// Copyright IBM Corp. and LoopBack contributors 2018,2020. All Rights Reserved.
// Node module: @loopback/rest
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT

import {Context} from '@loopback/core';
import {
  HandlerContext,
  MiddlewareContext,
  Request,
  Response,
} from '@loopback/express';
import {RestBindings} from './keys';
import {RestServerResolvedConfig} from './rest.server';

/**
 * A per-request Context combining an IoC container with handler context
 * (request, response, etc.).
 */
export class RequestContext
  extends MiddlewareContext
  implements HandlerContext
{
  /**
   * Get the protocol used by the client to make the request.
   * Please note this protocol may be different from what we are observing
   * at HTTP/TCP level, because reverse proxies like nginx or sidecars like
   * Envoy are switching between protocols.
   */
  get requestedProtocol(): string {
    return (
      ((this.request.get('x-forwarded-proto') ?? '').split(',')[0] ||
        this.request.protocol ||
        this.serverConfig.protocol) ??
      'http'
    );
  }

  /**
   * Get the effective base path of the incoming request. This base path
   * combines `baseUrl` provided by Express when LB4 handler is mounted on
   * a non-root path, with the `basePath` value configured at LB4 side.
   */
  get basePath(): string {
    const request = this.request;
    let basePath = this.serverConfig.basePath ?? '';
    if (request.baseUrl && request.baseUrl !== '/') {
      if (!basePath || request.baseUrl.endsWith(basePath)) {
        // Express has already applied basePath to baseUrl
        basePath = request.baseUrl;
      } else {
        basePath = request.baseUrl + basePath;
      }
    }
    return basePath;
  }

  /**
   * Get the base URL used by the client to make the request.
   * This URL contains the protocol, hostname, port and base path.
   * The path of the invoked route and query string is not included.
   *
   * Please note these values may be different from what we are observing
   * at HTTP/TCP level, because reverse proxies like nginx are rewriting them.
   */
  get requestedBaseUrl(): string {
    const request = this.request;
    const config = this.serverConfig;

    const protocol = this.requestedProtocol;
    // The host can be in one of the forms
    // [::1]:3000
    // [::1]
    // 127.0.0.1:3000
    // 127.0.0.1
    let {host, port} = parseHostAndPort(
      request.get('x-forwarded-host') ?? request.headers.host,
    );

    const forwardedPort = (request.get('x-forwarded-port') ?? '').split(',')[0];
    port = forwardedPort || port;

    if (!host) {
      // No host detected from http headers
      // Use the configured values or the local network address
      host = config.host ?? request.socket.localAddress ?? '';
      port = ((config.port || request.socket.localPort) ?? '').toString();
    }

    // clear default ports
    port = protocol === 'https' && port === '443' ? '' : port;
    port = protocol === 'http' && port === '80' ? '' : port;

    // add port number of present
    host += port !== '' ? ':' + port : '';

    return protocol + '://' + host + this.basePath;
  }

  constructor(
    public readonly request: Request,
    public readonly response: Response,
    parent: Context,
    public readonly serverConfig: RestServerResolvedConfig,
    name?: string,
  ) {
    super(request, response, parent, name);
  }

  protected setupBindings() {
    super.setupBindings();
    this.bind(RestBindings.Http.REQUEST).to(this.request).lock();
    this.bind(RestBindings.Http.RESPONSE).to(this.response).lock();
    this.bind(RestBindings.Http.CONTEXT).to(this).lock();
  }
}

function parseHostAndPort(host: string | undefined) {
  host = host ?? '';
  host = host.split(',')[0];
  const portPattern = /:([0-9]+)$/;
  const port = (host.match(portPattern) ?? [])[1] || '';
  host = host.replace(portPattern, '');
  return {host, port};
}