import { Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { PipelineTask } from './pipeline-task.entity';
import { Repository } from 'typeorm';
import { CreatePipelineTaskInput } from './dtos/create-pipeline-task.input';
import { RedisService } from 'nestjs-redis';
import { Pipeline } from '../pipelines/pipeline.entity';
import { InjectQueue } from '@nestjs/bull';
import { PIPELINE_TASK_QUEUE } from './pipeline-tasks.constants';
import { Queue } from 'bull';
import { LockFailedException } from '../commons/exceptions/lock-failed.exception';

@Injectable()
export class PipelineTasksService {
  constructor(
    @InjectRepository(PipelineTask)
    private readonly repository: Repository<PipelineTask>,
    @InjectRepository(Pipeline)
    private readonly pipelineRepository: Repository<Pipeline>,
    private readonly redis: RedisService,
    @InjectQueue(PIPELINE_TASK_QUEUE)
    private readonly queue: Queue<PipelineTask>,
  ) {}
  async addTask(dto: CreatePipelineTaskInput) {
    const pipeline = await this.pipelineRepository.findOneOrFail({
      where: { id: dto.pipelineId },
      relations: ['project'],
    });
    const task = await this.repository.save(this.repository.create(dto));
    task.pipeline = pipeline;

    const [lckKey, tasksKey] = this.getRedisTokens(pipeline);
    const redis = this.redis.getClient();
    await redis.lpush(tasksKey, JSON.stringify(task)).finally(() => {
      return redis.decr(lckKey);
    });
    await this.doNextTask(pipeline);
  }

  async doNextTask(pipeline: Pipeline) {
    const [lckKey, tasksKey] = this.getRedisTokens(pipeline);
    const redis = this.redis.getClient();
    await redis.set(lckKey, 0, 'EX', 10, 'NX');

    await new Promise(async (resolve, reject) => {
      for (let i = 0; i < 5; i++) {
        if ((await redis.incr(lckKey)) === 1) {
          resolve(undefined);
          return;
        }
        await redis.decr(lckKey);
        await new Promise((resolve) => setTimeout(resolve, 2000));
      }
      reject(new LockFailedException(lckKey));
    });

    const task = JSON.parse(
      (await redis.rpop(tasksKey).finally(() => redis.decr(lckKey))) ?? 'null',
    );
    if (task) {
      await this.queue.add(task);
    }
  }

  getRedisTokens(pipeline: Pipeline): [string, string] {
    return [`pipeline-${pipeline.id}:lck`, `pipeline-${pipeline.id}:tasks`];
  }
}