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@googleben
googleben committed Feb 7, 2020
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15 changes: 15 additions & 0 deletions README.md
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# Pokemon Emerald Party Randomizer

This is a romhack for Pokemon Emerald that randomizes your party's pokemon at the beginning of every battle; each pokemon in your party becomes a new pokmeon chosen randomly from every pokemon in the game. It preserves EVs, IVs, contest conditions, HP percentage, XP percentage, shiny/pokerus, and nickname across randomizations, and the moves of the new pokemon are the same as if they were found in the wild at that level. Pokemon will also be added to the pokedex if you get them through randomization.

# Download

Downloads can be found on the [releases page](https://github.com/googleben/EmeraldPartyRandomizer/releases) of this repository.

# Installation & Use

The hack is distributed as a .bps file used to patch your Pokemon Emerald ROM. You must acquire a Pokemon Emerald ROM to use this romhack; the patch file only contains my changes. .bps patches can be used with a patching tool called [Flips](https://www.romhacking.net/utilities/1040/) or directly inside some emulators. The ROM to patch is release #1986, which should be Pokemon Emerald U/E. The correct rom should have the SHA1 checksum `f3ae088181bf583e55daf962a92bb46f4f1d07b7` if you want to check that. After patching your rom (either by creating a new file or in-emulator), the randomizer will just work!

# About The Code

This randomizer works by modifying the code that's called at the beginning of every battle. In the [pokeemerald project](https://github.com/pret/pokeemerald) the function that's modified is SetUpBattleVarsAndBirchZigzagoon in battle_controllers.c. All it does is call my custon function rndParty if the check for being the first battle fails. Note that all the code is marked as static methods -- this is on purpose to make compilation easier by avoiding introducing another file to link, since the setup can be a little precarious.
233 changes: 233 additions & 0 deletions src/party_randomizer.c
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#include "global.h"
#include "pokemon.h"
#include "pokedex.h"
#include "constants/moves.h"
#include "random.h"
#include "constants/species.h"

//intended to be included and used in battle_controllers.c during battle setup

//randomizes the entire player's party
static void rndParty(void);
//randomizes a pokemon
static void rndPkmn(struct Pokemon* mon);

static void EncryptBoxMon(struct BoxPokemon *boxMon)
{
u32 i;
for (i = 0; i < 12; i++)
{
boxMon->secure.raw[i] ^= boxMon->personality;
boxMon->secure.raw[i] ^= boxMon->otId;
}
}

static void DecryptBoxMon(struct BoxPokemon *boxMon)
{
u32 i;
for (i = 0; i < 12; i++)
{
boxMon->secure.raw[i] ^= boxMon->otId;
boxMon->secure.raw[i] ^= boxMon->personality;
}
}

#define SUBSTRUCT_CASE(n, v1, v2, v3, v4) \
case n: \
{ \
union PokemonSubstruct *substructs0 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs1 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs2 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs3 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs4 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs5 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs6 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs7 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs8 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs9 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs10 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs11 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs12 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs13 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs14 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs15 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs16 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs17 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs18 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs19 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs20 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs21 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs22 = boxMon->secure.substructs; \
union PokemonSubstruct *substructs23 = boxMon->secure.substructs; \
\
switch (substructType) \
{ \
case 0: \
substruct = &substructs ## n [v1]; \
break; \
case 1: \
substruct = &substructs ## n [v2]; \
break; \
case 2: \
substruct = &substructs ## n [v3]; \
break; \
case 3: \
substruct = &substructs ## n [v4]; \
break; \
} \
break; \
} \


static union PokemonSubstruct *GetSubstruct(struct BoxPokemon *boxMon, u32 personality, u8 substructType)
{
union PokemonSubstruct *substruct = NULL;

switch (personality % 24)
{
SUBSTRUCT_CASE( 0,0,1,2,3)
SUBSTRUCT_CASE( 1,0,1,3,2)
SUBSTRUCT_CASE( 2,0,2,1,3)
SUBSTRUCT_CASE( 3,0,3,1,2)
SUBSTRUCT_CASE( 4,0,2,3,1)
SUBSTRUCT_CASE( 5,0,3,2,1)
SUBSTRUCT_CASE( 6,1,0,2,3)
SUBSTRUCT_CASE( 7,1,0,3,2)
SUBSTRUCT_CASE( 8,2,0,1,3)
SUBSTRUCT_CASE( 9,3,0,1,2)
SUBSTRUCT_CASE(10,2,0,3,1)
SUBSTRUCT_CASE(11,3,0,2,1)
SUBSTRUCT_CASE(12,1,2,0,3)
SUBSTRUCT_CASE(13,1,3,0,2)
SUBSTRUCT_CASE(14,2,1,0,3)
SUBSTRUCT_CASE(15,3,1,0,2)
SUBSTRUCT_CASE(16,2,3,0,1)
SUBSTRUCT_CASE(17,3,2,0,1)
SUBSTRUCT_CASE(18,1,2,3,0)
SUBSTRUCT_CASE(19,1,3,2,0)
SUBSTRUCT_CASE(20,2,1,3,0)
SUBSTRUCT_CASE(21,3,1,2,0)
SUBSTRUCT_CASE(22,2,3,1,0)
SUBSTRUCT_CASE(23,3,2,1,0)
}

return substruct;
}

static u16 CalculateBoxMonChecksum(struct BoxPokemon *boxMon)
{
u16 checksum = 0;
union PokemonSubstruct *substruct0 = GetSubstruct(boxMon, boxMon->personality, 0);
union PokemonSubstruct *substruct1 = GetSubstruct(boxMon, boxMon->personality, 1);
union PokemonSubstruct *substruct2 = GetSubstruct(boxMon, boxMon->personality, 2);
union PokemonSubstruct *substruct3 = GetSubstruct(boxMon, boxMon->personality, 3);
s32 i;

for (i = 0; i < 6; i++)
checksum += substruct0->raw[i];

for (i = 0; i < 6; i++)
checksum += substruct1->raw[i];

for (i = 0; i < 6; i++)
checksum += substruct2->raw[i];

for (i = 0; i < 6; i++)
checksum += substruct3->raw[i];

return checksum;
}

static void rndParty(void) {
s32 numMons = CalculatePlayerPartyCount();
s32 i;
u16 dexNum;
u32 personality;
for (i = 0; i < numMons; i++) {
rndPkmn(&gPlayerParty[i]);
dexNum = SpeciesToNationalPokedexNum(GetMonData(&gPlayerParty[i], MON_DATA_SPECIES, 0));
personality = GetMonData(&gPlayerParty[i], MON_DATA_PERSONALITY, 0);
HandleSetPokedexFlag(dexNum, FLAG_SET_SEEN, personality);
HandleSetPokedexFlag(dexNum, FLAG_SET_CAUGHT, personality);
}
}

static void rndPkmn(struct Pokemon* mon) {
struct PokemonSubstruct2 s2;
struct PokemonSubstruct2 *substruct2;
struct PokemonSubstruct3 s3;
struct PokemonSubstruct3 *substruct3;
u8 level;
u32 exp;
u16 species;
u8 nextLevel;
u32 xpa, xpb, xpc, xpd;
f32 hpr, xpr;
u16 prevHp;
u16 n = Random() % (NUM_SPECIES - 1) + 1;


//store BoxPokemon data
struct BoxPokemon* box = &mon->box;
u32 personality = box->personality;
u8 nickname[POKEMON_NAME_LENGTH];
s32 i;
u16 heldItem = GetMonData(mon, MON_DATA_HELD_ITEM, NULL);
GetMonData(mon, MON_DATA_NICKNAME, nickname);

//if we got bad species id (?? pokemon), try to random again. If that doesn't work, just choose one.
if (n >= SPECIES_OLD_UNOWN_B && n <= SPECIES_OLD_UNOWN_Z) n = Random() % (NUM_SPECIES - 2) + 1;
if (n >= SPECIES_OLD_UNOWN_B && n <= SPECIES_OLD_UNOWN_Z) n = SPECIES_OLD_UNOWN_B - 1;
//calculate XP and HP percentages
level = mon->level;
exp = GetMonData(mon, MON_DATA_EXP, NULL);
species = GetMonData(mon, MON_DATA_SPECIES, 0);
nextLevel = GetMonData(mon, MON_DATA_LEVEL, 0) + 1;
xpa = gExperienceTables[gBaseStats[species].growthRate][level];
xpb = gExperienceTables[gBaseStats[species].growthRate][nextLevel];
xpc = gExperienceTables[gBaseStats[n].growthRate][level];
xpd = gExperienceTables[gBaseStats[n].growthRate][nextLevel];

hpr = mon->hp / (f32)mon->maxHP;
prevHp = mon->hp;

xpr = (exp - (f32)xpa) / (xpb-xpa);
//calculate new XP
exp = xpr * (xpd - xpc) + xpc;

//store data from substruct 2 and 3
substruct2 = &(GetSubstruct(&mon->box, mon->box.personality, 2)->type2);
substruct3 = &(GetSubstruct(&mon->box, mon->box.personality, 3)->type3);
DecryptBoxMon(&mon->box);
s2 = *substruct2;
s3 = *substruct3;

//create the pokemon, then set XP and HP from the ratios calculated earlier
CreateMon(mon, n, level, 32, 0, 0, OT_ID_PLAYER_ID, 0);
SetMonData(mon, MON_DATA_EXP, &exp);


//restore substruct data
substruct2 = &(GetSubstruct(&mon->box, mon->box.personality, 2)->type2);
substruct3 = &(GetSubstruct(&mon->box, mon->box.personality, 3)->type3);
DecryptBoxMon(&mon->box);
*substruct2 = s2;
*substruct3 = s3;
mon->box.checksum = CalculateBoxMonChecksum(&mon->box);
EncryptBoxMon(&mon->box);

//restore BoxPokemon data
box = &mon->box;
//SetMonData(mon, MON_DATA_PERSONALITY, &personality);
//box->personality = personality;
SetMonData(mon, MON_DATA_NICKNAME, nickname);
SetMonData(mon, MON_DATA_HELD_ITEM, &heldItem);
personality = 4294967295u;
SetMonData(mon, MON_DATA_FATEFUL_ENCOUNTER, &personality);
SetMonData(mon, MON_DATA_OBEDIENCE, &personality);


CalculateMonStats(mon);
mon->hp = mon->maxHP * hpr + 0.5f;
if (mon->hp == 0 && prevHp > 0) mon->hp = 1;
}

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