还款

repay 指令是我们闪电贷系统的后半部分。由于 loan 指令的设计，repay 的逻辑非常简单，因为它只需要：

使用 loan 账户检查所有余额是否已正确偿还。
关闭 loan 账户，因为它不再需要。

所需账户

borrower：请求闪电贷的用户。他们提供创建 loan 账户所需的 lamports。必须是可变的。
loan：用于存储 protocol_token_account 和最终所需 balance 的临时账户。必须是可变的，因为它将在指令结束时关闭。

以下是实现：

rust
pub struct RepayAccounts<'a> {
    pub borrower: &'a AccountInfo,
    pub loan: &'a AccountInfo,
    pub token_accounts: &'a [AccountInfo],
}

impl<'a> TryFrom<&'a [AccountInfo]> for RepayAccounts<'a> {
    type Error = ProgramError;

    fn try_from(accounts: &'a [AccountInfo]) -> Result<Self, Self::Error> {
        let [borrower, loan, token_accounts @ ..] = accounts else {
            return Err(ProgramError::NotEnoughAccountKeys);
        };

        Ok(Self {
            borrower,
            loan,
            token_accounts,
        })
    }
}

token_accounts 字段是一个动态账户数组，表示与借款人贷款相关的协议代币账户。

指令数据

不需要指令数据，因为我们使用 balance 字段在 loan 账户中验证贷款是否已偿还。

指令逻辑

我们首先将账户解析为 RepayAccounts 结构体。

rust
pub struct Repay<'a> {
    pub accounts: RepayAccounts<'a>,
}

impl<'a> TryFrom<&'a [AccountInfo]> for Repay<'a> {
    type Error = ProgramError;

    fn try_from(accounts: &'a [AccountInfo]) -> Result<Self, Self::Error> {
        let accounts = RepayAccounts::try_from(accounts)?;

        Ok(Self { accounts })
    }
}

接下来，我们检查所有贷款是否已偿还。我们通过从 loan 账户中检索贷款数量并逐一迭代来完成此操作。对于每笔贷款，我们验证 protocol_token_account 是否正确，并且其余额是否大于或等于贷款金额。

rust
impl<'a> Repay<'a> {
    pub const DISCRIMINATOR: &'a u8 = &1;

    pub fn process(&mut self) -> ProgramResult {
        let loan_data = self.accounts.loan.try_borrow_data()?;
        let loan_num = loan_data.len() / size_of::<LoanData>();

        if loan_num.ne(&self.accounts.token_accounts.len()) {
            return Err(ProgramError::InvalidAccountData);
        }

        // Process each pair of token accounts (protocol, borrower) with corresponding amounts
        for i in 0..loan_num {
            // Validate that protocol_ata is the same as the one in the loan account
            let protocol_token_account = &self.accounts.token_accounts[i];

            if unsafe { *(loan_data.as_ptr().add(i * size_of::<LoanData>()) as *const [u8; 32]) } != *protocol_token_account.key() {
                return Err(ProgramError::InvalidAccountData);
            }

            // Check if the loan is already repaid
            let balance = get_token_amount(&protocol_token_account.try_borrow_data()?);
            let loan_balance = unsafe { *(loan_data.as_ptr().add(i * size_of::<LoanData>() + size_of::<[u8; 32]>()) as *const u64) };

            if balance < loan_balance {
                return Err(ProgramError::InvalidAccountData);
            }
        }

        //..
    }
}

然后我们可以关闭 loan 账户并回收租金，因为它不再需要：

rust
drop(loan_data);
// Close the loan account and give back the lamports to the borrower
unsafe {
    *self.accounts.borrower.borrow_mut_lamports_unchecked() += *self.accounts.loan.borrow_lamports_unchecked();
    // There is no need to manually zero out lamports in the loan account because it is done in the close_unchecked function
    self.accounts.loan.close_unchecked();
}

如您所见，为了优化和设计的目的，还款并未在此指令中发生。这是因为borrower可以选择在其他指令中偿还代币账户，例如在执行交换操作或从其套利程序中执行一系列CPI时。

Pinocchio 闪电贷

还款

所需账户

指令数据

指令逻辑