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use super::traits::{Name, ParseBytes};
use crate::{
  field_parsing_error, impl_name,
  result::{SQLiteError, SQLiteResult},
};

use core::ops::Deref;

/// # Reserved bytes per page (1 Byte)
///
///  SQLite has the ability to set aside a small number of extra bytes at the
/// end of every page for use by extensions. These extra bytes are used, for
/// example, by the SQLite Encryption Extension to store a nonce and/or
/// cryptographic checksum associated with each page. The "reserved space" size
/// in the 1-byte integer at offset 20 is the number of bytes of space at the
/// end of each page to reserve for extensions. **This value is usually 0.** *The
/// value can be odd.*
///
///  The **"usable size"** of a database page is the page size specified by the
/// 2-byte integer at offset 16 in the header less the "reserved" space size
/// recorded in the 1-byte integer at offset 20 in the header. The usable size
/// of a page might be an odd number.
///
/// However, *the usable size is not allowed to be less than `480`*. In other words, if the page size is 512, then the
/// reserved space size cannot exceed 32.
#[derive(Debug)]
pub struct ReservedBytesPerPage(u8);

impl Deref for ReservedBytesPerPage {
  type Target = u8;

  fn deref(&self) -> &Self::Target {
    &self.0
  }
}

impl_name! {ReservedBytesPerPage}

impl ParseBytes for ReservedBytesPerPage {
  const LENGTH_BYTES: usize = 1;

  fn parsing_handler(bytes: &[u8]) -> SQLiteResult<Self> {
    let reserved_bytes_per_page =
      *bytes.first().ok_or(field_parsing_error! {Self::NAME})?;

    Ok(Self(reserved_bytes_per_page))
  }
}