#include "globals.h"


struct {		// information for the keyboard handler
	char enabled;		// hook enabled
} keyb_handler_info;

volatile char keyb[256];	// all keys if pressed or not

unsigned char scancode2ascii[256] = {	// lookup table to convert scancodes to ascii
  0, 0, 49, 50, 51, 52, 53, 54, 55, 56,//0-9
  57, 48, 45, 0, 0, 0, 113, 119, 101, 114,//10-19
  116, 121, 117, 105, 111, 112, 0, 0, 0, 0,//20-29
  97, 115, 100, 102, 103, 104, 106, 107, 108, 0,//30-39
  0, 0, 0, 0, 122, 120, 99, 118, 98, 110,//40-49
  109, 44, 46, 47, 0, 0, 0, 32, 0, 0,//50-59
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0};

_go32_dpmi_seginfo old_keyb_handler_seginfo, new_keyb_handler_seginfo;


void keyb_handler() {	// called by the system if a key is pressed, stores the key in the last_keys array and the keyb array
	unsigned char key;		// temporarily stores the key
	static char extended;	// saves if the last character used the 8th bit
	int c1;				// iteration variable

	key = inportb(0x60);	// 0x60 seems to be the keyboard port

	if (key == 0xe0)		// next key is a special extended key
		extended = 1;
	else {
		if (extended == 0) {
			if ( (key & 0x80) == 0) {	// key is pressed
				keyb[key & 0x7f] = 1;	// scan code is all but hightést bit, so mark this key as pressed
				for (c1 = 48; c1 > 0; c1--)		// each character in the last_keys array
					last_keys[c1] = last_keys[c1 - 1];	// has to go one step back to
				last_keys[0] = scancode2ascii[key & 0x7f];	// make place for the new character
			}
			else
				keyb[key & 0x7f] = 0;	// mark as not pressed
		}
		else {
			if ( (key & 0x80) == 0) {	// extended key handling
				keyb[(key & 0x7f) + 0x80] = 1;	// are saved at upper positions in array
				for (c1 = 48; c1 > 0; c1--)
					last_keys[c1] = last_keys[c1 - 1];
				last_keys[0] = scancode2ascii[(key & 0x7f) + 0x80];
			}
			else
				keyb[(key & 0x7f) + 0x80] = 0;
		}
		if (extended == 1)	// reset extended flag, if clause is senseless
			extended = 0;
	}

	outportb(0x20, 0x20);	// handled?? or iret??

}

void keyb_handler_end() {}			// marks the end of the code of keyb_handler()


char hook_keyb_handler(void) {		// enables the keyboard hook

	if (keyb_handler_info.enabled == 0) {	// only if not already enabled
		_go32_dpmi_lock_data( (char *)&keyb, sizeof(keyb) );	// locks the memory region of the keyb array
		_go32_dpmi_lock_code(keyb_handler, (unsigned long)keyb_handler_end - (unsigned long)keyb_handler);		// locks the code region of keyb_handler
		_go32_dpmi_get_protected_mode_interrupt_vector(9, &old_keyb_handler_seginfo);	// store old keyboard handler
		new_keyb_handler_seginfo.pm_offset = (int)keyb_handler;	// function to call if a key is pressed is keyb_handler
		if (_go32_dpmi_allocate_iret_wrapper(&new_keyb_handler_seginfo) != 0)		// register this function
			return 1;
		if (_go32_dpmi_set_protected_mode_interrupt_vector(9, &new_keyb_handler_seginfo) != 0) {	// another part of it
			_go32_dpmi_free_iret_wrapper(&new_keyb_handler_seginfo);
			return 1;
		}
		keyb_handler_info.enabled = 1;		// keyboard hook is now enabled
		memset(last_keys, 0, sizeof(last_keys) );	// clear the last_keys array
	}

	return 0;

}


void remove_keyb_handler(void) {	// disables they interrupt handler

	if (keyb_handler_info.enabled == 1) {
		_go32_dpmi_set_protected_mode_interrupt_vector(9, &old_keyb_handler_seginfo);	// restore old handler
		_go32_dpmi_free_iret_wrapper(&new_keyb_handler_seginfo);	// free interrupt capturing
		keyb_handler_info.enabled = 0;	// handler is disabled
	}

}


char key_pressed(unsigned char key) {	// returns if a key is pressed

	return keyb[key];

}