Condensing Spell List in Battle

I HAVE SOLVED IT! I think, anyway. The reason it didn't crash until you got Shadow was because the crash was caused by Interceptor counter-attacks. I didn't realise how the game handled them, and consequently missed a PLY because of it causing a stack mismatch. The new version of the code checks for Interceptor (attacks FDh and FEh) before it goes into the rest of the code and exits ahead of time, rather than searching for it in Shadow's spell list. (Or whoever has Interceptor status, really.)

I have also fixed, I believe, the 'Not enough MP' messages -- that was caused by checking for monster attackers out of order. I've adjusted the current code so that it does that check and THEN jumps away to the new code. It leaves more of the vanilla code intact, and we have to check again for Summon or Lore, but it also shortens the new code because we no longer need to check for Magic/X-Magic, as it's done before we jump away, and we no longer need to REP #$10 in the new code, as that's set before the jump as well.

Code:

hirom
;header

!freespace_C2_0 = $C2A65A        ; 82 bytes needed
!freespace_C2_1 = $C2FAB0        ; 86 bytes needed

org $C2256D                
JSR condenseSpellLists ; this was originally a JSR to modify available commands; we'll be JMPing to that
                            ; at the end of the modified code so that RTS comes back to the right spot

org $C24F2E
JMP calculateMPDeduction


                            
org !freespace_C2_0
print "New code CondenseSpellLists starts at: ",pc
reset bytes

condenseSpellLists:
PHX                ; This is our character ID coming in
PHP
LDY #$04        ; this is the index of the first Spell slot in the character's spell list
.noMoreSpells    ; we'll be branching back here to execute our Lore list
TYX                ; X is going to be our 'write-space' indexREP
REP #$10

    .checkLoreLoop
    LDA ($F2),Y
    INC
    BNE .checkNextLore

        .findNextLore
        INY #4
        CPY #$00DC    ; if we've hit the first Lore slot, there are no more spells to copy back
        BEQ .noMoreSpells    ; so jump out, reset X to start our lores
        CPY #$013C    ; this is after the last Lore slot, so if we've gone that far, there are no more spells to copy back
        BEQ .noMoreLores
        LDA ($F2),Y
        INC
        BEQ .findNextLore

    PHY            ; we'll be pushing and pulling within the loop, but we need to know
                ; where it started so we can blank out the slot we copied from
    CLC
    REP #$20
    
        .copyNextLore
        LDA ($F2),Y    ; Yes, we just did this, but we need to do it within this loop, too
        PHY            ; this stores our Y location, i.e. the next slot with a spell learned
        TXY
        STA ($F2),Y
        PLY            ; back to our 'write from' location
        INY    #2        ; and gets the next byte
        INX #2
        BCS .doneCopy
        SEC
        BPL .copyNextLore    ; if we haven't done four bytes, loop back and grab the next
        .doneCopy
        
    SEP #$20    
    PLY            ; this is the first byte of the slot we copied from
    TDC
    STA ($F4),Y    ; this zeroes out the MP cost
    DEC
    STA ($F2),Y    ; and blanks out the spell we copied from
        
    BRA .weCopiedALore
    .checkNextLore
    INX #4
    .weCopiedALore
    TXY                ; and then copy it over to Y for our next loop through
    CPY #$00D8        ; if this is the last spell slot
    BEQ .checkNextLore    ;loop back up and INX again so we skip over it and point at our first Lore slot
    CPY #$0138
    BNE .checkLoreLoop
    
.noMoreLores
PLP    
PLX
JMP $532C


print "CondenseSpellLists ends at: ",pc," and used ",bytes," bytes of space."



org !freespace_C2_1
calculateMPDeduction:

print "New code CalculateMPDeduction starts at: ",pc
reset bytes

LDA $3A7A            ; (get command #)
CMP #$19
BEQ .calculateSummon    ; (branch if it's Summon)
CMP #$0C
BEQ .calculateLore    ; (branch if it's Lore)

.calculateMagic
LDA $3A7B            ; (get attack #)
CMP #$FD
BCS fka_4F53
STA $F0                        ; save our spell ID in scratch memory
LDA #$04                    ; four bytes per index

.loreEntersHere
REP #$20
CLC
ADC $302C,X                 ; get the start of our character's magic list (index #0 is esper)
STA $F2                        ; this points out our first Magic slot
INC #3
STA $F4                        ; and this points at our first MP cost slot
SEP #$20
PHY
LDY $00

    .findSpell
    LDA ($F2),Y
    CMP $F0
    BEQ .getMPCost
    INY #4
    BRA .findSpell
    
.getMPCost
LDA ($F4),Y
PLY
BRA fka_4F45

.calculateLore
LDA $3A7B                    ; (get attack #)
SEC
SBC #$8B                    ; turn our raw spell ID into a 0-23 Lore ID
STA $F0
LDA #$DC                    ; this is our first Lore slot in the character's spell list
BRA .loreEntersHere

.calculateSummon            ; rather than looking for the spell ID, I'm operating under
REP #$20                    ; the assumption that if someone is using Summon, it's already
LDA $302C,X                    ; checked for the equipped Esper, so I'm just loading the MP cost
TAX                            ; from the first entry in the character's list
SEP #$20
LDA $0003,X



fka_4F45: JMP $4F54            ; (clean up stack and exit)
fka_4F53: JMP $4F53

print "CalculateMPDeduction ends at: ",pc," and used ",bytes," bytes of space."