#include "vga.h"
#include "string.h"
#include "port.h"
#include <stdint.h>
#include <stddef.h>

uint16_t* terminal_buffer = (uint16_t*) 0xB8000;;

uint8_t vga_color(enum vga_color fg, enum vga_color bg) {
	return fg | bg << 4;
}

uint16_t vga_entry(unsigned char uc, uint8_t color) {
	return (uint16_t) uc | (uint16_t) color << 8;
}

void vclear(void) {
	terminal_row = 0;
	terminal_column = 0;
	for (size_t y = 0; y < VGA_HEIGHT; y++)
	{
		for (size_t x = 0; x < VGA_WIDTH; x++)
		{
			const size_t index = y * VGA_WIDTH + x;
			terminal_buffer[index] = vga_entry(' ', terminal_color);
		}
	}
}

void vsetcolor(uint8_t color) {
	terminal_color = color;
}

void vsetchar(char c, uint8_t color, size_t x, size_t y) {
	const size_t index = y * VGA_WIDTH + x;
	terminal_buffer[index] = vga_entry(c, color);
}

void vscroll() {
	for (unsigned int row=1; row < VGA_HEIGHT; row++)
	{
		size_t row_bytesize = VGA_WIDTH * 2; // A VGA entry is 2 bytes
		// Copy each line one line up
		memcpy(&terminal_buffer[(row - 1) * VGA_WIDTH], 
				&terminal_buffer[row * VGA_WIDTH], row_bytesize);
	}
	// Clear last line
	for (unsigned int col=0; col < VGA_WIDTH; col++)
	{
		terminal_buffer[VGA_WIDTH * (VGA_HEIGHT - 1) + col] = vga_entry(' ', terminal_color);
	}
	terminal_row--;
}

void vputchar(char c) {
	void newline() {
		terminal_column = 0;
		if (++terminal_row >= VGA_HEIGHT)
			vscroll();
	}
	switch (c) {
		default:
			vsetchar(c, terminal_color, terminal_column, terminal_row);
			terminal_column++;
			break;
		case '\n':
			newline();
			break;
		case '\t':
			// tab width of 4
			terminal_column = (terminal_column / 4 + 1) * 4;
			break;
		case '\b':
			if (terminal_column > 0) terminal_column--;
			break;
		case '\r':
			terminal_column = 0;
			break;
		case '\f':
			vclear();
			break;
		case '\a':
			break;
	}
	if (terminal_column >= VGA_WIDTH)
		newline();
}

void _putchar(char c) {
	vputchar(c);
}

void vprint(const char* str) {
	for (size_t i = 0; i < strlen(str); i++)
		vputchar(str[i]);
}

void vputn(const char* str, size_t l) {
	for (size_t i = 0; i < l; i++)
		vputchar(str[i]);
}

void vlocate(size_t column, size_t row) {
	terminal_column = column % VGA_WIDTH;
	terminal_row = row % VGA_HEIGHT;
}