import { Global, DynamicModule, Module } from '@nestjs/common';
import { ModuleRef } from '@nestjs/core';
import { PromModuleOptions } from './interfaces/prom-options.interface';
import {
  DEFAULT_PROM_REGISTRY,
  PROM_REGISTRY_NAME,
  DEFAULT_PROM_OPTIONS,
} from './metrics.constants';

import * as client from 'prom-client';
import {
  Registry,
  collectDefaultMetrics,
  DefaultMetricsCollectorConfiguration,
} from 'prom-client';
import { getRegistryName, getOptionsName } from './common/prom.utils';

@Global()
@Module({})
export class PromCoreModule {
  constructor(private readonly moduleRef: ModuleRef) {}

  static forRoot(options: PromModuleOptions = {}): DynamicModule {
    const {
      withDefaultsMetrics,
      registryName,
      timeout,
      prefix,
      ...promOptions
    } = options;

    const promRegistryName = registryName
      ? getRegistryName(registryName)
      : DEFAULT_PROM_REGISTRY;

    const promRegistryNameProvider = {
      provide: PROM_REGISTRY_NAME,
      useValue: promRegistryName,
    };

    // const promOptionName = registryName ?
    //   getOptionsName(registryName)
    //   : DEFAULT_PROM_OPTIONS;

    const promRegistryOptionsProvider = {
      provide: DEFAULT_PROM_OPTIONS,
      useValue: options,
    };

    const registryProvider = {
      provide: promRegistryName,
      useFactory: (): Registry => {
        let registry = client.register;
        if (promRegistryName !== DEFAULT_PROM_REGISTRY) {
          registry = new Registry();
        }

        if (withDefaultsMetrics !== false) {
          const defaultMetricsOptions: DefaultMetricsCollectorConfiguration = {
            register: registry,
          };
          if (timeout) {
            defaultMetricsOptions.timeout = timeout;
          }
          if (prefix) {
            defaultMetricsOptions.prefix = prefix;
          }
          collectDefaultMetrics(defaultMetricsOptions);
        }

        return registry;
      },
    };

    return {
      module: PromCoreModule,
      providers: [
        promRegistryNameProvider,
        promRegistryOptionsProvider,
        registryProvider,
      ],
      exports: [registryProvider],
    };
  }

  /**
   * on destroy
   */
  onModuleDestroy() {}
}