import {
  Injectable,
  OnApplicationBootstrap,
  OnModuleDestroy,
  OnModuleInit,
} from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { JobsOptions, Queue, Worker } from 'bullmq';
import { AppLoggerService } from '../logging/app-logger.service';
import { RedisService } from '../redis/redis.service';

type JobProcessor = (payload: Record<string, unknown>) => Promise<void>;

@Injectable()
export class AppQueueService
  implements OnModuleInit, OnApplicationBootstrap, OnModuleDestroy
{
  private readonly processors = new Map<string, JobProcessor>();
  private queue: Queue | null = null;
  private worker: Worker | null = null;

  constructor(
    private readonly configService: ConfigService,
    private readonly redisService: RedisService,
    private readonly logger: AppLoggerService,
  ) {}

  onModuleInit(): void {
    // Intentionally empty. Processors are usually registered by other providers before bootstrap.
  }

  onApplicationBootstrap(): void {
    if (!this.isQueueEnabled() || !this.redisService.isEnabled()) {
      return;
    }

    const queueName = this.getQueueName();
    const queueConnection = this.redisService.createQueueClient();
    const workerConnection = this.redisService.createQueueClient();
    if (!queueConnection || !workerConnection) {
      return;
    }

    this.queue = new Queue(queueName, {
      connection: queueConnection,
      defaultJobOptions: this.getDefaultJobOptions(),
    });

    this.worker = new Worker(
      queueName,
      async (job) => {
        const processor = this.processors.get(job.name);
        if (!processor) {
          throw new Error(`No processor registered for job "${job.name}"`);
        }

        await processor(job.data as Record<string, unknown>);
      },
      {
        connection: workerConnection,
        concurrency:
          this.configService.get<number>('queue.workerConcurrency', { infer: true }) ?? 5,
      },
    );

    this.worker.on('failed', (job, error) => {
      this.logger.error(
        {
          queue: queueName,
          jobName: job?.name,
          jobId: job?.id,
          error: error.message,
        },
        undefined,
        AppQueueService.name,
      );
    });
  }

  registerProcessor(jobName: string, processor: JobProcessor): void {
    this.processors.set(jobName, processor);
  }

  async enqueue(
    jobName: string,
    payload: Record<string, unknown>,
    options: JobsOptions = {},
  ): Promise<void> {
    if (this.queue) {
      await this.queue.add(jobName, payload, {
        ...this.getDefaultJobOptions(),
        ...options,
      });
      return;
    }

    const processor = this.processors.get(jobName);
    if (!processor) {
      return;
    }

    queueMicrotask(() => {
      void processor(payload).catch((error: Error) => {
        this.logger.error(
          {
            jobName,
            payload,
            error: error.message,
          },
          error.stack,
          AppQueueService.name,
        );
      });
    });
  }

  async onModuleDestroy(): Promise<void> {
    await this.worker?.close();
    await this.queue?.close();
    this.worker = null;
    this.queue = null;
  }

  private isQueueEnabled(): boolean {
    return this.configService.get<boolean>('queue.enabled', { infer: true }) ?? false;
  }

  private getQueueName(): string {
    return this.configService.get<string>('queue.name', { infer: true }) ?? 'app-jobs';
  }

  private getDefaultJobOptions(): JobsOptions {
    return {
      attempts:
        this.configService.get<number>('queue.defaultJobAttempts', { infer: true }) ?? 3,
      backoff: {
        type: 'exponential',
        delay:
          this.configService.get<number>('queue.defaultJobBackoffMs', { infer: true }) ?? 1000,
      },
      removeOnComplete:
        this.configService.get<boolean>('queue.removeOnComplete', { infer: true }) ?? true,
    };
  }
}