hazards

This code hijacks regular spikes to function.
x01/x02 = spikes
x04/x08 = toxic spikes
x10     = stealth rock
x20     = sticky web

Hazards are ordered: t-spikes -> spikes -> sr -> web.
This is consistent with gen 4 but not gen 5-6.
Later gens activate them in the order the player uses them.
(web is placed last to avoid wasting time if things die to sr/spikes)

First, to hijack regular spikes:
x24EB8: 11 E0 (b 0x24ede)
x24EF2: 1C E0 (b 0x24f2e)
x24F36: 00 00 00 00
x24F68: pointer to battle script

It'd *probably* be best to make the methods in a way that they could branch to each other seamlessly.
However, I instead handled the bulk of this with a large battle script that uses 4 callasm calls.
Also, I have no luck with BSP, so you're just getting raw hex. Sorry.

Also, this code assumes you aren't putting Immunity on a Poison-type.
If you do, it won't be able to absorb Toxic Spikes. (also you're a jerk)
Also also I took the very lazy road with Stealth Rock.
It won't respect Inverse Battles or an edited type chart. Sorry.

There should be four blocks that are simply callasm() on the Hurt functions for each hazard.
(also i inserted all of these close to the main code in freed ROM space)
(you'll need to either do the same or define functions to existing ones. sorry 'bout that)

=============================================
TSpikesHurt:
=============================================

.org 0x2514D0
push {lr}
mov r0, #0x0
bl 0x16e24
mov r4, r0
bl 0x751c4

ldr r1, .HalverStruct
mov r2, #0xc
mul r0, r2, r0
add r0, r1, r0
mov r5, r0
ldrb r0, [r0, #0xa]
mov r3, #0xc
and r0, r3, r0
lsr r0, #0x2
ldr r1, .ActiveBSPointer
cmp r0, #0x0
beq SkipTSpikes


mov r6, r0
ldr r0, .BattleStruct
mov r1, #0x58
mul r1, r4, r1
add r0, r1, r0
add r0, r0, #0x20
mov r7, r0

Ability:
ldrb r1, [r7, #0x0]
cmp r1, #0x1a
beq SkipTSpikes
cmp r1, #0x11
beq SkipTSpikes

BirdCheck:
ldrb r1, [r7, #0x1]
ldrb r0, [r7, #0x2]
cmp r0, #0x2
beq SkipTSpikes
cmp r1, #0x2
beq SkipTSpikes

PoisonCheck:
cmp r0, #0x3
beq AbsorbTSpikes
cmp r1, #0x3
beq AbsorbTSpikes

SteelCheck:
cmp r0, #0x8
beq SkipTSpikes
cmp r1, #0x8
beq SkipTSpikes


cmp r6, #0x1
beq NormalTSpikes
b HarshTSpikes


SkipTSpikes:
ldr r0, .SkipTSpikesBS
ldr r1, .ActiveBSPointer
str r0, [r1, #0x0]
b End

NormalTSpikes:
ldr r0, .NormalTSpikesBS
ldr r1, .ActiveBSPointer
str r0, [r1, #0x0]
b End

HarshTSpikes:
ldr r0, .HarshTSpikesBS
ldr r1, .ActiveBSPointer
str r0, [r1, #0x0]
b End

AbsorbTSpikes:
mov r0, r5
ldrb r1, [r0, #0xa]
mov r2, #0xf3
and r1, r2, r1
strb r1, [r0, #0xa]
ldr r0, .AbsorbTSpikesBS
ldr r1, .ActiveBSPointer
str r0, [r1, #0x0]

End:
pop {r0}
bx r0

.align 2

.ActiveMon: .word 0x02023bc4
.HalverStruct: .word 0x02023de4
.ActiveBSPointer: .word 0x02023d74
.SkipTSpikesBS: .word 0x08C8947B !!fix this
.NormalTSpikesBS: .word 0x08C894AB !!fix this
.HarshTSpikesBS: .word 0x08C894BB !!fix this
.AbsorbTSpikesBS: .word 0x08C894CB !!fix this
.BattleStruct: .word 0x02023be4

/////////////////////////////////////////////

SkipTSpikesBS should point to 5 bytes before a callasm on SpikesHurt.
NormalTSpikesBS should point to 5 bytes before this:
2E 85 3E 02 02 02
16
F8 (SpikesHurt)
HarshTSpikesBS should point to 5 bytes before this:
2E 85 3E 02 02 06
16
F8 (SpikesHurt)
AbsorbTSpikesBS should point to 5 bytes before this:
10 (your "t-spikes disappeared" message ID)
12 40 00
F8 (SpikesHurt)

=============================================
SpikesHurt:
=============================================

.org 0x251580
push {lr}
mov r0, #0x0
bl 0x16e24
ldr r4, .HurtBank
strb r0, [r4, #0x0]
mov r4, r0
bl 0x751c4

ldr r1, .HalverStruct
mov r2, #0xc
mul r0, r2, r0
add r0, r1, r0
mov r5, r0
ldrb r0, [r0, #0xa]
mov r3, #0x3
and r0, r3, r0
cmp r0, #0x0
beq SkipSpikes
mov r6, r0

ldr r0, .BattleStruct
mov r1, #0x58
mul r1, r4, r1
add r0, r1, r0
add r0, #0x20
mov r7, r0

Ability:
ldrb r1, [r7, #0x0]
cmp r1, #0x1a
beq SkipSpikes
cmp r1, #0x5d
beq SkipSpikes

BirdCheck:
ldrb r0, [r7, #0x1]
ldrb r1, [r7, #0x2]
cmp r0, #0x2
beq SkipSpikes
cmp r1, #0x2
beq SkipSpikes

DamCalculate:
ldrh r0, [r7, #0xc]
mov r1, #0xa
mov r2, r6
add r2, r6, r2
sub r1, r1, r2
bl 0x1e4018

ldr r1, .DamageDealt
str r0, [r1, #0x0]
ldr r2, .ActiveBSPointer
ldr r3, .SpikesDamageBS
str r3, [r2, #0x0]
b End

SkipSpikes:
ldr r2, .ActiveBSPointer
ldr r3, .SpikesSkipBS
str r3, [r2, #0x0]

End:
pop {r0}
bx r0

.align 2
.HurtBank: .word 0x02023fdb
.HalverStruct: .word 0x02023de4
.DamageDealt: .word 0x02023d50
.ActiveBSPointer: .word 0x02023d74
.BattleStruct: .word 0x02023be4
.SpikesDamageBS: .word 0x08C894DB !!fix this
.SpikesSkipBS: .word 0x08C8948B !!fix this

/////////////////////////////////////////////

SpikesSkipBS should point to 5 bytes before a callasm on SRHurt.
SpikesDamageBS should point to 5 bytes before this:
0B 00
0C 00
41 2C 8D 1D 08
19 00 00 00 00 00 00
19 00 01 DF 8C 1D 08
F8 (SRHurt)

=============================================
SRHurt:
=============================================

.org 0x251610
push {lr}
mov r0, #0x0
bl 0x16e24
mov r4, r0
bl 0x751c4

ldr r1, .HalverStruct
mov r2, #0xc
mul r0, r2, r0
add r0, r1, r0
mov r5, r0
ldrb r0, [r0, #0xa]
mov r3, #0x10
and r0, r3, r0
cmp r0, #0x0
beq SkipSR
mov r6, r0

ldr r0, .BattleStruct
mov r1, #0x58
mul r1, r4, r1
add r0, r1, r0
add r0, #0x20
mov r7, r0

Ability:
ldrb r1, [r7, #0x0]
cmp r1, #0x5d
beq SkipSR


mov r0, #0x8
ldrb r1, [r7, #0x1]
mov r2, #0x0

TypeMatchup:
cmp r1, #0x1
beq Resist
cmp r1, #0x2
beq Weak
cmp r1, #0x4
beq Resist
cmp r1, #0x6
beq Weak
cmp r1, #0x8
beq Resist
cmp r1, #0xa
beq Weak
cmp r1, #0xf
beq Weak

b TypeLoop

Resist:
lsl r0, r0, #0x1
b TypeLoop

Weak:
lsr r0, r0, #0x1

TypeLoop:
add r2, #0x1
mov r3, r1
ldrb r1, [r7, #0x2]
cmp r1, r3
beq EndTypeLoop
cmp r2, #0x2
bne TypeMatchup

EndTypeLoop:
DamCalculate:
mov r1, r0
ldrh r0, [r7, #0xc]
bl 0x1e4018

cmp r0, #0x0
bne ApplyDamage
mov r0, #0x1

ApplyDamage:
ldr r1, .DamageDealt
str r0, [r1, #0x0]
ldr r2, .ActiveBSPointer
ldr r3, .SRDamageBS
str r3, [r2, #0x0]
b End

SkipSR:
ldr r2, .ActiveBSPointer
ldr r3, .SRSkipBS
str r3, [r2, #0x0]

End:
pop {r0}
bx r0

.align 2

.HalverStruct: .word 0x02023de4
.DamageDealt: .word 0x02023d50
.ActiveBSPointer: .word 0x02023d74
.BattleStruct: .word 0x02023be4
.SRDamageBS: .word 0x08C894FB !!fix this
.SRSkipBS: .word 0x08C8949B !!fix this

/////////////////////////////////////////////

SRSkipBS should point to 5 bytes before a callasm to WebHurt.
SRDamageBS should point to 5 bytes before this:
0B 00
0C 00
10 86 01
12 40 00
19 00 00 00 00 00 00
19 00 01 DF 8C 1D 08
F8 (WebHurt)

=============================================
WebHurt:
=============================================

.org 0x2516C0
push {lr}
mov r0, #0x0
bl 0x16e24
mov r4, r0
bl 0x751c4

ldr r1, .HalverStruct
mov r2, #0xc
mul r0, r2, r0
add r0, r1, r0
ldrb r0, [r0, #0xa]
mov r3, #0x20
and r0, r3, r0
cmp r0, #0x0
beq SkipWeb

ldr r0, .BattleStruct
mov r1, #0x48
mul r1, r4, r1
add r0, r1, r0
add r0, #0x20
mov r7, r0

Ability:
ldrb r1, [r7, #0x0]
cmp r1, #0x1a
beq SkipWeb

BirdCheck:
ldrb r1, [r7, #0x1]
ldrb r0, [r7, #0x2]
cmp r1, #0x2
beq SkipWeb
cmp r0, #0x2
beq SkipWeb


ApplyWeb:
ldr r2, .ActiveBSPointer
ldr r3, .WebApplyBS
str r3, [r2, #0x0]
b End

SkipWeb:
ldr r2, .ActiveBSPointer
ldr r3, .WebSkipBS
str r3, [r2, #0x0]

End:
pop {r0}
bx r0

.HalverStruct: .word 0x02023de4
.BattleStruct: .word 0x02023be4
.ActiveBSPointer: .word 0x02023d74
.WebApplyBS: .word 0x08C8951B !!fix this
.WebSkipBS: .word 0x08C8953B !!fix this

/////////////////////////////////////////////

WebApplyBS should point to 5 bytes before this:
10 ("caught in a web" message ID)
12 40 00
2E 85 3E 02 02 18
16
35 D0 3D 02 02 00 01 10 00
3C
WebSkipBS should point to 5 bytes before this:
35 D0 3D 02 02 00 01 10 00
3C



.............................................

This gets the four hazards working properly.
To make the moves function without memory editing, replace Spikes's script with this:
2A 00 4A 3D 02 02 MM MM XX XX XX XX
2A 00 4A 3D 02 02 NN NN YY YY YY YY
2A 00 4A 3D 02 02 OO OO ZZ ZZ ZZ ZZ
00
F8 (LaySpikes)
02
03
09
0A
10 94 00
12 40 00
28 4E 69 1D 08

Where:
MM MM is Toxic Spikes's move ID; XX XX XX XX points to its battle script
NN NN is Stealth Rock's move ID; YY YY YY YY points to its battle script
OO OO is Sticky Web's move ID;   ZZ ZZ ZZ ZZ points to its battle script

At XX XX XX XX:
00
F8 (LayToxicSpikes)
02
03
09
0A
10 ("poison spikes scattered" message ID)
12 40 00
28 4E 69 1D 08

...and so on for the other two.


=============================================
LaySpikes
=============================================

.org 0x251730

push {r4, lr}
ldr r4, .ActiveBank
ldrb r0, [r4, #0x0]
bl 0x751c4

mov r1, #0x1
eor r0, r1
lsl r0, r0, #0x18
lsr r0, r0, #0x18
ldr r1, .HalverStruct
lsl r2, r0, #0x1
add r0, r2, r0
lsl r0, r0, #0x2
add r3, r0, r1
ldrb r0, [r3, #0xa]
mov r1, #0x3
and r0, r1, r0
cmp r0, #0x3
bne LaySpikes

ldr r2, .Unknown
ldrb r1, [r4, #0x0]
lsl r0, r1, #0x2
add r0, r0, r1
lsl r0, r0, #0x2
add r0, r0, r2
ldrb r1, [r0, #0x0]
mov r2, #0x20
orr r1, r2
strb r1, [r0, #0x0]

ldr r3, .ActiveBSPointer
ldr r1, .FailAddr
str r1, [r3, #0x0]
b End


LaySpikes:
ldr r1, .HalverMarker
add r1, r2, r1
ldrh r2, [r1, #0x0]
mov r0, #0x10
orr r0, r2
strh r0, [r1, #0x0]

ldrb r0, [r3, #0xa]
add r0, #0x1
strb r0, [r3, #0xa]

End:
pop {r4}
pop {r0}
bx r0

.align 2

.ActiveBank: .word 0x02023d6b
.HalverStruct: .word 0x02023de4
.Unknown: .word 0x02023ecc
.ActiveBSPointer: .word 0x02023d74
.HalverMarker: .word 0x02023dde
.FailAddr: .word 0x081D7DEB

=============================================
LayTSpikes
=============================================

.org 0x2517C0

push {r4, lr}
ldr r4, .ActiveBank
ldrb r0, [r4, #0x0]
bl 0x751c4

mov r1, #0x1
eor r0, r1
lsl r0, r0, #0x18
lsr r0, r0, #0x18
ldr r1, .HalverStruct
lsl r2, r0, #0x1
add r0, r2, r0
lsl r0, r0, #0x2
add r3, r0, r1
ldrb r0, [r3, #0xa]
mov r1, #0xc
and r0, r1, r0
lsr r0, r0, #0x2
cmp r0, #0x3
bne LayTSpikes

ldr r2, .Unknown
ldrb r1, [r4, #0x0]
lsl r0, r1, #0x2
add r0, r0, r1
lsl r0, r0, #0x2
add r0, r0, r2
ldrb r1, [r0, #0x0]
mov r2, #0x20
orr r1, r2
strb r1, [r0, #0x0]

ldr r3, .ActiveBSPointer
ldr r1, .FailAddr
str r1, [r3, #0x0]
b End


LayTSpikes:
ldr r1, .HalverMarker
add r1, r2, r1
ldrh r2, [r1, #0x0]
mov r0, #0x10
orr r0, r2
strh r0, [r1, #0x0]

ldrb r0, [r3, #0xa]
mov r1, #0xc
and r1, r0, r1
lsr r1, r1, #0x2
add r1, #0x1
lsl r1, r1, #0x2
orr r0, r0, r1
strb r0, [r3, #0xa]

End:
pop {r4}
pop {r0}
bx r0

.align 2

.ActiveBank: .word 0x02023d6b
.HalverStruct: .word 0x02023de4
.Unknown: .word 0x02023ecc
.ActiveBSPointer: .word 0x02023d74
.HalverMarker: .word 0x02023dde
.FailAddr: .word 0x081D7DEB

=============================================
LaySR
=============================================

.org 0x251860

push {r4, lr}
ldr r4, .ActiveBank
ldrb r0, [r4, #0x0]
bl 0x751c4

mov r1, #0x1
eor r0, r1
lsl r0, r0, #0x18
lsr r0, r0, #0x18
ldr r1, .HalverStruct
lsl r2, r0, #0x1
add r0, r2, r0
lsl r0, r0, #0x2
add r3, r0, r1
ldrb r0, [r3, #0xa]
mov r1, #0x10
and r0, r1, r0
cmp r0, #0x0
beq LaySR

ldr r2, .Unknown
ldrb r1, [r4, #0x0]
lsl r0, r1, #0x2
add r0, r0, r1
lsl r0, r0, #0x2
add r0, r0, r2
ldrb r1, [r0, #0x0]
mov r2, #0x20
orr r1, r2
strb r1, [r0, #0x0]

ldr r3, .ActiveBSPointer
ldr r1, .FailAddr
str r1, [r3, #0x0]
b End


LaySR:
ldr r1, .HalverMarker
add r1, r2, r1
ldrh r2, [r1, #0x0]
mov r0, #0x10
orr r0, r2
strh r0, [r1, #0x0]

ldrb r0, [r3, #0xa]
mov r1, #0x10
orr r0, r1, r0
strb r0, [r3, #0xa]

End:
pop {r4}
pop {r0}
bx r0



.ActiveBank: .word 0x02023d6b
.HalverStruct: .word 0x02023de4
.Unknown: .word 0x02023ecc
.ActiveBSPointer: .word 0x02023d74
.HalverMarker: .word 0x02023dde
.FailAddr: .word 0x081D7DEB

=============================================
LayWeb
=============================================

.org 0x2518F0

push {r4, lr}
ldr r4, .ActiveBank
ldrb r0, [r4, #0x0]
bl 0x751c4

mov r1, #0x1
eor r0, r1
lsl r0, r0, #0x18
lsr r0, r0, #0x18
ldr r1, .HalverStruct
lsl r2, r0, #0x1
add r0, r2, r0
lsl r0, r0, #0x2
add r3, r0, r1
ldrb r0, [r3, #0xa]
mov r1, #0x20
and r0, r1, r0
cmp r0, #0x0
beq LayWeb

ldr r2, .Unknown
ldrb r1, [r4, #0x0]
lsl r0, r1, #0x2
add r0, r0, r1
lsl r0, r0, #0x2
add r0, r0, r2
ldrb r1, [r0, #0x0]
mov r2, #0x20
orr r1, r2
strb r1, [r0, #0x0]

ldr r3, .ActiveBSPointer
ldr r1, .FailAddr
str r1, [r3, #0x0]
b End


LayWeb:
ldr r1, .HalverMarker
add r1, r2, r1
ldrh r2, [r1, #0x0]
mov r0, #0x10
orr r0, r2
strh r0, [r1, #0x0]

ldrb r0, [r3, #0xa]
mov r1, #0x20
orr r0, r1, r0
strb r0, [r3, #0xa]

End:
pop {r4}
pop {r0}
bx r0

.align 2

.ActiveBank: .word 0x02023d6b
.HalverStruct: .word 0x02023de4
.Unknown: .word 0x02023ecc
.ActiveBSPointer: .word 0x02023d74
.HalverMarker: .word 0x02023dde
.FailAddr: .word 0x081D7DEB