// fether os kernel.
#include <stddef.h>
#include <stdint.h>

// protecting compilation.
#if defined(__linux__)
	#error "You should compile all with a cross-compiler. See project wiki."
#elif !defined(__i386__)
	#error "This is an 32bit kernel. Please use i386 target."
#endif

volatile uint16_t* vga_buffer = (uint16_t*)0xB8000; // defining VGA text mode.

// vga(2) settings
const int VGA_COLS = 80;
const int VGA_ROWS = 25;

// terminal settings
int term_col = 0;
int term_row = 0;
uint8_t term_color = 0x0F;

// clearing the terminal
void term_init() {
	for(int col = 0; col < VGA_COLS; col++) {
		for(int row = 0; row < VGA_ROWS; row++) {
			const size_t index = (VGA_COLS * row) + col;
			vga_buffer[index] = ((uint16_t)term_color << 8) | ' ';
		}
	}
}

void term_put(char c) {
	switch(c) {
		case '\n': // newline implemintation
			{
				term_col = 0;
				term_row++;
				break;
			}
		default: // if char doesn't match any special symbol
			{
				const size_t index = (VGA_COLS * term_row) + term_col;
				vga_buffer[index] = ((uint16_t)term_color << 8) | c;
				break;
			}
	}

	if(term_col >= VGA_COLS) {
		term_col = 0;
		term_row++;
	}


	if(term_row >= VGA_ROWS) {
		term_col = 0;
		term_row = 0;
	}
}


void term_print(const char* str) { for(size_t i = 0; str[i] != '\0'; i++) { term_put(str[i]); } }

void kmain() {
	term_init();
	term_print("Kernel loaded.\nFether.");
}