import { Service, Inject, Container } from '@rxdi/core';
import { mergeSchemas, introspectSchema, makeRemoteExecutableSchema } from 'graphql-tools';
import { createHttpLink } from 'apollo-link-http';
import { MicroserviceInterface } from './microservice.interface';
import fetch = require('node-fetch');
import { GraphQLSchema } from 'graphql';

@Service()
export class ProxyService {

  constructor(
    @Inject('gapi-microservice-config') private microservices: MicroserviceInterface[],
    @Inject('gapi-microservice-config-auth') private configAuth: {authorization?: Function}
  ) {}

  public async getSchemaIntrospection(): Promise<GraphQLSchema> {
    return await this.mergeSchemas(await Promise.all(this.microservices.map(ep => {
      console.log(`Microservice: ${ep.name} loaded!`);
      return this.getIntrospectSchema(ep);
    })));
  }

  private mergeSchemas(allSchemas): GraphQLSchema {
    return mergeSchemas({ schemas: allSchemas });
  }

  private async getIntrospectSchema(microservice: MicroserviceInterface): Promise<GraphQLSchema> {
    const headers = {authorization: ''};
    if (this.configAuth.authorization) {
      const Authorization = Container.get<{sign: (params) => string}>(this.configAuth.authorization);
      headers.authorization = Authorization.sign({
        email: microservice.name,
        id: -1,
        scope: ['ADMIN']
      });
    }
    const makeDatabaseServiceLink = () => createHttpLink({ uri: microservice.link, fetch, headers });
    return makeRemoteExecutableSchema({ schema: await introspectSchema(makeDatabaseServiceLink()), link: makeDatabaseServiceLink() });
  }

}