; lenser -- FLI slideshow viewer
;
; Steps through NIMAGES FLI pictures named "00".."NN", each a PRG that KERNAL-
; loads to $4000 with the layout from fli.s --
;   $4000+L*$400  screen RAM for line L (L=0..7), 1000 bytes each
;   $6000         bitmap 8000   (offset $2000 in VIC bank 1)
;   $8000         colour RAM 1000  (copied to $D800)
;   $83E8         background 1
; The cycle-timed raster loop re-points $D018/$D011 every line for per-line
; colour; at the bottom border it chains to the KERNAL IRQ ($ea31) so GETIN and
; the jiffy clock keep working, letting wait.i advance on key / seconds / both.
; All slides are FLI (uniform).  NTSC=1 adds one NOP for the 65-cycle line.
;
; assembled by viewer/assemble.py via xa; NIMAGES / LOOPFLAG / WAITMODE / NTSC
; etc. are #defined by the generated wrapper.

        ; BASIC autostart, SYS 2061
        * = $0801
        .word basicend
        .word 10
        .byte $9e
        .byte "2061"
        .byte 0
basicend:
        .word 0

start:
        lda #$00
        sta $9d                   ; suppress KERNAL LOAD messages
        sta ss_idx
        jsr build_tables          ; per-line $D018/$D011 tables (once)

mainloop:
        jsr ss_name_build
        lda #$0b
        sta $d011                 ; blank while loading
        jsr ss_load               ; LOAD "NN",8,1 -> $4000 (KERNAL IRQ active)

        ; ---- FLI setup ----
        sei
        lda #$ff
        sta $cc                   ; cursor off (so blink can't corrupt $D800)

        ; copy colour RAM $8000 -> $D800 (1024 bytes)
        ldx #0
ccopy:
        lda $8000,x
        sta $d800,x
        lda $8100,x
        sta $d900,x
        lda $8200,x
        sta $da00,x
        lda $8300,x
        sta $db00,x
        inx
        bne ccopy

        lda $dd00
        and #$fc
        ora #$02
        sta $dd00                 ; VIC bank 1 ($4000-$7FFF)
        lda $83e8
        sta $d021                 ; background
        lda #$00
        sta $d020                 ; border black
        lda #$d8
        sta $d016                 ; multicolor on

        lda #<irq1
        sta $0314
        lda #>irq1
        sta $0315
        lda #$7f
        sta $dc0d                 ; disable CIA timer IRQs
        sta $dd0d
        lda $dc0d
        lda $dd0d
        lda #$01
        sta $d01a                 ; enable raster IRQ
        lda #$30
        sta $d012                 ; line 48
        lda $d011
        and #$7f
        sta $d011
        asl $d019
        cli

#include "wait.i"

        ; ---- stop the engine (KERNAL IRQ back on for the next LOAD) ----
        sei
        lda #$00
        sta $d01a
        lda #$81
        sta $dc0d
        lda #$31
        sta $0314
        lda #$ea
        sta $0315
        lda $dd00
        ora #$03
        sta $dd00                 ; bank 0
        asl $d019
        cli

        ; ---- advance ----
        inc ss_idx
        lda ss_idx
        cmp #NIMAGES
        bcc ssgo
#if LOOPFLAG == 1
        lda #$00
        sta ss_idx
ssgo:
        jmp mainloop
#else
        jmp ssend
ssgo:
        jmp mainloop
ssend:
#endif

        ; ---- final restore to BASIC ----
        lda #$1b
        sta $d011
        lda #$c8
        sta $d016
        lda #$15
        sta $d018
        lda #$0e
        sta $d020
        lda #$06
        sta $d021
        lda #$00
        sta $cc
        jsr $e544
        rts

; build d018tab = ((line AND 7) << 4) OR $08, d011tab = $38 OR ((line+3) AND 7)
build_tables:
        ldx #0
btab:
        txa
        and #$07
        asl
        asl
        asl
        asl
        ora #$08
        sta d018tab,x
        txa
        clc
        adc #$03
        and #$07
        ora #$38
        sta d011tab,x
        inx
        bne btab
        rts

; first IRQ, arrives with jitter on line 48, sets up the stabilised one
irq1:
        lda #<irq2
        sta $0314
        lda #>irq2
        sta $0315
        inc $d012
        asl $d019
        tsx
        cli
        .dsb 40,$ea               ; 40 NOPs -- irq2 fires inside this slide

; stabilised IRQ on line 49, runs the FLI loop then chains to the KERNAL IRQ
irq2:
        txs
        lda $d012
        cmp $d012
        beq jl
jl:
        ldx #$0d
d0:     dex
        bne d0
        nop
        nop
#if NTSC == 1
        nop                       ; NTSC extra 2 cycles for the 65-cycle line
#endif

        ldx #$00
fliloop:
        lda d011tab,x
        sta $d011
        lda d018tab,x
        sta $d018
        inx
        cpx #200
        bne fliloop

        ; bottom border -- re-arm irq1, then KERNAL housekeeping (keys + jiffy)
        lda #<irq1
        sta $0314
        lda #>irq1
        sta $0315
        lda #$30
        sta $d012
        asl $d019
        jmp $ea31                 ; KERNAL housekeeping (keys + jiffy) then RTI

ss_load:
        lda #2
        ldx #<ss_name
        ldy #>ss_name
        jsr $ffbd                 ; SETNAM
        lda #1
        ldx #8
        ldy #1
        jsr $ffba                 ; SETLFS (secondary 1 = file's own address)
        lda #0
        jsr $ffd5                 ; LOAD
        rts

ss_name_build:
        lda ss_idx
        ldx #$2f
        sec
ssten:
        inx
        sbc #10
        bcs ssten
        adc #10
        ora #$30
        sta ss_name+1
        txa
        sta ss_name
        rts

ss_idx:  .byte 0
ss_name: .byte $30,$30

; The cycle-exact fliloop reads `lda d018tab,x` / `lda d011tab,x` for x=0..199,
; so each table MUST be page-aligned -- otherwise indices past the page boundary
; add a page-cross penalty cycle and tear the FLI display.
        * = (* + $ff) & $ff00
d018tab:
        .dsb 256,0
d011tab:
        .dsb 256,0