> ## Documentation Index
> Fetch the complete documentation index at: https://docs.soroswap.finance/llms.txt
> Use this file to discover all available pages before exploring further.

# Adapter Trait

> AdapterTrait, the interface every protocol adapter implements so the aggregator can route through it.

Every adapter implements `AdapterTrait`, defined in
[`contracts/adapters/interface`](https://github.com/soroswap/aggregator/tree/main/contracts/adapters/interface).
That single interface is what lets the aggregator treat Soroswap, Phoenix, Aqua and Comet
the same way, and it is all you need to implement to add a protocol.

## Interface

```rust theme={null}
pub trait AdapterTrait {
    fn initialize(
        e: Env,
        protocol_id: String,
        protocol_address: Address,
    ) -> Result<(), AdapterError>;

    /// Swaps an exact amount of input tokens for as many output tokens as possible,
    /// along the route given by `path`.
    fn swap_exact_tokens_for_tokens(
        env: Env,
        amount_in: i128,
        amount_out_min: i128,
        path: Vec<Address>,
        to: Address,
        deadline: u64,
        bytes: Option<Vec<BytesN<32>>>,
    ) -> Result<Vec<i128>, AdapterError>;

    /// Swaps as few input tokens as possible for an exact amount of output token.
    fn swap_tokens_for_exact_tokens(
        e: Env,
        amount_out: i128,
        amount_in_max: i128,
        path: Vec<Address>,
        to: Address,
        deadline: u64,
        bytes: Option<Vec<BytesN<32>>>,
    ) -> Result<Vec<i128>, AdapterError>;

    /*  *** Read only functions: *** */
    fn get_protocol_id(e: &Env) -> Result<String, AdapterError>;
    fn get_protocol_address(e: &Env) -> Result<Address, AdapterError>;
}
```

## Notes on the parameters

`path` is the route through the underlying protocol. The first element is the input
token, the last is the output token, and anything between them is an intermediate hop to
trade through when no direct pair exists.

`bytes` is the escape hatch for protocols that need something the common interface does
not carry. Aqua uses it for pool hashes, which is why `AdapterError` has
`MissingPoolHashes` and `WrongPoolHashesLength`. Adapters that need nothing extra take
`None`.

Both swap functions return the amounts at each step of the route, not just the final
amount.

## Errors

| Code | Variant                   | Meaning                                            |
| ---- | ------------------------- | -------------------------------------------------- |
| 401  | `NotInitialized`          | The adapter has not been initialized.              |
| 402  | `AlreadyInitialized`      | `initialize` was called twice.                     |
| 403  | `NegativeNotAllowed`      | An amount was negative.                            |
| 404  | `ProtocolAddressNotFound` | No protocol address is stored.                     |
| 405  | `DeadlineExpired`         | The ledger passed `deadline`.                      |
| 406  | `MissingPoolHashes`       | Aqua: `bytes` was required and not supplied.       |
| 407  | `WrongMinimumPathLength`  | `path` is shorter than the protocol needs.         |
| 408  | `WrongPoolHashesLength`   | Aqua: the pool hash count does not match the path. |