solana-program-examples/basics/transfer-sol/native/program/src/processor.rs

use borsh::{ BorshDeserialize, BorshSerialize };
use solana_program::{
    account_info::AccountInfo, 
    entrypoint::ProgramResult, 
    pubkey::Pubkey,
};

use crate::instruction::transfer_sol_with_cpi;
use crate::instruction::transfer_sol_with_program;


#[derive(BorshSerialize, BorshDeserialize, Debug)]
pub enum TransferInstruction {
    CpiTransfer(u64),
    ProgramTransfer(u64),
}


pub fn process_instruction(
    program_id: &Pubkey,
    accounts: &[AccountInfo],
    input: &[u8],
) -> ProgramResult {

    let instruction = TransferInstruction::try_from_slice(&input)?;
    match instruction {
        TransferInstruction::CpiTransfer(
            args) => transfer_sol_with_cpi(accounts, args),
            TransferInstruction::ProgramTransfer(
            args) => transfer_sol_with_program(program_id, accounts, args),
    }
}