#include <devices/8254.h>
#include <palacios/vmm.h>
#include <palacios/vmm_time.h>

// constants
#define OSC_HZ 1193182


/* The 8254 has three counters and one control port */
#define CHANNEL0_PORT 0x40
#define CHANNEL1_PORT 0x41
#define CHANNEL2_PORT 0x42
#define COMMAND_PORT 0x43


#define PIT_INTR_NUM 0

/* The order of these typedefs is important because the numerical values correspond to the 
 * values coming from the io ports
 */
typedef enum {NOT_RUNNING, WAITING_LOBYTE, WAITING_HIBYTE, RUNNING} channel_access_state_t;
typedef enum {LATCH_COUNT, LOBYTE_ONLY, HIBYTE_ONLY, LOBYTE_HIBYTE} channel_access_mode_t;
typedef enum {IRQ_ON_TERM_CNT, ONE_SHOT, RATE_GEN, SQR_WAVE, SW_STROBE, HW_STROBE} channel_op_mode_t;


struct channel {
  channel_access_mode_t access_mode;
  channel_access_state_t access_state;

  channel_op_mode_t op_mode;

  // Time til interrupt trigger 
  ullong_t ns;

  uint_t ctr;
  uint_t prg_ctr;
};


struct pit {

  struct channel ch_0;
  struct channel ch_1;
  struct channel ch_2;
};

struct pit_cmd {
  uint_t channel     : 2;
  uint_t access_mode : 2;
  uint_t op_mode     : 3;
  uint_t bcd_mode    : 1;
};






static void pit_update_time(ullong_t cpu_cycles, ullong_t cpu_freq, void * private_data) {

  return;
}



static int pit_read_channel(ushort_t port, void * dst, uint_t length, struct vm_device * dev) {
  PrintDebug("8254 PIT: Read of PIT Channel %d\n", port - CHANNEL0_PORT);
  return length;
}



static int pit_write_channel(ushort_t port, void * src, uint_t length, struct vm_device * dev) {
  PrintDebug("8254 PIT: Write to PIT Channel %d\n", port - CHANNEL0_PORT);
  return length;
}


static int pit_write_command(ushort_t port, void * src, uint_t length, struct vm_device * dev) {
  struct pit * state = (struct pit *)dev->private_data;
  struct pit_cmd * cmd = (struct pit_cmd *)src;

  PrintDebug("8254 PIT: Write to PIT Command port\n");

  if (length != 1) {
    PrintDebug("8254 PIT: Write of Invalid length to command port\n");
    return -1;
  }

  switch (cmd->channel) {
  case 0:
    state->ch_0.op_mode = cmd->op_mode;
    break;
  case 1:
    break;
  case 2:
    break;
  default:
    break;
  }


  return length;
}




static struct vm_timer_ops timer_ops = {
  .update_time = pit_update_time,
};


static int pit_init(struct vm_device * dev) {
  dev_hook_io(dev, CHANNEL0_PORT, &pit_read_channel, &pit_write_channel);
  dev_hook_io(dev, CHANNEL1_PORT, &pit_read_channel, &pit_write_channel);
  dev_hook_io(dev, CHANNEL2_PORT, &pit_read_channel, &pit_write_channel);
  dev_hook_io(dev, COMMAND_PORT, NULL, &pit_write_command);


  v3_add_timer(dev->vm, &timer_ops, dev);

  return 0;
}

static int pit_deinit(struct vm_device * dev) {

  return 0;
}


static struct vm_device_ops dev_ops = {
  .init = pit_init,
  .deinit = pit_deinit,
  .reset = NULL,
  .start = NULL,
  .stop = NULL,

};


struct vm_device * create_pit() {
  struct pit * pit_state = NULL;
  pit_state = (struct pit *)V3_Malloc(sizeof(struct pit));
  V3_ASSERT(pit_state != NULL);

  struct vm_device * dev = create_device("PIT", &dev_ops, pit_state);
  
  return dev;
}