import { Injectable } from '@nestjs/common';

import type { CheckDetails } from '../health/helpers';
import { CheckResult } from '../health/helpers';
import type { HealthIndicator } from '../health/types';

import type { Config } from './config.abstract';
import { ReloadEvents } from './reload';
import type { ConfigSource } from './sources';

@Injectable()
export class ConfigReloadIndicator implements HealthIndicator {
  private errors = new Map<ConfigSource | Config, Error>();

  constructor(private events: ReloadEvents) {
    this.events
      .on('reload_failure', (source, err) => this.errors.set(source, err))
      .on('update_failure', (config, err) => this.errors.set(config, err))
      .on('reload', (source) => this.errors.delete(source))
      .on('update', (config) => this.errors.delete(config));
  }

  async check(): Promise<CheckResult> {
    if (this.errors.size === 0) {
      return CheckResult.up({});
    }

    const details: CheckDetails = {};

    for (const [key, err] of this.errors.entries()) {
      details[key.constructor.name] = { error: err };
    }

    return CheckResult.down(details);
  }
}