#include <fc/network/udp_socket.hpp>
#include <fc/network/ip.hpp>
#include <fc/network/resolve.hpp>
#include <fc/exception/exception.hpp>
#include <fc/log/gelf_appender.hpp>
#include <fc/reflect/variant.hpp>
#include <fc/thread/thread.hpp>
#include <fc/variant.hpp>
#include <fc/io/json.hpp>
#include <fc/crypto/city.hpp>
#include <fc/compress/zlib.hpp>

#include <boost/lexical_cast.hpp>
#include <iomanip>
#include <iostream>
#include <queue>
#include <sstream>
#include <iostream>

namespace fc 
{

  class gelf_appender::impl : public retainable
  {
  public:
    config                     cfg;
    optional<ip::endpoint>     gelf_endpoint;
    udp_socket                 gelf_socket;

    impl(const config& c) : 
      cfg(c)
    {
    }

    ~impl()
    {
    }
  };

  gelf_appender::gelf_appender(const variant& args) :
    my( new impl( args.as<config>( FC_MAX_LOG_OBJECT_DEPTH ) ) )
  {
    try
    {
      try
      {
        // if it's a numeric address:port, this will parse it
        my->gelf_endpoint = ip::endpoint::from_string(my->cfg.endpoint);
      }
      catch (...)
      {
      }
      if (!my->gelf_endpoint)
      {
        // couldn't parse as a numeric ip address, try resolving as a DNS name.  
        // This can yield, so don't do it in the catch block above
        string::size_type colon_pos = my->cfg.endpoint.find(':');
        try
        {
          uint16_t port = boost::lexical_cast<uint16_t>(my->cfg.endpoint.substr(colon_pos + 1, my->cfg.endpoint.size()));

          string hostname = my->cfg.endpoint.substr( 0, colon_pos );
          std::vector<ip::endpoint> endpoints = resolve(hostname, port);
          if (endpoints.empty())
              FC_THROW_EXCEPTION(unknown_host_exception, "The host name can not be resolved: ${hostname}", 
                                 ("hostname", hostname));
          my->gelf_endpoint = endpoints.back();
        }
        catch (const boost::bad_lexical_cast&)
        {
          FC_THROW("Bad port: ${port}", ("port", my->cfg.endpoint.substr(colon_pos + 1, my->cfg.endpoint.size())));
        }
      }

      if (my->gelf_endpoint)
        my->gelf_socket.open();
    }
    catch (...)
    {
      std::cerr << "error opening GELF socket to endpoint ${endpoint}" << my->cfg.endpoint << "\n";
    }
  }

  gelf_appender::~gelf_appender()
  {}

  void gelf_appender::log(const log_message& message)
  {
    if (!my->gelf_endpoint)
      return;

    log_context context = message.get_context();

    mutable_variant_object gelf_message;
    gelf_message["version"] = "1.1";
    gelf_message["host"] = my->cfg.host;
    gelf_message["short_message"] = format_string( message.get_format(), message.get_data(), my->cfg.max_object_depth );
    
    gelf_message["timestamp"] = context.get_timestamp().time_since_epoch().count() / 1000000.;

    switch (context.get_log_level())
    {
    case log_level::debug:
      gelf_message["level"] = 7; // debug
      break;
    case log_level::info:
      gelf_message["level"] = 6; // info
      break;
    case log_level::warn:
      gelf_message["level"] = 4; // warning
      break;
    case log_level::error:
      gelf_message["level"] = 3; // error
      break;
    case log_level::all:
    case log_level::off:
      // these shouldn't be used in log messages, but do something deterministic just in case
      gelf_message["level"] = 6; // info
      break;
    }

    if (!context.get_context().empty())
      gelf_message["context"] = context.get_context();
    gelf_message["_line"] = context.get_line_number();
    gelf_message["_file"] = context.get_file();
    gelf_message["_method_name"] = context.get_method();
    gelf_message["_thread_name"] = context.get_thread_name();
    if (!context.get_task_name().empty())
      gelf_message["_task_name"] = context.get_task_name();

    string gelf_message_as_string;
    try
    {
       gelf_message_as_string = json::to_string(gelf_message);
    }
    catch( const fc::assert_exception& e )
    {
       gelf_message_as_string = "{\"level\":3,\"short_message\":\"ERROR while generating log message\"}";
    }
    gelf_message_as_string = zlib_compress(gelf_message_as_string);
    
    // graylog2 expects the zlib header to be 0x78 0x9c
    // but miniz.c generates 0x78 0x01 (indicating 
    // low compression instead of default compression)
    // so change that here
    assert(gelf_message_as_string[0] == (char)0x78);
    if (gelf_message_as_string[1] == (char)0x01 ||
        gelf_message_as_string[1] == (char)0xda)
      gelf_message_as_string[1] = (char)0x9c;
    assert(gelf_message_as_string[1] == (char)0x9c);

    // packets are sent by UDP, and they tend to disappear if they
    // get too large.  It's hard to find any solid numbers on how
    // large they can be before they get dropped -- datagrams can
    // be up to 64k, but anything over 512 is not guaranteed.
    // You can play with this number, intermediate values like
    // 1400 and 8100 are likely to work on most intranets.
    const unsigned max_payload_size = 512;

    if (gelf_message_as_string.size() <= max_payload_size)
    {
      // no need to split
      std::shared_ptr<char> send_buffer(new char[gelf_message_as_string.size()],
                                        [](char* p){ delete[] p; });
      memcpy(send_buffer.get(), gelf_message_as_string.c_str(), 
             gelf_message_as_string.size());

      my->gelf_socket.send_to(send_buffer, gelf_message_as_string.size(), 
                              *my->gelf_endpoint);
    }
    else
    {
      // split the message
      // we need to generate an 8-byte ID for this message.  
      // city hash should do
      uint64_t message_id = city_hash64(gelf_message_as_string.c_str(), gelf_message_as_string.size());
      const unsigned header_length = 2 /* magic */ + 8 /* msg id */ + 1 /* seq */ + 1 /* count */;
      const unsigned body_length = max_payload_size - header_length;
      unsigned total_number_of_packets = (gelf_message_as_string.size() + body_length - 1) / body_length;
      unsigned bytes_sent = 0;
      unsigned number_of_packets_sent = 0;
      while (bytes_sent < gelf_message_as_string.size())
      {
        unsigned bytes_to_send = std::min((unsigned)gelf_message_as_string.size() - bytes_sent, 
                                          body_length);
                                               
        std::shared_ptr<char> send_buffer(new char[max_payload_size], 
                                          [](char* p){ delete[] p; });
        char* ptr = send_buffer.get();
        // magic number for chunked message
        *(unsigned char*)ptr++ = 0x1e;
        *(unsigned char*)ptr++ = 0x0f;

        // message id
        memcpy(ptr, (char*)&message_id, sizeof(message_id));
        ptr += sizeof(message_id);

        *(unsigned char*)(ptr++) = number_of_packets_sent;
        *(unsigned char*)(ptr++) = total_number_of_packets;
        memcpy(ptr, gelf_message_as_string.c_str() + bytes_sent, 
               bytes_to_send);
        my->gelf_socket.send_to(send_buffer, header_length + bytes_to_send, 
                                *my->gelf_endpoint);
        ++number_of_packets_sent;
        bytes_sent += bytes_to_send;
      }
      assert(number_of_packets_sent == total_number_of_packets);
    }
  }
} // fc
