Adding support to persist variables in Redis

back/src/Services/Repository/RedisVariablesRepository.ts

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+import { promisify } from "util";
+import { RedisClient } from "redis";
+import { VariablesRepositoryInterface } from "./VariablesRepositoryInterface";
+
+/**
+ * Class in charge of saving/loading variables from the data store
+ */
+export class RedisVariablesRepository implements VariablesRepositoryInterface {
+    private readonly hgetall: OmitThisParameter<(arg1: string) => Promise<{ [p: string]: string }>>;
+    private readonly hset: OmitThisParameter<(arg1: [string, ...string[]]) => Promise<number>>;
+
+    constructor(redisClient: RedisClient) {
+        // @eslint-disable-next-line @typescript-eslint/unbound-method
+        this.hgetall = promisify(redisClient.hgetall).bind(redisClient);
+        // @eslint-disable-next-line @typescript-eslint/unbound-method
+        this.hset = promisify(redisClient.hset).bind(redisClient);
+    }
+
+    /**
+     * Load all variables for a room.
+     *
+     * Note: in Redis, variables are stored in a hashmap and the key is the roomUrl
+     */
+    async loadVariables(roomUrl: string): Promise<{ [key: string]: string }> {
+        return this.hgetall(roomUrl);
+    }
+
+    async saveVariable(roomUrl: string, key: string, value: string): Promise<number> {
+        // TODO: handle the case for "undefined"
+        // TODO: handle the case for "undefined"
+        // TODO: handle the case for "undefined"
+        // TODO: handle the case for "undefined"
+        // TODO: handle the case for "undefined"
+
+        // TODO: SLOW WRITING EVERY 2 SECONDS WITH A TIMEOUT
+
+        // @ts-ignore See https://stackoverflow.com/questions/63539317/how-do-i-use-hmset-with-node-promisify
+        return this.hset(roomUrl, key, value);
+    }
+}

back/src/Services/Repository/VariablesRepository.ts

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+import { RedisVariablesRepository } from "./RedisVariablesRepository";
+import { redisClient } from "../RedisClient";
+import { VoidVariablesRepository } from "./VoidVariablesRepository";
+import { VariablesRepositoryInterface } from "./VariablesRepositoryInterface";
+
+let variablesRepository: VariablesRepositoryInterface;
+if (!redisClient) {
+    console.warn("WARNING: Redis isnot configured. No variables will be persisted.");
+    variablesRepository = new VoidVariablesRepository();
+} else {
+    variablesRepository = new RedisVariablesRepository(redisClient);
+}
+
+export { variablesRepository };

back/src/Services/Repository/VariablesRepositoryInterface.ts

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+export interface VariablesRepositoryInterface {
+    /**
+     * Load all variables for a room.
+     *
+     * Note: in Redis, variables are stored in a hashmap and the key is the roomUrl
+     */
+    loadVariables(roomUrl: string): Promise<{ [key: string]: string }>;
+
+    saveVariable(roomUrl: string, key: string, value: string): Promise<number>;
+}

back/src/Services/Repository/VoidVariablesRepository.ts

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+import { VariablesRepositoryInterface } from "./VariablesRepositoryInterface";
+
+/**
+ * Mock class in charge of NOT saving/loading variables from the data store
+ */
+export class VoidVariablesRepository implements VariablesRepositoryInterface {
+    loadVariables(roomUrl: string): Promise<{ [key: string]: string }> {
+        return Promise.resolve({});
+    }
+
+    saveVariable(roomUrl: string, key: string, value: string): Promise<number> {
+        return Promise.resolve(0);
+    }
+}