fix: Add Mongodb-watcher

package.json

@@ -0,0 +1,22 @@
+{
+  "name": "mongodb-watcher",
+  "version": "1.0.0",
+  "description": "moggodb-watcher for node casbin",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "@types/jest": "^26.0.23",
+    "@types/mongodb": "^3.6.17",
+    "casbin": "^5.7.1",
+    "mongodb": "^3.6.9"
+  },
+  "devDependencies": {
+    "jest": "^27.0.4",
+    "ts-jest": "^27.0.2",
+    "typescript": "^4.3.2"
+  }
+}

src/mongodb.ts

@@ -0,0 +1,29 @@
+import {MongoClient} from "mongodb";
+
+export class MongodbConnection{
+    private readonly uri: string;
+    private readonly dbName: string;
+    private readonly collectionName: string;
+    public client: MongoClient;
+
+
+    constructor(uri :string, dbName: string, collectionName: string) {
+        this.uri = uri;
+        this.dbName = dbName;
+        this.collectionName = collectionName;
+    }
+
+
+    open(){
+       this.client = new MongoClient(this.uri);
+    }
+
+    async getCollection(){
+        await this.client.connect();
+        return this.client.db(this.dbName).collection(this.collectionName);
+    }
+
+    public close(){
+        this.client.close();
+    }
+}

src/watcher.ts

@@ -0,0 +1,53 @@
+import {MongodbConnection} from './mongodb'
+import {Watcher} from "casbin";
+
+export default class MongodbWatcher implements Watcher{
+
+    private readonly keyName : string;
+    private mongodbConnection : MongodbConnection;
+    private callback : () => void;
+
+    public static async newWatcher(uri : string,dbName: string,collectionName: string,keyName?: string):Promise<MongodbWatcher>{
+        return new MongodbWatcher(uri,dbName,collectionName,keyName);
+    }
+
+    private constructor(uri: string, dbName: string,collectionName: string, keyName?: string) {
+        this.keyName = keyName || "/casbin";
+        this.mongodbConnection = new MongodbConnection(uri,dbName,collectionName);
+        this.mongodbConnection.open();
+        this.mongodbConnection.getCollection().then(collection=>{
+           let that = this;
+           let latest =  collection.find({}).limit(1);
+           latest.next(function (err,doc){
+               if (err) throw err;
+               let query = {_id: {$gt: doc._id}};
+               let options = {tailable:true,awaitData: true, numberOfRetries:-1};
+               let cursor = collection.find(query,options);
+               (function next(){
+                   cursor.next(function (err,message){
+                       if (err) throw err;
+                       if (message.message === that.keyName){
+                           if (that.callback)
+                               that.callback();
+                       }
+                       next();
+                   });
+               })();
+           })
+        })
+    }
+    public setUpdateCallback(callback: () => void): void {
+        this.callback = callback;
+    }
+
+    public async update(): Promise<boolean> {
+        let collection = await this.mongodbConnection.getCollection();
+        await collection.insertOne({message:this.keyName,time: Date.now()})
+        return true
+    }
+
+    public async close(): Promise<void>{
+        this.mongodbConnection.close();
+    }
+
+}

tsconfig.json

@@ -0,0 +1,16 @@
+{
+  "compilerOptions": {
+    "target": "es6",
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "strict": true,
+    "strictPropertyInitialization": false,
+    "declaration": true,
+    "declarationDir": "lib",
+    "outDir": "lib",
+    "esModuleInterop": true
+  },
+  "include": [
+    "src/**/*"
+  ]
+}