#include "vgatext.h"

#include <stdbool.h>

#include "string.h"
#include "stdlib.h"
#include "kernel.h"

static bool params_ok( vga_text_t *vga_text, const int x, const int y );
static int calculate_offset( vga_text_t *vga_text, const int x, const int y );
static uint8_t calculate_color_cell( vga_text_t *vga_text );
static void scroll_screen( vga_text_t *vga_text );

void vga_text_init( vga_text_t *vga_text )
{
	memset( vga_text, 0, sizeof( vga_text_t ) );

	vga_text->res_x = VGA_TEXT_DEFAULT_RES_X;
	vga_text->res_y = VGA_TEXT_DEFAULT_RES_Y;
	vga_text->color = VGA_TEXT_COLOR_DARK_GREY;
	vga_text->background_color = VGA_TEXT_COLOR_BLACK;
	vga_text->show_mouse_cursor = false;
	vga_text->mouse_cursor_x = -1;
	vga_text->mouse_cursor_y = -1;

	// make sure we use the 0x3dx VGA_TEXT ports, is done
	// in assembly in stage 2 too
	port8_init( &vga_text->crtc_misc_port, 0x3d2 );
	port8_write( &vga_text->crtc_misc_port, 1 );

	// set up VGA_TEXT ports
	port8_init( &vga_text->crtc_index_port, 0x3d4 );
	port8_init( &vga_text->crtc_data_port, 0x3d5 );
	
	vga_text_set_cursor_from_hardware( vga_text );	
};

void vga_text_clear_screen( vga_text_t *vga_text )
{
	uint8_t *VIDEO_MEMORY = (uint8_t *)0xb8000;

	for( int i = 0; i < 2 * ( vga_text->res_x * vga_text->res_y ); i += 2 ) {
		*(VIDEO_MEMORY+i) = ' ';
		*(VIDEO_MEMORY+i+1) = calculate_color_cell( vga_text );
	}
	
	vga_text_set_cursor( vga_text, 0, 0 );
}

void vga_text_set_cursor( vga_text_t *vga_text, const int x, const int y )
{
	if( !params_ok( vga_text, x, y ) ) {
		kernel_panic( "Cursor parameters out of bounds: (%d, %d), resolution is only (%d, %d)",
			x, y, vga_text->res_x, vga_text->res_y );
	}

	vga_text->cursor_x = x;
	vga_text->cursor_y = y;
	
	// TODO: have a silent mode where we don't update the cursor
	vga_text_set_cursor_on_hardware( vga_text );
}

void vga_text_set_cursor_from_hardware( vga_text_t *vga_text )
{
	uint16_t hw_cursor_pos;
	
	port8_write( &vga_text->crtc_index_port, 14 );
	uint8_t data = port8_read( &(vga_text->crtc_data_port ) );
	hw_cursor_pos = data << 8;
 
	port8_write( &vga_text->crtc_index_port, 15 );
	data = port8_read( &(vga_text->crtc_data_port ) );

	hw_cursor_pos |= data;
	
	vga_text->cursor_x = hw_cursor_pos % vga_text->res_x;
	vga_text->cursor_y = hw_cursor_pos / vga_text->res_x;
	
	// reset to sane values if we get funny values from the VGA_TEXT card
	if( vga_text->cursor_x < 0 || vga_text->cursor_x > vga_text->res_x ||
		vga_text->cursor_y < 0 || vga_text->cursor_y > vga_text->res_y ) {
		vga_text->cursor_x = 0;
		vga_text->cursor_y = 0;
	}
}

void vga_text_set_cursor_on_hardware( vga_text_t *vga_text )
{
    uint16_t hw_cursor_pos = vga_text->cursor_x + vga_text->cursor_y * vga_text->res_x;

    port8_write( &vga_text->crtc_index_port, 15 );
    port8_write( &vga_text->crtc_data_port, hw_cursor_pos & 0xff );
    port8_write( &vga_text->crtc_index_port, 14 );
    port8_write( &vga_text->crtc_data_port, hw_cursor_pos >> 8 );
}

int vga_text_get_cursor_x( vga_text_t *vga_text )
{
	return vga_text->cursor_x;
}

int vga_text_get_cursor_y( vga_text_t *vga_text )
{
	return vga_text->cursor_y;
}

void vga_text_set_color( vga_text_t *vga_text, const vga_text_color_t color )
{
	vga_text->color = color;
}

void vga_text_set_background_color( vga_text_t *vga_text, const vga_text_color_t color )
{
	vga_text->background_color = color;
}

static int calculate_offset( vga_text_t *vga_text, const int x, const int y )
{
	int offset = ( vga_text->res_x * y + x ) * 2;
	
	return offset;
}

static void scroll_screen( vga_text_t *vga_text )
{
	uint8_t *VIDEO_MEMORY = (uint8_t *)0xb8000;
	
	memmove( (void *)VIDEO_MEMORY, (const void *)VIDEO_MEMORY + 2 * vga_text->res_x, 2 * ( vga_text->res_y - 1 ) * vga_text->res_x );

	for( int i = 2 * ( vga_text->res_x * ( vga_text->res_y - 1 ) ); i < 2 * ( vga_text->res_x * vga_text->res_y ); i += 2 ) {
		*(VIDEO_MEMORY+i) = ' ';
		*(VIDEO_MEMORY+i+1) = calculate_color_cell( vga_text );
	}
	
	vga_text->cursor_y = vga_text->res_y - 1;
}

static uint8_t calculate_color_cell( vga_text_t *vga_text )
{
	uint8_t cell;
	
	cell = ( vga_text->background_color << 4 ) | vga_text->color;
	
	return cell;
}

static bool params_ok( vga_text_t *vga_text, const int x, const int y )
{
	if( x < 0 || x > vga_text->res_x || y < 0 || y > vga_text->res_y ) {
		return false;
	}

	return true;
}

void vga_text_put_char_at( vga_text_t *vga_text, const int x, const int y, const char c )
{
	vga_text_set_cursor( vga_text, x, y );
	vga_text_put_char( vga_text, c );
}


void vga_text_put_string_at( vga_text_t *vga_text, const int x, const int y, const char *s )
{
	vga_text_set_cursor( vga_text, x, y );
	vga_text_put_string( vga_text, s );	
}

void vga_text_put_char( vga_text_t *vga_text, const char c )
{		
	int offset = calculate_offset( vga_text, vga_text->cursor_x, vga_text->cursor_y );

	uint8_t *VIDEO_MEMORY = (uint8_t *)0xb8000;
	*(VIDEO_MEMORY+offset) = (uint8_t)c;
	*(VIDEO_MEMORY+offset+1) = calculate_color_cell( vga_text );	

	vga_text->cursor_x++;
	if( vga_text->cursor_x >= vga_text->res_x ) {
		vga_text->cursor_x = 0;
		vga_text->cursor_y++;
		if( vga_text->cursor_y >= vga_text->res_y ) {
			scroll_screen( vga_text );
		}
	}

	vga_text_set_cursor_on_hardware( vga_text );
}

void vga_text_put_string( vga_text_t *vga_text, const char *s )
{
	for( size_t i = 0; i < strlen( s ); i++ ) {
		vga_text_put_char( vga_text, s[i] );
	}
}

void vga_text_put_newline( vga_text_t *vga_text )
{
	vga_text->cursor_x = 0;
	vga_text->cursor_y++;
	if( vga_text->cursor_y >= vga_text->res_y ) {
		scroll_screen( vga_text );
	}

	vga_text_set_cursor_on_hardware( vga_text );
}

void vga_text_set_background_color_at( vga_text_t *vga_text, const int x, const int y, vga_text_color_t color )
{
	int offset = calculate_offset( vga_text, x, y );

	uint8_t *VIDEO_MEMORY = (uint8_t *)0xb8000;
	*(VIDEO_MEMORY+offset+1) = ( *(VIDEO_MEMORY+offset+1) & 0x0f ) | ( color << 4 );
}

vga_text_color_t vga_text_get_background_color_at( vga_text_t *vga_text, const int x, const int y )
{
	int offset = calculate_offset( vga_text, x, y );

	uint8_t *VIDEO_MEMORY = (uint8_t *)0xb8000;
	uint8_t cell = *(VIDEO_MEMORY+offset+1);

	return cell & 0xf0;
}

void vga_text_inverse_colors_at( vga_text_t *vga_text, const int x, const int y )
{
	int offset = calculate_offset( vga_text, x, y );

	uint8_t *VIDEO_MEMORY = (uint8_t *)0xb8000;
	*(VIDEO_MEMORY+offset+1) = ( ( *(VIDEO_MEMORY+offset+1) & 0x0f ) << 4 )
		| ( ( *(VIDEO_MEMORY+offset+1) & 0xf0 ) >> 4 );
}

void vga_text_show_mouse_cursor( vga_text_t *vga_text )
{
	if( !vga_text->show_mouse_cursor ) {
		vga_text->show_mouse_cursor = true;
		vga_text_inverse_colors_at( vga_text, vga_text->mouse_cursor_x, vga_text->mouse_cursor_y );
	}
}

void vga_text_move_mouse_cursor( vga_text_t *vga_text, const int x, const int y )
{
	if( vga_text->show_mouse_cursor ) {
		vga_text_inverse_colors_at( vga_text, vga_text->mouse_cursor_x, vga_text->mouse_cursor_y );
	}
	
	vga_text->mouse_cursor_x = x;
	vga_text->mouse_cursor_y = y;
	
	if( vga_text->show_mouse_cursor ) {
		vga_text_inverse_colors_at( vga_text, vga_text->mouse_cursor_x, vga_text->mouse_cursor_y );
	}
}

void vga_text_hide_mouse_cursor( vga_text_t *vga_text )
{
	if( vga_text->show_mouse_cursor ) {
		vga_text_inverse_colors_at( vga_text, vga_text->mouse_cursor_x, vga_text->mouse_cursor_y );
		vga_text->show_mouse_cursor = false;
	}
}

void vga_text_save( vga_text_t *vga_text )
{
	uint8_t *VIDEO_MEMORY = (uint8_t *)0xA0000;

	memcpy( vga_text->buf, (const uint8_t *)VIDEO_MEMORY, 2*65535 );
}

void vga_text_restore( vga_text_t *vga_text )
{
	uint8_t *VIDEO_MEMORY = (uint8_t *)0xA0000;

	memcpy( (void *)VIDEO_MEMORY, (const uint8_t *)vga_text->buf, 2*65535 );
}