Reorganize project. Add folder for shared code between backend/dashboard. Switch from jest to ava for tests.

backend/src/data/BaseGuildRepository.ts

@@ -0,0 +1,28 @@
+import { BaseRepository } from "./BaseRepository";
+
+export class BaseGuildRepository extends BaseRepository {
+  private static guildInstances: Map<string, any>;
+
+  protected guildId: string;
+
+  constructor(guildId: string) {
+    super();
+    this.guildId = guildId;
+  }
+
+  /**
+   * Returns a cached instance of the inheriting class for the specified guildId,
+   * or creates a new instance if one doesn't exist yet
+   */
+  public static getGuildInstance<T extends typeof BaseGuildRepository>(this: T, guildId: string): InstanceType<T> {
+    if (!this.guildInstances) {
+      this.guildInstances = new Map();
+    }
+
+    if (!this.guildInstances.has(guildId)) {
+      this.guildInstances.set(guildId, new this(guildId));
+    }
+
+    return this.guildInstances.get(guildId) as InstanceType<T>;
+  }
+}