From e42fab04c4966714922f56ed86641fe83a51ec72 Mon Sep 17 00:00:00 2001
From: Eric Robinson <68359262+kphoenix137@users.noreply.github.com>
Date: Thu, 19 Oct 2023 03:34:09 -0400
Subject: [PATCH] Fix Item Validation (#6723)

---
 Source/pack.cpp | 60 ++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 54 insertions(+), 6 deletions(-)

diff --git a/Source/pack.cpp b/Source/pack.cpp
index 85f37c978..3640768a7 100644
--- a/Source/pack.cpp
+++ b/Source/pack.cpp
@@ -87,12 +87,16 @@ bool IsCreationFlagComboValid(uint16_t iCreateInfo)
 	const bool isPregenItem = (iCreateInfo & CF_PREGEN) != 0;
 	const bool isUsefulItem = (iCreateInfo & CF_USEFUL) == CF_USEFUL;
 
-	if (isPregenItem)
+	if (isPregenItem) {
+		// Pregen flags are discarded when an item is picked up, therefore impossible to have in the inventory
 		return false;
+	}
 	if (isUsefulItem && (iCreateInfo & ~CF_USEFUL) != 0)
 		return false;
-	if (isTownItem && hasMultipleFlags(iCreateInfo))
+	if (isTownItem && hasMultipleFlags(iCreateInfo)) {
+		// Items from town can only have 1 towner flag
 		return false;
+	}
 	return true;
 }
 
@@ -100,11 +104,13 @@ bool IsTownItemValid(uint16_t iCreateInfo)
 {
 	const uint8_t level = iCreateInfo & CF_LEVEL;
 	const bool isBoyItem = (iCreateInfo & CF_BOY) != 0;
+	const uint8_t maxTownItemLevel = 30;
 
+	// Wirt items in multiplayer are equal to the level of the player, therefore they cannot exceed the max character level
 	if (isBoyItem && level <= MaxCharacterLevel)
 		return true;
 
-	return level <= 30;
+	return level <= maxTownItemLevel;
 }
 
 bool IsUniqueMonsterItemValid(uint16_t iCreateInfo, uint32_t dwBuff)
@@ -112,16 +118,18 @@ bool IsUniqueMonsterItemValid(uint16_t iCreateInfo, uint32_t dwBuff)
 	const uint8_t level = iCreateInfo & CF_LEVEL;
 	const bool isHellfireItem = (dwBuff & CF_HELLFIRE) != 0;
 
+	// Check all unique monster levels to see if they match the item level
 	for (int i = 0; UniqueMonstersData[i].mName != nullptr; i++) {
 		const auto &uniqueMonsterData = UniqueMonstersData[i];
 		const auto &uniqueMonsterLevel = static_cast<uint8_t>(MonstersData[uniqueMonsterData.mtype].level);
 
-		if (!isHellfireItem && IsAnyOf(uniqueMonsterData.mtype, MT_HORKDMN, MT_DEFILER, MT_NAKRUL)) {
-			// These monsters don't appear in Diablo
+		if (IsAnyOf(uniqueMonsterData.mtype, MT_DEFILER, MT_NAKRUL, MT_HORKDMN)) {
+			// These monsters don't use their mlvl for item generation
 			continue;
 		}
 
 		if (level == uniqueMonsterLevel) {
+			// If the ilvl matches the mlvl, we confirm the item is legitimate
 			return true;
 		}
 	}
@@ -134,24 +142,62 @@ bool IsDungeonItemValid(uint16_t iCreateInfo, uint32_t dwBuff)
 	const uint8_t level = iCreateInfo & CF_LEVEL;
 	const bool isHellfireItem = (dwBuff & CF_HELLFIRE) != 0;
 
+	// Check all monster levels to see if they match the item level
 	for (int16_t i = 0; i < static_cast<int16_t>(NUM_MTYPES); i++) {
 		const auto &monsterData = MonstersData[i];
 		auto monsterLevel = static_cast<uint8_t>(monsterData.level);
 
 		if (i != MT_DIABLO && monsterData.availability == MonsterAvailability::Never) {
+			// Skip monsters that are unable to appear in the game
 			continue;
 		}
 
 		if (i == MT_DIABLO && !isHellfireItem) {
+			// Adjust The Dark Lord's mlvl if the item isn't a Hellfire item to match the Diablo mlvl
 			monsterLevel -= 15;
 		}
 
 		if (level == monsterLevel) {
+			// If the ilvl matches the mlvl, we confirm the item is legitimate
 			return true;
 		}
 	}
 
-	return level <= 30;
+	if (isHellfireItem) {
+		uint8_t hellfireMaxDungeonLevel = 24;
+
+		// Hellfire adjusts the currlevel minus 7 in dungeon levels 20-24 for generating items
+		hellfireMaxDungeonLevel -= 7;
+		return level <= (hellfireMaxDungeonLevel * 2);
+	}
+
+	uint8_t diabloMaxDungeonLevel = 16;
+
+	// Diablo doesn't have containers that drop items in dungeon level 16, therefore we decrement by 1
+	diabloMaxDungeonLevel--;
+	return level <= (diabloMaxDungeonLevel * 2);
+}
+
+bool RecreateHellfireSpellBook(const Player &player, const ItemNetPack &packedItem, Item &item)
+{
+	Item spellBook {};
+	RecreateItem(player, packedItem.item, spellBook);
+
+	// Hellfire uses the spell book level when generating items via CreateSpellBook()
+	int spellBookLevel = GetSpellBookLevel(spellBook._iSpell);
+
+	// CreateSpellBook() adds 1 to the spell level for ilvl
+	spellBookLevel++;
+
+	if (spellBookLevel >= 1 && (spellBook._iCreateInfo & CF_LEVEL) == spellBookLevel * 2) {
+		// The ilvl matches the result for a spell book drop, so we confirm the item is legitimate
+		item = spellBook;
+		return true;
+	}
+
+	ValidateFields(spellBook._iCreateInfo, spellBook.dwBuff, IsDungeonItemValid(spellBook._iCreateInfo, spellBook.dwBuff));
+	item = spellBook;
+	return true;
 }
 } // namespace
 
@@ -490,6 +536,8 @@ bool UnPackNetItem(const Player &player, const ItemNetPack &packedItem, Item &it
 		ValidateField(creationFlags, IsTownItemValid(creationFlags));
 	else if ((creationFlags & CF_USEFUL) == CF_UPER15)
 		ValidateFields(creationFlags, dwBuff, IsUniqueMonsterItemValid(creationFlags, dwBuff));
+	else if ((dwBuff & CF_HELLFIRE) != 0 && AllItemsList[idx].iMiscId == IMISC_BOOK)
+		return RecreateHellfireSpellBook(player, packedItem, item);
 	else
 		ValidateFields(creationFlags, dwBuff, IsDungeonItemValid(creationFlags, dwBuff));