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#include "textmode.h"

void main()
{
   // BEGIN GRAPHICS INIT
   color(BLACK, WHITE);
   clrscr();
   // END

   print("Hello World!\n");
   colorch('N', WHITE, BLACK);
   colorch('P', BLUE , BTWHITE);
   colorch('/', BLACK, BTWHITE);
   colorch('O', RED  , GRAY);
   colorch('S', GREEN, BTWHITE);
}

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// START : Text color definitions

#define BLACK      0x00
#define BLUE      0x01
#define GREEN      0x02
#define AQUA      0x03
#define RED         0x04
#define PURPLE      0x05
#define YELLOW      0x06
#define WHITE      0x07 // The white is really a light gray. use 0x0F for pure white
#define GRAY      0x08
#define LTBLUE      0x09 // LT stands for LIGHT
#define LTGREEN      0x0A
#define LTAQUA      0x0B
#define LTRED      0x0C
#define LTPURPLE   0x0D
#define LTYELLOW   0x0E
#define BTWHITE      0x0F // BR stands for BRIGHT

// END

char *vmem = (char *)0xb8000;
int colormode = 0x07;
int pos = 0;
int line = 0;

void color(int bgcolor, int fgcolor)
{
   /* well, think of it this way. the color mode
    * is formatted as (BGBIT)(FGBIT). 0x00 is black
    * and 0x07 is white. thus, black background with
    * white text is still 0x07. However, blue (0x01)
    * background with white text would be 0x17
    * (BSOD anyone? hehe, just a joke.)
    * But anyways. in hex, instead of * by 10 to move
    * up a digit like we would in our system of
    * numbers, we would * by 16.
    *
    * now, why is the or there?
    * in hex, if you have 0xF0 and 0x07, 0xF0 |
    * 0x07 = 0xF7. see what im getting at?
    */

   colormode = (bgcolor * 16) | fgcolor;
}

void clrscr()
{
   /* the text mode screen memory works like this:
    * there are 25 rows of possible 80 characters to
    * display, right? well, each character also has a
    * one-byte attribute (color) so, to account for the
    * full size we do 25 * 80 * 2
    */

   for(int i = 0; i < (25 * 80 * 2); ++i)
   {
      vmem[i] = ' ';
      ++i;
      vmem[i] = colormode;
      pos = pos + 2;
   }

   pos = 0;
}

void print(char string[])
{
   int len = (sizeof(string) / sizeof(char)) * 2;
   int spos = 0;
   int lim;

   if((len + (line * 80 * 2) + pos) >= (25 * 80 * 2))
   {
      lim = ((0 - 1) * ((25 * 80 * 2) - (len + (line * 80 * 2) + pos)));
   }
   else
   {
      lim = len;
   }

   for(int i = (line * 80 * 2) + pos; i < lim; ++i)
   {
      if(string[spos] == '\n')
      {
         if(line < 25)
         {
            i = i + ((line + 1) * 80 * 2) - (line * 80 * 2) + pos;
            ++line;
            pos = 0;
            ++spos;
         }
         else
         {
            vmem[i] = ' ';
            ++i;
            vmem[i] = colormode;
            pos = pos + 2;
            ++spos;
         }
      }
      else
      {
         vmem[i] = string[spos];
         ++i;
         vmem[i] = colormode;
         pos = pos + 2;
         ++spos;
      }
   }
}

void colorch(char ch, int bgcolor, int fgcolor)
{
   if(pos == (24 * 2)) // if we are on our last character.....
   {
      ++line;
   }

   int npos = (line * 80) + pos;

   vmem[npos] = ch;
   ++npos;
   vmem[npos] = (bgcolor * 16) | fgcolor;
   pos = pos + 2;
}

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[BITS 32]
[global start]
[extern _main] ; this is in main.cpp

start:
  call _main

  cli  ; stop interrupts
  hlt ; halt the CPU

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for(;;);