/**
 * Copyright 2013-2019  GenieACS Inc.
 *
 * This file is part of GenieACS.
 *
 * GenieACS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * GenieACS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with GenieACS.  If not, see <http://www.gnu.org/licenses/>.
 */

import * as crypto from "crypto";
import * as dgram from "dgram";
import { URL } from "url";
import * as http from "http";
import { evaluateAsync } from "./common/expression";
import { Expression } from "./types";
import * as auth from "./auth";
import * as extensions from "./extensions";
import * as debug from "./debug";

async function extractAuth(
  exp: Expression,
  dflt: any
): Promise<[string, string, Expression]> {
  let username, password;
  const _exp = await evaluateAsync(
    exp,
    {},
    0,
    async (e: Expression): Promise<Expression> => {
      if (!username && Array.isArray(e) && e[0] === "FUNC") {
        if (e[1] === "EXT") {
          if (typeof e[2] !== "string" || typeof e[3] !== "string") return null;

          for (let i = 4; i < e.length; i++)
            if (Array.isArray(e[i])) return null;

          const { fault, value } = await extensions.run(e.slice(2));
          return fault ? null : value;
        } else if (e[1] === "AUTH") {
          if (!Array.isArray(e[2]) && !Array.isArray(e[3])) {
            username = e[2] || "";
            password = e[3] || "";
          }
          return dflt;
        }
      }
      return e;
    }
  );
  return [username, password, _exp];
}

function httpGet(
  url: URL,
  options: http.RequestOptions,
  _debug: boolean,
  deviceId: string
): Promise<{ statusCode: number; headers: http.IncomingHttpHeaders }> {
  return new Promise((resolve, reject) => {
    const req = http
      .get(url, options, (res) => {
        res.resume();
        resolve({ statusCode: res.statusCode, headers: res.headers });
        if (_debug) {
          debug.outgoingHttpRequest(req, deviceId, "GET", url, null);
          debug.incomingHttpResponse(res, deviceId, null);
        }
      })
      .on("error", (err) => {
        req.destroy();
        reject(err);
        if (_debug)
          debug.outgoingHttpRequestError(req, deviceId, "GET", url, err);
      })
      .on("timeout", () => {
        req.destroy();
      });
  });
}

export async function httpConnectionRequest(
  address: string,
  authExp: Expression,
  allowBasicAuth: boolean,
  timeout: number,
  _debug: boolean,
  deviceId: string
): Promise<string> {
  const url = new URL(address);
  if (url.protocol !== "http:")
    return "Invalid connection request URL or protocol";

  const options: http.RequestOptions = {
    agent: new http.Agent({ maxSockets: 1, keepAlive: true, timeout: timeout }),
  };

  let authHeader: Record<string, string>;
  let username: string;
  let password: string;

  while (!authHeader || (username != null && password != null)) {
    let opts = options;
    if (authHeader) {
      if (authHeader["method"] === "Basic") {
        if (!allowBasicAuth) return "Basic HTTP authentication not allowed";

        opts = Object.assign(
          {
            headers: {
              Authorization: auth.basic(username || "", password || ""),
            },
          },
          options
        );
      } else if (authHeader["method"] === "Digest") {
        opts = Object.assign(
          {
            headers: {
              Authorization: auth.solveDigest(
                username,
                password,
                url.pathname + url.search,
                "GET",
                null,
                authHeader
              ),
            },
          },
          options
        );
      } else {
        return "Unrecognized auth method";
      }
    }

    let res: { statusCode: number; headers: http.IncomingHttpHeaders };
    try {
      res = await httpGet(url, opts, _debug, deviceId);
    } catch (err) {
      // Workaround for some devices unexpectedly closing the connection
      if (authHeader) {
        try {
          res = await httpGet(url, opts, _debug, deviceId);
        } catch (err) {
          return `Connection request error: ${err.message}`;
        }
      }

      if (err["code"] === "ECONNRESET" || err["code"] === "ECONNREFUSED")
        return "Device is offline";

      return `Connection request error: ${err.message}`;
    }

    if (res.statusCode === 200 || res.statusCode === 204) return "";

    // When a Connection Request is received for the Virtual CWMP Device and the Proxied
    // Device is offline the CPE Proxier MUST respond with an HTTP 503 failure
    if (res.statusCode === 503) return "Device is offline";

    if (res.statusCode === 401 && res.headers["www-authenticate"]) {
      try {
        authHeader = auth.parseWwwAuthenticateHeader(
          res.headers["www-authenticate"]
        );
      } catch (err) {
        return "Connection request error: Error parsing www-authenticate header";
      }
      [username, password, authExp] = await extractAuth(authExp, false);
    } else {
      return `Connection request error: Unexpected status code ${res.statusCode}`;
    }
  }

  return "Connection request error: Incorrect connection request credentials";
}

export async function udpConnectionRequest(
  host: string,
  port: number,
  authExp: Expression,
  sourcePort = 0,
  _debug: boolean,
  deviceId: string
): Promise<void> {
  const now = Date.now();

  const client = dgram.createSocket({ type: "udp4", reuseAddr: true });
  // When a device is NAT'ed, the UDP Connection Request must originate from
  // the same address and port used by the STUN server, in order to traverse
  // the firewall. This does require that the Genieacs NBI and STUN server
  // are allowed to bind to the same address and port. The STUN server needs
  // to open its UDP port with the SO_REUSEADDR option, allowing the NBI to
  // also bind to the same port.
  if (sourcePort) client.bind({ port: sourcePort, exclusive: true });

  let username: string;
  let password: string;

  [username, password, authExp] = await extractAuth(authExp, null);

  if (username == null) username = "";
  if (password == null) password = "";
  while (username != null && password != null) {
    const ts = Math.trunc(now / 1000);
    const id = Math.trunc(Math.random() * 4294967295);
    const cn = crypto.randomBytes(8).toString("hex");
    const sig = crypto
      .createHmac("sha1", password)
      .update(`${ts}${id}${username}${cn}`)
      .digest("hex");
    const uri = `http://${host}:${port}?ts=${ts}&id=${id}&un=${username}&cn=${cn}&sig=${sig}`;
    const msg = `GET ${uri} HTTP/1.1\r\nHost: ${host}:${port}\r\n\r\n`;
    const message = Buffer.from(msg);

    for (let i = 0; i < 3; ++i) {
      await new Promise<void>((resolve, reject) => {
        client.send(message, 0, message.length, port, host, (err: Error) => {
          if (err) reject(err);
          else resolve();
          if (_debug) debug.outgoingUdpMessage(host, deviceId, port, msg);
        });
      });
    }

    [username, password, authExp] = await extractAuth(authExp, null);
  }
  client.close();
}