XDEF _takeOverSystem
  XDEF _giveBackSystem
  XDEF _initializeCopperlist
  XDEF _setUpDisplay
  XDEF _setUpEmptySpritesInCopperlist
  XDEF _addDisplayToCopperlist
  XDEF _updateDisplayInCopperList
  XDEF _addColorsToCopperlist
  XDEF _endCopperlist
  XDEF _myWaitBlit
  XDEF _WaitBOF
  XDEF _KeyboardHandler

  XDEF _keyboardPressed

  XREF _custom

FUNC_CNT SET -30
FUNCDEF MACRO
_LVO\1 EQU FUNC_CNT
FUNC_CNT SET FUNC_CNT-6
  ENDM

  INCDIR "include_i_39:"
  INCDIR "extra_lvos_39:"
  INCLUDE "exec/exec_lib.i"
  INCLUDE "exec/types.i"
  INCLUDE "exec/execbase.i"
  INCLUDE "exec/libraries.i" # get the CALLLIB macro
  INCLUDE "graphics/gfxbase.i"
  INCLUDE "graphics_lvo.i"
  INCLUDE "hardware/custom.i"
  INCLUDE "hardware/dmabits.i"
  INCLUDE "hardware/intbits.i"
  INCLUDE "exec/io.i"
  INCLUDE "devices/inputevent.i"

; @param 1 Pointer to null terminated name of library
; @param 2 Minimum version of library, 0 for any
; @outreg D0 pointer to library in memory
OpenLibrary MACRO
  MOVE.L 4,A6
  MOVEM.L A1,-(SP)
    MOVE.L \1,A1
    MOVE.L \2,D0
    CALLLIB _LVOOpenLibrary
  MOVEM.L (SP)+,A1
  ENDM

PreserveRegister MACRO
  MOVE.L D0,-(SP)
    LEA _custom,A0
    MOVE.W \1r(A0),D0
    OR.W #$8000,D0
    MOVE.W D0,Old\1
  MOVE.L (SP)+,D0
  ENDM

RestoreRegister MACRO
  MOVE.W #$7FFF,\1(A0)
  MOVE.W Old\1,\1(A0)
  ENDM

  STRUCTURE ScreenDefinition,0
  UWORD ScreenDefinition_width
  UWORD ScreenDefinition_height
  UWORD ScreenDefinition_bitplanes
  ULONG ScreenDefinition_memoryStart
  UWORD ScreenDefinition_byteWidth
  UWORD ScreenDefinition_nextBitplaneAdvance
  UWORD ScreenDefinition_nextBufferAdvance
  ULONG ScreenDefinition_copperlistBitplanePointers
  LABEL ScreenDefinition_SIZEOF

  STRUCTURE ActiveScreenBufferDetails,0
  UWORD ActiveScreenBufferDetails_currentBuffer
ActiveScreenBufferDetails_planes EQU SOFFSET
SOFFSET SET SOFFSET+(8*4)
  LABEL ActiveScreenBufferDetails_SIZEOF

; @see https://amigadev.elowar.com/read/ADCD_2.1/Devices_Manual_guide/node019A.html
; @register A0 struct InputEvent *
; @register A1 extra data about the event
; @output D0 The value of A0
_KeyboardHandler:
  ; @stack [RA,A0,current node]
  MOVE.L A0,-(SP)
    MOVE.L #0,-(SP)

_KeyboardHandler_CheckLoop:
      CMP.B #IECLASS_RAWKEY,ie_Class(A0)
      BNE.S _KeyboardHandler_NextEvent

      MOVE.W ie_Code(A0),D0
      AND.W #IECODE_UP_PREFIX,D0
      SEQ _keyboardPressed

      ; if next_event:
      ;   do the stack swap thing below
      ; else:
      ;   change the A0 in the stack above it
      TST.L (SP)
      BNE.S _KeyboardHandler_hasLastEvent

      MOVE.L (A0),4(SP)
      BRA.S _KeyboardHandler_NextEvent

_KeyboardHandler_hasLastEvent:
      ; put the next event in the first pointer of the
      ; last event
      MOVE.L A1,-(SP)
        MOVE.L 4(SP),A1
        MOVE.L (A0),(A1)
      MOVE.L (SP)+,A1

_KeyboardHandler_NextEvent:
      ; next event is in first long of struct
      MOVE.L (A0),D0
      ; store current node in stack
      MOVE.L A0,(SP)

      MOVE.L D0,A0
      BNE.S _KeyboardHandler_CheckLoop
    MOVE.L (SP)+,D0
  MOVE.L (SP)+,D0
  RTS

M68K_LEVEL3_INTERRUPT_AUTOVECTOR EQU $6C
_takeOverSystem:
  MOVEM.L A2/A6,-(SP)
    OpenLibrary #GraphicsLibrary,#0
    MOVE.L D0,GraphicsBase

    MOVE.L D0,A6
    MOVE.L gb_ActiView(A6),OldView
    MOVE.L gb_copinit(A6),OldCopper

    MOVE.L #0,A1
    CALLLIB _LVOLoadView
    CALLLIB _LVOWaitTOF
    CALLLIB _LVOWaitTOF

    CALLLIB _LVOOwnBlitter
    CALLLIB _LVOWaitBlit

    LEA _custom,A0

    PreserveRegister dmacon
    PreserveRegister intena
    PreserveRegister intreq
    PreserveRegister adkcon

    ; http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node0036.html
    MOVE.W #$7FFF,intena(A0) ; disable all interrupts
    ; we need VERTB to use WaitTOF
    ; PORTS and EXTER give me access to the keyboard and mouse via OS interrupts
    MOVE.W #INTF_SETCLR|INTF_INTEN|INTF_COPER|INTF_PORTS|INTF_EXTER|INTF_VERTB,intena(A0) ; enable master interrupt, copper, and VBR

    MOVE.W #$7FFF,dmacon(a0)
    MOVE.W #DMAF_SETCLR|DMAF_MASTER|DMAF_COPPER|DMAF_RASTER|DMAF_BLITTER|DMAF_SPRITE,dmacon(A0)
  MOVEM.L (SP)+,A2/A6
  RTS

; @outreg D0 pointer to VBR
GetVBR:
  MOVE.L A5,-(SP)
    MOVEQ #0,D0
    MOVE.L $4,A6
    BTST #0,AttnFlags+1(A6)
    BEQ.B .zIs68K
    LEA Get68010VBR(pc),A5
    CALLLIB _LVOSupervisor
.zIs68K:
  MOVE.L (SP)+,A5
  RTS

Get68010VBR:
  DC.L $4E7A0801
  RTE

NewLevel3VBI:
  MOVEM.L D0-A6,-(SP)
    MOVE.L VBIPtr,D0
    BEQ.B .noVBI
    MOVE.L D0,A0
    JSR (A0)
.noVBI:
    LEA _custom,A6
    LEA intreq(A6),A6
    MOVEQ #$20,D0
    MOVE.W D0,(A6)
    MOVE.W D0,(A6) ; there is a bug in the 4000?
  MOVEM.L (SP)+,D0-A6
  RTE

_giveBackSystem:
  MOVE.L A6,-(SP)
    LEA _custom,A0

    RestoreRegister dmacon
    RestoreRegister intena
    RestoreRegister intreq
    RestoreRegister adkcon

    MOVE.L OldCopper,cop1lc(A0)
    MOVE.L GraphicsBase,A6
    MOVE.L OldView,A1
    CALLLIB _LVOLoadView
    CALLLIB _LVOWaitTOF
    CALLLIB _LVOWaitTOF
    CALLLIB _LVOWaitBlit
    CALLLIB _LVODisownBlitter
  MOVE.L (SP)+,A6
  RTS

; @stack *copperlist Pointer to copperlist
_initializeCopperlist:
  MOVE.L 4(A7),A0
  MOVE.L #$FFFFFFFE,(A0)

  RTS

; @stack *copperlist Pointer to copperlist
; @stack ScreenDefinition Pointer to screenSetup struct
; @stack ActiveScreenBufferDetails Pointer to currentScreen struct
; @stack copperlistBitplanePointers Pointer to bitplane pointers within the copper list [[high, low], ...]
  STRUCTURE updateDisplayInCopperList,4
  ULONG updateDisplayInCopperList_screenSetup
  ULONG updateDisplayInCopperList_currentScreen
  ULONG updateDisplayInCopperList_copperlistBitplanePointers
_updateDisplayInCopperList:
  MOVE.L updateDisplayInCopperList_screenSetup(A7),A0
  MOVE.L updateDisplayInCopperList_currentScreen(A7),A1
  MOVE.L updateDisplayInCopperList_copperlistBitplanePointers(A7),D0

  MOVEM.L A2-A3/D2,-(SP)
    MOVE.L D0,A2
    ; a2 has copperlistBitplanePointers

    MOVE.W ScreenDefinition_bitplanes(A0),D1
    SUBQ #1,D1
    LEA ActiveScreenBufferDetails_planes(A1),A1
    ; a1 has planes

.continue:
    MOVE.L (A1)+,D2
    ; d2 has bitplane pointer

    MOVE.L (A2)+,A3
    ; a3 has high copperlist bitplane pointer
    SWAP D2
    MOVE.W D2,(A3)
    MOVE.L (A2)+,A3
    ; a3 has low copperlist bitplane pointer
    SWAP D2
    MOVE.W D2,(A3)

    DBRA D1,.continue
  MOVEM.L (SP)+,A2-A3/D2

  RTS

; Populate all 8 sprite pointers with the
; address to an empty sprite.
;
; @stack *copperlist Pointer to copperlist
; @outreg D0 Current pointer to copperlist
_setUpEmptySpritesInCopperlist:
  MOVE.L 4(A7),A1

  MOVE.L D2,-(SP)
    MOVEQ #7,D0
    MOVEQ #0,D1
    MOVE.W #sprpt,D1
    LEA EmptySprite,A0
    MOVE.L A0,D2
.spritewrite:
    SWAP D2
    MOVE.W D1,(A1)+
    MOVE.W D2,(A1)+
    ADDQ #2,D1
    SWAP D2
    MOVE.W D1,(A1)+
    MOVE.W D2,(A1)+
    ADDQ #2,D1
    DBRA D0,.spritewrite
  MOVE.L (SP)+,D2
  MOVE.L A1,D0

  RTS

; @stack *copperlist Pointer to copperlist
; @stack ScreenDefinition Pointer to screenDefinition struct
; @stack ActiveScreenBufferDetails Pointer to activeScreenBufferDetails struct
; @stack copperlistBitplanePointers Pointer to copperlistBitplanePointers struct
  STRUCTURE AddDisplayToCopperListParams,4
  ULONG AddDisplayToCopperListParams_copperlistPtr
  ULONG AddDisplayToCopperListParams_screenDefinitionPtr
  ULONG AddDisplayToCopperListParams_activeScreenBufferDetailsPtr
  ULONG AddDisplayToCopperListParams_copperlistBitplanePointersPtr
_addDisplayToCopperlist:
  MOVE.L A7,A0

  ; A2,D2,D3
  MOVEM.L A2-A4/D2-D4,-(SP)
    MOVE.L AddDisplayToCopperListParams_copperlistPtr(A0),A1 ; copperlist
    MOVE.L AddDisplayToCopperListParams_screenDefinitionPtr(A0),A2 ; screenDefinition
    MOVE.L AddDisplayToCopperListParams_activeScreenBufferDetailsPtr(A0),A3 ; currentScreen
    MOVE.L AddDisplayToCopperListParams_copperlistBitplanePointersPtr(A0),A4 ; copperlistBitplanePointers

    LEA ActiveScreenBufferDetails_planes(A3),A3
    ; a3 contains address to planes

    MOVEQ #0,D0
    MOVE.W ScreenDefinition_bitplanes(A2),D0
    ; d0 is num of bitplanes

    ; set up bplpt
    MOVEQ #0,D1
    ADD.W #bplpt,D1
    ; d1 contains bltpt

    MOVEQ #0,D4
.continue:
    ; get plane to split up
    MOVE.L (A3)+,D3

    ; high byte
    SWAP D3
    MOVE.W D1,(A1)+
    ; get this position for later updating
    MOVE.L A1,(A4)+
    MOVE.W D3,(A1)+
    ADDQ #2,D1

    ; low byte
    SWAP D3
    MOVE.W D1,(A1)+
    ; get this position for later updating
    MOVE.L A1,(A4)+
    MOVE.W D3,(A1)+
    ADDQ #2,D1

    ADDQ #1,D4
    CMP D4,D0
    BNE .continue

    ; current copperlist position
    MOVE.L A1,D0
  MOVEM.L (SP)+,A2-A4/D2-D4

  RTS

; @stack *copperlist
; @stack *colors
; @stack count
_addColorsToCopperlist:
  MOVE.L 4(A7),A0 ; copperlist
  MOVE.L 8(A7),A1 ; colors
  MOVE.L 12(A7),D0 ; count

  MOVEM.L A2/D2,-(SP)
    LEA _custom,A2
    MOVE.L #color,D2
    ADD.L D2,A2

    SUBQ #1,D0
.continue:
    MOVE.W (A1)+,(A2)+
    DBRA D0,.continue
    MOVE.L A2,D0
  MOVEM.L (SP)+,A2/D2

  RTS

; @stack *copperlist
_endCopperlist:
  MOVE.L 4(A7),A0

  MOVE.W #$ffff,(A0)+
  MOVE.W #$fffe,(A0)+
  MOVE.L A0,D0

  RTS

BPLCON0_ENABLE_COMPOSITE_COLOR EQU $200

; TODO: [ ] Create a stock display structure w/ all the default values in it
;           that can be overridden, with guides/help on how to do so, then
;           have this accept that structure
; @stack bitplaneCount
_setUpDisplay:
  MOVE.L D2,-(SP)
    MOVE.L 8(A7),D2 ; bitplaneCount

    LEA _custom,A1

    MOVEQ #0,D0
    MOVE.W #BPLCON0_ENABLE_COMPOSITE_COLOR,D0

    ; move bitplane count to bits 12-14
    MOVEQ #0,D1
    MOVE.W D2,D1
    AND.W #$7,D1
    ROL.W #8,D1
    ROL.W #4,D1
    ADD.W D1,D0

    MOVE.W D0,bplcon0(A1)

    ; this controls horizontal scroll. I'm not good enough
    ; yet to provide opinions on this.
    MOVE.W #0,bplcon1(A1)

    ; sprites always on top for this demo
    MOVE.W #$0020,bplcon2(A1)

    ; no modulos needed
    MOVE.W #0,bpl1mod(A1)
    MOVE.W #0,bpl2mod(A1)

    ; pal default
    MOVE.W #$2c81,diwstrt(A1)
    MOVE.W #$2cc1,diwstop(A1)
    MOVE.W #$0038,ddfstrt(A1)
    MOVE.W #$00d0,ddfstop(A1)
  MOVE.L (SP)+,D2

  RTS

_myWaitBlit:
  LEA _custom,A0

  BTST.B #DMAB_BLTDONE-8,dmaconr(A0)
  BTST.B #DMAB_BLTDONE-8,dmaconr(A0)
  BEQ .done

.loop:
  BTST.B #DMAB_BLTDONE-8,dmaconr(A0)
  BNE .loop

.done:
  RTS

_WaitBOF:
  MOVE.W 4(A7),D1
  ROL.L #8,D1

  MOVE.L $dff004,D0
  AND.L #$1ff00,D0
  CMP.L D1,D0
  BNE.B _WaitBOF

.loop2:
  MOVE.L $dff004,D0
  AND.L #$1ff00,D0
  CMP.L D1,D0
  BEQ.B .loop2

  RTS

  CNOP 0,4
GraphicsBase dc.l 0

; old graphics stuff
OldView dc.l 0
OldCopper dc.l 0

; old registers
Olddmacon dc.w 0
Oldintena dc.w 0
Oldintreq dc.w 0
Oldadkcon dc.w 0

; vertical blank interrupt and the vector base register
OldLevel3VBI dc.l 0
VBRPtr dc.l 0

; you can set this to your own interrupt
VBIPtr dc.l 0

  CNOP 0,4
GraphicsLibrary GRAPHICSNAME

  CNOP 0,4
_keyboardPressed dc.l 0

  SECTION Sprite,Data_C
EmptySprite dc.w 0,0