use std::fs::File;
use std::io::{Cursor, Read, Seek};

/// Trait used to get a hold to file handler or to the underlying bytes
/// without performing a Read.
pub trait MmapBytesReader: Read + Seek + Send + Sync {
    fn to_file(&self) -> Option<&File> {
        None
    }

    fn to_bytes(&self) -> Option<&[u8]> {
        None
    }
}

impl MmapBytesReader for File {
    fn to_file(&self) -> Option<&File> {
        Some(self)
    }
}

impl<T> MmapBytesReader for Cursor<T>
where
    T: AsRef<[u8]> + Send + Sync,
{
    fn to_bytes(&self) -> Option<&[u8]> {
        Some(self.get_ref().as_ref())
    }
}

impl<T: MmapBytesReader + ?Sized> MmapBytesReader for Box<T> {
    fn to_file(&self) -> Option<&File> {
        T::to_file(self)
    }

    fn to_bytes(&self) -> Option<&[u8]> {
        T::to_bytes(self)
    }
}
