還款
repay 指令是我們閃電貸系統的第二部分。由於 loan 指令的設計，repay 的邏輯相對簡單，因為它只需要：
使用
loan帳戶檢查所有餘額是否已正確償還。關閉
loan帳戶，因為它已不再需要。
所需帳戶
borrower：請求閃電貸的用戶。他們提供建立loan帳戶所需的 lamports。必須是可變的。loan：用於存儲protocol_token_account和最終所需balance的臨時帳戶。必須是可變的，因為它將在指令結束時被關閉。
以下是實現：
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 欄位是一個動態帳戶數組，表示與借款人貸款相關的協議代幣帳戶。
指令數據
不需要指令數據，因為我們使用 balance 欄位在 loan 帳戶中驗證貸款是否已償還。
指令邏輯
我們首先將帳戶解析為 RepayAccounts 結構。
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 })
}
}
接下來，我們檢查所有貸款是否已償還。我們通過從 loan 帳戶中檢索貸款數量並逐一迭代來完成此操作。對於每筆貸款，我們驗證 protocol_token_account 是否正確，並且其餘額是否大於或等於貸款金額。
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);
}
}
//..
}
}然後，我們可以關閉 loan 帳戶並回收租金，因為它已不再需要：
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();
}