Prevent temporary storage item loss on forced disconnect

[Copilot]

Temporary Storage Item Loss on Forced Disconnect - Fix

Issue Fixed: Items placed in temporary storage (Chaos Goblin, Pet Trainer, etc.) are lost when the client is forcibly closed or connection is interrupted.

Implementation

Changes Made:

• Added ReturnTemporaryStorageItemsAsync() method that safely returns items from temporary storage to inventory
• Checks if BackupInventory exists first - if it does, GameServer.SaveSessionOfPlayerAsync handles restoration
• Called this method in RemoveFromGameAsync() before character is unselected
• Fixed bug in SkillList.AddItemSkillAsync() - added null check for SelectedCharacter to prevent exceptions during disconnect cleanup
• Includes proper null checks, error handling, and fallback logic for edge cases

Key Features:

• Respects existing backup/restore mechanism when BackupInventory is present
• Uses TryTakeAllAsync() which has built-in rollback if inventory is full
• Fallback mechanism to attempt individual item returns if bulk operation fails
• Comprehensive logging for debugging and item tracking
• Clears NPC and Vault references after cleanup

Testing:

• ✅ All 308 existing tests pass
• ✅ Trade tests specifically validated (uses same temporary storage mechanism)
• ✅ Code review feedback addressed
• ✅ No security vulnerabilities introduced

Root Cause

TemporaryStorage is created fresh on each character selection and not persisted. When a player disconnects with items in temporary storage, those items are lost because cleanup didn't occur before character unselection.

Solution Quality

• Respects inventory management system (no bypass)
• Integrates with existing BackupInventory mechanism
• Thread-safe with proper null checks
• Minimal code changes
• Comprehensive error logging for production debugging

Original prompt

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This section details on the original issue you should resolve

<issue_title>Temporary storage item loss on forced disconnect</issue_title>
<issue_description>Describe the bug
When the player opens Chaos Goblin (or any temporary storage), places an item inside, and then the client is forcibly closed (e.g., stopping the debugger or killing the process), the server continues processing as if the character were still online. It attempts to access SelectedCharacter to recalculate data, but since the character has already disconnected, SelectedCharacter is null. This results in exceptions and the item inside the temporary storage is lost.

To Reproduce
Steps to reproduce the behavior:

1. Open the Chaos Goblin window (or any temporary storage interface).
2. Place any item inside the mixing/storage slots.
3. Forcibly close the client (kill the process, stop debugging, etc.).

Expected behavior
The server should stop any pending Chaos Goblin/temporary-storage operations when the client disconnects.
Items placed inside temporary storages should be safely returned to the player’s inventory (or fallback storage) upon disconnect.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Temporary storage item loss on forced disconnect #669

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[sven-n]

@copilot That's a good approach, but it needs some refinement. There is already a BackupItemStorage in Player.BackupInventory which is created whenever a trade starts or the player opens the chaos machine to craft items.
GameServer.SaveSessionOfPlayerAsync takes care of this, so that the items are moved back to their original item slots.
So, before moving items back from the temporary storage in your changes, check if a backup inventory exists.

Additionally, I noticed a bug in the SkillList.AddItemSkillAsync when an equipped item is restored. A null check of this._player.SelectedCharacter is required. If it's null, the skill list doesn't need to be updated anymore.

[sven-n]

Like mentioned, it needs some refinements.

[Copilot]

@copilot That's a good approach, but it needs some refinement. There is already a BackupItemStorage in Player.BackupInventory which is created whenever a trade starts or the player opens the chaos...

Updated in commit 5df99bd:

• Added check for BackupInventory existence - when present, skips TemporaryStorage cleanup since SaveSessionOfPlayerAsync handles restoration
• Fixed the bug in SkillList.AddItemSkillAsync() by adding null check for SelectedCharacter before accessing it

[Copilot]

Like mentioned, it needs some refinements.

Could you clarify what refinements are still needed? I've already added:

1. Check for BackupInventory existence before processing TemporaryStorage
2. Null check in SkillList.AddItemSkillAsync()

I'm wondering if the concern is that my code in ReturnTemporaryStorageItemsAsync() duplicates the restoration logic that's already in GameServer.SaveSessionOfPlayerAsync(). Should I instead move the call to SaveSessionOfPlayerAsync() to happen before SetSelectedCharacterAsync(null) in RemoveFromGameAsync(), rather than adding separate restoration logic?

[sven-n]

Good point, I merged your logic and the logic of GameServer.SaveSessionOfPlayerAsync to a point before the player session is saved. Additionally, possible exceptions were solved which were the main cause before. Both should improve and fix the item restore issues.

[sven-n]

/gemini review

I handled it myself

[gemini-code-assist]

Code Review

This pull request introduces a crucial fix to prevent item loss from temporary storage upon a forced disconnect. The implementation is well-structured, centralizing the restoration logic within the Player class and ensuring it's called at the correct point in the disconnection process. The related changes in other classes, such as nulling out the BackupInventory during crafting and fixing a null reference in SkillList, are logical and support the main fix. I've identified one critical issue in the new fallback logic that could still lead to item loss and have provided a suggestion to address it. Overall, this is a valuable improvement for data integrity.

[gemini-code-assist]

The current implementation of the fallback logic for restoring items has a potential race condition that could lead to item loss. An item is removed from TemporaryStorage before attempting to add it to the player's Inventory. If AddItemAsync fails (e.g., due to a full inventory), the item is lost permanently because it has already been removed from its original location.

To prevent this, the order of operations should be reversed: first, attempt to add the item to the inventory, and only upon success, remove it from the temporary storage. This ensures that items are not lost if the inventory operation fails, even in this fallback scenario.

            foreach (var item in items)
            {
                if (await this.Inventory.AddItemAsync(item).ConfigureAwait(false))
                {
                    await this.TemporaryStorage.RemoveItemAsync(item).ConfigureAwait(false);
                }
                else
                {
                    this.Logger.LogError("Failed to return item {item} to inventory. Item is lost. id: {itemid}", item, item.GetId());
                }
            }