#include <stddef.h>
#include <stdint.h>
 
#include "tty.h"

#include "kernel.h"
#include "interrupt.h"
#include "ioport.h"

#include "string.h"

#include <mem.h>

#define make_color(fg, bg) (fg | bg << 4)
#define make_vga(ch, color) ((uint16_t)(ch & 0xff | color << 8))
 
#define VGA_WIDTH  80
#define VGA_HEIGHT 25
 
static struct virtual_console {
	int row, column;
	uint8_t color;

} con;

struct terminal terminal = { 0 };

static void clear() {
	int i;
	uint16_t blank = make_vga(' ', terminal.color);
	for (i=0; i < VGA_WIDTH * VGA_HEIGHT; i++) {
		terminal.vmem[i] = blank;
	}
}

static void scroll(int lines) {
	uint16_t *base, *offset;
	uint16_t blank;
	int i;

	base = terminal.vmem;
	offset = base + VGA_WIDTH * lines;
	memmove(base, offset, (VGA_WIDTH * VGA_HEIGHT - lines) * 2);

	offset = base + (VGA_WIDTH * VGA_HEIGHT - lines);
	blank = make_vga(' ', terminal.color);
	for (i=0; i < VGA_WIDTH * lines; i++) {
		offset[i] = blank;
	}
}
 
static void putentryat(int c, uint8_t color, size_t x, size_t y) {
	size_t index = y * VGA_WIDTH + x;
	terminal.vmem[index] = make_vga(c, color);
}
 
static void putchar(int c) {
	if (terminal.escape) {
		switch(c) {

		}

		return;
	}

	switch (c) {
		case '\n':
			terminal.column = 0;
			if (++terminal.row == VGA_HEIGHT) {
				terminal.row = VGA_HEIGHT-1;
				scroll(1);
			}
			break;
		case '\r':
			terminal.column = 0;
			break;
		default:
			putentryat(c, terminal.color, terminal.column, terminal.row);
			terminal.column++;
			break;
	}

	if (terminal.column == VGA_WIDTH) {
		terminal.column = 0;
		if (++terminal.row == VGA_HEIGHT) {
			terminal.row = VGA_HEIGHT-1;
			scroll(1);
		}
	}
}

static void setcursor(int row, int col) {
	uint16_t position = (row*VGA_WIDTH) + col;

	/* cursor low port to vga index register */
	outport8(0x3D4, 0x0F);
	outport8(0x3D5, (unsigned char)(position&0xFF));
	/* cursor high port to vga index register */
	outport8(0x3D4, 0x0E);
	outport8(0x3D5, (unsigned char )((position>>8)&0xFF));
}

static void updcursor() {
	setcursor(terminal.row, terminal.column);
}
 
static void writestring(const char *data) {
	size_t i = 0;

	while (data[i]) {
		putchar(data[i++]);
	}
	updcursor();
}

void terminal_initialize() {
	terminal.putchar = putchar;
	terminal.clear = clear;
	terminal.scroll = scroll;
	terminal.writestring = writestring;
	terminal.vc = &con;
	terminal.vmem = (uint16_t *) (0xb8000 + _asm_physmap);
	terminal.update_cursor = updcursor;

	terminal.row = 0;
	terminal.column = 0;
	updcursor();

	terminal.color = make_color(VGA_LIGHT_GREY, VGA_BLACK);

	clear();
}