#include <boost/beast/version.hpp>

#include <boost/asio/ip/tcp.hpp>
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/beast/ssl.hpp>
#include <boost/asio/dispatch.hpp>
#include <boost/asio/signal_set.hpp>
#include <boost/asio/strand.hpp>
#include <boost/config.hpp>

#include <exception>
#include <filesystem>
#include <functional>
#include <iostream>
#include <thread>
#include <vector>

#include <libreichwein/file.h>

#include "server.h"

#include "http.h"
#include "privileges.h"
#include "statistics.h"

namespace beast = boost::beast;         // from <boost/beast.hpp>
namespace http = beast::http;           // from <boost/beast/http.hpp>
namespace net = boost::asio;            // from <boost/asio.hpp>
namespace ssl = boost::asio::ssl;       // from <boost/asio/ssl.hpp>
using tcp = boost::asio::ip::tcp;       // from <boost/asio/ip/tcp.hpp>
namespace fs = std::filesystem;
using namespace Reichwein;

const std::string Server::VersionString{ "Reichwein.IT Webserver "s + std::string{VERSION} };

namespace {
 const int32_t stats_timer_seconds { 24 * 60 * 60 }; // save stats once a day

 std::string unbracketed(const std::string& s)
 {
  if (s.size() >= 2 && s.front() == '[' && s.back() == ']') {
   return s.substr(1, s.size() - 2);
  } else {
   return s;
  }
 }

} // anonymous namespace

Server::Server(Config& config, boost::asio::io_context& ioc, const Socket& socket, plugins_container_type& plugins, Statistics& statistics)
 : m_config(config)
 , m_ioc(ioc)
 , m_socket(socket)
 , m_plugins(plugins)
 , m_statistics(statistics)
{
}

Server::~Server()
{
}

Config& Server::GetConfig()
{
 return m_config;
}

const Socket& Server::GetSocket()
{
 return m_socket;
}

plugin_type Server::GetPlugin(const std::string& name)
{
 try {
  return m_plugins.at(name);
 } catch (const std::out_of_range& ex) {
  std::cout << "Out of range at Server::GetPlugin(): " << name << std::endl;
  std::rethrow_exception(std::current_exception());
 } catch (...) {
  std::cout << "Unknown exception at Server::GetPlugin(): " << name << std::endl;
  std::rethrow_exception(std::current_exception());
 }
}

Statistics& Server::GetStatistics()
{
 return m_statistics;
}

namespace HTTP {

class Server: public ::Server
{
public:
 Server(Config& config, boost::asio::io_context& ioc, const Socket& socket, plugins_container_type& plugins, Statistics& statistics)
  : ::Server(config, ioc, socket, plugins, statistics)
 {
 }

 ~Server() override
 {
 }

 int start() override
 {
  auto const address = net::ip::make_address(m_socket.address);
  auto const port = static_cast<unsigned short>(std::atoi(m_socket.port.data()));

  // Create and launch a listening port
  make_listener(m_ioc, address, port, *this);

  return EXIT_SUCCESS;
 }
};

} // namespace HTTP

namespace {

/*  Load a signed certificate into the ssl context, and configure
    the context for use with a server.
*/
void load_server_certificate(boost::asio::ssl::context& ctx, const fs::path& cert_path, const fs::path& key_path)
{
 /*
     The certificate was generated from CMD.EXE on Windows 10 using:

     winpty openssl dhparam -out dh.pem 2048
     winpty openssl req -newkey rsa:4096 -sha256 -nodes -keyout key.pem -x509 -days 10000 -out cert.pem -subj "//C=DE\ST=BY\L=Munich\O=Reichwein\CN=reichwein.it"
 */

 std::string const dh =
     "-----BEGIN DH PARAMETERS-----\n"
     "MIIBCAKCAQEArzQc5mpm0Fs8yahDeySj31JZlwEphUdZ9StM2D8+Fo7TMduGtSi+\n"
     "/HRWVwHcTFAgrxVdm+dl474mOUqqaz4MpzIb6+6OVfWHbQJmXPepZKyu4LgUPvY/\n"
     "4q3/iDMjIS0fLOu/bLuObwU5ccZmDgfhmz1GanRlTQOiYRty3FiOATWZBRh6uv4u\n"
     "tff4A9Bm3V9tLx9S6djq31w31Gl7OQhryodW28kc16t9TvO1BzcV3HjRPwpe701X\n"
     "oEEZdnZWANkkpR/m/pfgdmGPU66S2sXMHgsliViQWpDCYeehrvFRHEdR9NV+XJfC\n"
     "QMUk26jPTIVTLfXmmwU0u8vUkpR7LQKkwwIBAg==\n"
     "-----END DH PARAMETERS-----\n";
 
 ctx.set_options(
     boost::asio::ssl::context::default_workarounds |
     boost::asio::ssl::context::no_sslv2 |
     boost::asio::ssl::context::single_dh_use);

 std::string cert;
 if (cert_path.empty()) {
  // use dummy self signed certificate. Will be replaced by real
  // certificate if configured upon respective session
  cert =
   "-----BEGIN CERTIFICATE-----\n"
   "MIIDnTCCAoWgAwIBAgIULkYtO+2Ddeg+qLZ+aDQpmA5b4L0wDQYJKoZIhvcNAQEL\n"
   "BQAwXjELMAkGA1UEBhMCREUxEDAOBgNVBAgMB0JhdmFyaWExDzANBgNVBAcMBk11\n"
   "bmljaDEVMBMGA1UECgwMUmVpY2h3ZWluIElUMRUwEwYDVQQDDAxyZWljaHdlaW4u\n"
   "aXQwHhcNMjAwNDA1MDgwNzIyWhcNNDcwODIyMDgwNzIyWjBeMQswCQYDVQQGEwJE\n"
   "RTEQMA4GA1UECAwHQmF2YXJpYTEPMA0GA1UEBwwGTXVuaWNoMRUwEwYDVQQKDAxS\n"
   "ZWljaHdlaW4gSVQxFTATBgNVBAMMDHJlaWNod2Vpbi5pdDCCASIwDQYJKoZIhvcN\n"
   "AQEBBQADggEPADCCAQoCggEBALJNb0WLbz+xP+YITMMk+eeK/SIOCRFs/9aZIAyK\n"
   "ParGauxa+8d25mlfJTAo6/G0h3sA240JHyNpOzVOogPU+v4dRWyGO0w5vHVD0caB\n"
   "rDb1eEfmLtqfKLLUL9iPDReUh6WAE7qoNDtfoT551uSMIae1cpPUduVTnSkEgw8k\n"
   "NjJSHYT800jSB2R+e7tJG3ErXDM63R3B8RbitZPoWACjpBxDT+Qrj0fBFS4AWw6b\n"
   "z09uitv0RrgI6CW7xRh3UAdRwEBGHiU6HTIthX6LNgez1UL0sfu1iZ22wNmYZP/S\n"
   "sL3b20WtSH9LN2PRJ4q3AGt6RMbmSGr65ljha9xkTFna0Y8CAwEAAaNTMFEwHQYD\n"
   "VR0OBBYEFKd5/MGFZUAUV502vJ/Kcswax8WVMB8GA1UdIwQYMBaAFKd5/MGFZUAU\n"
   "V502vJ/Kcswax8WVMA8GA1UdEwEB/wQFMAMBAf8wDQYJKoZIhvcNAQELBQADggEB\n"
   "AIBS4AfM7wiunQ2UZQQ5A0Un99+BLax9e+h11h/jGeJ+/9maY/E9MK6UG9LXoOv2\n"
   "z32Q7Ta2xKeRu6GC/qupwYJ0Xt3LENOfogsaNCAgxKlAN48LGlRyCTvzWsEMh28j\n"
   "RaelWonh2qQoiryKLVnRwrg8g1Bu4v+V437cIBmeZPxf0spEL9EVqlN+iS8plmel\n"
   "7/F4ULdybKGq39tgicuS7JhnY21ZzOFoq0bWnKBbAeTndmuROdb3pEppxW6pwu0q\n"
   "TFdMrSJE38kiQh2O9IchPQbTZ+Rdj0HE9NxStlrNr5bu6rjikRm50/G3JoXpzYdp\n"
   "AN4ZI2QZ6R6Y+TzDixKecNk=\n"
   "-----END CERTIFICATE-----\n"
   ;
 } else {
  cert = File::getFile(cert_path);
 }

 ctx.use_certificate_chain(
     boost::asio::buffer(cert.data(), cert.size()));

 std::string key;
 if (key_path == "") {
  // use dummy self signed key. Will be replaced by real
  // certificate if configured upon respective session
  key =
   "-----BEGIN PRIVATE KEY-----\n"
   "MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQCyTW9Fi28/sT/m\n"
   "CEzDJPnniv0iDgkRbP/WmSAMij2qxmrsWvvHduZpXyUwKOvxtId7ANuNCR8jaTs1\n"
   "TqID1Pr+HUVshjtMObx1Q9HGgaw29XhH5i7anyiy1C/Yjw0XlIelgBO6qDQ7X6E+\n"
   "edbkjCGntXKT1HblU50pBIMPJDYyUh2E/NNI0gdkfnu7SRtxK1wzOt0dwfEW4rWT\n"
   "6FgAo6QcQ0/kK49HwRUuAFsOm89Pborb9Ea4COglu8UYd1AHUcBARh4lOh0yLYV+\n"
   "izYHs9VC9LH7tYmdtsDZmGT/0rC929tFrUh/Szdj0SeKtwBrekTG5khq+uZY4Wvc\n"
   "ZExZ2tGPAgMBAAECggEBAK9bJKIa3dCgPB257/TEOtsTgJyrfROcRYkCk9iBZOC9\n"
   "v46wdIrZTwY2wtY4iMPwLoY0c7ijTfJ/nfFxYjmujyK4Gvz+jvcKmWQizP8TrRFo\n"
   "HWFo6o+slFQ8BspO9itIspd7/OtIXgY+qNBO959Sig7sjsEA5eXoc9pRS6vqizq0\n"
   "j4G/UO5Amr/l3ciEJiqMJgZsIVLDKaGlqFTymydSqkB8UHQYWK1kunQxhK4Ldycu\n"
   "hTooQE7tXM0zvoFVV6v1fldV5OFsZk2kPMNtvMO6ZEpOM4rNMlg+vJy8kB1fb3Gs\n"
   "iFE/DCUpZsMSserQMU9/hfrYlndgsFD5Sr1EVGEebhECgYEA1gc9qx+ugdhYTY5j\n"
   "tJDXjOsnw8KY/l/1y+mQ8XNJ9MVdBGy1WB+uWB4teiyJchV49gn2XlKUK2rcCBvZ\n"
   "vC5CwPmFi2t70JezQgnXtDlbR0bARPlRd741i4rBpD7hEiZNCTOd2HFBpUg/CGWN\n"
   "E4n1ksazBm6jvv3Jo6WAa07Z390CgYEA1USrFqmc/fKGQpTCdH0qYZv3hQtrb1TQ\n"
   "9YnrbhtaC0haPpintZKjvhU3tCd1fPuIDXtMAgaaKSyoGiE2aMvLxt1/eV08BkMi\n"
   "kGIss9poYNi5+6ZD9QAHmHJhzZtVGj8U5L8379XmwxAByiBRVVE8CW1X/e6+iJpz\n"
   "+CLgN+zEVlsCgYEAsuOAdtxXJm4meERwL8b0cvNF3Eh1Sf/42MPTAwzCntSrh3w5\n"
   "InvwY/RtPHWnN/ScksEG7BWHhLafTCPDHJdp8hNcvIhNB68UBDln0loyYePP5pag\n"
   "sj4IUSbb7SUlR989elhrMTKQlM5K6QDAJrmjyVdM4S5urL9A3wgAyzAvyP0CgYAO\n"
   "paGuc8WxdzebWQYl4/bGL2UHgSpGwid7xZYiwMQlZDm2dNuHz+NpCaICwHcEN243\n"
   "ptEojnWGAGgnK0LGXcDIDqxTlICr2W6FRgjV7Vkf1aKoUtn1+KOM58YpzdJBdDWm\n"
   "JC/eS+2GVhIZZLDRUDv0VcsmSIBTd3AhiZumm588YwKBgBZfNqfmHAwIP2pM1wml\n"
   "Ck3vaLLvonghj3iQW9CFJ/SqLOnfT4KJkFObR6oGbxY0RtXsCrmSqidIKgDd0Kkq\n"
   "L6QbHp2j3+16GBdmLNUJlfjBTNPJp69IDKztjeCX7/8JZs79p/LAv+I9Sh4lVw4O\n"
   "IrDprlB0yzP5zigcsAZeViYJ\n"
   "-----END PRIVATE KEY-----\n"
   ;
 } else {
  key = File::getFile(key_path);
 }
 ctx.use_private_key(
     boost::asio::buffer(key.data(), key.size()),
     boost::asio::ssl::context::file_format::pem);

 ctx.use_tmp_dh(
     boost::asio::buffer(dh.data(), dh.size()));
}

} // namespace

namespace HTTPS {

typedef std::unordered_map<std::string, std::shared_ptr<ssl::context>> ctx_type;

static const ssl::context_base::method tls_method {ssl::context::tlsv13};

int ServerNameError(SSL *s, ctx_type& ctx_map)
{
 std::shared_ptr<ssl::context> ctx{ctx_map.at("")};
 SSL_set_SSL_CTX(s, ctx->native_handle());
 return SSL_CLIENT_HELLO_SUCCESS; // OK for now
}

int servername_callback(SSL *s, int *al, void *arg)
{
 ctx_type& ctx_map = *(ctx_type*)arg;

 if (0) { // not really necessary
  int* numbers;
  size_t numbers_size;
  if (SSL_client_hello_get1_extensions_present(s, &numbers, &numbers_size) != 1) {
   std::cout << "Error on SSL_client_hello_get1_extensions_present" << std::endl;
   return ServerNameError(s, ctx_map);
  }
  bool server_name_available {false};
  for (size_t i = 0; i < numbers_size; i++)
   if (numbers[i] == 0)
    server_name_available = true;

  OPENSSL_free(numbers);

  if (!server_name_available) {
   std::cout << "Error: No server_name available at SSL_client_hello_get1_extensions_present" << std::endl;
   return ServerNameError(s, ctx_map);
  }
 }

 const unsigned char* data;
 size_t data_size;
 // 0 is server_name
 if (SSL_client_hello_get0_ext(s, 0, &data, &data_size) != 1) {
  std::cout << "Warning: Error on SSL_client_hello_get0_ext: servername not available. Using dummy ctx." << std::endl;
  return ServerNameError(s, ctx_map);
 }

 // SNI Server Name, See https://tools.ietf.org/html/rfc6066 (TODO: why are there 5 bytes header?)
 std::string server_name {std::string((const char*)data, (size_t)data_size)};
 if (server_name.size() >= 5 && server_name[0] == '\0')
  server_name = server_name.substr(5);

 server_name = unbracketed(server_name);

 auto it {ctx_map.find(server_name)};
 std::shared_ptr<ssl::context> ctx{};
 if (it != ctx_map.end()) {
  ctx = it->second;
 } else {
  std::cout << "Warning: server_name " << server_name << " (" << server_name.size() << ") not found in list of prepared contexts. Using dummy ctx." << std::endl;
  return ServerNameError(s, ctx_map);
 }

 SSL_set_SSL_CTX(s, ctx->native_handle());
 
 return SSL_CLIENT_HELLO_SUCCESS;
}

class Server: public ::Server
{
private:
 ctx_type m_ctx;

public:
 Server(Config& config, boost::asio::io_context& ioc, const Socket& socket, plugins_container_type& plugins, Statistics& statistics):
  ::Server(config, ioc, socket, plugins, statistics)
 {
  load_certificates(); // load initially
 }

 ~Server() override
 {
 }

 void load_certificates()
 {
  // initial dummy, before we can add specific ctx w/ certificate
  std::shared_ptr<ssl::context> ctx_dummy{std::make_shared<ssl::context>(tls_method)};
  load_server_certificate(*ctx_dummy, "", "");
  SSL_CTX_set_client_hello_cb(ctx_dummy->native_handle(), servername_callback, &m_ctx);
  m_ctx.emplace("", ctx_dummy);

  // import the real certificates
  for (const auto& serve_site: m_socket.serve_sites) {
   for (const auto& site: m_config.Sites()) {
    if (site.first == serve_site) {
     std::shared_ptr<ssl::context> ctx {std::make_shared<ssl::context>(tls_method)};

     std::cout << "Creating SSL context/cert for site " << serve_site << " on port " << m_socket.port << std::endl;

     load_server_certificate(*ctx, site.second.cert_path, site.second.key_path);
     SSL_CTX_set_client_hello_cb(ctx->native_handle(), servername_callback, &m_ctx);

     for (const auto& host: site.second.hosts) {
      std::cout << "  Adding Host " << host << std::endl;
      m_ctx.emplace(unbracketed(host), ctx);
     }
    }
   }
  }
 }

 int start() override
 {
  auto const address = net::ip::make_address(m_socket.address);
  auto const port = static_cast<unsigned short>(std::atoi(m_socket.port.data()));

  // Create and launch a listening port
  make_listener(m_ioc, *m_ctx[""], address, port, *this);

  return EXIT_SUCCESS;
 }

};

} // namespace HTTPS

int run_server(Config& config, plugins_container_type& plugins)
{
 Statistics stats(config.statistics_path());

 auto const threads = std::max<int>(1, config.Threads());

 boost::asio::io_context ioc{threads};

 // for now, just terminate on SIGINT, SIGHUP and SIGTERM
 boost::asio::signal_set signals(ioc, SIGINT, SIGTERM, SIGHUP);
 signals.async_wait([&](const boost::system::error_code& error, int signal_number){
                    std::cout << "Terminating via signal " << signal_number << std::endl;
                    ioc.stop();
                    });

 // Save stats once a day
 boost::asio::steady_timer stats_save_timer(ioc, boost::asio::chrono::seconds(stats_timer_seconds));
 std::function<void(const boost::system::error_code&)> stats_callback =
   [&](const boost::system::error_code& error){
         stats.save();
         stats_save_timer.expires_at(stats_save_timer.expires_at() + boost::asio::chrono::seconds(stats_timer_seconds));
         stats_save_timer.async_wait(stats_callback);
   };
 stats_save_timer.async_wait(stats_callback);

 std::vector<std::shared_ptr<Server>> servers;

 const auto& sockets {config.Sockets()};
 for (const auto& socket: sockets) {
  if (socket.protocol == SocketProtocol::HTTP) {
   servers.push_back(std::make_shared<HTTP::Server>(config, ioc, socket, plugins, stats));
  } else {
   servers.push_back(std::make_shared<HTTPS::Server>(config, ioc, socket, plugins, stats));
  }
  servers.back()->start();
 }

 // set UID, GID
 drop_privileges(config);

 // Run the I/O service on the requested number of threads
 std::vector<std::thread> v;
 v.reserve(threads - 1);
 for (auto i = threads - 1; i > 0; --i) {
  v.emplace_back(
  [&ioc]
  {
   ioc.run();
  });
 }
 ioc.run();

 for (auto& t: v) {
  t.join();
 }

 return EXIT_SUCCESS; 
}