#include <stdint.h>
#include "utils.h"

#define PORT 0x3f8                   // COM1
#define LINE_STATUS_REGISTER         PORT + 5
#define TRANSMITTER_EMPTY_BITMASK    0b00100000

uint8_t inportb(uint16_t port) {
    uint8_t r;
    asm("inb %1, %0" : "=a" (r) : "dN" (port));
    return r;
}

void outportb(uint16_t port, uint8_t data) {
    asm("outb %1, %0" : : "dN" (port), "a" (data));
}

void init_serial() {
    outportb(PORT + 1, 0x00); // Disable all interrupts
    outportb(PORT + 3, 0x80); // Enable DLAB (set baud rate divisor)

    // Set divisor to 3 -> (115200 / 3) = 38400
    outportb(PORT + 0, 0x03); // LSB
    outportb(PORT + 1, 0x00); // MSB

    outportb(PORT + 3, 0x03); // Character length is 8 bits, no parity, one stop bit
    outportb(PORT + 2, 0xC7); // Enable FIFO, clear them, with 14-byte threshold

//  TODO: GDT and IDT in order to setup COM1 interrupts.
//        For now, though, we POLLLLL that mf.
//     outportb(PORT + 4, 0x0B); // IRQs enabled, RTS/DSR set

    outportb(PORT + 4, 0x1E); // Set in loopback mode, test the serial chip
    outportb(PORT + 0, 0xAE); // Test serial chip (send byte 0xAE and check if serial returns same byte)
    macaroni_assert(inportb(PORT + 0) == 0xAE, "0xAE expected from serial initizliation");
    outportb(PORT + 4, 0x0F);
}

int serial_tx_empty(void) {
    return inportb(LINE_STATUS_REGISTER) & TRANSMITTER_EMPTY_BITMASK;
}

void serial_putc(char c) {
    while (!serial_tx_empty());
    outportb(PORT, c);
}

void serial_puts(const char* s) {
    while (*s) serial_putc(*s++);
}

void serial_puthex(uint32_t h) {
    serial_puts("0x");
    for (int i = 28; i >= 0; i -= 4)
        serial_putc("0123456789abcdef"[(h >> i) & 0xF]);
}