import { graphql } from 'graphql';
import Logger from '../utils/Logger';
import * as fetch from 'isomorphic-fetch';

const logger = new Logger('GraphqlClient');

interface IResponse<T> {
  data: T;
}

export default class GraphqlClient {
  private static clientInstance: GraphqlClient;

  constructor(private url, private token) {}

  query = <Variables, ResponseData>(
    query: string,
    variables: Variables
  ): Promise<IResponse<ResponseData>> => this.doOperation('query', query, variables);

  mutate = <Variables, Response extends {}>(
    mutation: string,
    variables: Variables
  ): Promise<Response> => this.doOperation('mutation', mutation, variables);

  public static getClient = () => {
    if (!GraphqlClient.clientInstance) {
      GraphqlClient.clientInstance = new GraphqlClient(
        process.env.GRAPHQL_API,
        process.env.ADMIN_TOKEN
      );
    }

    return GraphqlClient.clientInstance;
  };

  private doOperation = (
    type: 'query' | 'mutation',
    operation: string,
    variables
  ) =>
    fetch(this.url, {
      method: 'POST',
      body: JSON.stringify({
        query: operation,
        variables: variables
      }),
      headers: {
        Authorization: this.token,
        'content-type': 'application/json'
      }
    })
      .then(res => res.json())
      .then(function(body) {
        if (body.errors && body.errors.length) {
          logger.info(
            'Error running graphql request',
            JSON.stringify({ errors: body.errors, operation, variables })
          );
          throw new Error(body.errors);
        }

        return body;
      });
}