# BPC_ActiveItemSystem — Active Item System

**Parent Class:** `ActorComponent`
**Category:** Inventory
**Target UE Version:** 5.5–5.7
**Build Phase:** 3 — Inventory

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## 1. Overview

`BPC_ActiveItemSystem` manages the player's currently selected/active item and quick slot assignments. It reads from [`BPC_InventorySystem`](BPC_InventorySystem.md) and maps up to 8 quick slots to inventory items, handling hotkey input, item switching, and active item context (usable, throwable, consumable).

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## 2. Enums

### `E_QuickSlot`

| Value | Description |
|-------|-------------|
| `Slot_1` | Hotkey 1 |
| `Slot_2` | Hotkey 2 |
| `Slot_3` | Hotkey 3 |
| `Slot_4` | Hotkey 4 |
| `Slot_5` | Hotkey 5 |
| `Slot_6` | Hotkey 6 |
| `Slot_7` | Hotkey 7 |
| `Slot_8` | Hotkey 8 |

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## 3. Variables

| Variable | Type | Description |
|----------|------|-------------|
| `QuickSlots` | `TMap<E_QuickSlot, FGuid>` | Hotkey → Inventory Item ID mapping |
| `ActiveSlot` | `E_QuickSlot` | Currently selected quick slot |
| `ActiveItem` | `S_InventoryEntry` | Currently active item data |
| `bHasActiveItem` | `bool` | An item is currently selected |
| `bCanSwitchItems` | `bool` | Item switching allowed (not during anim) |
| `SwitchCooldown` | `float` | Min time between item switches |

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## 4. Functions

| Function | Description |
|----------|-------------|
| `SetQuickSlot` | Assigns an inventory item to a quick slot |
| `ClearQuickSlot` | Clears a quick slot assignment |
| `SelectSlot` | Sets the active quick slot by key press |
| `GetActiveItem` | Returns current `S_InventoryEntry` |
| `UseActiveItem` | Uses/consumes the active item |
| `CycleNextItem` | Selects the next populated quick slot |
| `CyclePreviousItem` | Selects the previous populated quick slot |
| `IsQuickSlotEmpty` | Returns true if quick slot has no item |
| `GetQuickSlotItem` | Returns item in a specific quick slot |

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## 5. Event Dispatchers

| Dispatcher | Payload | Description |
|------------|---------|-------------|
| `OnActiveItemChanged` | `S_InventoryEntry NewItem`, `E_QuickSlot Slot` | Active item switched |
| `OnQuickSlotAssigned` | `E_QuickSlot Slot`, `FGuid ItemID` | Item assigned to quick slot |
| `OnQuickSlotCleared` | `E_QuickSlot Slot` | Quick slot cleared |
| `OnActiveItemUsed` | `S_InventoryEntry Item` | Active item consumed |

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## 6. Dependencies & Communication

| System | Relationship |
|--------|--------------|
| `BPC_InventorySystem` | Reads inventory slots; source of truth for items |
| `BPC_EquipmentSlotSystem` | Automatically updates quick slots on equipment change |
| `WBP_HUDController` | Displays active item in HUD |
| `BPC_HealthSystem` | Consumed health items trigger healing |

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## 7. Reuse Notes
- Quick slots are configurable per project (4-8 slots)
- Active item system is the bridge between inventory data and gameplay input