;license:MIT
;(c) 2021 by 4am & qkumba
;

!cpu 6502
!to "build/FX.INDEXED/SHR.80BOXES",plain
*=$A000

; The SHR screen in 320x200 mode is separated into 80 boxes.
; Boxes are laid out in a grid, left-to-right, top-down:
;
; 0  1  2  3  4  5  6  7  8  9
; 10 11 12 13 14 15 16 17 18 19
; 20 21 22 23 24 25 26 27 28 29
; 30 31 32 33 34 35 36 37 38 39
; 40 41 42 43 44 45 46 47 48 49
; 50 51 52 53 54 55 56 57 58 59
; 60 61 62 63 64 65 66 67 68 69
; 70 71 72 73 74 75 76 77 78 79
;
; Each box is 32x25 pixels, so each row of each box is 16 consecutive
; bytes in memory (2 pixels per byte) once you calculate the SHR base
; address for that row.
;
; |BoxStages| defines the initial grid of stages for each box.
; Each stage is used as an index into the |StagesHi| array
; to find the drawing routine for that stage (if any).
; Each box's stage is incremented after each iteration through the main loop.
; When the main loop iterates through all 80 boxes without drawing anything,
; the program exits.
;
; There are 7 clear routines that set certain pixels to color 0 (usually black)
; labeled clear00..clear06. clear00 clears the inner-most box, and
; clear06 clears the outermost box (see diagram).
; There are 7 copy routines that copy certain pixels from the source
; image in mainmem to the destination image in auxmem, labeled copy00..copy06.
;
; row|             pixels
; ---+.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
; 00 |66666666666666666666666666666666
; 01 |66666666666666666666666666666666
; 02 |66555555555555555555555555555566
; 03 |66555555555555555555555555555566
; 04 |66554444444444444444444444445566
; 05 |66554444444444444444444444445566
; 06 |66554433333333333333333333445566
; 07 |66554433333333333333333333445566
; 08 |66554433222222222222222233445566
; 09 |66554433222222222222222233445566
; 10 |66554433221111111111112233445566
; 11 |66554433221111111111112233445566
; 12 |66554433221100000000112233445566
; 13 |66554433221111111111112233445566
; 14 |66554433221111111111112233445566
; 15 |66554433222222222222222233445566
; 16 |66554433222222222222222233445566
; 17 |66554433333333333333333333445566
; 18 |66554433333333333333333333445566
; 19 |66554444444444444444444444445566
; 20 |66554444444444444444444444445566
; 21 |66555555555555555555555555555566
; 22 |66555555555555555555555555555566
; 23 |66666666666666666666666666666666
; 24 |66666666666666666666666666666666
;
; Each routine manipulates pixels in horizontal pairs, meaning we can copy
; bytes without having to worry about masking high and low nibbles.
; Each routine except copy00 is similar, defined by 4 parameters:
; - top row (absolute row, i.e. 00..C7)
; - bottom row (should probably use the first of the two, also absolute)
; - left (should probably be in bytes, also absolute)
; - right (should probably be in bytes, also absolute)
;
; On [top row] and [top row + 1], copy bytes from [left offset] to [right offset]
; While [current row] < [bottom row], draw 1 byte at [left offset] and 1 byte at [right offset]
; On [bottom row] and [bottom row + 1], copy bytes from [left offset] to [right offset]

shrlo     = $201                     ; [$C8 bytes]
shrhi     = $301                     ; [$C8 bytes]

         !source "src/fx/macros.a"
         !source "src/fx/fx.shr.common.a"

         ldx   #0
-        ldy   start, x
         sty   $00, x
         sta   EndStagesHi, x
         inx
         bne   -

         stx   seta+1
         stx   sub1+1
         ldx   #-25
         stx   sub2+1
---      ldx   #8
seta     lda   #0
--       pha
         ldy   #10-1
-        sta   (<src), y
         sec
sub1     sbc   #0
         dey
         bpl   -
         clc
         lda   <src
         adc   #10
         sta   <src
         pla
         sec
sub2     sbc   #-25
         dex
         bne   --
         lda   #$90
         sta   seta+1
         lda   #$10
         sta   sub1+1
         stx   sub2+1
         bcc   ---

         +BUILD_SHR_LOOKUP_TABLES shrlo, shrhi
         +COPY_SCB_AND_PALETTES
         ;WRITEAUXMEM active

         jmp   MainLoop

start
!pseudopc 0 {
MainLoop ldx   #80
BoxLoop  ldy   <BoxStages-1, x       ; for each box, get its current stage
         inc   <BoxStages-1, x       ; increment every box's stage every time through the loop
         lda   StagesHi, y
         beq   NextBox               ; if stage's drawing routine is 0, nothing to do
         sta   <j+2
         lda   BoxesX-1, x           ; A = starting SHR row for this box
         ldy   BoxesY-1, x           ; Y = starting byte offset for this box
         clc
         stx   <ReBox+1
j        jsr   $0000                 ; [SMC] call drawing routine for this stage
ReBox    ldx   #$00                  ; [SMC]
NextBox  dex
         bne   <BoxLoop
         lda   <j+2
         beq   <exit                 ; if we didn't draw anything in any box, we're done
         stx   <j+2                  ; X=0 here
         bit   $C000
         bpl   MainLoop
exit     sta   WRITEMAINMEM
setV     rts

src      !word BoxesX
rowcount !byte 0
lefty    !byte 0
righty   !byte 0

; diagonal - VERY GOOD
BoxStages
         !byte $F9,$F8,$F7,$F6,$F5,$F4,$F3,$F2,$F1,$F0
         !byte $FA,$F9,$F8,$F7,$F6,$F5,$F4,$F3,$F2,$F1
         !byte $FB,$FA,$F9,$F8,$F7,$F6,$F5,$F4,$F3,$F2
         !byte $FC,$FB,$FA,$F9,$F8,$F7,$F6,$F5,$F4,$F3
         !byte $FD,$FC,$FB,$FA,$F9,$F8,$F7,$F6,$F5,$F4
         !byte $FE,$FD,$FC,$FB,$FA,$F9,$F8,$F7,$F6,$F5
         !byte $FF,$FE,$FD,$FC,$FB,$FA,$F9,$F8,$F7,$F6
         !byte $00,$FF,$FE,$FD,$FC,$FB,$FA,$F9,$F8,$F7

; diagonal
;BoxStages
;         !byte $F2,$F0,$EE,$EC,$EA,$E8,$E6,$E4,$E2,$E0
;         !byte $F4,$F2,$F0,$EE,$EC,$EA,$E8,$E6,$E4,$E2
;         !byte $F6,$F4,$F2,$F0,$EE,$EC,$EA,$E8,$E6,$E4
;         !byte $F8,$F6,$F4,$F2,$F0,$EE,$EC,$EA,$E8,$E6
;         !byte $FA,$F8,$F6,$F4,$F2,$F0,$EE,$EC,$EA,$E8
;         !byte $FC,$FA,$F8,$F6,$F4,$F2,$F0,$EE,$EC,$EA
;         !byte $FE,$FC,$FA,$F8,$F6,$F4,$F2,$F0,$EE,$EC
;         !byte $00,$FE,$FC,$FA,$F8,$F6,$F4,$F2,$F0,$EE

; spiral
;BoxStages
;         !byte $E9,$E8,$E7,$E6,$E5,$E4,$E3,$E2,$E1,$00
;         !byte $EA,$CF,$CE,$CD,$CC,$CB,$CA,$C9,$E0,$FF
;         !byte $EB,$D0,$BD,$BC,$BB,$BA,$B9,$C8,$DF,$FE
;         !byte $EC,$D1,$BE,$B3,$B2,$B1,$B8,$C7,$DE,$FD
;         !byte $ED,$D2,$BF,$B4,$B5,$B6,$B7,$C6,$DD,$FC
;         !byte $EE,$D3,$C0,$C1,$C2,$C3,$C4,$C5,$DC,$FB
;         !byte $EF,$D4,$D5,$D6,$D7,$D8,$D9,$DA,$DB,$FA
;         !byte $F0,$F1,$F2,$F3,$F4,$F5,$F6,$F7,$F8,$F9

; snake
;BoxStages
;         !byte $00,$FF,$FE,$FD,$FC,$FB,$FA,$F9,$F8,$F7
;         !byte $ED,$EE,$EF,$F0,$F1,$F2,$F3,$F4,$F5,$F6
;         !byte $EC,$EB,$EA,$E9,$E8,$E7,$E6,$E5,$E4,$E3
;         !byte $D9,$DA,$DB,$DC,$DD,$DE,$DF,$E0,$E1,$E2
;         !byte $D8,$D7,$D6,$D5,$D4,$D3,$D2,$D1,$D0,$CF
;         !byte $C5,$C6,$C7,$C8,$C9,$CA,$CB,$CC,$CD,$CE
;         !byte $C4,$C3,$C2,$C1,$C0,$BF,$BE,$BD,$BC,$BB
;         !byte $B1,$B2,$B3,$B4,$B5,$B6,$B7,$B8,$B9,$BA

; snake 2
;BoxStages
;         !byte $00,$00,$FF,$FF,$FE,$FE,$FD,$FD,$FC,$FC
;         !byte $F7,$F7,$F8,$F8,$F9,$F9,$FA,$FA,$FB,$FB
;         !byte $F6,$F6,$F5,$F5,$F4,$F4,$F3,$F3,$F2,$F2
;         !byte $ED,$ED,$EE,$EE,$EF,$EF,$F0,$F0,$F1,$F1
;         !byte $EC,$EC,$EB,$EB,$EA,$EA,$E9,$E9,$E8,$E8
;         !byte $E3,$E3,$E4,$E4,$E5,$E5,$E6,$E6,$E7,$E7
;         !byte $E2,$E2,$E1,$E1,$E0,$E0,$DF,$DF,$DE,$DE
;         !byte $D9,$D9,$DA,$DA,$DB,$DB,$DC,$DC,$DD,$DD

; l2r alternating - VERY GOOD
;BoxStages
;         !byte $00,$FE,$FC,$FA,$F8,$F6,$F4,$F2,$F0,$EE
;         !byte $ED,$EF,$F1,$F3,$F5,$F7,$F9,$FB,$FD,$FF
;         !byte $00,$FE,$FC,$FA,$F8,$F6,$F4,$F2,$F0,$EE
;         !byte $ED,$EF,$F1,$F3,$F5,$F7,$F9,$FB,$FD,$FF
;         !byte $00,$FE,$FC,$FA,$F8,$F6,$F4,$F2,$F0,$EE
;         !byte $ED,$EF,$F1,$F3,$F5,$F7,$F9,$FB,$FD,$FF
;         !byte $00,$FE,$FC,$FA,$F8,$F6,$F4,$F2,$F0,$EE
;         !byte $ED,$EF,$F1,$F3,$F5,$F7,$F9,$FB,$FD,$FF

; l2r alternating 2
;BoxStages
;         !byte $00,$FF,$FE,$FD,$FC,$FB,$FA,$F9,$F8,$F7
;         !byte $F7,$F8,$F9,$FA,$FB,$FC,$FD,$FE,$FF,$00
;         !byte $00,$FF,$FE,$FD,$FC,$FB,$FA,$F9,$F8,$F7
;         !byte $F7,$F8,$F9,$FA,$FB,$FC,$FD,$FE,$FF,$00
;         !byte $00,$FF,$FE,$FD,$FC,$FB,$FA,$F9,$F8,$F7
;         !byte $F7,$F8,$F9,$FA,$FB,$FC,$FD,$FE,$FF,$00
;         !byte $00,$FF,$FE,$FD,$FC,$FB,$FA,$F9,$F8,$F7
;         !byte $F7,$F8,$F9,$FA,$FB,$FC,$FD,$FE,$FF,$00

; u2d alternating
;BoxStages
;         !byte $00,$F1,$00,$F1,$00,$F1,$00,$F1,$00,$F1
;         !byte $FE,$F3,$FE,$F3,$FE,$F3,$FE,$F3,$FE,$F3
;         !byte $FC,$F5,$FC,$F5,$FC,$F5,$FC,$F5,$FC,$F5
;         !byte $FA,$F7,$FA,$F7,$FA,$F7,$FA,$F7,$FA,$F7
;         !byte $F8,$F9,$F8,$F9,$F8,$F9,$F8,$F9,$F8,$F9
;         !byte $F6,$FB,$F6,$FB,$F6,$FB,$F6,$FB,$F6,$FB
;         !byte $F4,$FD,$F4,$FD,$F4,$FD,$F4,$FD,$F4,$FD
;         !byte $F2,$FF,$F2,$FF,$F2,$FF,$F2,$FF,$F2,$FF
}

!macro INIT_DRAW .toprowoffset, .siderowcount, .leftoffset {
         adc   #.toprowoffset
         ldx   #.siderowcount
         stx   rowcount
         tax
         tya
         adc   #.leftoffset
         sta   lefty
}

!macro SET_ROW_X {
         lda   shrlo, x
         sta   <src
         lda   shrhi, x
         sta   <src+1
         ldy   lefty
}

!macro COPY_BYTE {
         lda   (src), y
         sta   (src), y
}

!macro COPY_BYTE_AND_INY {
         +COPY_BYTE
         iny
}

!macro SIDE_ROWS {
@siderows
         sty   righty
         +SET_ROW_X
         +COPY_BYTE
         ldy   righty
         +COPY_BYTE
         inx
         dec   rowcount
         bne   @siderows
}

!align $FF,0,0                       ; align to page
copy00
         +INIT_DRAW 12, 0, 6
         +SET_ROW_X
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE
         rts

BoxesX ; starting row for each box
;         !byte 0,0,0,0,0,0,0,0,0,0
;         !byte 25,25,25,25,25,25,25,25,25,25
;         !byte 50,50,50,50,50,50,50,50,50,50
;         !byte 75,75,75,75,75,75,75,75,75,75
;         !byte 100,100,100,100,100,100,100,100,100,100
;         !byte 125,125,125,125,125,125,125,125,125,125
;         !byte 150,150,150,150,150,150,150,150,150,150
;         !byte 175,175,175,175,175,175,175,175,175,175
BoxesY = BoxesX + 10*8 ; starting byte offset for each box
;         !byte $00,$10,$20,$30,$40,$50,$60,$70,$80,$90
;         !byte $00,$10,$20,$30,$40,$50,$60,$70,$80,$90
;         !byte $00,$10,$20,$30,$40,$50,$60,$70,$80,$90
;         !byte $00,$10,$20,$30,$40,$50,$60,$70,$80,$90
;         !byte $00,$10,$20,$30,$40,$50,$60,$70,$80,$90
;         !byte $00,$10,$20,$30,$40,$50,$60,$70,$80,$90
;         !byte $00,$10,$20,$30,$40,$50,$60,$70,$80,$90
;         !byte $00,$10,$20,$30,$40,$50,$60,$70,$80,$90
!if (>BoxesY != >BoxesX) {
  !error "Boxes array crosses a page"
}

!align $FF,0,0                       ; align to page
copy01
         +INIT_DRAW 10, 1, 5
         bit   <setV
--       clc
         !byte $A9
-        sec
         +SET_ROW_X
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE
         inx
         bcc   -
         bvc   +
         +SIDE_ROWS
         clv
         jmp   --
+        rts

!align $FF,0,0                       ; align to page
copy02
         +INIT_DRAW 8, 5, 4
         bit   <setV
--       clc
         !byte $A9
-        sec
         +SET_ROW_X
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE
         inx
         bcc   -
         bvc   +
         +SIDE_ROWS
         clv
         jmp   --
+        rts

!align $FF,0,0                       ; align to page
copy03
         +INIT_DRAW 6, 9, 3
         bit   <setV
--       clc
         !byte $A9
-        sec
         +SET_ROW_X
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE
         inx
         bcc   -
         bvc   +
         +SIDE_ROWS
         clv
         jmp   --
+        rts

!align $FF,0,0                       ; align to page
copy04
         +INIT_DRAW 4, 13, 2
         bit   <setV
--       clc
         !byte $A9
-        sec
         +SET_ROW_X
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE
         inx
         bcc   -
         bvc   +
         +SIDE_ROWS
         clv
         jmp   --
+        rts

!align $FF,0,0                       ; align to page
copy05
         +INIT_DRAW 2, 17, 1
         bit   <setV
--       clc
         !byte $A9
-        sec
         +SET_ROW_X
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE
         inx
         bcc   -
         bvc   +
         +SIDE_ROWS
         clv
         jmp   --
+        rts

!align $FF,0,0                       ; align to page
copy06
         +INIT_DRAW 0, 21, 0
         bit   <setV
--       clc
         !byte $A9
-        sec
         +SET_ROW_X
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE_AND_INY
         +COPY_BYTE
         inx
         bcc   -
         bvc   +
         +SIDE_ROWS
         clv
         jmp   --
+        rts

StagesHi ; high bytes of address of drawing routine for each stage
         !byte >copy00
         !byte >copy01
         !byte >copy02
         !byte >copy03
         !byte >copy04
         !byte >copy05
         !byte >copy06
EndStagesHi