use error::{ErrorKind, Result};

/// A trait for stopping serialization and deserialization when a certain limit has been reached.

pub trait SizeLimit {

    /// Tells the SizeLimit that a certain number of bytes has been

    /// read or written.  Returns Err if the limit has been exceeded.

    fn add(&mut self, n: u64) -> Result<()>;

    /// Returns the hard limit (if one exists)

    fn limit(&self) -> Option<u64>;

}

/// A SizeLimit that restricts serialized or deserialized messages from

/// exceeding a certain byte length.

#[derive(Copy, Clone)]

pub struct Bounded(pub u64);

/// A SizeLimit without a limit!

/// Use this if you don't care about the size of encoded or decoded messages.

#[derive(Copy, Clone)]

pub struct Infinite;

impl SizeLimit for Bounded {

    #[inline(always)]

    fn add(&mut self, n: u64) -> Result<()> {

        if self.0 >= n {

            self.0 -= n;

            Ok(())

        } else {

            Err(Box::new(ErrorKind::SizeLimit))

        }

    }

    #[inline(always)]

    fn limit(&self) -> Option<u64> {

        Some(self.0)

    }

}

impl SizeLimit for Infinite {

    #[inline(always)]

    fn add(&mut self, _: u64) -> Result<()> {

        Ok(())

    }

    #[inline(always)]

    fn limit(&self) -> Option<u64> {

        None

    }

}