#include <stdint.h>
#include <stdbool.h>

#define SERIAL_PORT 0x3f8

extern uint8_t serial_inb(uint16_t port);
extern void serial_outb(uint16_t port, uint8_t value);

static int serial_received(void) {
  return serial_inb(SERIAL_PORT + 5) & 1;
}

static uint8_t serial_read(void) {
  while (serial_received() == 0);
  return serial_inb(SERIAL_PORT);
}

static int serial_trans_empty(void) {
  return serial_inb(SERIAL_PORT + 5) & 0x20;
}

static void serial_write(uint8_t value) {
  while (!serial_trans_empty());
  serial_outb(SERIAL_PORT, value);
}

// REFERENCE: https://wiki.osdev.org/Serial_Ports
bool serial_init(void) {
  serial_outb(SERIAL_PORT + 1, 0x00); 
  serial_outb(SERIAL_PORT + 3, 0x80); 
  serial_outb(SERIAL_PORT + 0, 0x03);
  serial_outb(SERIAL_PORT + 1, 0x00);
  serial_outb(SERIAL_PORT + 3, 0x03);
  serial_outb(SERIAL_PORT + 2, 0xc7);
  serial_outb(SERIAL_PORT + 4, 0x0b);
  serial_outb(SERIAL_PORT + 4, 0x1e);
  serial_outb(SERIAL_PORT + 0, 0xae);

  if (serial_inb(SERIAL_PORT + 0) != 0xae) {
    return false;
  }

  serial_outb(SERIAL_PORT + 4, 0x0f);
  return true;
}

// For printf library
void putchar_(char c) {
  serial_write(c);
}