From 414aa76c233d64b29ae895d34eddbb1715deb80e Mon Sep 17 00:00:00 2001
From: PhlexPlexico <flexing@phlexplexi.co>
Date: Sun, 25 Feb 2024 17:23:45 -0600
Subject: [PATCH] Adjust removing items to give next trade item if it is not
 none. (#45)

---
 code/include/rnd/savefile.h          |  1 +
 code/mm.ld                           |  4 ++++
 code/source/asm/trade_item_hooks.s   |  8 ++++++++
 code/source/asm/trade_item_patches.s |  5 +++++
 code/source/rnd/savefile.cpp         | 22 ++++++++++++++++++++++
 5 files changed, 40 insertions(+)

diff --git a/code/include/rnd/savefile.h b/code/include/rnd/savefile.h
index 1cb8b4a7..c1b65112 100644
--- a/code/include/rnd/savefile.h
+++ b/code/include/rnd/savefile.h
@@ -36,6 +36,7 @@ namespace rnd {
   extern "C" void SaveFile_RemoveStoredTradeItem(u16, u8);
   extern "C" void SaveFile_RemoveTradeItemFromSlot(u16, u8);
   extern "C" u8 SaveFile_GetItemCurrentlyInSlot(u8);
+  extern "C" void SaveFile_SetNextTradeSlotItem(u8);
 
   typedef struct {
     u32 version;  // Needs to always be the first field of the structure
diff --git a/code/mm.ld b/code/mm.ld
index e95c8bcb..9d83ad40 100644
--- a/code/mm.ld
+++ b/code/mm.ld
@@ -67,6 +67,10 @@ SECTIONS{
     *(.patch_RemoveTradeItemFromSlot)
   }
 
+  .patch_SwapTradeItemFromExtSlot 0x1AFEA8 : {
+    *(.patch_SwapTradeItemFromExtSlot)
+  }
+
   .patch_OverrideCutsceneNextEntrance 0x1B1834 : {
     *(.patch_OverrideCutsceneNextEntrance)
   }
diff --git a/code/source/asm/trade_item_hooks.s b/code/source/asm/trade_item_hooks.s
index 5f16d48e..28a71e06 100644
--- a/code/source/asm/trade_item_hooks.s
+++ b/code/source/asm/trade_item_hooks.s
@@ -32,6 +32,14 @@ hook_RemoveTradeItemFromExtSlot:
   cpy r4,r0
   bx lr
 
+.global hook_SwapTradeItemFromExtSlot
+hook_SwapTradeItemFromExtSlot:
+  push {r0-r12,lr}
+  bl SaveFile_SetNextTradeSlotItem
+  pop {r0-r12,lr}
+  mov r2, #0xFF
+  bx lr
+
 .global hook_RemoveKafeiItemFromExtSlot
 hook_RemoveKafeiItemFromExtSlot:
   push {r0-r12, lr}
diff --git a/code/source/asm/trade_item_patches.s b/code/source/asm/trade_item_patches.s
index b36b7ca2..841b866f 100644
--- a/code/source/asm/trade_item_patches.s
+++ b/code/source/asm/trade_item_patches.s
@@ -5,6 +5,11 @@
 patch_RemoveTradeItemFromSlot:
   bl hook_RemoveTradeItemFromExtSlot
 
+.section .patch_SwapTradeItemFromExtSlot
+.global patch_SwapTradeItemFromExtSlot
+patch_SwapTradeItemFromExtSlot:
+  bl hook_SwapTradeItemFromExtSlot
+
 .section .patch_DoNotRemoveTradeItems
 .global patch_DoNotRemoveTradeItems
 patch_DoNotRemoveTradeItems:
diff --git a/code/source/rnd/savefile.cpp b/code/source/rnd/savefile.cpp
index 7426433c..1f169816 100644
--- a/code/source/rnd/savefile.cpp
+++ b/code/source/rnd/savefile.cpp
@@ -940,6 +940,8 @@ namespace rnd {
           break;
         }
       }
+    } else if (slot == 17 && item == (u16)game::ItemId::LetterToKafei) {
+      gExtSaveData.collectedTradeItems[6] = game::ItemId::None;
     }
   }
 
@@ -949,6 +951,26 @@ namespace rnd {
 #endif
     return (u8)game::GetCommonData().save.inventory.items[slot];
   }
+
+  extern "C" void SaveFile_SetNextTradeSlotItem(u8 slot) {
+    if (slot != 5 && slot != 17)
+      return;
+    game::ItemId firstItem = game::ItemId::None;
+    for (int i = 0; i < 9; i++) {
+      if (firstItem == game::ItemId::None) {
+        if (slot == 17 && i > 5 && i < 8 && gExtSaveData.collectedTradeItems[i] != game::ItemId::None) {
+          firstItem = gExtSaveData.collectedTradeItems[i];
+          break;
+        } else if (slot == 5 && i < 5 && gExtSaveData.collectedTradeItems[i] != game::ItemId::None) {
+          firstItem = gExtSaveData.collectedTradeItems[i];
+          break;
+        }
+      }
+    }
+    // Place the item in inventory, if there is no item to place it simply places none.
+    game::SaveData& saveData = game::GetCommonData().save;
+    saveData.inventory.items[slot] = firstItem;
+  }
   // SaveFile_DrawAndShowUIMessage() {
 
   // }