#include "./resolver.h"
#include "./response.h"

#include <cassert>
#include <functional>
#include <event.h>
#include <unbound.h>
#include <unbound-event.h>
#include <iostream>
#include <cstring>
#include <utility>

#include <fcntl.h> /* for TSDNS */
#include <unistd.h>
#ifdef WIN32
	#include <ws2tcpip.h>
    #define SOCK_NONBLOCK (0)
    #define MSG_DONTWAIT (0)
#else
	#include <sys/socket.h>
#endif

using namespace std;
using namespace tc::dns;

Resolver::Resolver() { }

Resolver::~Resolver() {
	this->finalize();
}

void Resolver::destroy_tsdns_request(Resolver::tsdns_request *request) {
	assert(this_thread::get_id() == this->event.loop.get_id() || !this->event.loop_active);

	{
		lock_guard lock{this->request_lock};
		this->tsdns_requests.erase(std::find(this->tsdns_requests.begin(), this->tsdns_requests.end(), request), this->tsdns_requests.end());
	}

	if(request->event_read) {
		event_del_noblock(request->event_read);
		event_free(request->event_read);
		request->event_read = nullptr;
	}

	if(request->event_write) {
		event_del_noblock(request->event_write);
		event_free(request->event_write);
		request->event_write = nullptr;
	}

	if(request->timeout_event) {
		event_del_noblock(request->timeout_event);
		event_free(request->timeout_event);
		request->timeout_event = nullptr;
	}

	if(request->socket > 0) {
#ifndef WIN32
		::shutdown(request->socket, SHUT_RDWR);
#endif
		::close(request->socket);
		request->socket = 0;
	}

	delete request;
}

//---------------------- TSDNS
void Resolver::resolve_tsdns(const char *query, const sockaddr_storage& server_address, const std::chrono::microseconds& timeout, const tc::dns::Resolver::tsdns_callback_t &callback) {
	/* create the socket */
	auto socket = ::socket(server_address.ss_family, SOCK_STREAM | SOCK_NONBLOCK, 0);
	if(socket <= 0) {
		callback(ResultState::INITIALISATION_FAILED, -1, "failed to allocate socket: " + to_string(errno) + "/" + strerror(errno));
		return;
	}

#ifdef WIN32
	u_long enabled = 0;
    auto non_block_rs = ioctlsocket(this->_socket, FIONBIO, &enabled);
    if (non_block_rs != NO_ERROR) {
    	::close(socket);
        callback(ResultState::INITIALISATION_FAILED, -2, "failed to enable nonblock: " + to_string(errno) + "/" + strerror(errno));
		return;
    }
#endif

	int opt = 1;
	setsockopt(socket, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(int));

	auto request = new tsdns_request{};

	request->resolver = this;
	request->callback = callback;
	request->socket = socket;
	request->timeout_event = evtimer_new(this->event.base, [](evutil_socket_t, short, void *_request) {
		auto request = static_cast<tsdns_request*>(_request);
		request->resolver->evtimer_tsdns_callback(request);
	}, request);

	request->event_read = event_new(this->event.base, socket, EV_READ | EV_PERSIST, [](evutil_socket_t, short, void *_request){
		auto request = static_cast<tsdns_request*>(_request);
		request->resolver->event_tsdns_read(request);
	}, request);
	request->event_write = event_new(this->event.base, socket, EV_WRITE, [](evutil_socket_t, short, void *_request){
		auto request = static_cast<tsdns_request*>(_request);
		request->resolver->event_tsdns_write(request);
	}, request);

	if(!request->timeout_event || !request->event_write || !request->event_read) {
		callback(ResultState::INITIALISATION_FAILED, -3, "");
		this->destroy_tsdns_request(request);
		return;
	}

	request->write_buffer = query;
	request->write_buffer += "\n\r\r\r\n";

	int result = ::connect(socket, reinterpret_cast<const sockaddr *> (&server_address), sizeof(server_address));
	if (result < 0) {
#ifdef WIN32
		auto error = WSAGetLastError();

        if(error != WSAEWOULDBLOCK) {
        	/*
        	 * TODO!
            wchar_t *s = nullptr;
            FormatMessageW(
                    FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                    nullptr,
                    error,
                    MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                    (LPWSTR)&s,
                    0,
                    nullptr
            );
            fprintf(stdout, "Connect failed with code %d. Error: %ld/%S\n", result, error, s);
            LocalFree(s);
            */

			callback(ResultState::TSDNS_CONNECTION_FAIL, -1, "Failed to connect");
			this->destroy_tsdns_request(request);
        }
#else
		if(errno != EINPROGRESS) {
			callback(ResultState::TSDNS_CONNECTION_FAIL, -1, "Failed to connect with code: " + to_string(errno) + "/" + strerror(errno));
			this->destroy_tsdns_request(request);
			return;
		}
#endif
	}

	event_add(request->event_write, nullptr);
	event_add(request->event_read, nullptr);

	{
		auto seconds = chrono::floor<chrono::seconds>(timeout);
		auto microseconds = chrono::ceil<chrono::microseconds>(timeout - seconds);

		timeval tv{seconds.count(), microseconds.count()};
		auto errc = event_add(request->timeout_event, &tv);

		//TODO: Check for error
	}

	{
		lock_guard lock{this->request_lock};
		this->tsdns_requests.push_back(request);
	}

	/* Activate the event loop */
	this->event.condition.notify_one();
}

void Resolver::evtimer_tsdns_callback(Resolver::tsdns_request *request) {
	request->callback(ResultState::DNS_TIMEOUT, 0, "");
	this->destroy_tsdns_request(request);
}

void Resolver::event_tsdns_read(Resolver::tsdns_request *request) {
	int64_t buffer_length = 1024;
	char buffer[1024];

	buffer_length = recv(request->socket, buffer, (int) buffer_length, MSG_DONTWAIT);
	if(buffer_length < 0) {
#ifdef WIN32
		auto error = WSAGetLastError();
        if(error != WSAEWOULDBLOCK)
            return;
		request->callback(ResultState::TSDNS_CONNECTION_FAIL, -2, "read failed: " + to_string(error));
#else
		if(errno == EAGAIN)
			return;
		request->callback(ResultState::TSDNS_CONNECTION_FAIL, -2, "read failed: " + to_string(errno) + "/" + strerror(errno));
#endif
		this->destroy_tsdns_request(request);
		return;
	} else if(buffer_length == 0) {
		if(request->read_buffer.empty()) {
			request->callback(ResultState::TSDNS_EMPTY_RESPONSE, 0, "");
		} else {
			request->callback(ResultState::SUCCESS, 0, request->read_buffer);
		}
		this->destroy_tsdns_request(request);
		return;
	}

	lock_guard lock{request->buffer_lock};
	request->read_buffer.append(buffer, buffer_length);
}

void Resolver::event_tsdns_write(Resolver::tsdns_request *request) {
	lock_guard lock{request->buffer_lock};
	if(request->write_buffer.empty())
		return;

	auto written = send(request->socket, request->write_buffer.data(), min(request->write_buffer.size(), 1024UL), MSG_DONTWAIT);
	if(written < 0) {
#ifdef WIN32
		auto error = WSAGetLastError();
        if(error != WSAEWOULDBLOCK)
            return;
		request->callback(ResultState::TSDNS_CONNECTION_FAIL, -4, "write failed: " + to_string(error));
#else
		if(errno == EAGAIN)
			return;
		request->callback(ResultState::TSDNS_CONNECTION_FAIL, -4, "write failed: " + to_string(errno) + "/" + strerror(errno));
#endif
		this->destroy_tsdns_request(request);
		return;
	} else if(written == 0) {
		request->callback(ResultState::TSDNS_CONNECTION_FAIL, -5, "remote peer hang up");
		this->destroy_tsdns_request(request);
		return;
	}

	if(written == request->write_buffer.size())
		request->write_buffer.clear();
	else {
		request->write_buffer = request->write_buffer.substr(written);
		event_add(request->event_write, nullptr);
	}
}