> For the complete documentation index, see [llms.txt](https://docs.satay.finance/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.satay.finance/technical-overview/wrapper-module-legacy.md).

# Wrapper Module (Legacy)

## Overview

The `satay::wrapper` module manages the conversion of the legacy coin standard to-and-fro the fungible assets standard within the Satay protocol. It handles the creation, initialization, and management of wrapped coins by providing functions to wrap and unwrap them.

## Structs

### Wrapper

The `Wrapper` struct stores a `SignerCapability` for managing wrapped coins and a `SmartTable` that maps wrapped coin metadata to their coin type names.

```rust
struct Wrapper has key {
    signer_cap: SignerCapability,
    wrapped_coins: SmartTable<Object<Metadata>, String>
}
```

## Constants

* **WRAPPER\_SEED**: `vector<u8> = b"000000000Wrapper"` – The seed used to create the wrapper resource account.
* **EWRAPPER\_ALREADY\_INITIALIZED**: `u64 = 0` – Error indicating that the wrapper has already been initialized.
* **EWRAPPER\_NOT\_INITIALIZED**: `u64 = 1` – Error indicating that the wrapper has not been initialized.
* **EMETADATA\_ALREADY\_EXISTS**: `u64 = 2` – Error indicating that the metadata for the wrapped asset already exists.

## Public Functions

1. **Module Initialization**
   * `init_module(_: &signer)`: Initializes the wrapper module by creating a new wrapper account. It generates a new signer and a `Wrapper` resource, storing wrapped coins in a `SmartTable`.
2. **Asset Initialization and Management**
   * `initialize_wrapped_asset<CoinType>(): Object<Metadata> acquires Wrapper`: Initializes a new wrapped asset for the given `CoinType`. It creates metadata for the wrapped asset and stores it in the wrapper's `SmartTable`. If the metadata already exists, it raises `EMETADATA_ALREADY_EXISTS`.
   * `get_wrapped_asset_metadata<CoinType>(): Object<Metadata>`: Retrieves the metadata for a wrapped asset of the given `CoinType`.
   * `get_wrapped_coin_type(metadata: Object<Metadata>): String acquires Wrapper`: Retrieves the coin type name of the given wrapped asset from the wrapper's `SmartTable`.
   * `is_wrapped_asset(metadata: Object<Metadata>): bool acquires Wrapper`: Checks whether the given metadata represents a wrapped asset.
3. **Address Management**
   * `get_wrapper_address(): address`: Computes and returns the address of the wrapper resource.
   * `compute_wrap_address<CoinType>(): address`: Computes the address of the wrapped asset for the given `CoinType`.
4. **Asset Wrapping and Unwrapping**
   * `wrap<CoinType>(coin: Coin<CoinType>): FungibleAsset acquires Wrapper`: Wraps the given `CoinType` into a fungible asset. It initializes the wrapped asset if it doesn't exist, deposits the coin into the wrapper, and mints the corresponding fungible asset.
   * `unwrap<CoinType>(asset: FungibleAsset): Coin<CoinType> acquires Wrapper`: Unwraps a fungible asset into the corresponding `CoinType`. It burns the fungible asset and withdraws the equivalent amount of the original coin.

## **Helper Functions**

* `borrow_wrapper()`: Returns a reference to the `Wrapper` resource.
* `borrow_wrapper_mut()`: Returns a mutable reference to the `Wrapper` resource.

## View Functions

* `has_wrapped_asset<CoinType>(): bool`: Checks if the wrapped asset for the given `CoinType` exists.
* `get_wrapped_asset_metadata<CoinType>(): Object<Metadata>`: Retrieves the metadata for the wrapped asset corresponding to `CoinType`.