# Backpacks API

The `EdToolsBackpackAPI` provides a comprehensive set of tools for developers to interact with the player backpack system. You can retrieve backpack data, manage its contents, and handle upgrades externally.

### Get API Instance

To begin using the Backpack API, you first need to get an instance of it from the main EdToolsAPI class.

```java
EdToolsBackpackAPI backpackAPI = EdToolsAPI.getInstance().getBackpackAPI();
```

***

### Methods

#### `getPlayerBackpackInInventory(Player player)`

Retrieves the actual `ItemStack` representing the player's backpack from their inventory.

* **player**: The player whose backpack item you want to find.
* **Returns**: The `ItemStack` of the backpack, or null if the player does not have it in their inventory.

#### `getBackpackItems(UUID uuid)`

Gets a map of all items and their quantities stored in a player's backpack.

* **uuid**: The unique ID of the player.
* **Returns**: A `Map<String, Double>` where the key is the item ID and the value is the amount stored.

#### `getBackpackWeight(UUID uuid)`

Calculates the total number of items currently inside a player's backpack.

* **uuid**: The unique ID of the player.
* **Returns**: A `double` representing the sum of all item amounts in the backpack.

#### `sellBackpackItems(Player player)`

Triggers a sale of all items currently in the player's backpack, clearing its contents.

* **player**: The player whose backpack items will be sold.

#### `upgradeBackpackAsPlayer(Player player)`

Attempts to upgrade the player's backpack to the next available tier. This method internally handles checking for the next upgrade and deducting the cost from the player's balance.

* **player**: The player who is attempting to upgrade their backpack.

#### `setBackpackUpgrade(UUID uuid, String upgrade)`

Directly sets a player's backpack to a specific upgrade tier, bypassing any cost checks.

* **uuid**: The unique ID of the player.
* **upgrade**: The ID of the target backpack tier (e.g., "2", "3", "vip-pack").

#### `getBackpackUpgrade(UUID uuid)`

Retrieves the ID of the player's current backpack upgrade tier.

* **uuid**: The unique ID of the player.
* **Returns**: A `String` containing the ID of the current backpack tier.

#### `getBackpackNextUpgrade(UUID uuid)`

Determines the next available upgrade tier for a player based on their current one.

* **uuid**: The unique ID of the player.
* **Returns**: A `String` with the ID of the next upgrade tier, or null if the player is at the maximum level.

#### `getBackpackUpgrades()`

Gets a collection of all configured backpack upgrade tier IDs.

* **Returns**: A `Set<String>` containing all available backpack tier IDs from backpacks.yml.

#### `getBackpackUpgradeMultiplier(String upgrade)`

Retrieves the item collection multiplier for a specific backpack tier.

* **upgrade**: The ID of the backpack tier.
* **Returns**: A `double` representing the multiplier (e.g., 0.2 for 20%).

#### `getBackpackUpgradeCost(String upgrade)`

Gets the upgrade cost for a specific backpack tier.

* **upgrade**: The ID of the backpack tier.
* **Returns**: A `double` representing the cost amount.

#### `getBackpackUpgradeCurrency(String upgrade)`

Gets the currency type required to upgrade to a specific backpack tier.

* **upgrade**: The ID of the backpack tier.
* **Returns**: A `String` with the ID of the currency (e.g., "farm-coins").

#### `getBackpackUpgradeSize(String upgrade)`

Retrieves the total storage capacity for a specific backpack tier.

* **upgrade**: The ID of the backpack tier.
* **Returns**: A `double` representing the maximum capacity.