feat(server): job system (#10134)

packages/backend/server/src/base/job/queue/scanner.ts

@@ -0,0 +1,77 @@
+import { Injectable, OnModuleInit } from '@nestjs/common';
+
+import { ModuleScanner } from '../../nestjs';
+import { getJobHandlerMetadata } from './def';
+
+interface JobHandler {
+  name: string;
+  fn: (payload: any) => any;
+}
+
+@Injectable()
+export class JobHandlerScanner implements OnModuleInit {
+  private readonly handlers: Record<string, JobHandler> = {};
+
+  constructor(private readonly scanner: ModuleScanner) {}
+
+  async onModuleInit() {
+    this.scan();
+  }
+
+  getHandler(jobName: JobName): JobHandler | undefined {
+    return this.handlers[jobName];
+  }
+
+  private scan() {
+    const providers = this.scanner.getAtInjectables();
+
+    providers.forEach(wrapper => {
+      const { instance, name } = wrapper;
+      if (!instance || wrapper.isAlias) {
+        return;
+      }
+
+      const methods = this.scanner.getAllMethodNames(instance);
+
+      methods.forEach(method => {
+        const fn = instance[method];
+
+        let jobNames = getJobHandlerMetadata(instance[method]);
+
+        if (jobNames.length === 0) {
+          return;
+        }
+
+        const signature = `${name}.${method}`;
+
+        if (typeof fn !== 'function') {
+          throw new Error(`Job handler [${signature}] is not a function.`);
+        }
+
+        if (!wrapper.isDependencyTreeStatic()) {
+          throw new Error(
+            `Provider [${name}] could not be RequestScoped or TransientScoped injectable if it contains job handlers.`
+          );
+        }
+
+        jobNames.forEach(jobName => {
+          if (this.handlers[jobName]) {
+            throw new Error(
+              `Job handler ${jobName} already defined in [${this.handlers[jobName].name}].`
+            );
+          }
+
+          this.handlers[jobName] = {
+            name: signature,
+            fn: (payload: any) => {
+              // NOTE(@forehalo):
+              //   we might create spies on the job handlers when testing,
+              //   avoid reusing `fn` variable to fail the spies or stubs
+              return instance[method].bind(instance)(payload);
+            },
+          };
+        });
+      });
+    });
+  }
+}