/*
 * This file is part of PowerDNS or dnsdist.
 * Copyright -- PowerDNS.COM B.V. and its contributors
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * In addition, for the avoidance of any doubt, permission is granted to
 * link this program with OpenSSL and to (re)distribute the binaries
 * produced as the result of such linking.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "remotebackend.hh"
#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.h>

#include <sstream>
#include "pdns/lock.hh"

#ifndef UNIX_PATH_MAX
#define UNIX_PATH_MAX 108
#endif

HTTPConnector::HTTPConnector(std::map<std::string, std::string> options) :
  d_socket(nullptr)
{

  if (options.find("url") == options.end()) {
    throw PDNSException("Cannot find 'url' option in the remote backend HTTP connector's parameters");
  }

  this->d_url = options.find("url")->second;

  try {
    YaHTTP::URL url(d_url);
    d_host = url.host;
    d_port = url.port;
  }
  catch (const std::exception& e) {
    throw PDNSException("Error parsing the 'url' option provided to the remote backend HTTP connector: " + std::string(e.what()));
  }

  if (options.find("url-suffix") != options.end()) {
    this->d_url_suffix = options.find("url-suffix")->second;
  }
  else {
    this->d_url_suffix = "";
  }
  this->timeout = 2;
  this->d_post = false;
  this->d_post_json = false;

  if (options.find("timeout") != options.end()) {
    this->timeout = std::stoi(options.find("timeout")->second) / 1000;
  }
  if (options.find("post") != options.end()) {
    std::string val = options.find("post")->second;
    if (val == "yes" || val == "true" || val == "on" || val == "1") {
      this->d_post = true;
    }
  }
  if (options.find("post_json") != options.end()) {
    std::string val = options.find("post_json")->second;
    if (val == "yes" || val == "true" || val == "on" || val == "1") {
      this->d_post_json = true;
    }
  }
}

HTTPConnector::~HTTPConnector() = default;

void HTTPConnector::addUrlComponent(const Json& parameters, const string& element, std::stringstream& ss)
{
  std::string sparam;
  if (parameters[element] != Json()) {
    ss << "/" << YaHTTP::Utility::encodeURL(asString(parameters[element]), false);
  }
}

std::string HTTPConnector::buildMemberListArgs(const std::string& prefix, const Json& args)
{
  std::stringstream stream;

  for (const auto& pair : args.object_items()) {
    stream << prefix << "[" << YaHTTP::Utility::encodeURL(pair.first, false) << "]=";
    if (pair.second.is_bool()) {
      stream << (pair.second.bool_value() ? "1" : "0");
    }
    else if (!pair.second.is_null()) {
      stream << YaHTTP::Utility::encodeURL(HTTPConnector::asString(pair.second), false);
    }
    stream << "&";
  }

  return stream.str().substr(0, stream.str().size() - 1); // snip the trailing &
}

// builds our request (near-restful)
void HTTPConnector::restful_requestbuilder(const std::string& method, const Json& parameters, YaHTTP::Request& req)
{
  std::stringstream ss;
  std::string sparam;
  std::string verb;

  // special names are qname, name, zonename, kind, others go to headers

  ss << d_url;

  ss << "/" << method;

  // add the url components, if found, in following order.
  // id must be first due to the fact that the qname/name can be empty

  addUrlComponent(parameters, "id", ss);
  addUrlComponent(parameters, "domain_id", ss);
  addUrlComponent(parameters, "zonename", ss);
  addUrlComponent(parameters, "qname", ss);
  addUrlComponent(parameters, "name", ss);
  addUrlComponent(parameters, "kind", ss);
  addUrlComponent(parameters, "qtype", ss);

  // set the correct type of request based on method
  if (method == "activateDomainKey" || method == "deactivateDomainKey" || method == "publishDomainKey" || method == "unpublishDomainKey") {
    // create an empty post
    req.preparePost();
    verb = "POST";
  }
  else if (method == "setTSIGKey") {
    req.POST()["algorithm"] = parameters["algorithm"].string_value();
    req.POST()["content"] = parameters["content"].string_value();
    req.preparePost();
    verb = "PATCH";
  }
  else if (method == "deleteTSIGKey") {
    verb = "DELETE";
  }
  else if (method == "addDomainKey") {
    const Json& param = parameters["key"];
    req.POST()["flags"] = asString(param["flags"]);
    req.POST()["active"] = (param["active"].bool_value() ? "1" : "0");
    req.POST()["published"] = (param["published"].bool_value() ? "1" : "0");
    req.POST()["content"] = param["content"].string_value();
    req.preparePost();
    verb = "PUT";
  }
  else if (method == "superMasterBackend") {
    std::stringstream ss2;
    addUrlComponent(parameters, "ip", ss);
    addUrlComponent(parameters, "domain", ss);
    // then we need to serialize rrset payload into POST
    for (size_t index = 0; index < parameters["nsset"].array_items().size(); index++) {
      ss2 << buildMemberListArgs("nsset[" + std::to_string(index) + "]", parameters["nsset"][index]) << "&";
    }
    req.body = ss2.str().substr(0, ss2.str().size() - 1);
    req.headers["content-type"] = "application/x-www-form-urlencoded; charset=utf-8";
    req.headers["content-length"] = std::to_string(req.body.size());
    verb = "POST";
  }
  else if (method == "createSlaveDomain") {
    addUrlComponent(parameters, "ip", ss);
    addUrlComponent(parameters, "domain", ss);
    if (!parameters["account"].is_null() && parameters["account"].is_string()) {
      req.POST()["account"] = parameters["account"].string_value();
    }
    req.preparePost();
    verb = "PUT";
  }
  else if (method == "replaceRRSet") {
    std::stringstream ss2;
    for (size_t index = 0; index < parameters["rrset"].array_items().size(); index++) {
      ss2 << buildMemberListArgs("rrset[" + std::to_string(index) + "]", parameters["rrset"][index]) << "&";
    }
    req.body = ss2.str().substr(0, ss2.str().size() - 1); // remove trailing &
    req.headers["content-type"] = "application/x-www-form-urlencoded; charset=utf-8";
    req.headers["content-length"] = std::to_string(req.body.size());
    verb = "PATCH";
  }
  else if (method == "feedRecord") {
    addUrlComponent(parameters, "trxid", ss);
    req.body = buildMemberListArgs("rr", parameters["rr"]);
    req.headers["content-type"] = "application/x-www-form-urlencoded; charset=utf-8";
    req.headers["content-length"] = std::to_string(req.body.size());
    verb = "PATCH";
  }
  else if (method == "feedEnts") {
    std::stringstream ss2;
    addUrlComponent(parameters, "trxid", ss);
    for (const auto& param : parameters["nonterm"].array_items()) {
      ss2 << "nonterm[]=" << YaHTTP::Utility::encodeURL(param.string_value(), false) << "&";
    }
    for (const auto& param : parameters["auth"].array_items()) {
      ss2 << "auth[]=" << (param["auth"].bool_value() ? "1" : "0") << "&";
    }
    req.body = ss2.str().substr(0, ss2.str().size() - 1);
    req.headers["content-type"] = "application/x-www-form-urlencoded; charset=utf-8";
    req.headers["content-length"] = std::to_string(req.body.size());
    verb = "PATCH";
  }
  else if (method == "feedEnts3") {
    std::stringstream ss2;
    addUrlComponent(parameters, "domain", ss);
    addUrlComponent(parameters, "trxid", ss);
    ss2 << "times=" << parameters["times"].int_value() << "&salt=" << YaHTTP::Utility::encodeURL(parameters["salt"].string_value(), false) << "&narrow=" << (parameters["narrow"].bool_value() ? 1 : 0) << "&";
    for (const auto& param : parameters["nonterm"].array_items()) {
      ss2 << "nonterm[]=" << YaHTTP::Utility::encodeURL(param.string_value(), false) << "&";
    }
    for (const auto& param : parameters["auth"].array_items()) {
      ss2 << "auth[]=" << (param["auth"].bool_value() ? "1" : "0") << "&";
    }
    req.body = ss2.str().substr(0, ss2.str().size() - 1);
    req.headers["content-type"] = "application/x-www-form-urlencoded; charset=utf-8";
    req.headers["content-length"] = std::to_string(req.body.size());
    verb = "PATCH";
  }
  else if (method == "startTransaction") {
    addUrlComponent(parameters, "domain", ss);
    addUrlComponent(parameters, "trxid", ss);
    req.preparePost();
    verb = "POST";
  }
  else if (method == "commitTransaction" || method == "abortTransaction") {
    addUrlComponent(parameters, "trxid", ss);
    req.preparePost();
    verb = "POST";
  }
  else if (method == "setDomainMetadata") {
    // copy all metadata values into post
    std::stringstream ss2;
    // this one has values too
    if (parameters["value"].is_array()) {
      for (const auto& val : parameters["value"].array_items()) {
        ss2 << "value[]=" << YaHTTP::Utility::encodeURL(val.string_value(), false) << "&";
      }
    }
    req.body = ss2.str().substr(0, ss2.str().size() - 1);
    req.headers["content-type"] = "application/x-www-form-urlencoded; charset=utf-8";
    req.headers["content-length"] = std::to_string(req.body.size());
    verb = "PATCH";
  }
  else if (method == "removeDomainKey") {
    // this one is delete
    verb = "DELETE";
  }
  else if (method == "setNotified") {
    req.POST()["serial"] = asString(parameters["serial"]);
    req.preparePost();
    verb = "PATCH";
  }
  else if (method == "setStale") {
    req.preparePost();
    verb = "PATCH";
  }
  else if (method == "setFresh") {
    req.preparePost();
    verb = "PATCH";
  }
  else if (method == "directBackendCmd") {
    req.POST()["query"] = parameters["query"].string_value();
    req.preparePost();
    verb = "POST";
  }
  else if (method == "searchRecords" || method == "searchComments") {
    req.GET()["pattern"] = parameters["pattern"].string_value();
    req.GET()["maxResults"] = std::to_string(parameters["maxResults"].int_value());
    verb = "GET";
  }
  else if (method == "getAllDomains") {
    req.GET()["includeDisabled"] = (parameters["include_disabled"].bool_value() ? "true" : "false");
    verb = "GET";
  }
  else {
    // perform normal get
    verb = "GET";
  }

  // put everything else into headers
  for (const auto& pair : parameters.object_items()) {
    std::string member = pair.first;
    // whitelist header parameters
    if ((member == "trxid" || member == "local" || member == "remote" || member == "real-remote" || member == "zone-id")) {
      std::string hdr = "x-remotebackend-" + member;
      req.headers[hdr] = asString(pair.second);
    }
  };

  // finally add suffix and store url
  ss << d_url_suffix;

  req.setup(verb, ss.str());
  req.headers["accept"] = "application/json";
}

void HTTPConnector::post_requestbuilder(const Json& input, YaHTTP::Request& req)
{
  if (this->d_post_json) {
    std::string out = input.dump();
    req.setup("POST", d_url);
    // simple case, POST JSON into url. nothing fancy.
    req.headers["Content-Type"] = "text/javascript; charset=utf-8";
    req.headers["Content-Length"] = std::to_string(out.size());
    req.headers["accept"] = "application/json";
    req.body = out;
  }
  else {
    std::stringstream url;
    std::stringstream content;
    // call url/method.suffix
    url << d_url << "/" << input["method"].string_value() << d_url_suffix;
    req.setup("POST", url.str());
    // then build content
    req.POST()["parameters"] = input["parameters"].dump();
    req.preparePost();
    req.headers["accept"] = "application/json";
  }
}

int HTTPConnector::send_message(const Json& input)
{
  int rv = 0;
  int ec = 0;
  int fd = 0;

  std::vector<std::string> members;
  std::string method;
  std::ostringstream out;

  // perform request
  YaHTTP::Request req;

  if (d_post) {
    post_requestbuilder(input, req);
  }
  else {
    restful_requestbuilder(input["method"].string_value(), input["parameters"], req);
  }

  rv = -1;
  req.headers["connection"] = "Keep-Alive"; // see if we can streamline requests (not needed, strictly speaking)

  out << req;

  // try sending with current socket, if it fails retry with new socket
  if (this->d_socket != nullptr) {
    fd = this->d_socket->getHandle();
    // there should be no data waiting
    if (waitForRWData(fd, true, 0, 1000) < 1) {
      try {
        d_socket->writenWithTimeout(out.str().c_str(), out.str().size(), timeout);
        rv = 1;
      }
      catch (NetworkError& ne) {
        g_log << Logger::Error << "While writing to HTTP endpoint " << d_addr.toStringWithPort() << ": " << ne.what() << std::endl;
      }
      catch (...) {
        g_log << Logger::Error << "While writing to HTTP endpoint " << d_addr.toStringWithPort() << ": exception caught" << std::endl;
      }
    }
  }

  if (rv == 1) {
    return rv;
  }

  this->d_socket.reset();

  // connect using tcp
  struct addrinfo* gAddr = nullptr;
  struct addrinfo* gAddrPtr = nullptr;
  struct addrinfo hints{};
  std::string sPort = std::to_string(d_port);
  memset(&hints, 0, sizeof hints);
  hints.ai_family = AF_UNSPEC;
  hints.ai_flags = AI_ADDRCONFIG;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_protocol = IPPROTO_TCP;
  if ((ec = getaddrinfo(d_host.c_str(), sPort.c_str(), &hints, &gAddr)) == 0) {
    // try to connect to each address.
    gAddrPtr = gAddr;

    while (gAddrPtr != nullptr) {
      try {
        d_socket = std::make_unique<Socket>(gAddrPtr->ai_family, gAddrPtr->ai_socktype, gAddrPtr->ai_protocol);
        d_addr.setSockaddr(gAddrPtr->ai_addr, gAddrPtr->ai_addrlen);
        d_socket->connect(d_addr);
        d_socket->setNonBlocking();
        d_socket->writenWithTimeout(out.str().c_str(), out.str().size(), timeout);
        rv = 1;
      }
      catch (NetworkError& ne) {
        g_log << Logger::Error << "While writing to HTTP endpoint " << d_addr.toStringWithPort() << ": " << ne.what() << std::endl;
      }
      catch (...) {
        g_log << Logger::Error << "While writing to HTTP endpoint " << d_addr.toStringWithPort() << ": exception caught" << std::endl;
      }

      if (rv > -1) {
        break;
      }
      d_socket.reset();
      gAddrPtr = gAddrPtr->ai_next;
    }
    freeaddrinfo(gAddr);
  }
  else {
    g_log << Logger::Error << "Unable to resolve " << d_host << ": " << gai_strerror(ec) << std::endl;
  }

  return rv;
}

int HTTPConnector::recv_message(Json& output)
{
  YaHTTP::AsyncResponseLoader arl;
  YaHTTP::Response resp;

  if (d_socket == nullptr) {
    return -1; // cannot receive :(
  }
  std::array<char, 4096> buffer{};
  time_t time0 = 0;

  arl.initialize(&resp);

  try {
    time0 = time(nullptr);
    while (!arl.ready() && (labs(time(nullptr) - time0) <= timeout)) {
      auto readBytes = d_socket->readWithTimeout(buffer.data(), buffer.size(), timeout);
      if (readBytes == 0) {
        throw NetworkError("EOF while reading");
      }
      arl.feed(std::string(buffer.data(), readBytes));
    }
    // timeout occurred.
    if (!arl.ready()) {
      throw NetworkError("timeout");
    }
  }
  catch (NetworkError& ne) {
    d_socket.reset();
    throw PDNSException("While reading from HTTP endpoint " + d_addr.toStringWithPort() + ": " + ne.what());
  }
  catch (...) {
    d_socket.reset();
    throw PDNSException("While reading from HTTP endpoint " + d_addr.toStringWithPort() + ": unknown error");
  }

  arl.finalize();

  if ((resp.status < 200 || resp.status >= 400) && resp.status != 404) {
    // bad.
    throw PDNSException("Received unacceptable HTTP status code " + std::to_string(resp.status) + " from HTTP endpoint " + d_addr.toStringWithPort());
  }

  std::string err;
  output = Json::parse(resp.body, err);
  if (output != nullptr) {
    return static_cast<int>(resp.body.size());
  }
  g_log << Logger::Error << "Cannot parse JSON reply: " << err << endl;

  return -1;
}