#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>

#include <kernel/tty.h>
#include <kernel/utils.h>

static const size_t TERM_WIDTH=80;
static const size_t TERM_HEIGHT=25;

static size_t terminal_row;
static size_t terminal_column;

static uint8_t current_color;
static uint16_t* term_buffer;
static uint16_t* const vga_buffer = (uint16_t*) 0xB8000;

void screen_initialize(void) {
	
	terminal_row = 0;
	terminal_column = 0;
	current_color = vga_color_set(LIGHT_GREY, BLACK);
	term_buffer = vga_buffer;
	
	for (size_t y = 0; y < TERM_HEIGHT; y++) {
		for(size_t x = 0; x < TERM_WIDTH; x++) {
			const size_t offset = y * TERM_WIDTH + x;
			term_buffer[offset] = vga_entry(' ', current_color);
		}
	}
}

void term_setcolor(enum vga_colors color) {
	current_color = color;
}

void term_putentryat (char c, uint8_t color, size_t x, size_t y) {
	const size_t offset = y * TERM_WIDTH + x;
	term_buffer[offset] = vga_entry(c, color);
}

void term_putchar(char c) {
	unsigned char uc = c;
	term_putentryat(uc, current_color, terminal_column, terminal_row);
	
	if(++terminal_column == TERM_WIDTH) 
	{
		terminal_column = 0;
		if(++terminal_row == TERM_HEIGHT){
			term_scroll();
			terminal_row = 0;
		}
	}
}

void term_write(const char* data, size_t size) {
	for(size_t i = 0; i < size; i++)
		term_putchar(data[i]);
}

void puts(const char* string) { 
	term_write(string, strlen(string));
	term_putchar('\n');
}

void term_scroll() {
	int current_pos = 160; //Start of the second line.
	
	unsigned char* term_buffer = (unsigned char*) vga_buffer;
	
	while (current_pos <= 4000) {
		term_buffer[current_pos - 160 /*The character immediately below it*/] = vga_buffer[current_pos];      //Move each character up a line
		term_buffer[current_pos - 159 /*The color of the character below*/] = vga_buffer[current_pos + 1];    //As well as its color
		current_pos += 2; //Move to next char
	}
	
	current_pos = 3840; //Start of the last line
	int i; //Offset for framebuffer
	//Wipe out the bottom line
	for(i = 1920; i <= 2000; i++) {
		term_buffer[current_pos] = 0;
		current_pos += 2;
	}
	
	i = 3840;
	terminal_row = 24; //Prepare the screen to scroll
}