#include "https.h"

#include "config.h"
#include "error.h"
#include "server.h"
#include "response.h"
#include "websocket.h"

#include "libreichwein/file.h"

#include <openssl/ssl.h>
#include <openssl/crypto.h>

#include <boost/asio/buffer.hpp>
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/websocket.hpp>
#include <boost/beast/websocket/ssl.hpp>
#include <boost/asio/buffers_iterator.hpp>
#include <boost/asio/dispatch.hpp>
#include <boost/asio/ssl/context.hpp>
#include <boost/beast/ssl.hpp>
#include <boost/asio/strand.hpp>
#include <boost/config.hpp>

#include <algorithm>
#include <cstddef>
#include <cstdlib>
#include <filesystem>
#include <functional>
#include <iostream>
#include <memory>
#include <optional>
#include <string>
#include <thread>
#include <vector>

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

namespace {

//------------------------------------------------------------------------------

// Handles an HTTP server connection
class session : public std::enable_shared_from_this<session>
{
 boost::asio::io_context& ioc_;
 beast::ssl_stream<beast::tcp_stream> stream_;
 beast::flat_buffer buffer_;
 Server& m_server;
 std::optional<http::request_parser<http::string_body>> parser_; // need to reset parser every time, no other mechanism currently
 http::request<http::string_body> req_;
 std::shared_ptr<response_type> res_; // std::shared_ptr<void>

 void handle_request(::Server& server, request_type&& req)
 {
  beast::get_lowest_layer(stream_).expires_after(std::chrono::seconds(300)); // timeout on write by server much longer than read timeout from client
  auto sp = std::make_shared<response_type>(generate_response(req, server));

  res_ = sp;

  // Write the response
  http::async_write(
      stream_,
      *sp,
      beast::bind_front_handler(
          &session::on_write,
          shared_from_this(),
          sp->need_eof()));
 }
public:
    // Take ownership of the socket
    explicit
    session(
        boost::asio::io_context& ioc,
        tcp::socket&& socket,
        ssl::context& ctx,
        Server& server):
         ioc_(ioc),
         stream_(std::move(socket), ctx),
         m_server(server)
    {
    }

    // Start the asynchronous operation
    void
    run()
    {
        // We need to be executing within a strand to perform async operations
        // on the I/O objects in this session.
        net::dispatch(
            stream_.get_executor(),
            beast::bind_front_handler(
                &session::on_run,
                shared_from_this()));
    }

    void
    on_run()
    {
        // Set the timeout.
        beast::get_lowest_layer(stream_).expires_after(
            std::chrono::seconds(30));

        // Perform the SSL handshake
        stream_.async_handshake(
            ssl::stream_base::server,
            beast::bind_front_handler(
                &session::on_handshake,
                shared_from_this()));
    }

    void
    on_handshake(
                 beast::error_code ec
                 )
    {
        if(ec)
            return fail(ec, "https handshake");

        do_read();
    }

    void
    do_read()
    {
        // Make the request empty before reading,
        // otherwise the operation behavior is undefined.
        req_ = {};
       
        // this is the way to reset the parser. it's necessary.
        // https://github.com/boostorg/beast/issues/927
        parser_.emplace();
        parser_->body_limit(1000000000); // 1GB limit

        // Set the timeout.
        beast::get_lowest_layer(stream_).expires_after(std::chrono::seconds(30));

        // Read a request
        http::async_read(stream_, buffer_, *parser_,
            beast::bind_front_handler(
                &session::on_read,
                shared_from_this()));
    }

    void
    on_read(
        beast::error_code ec,
        std::size_t bytes_transferred)
    {
        boost::ignore_unused(bytes_transferred);

        // This means they closed the connection
        if (ec == http::error::end_of_stream)
            return do_close();

        if (ec == http::error::partial_message)
         return; // ignore

        if (ec)
            return fail(ec, "https read");

        req_ = parser_->get();

        if (websocket::is_upgrade(req_))
        {
         beast::get_lowest_layer(stream_).expires_never();
         std::make_shared<websocket_session>(ioc_, std::move(stream_))->do_accept_in(parser_->release());
         return;
        }
        
        // Send the response
        handle_request(m_server, std::move(req_));
    }

    void
    on_write(
        bool close,
        beast::error_code ec,
        std::size_t bytes_transferred
        )
    {
        boost::ignore_unused(bytes_transferred);

        if(ec)
            return fail(ec, "https write");

        if(close)
        {
            // This means we should close the connection, usually because
            // the response indicated the "Connection: close" semantic.
            return do_close();
        }

        // We're done with the response so delete it
        res_ = nullptr;

        // Read another request
        do_read();
    }

    void
    do_close()
    {
        // Set the timeout.
        beast::get_lowest_layer(stream_).expires_after(std::chrono::seconds(30));

        // Perform the SSL shutdown
        stream_.async_shutdown(
            beast::bind_front_handler(
                &session::on_shutdown,
                shared_from_this()));
    }

    void
    on_shutdown(beast::error_code ec)
    {
        if(ec)
            return fail(ec, "https shutdown");

        // At this point the connection is closed gracefully
    }
};

//------------------------------------------------------------------------------

// Accepts incoming connections and launches the sessions
class listener : public std::enable_shared_from_this<listener>
{
    net::io_context& ioc_;
    ssl::context& ctx_;
    tcp::acceptor acceptor_;
    ::Server& m_server;

public:
    listener(
        net::io_context& ioc,
        ssl::context& ctx,
        tcp::endpoint endpoint,
        Server& server) :
        ioc_(ioc),
        ctx_(ctx),
        acceptor_(ioc),
        m_server(server)
    {
        beast::error_code ec;

        // Open the acceptor
        acceptor_.open(endpoint.protocol(), ec);
        if(ec)
        {
            fail(ec, "https open");
            return;
        }

        // Allow address reuse
        acceptor_.set_option(net::socket_base::reuse_address(true), ec);
        if(ec)
        {
            fail(ec, "https set_option");
            return;
        }

        // Bind to the server address
        acceptor_.bind(endpoint, ec);
        if(ec)
        {
            fail(ec, "https bind");
            return;
        }

        // Start listening for connections
        acceptor_.listen(
            net::socket_base::max_listen_connections, ec);
        if(ec)
        {
            fail(ec, "https listen");
            return;
        }
    }

    // Start accepting incoming connections
    void
    run()
    {
        do_accept();
    }

private:
    void
    do_accept()
    {
        // The new connection gets its own strand
        acceptor_.async_accept(
            net::make_strand(ioc_),
            beast::bind_front_handler(
                &listener::on_accept,
                shared_from_this()));
    }

    void
    on_accept(beast::error_code ec, tcp::socket socket)
    {
        if(ec)
        {
            fail(ec, "https accept");
        }
        else
        {
            // Create the session and run it
            std::make_shared<session>(
                ioc_,
                std::move(socket),
                ctx_,
                m_server)->run();
        }

        // Accept another connection
        do_accept();
    }
};

/*  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()));
}

int ServerNameError(SSL *s, HTTPS::Server::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
}

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;
 }
}

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

} // anonymous namespace
//------------------------------------------------------------------------------

namespace HTTPS {

Server::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::~Server()
{
}

void Server::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 Server::start()
{
 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
 std::make_shared<listener>(
     m_ioc,
     *m_ctx[""],
     tcp::endpoint{address, port},
     *this)->run();

 return EXIT_SUCCESS;
}

} // namespace HTTPS