BITS 16

;;;;;;;;;;;;;;
; CONSTANTS
;;;;;;;;;;;;;;
stacksize       EQU 0200h
; starting address of video memory

videobase       EQU 0a000h

; some colors

black           EQU 0
green           EQU 00110000b
blue            EQU 00001001b
red             EQU 00000100b
white           EQU 00001111b
grey            EQU 00000111b
yellow          EQU 00001110b
transparent     EQU 11111111b  ;Note: this is our convention for this exercise - see the bitmap copy later...

; screen width in pixels, in the graphics mode 320x200

scrwidth    EQU 320

;;;;;;;;;;;;;;
; DATA AND STACK SEGMENTS
;;;;;;;;;;;;;;

segment memscreen data
	resb 320*200

segment background data
	resb 320*200

segment mystack stack
	resb stacksize
stacktop:

segment mydata data
	; DEFINE YOUR VARIABLES HERE
	foo	resw	1
	pressesc dw	0
	oldintseg resw	1
	oldintoff resw	1
	delay dw	2
	oldgramod resw	1
	move dw		6
	pacmanloc dw	32160
	toofast dw	0

segment bitmaps data
PacmanMap db transparent,transparent,transparent,transparent,yellow,yellow,yellow,transparent,transparent,transparent,transparent,transparent,transparent,yellow,yellow,yellow,yellow,yellow,yellow,yellow,transparent,transparent,transparent,yellow,yellow,yellow,yellow,yellow,yellow,yellow,yellow,yellow,transparent,transparent,yellow,yellow,yellow,yellow,yellow,yellow,yellow,transparent,transparent,transparent,yellow,yellow,yellow,yellow,yellow,yellow,transparent,transparent,transparent,transparent,transparent,yellow,yellow,yellow,yellow,transparent,transparent,transparent,transparent,transparent,transparent,transparent,yellow,yellow,yellow,yellow,yellow,yellow,transparent,transparent,transparent,transparent,transparent,transparent,yellow,yellow,yellow,yellow,yellow,yellow,yellow,transparent,transparent,transparent,transparent,yellow,yellow,yellow,yellow,yellow,yellow,yellow,yellow,yellow,transparent,transparent,transparent,yellow,yellow,yellow,yellow,yellow,yellow,yellow,transparent,transparent,transparent,transparent,transparent,transparent,yellow,yellow,yellow,transparent,transparent,transparent,transparent

;;;;;;;;;;;;;;
; The code segment - YOUR CODE HERE
;;;;;;;;;;;;;;

segment mycode code

; Subroutines here

KeybInt:
        push    ds              ; push the value of ds and ax to safety
        push    ax
        mov     ax,mydata       ; Re-initialisation of
        mov     ds,ax           ; the data segment
        cli                     ; Disable other interrupts
	                            ; during this one

.getstatus:
        in      al, 64h
        test	al, 02h
        loopnz	.getstatus      ; wait until the port is ready
        in      al,60h          ; Get the scan code of the pressed/released key

	    ; here begins the actual key scanning
        cmp     al, 01h		    ; 1 is the 'make code' for ESC
        jne     .cplus		    ; if ESC was not pressed, continue
        mov     word [pressesc], 1
	    jmp    .kbread
.cplus:
	    cmp 	al, 04Eh	; 4E is the 'make code' for keypad plus
	    jne 	.cminus
	    add		word [delay], 1
	    jmp     .kbread
.cminus:
	    cmp 	al, 04Ah	; 4A is the 'make code' for keypad minus
	    jne		.cright
	    sub		word [delay], 1
		jmp     .kbread
.cright
		cmp		al, 04Dh
		jne		.cleft
		mov word [move], 6
	    jmp     .kbread
.cleft
		cmp		al, 04Bh
		jne		.cup
		mov word [move], -6
	    jmp     .kbread
.cup
		cmp		al, 048h
		jne		.cdown
		mov word [move], -1920
	    jmp     .kbread
.cdown
		cmp		al, 050h
		jne		.kbread
		mov word [move], 1920
.kbread:
        in      al,61h          ; Send acknowledgment without
        or      al,10000000b    ; modifying the other bits.
        out     61h,al          ;
        and     al,01111111b    ;
        out     61h,al          ;
        mov     al,20h          ; Send End-of-Interrupt signal
        out     20h,al          ;
        sti                     ; Enable interrupts again
        pop     ax
   	    pop 	ds       		; Regain the ds,ax from stack
        iret	                ; Return from interrupt

movePacman:
	mov word ax, [move]
	add word [pacmanloc], ax
	ret

copybitmap:
    ;PARAMETERS:
    ;   SI contains the offset address of the bitmap
    ;   DI contains the target coordinate
    ;   ES contains the target segment
    ;   CX contains the bitmap row count
    ;   DX contains the bitmap col count
    push ds
    pusha
    ;Segment registers to correct locations
    mov ax, bitmaps
    mov ds, ax
    .rowloop:
        push cx
        push di
        mov cx, dx
        .colloop:
            mov byte bl, [ds:si]
            cmp byte bl, transparent
            je .skip
            mov byte [es:di], bl
            .skip:
            inc di
            inc si
            loop .colloop
        pop di
        add di, 320
        pop cx
        loop .rowloop
    popa
    pop ds
	ret

drawPacman:
	push cx
	push dx
    mov si, 1
	mov di, [pacmanloc]
    mov ax, memscreen
	mov es, ax
    mov dx, 11
	mov cx, 11
	call copybitmap
	pop cx
	pop dx
	ret



initBackground:
	mov ax, background        ; test draw for pixels
	mov es, ax               ; move video memory address to ES
	mov di, 0                ; move the desired offset address to DI
hyppy1:
	mov byte [es:di], blue   ; Move the constant 'blue' (hopefully corresponding to blue colour) to the video memory at offset DI
	inc di                   ; Change the offset address
	cmp di, 320
	jne hyppy1
	mov di, 63680
hyppy2:
	mov byte [es:di], blue   ; Move the constant 'blue' (hopefully corresponding to blue colour) to the video memory at offset DI
	inc di                   ; Change the offset address
	cmp di, 64000
	jne hyppy2
	mov di, 0
hyppy3:
	mov byte [es:di], blue
	add di, 320
	cmp di, 64000
	jne hyppy3
	mov di, 319
hyppy4:
	mov byte [es:di], blue
	add di, 320
	cmp di, 64319
	jne hyppy4
	ret

draw:
	call copybackground
    call drawPacman
	call copymemscreen
	ret


copybackground:
    push ds
    pusha
    ;Pointers
    mov word si, 0
    mov word di, 0
    mov cx, 64000

    ;Segment registers to correct locations
    mov ax, memscreen
    mov es, ax
    mov ax, background
    mov ds, ax

    ;REPEAT COPY!
    rep movsb
    popa
    pop ds
    ret

copymemscreen:
    push ds
    pusha
    ;Pointers
    mov word si, 0
    mov word di, 0
    mov cx, 64000

    ;Segment registers to correct locations
    mov ax, videobase
    mov es, ax
    mov ax, memscreen
    mov ds, ax

    ;REPEAT COPY!
    rep movsb
    popa
    pop ds
    ret

iscolour:
    push di
    push cx
    push dx
    mov ax, 0
    .rowloop:
        push cx
        push di
        mov cx, dx
        .colloop:
            cmp byte [es:di], bl
            jne .ok
                inc ax
            .ok:
            inc di
            loop .colloop
        pop di
        add di, 320
        pop cx
        loop .rowloop
    pop dx
    pop cx
    pop di
    ret

respectwall:
	mov word di, [move]
	add word di, [pacmanloc]
	mov cx, 11
	mov dx, 11
	mov ax, bitmaps
    mov es, ax
	call iscolour
	ret

..start:

	mov		ax, 3509h  ;saving the old interrupt address
	int		21h
	mov		word [oldintseg], es
	mov		word [oldintoff], bx


	mov     ax, mydata
	mov     ds, ax
    mov     ax, mystack
    mov     ss, ax
    mov     sp, stacktop


	push	ds
	mov		ax, mycode  ;setting the new interrupt
	mov		ds, ax
	mov		dx, KeybInt
	mov		ax, 2509h
	int		21h
	pop		ds

	mov		ah, 0fh   ; fetching the old graphics mode and storing it to a variable
	int		10h
	mov		word [oldgramod], ax

	mov		ax, 0013h  ; setting the new graphics mode
	int		10h

	call initBackground
.mainloop:
	mov word dx, [delay]  ; delay for game speed
.pause1:
	mov cx, 65535
.pause2:
	dec cx
	jne .pause2
	dec dx
	jne .pause1

	call draw
	call respectwall ;pacman should recognize the wall...
	cmp ax, 0
	jne .jumppi
	add word [toofast], 1  ;if pacman moves too fast
	cmp word [toofast], 2
	jne .jumppi
	call movePacman
	mov word [toofast], 0
.jumppi:
	cmp		word [pressesc], 1; check if pressed esc
	jne		.mainloop

.dosexit:

    mov     word ax, [oldgramod]  ; setting the old graphics mode back
    mov     ah, 00h
    int     10h

	push	ds
	mov		word dx, [oldintoff] ; Move VALUE at address oldintoff to DX (not the address!)  restoring the old interrupt here!!!
	mov		word ax, [oldintseg]; Move VALUE at address oldintseg to DS, step 1 (remember you cannot move directly to segment registers)
	mov		ds, ax; Move VALUE at address oldintseg to DS, step 2
	mov		ax, 2509h ; Move parameters to AH and AL (or both together by moving to AX). Interrupt number is still 9 and AH should be 25h (note hexadecimal)
	int		21h ; Finally, set the interrupt vector by calling int 21H
	pop		ds

	mov	al, 0    ; ending the program with INT 21,4c
	mov     ah, 4ch
	int     21h

.end