Ported and modded Deokishisu's Wonder Trade

I also added a script to do Wonder Trades, because why not.
Special thanks to Zeturic and Ghoulslash, as their Dynamic Trade Names feature is used here.
And to Hungry Pickle for providing the IsMegaPreEvolution function.

data/event_scripts.s

@@ -1005,6 +1005,29 @@ Common_EventScript_LegendaryFlewAway:: @ 8273776
 	release
 	end
 
+EventScript_DoWonderTrade::
+	special ChoosePartyMon
+	waitstate
+	compare VAR_0x8004, PARTY_SIZE
+	goto_if_ge EventScript_End
+	copyvar VAR_0x8005, VAR_0x8004
+	special CreateWonderTradePokemon
+	special DoInGameTradeScene
+	waitstate
+	msgbox EventScript_DoWonderTrade_Text_WannaDoAnotherWonderTrade, MSGBOX_YESNO
+	compare VAR_RESULT, YES
+	goto_if_eq EventScript_DoWonderTrade
+	msgbox EventScript_DoWonderTrade_Text_Done, MSGBOX_DEFAULT
+	closemessage
+EventScript_End:
+	end
+
+EventScript_DoWonderTrade_Text_WannaDoAnotherWonderTrade:
+	.string "Do you want to do\nanother Wonder Trade?$"
+
+EventScript_DoWonderTrade_Text_Done:
+	.string "Enjoy your new Pokémon.$"
+
 	.include "data/scripts/pc_transfer.inc"
 	.include "data/scripts/mevent.inc"
 	.include "data/scripts/abnormal_weather.inc"

data/specials.inc

@@ -535,3 +535,4 @@ gSpecials:: @ 81DBA64
 	def_special RemoveRecordsWindow
 	def_special CloseDeptStoreElevatorWindow
 	def_special TrySetBattleTowerLinkType
+	def_special CreateWonderTradePokemon

ld_script.txt

@@ -333,6 +333,7 @@ SECTIONS {
         src/gym_leader_rematch.o(.text);
         src/battle_transition_frontier.o(.text);
         src/international_string_util.o(.text);
+        src/wonder_trade.o(.text);
     } =0
 
     script_data :
@@ -689,6 +690,7 @@ SECTIONS {
         data/fonts.o(.rodata);
         src/mystery_event_msg.o(.rodata);
         data/mystery_event.o(.rodata);
+        src/wonder_trade.o(.rodata);
         src/m4a_tables.o(.rodata);
         data/sound_data.o(.rodata);
     } =0