kaptn-syn 0.3.0

Syntax parsing and code generation for Kaptn Transfer-Hook Framework
Documentation 
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use crate::TransferHookInput;
use quote::quote;

pub fn generate(_program: &TransferHookInput) -> proc_macro2::TokenStream {
    quote! {
        pub fn process_execute<'info, E: ExtraMetas<'info>>(
            program_id: &Pubkey,
            accounts: &[AccountInfo<'info>],
            amount: u64,
            process_transfer: fn(TransferContext<'_, 'info, E>) -> ProgramResult,
        ) -> ProgramResult {
            let account_info_iter = &mut accounts.iter();

            let source_account_info = next_account_info(account_info_iter)?;
            let mint_info = next_account_info(account_info_iter)?;
            let destination_account_info = next_account_info(account_info_iter)?;
            let authority_info = next_account_info(account_info_iter)?;
            let extra_account_metas_info = next_account_info(account_info_iter)?;

            check_token_account_is_transferring(source_account_info)?;
            check_token_account_is_transferring(destination_account_info)?;

            let expected_validation_address = get_extra_account_metas_address(mint_info.key, program_id);
            if expected_validation_address != *extra_account_metas_info.key {
                return Err(ProgramError::InvalidSeeds);
            }

            let data = extra_account_metas_info.try_borrow_data()?;

            ExtraAccountMetaList::check_account_infos::<ExecuteInstruction>(
                accounts,
                &TransferHookInstruction::Execute { amount }.pack(),
                program_id,
                &data,
            )?;

            let extra_metas = E::from_accounts(accounts)?;

            let ctx = TransferContext {
                program_id,
                source_account: source_account_info,
                mint: mint_info,
                destination_account: destination_account_info,
                authority: authority_info,
                extra_account_metas: extra_account_metas_info,
                amount,
                extra_metas,
            };

            process_transfer(ctx)
        }

        fn check_token_account_is_transferring(account_info: &AccountInfo) -> Result<(), ProgramError> {
            let account_data = account_info.try_borrow_data()?;
            let token_account = StateWithExtensions::<Account>::unpack(&account_data)?;
            let extension = token_account.get_extension::<TransferHookAccount>()?;
            if bool::from(extension.transferring) {
                Ok(())
            } else {
                Err(TransferHookError::ProgramCalledOutsideOfTransfer.into())
            }
        }

    }
}