kaptn-lang 0.2.4

Kaptn Transfer-Hook Framework
Documentation 
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use solana_program::account_info::{next_account_info, AccountInfo};
use solana_program::entrypoint::ProgramResult;
use solana_program::program_error::ProgramError;
use solana_program::pubkey::Pubkey;
use spl_tlv_account_resolution;
use spl_tlv_account_resolution::account::ExtraAccountMeta;
use spl_tlv_account_resolution::state::ExtraAccountMetaList;
use spl_token_2022::extension::StateWithExtensions;
use spl_token_2022::state::Mint;
use spl_transfer_hook_interface::error::TransferHookError;
use spl_transfer_hook_interface::get_extra_account_metas_address;
use spl_transfer_hook_interface::instruction::ExecuteInstruction;

pub fn process_update_extra_account_meta_list(
    program_id: &Pubkey,
    accounts: &[AccountInfo],
    extra_account_metas: &[ExtraAccountMeta],
) -> ProgramResult {
    let account_info_iter = &mut accounts.iter();

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

    let mint_data = mint_info.try_borrow_data()?;
    let mint = StateWithExtensions::<Mint>::unpack(&mint_data)?;
    let mint_authority = mint
        .base
        .mint_authority
        .ok_or(TransferHookError::MintHasNoMintAuthority)?;

    if !authority_info.is_signer {
        return Err(ProgramError::MissingRequiredSignature);
    }
    if *authority_info.key != mint_authority {
        return Err(TransferHookError::IncorrectMintAuthority.into());
    }

    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 min_account_size = ExtraAccountMetaList::size_of(0)?;
    let original_account_size = extra_account_metas_info.data_len();
    if program_id != extra_account_metas_info.owner || original_account_size < min_account_size {
        return Err(ProgramError::UninitializedAccount);
    }

    let length = extra_account_metas.len();
    let account_size = ExtraAccountMetaList::size_of(length)?;
    if account_size >= original_account_size {
        extra_account_metas_info.realloc(account_size, false)?;
        let mut data = extra_account_metas_info.try_borrow_mut_data()?;
        ExtraAccountMetaList::update::<ExecuteInstruction>(&mut data, extra_account_metas)?;
    } else {
        {
            let mut data = extra_account_metas_info.try_borrow_mut_data()?;
            ExtraAccountMetaList::update::<ExecuteInstruction>(&mut data, extra_account_metas)?;
        }
        extra_account_metas_info.realloc(account_size, false)?;
    }

    Ok(())
}