dc.l $0, start
	dc.l empty_handler
	dc.l empty_handler
	;$10
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$20
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$30
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$40
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$50
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$60
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$70
	dc.l int_4
	dc.l empty_handler
	dc.l int_6
	dc.l empty_handler
	;$80
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$90
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$A0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$B0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$C0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$D0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$E0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$F0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.b "SEGA GENESIS    "
	dc.b "(c) 2015.JULY   "
	dc.b "Menu            "
	dc.b "                "
	dc.b "                "
	dc.b "Menu            "
	dc.b "                "
	dc.b "                "
	dc.b "MP BlstMenu-00", 0, 0
	dc.b "                "
	dc.l $0, rom_end-1, $FF0000, $FFFFFF
	dc.b "                "
	dc.b "                "
	dc.b "                "
	dc.b "                "
	dc.b "JUE "

;register addresses
VDP_DATA  equ $C00000
VDP_CTRL  equ $C00004
VDP_HV    equ $C00008
Z80_RAM   equ $A00000
IO_AREA   equ $A10000
PAD1_DATA equ (IO_AREA + 3)
PAD2_DATA equ (IO_AREA + 5)
EXT_DATA  equ (IO_AREA + 7)
PAD1_CTRL equ (IO_AREA + 9)
PAD2_CTRL equ (IO_AREA + 11)
EXT_CTRL  equ (IO_AREA + 13)

MODE_1   equ 0
MODE_2   equ 1
SCROLL_A equ 2
WINDOW   equ 3
SCROLL_B equ 4
SAT      equ 5
BG_COLOR equ 7
HINT     equ $A
MODE_3   equ $B
MODE_4   equ $C
HSCROLL  equ $D
AUTOINC  equ $F
SCROLL   EQU $10
WINDOW_H equ $11
WINDOW_V equ $12
DMALEN_L equ $13
DMALEN_H equ $14
DMASRC_L equ $15
DMASRC_M equ $16
DMASRC_H equ $17

VDP_VRAM_WRITE equ $40000000
VDP_CRAM_WRITE equ $C0000000
VDP_VSRAM_WRITE equ $40000010
VDP_DMA_FLAG equ $80

vdpregset macro
	move.w #(((\1) << 8) | $8000 | (\2)), (a1)
	endm

vdpreg macro
	dc.w (((\1) << 8) | $8000 | (\2))
	endm

;Writes a normal VDP command to the control port
;\1 - VDP address
;\2 - Access type
vdpaccess macro
	move.l #((\2) | (\1) << 16 & $3FFF0000 | (\1) >> 14 & 3), (a1)
	endm

;Writes a DMA command to the control port
;\1 - Destination address
;\2 - Destination type
startdma macro
	move.l #(\2 | VDP_DMA_FLAG | (\1 << 16) & $3FFF0000 | (\1 >> 14) & 3), (a1)
	endm

DMA_SRC_68K  equ 0
DMA_SRC_VRAM equ $C0
DMA_SRC_FILL equ $80

dmasrc macro
	move.l #($95009600 + (\1) << 15 & $FF0000 + (\1) >> 9 & $FF), (a1)
	move.w #($9700 + (\1) >> 17 & $7F | (\2)), (a1)
	endm

dir_buffer equ $100000
menu_port  equ $180000

MAX_DISPLAY equ 24

	rsset $FFFF8000
x_pos         rs.w 1
base_cmd      rs.l 1
sprite_list   rs.l 160
page_index    rs.l MAX_DISPLAY+1
page_stack    rs.l 1
page_pointers rs.l 1024
mouse_sprite  rs.l 1
mouse_x       rs.w 1
num_sprites   rs.b 1
last_pad1     rs.b 1
last_pad2     rs.b 1
selected      rs.b 1
more_pages    rs.b 1
mouse_buf     rs.b 3
mouse_shown   rs.b 1
last_mbuttons rs.b 1


int_6:
	dmasrc sprite_list, DMA_SRC_68K
	;set DMA length
	move.l #$94009300, d0
	moveq #0, d1
	move.b num_sprites.w, d1
	add.w d1, d1
	add.w d1, d1
	move.b d1, d0
	swap d0
	lsr.w #8, d1
	move.b d1, d0
	move.l d0, (a1)
	startdma $C000, VDP_VRAM_WRITE

	;read gamepad/mouse in port 1
	lea PAD1_DATA, a2

	bsr io_read

	cmp.b #3, d2
	beq .mouse

	move.b last_pad1.w, d1
	eor.b d0, d1
	and.b d0, d1
	move.b d0, last_pad1.w

	bsr handle_pad_buttons

	bra pad2
.mouse
	bsr handle_mouse

pad2:
	;read gamepad/mouse in port 2
	lea PAD2_DATA, a2

	bsr io_read

	cmp.b #3, d2
	beq .mouse

	move.b last_pad2.w, d1
	eor.b d0, d1
	and.b d0, d1
	move.b d0, last_pad2.w

	bsr handle_pad_buttons
	rte
.mouse
	bsr handle_mouse
	rte


;d0 = SACBRLUD
;d1 = newly pressed buttons
handle_pad_buttons:
	moveq #16, d2
	btst #1, d1
	bne down
	btst #0, d1
	bne up
	btst #3, d1
	bne right
	btst #2, d1
	bne left
	btst #7, d1
	bne select_entry
	btst #5, d1
	bne select_entry
handle_done:
	rts

down:
	;check if we are already at the bottom of the page
	moveq #1, d0
	add.b (selected).w, d0
	move.w d0, d1
	add.w d0, d0
	add.w d0, d0
	lea page_index.w, a2
	tst.l (0, a2, d0.w)
	beq handle_done
	move.b d1, (selected).w

	add.w d2, (sprite_list).w
	add.w d2, (sprite_list+8).w
	rts
up:
	;check if we are already at the top of the page
	move.b (selected).w, d0
	beq handle_done
	subq #1, d0
	move.b d0, (selected).w

	sub.w d2, (sprite_list).w
	sub.w d2, (sprite_list+8).w
	rts

right:
	;check that we have another page to go to
	tst.b more_pages.w
	beq handle_done
	;switch to the next page
	move.l page_stack.w, a6
	move.l (-4, a6), a6

	addq #6, a7
	bra render_page

left:
	move.l page_stack.w, a5
	;check if we're already on the first page
	cmp.l #(page_pointers+8), a5
	beq handle_done
	;switch to previous page
	lea (-12, a5), a5
	move.l (a5)+, a6
	move.l a5, page_stack.w

	addq #6, a7
	bra render_page

select_entry:
	moveq #0, d0
	move.b (selected).w, d0
	add.w d0, d0
	add.w d0, d0
	lea page_index.w, a2
	move.l (0, a2, d0.w), a2
	tst.b (-1, a2)
	bne enter_dir
	;regular file
	lea menu_port+8, a3
	move.l a2, (a3)
	rts
enter_dir:
	lea menu_port+4, a3
	move.l a2, (a3)
.wait_complete
	tst.w (a3)
	bne .wait_complete
	addq #6, a7
	bra menu_start

handle_mouse:
	move.b last_mbuttons.w, d4
	eor.b d3, d4
	and.b d3, d4
	move.b d3, last_mbuttons.w

	move.b d0, d2
	or.b d1, d2
	beq .no_mouse_move


	tst.b mouse_shown.w
	bne .skip_show_check

	moveq #0, d2
	move.b num_sprites.w, d2
	move.w d2, d4
	lsl.w #3, d4
	lea sprite_list.w, a2
	move.b d2, (-5, a2, d4.w)
	lea (0, a2, d4.w), a2
	move.l a2, mouse_sprite.w
	move.l #$01000500, (a2)+
	move.w #$8083, (a2)
	move.w #$100, mouse_x.w
	addq #1, d2
	move.b d2, num_sprites.w

	move.b #1, mouse_shown.w

.skip_show_check
	neg.w d1
	move.l mouse_sprite.w, a2
	add.w d1, (a2)
	add.w d0, mouse_x.w
	move.w mouse_x.w, d0
	asr.w #1, d0
	move.w d0, (6, a2)
	move.w (a2), d1
	cmp.w #272, d1
	blo .done
	cmp.w #655, d1
	bhi .done
	and.w #$FFF0, d1
	subq #8, d1
	move.w d1, (sprite_list).w
	move.w d1, (sprite_list+8).w

	sub.w #264, d1
	lsr.w #4, d1
	move.b d1, selected.w
.no_mouse_move
	btst #0, d4
	bne select_entry
.done
	rts
int_4:
empty_handler:
	rte

id_lookup:
	dc.b $0, $1, $4, $5
	dc.b $2, $3, $6, $7
	dc.b $8, $9, $C, $D
	dc.b $A, $B, $E, $F

io_read:
	;read TH=1
	move.b (a2), d0
	;read TH=0
	move.b #0, (a2)
	nop
	nop
	move.b (a2), d1
	;reset TH to 1
	move.b #$40, (a2)

	moveq #0, d2   ;4

	;calculate Mega Drive peripheral ID
	move.b d1, d2  ;4
	lsr.b #1, d2   ;8, 12
	or.b d1, d2    ;4, 16
	and.b #5, d2   ;8, 24

	move.b d0, d3  ;4
	add.b d3, d3   ;4, 8
	or.b d0, d3    ;4, 12
	and.b #$A, d3  ;8, 20

	or.b d3, d2    ;4
	move.b (id_lookup, pc, d2.w), d2 ;14


	cmp.b #$3, d2
	beq .mouse

	cmp.b #$D, d2
	bne .not_pad

	and.b #$3F, d0
	and.b #$30, d1
	add.b d1, d1
	add.b d1, d1
	or.b d1, d0
	not.b d0
	rts
.not_pad:
	moveq #0, d0
	rts

.mouse:

	move.b #$60, (a2)
	move.b #$60, (PAD1_CTRL-PAD1_DATA, a2)
	move.b #$60, (a2)

	moveq #$f, d4
wait_hi_init:
	btst #4, (a2)
	beq wait_hi_init
	nop
	nop
	move.b #$20, (a2)
	nop
	nop
	moveq #$f, d4
	move.b #0, (a2)
.wait_lo
	btst #4, (a2)
	bne .wait_lo
	moveq #$f, d4
	move.b #$20, (a2)
.wait_hi
	btst #4, (a2)
	beq .wait_hi

	lea mouse_buf.w, a3
	move.l a3, a4
	moveq #2, d3
	moveq #0, d0
loop:
	moveq #$f, d4
	move.b #0, (a2)
.wait_lo
	btst #4, (a2)
	bne .wait_lo
	move.b (a2), d0
	lsl.b #4, d0
	moveq #$f, d4
	move.b #$20, (a2)
.wait_hi
	btst #4, (a2)
	beq .wait_hi
	move.b (a2), d1
	and.b #$f, d1
	or.b d1, d0
	move.b d0, (a3)+

	dbra d3, loop

	;end request
	move.b #$60, (a2)


	;massage data
	moveq #0, d1
	move.b d0, d1
	move.b (a4)+, d3
	move.b (a4), d0

	btst #4, d3
	beq xpos
	or.w #$FF00, d0
xpos
	btst #5, d3
	beq ypos
	or.w #$FF00, d1
ypos
	;set port config back to normal controller mode
	move.b #$40, (PAD1_CTRL-PAD1_DATA, a2)
	rts

topcorner equ (button-font)/64 + 32
topmiddle equ topcorner+1
botcorner equ topmiddle+1
botmiddle equ botcorner+1
horiz_flip equ $800
vert_flip equ $1000

; draws a button
; d0.w - x in cells
; d1.w - y in cells
; d2.w - width in cells
;
; clobbers a6
draw_button:
	;multiply x by 2
	add.w d0, d0
	;multiply y by 128
	lsl.w #7, d1
	add.w d1, d0
	add.w #$A000, d0
	move.w d0, d1
	and.w #$3FFF, d0
	rol.w #2, d1
	and.w #3, d1
	ori.w #(VDP_VRAM_WRITE >> 16), d0
	swap d0
	move.w d1, d0
	move.l d0, (a1)
	move.w d2, d1
	;top left corner
	move.w #topcorner, (a0)
	subq #3, d1
	bmi .notopmiddle
.toploop:
	;top middle
	move.w #topmiddle, (a0)
	dbra d1, .toploop
.notopmiddle
	;top right corner
	move.w #(topcorner | horiz_flip), (a0)
	;go to next row in name table
	add.l #((2*64) << 16), d0
	move.l d0, (a1)
	;bottom left corner
	move.w #botcorner, (a0)
	subq #3, d2
	bmi .nomiddlebot
.botloop:
	;bottom middle
	move.w #botmiddle, (a0)
	dbra d2, .botloop
.nomiddlebot
	;bottom right corner
	move.w #(botcorner | horiz_flip), (a0)
	rts

;a5 - menu pointer
;d6 - initial Y position of menu
draw_menu:
	moveq #0, d7
	;save menu pointer for second pass
	movea.l a5, a4
.lenloop	
	tst.b (a5)
	beq .lendone
	movea.l a5, a6
	bsr strlen
	cmp.w d7, d0
	blo .nochange
	move.w d0, d7
.nochange
	lea (1, a5, d0.w), a5
	bra .lenloop
.lendone
	
	addq #2, d7
	
	;calculate X position
	move.w d7, d4
	lsr.w #1, d4
	moveq #20, d5
	sub.w d4, d5
	;restore menu pointer
	movea.l a4, a5
.drawloop
	tst.b (a5)
	beq .done
	;x pos
	move.w d5, d0
	;y pos
	move.w d6, d1
	;width
	move.w d7, d2
	bsr draw_button
	addq #4, d6
	
	movea.l a5, a6
	bsr strlen
	movea.l a5, a6
	lea (1, a5, d0.w), a5
	;TODO: draw string
	bra .drawloop
.done
	rts

initial_regs:
	vdpreg MODE_2, $4    ;Mode 5, everything turned off
	vdpreg MODE_1, $4
	vdpreg SCROLL_A, $20 ;Scroll a table $8000
	vdpreg SCROLL_B, $05 ;Scroll b table $A000
	vdpreg SAT, $60      ;SAT table $C000
	vdpreg BG_COLOR, 0
	vdpreg HINT, $FF
	vdpreg MODE_3, 0     ;full screen scroll
	vdpreg MODE_4, $87   ;40 cell mode, double-res interlace
	vdpreg HSCROLL, 0
	vdpreg AUTOINC, 2
	vdpreg SCROLL, 1     ;64x32 scroll size
end_initial_regs

start:
	lea $FF0000, a0
	moveq #0, d0
	move.w #($10000/8 - 1), d1
.clearloop:
	move.l d0, (a0)+
	move.l d0, (a0)+
	dbra d1, .clearloop

	lea $C00000, a0
	lea $C00004, a1

	moveq #(end_initial_regs-initial_regs-1), d0
	lea initial_regs.w, a2
.regloop
	move.w (a2)+, (a1)
	dbra d0, .regloop

	vdpaccess $0, VDP_CRAM_WRITE
	move.w #$020, (a0)
	move.w #$EEE, (a0)
	move.w #$222, (a0)

	;init scroll table
	vdpaccess $0, VDP_VRAM_WRITE
	move.w #0, (a0)
	move.w #4, (a0)

	;load tiles
	vdpaccess $800, VDP_VRAM_WRITE
	lea font(pc), a2
	move.w #((buttonend-font)/4 - 1), d0
tloop:
	move.l (a2)+, (a0)
	dbra d0, tloop
	move.w #((fontfixedend-fontfixed)/4 - 1), d0
dtloop:
	move.l (a2)+, d1
	move.l d1, (a0)
	move.l d1, (a0)
	dbra d0, dtloop


	;setup SAT
	;;vdpaccess $C000, VDP_VRAM_WRITE

	lea sprite_list.w, a2
	;left arrow
	move.l #$01080501, (a2)+
	move.l #$807F0086, (a2)+

	;right arrow
	move.l #$01080500, (a2)+
	move.l #$887F01AA, (a2)+
	move.b #2, num_sprites.w
	
	

menu_start:
	lea page_pointers.w, a5
	lea dir_buffer, a6
	move.l a6, (a5)+
	move.l a5, page_stack.w
	lea menu_port, a2
	move.l a6, (a2)

wait_complete:
	tst.w (a2)
	bne wait_complete

render_page:
	;clear name tables
	vdpaccess $8000, VDP_VRAM_WRITE
	moveq #32, d0
	swap d0
	move.b #32, d0
	move.w #(64*64-1), d1
ploop:
	move.l d0, (a0)
	dbra d1, ploop

	;moveq #0, d0
	;moveq #26, d1
	;moveq #6, d2
	;bsr draw_button

	move.l #$40860002, d3
	move.l d3, (a1)
	move.l d3, base_cmd.w
	
	moveq #4, d6
	lea main_menu(pc), a5
	bsr draw_menu
	bra gamepad_setup
	

	move.b #0, more_pages.w
	lea page_index.w, a3
	moveq #MAX_DISPLAY-1, d7
file_loop:
	tst.b (a6)+
	beq done_files
	addq #1, a6 ;TODO: Do something with directory flag

	;skip over entries starting with a dot except ..
	cmp.b #$2E, (a6)
	bne normal
	cmp.b #$2E, (1, a6)
	beq normal
	addq #1, a6
.skip_loop:
	tst.b (a6)+
	bne .skip_loop
	addq #1, d7
	move.l a6, d6
	bra skip
normal:
	;save entry pointer to page index
	move.l a6, (a3)+
	;print name on screen
	moveq #0, d0
	bsr print_string
	move.l a6, d6

	lea Newline(pc), a6
	bsr print_string

skip:
	;word align pointer
	addq #1, d6
	and.w #$FFFE, d6
	move.l d6, a6

	dbra d7, file_loop
	tst.b (a6)
	beq done_files
	move.b #1, more_pages.w
done_files:
	move.l page_stack.w, a5
	move.l a6, (a5)+
	move.l a5, page_stack.w

	;null terminate page_index
	moveq #0, d0
	move.l d0, (a3)

gamepad_setup:
	;setup gamepads
	move.b #$40, PAD1_CTRL
	move.b #$40, PAD2_CTRL

	move.w #$8174, (a1) ;enable display, vertical interrupts, DMA


wait_forever
	stop #2500
	bra wait_forever

Newline:
	dc.b $A, 0

	align 1

;Prints a null terminated string
;a6 - pointer to string
;a0 - VDP data port
;d0 - base tile attribute
;
;Clobbers: d1.w, d2.w, d3.l
print_string:
	lea widths(pc), a5
	move.w x_pos.w, d2
	move.l base_cmd.w, d3
.loop
	moveq #0, d1
	move.b (a6)+, d1
	beq .end
	cmp.b #$A, d1
	beq .newline
	tst.b (-32, a5, d1.w)
	beq .narrow
	add.w d0, d1
	move.w d1, (a0)
	addq #2, d2
	bra .loop
.narrow
	add.w d0, d1
	move.w d1, (a0)
	addq #1, d2
	move.l d2, d1
	;switch to other plane
	and.w #$FFFE, d1
	swap d1
	eor.l #$20000000, d3
	add.l d3, d1
	move.l d1, (a1)
	bra .loop
.newline
	moveq #0, d2
	;switch back to plane A
	and.l #$DFFFFFFF, d3
	;skip to next row
	add.l #$00800000, d3
	move.l d3, (a1)
	bra .loop
.end
	move.w d2, x_pos.w
	move.l d3, base_cmd.w
	rts
	
;Prints a null-terminated string with a fixed width font
;a6 - pointer to string
;a0 - VDP data port
;d0 - base tile attribute
;
print_string_fixed:
.loop
	moveq #0, d1
	move.b (a6)+, d1
	beq .end
	add.w d0, d1
	move.w d1, (a0)
	bra .loop
.end
	rts
	
;Returns string length in d0
;a6 - pointer to string
strlen:
	moveq #-1, d0
.loop
	addq #1, d0
	tst.b (a6)+
	bne .loop
	rts

	align 1
font:
	incbin font_interlace_variable.tiles
fontend
arrow:
	incbin arrow.tiles
arrowend:
cursor:
	incbin cursor.tiles
cursorend:
button:
	incbin button.tiles
buttonend:
fontfixed:
	incbin font.tiles
fontfixedend:

widths:
	dc.b 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 1
	dc.b 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0
	dc.b 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1
	dc.b 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
	dc.b 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1
	
main_menu:
	dc.b "Load ROM", 0
	dc.b "Exit", 0
	dc.b 0
	
pause_menu:
	dc.b "Resume", 0
	dc.b "Load ROM", 0
	dc.b "Save State", 0
	dc.b "Load State", 0
	dc.b 0

rom_end: