Swapline

The Swapline is a more straightforward way to get synthetic tokens. It exists to keep the price of each of the synthetic tokens close to their original counterparts. Moreover, without it, amount of synthetic tokens in circulation would be smaller than debt, due to interest rate. The Swapline provides a simple way to counteract that.

Structure of Swapline#

pub struct Swapline {
    pub synthetic: Pubkey,
    pub collateral: Pubkey,
    pub fee: Decimal,
    pub accumulated_fee: Decimal,
    pub balance: Decimal,
    pub limit: Decimal,
    pub collateral_reserve: Pubkey,
    pub halted: bool,
    pub bump: u8,
}

synthetic - address of a synthetic token
collateral - address of a collateral token
fee - percentage of every swap taken as a fee
accumulated_fee - total amount of the fee. Can be withdrawn by admin
balance - amount of tokens in reserve
limit - limit of synthetic tokens that can be minted
collateral_reserve - account where collateral tokens are deposited (different from both debt pool and vault counterparts)
halted - swapline can be halted independently of rest of exchange (but halt of exchange affects it too)
bump - seed used to ensure the generated address doesn't collide with any other existing one

Swapping tokens#

Tokens can be swapped from collateral to synthetic as long as the total swapped amount is below the swapline limit. The appropriate function is defined here.

They can also be swapped back from synthetic to collateral, as long as there are enough tokens in collateral_reserve (balance). The method is defined here.

As both of these functions are so similar, they both take amount (u64) and the same struct:

pub struct UseSwapline<'info> {
    pub state: Loader<'info, State>,
    pub swapline: Loader<'info, Swapline>,
    pub synthetic: Info<'info, anchor_spl::token::Mint>,
    pub collateral: Info<'info, anchor_spl::token::Mint>,
    pub user_collateral_account: Account<'info, TokenAccount>,
    pub user_synthetic_account: Account<'info, TokenAccount>,
    pub assets_list: Loader<'info, AssetsList>,
    pub collateral_reserve: Account<'info, TokenAccount>,
    pub signer: AccountInfo<'info>,
    pub exchange_authority: AccountInfo<'info>,
    pub token_program: AccountInfo<'info>,
}

state - account with data of the program
swapline - structure with data of the exchange
synthetic - address of the synthetic token
collateral - address of the collateral token
user_collateral_account - user account with collateral tokens
user_synthetic_account - user account with synthetic tokens
assets_list - list of assets structured as this
collateral_reserve - account with collateral tokens
signer - owner of the user accounts with tokens
exchange_authority - pubkey of the exchange program
token_program - address of Solana's Token Program