import * as http from 'http';

export default function getUrlContents({ host, path }: {host: string, path: string}): Promise<ArrayBuffer> {
  return new Promise((resolve, reject) => {
    const request = http.request({
      family: 4,
      host,
      path,
    }, (response) => {
      if (response.statusCode !== 200) {
        return reject(`Expected status code 200 but received ${response.statusCode}`);
      }
      const headerLength = Number(response.headers['content-length']);

      const chunkList: Buffer[] = [];
      let totalLength = 0;
      response.on('data', (chunk: Buffer) => {
        chunkList.push(chunk);
        totalLength += chunk.length;
      });
      response.on('end', () => {
        if (totalLength !== headerLength) {
          return reject(`Expected length ${headerLength} but received ${totalLength}`);
        }
        const fileContents = Buffer.concat(chunkList, totalLength);
        resolve(fileContents.buffer as ArrayBuffer);
      });
    });

    request.on('error', (e) => {
      reject(e);
    });
    request.end();
  });
}