;=======================================
;
; MSU-1 Enhanced Audio Patch
; ZeLDA no Densetsu - Kamigami no Triforce
; Modified for VT Randomizer
; 
; Author: qwertymodo
;
; Modified for use with Enemizer
;=======================================

track_list:
    DB $00,$01,$03,$03,$03,$03,$03,$03
    DB $01,$03,$01,$03,$03,$03,$03,$03
    DB $03,$03,$03,$01,$03,$03,$03,$03
    DB $03,$03,$03,$03,$03,$01,$03,$03
    DB $03,$01,$01

msu_main:
    LDA $4210
    LDA !REG_MSU_ID_01
    CMP !VAL_MSU_ID_01
    BEQ .continue
.nomsu
    SEP #$30
    JML spc_continue
.continue
    LDA !REG_MSU_ID_23
    CMP !VAL_MSU_ID_23
    BNE .nomsu
    LDA !REG_MSU_ID_45
    CMP !VAL_MSU_ID_45
    BNE .nomsu
    SEP #$30
    LDX !REG_MUSIC_CONTROL
    BNE command_ff
    
do_fade:
    LDA !REG_CURRENT_VOLUME
    CMP !REG_TARGET_VOLUME
    BNE .continue
    JML spc_continue
.continue
    BCC .increment
.decrement
    SBC !VAL_VOLUME_DECREMENT
    BCS .set
.mute
    STZ !REG_CURRENT_VOLUME
    STZ !REG_MSU_CONTROL
    STZ !REG_CURRENT_MSU_TRACK
    BRA .set
.increment
    ADC !VAL_VOLUME_INCREMENT
    BCC .set
    LDA !VAL_VOLUME_FULL
.set
    STA !REG_CURRENT_VOLUME
    STA !REG_MSU_VOLUME
    JML spc_continue

command_ff:
    CPX !VAL_COMMAND_LOAD_NEW_BANK
    BNE command_f3
    JML spc_continue

command_f3:
    CPX !VAL_COMMAND_FULL_VOLUME
    BNE command_f2
    STX !REG_SPC_CONTROL
    LDA !VAL_VOLUME_FULL
    STA !REG_TARGET_VOLUME
    JML spc_continue

command_f2:
    CPX !VAL_COMMAND_FADE_HALF
    BNE command_f1
    STX !REG_SPC_CONTROL
    LDA !VAL_VOLUME_HALF
    STA !REG_TARGET_VOLUME
    JML spc_continue

command_f1:
    CPX !VAL_COMMAND_FADE_OUT
    BNE load_track
    STX !REG_SPC_CONTROL
    STZ !REG_TARGET_VOLUME
    JML spc_continue

load_track:
    CPX !REG_CURRENT_MSU_TRACK
    BNE .continue
    CPX #$1B
    BEQ .continue
    JML spc_continue
.continue
    STX !REG_MSU_TRACK_LO
    STZ !REG_MSU_TRACK_HI
    STZ !REG_MSU_CONTROL
    LDA !VAL_VOLUME_FULL
    STA !REG_TARGET_VOLUME
    STA !REG_CURRENT_VOLUME
    STA !REG_MSU_VOLUME

msu_check_busy:
    LDA !REG_MSU_STATUS
    BIT !FLAG_MSU_STATUS_AUDIO_BUSY
    BNE msu_check_busy
    BIT !FLAG_MSU_STATUS_TRACK_MISSING
    BEQ msu_play

spc_fallback:
    STZ !REG_MSU_CONTROL
    STZ !REG_CURRENT_MSU_TRACK
    STZ !REG_TARGET_VOLUME
    STZ !REG_CURRENT_VOLUME
    STZ !REG_MSU_VOLUME
    JML spc_continue

msu_play:
    LDA track_list,x
    STA !REG_MSU_CONTROL
    STX !REG_CURRENT_MSU_TRACK
    JML spc_continue