From b1b30687434b992623047ec24a6b9558cac1f779 Mon Sep 17 00:00:00 2001
From: lahm86 <33758420+lahm86@users.noreply.github.com>
Date: Thu, 6 Feb 2025 14:33:43 +0000
Subject: [PATCH] items: introduce Item_GetIndex

This provides a common function to retrieve an item index.
---
 src/libtrx/game/items.c                        | 5 +++++
 src/libtrx/include/libtrx/game/items/common.h  | 1 +
 src/tr1/game/lara/cheat.c                      | 2 +-
 src/tr1/game/overlay.c                         | 2 +-
 src/tr2/game/lara/cheat.c                      | 2 +-
 src/tr2/game/objects/creatures/skidoo_driver.c | 5 ++---
 6 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/libtrx/game/items.c b/src/libtrx/game/items.c
index c025bee66..5a2837efc 100644
--- a/src/libtrx/game/items.c
+++ b/src/libtrx/game/items.c
@@ -26,6 +26,11 @@ void Item_TakeDamage(
     }
 }
 
+int16_t Item_GetIndex(const ITEM *const item)
+{
+    return item - Item_Get(0);
+}
+
 ITEM *Item_Find(const GAME_OBJECT_ID obj_id)
 {
     for (int32_t item_num = 0; item_num < Item_GetTotalCount(); item_num++) {
diff --git a/src/libtrx/include/libtrx/game/items/common.h b/src/libtrx/include/libtrx/game/items/common.h
index 3a554caee..24dfd2901 100644
--- a/src/libtrx/include/libtrx/game/items/common.h
+++ b/src/libtrx/include/libtrx/game/items/common.h
@@ -4,6 +4,7 @@
 #include "./types.h"
 
 ITEM *Item_Get(int16_t num);
+int16_t Item_GetIndex(const ITEM *item);
 ITEM *Item_Find(GAME_OBJECT_ID obj_id);
 int32_t Item_GetTotalCount(void);
 int32_t Item_GetDistance(const ITEM *item, const XYZ_32 *target);
diff --git a/src/tr1/game/lara/cheat.c b/src/tr1/game/lara/cheat.c
index 10276b19b..d89911d61 100644
--- a/src/tr1/game/lara/cheat.c
+++ b/src/tr1/game/lara/cheat.c
@@ -448,7 +448,7 @@ bool Lara_Cheat_Teleport(int32_t x, int32_t y, int32_t z)
     g_LaraItem->floor = height;
 
     if (g_LaraItem->room_num != room_num) {
-        const int16_t item_num = g_LaraItem - Item_Get(0);
+        const int16_t item_num = Item_GetIndex(g_LaraItem);
         Item_NewRoom(item_num, room_num);
     }
 
diff --git a/src/tr1/game/overlay.c b/src/tr1/game/overlay.c
index 46373c5cb..558785bcd 100644
--- a/src/tr1/game/overlay.c
+++ b/src/tr1/game/overlay.c
@@ -569,7 +569,7 @@ static void M_BarDrawEnemy(void)
         break;
 
     case BSM_BOSS_ONLY:
-        m_EnemyBar.show = Creature_IsBoss(g_Lara.target - Item_Get(0));
+        m_EnemyBar.show = Creature_IsBoss(Item_GetIndex(g_Lara.target));
         break;
     }
 
diff --git a/src/tr2/game/lara/cheat.c b/src/tr2/game/lara/cheat.c
index 6f6341410..a07feefdf 100644
--- a/src/tr2/game/lara/cheat.c
+++ b/src/tr2/game/lara/cheat.c
@@ -373,7 +373,7 @@ bool Lara_Cheat_Teleport(int32_t x, int32_t y, int32_t z)
     g_LaraItem->floor = height;
 
     if (g_LaraItem->room_num != room_num) {
-        const int16_t item_num = g_LaraItem - Item_Get(0);
+        const int16_t item_num = Item_GetIndex(g_LaraItem);
         Item_NewRoom(item_num, room_num);
     }
 
diff --git a/src/tr2/game/objects/creatures/skidoo_driver.c b/src/tr2/game/objects/creatures/skidoo_driver.c
index 2b4de933a..7f062ffdf 100644
--- a/src/tr2/game/objects/creatures/skidoo_driver.c
+++ b/src/tr2/game/objects/creatures/skidoo_driver.c
@@ -40,8 +40,7 @@ static int16_t M_ControlAlive(ITEM *driver_item, ITEM *skidoo_item);
 
 static void M_KillDriver(ITEM *const driver_item)
 {
-    // TODO: Item_GetIndex(const ITEM *item)
-    const int32_t driver_item_num = driver_item - Item_Get(0);
+    const int32_t driver_item_num = Item_GetIndex(driver_item);
     Item_RemoveActive(driver_item_num);
     driver_item->collidable = 0;
     driver_item->flags |= IF_ONE_SHOT;
@@ -50,7 +49,7 @@ static void M_KillDriver(ITEM *const driver_item)
 
 static void M_MakeMountable(ITEM *const skidoo_item)
 {
-    const int32_t skidoo_item_num = skidoo_item - Item_Get(0);
+    const int32_t skidoo_item_num = Item_GetIndex(skidoo_item);
     LOT_DisableBaddieAI(skidoo_item_num);
     skidoo_item->object_id = O_SKIDOO_FAST;
     skidoo_item->status = IS_DEACTIVATED;