#include <libreichwein/file.h>

#include <alsa/asoundlib.h>

#include <cstdint>
#include <cmath>
#include <iostream>
#include <limits>
#include <exception>
#include <stdexcept>

#include <stdio.h>
#include <sys/types.h>
#include <sys/time.h>

using namespace std::string_literals;

//static const int CLICK_NOTE = 37;
//static const int CLICK_CHANNEL = 4;

static const char *device = "default";    // playback device
const snd_pcm_sframes_t nframes = 1024;   // ~1/44th sec buffer size
int16_t buffer[nframes];
const unsigned int f_sample = 44100;
const double pi = std::acos(-1);

class ClickStream
{
public:
  ClickStream(): m_phase(1000000)
  {
    std::string data_s = Reichwein::File::getFile("media/click.s16le");
    m_data.resize(data_s.size() / 2); // src is in bytes
    memcpy(m_data.data(), data_s.data(), data_s.size());
  }

  void generate()
  {
    int i;
    size_t j = m_phase;

    for (i = 0; i < nframes; i++) {
        if (j >= m_data.size())
        {
          buffer[i] = 0;
        }
        else
        {
          buffer[i] = m_data[j];
        }
        j++;
    }

    m_phase = j;
  }

  void click()
  {
    m_phase = 0;
  }

private:
  std::vector<uint16_t> m_data;
  size_t m_phase;
};

class PCM
{
public:
  PCM()
  {
    // non-blocking
    if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK)) < 0) {
        printf("Playback open error: %s\n", snd_strerror(err));
        exit(EXIT_FAILURE);
    }
    if ((err = snd_pcm_set_params(handle,
                      SND_PCM_FORMAT_S16_LE,
                      SND_PCM_ACCESS_RW_INTERLEAVED,
                      1,
                      f_sample,
                      1,
                      100000)) < 0) {   // latency in us
        printf("Playback open error: %s\n", snd_strerror(err));
        exit(EXIT_FAILURE);
    }
 
    npfd = snd_pcm_poll_descriptors_count(handle);
    if (npfd < 0) {
      throw std::runtime_error("snd_pcm_poll_descriptors_count() failed");
    }
    pfd = (struct pollfd *)malloc(npfd * sizeof(struct pollfd));
    if (pfd == nullptr) {
      throw std::runtime_error("alloca() error for PCM");
    }
    if (0 > snd_pcm_poll_descriptors(handle, pfd, npfd))
    {
      throw std::runtime_error("snd_pcm_poll_descriptors() failure");
    }

    if (0 > snd_pcm_start(handle))
    {
     throw std::runtime_error("PCM could not be started");
    }

    if (npfd != 1) {
      std::cout << "Warning: " << std::to_string(npfd) << " poll fds for pcm" << std::endl;
    }
  }

  ~PCM()
  {
    // pass the remaining samples, otherwise they're dropped in close
    err = snd_pcm_drain(handle);
    if (err < 0)
        printf("snd_pcm_drain failed: %s\n", snd_strerror(err));
    snd_pcm_close(handle);

    free(pfd);
  }

  int fd()
  {
    return pfd->fd;
  }

  // write from buffer to ALSA PCM
  void write()
  {
        snd_pcm_sframes_t written = snd_pcm_writei(handle, &buffer[0], nframes);
        if (written < 0) {
            if (written == -EPIPE) {
              std::cout << "Warning: PCM underrun" << std::endl;
            }
            std::cout << "Recovering." << std::endl;
            written = snd_pcm_recover(handle, written, 0);
        }
        if (written < 0) {
            throw std::runtime_error("snd_pcm_writei failed: "s + snd_strerror(written));
        }

        if (written != nframes) {
          std::cout << "Warning: written " << std::to_string(written) << " frames instead of "<< std::to_string(nframes) << std::endl;
        }
  }

  bool wait_for_event()
  {
    int result = poll(pfd, npfd, 10000);
    if (result > 0)
    {
      // event
      return true;
    }
    else if (result == 0) {
      // timeout
      return false;
    } else {
      throw std::runtime_error("Poll unsuccessful");
    }
  }

  bool write_available()
  {
    snd_pcm_sframes_t result = snd_pcm_avail(handle);
    if (0 > result) {
      std::cerr << "Error: snd_pcm_avail()" << std::endl;
      //throw std::runtime_error("snd_pcm_avail()");
    }

    return result >= nframes;
  }

private:
  int err;
  snd_pcm_t *handle;

  int npfd;
  struct pollfd* pfd;
};

class MIDI
{
public:
  MIDI()
  {
    if (0 > snd_seq_open(&seq_handle, "default", SND_SEQ_OPEN_INPUT, SND_SEQ_NONBLOCK))
    {
      throw std::runtime_error("MIDI sequencer couldn't be opened");
    }

    if (0 > snd_seq_set_client_name(seq_handle, "Midi Listener"))
    {
      throw std::runtime_error("MIDI client name couldn't be set");
    }

    if (0 > ((in_port = snd_seq_create_simple_port(seq_handle, "24:0",
                      SND_SEQ_PORT_CAP_WRITE | SND_SEQ_PORT_CAP_SUBS_WRITE | SND_SEQ_PORT_CAP_READ | SND_SEQ_PORT_CAP_SUBS_READ,
                      SND_SEQ_PORT_TYPE_APPLICATION))))
    {
      throw std::runtime_error("MIDI port couldn't be opened");
    }

    std::cout << "in_port: " << std::to_string(in_port) << std::endl;

#if 1
    snd_seq_addr_t sender, dest;
    snd_seq_port_subscribe_t *subs;
    sender.client = 24;
    sender.port = 0;
    dest.client = snd_seq_client_id(seq_handle);
    dest.port = in_port;
    snd_seq_port_subscribe_alloca(&subs);
    snd_seq_port_subscribe_set_sender(subs, &sender);
    snd_seq_port_subscribe_set_dest(subs, &dest);
    snd_seq_port_subscribe_set_queue(subs, 1);
    //snd_seq_port_subscribe_set_time_update(subs, 1);
    snd_seq_port_subscribe_set_time_real(subs, 1);
    // TODO: fix timestamp (currently always 0)
    if (0 > snd_seq_subscribe_port(seq_handle, subs))
#endif
    //if (0 > snd_seq_connect_from(seq_handle, in_port, 24, 0))
    {
      throw std::runtime_error("MIDI port couldn't be connected");
    }

    npfd = snd_seq_poll_descriptors_count(seq_handle, POLLIN);
    if (npfd < 0) {
      throw std::runtime_error("snd_seq_poll_descriptors_count() failed");
    }
    pfd = (struct pollfd *)malloc(npfd * sizeof(struct pollfd));
    if (pfd == nullptr) {
      throw std::runtime_error("alloca() error for MIDI");
    }
    if (0 > snd_seq_poll_descriptors(seq_handle, pfd, npfd, POLLIN))
    {
      throw std::runtime_error("snd_seq_poll_descriptors() failure");
    }

    if (npfd != 1) {
      std::cout << "Warning: " << std::to_string(npfd) << " poll fds for MIDI" << std::endl;
    }
  }

  ~MIDI()
  {
    free(pfd);
  }

  int fd()
  {
    return pfd->fd;
  }

  bool event_ready()
  {
    int result = snd_seq_event_input_pending(seq_handle, 1);
    if (result < 0) {
      throw std::runtime_error("snd_seq_event_input_pending() failed");
    }

    return result > 0;
  }

  snd_seq_event_t *read(void)
  {
    snd_seq_event_t *ev = NULL;
    if (0 > snd_seq_event_input(seq_handle, &ev))
    {
     std::cerr << "snd_seq_event_input(): -EAGAIN" << std::endl;
    }
    return ev;
  }

  // returns if click starts
  bool process(const snd_seq_event_t *ev)
  {
     bool result = false;

     if((ev->type == SND_SEQ_EVENT_NOTEON)
            ||(ev->type == SND_SEQ_EVENT_NOTEOFF)) {
        const char *type = (ev->type == SND_SEQ_EVENT_NOTEON) ? "on " : "off";
        printf("[%d] Note %s: %2x vel(%2x), ch %2x\n", ((ev->flags & SND_SEQ_TIME_STAMP_MASK) == SND_SEQ_TIME_STAMP_REAL) ? ev->time.time.tv_sec : ev->time.tick,
                                               type,
                                               ev->data.note.note,
                                               ev->data.note.velocity,
                                               ev->data.control.channel);
        if (ev->type == SND_SEQ_EVENT_NOTEON) {
//          if (ev->data.note.note == CLICK_NOTE && ev->data.control.channel == CLICK_CHANNEL) {
            result = true;
//          }
        }
     }
     else if(ev->type == SND_SEQ_EVENT_CONTROLLER)
     {
        printf("[%d] Control:  %2x val(%2x)\n", ((ev->flags & SND_SEQ_TIME_STAMP_MASK) == SND_SEQ_TIME_STAMP_REAL) ? ev->time.time.tv_sec : ev->time.tick,
                                                ev->data.control.param,
                                                ev->data.control.value);
     }
     else if(ev->type == SND_SEQ_EVENT_CLOCK)
     {
        printf("[%d] Clock\n", ((ev->flags & SND_SEQ_TIME_STAMP_MASK) == SND_SEQ_TIME_STAMP_REAL) ? ev->time.time.tv_sec : ev->time.tick);
     }
     else
     {
        printf("[%d] Unknown:  Unhandled Event Received\n", ev->time.tick);
     }
     return result;
  }

  void wait_for_event()
  {
    int result = poll(pfd, npfd, 10000);
    if (result > 0)
    {
      // event
    }
    else if (result == 0) {
      // timeout
    } else {
      throw std::runtime_error("Poll unsuccessful");
    }
  }

private:
  snd_seq_t *seq_handle;
  int in_port;
  int npfd;
  struct pollfd* pfd;
};

int main(void)
{
  try {
    MIDI midi;
    ClickStream stream;
    PCM pcm;

    stream.generate();
    pcm.write();
    stream.generate();

    while (true) {
      //midi.wait_for_event();
      //pcm.wait_for_event();
      fd_set read_set;
      FD_ZERO(&read_set);
      FD_SET(midi.fd(), &read_set);

      fd_set write_set;
      FD_ZERO(&write_set);
      FD_SET(pcm.fd(), &write_set);

      struct timeval timeout;
      timeout.tv_sec = 1;
      timeout.tv_usec = 0;

      int result = select(FD_SETSIZE, &read_set, &write_set, NULL, &timeout);
      if (result < 0) {
        throw std::runtime_error("select() failed");
      } else if (result == 0) {
        throw std::runtime_error("select() timeout");
      }

      if (midi.event_ready())
      {
        //std::cout << "read..." << std::endl;
        auto event = midi.read();
        //std::cout << "process..." << std::endl;
        if (midi.process(event)) {
          stream.click();
          //std::cout << "DEBUG: CLICK" << std::endl;
        }
      }

      if (pcm.write_available()) {
        //std::cout << "DEBUG: WRITE" << std::endl;
        pcm.write();
        stream.generate();
      }
    }
  } catch (const std::exception& ex) {
    std::cerr << "Error: " << ex.what() << std::endl;
  }
 
  return 0;
}