The Pair Contract

The SoroswapPair Contract implements the token interface (hence, it has the same functions that any Stellar Asset Contract) and it also has the specific functions for a liquidity pool to exist:

In the next chapter we will see, step-by-step how to experiment with this contract using the soroban CLI.

Here is the contract interface:

pub trait SoroswapPairTrait{
    // Sets the token contract addresses for this pool
    fn initialize_pair(e: Env, factory: Address, token_a: BytesN<32>, token_b: BytesN<32>);

    // Returns the token contract address for the pool share token
    fn share_id(e: Env) -> BytesN<32>;

    fn token_0(e: Env) -> BytesN<32>;
    fn token_1(e: Env) -> BytesN<32>;

    // Deposits token_a and token_b. Also mints pool shares for the "to" Identifier. The amount minted
    // is determined based on the difference between the reserves stored by this contract, and
    // the actual balance of token_a and token_b for this contract.
    fn deposit(e: Env, to: Address, desired_a: i128, min_a: i128, desired_b: i128, min_b: i128);

    // If "buy_a" is true, the swap will buy token_a and sell token_b. This is flipped if "buy_a" is false.
    // "out" is the amount being bought, with in_max being a safety to make sure you receive at least that amount.
    // swap will transfer the selling token "to" to this contract, and then the contract will transfer the buying token to "to".
    fn swap(e: Env, to: Address, buy_a: bool, out: i128, in_max: i128);

    // transfers share_amount of pool share tokens to this contract, burns all pools share tokens in this contracts, and sends the
    // corresponding amount of token_a and token_b to "to".
    // Returns amount of both tokens withdrawn
    fn withdraw(e: Env, to: Address, share_amount: i128, min_a: i128, min_b: i128) -> (i128, i128);

    fn get_rsrvs(e: Env) -> (i128, i128);

    fn my_balance(e: Env, id: Address) -> i128;

    fn factory(e: Env) -> Address;
}

pub trait TokenTrait {
    fn initialize(e: Env, admin: Address, decimal: u32, name: Bytes, symbol: Bytes);

    fn allowance(e: Env, from: Address, spender: Address) -> i128;

    fn incr_allow(e: Env, from: Address, spender: Address, amount: i128);

    fn decr_allow(e: Env, from: Address, spender: Address, amount: i128);

    fn balance(e: Env, id: Address) -> i128;

    fn spendable(e: Env, id: Address) -> i128;

    fn authorized(e: Env, id: Address) -> bool;

    fn xfer(e: Env, from: Address, to: Address, amount: i128);

    fn xfer_from(e: Env, spender: Address, from: Address, to: Address, amount: i128);

    fn burn(e: Env, from: Address, amount: i128);

    fn burn_from(e: Env, spender: Address, from: Address, amount: i128);

    fn clawback(e: Env, admin: Address, from: Address, amount: i128);

    fn set_auth(e: Env, admin: Address, id: Address, authorize: bool);

    fn mint(e: Env, admin: Address, to: Address, amount: i128);

    fn set_admin(e: Env, admin: Address, new_admin: Address);

    fn decimals(e: Env) -> u32;

    fn name(e: Env) -> Bytes;

    fn symbol(e: Env) -> Bytes;
}