#include <stdio.h>
#include <dos.h>
#include <conio.h>

unsigned char getmousestatus(void);
int setleds(char leds);
void interrupt (*tmrint_old)(void);
void interrupt tmrint(void);

void dly(int msec);
void blinkled(unsigned char st);
unsigned int cnt;
unsigned char state;
unsigned char blinkstate;
unsigned int dly_cycles;

const unsigned char led_lit = 0x1;
const unsigned char led_dark = 0x0;

union REGS inregs, outregs;

int main(void) {

	while(!kbhit()) {
		/* check mouse status, program state depends on it */
		state = getmousestatus();
		switch(state) {
			case 0x1: {
				/* left button down, blink mode off, light
				 * capslock and restart main loop
				 */
				blinkled(0x0);
				setleds(0x4);
				break;
			}
			case 0x2: {
				/* right button down, blink mode off, light
				 * numlock only, restart main loop
				 */
				blinkled(0x0);
				setleds(0x2);
				break;
			}
			case 0x3: {
				/* both buttons down, blink mode on */
				blinkled(0x1);
				break;
			}
			default: {
				/* both buttons up, blink mode off,
				 * both leds dark, restart main loop
				 */
				blinkled(0x0);
				setleds(0x0);
				break;
			}
		}
		/* wait 50ms. mouse state can change during blink cycle,
		 * so we need to be ready for it. five delay cycles
		 * forces blinkled() to change led state -> ~2Hz rate
		 */
		dly(50);

	}


	return 0;
}

void blinkled(unsigned char st) {
	if(st) {
		/* about 250ms later and if led is dark, light led and restart
		 * the 250ms wait period. if the led is lit, make it dark and
		 * restart the waiting period.
		 */
		if((blinkstate == led_dark) && (dly_cycles >= 5)) {
			setleds(0x4);
			dly_cycles = 0;
			blinkstate = led_lit;
		} else if((blinkstate == led_lit) && (dly_cycles >= 5)) {
			setleds(0x0);
			dly_cycles = 0;
			blinkstate = led_dark;
		}
	} else {
		/* blink off */
		dly_cycles = 0;
		blinkstate = led_dark;
	}


}
void dly(int msec) {
	/* set counter 0 of 8254 to 1000Hz rate */
	outportb(0x43, 0x30);
	outportb(0x40, 0xa9);
	outportb(0x40, 0x04);
	/* store old interrupt vector, init cnt and
	 * wait for it to reach msec
	 */
	tmrint_old = getvect(0x8);
	setvect(0x8, tmrint);
	cnt = 0;
	while(cnt < msec);

	/* restore old vector and value of counter 0 to 8254 */
	setvect(0x8, tmrint_old);
	outportb(0x43, 0x30);
	outportb(0x40, 0xff);
	outportb(0x40, 0xff);
	/* dly_cycles is used in blinkled() to track how many times
	 * we have been called
	 */
	dly_cycles++;

}

void interrupt tmrint(void) {
	disable();
	cnt++;
	enable();
	if(!(cnt % 55))
		tmrint_old();
	else
		outportb(0x20, 0x20);

}

unsigned char getmousestatus(void) {
	/* bios interrupt 33,3 is used to fetch mouse status */
	unsigned char stat = 0x0;
	inregs.x.ax = 0x3;
	int86(0x33, &inregs, &outregs);
	stat = outregs.x.bx;
	return stat;
}

/* setleds() takes a char variable as parameter.
 * Bit values:
 * 7|6|5|4|3|2|1|0
 *           | | +--- scroll lock led (1 = on, 0 = off)
 *           | +----- num lock led (1 = on, 0 = off)
 *           +------- caps lock led (1 = on, 0 = off)
 * bits 3-7 MUST be zero.
 */
int setleds(char leds) {
	disable();
	/* Prevent keyboard action */
	outportb(0x60, 0xAD);

	/* Set 'change in progress' flag on*/
	pokeb(0x40, 0x97, peekb(0x40, 0x97) | 0x40);

	/* Check if keyboard is ready to receive command */
	if((inportb(0x64) & 2) != 0) {
		/* Keyboard wasn't ready */
		printf("Keyboard not ready\n");
		/* Send Resume to keyboard */
			outportb(0x60, 0xF4);
			enable();
		return 1;
	}

	/* Light leds */
	do {
		outportb(0x60, 0xED);
		outportb(0x60, leds);

	/* Check the given result */
	} while(inportb(0x60) != 0xFA);

	/* Enable keyboard action again */
	outportb(0x60, 0xAE);

	/* Set 'change in progress' flag off*/
	pokeb(0x40, 0x97, peekb(0x40, 0x97) & 0xBF);

	enable();
	return 0;
}