#include <asm/interrupt.h>
#include <asm/io.h>
#include <errno.h>
#include <kernel/con.h>
#include <kernel/sched.h>
#include <kernel/serial.h>
#include <kernel/tty.h>
#include <sys/types.h>
#include <unistd.h>

/* 115200 baud */
#define DIVISOR 1

/* this shouldn't change */
#define FIFOSZ 16

#define RSBASE 0x3F8

#define RSDATA    RSBASE
#define RSINTEN   (RSBASE + 1)
#define RSFIFOC   (RSBASE + 2)
#define RSINTID   (RSBASE + 2)
#define RSLINEC   (RSBASE + 3)
#define RSMODEMC  (RSBASE + 4)
#define RSLINES   (RSBASE + 5)
#define RSMODEMS  (RSBASE + 6)
#define RSSCRATCH (RSBASE + 7)

extern void rs_isr(void);

/* internal function prototypes */
void rsint_tx(void);

struct tty_struct tty_rs = {
  .init = &serial_init,
  .write = &rsint_tx
};

static char present;

void serial_init(void) {
  present = 0;

  outb(RSSCRATCH, 0x00);
  outb(RSSCRATCH, 0xAA);
  if(inb(RSSCRATCH) != 0xAA) {
    printk("[rs] COM0 not detected!\n");
    return;
  }

  /* enable access to the divisor */
  outb(RSLINEC, inb(RSLINEC) | 0x80);
  /* write the divisor */
  outb(RSBASE, DIVISOR);
  outb(RSBASE + 1, DIVISOR >> 8);
  /* restore access to the divisor */
  outb(RSLINEC, inb(RSLINEC) & 0x7F);
  /* configure port parameters */
  outb(RSFIFOC, 0x07);
  outb(RSLINEC, 0x03);
  outb(RSMODEMC, 0x0B);
  outb(RSINTEN, 0x03);
  inb(RSDATA);

  /* test FIFO functionality */
  if(inb(RSINTID) & 0xC0 != 0xC0) {
    printk("[rs] Failed to enable FIFO on COM0!\n");
    return;
  }

  /* register the interrupt handler */
  register_isr(0x24, 0, &rs_isr);
  irq_enable(0x10);

  printk("[rs] Serial port COM0 initialized!\n");

  present = 1;
}

void rsint_rx(void) {
  struct tty_queue *q = &tty_rs.rqueue;

  if((inb(RSLINES) & 1) == 0)
    return;
  if(q->pwrite == ((q->pread - 1) % sizeof(q->buf)))
    return;

  q->buf[q->pwrite] = inb(RSDATA);
  q->pwrite = (q->pwrite + 1) % sizeof(q->buf);

  wake_up(&q->waiting);
}

void rsint_tx(void) {
  int i;
  int copied = 0;
  struct tty_queue *q = &tty_rs.wqueue;

  if((inb(RSLINES) & 0x20) == 0)
    return;

  for(i = 0; i < FIFOSZ; i++) {
    if(q->pread == q->pwrite)
      break;

    outb(RSDATA, q->buf[q->pread]);
    q->pread = (q->pread + 1) % TTY_BUF_SIZE;

    copied = 1;
  }

  if(copied)
    wake_up(&q->waiting);
}