/*
 * ebusd - daemon for communication with eBUS heating systems.
 * Copyright (C) 2015-2018 John Baier <ebusd@ebusd.eu>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include "lib/ebus/device.h"
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/file.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#ifdef HAVE_LINUX_SERIAL
#  include <linux/serial.h>
#endif
#include <errno.h>
#ifdef HAVE_PPOLL
#  include <poll.h>
#endif
#include <cstdlib>
#include <cstring>
#include <fstream>
#include "lib/ebus/data.h"

namespace ebusd {

#define MTU 1540

#ifndef POLLRDHUP
#define POLLRDHUP 0
#endif

// ebusd enhanced protocol IDs:
//TODO use this:
#define ENH_INIT ((symbol_t)0x00)
#define ENH_RESETTED ((symbol_t)0x00)
#define ENH_SEND ((symbol_t)0x01)
#define ENH_RECEIVED ((symbol_t)0x01)
#define ENH_START ((symbol_t)0x02)
#define ENH_STARTED ((symbol_t)0x02)
#define ENH_FAILED ((symbol_t)0x82)

/**
 * Construct a new instance.
 * @param name the device name (e.g. "/dev/ttyUSB0" for serial, "127.0.0.1:1234" for network).
 * @param address the socket address of the device.
 * @param readOnly whether to allow read access to the device only.
 * @param initialSend whether to send an initial @a ESC symbol in @a open().
 * @param udp true for UDP, false to TCP.
 * @param enhancedProto whether to use the ebusd enhanced protocol.
 */
Device::Device(const char* name, bool checkDevice, bool readOnly, bool initialSend, bool enhancedProto)
  : m_name(name), m_checkDevice(checkDevice), m_readOnly(readOnly), m_initialSend(initialSend),
    m_enhancedProto(enhancedProto), m_fd(-1), m_listener(nullptr), m_arbitrationMaster(SYN),
    m_arbitrationCheck(false), m_bufSize(((MAX_LEN+1+3)/4)*4), m_bufLen(0), m_bufPos(0) {
  m_buffer = reinterpret_cast<symbol_t*>(malloc(m_bufSize));
  if (!m_buffer) {
    m_bufSize = 0;
  }
}

Device::~Device() {
  close();
  if (m_buffer) {
    free(m_buffer);
  }
}

Device* Device::create(const char* name, bool checkDevice, bool readOnly, bool initialSend) {
  bool enhanced = strncmp(name, "enh:", 4) == 0;
  if (enhanced) {
    name += 4;
  }
  if (strchr(name, '/') == nullptr && strchr(name, ':') != nullptr) {
    char* in = strdup(name);
    bool udp = false;
    char* addrpos = in;
    char* portpos = strchr(addrpos, ':');
    if (!enhanced && portpos >= addrpos+3 && strncmp(addrpos, "enh", 3) == 0) {
      enhanced = true; // support enhtcp:<ip>:<port> and enhudp:<ip>:<port>
      addrpos += 3;
      if (portpos == addrpos) {
        addrpos++;
        portpos = strchr(addrpos, ':');
      }
    } // else: support enh:<ip>:<port> defaulting to TCP
    if (portpos == addrpos+3 && (strncmp(addrpos, "tcp", 3) == 0 || (udp=(strncmp(addrpos, "udp", 3) == 0)))) {
      addrpos += 4;
      portpos = strchr(addrpos, ':');
    }
    if (portpos == nullptr) {
      free(in);
      return nullptr;  // invalid protocol or missing port
    }
    result_t result = RESULT_OK;
    unsigned int port = parseInt(portpos+1, 10, 1, 65535, &result);
    if (result != RESULT_OK) {
      free(in);
      return nullptr;  // invalid port
    }
    struct sockaddr_in address;
    memset(reinterpret_cast<char*>(&address), 0, sizeof(address));
    *portpos = 0;
    if (inet_aton(addrpos, &address.sin_addr) == 0) {
      struct hostent* h = gethostbyname(addrpos);
      if (h == nullptr) {
        free(in);
        return nullptr;  // invalid host
      }
      memcpy(&address.sin_addr, h->h_addr_list[0], h->h_length);
    }
    free(in);
    address.sin_family = AF_INET;
    address.sin_port = (in_port_t)htons((uint16_t)port);
    return new NetworkDevice(name, address, readOnly, initialSend, udp, enhanced);
  }
  // support enh:/dev/<device>
  return new SerialDevice(name, checkDevice, readOnly, initialSend, enhanced);
}

result_t Device::open() {
  close();
  return m_bufSize == 0 ? RESULT_ERR_DEVICE : RESULT_OK;
}

void Device::close() {
  if (m_fd != -1) {
    ::close(m_fd);
    m_fd = -1;
  }
  m_bufLen = 0;  // flush read buffer
}

bool Device::isValid() {
  if (m_fd == -1) {
    return false;
  }
  if (m_checkDevice) {
    checkDevice();
  }
  return m_fd != -1;
}

result_t Device::send(symbol_t value) {
  if (!isValid()) {
    return RESULT_ERR_DEVICE;
  }
  if (m_readOnly || !write(value)) {
    return RESULT_ERR_SEND;
  }
  if (m_listener != nullptr) {
    m_listener->notifyDeviceData(value, false);
  }
  return RESULT_OK;
}

result_t Device::recv(unsigned int timeout, symbol_t* value, ArbitrationState* arbitrationState) {
  if (!isValid()) {
    return RESULT_ERR_DEVICE;
  }
  bool isAvailable = available();
  if (!isAvailable && timeout > 0) {
    int ret;
    struct timespec tdiff;

    // set select timeout
    tdiff.tv_sec = timeout/1000000;
    tdiff.tv_nsec = (timeout%1000000)*1000;

#ifdef HAVE_PPOLL
    nfds_t nfds = 1;
    struct pollfd fds[nfds];

    memset(fds, 0, sizeof(fds));

    fds[0].fd = m_fd;
    fds[0].events = POLLIN | POLLERR | POLLHUP | POLLRDHUP;
    ret = ppoll(fds, nfds, &tdiff, nullptr);
    if (ret >= 0 && fds[0].revents & (POLLERR | POLLHUP | POLLRDHUP)) {
      ret = -1;
    }
#else
#ifdef HAVE_PSELECT
    fd_set readfds, exceptfds;

    FD_ZERO(&readfds);
    FD_ZERO(&exceptfds);
    FD_SET(m_fd, &readfds);

    ret = pselect(m_fd + 1, &readfds, nullptr, &exceptfds, &tdiff, nullptr);
    if (ret >= 1 && FD_ISSET(m_fd, &exceptfds)) {
      ret = -1;
    }
#else
    ret = 1;  // ignore timeout if neither ppoll nor pselect are available
#endif
#endif
    if (ret == -1) {
      close();
      return RESULT_ERR_DEVICE;
    }
    if (ret == 0) {
      return RESULT_ERR_TIMEOUT;
    }
  }

  ArbitrationState prevState = *arbitrationState;
  // directly read byte from device
  if (!read(value, isAvailable, arbitrationState)) {
    close();
    return RESULT_ERR_DEVICE;
  }
  if (m_enhancedProto || *value != SYN || m_arbitrationMaster == SYN) {
    if (m_listener != nullptr) {
      m_listener->notifyDeviceData(*value, true);
    }
    if (m_enhancedProto) {
      if (*arbitrationState != prevState) {
        m_arbitrationMaster = SYN;
        m_arbitrationCheck = false;
      }
    } else if (m_arbitrationMaster != SYN) {
      if (m_arbitrationCheck) {
        *arbitrationState = *value == m_arbitrationMaster ? as_won : as_lost;
        m_arbitrationMaster = SYN;
        m_arbitrationCheck = false;
      } else {
        *arbitrationState = m_arbitrationMaster == SYN ? as_none : as_start;
      }
    }
    return RESULT_OK;
  }
  bool wrote = write(m_arbitrationMaster);  // send as fast as possible
  if (m_listener != nullptr) {
    m_listener->notifyDeviceData(*value, true);
  }
  if (!wrote) {
    *arbitrationState = as_error;
    m_arbitrationMaster = SYN;
    m_arbitrationCheck = false;
    return RESULT_OK;
  }
  if (m_listener != NULL) {
    m_listener->notifyDeviceData(m_arbitrationMaster, false);
  }
  m_arbitrationCheck = true;
  *arbitrationState = as_running;
  return RESULT_OK;
}

result_t Device::startArbitration(symbol_t masterAddress) {
  if (m_arbitrationCheck) {
    return RESULT_ERR_DUPLICATE;
  }
  if (m_readOnly) {
    return RESULT_ERR_SEND;
  }
  m_arbitrationMaster = masterAddress;
  m_arbitrationCheck = false;
  if (m_enhancedProto && masterAddress != SYN) {
    if (!write(masterAddress, true)) {
      m_arbitrationMaster = SYN;
      return RESULT_ERR_SEND;
    }
    m_arbitrationCheck = true;
  }
  return RESULT_OK;
}

bool Device::write(symbol_t value, bool startArbitration) {
  if (m_enhancedProto) {
    symbol_t buf[2] = {startArbitration ? ENH_START : ENH_SEND, value};
    return ::write(m_fd, buf, 2) == 2;
  }
  return ::write(m_fd, &value, 1) == 1;
}

bool Device::available() {
  if (m_bufLen <= 0) {
    return false;
  }
  if (!m_enhancedProto) {
    return true;
  }
  // peek into the received enhanced proto bytes to determine symbol availability
  for (size_t pos = 0; pos < m_bufLen; pos++) {
    symbol_t ch = m_buffer[(pos+m_bufPos)%m_bufSize];
    if (ch == ENH_RECEIVED) {
      return pos+1 < m_bufLen;
    }
  }
  return false;
}

bool Device::read(symbol_t* value, bool isAvailable, ArbitrationState* arbitrationState) {
  if (!isAvailable) {
    if (m_bufLen > 0 && m_bufPos != 0) {
      if (m_bufLen > m_bufSize / 2) {
        m_bufLen = 0; // TODO report error
      } else {
        size_t tail;
        if (m_bufPos+m_bufLen > m_bufSize) {
          // move wrapped tail away
          tail = (m_bufPos+m_bufLen) % m_bufSize;
          size_t head = m_bufLen-tail;
          memmove(m_buffer+head, m_buffer, tail);
        } else {
          tail = 0;
        }
        // move head to first position
        memmove(m_buffer, m_buffer + m_bufPos, m_bufLen - tail);
      }
    }
    m_bufPos = 0;
    // fill up the buffer
    ssize_t size = ::read(m_fd, m_buffer + m_bufLen, m_bufSize - m_bufLen);
    if (size <= 0) {
      return false;
    }
    m_bufLen += size;
  }
  if (!available()) {
    return false;
  }
  if (!m_enhancedProto) {
    *value = m_buffer[m_bufPos];
    m_bufPos = (m_bufPos+1)%m_bufSize;
    m_bufLen--;
    return true;
  }
  while (m_bufLen > 0) {
    symbol_t ch = m_buffer[m_bufPos];
    m_bufPos = (m_bufPos+1)%m_bufSize;
    m_bufLen--;
    switch (ch) {
      case ENH_STARTED:
        *arbitrationState = as_won;
        if (m_listener != NULL) {
          m_listener->notifyDeviceData(m_arbitrationMaster, false);
        }
        m_arbitrationMaster = SYN;
        break;
      case ENH_FAILED:
        *arbitrationState = as_error;
        if (m_listener != NULL) {
          m_listener->notifyDeviceData(m_arbitrationMaster, false);
        }
        m_arbitrationMaster = SYN;
        break;
      case ENH_RECEIVED:
        if (m_bufLen <= 0) {
          return false;
        }
        *value = m_buffer[m_bufPos];
        m_bufPos = (m_bufPos+1)%m_bufSize;
        m_bufLen--;
        return true;
      case ENH_RESETTED: // TODO
        *arbitrationState = as_error;
        break;
      default:
        // TODO proto error
        return false;
    }
  }
  return false;
}


result_t SerialDevice::open() {
  result_t result = Device::open();
  if (result != RESULT_OK) {
    return result;
  }
  struct termios newSettings;

  // open file descriptor
  m_fd = ::open(m_name, O_RDWR | O_NOCTTY);

  if (m_fd < 0) {
    return RESULT_ERR_NOTFOUND;
  }
  if (isatty(m_fd) == 0) {
    close();
    return RESULT_ERR_NOTFOUND;
  }

  if (flock(m_fd, LOCK_EX|LOCK_NB)) {
    close();
    return RESULT_ERR_DEVICE;
  }

#ifdef HAVE_LINUX_SERIAL
  struct serial_struct serial;
  if (ioctl(m_fd, TIOCGSERIAL, &serial) == 0) {
    serial.flags |= ASYNC_LOW_LATENCY;
    ioctl(m_fd, TIOCSSERIAL, &serial);
  }
#endif

  // save current settings
  tcgetattr(m_fd, &m_oldSettings);

  // create new settings
  memset(&newSettings, 0, sizeof(newSettings));

  newSettings.c_cflag |= ((m_enhancedProto ? B115200 : B2400) | CS8 | CLOCAL | CREAD);
  newSettings.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);  // non-canonical mode
  newSettings.c_iflag |= IGNPAR;  // ignore parity errors
  newSettings.c_oflag &= ~OPOST;

  // non-canonical mode: read() blocks until at least one byte is available
  newSettings.c_cc[VMIN]  = 1;
  newSettings.c_cc[VTIME] = 0;

  // empty device buffer
  tcflush(m_fd, TCIFLUSH);

  // activate new settings of serial device
  tcsetattr(m_fd, TCSAFLUSH, &newSettings);

  // set serial device into blocking mode
  fcntl(m_fd, F_SETFL, fcntl(m_fd, F_GETFL) & ~O_NONBLOCK);

  if (m_initialSend && !write(ESC)) {
    return RESULT_ERR_SEND;
  }
  return RESULT_OK;
}

void SerialDevice::close() {
  if (m_fd != -1) {
    // empty device buffer
    tcflush(m_fd, TCIOFLUSH);

    // restore previous settings of the device
    tcsetattr(m_fd, TCSANOW, &m_oldSettings);
  }
  Device::close();
}

void SerialDevice::checkDevice() {
  int port;
  if (ioctl(m_fd, TIOCMGET, &port) == -1) {
    close();
  }
}


result_t NetworkDevice::open() {
  result_t result = Device::open();
  if (result != RESULT_OK) {
    return result;
  }
  m_fd = socket(AF_INET, m_udp ? SOCK_DGRAM : SOCK_STREAM, 0);
  if (m_fd < 0) {
    return RESULT_ERR_GENERIC_IO;
  }
  int ret;
  if (m_udp) {
    struct sockaddr_in address = m_address;
    address.sin_addr.s_addr = INADDR_ANY;
    ret = bind(m_fd, (struct sockaddr*)&address, sizeof(address));
  } else {
    int value = 1;
    ret = setsockopt(m_fd, IPPROTO_TCP, TCP_NODELAY, reinterpret_cast<void*>(&value), sizeof(value));
    value = 1;
    setsockopt(m_fd, SOL_SOCKET, SO_KEEPALIVE, reinterpret_cast<void*>(&value), sizeof(value));
  }
  if (ret >= 0) {
    ret = connect(m_fd, (struct sockaddr*)&m_address, sizeof(m_address));
  }
  if (ret < 0) {
    close();
    return RESULT_ERR_GENERIC_IO;
  }
  if (!m_udp) {
    usleep(25000);  // wait 25ms for potential initial garbage
  }
  int cnt;
  symbol_t buf[MTU];
  while (ioctl(m_fd, FIONREAD, &cnt) >= 0 && cnt > 1) {
    // skip buffered input
    ssize_t read = ::read(m_fd, &buf, MTU);
    if (read <= 0) {
      break;
    }
  }
  m_bufLen = 0;
  if (m_initialSend && !write(ESC)) {
    return RESULT_ERR_SEND;
  }
  return RESULT_OK;
}

void NetworkDevice::checkDevice() {
  int cnt;
  if (ioctl(m_fd, FIONREAD, &cnt) < 0) {
    close();
  }
}

}  // namespace ebusd