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