwork for GraphQL sync

University-of-Auckland-SOFTENG761 · Aug 31, 2022 · ae666ad · ae666ad
1 parent cf89510
commit ae666ad
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Showing 4 changed files with 71 additions and 20 deletions.
diff --git a/apps/backend/src/app/users/users.service.ts b/apps/backend/src/app/users/users.service.ts
@@ -16,7 +16,12 @@ export class UserService {
     limit: number
   ): Promise<UserEntity[]> {
     let query: SelectQueryBuilder<UserEntity>;
-    if (minUpdatedAt === undefined || lastId === undefined) {
+    if (
+      minUpdatedAt === undefined ||
+      lastId === undefined ||
+      minUpdatedAt?.getTime() === 0 ||
+      lastId === ''
+    ) {
       query = this.usersRepository.createQueryBuilder('user');
     } else {
       query = this.usersRepository

diff --git a/apps/frontend/src/app/hooks/usePatients/usePatients.tsx b/apps/frontend/src/app/hooks/usePatients/usePatients.tsx
@@ -39,8 +39,8 @@ export const usePatients = () => {
   useEffect(() => {
     patientDatabase
       .get()
-      ?.then((db: RxDatabase) => {
-        setPatientsDb(db);
+      ?.then((db: RxDatabase | null) => {
+        db && setPatientsDb(db);
       })
       .catch((error: Error) => {
         console.log(error);

diff --git a/apps/frontend/src/database/database-constructor.ts b/apps/frontend/src/database/database-constructor.ts
@@ -1,20 +1,21 @@
 import { RxDatabase } from 'rxdb';
 
 class DatabaseConstructor {
-  private _db: RxDatabase | null;
-  private _databaseConstructor: () => Promise<RxDatabase>;
-  constructor(databaseConstructor: () => Promise<RxDatabase>) {
-    this._databaseConstructor = databaseConstructor;
-    this._db = null;
-    this.get = async (): Promise<RxDatabase> => {
-      if (!this._db) {
-        this._db = await this._databaseConstructor();
-      }
-      return this._db;
-    };
+  private _blocked = false;
+  private _db: RxDatabase | null = null;
+  private _dbInitializer: () => Promise<RxDatabase>;
+
+  public async get(): Promise<RxDatabase | null> {
+    if (!this._db && !this._blocked) {
+      this._blocked = true;
+      this._db = await this._dbInitializer();
+      this._blocked = false;
+    }
+    return Promise.resolve(this._db);
   }
-  get(): Promise<RxDatabase> | null {
-    return null;
+
+  constructor(dbInitializer: () => Promise<RxDatabase>) {
+    this._dbInitializer = dbInitializer;
   }
 }
 

diff --git a/apps/frontend/src/database/patient-database.ts b/apps/frontend/src/database/patient-database.ts
@@ -1,17 +1,49 @@
-import { addRxPlugin, createRxDatabase } from 'rxdb';
+import { addRxPlugin, createRxDatabase, RxDocument } from 'rxdb';
 import { getRxStorageDexie } from 'rxdb/plugins/dexie';
 import patientSchema from './patient-schema';
 import { RxDBUpdatePlugin } from 'rxdb/plugins/update';
 import DatabaseConstructor from './database-constructor';
-addRxPlugin(RxDBUpdatePlugin);
+import { RxDBReplicationGraphQLPlugin } from 'rxdb/plugins/replication-graphql';
+
+const addPlugins = async () => {
+  addRxPlugin(RxDBReplicationGraphQLPlugin);
+  addRxPlugin(RxDBUpdatePlugin);
 
-const initializePatientDatabase = async () => {
   if (process.env['NODE_ENV'] !== 'production') {
     await import('rxdb/plugins/dev-mode').then((module) => {
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
       addRxPlugin((module as any).RxDBDevModePlugin);
     });
   }
+};
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+const pullQueryBuilder = async (doc: RxDocument<any>) => {
+  if (!doc) {
+    doc = {
+      id: '',
+      updatedAt: 0,
+    };
+  }
+
+  const query = `{
+    userReplicationFeed(lastId: "${doc.id}", minUpdatedAt: ${doc.updatedAt}, limit: 5) {
+      id,
+      firstName,
+      lastName,
+      updatedAt,
+      deletedAt,
+    }
+  }`;
+
+  return {
+    query,
+    variables: {},
+  };
+};
+
+const initializePatientDatabase = async () => {
+  await addPlugins();
   const db = await createRxDatabase({
     name: 'patientdb',
     storage: getRxStorageDexie(),
@@ -21,9 +53,22 @@ const initializePatientDatabase = async () => {
       schema: patientSchema,
     },
   });
+  const replicationState = db.collections['patients'].syncGraphQL({
+    url: 'http://localhost:3333/graphql', // url to the GraphQL endpoint
+    pull: {
+      queryBuilder: pullQueryBuilder, // the queryBuilder from above
+      batchSize: 5,
+    },
+    deletedFlag: 'deletedAt', // the flag which indicates if a pulled document is deleted
+    live: true, // if this is true, rxdb will watch for ongoing changes and sync them, when false, a one-time-replication will be done
+  });
+  replicationState.received$.subscribe((response) =>
+    console.log('response from graphql', response)
+  );
+  replicationState.run();
   return db;
 };
 
-export const patientDatabase: DatabaseConstructor = new DatabaseConstructor(
+export const patientDatabase = new DatabaseConstructor(
   initializePatientDatabase
 );