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

// port numbers for first four serial ports
static uint16_t SERIAL_PORTS[] = { 
	[COM1] = 0x3F8, 
	[COM2] = 0x2F8, 
	[COM3] = 0x3E8, 
	[COM4] = 0x2E8,
};

// 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(enum serial_com_port com) {
	uint16_t port = SERIAL_PORTS[com];
	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(enum serial_com_port com) {
	uint16_t port = SERIAL_PORTS[com];
	// wait for data to be available
	while((inb(port + 5) & 0x01) == 0);
	return inb(port);
}

void serial_out(enum serial_com_port com, uint8_t ch) {
	uint16_t port = SERIAL_PORTS[com];
	// wait for output to be free
	while((inb(port + 5) & 0x20) == 0);
	outb(port, ch);
}

void serial_out_str(enum serial_com_port com, char *str) {
	uint16_t port = SERIAL_PORTS[com];
	for(; *str != '\0'; str++) {
		while((inb(port + 5) & 0x20) == 0);
		outb(port, *str);
	}
}