#include "project.h"

#define RXR       ((0))
#define TXR       ((0))
#define DLLR      ((0))

#define IER       ((1))
#define DLHR      ((1))

#define IIR       ((2))
#define FCR       ((2))

#define LCR       ((3))
#define LCR_WS0           (1<<0)
#define LCR_WS1           (1<<1)
#define LCR_NSTOP         (1<<2)
#define LCR_PARITY_ENABLE (1<<3)
#define LCR_EVEN_PARITY   (1<<4)
#define LCR_STUCK_PARITY  (1<<5)
#define LCR_BREAK         (1<<6)
#define LCR_DLAB          (1<<7)

#define MCR      ((4))
#define MCR_DTR        (1<<0)
#define MCR_RTS        (1<<1)
#define MCR_AUX1       (1<<2)
#define MCR_AUX2       (1<<3)
#define MCR_LOOP       (1<<4)
#define MCR_AUTOFLOW   (1<<5)

#define LSR      ((5))
#define LSR_DA         (1<<0)
#define LSR_OR         (1<<1)
#define LSR_PE         (1<<2)
#define LSR_FE         (1<<3)
#define LSR_BRK        (1<<4)
#define LSR_THRE       (1<<5)
#define LSR_THREI      (1<<6)
#define LSR_FIFOE      (1<<7)

#define MSR   ((6))
#define MSR_DCTS  (1<<0)
#define MSR_DDSR  (1<<1)
#define MSR_TERI  (1<<2)
#define MSR_DDCD  (1<<3)
#define MSR_CTS   (1<<4)
#define MSR_DSR   (1<<5)
#define MSR_RI    (1<<6)
#define MSR_DCD   (1<<7)

#define SR    ((7))


/* 0 */
static uint8_t dllr = 1; /* 115200 baud */

/* 1 */
static uint8_t dlhr = 0;
static uint8_t ier = 0;

/* 2 */
static uint8_t iir = 0;

/* 3 */
static uint8_t lcr = LCR_WS0 | LCR_WS1; /* 8 bits, 1 stop, no parity */

/* 4 */
static uint8_t mcr = MCR_RTS | MCR_DTR; /* RTS and DTR on */

/* 5 */
static uint8_t lsr = LSR_THRE | LSR_THREI;

/* 6 */
static uint8_t msr = MSR_CTS | MSR_DSR | MSR_DCD;

/* 7 */
static uint8_t sr = 0;


static void vuart_xmit (uint8_t c)
{
  led1 = 100;
  ring_write_byte (&usart_tx_ring, c);
  usart_kick();
  ring_write_byte (&cdcacm_tx_ring, c);
}


static int vuart_recv_empty (void)
{
  if (!ring_empty (&usart_rx_ring))
    return 0;

  if (!ring_empty (&cdcacm_rx_ring))
    return 0;

  return 1;
}


static int vuart_recv (uint8_t *c)
{
  *c = 0;

  if (!ring_read_byte (&usart_rx_ring, c)) {
    led2 = 100;
    return 0;
  }

  if (!ring_read_byte (&cdcacm_rx_ring, c)) {
    led2 = 100;
    return 0;
  }

  return -1;
}


static void update_lsr (void)
{
  if (vuart_recv_empty())
    lsr &= ~LSR_DA;

  else
    lsr |= LSR_DA;
}

uint8_t vuart_read (unsigned reg)
{
  uint8_t val;

  switch (reg) {
  case RXR:

    //case DLLR:
    if (! (lcr & LCR_DLAB)) {
      vuart_recv (&val);
      update_lsr();
      return val;
    } else
      return dllr;

  case IER:
    //case DLLH:
    return (lcr & LCR_DLAB) ? dlhr : ier;

  case IIR:
    return iir;

  case LCR:
    return lcr;

  case MCR:
    return mcr;

  case LSR:
    update_lsr();
    val = lsr;
    lsr &= 0xe1;
    return val;

  case MSR:
    val = msr;
    msr &= 0xf0;
    return val;

  case SR:
    return sr;
  }

  return 0;
}


void vuart_write (unsigned reg, uint8_t val)
{
  switch (reg) {
  case RXR:

    //case DLLR:
    if (! (lcr & LCR_DLAB))
      vuart_xmit (val);

    else
      dllr = val;

    break;

  case IER:

    //case DLHR:
    if (! (lcr & LCR_DLAB))
      ier = val & 0xf;

    else
      dlhr = val;

    break;

  case LCR:
    lcr = val;
    break;

  case MCR:
    mcr = val & 0x1f;
    break;

  case SR:
    sr = val;
    break;
  }
}