top_up_ephemeral_balance.rs

use borsh::BorshDeserialize;
use solana_program::{
    account_info::AccountInfo, entrypoint::ProgramResult, program::invoke,
    program_error::ProgramError, pubkey::Pubkey, system_instruction::transfer,
    system_program,
};

use crate::{
    args::TopUpEphemeralBalanceArgs,
    ephemeral_balance_seeds_from_payer,
    processor::utils::{
        loaders::{load_pda, load_program, load_signer},
        pda::create_pda,
    },
};

/// Tops up the ephemeral balance account.
///
/// Accounts:
///
/// 0: `[writable]` payer account who funds the topup
/// 1: `[]` pubkey account that the ephemeral balance PDA was derived from
/// 2: `[writable]` ephemeral balance account to top up
/// 3: `[]` system program
///
/// Requirements:
///
/// - the payer account has enough lamports to fund the transfer
///
/// Steps:
///
/// 1. Create the ephemeral balance PDA if it does not exist
/// 2. Transfer lamports from payer to ephemeral PDA
pub fn process_top_up_ephemeral_balance(
    _program_id: &Pubkey,
    accounts: &[AccountInfo],
    data: &[u8],
) -> ProgramResult {
    // Parse args.
    let args = TopUpEphemeralBalanceArgs::try_from_slice(data)?;

    // Load Accounts
    let [payer, pubkey, ephemeral_balance_account, system_program] = accounts
    else {
        return Err(ProgramError::NotEnoughAccountKeys);
    };

    load_signer(payer, "payer")?;
    load_program(system_program, system_program::id(), "system program")?;

    let bump_ephemeral_balance = load_pda(
        ephemeral_balance_account,
        ephemeral_balance_seeds_from_payer!(pubkey.key, args.index),
        &crate::id(),
        true,
        "ephemeral balance",
    )?;

    // Create the ephemeral balance PDA if it does not exist
    if ephemeral_balance_account.owner.eq(&system_program::id()) {
        create_pda(
            ephemeral_balance_account,
            &system_program::id(),
            0,
            ephemeral_balance_seeds_from_payer!(pubkey.key, args.index),
            bump_ephemeral_balance,
            system_program,
            payer,
        )?;
    }

    // Transfer lamports from payer to ephemeral PDA (with a system program call)
    if args.amount > 0 {
        let transfer_instruction =
            transfer(payer.key, ephemeral_balance_account.key, args.amount);
        invoke(
            &transfer_instruction,
            &[
                payer.clone(),
                ephemeral_balance_account.clone(),
                system_program.clone(),
            ],
        )?;
    }

    Ok(())
}