use anchor_lang::prelude::Error;
use bytemuck::{bytes_of, cast_slice_mut, from_bytes_mut, Contiguous, Pod};

use solana_program::account_info::AccountInfo;
use solana_program::program_error::ProgramError;
use solana_program::pubkey::Pubkey;
use std::cell::RefMut;
use std::mem::size_of;

#[inline]
pub fn remove_slop_mut<T: Pod>(bytes: &mut [u8]) -> &mut [T] {
    let slop = bytes.len() % size_of::<T>();
    let new_len = bytes.len() - slop;
    cast_slice_mut(&mut bytes[..new_len])
}

pub fn strip_header_mut<'a, H: Pod, D: Pod>(
    account: &'a AccountInfo,
) -> Result<(RefMut<'a, H>, RefMut<'a, [D]>), Error> {
    Ok(RefMut::map_split(account.try_borrow_mut_data()?, |data| {
        let (header_bytes, inner_bytes) = data.split_at_mut(size_of::<H>());
        (from_bytes_mut(header_bytes), remove_slop_mut(inner_bytes))
    }))
}