#include "uart_16550.h"
#include <stddef.h>

int
uart_thre(unsigned short port)
{
  return inb(port + LineStatus) & THRE;
}

void
uart_putc(const FILE *self, char a)
{
  const unsigned short port = (unsigned short)self->id;

  while (uart_thre(port) == 0) {}
  outb((unsigned char)a, port);

  if (a == '\n') {
    while (uart_thre(port) == 0) {}
    outb('\r', port);
  }
}

int
uart_puts(const FILE *self, const char *string, int length)
{
  int i;
  int written = 0;

  if (length == -1)
    while (*string != '\0') {
      uart_putc(self, *string);
      ++string;
      ++written;
    }

  else
    for (i = 0; i < length; ++i) {
      uart_putc(self, string[i]);
      ++written;
    }

  return written;
}

void
uart_flush(__attribute__((unused)) const FILE *self)
{
}

FILE uart_stream;

FILE *
uart_init(unsigned short port)
{
  outb(0x00, port + 1); /* Disable all interrupts */
  outb(0x80, port + 3); /* Enable DLAB (set baud rate divisor) */
  outb(0x03, port + 0); /* Set divisor to 3 (lo byte) 38400 baud */
  outb(0x00, port + 1); /*                  (hi byte) */
  outb(0x03, port + 3); /* 8 bits, no parity, one stop bit */
  outb(0xc7, port + 2); /* Enable FIFO, clear them, with 14-byte threshold */
  outb(0x0b, port + 4); /* IRQs enabled, RTS/DSR set */
  outb(0x1e, port + 4); /* Set in loopback mode, test the serial chip */
  outb(0xae, port + 0); /* Test serial chip (send byte 0xAE and check if serial */
                        /* returns same byte) */

  /* Check if serial is faulty (i.e: not same byte as sent) */
  if (inb(port + 0) != 0xae) { return NULL; }

  /* If serial is not faulty set it in normal operation mode */
  /* (not-loopback with IRQs enabled and OUT#1 and OUT#2 bits enabled) */
  outb(0x0f, port + 4);
  uart_stream.id = port;
  uart_stream.putc = &uart_putc;
  uart_stream.puts = &uart_puts;
  uart_stream.flush = &uart_flush;
  return &uart_stream;
}