#include <serial.h>
#include <bindings.h>

#define PORT 0x3F8

// initialize the specified COM port for serial
// see https://wiki.osdev.org/Serial_Ports
// and https://en.wikibooks.org/wiki/Serial_Programming/8250_UART_Programming
int serial_init(void) {
	outb(PORT + 1, 0x00); // disable interrupts
	outb(PORT + 3, 0x80); // enable DLAB (divisor latch access bit)
	outb(PORT + 0, 0x03); // (lo) Set baud divisor to 3 38400 baud
	outb(PORT + 1, 0x00); // (hi)
	outb(PORT + 3, 0x03); // disable DLAB, set 8 bits per word, one stop bit, no parity
	outb(PORT + 2, 0xC7); // enable and clear FIFOs, set to maximum threshold
	// outb(port + 4, 0x0B); // TODO copied this from osdev wiki but i don't think you need it here
	outb(PORT + 4, 0x1E); // set in loopback mode for test
	outb(PORT + 0, 0xAE); // test by sending 0xAE

	uint8_t response = inb(PORT + 0);
	if (response != 0xAE) {
		// TODO panic here?
		return -1;
	}

	// disable loopback, enable IRQs
	outb(PORT + 4, 0x0F);
	return 0;
}

uint8_t serial_in(void) {
	// wait for data to be available
	while ((inb(PORT + 5) & 0x01) == 0);
	return inb(PORT);
}

void serial_out(uint8_t ch) {
	// wait for output to be free
	while ((inb(PORT + 5) & 0x20) == 0);
	outb(PORT, ch);
}

void serial_out_str(const char *str) {
	for (; *str != '\0'; str++) {
		serial_out(*str);
	}
}