const Stream = require('stream');
const util = require('util');
const net = require('net');
const tls = require('tls');
// eslint-disable-next-line node/no-deprecated-api
const { parse } = require('url');
const semver = require('semver');

let http2;
if (semver.gte(process.version, 'v10.10.0')) http2 = require('http2');
else
  throw new Error('superagent: this version of Node.js does not support http2');

const {
  HTTP2_HEADER_PATH,
  HTTP2_HEADER_STATUS,
  HTTP2_HEADER_METHOD,
  HTTP2_HEADER_AUTHORITY,
  HTTP2_HEADER_HOST,
  HTTP2_HEADER_SET_COOKIE,
  NGHTTP2_CANCEL
} = http2.constants;

function setProtocol(protocol) {
  return {
    request(options) {
      return new Request(protocol, options);
    }
  };
}

function Request(protocol, options) {
  Stream.call(this);
  const defaultPort = protocol === 'https:' ? 443 : 80;
  const defaultHost = 'localhost';
  const port = options.port || defaultPort;
  const host = options.host || defaultHost;

  delete options.port;
  delete options.host;

  this.method = options.method;
  this.path = options.path;
  this.protocol = protocol;
  this.host = host;

  delete options.method;
  delete options.path;

  const sessionOptions = { ...options };
  if (options.socketPath) {
    sessionOptions.socketPath = options.socketPath;
    sessionOptions.createConnection = this.createUnixConnection.bind(this);
  }

  this._headers = {};

  const session = http2.connect(`${protocol}//${host}:${port}`, sessionOptions);
  this.setHeader('host', `${host}:${port}`);

  session.on('error', err => this.emit('error', err));

  this.session = session;
}

/**
 * Inherit from `Stream` (which inherits from `EventEmitter`).
 */
util.inherits(Request, Stream);

Request.prototype.createUnixConnection = function(authority, options) {
  switch (this.protocol) {
    case 'http:':
      return net.connect(options.socketPath);
    case 'https:':
      options.ALPNProtocols = ['h2'];
      options.servername = this.host;
      options.allowHalfOpen = true;
      return tls.connect(options.socketPath, options);
    default:
      throw new Error('Unsupported protocol', this.protocol);
  }
};

// eslint-disable-next-line no-unused-vars
Request.prototype.setNoDelay = function(bool) {
  // We can not use setNoDelay with HTTP/2.
  // Node 10 limits http2session.socket methods to ones safe to use with HTTP/2.
  // See also https://nodejs.org/api/http2.html#http2_http2session_socket
};

Request.prototype.getFrame = function() {
  if (this.frame) {
    return this.frame;
  }

  const method = {
    [HTTP2_HEADER_PATH]: this.path,
    [HTTP2_HEADER_METHOD]: this.method
  };

  let headers = this.mapToHttp2Header(this._headers);

  headers = Object.assign(headers, method);

  const frame = this.session.request(headers);
  // eslint-disable-next-line no-unused-vars
  frame.once('response', (headers, flags) => {
    headers = this.mapToHttpHeader(headers);
    frame.headers = headers;
    frame.statusCode = headers[HTTP2_HEADER_STATUS];
    frame.status = frame.statusCode;
    this.emit('response', frame);
  });

  this._headerSent = true;

  frame.once('drain', () => this.emit('drain'));
  frame.on('error', err => this.emit('error', err));
  frame.on('close', () => this.session.close());

  this.frame = frame;
  return frame;
};

Request.prototype.mapToHttpHeader = function(headers) {
  const keys = Object.keys(headers);
  const http2Headers = {};
  for (let key of keys) {
    let value = headers[key];
    key = key.toLowerCase();
    switch (key) {
      case HTTP2_HEADER_SET_COOKIE:
        value = Array.isArray(value) ? value : [value];
        break;
      default:
        break;
    }

    http2Headers[key] = value;
  }

  return http2Headers;
};

Request.prototype.mapToHttp2Header = function(headers) {
  const keys = Object.keys(headers);
  const http2Headers = {};
  for (let key of keys) {
    let value = headers[key];
    key = key.toLowerCase();
    switch (key) {
      case HTTP2_HEADER_HOST:
        key = HTTP2_HEADER_AUTHORITY;
        value = /^http:\/\/|^https:\/\//.test(value)
          ? parse(value).host
          : value;
        break;
      default:
        break;
    }

    http2Headers[key] = value;
  }

  return http2Headers;
};

Request.prototype.setHeader = function(name, value) {
  this._headers[name.toLowerCase()] = value;
};

Request.prototype.getHeader = function(name) {
  return this._headers[name.toLowerCase()];
};

Request.prototype.write = function(data, encoding) {
  const frame = this.getFrame();
  return frame.write(data, encoding);
};

Request.prototype.pipe = function(stream, options) {
  const frame = this.getFrame();
  return frame.pipe(stream, options);
};

Request.prototype.end = function(data) {
  const frame = this.getFrame();
  frame.end(data);
};

// eslint-disable-next-line no-unused-vars
Request.prototype.abort = function(data) {
  const frame = this.getFrame();
  frame.close(NGHTTP2_CANCEL);
  this.session.destroy();
};

exports.setProtocol = setProtocol;
