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use Buffer;
use BufferRef;
use ToBufferRef;
use wildly_unsafe;

/// The intermediate step from a byte slice to a `BufferRef`.
pub struct SliceBuffer<'data> {
    slice: &'data mut [u8],
    initialized: usize,
}

impl<'d> SliceBuffer<'d> {
    fn new(slice: &'d mut [u8]) -> SliceBuffer<'d> {
        SliceBuffer {
            slice: slice,
            initialized: 0,
        }
    }
    fn buffer<'s>(&'s mut self) -> BufferRef<'d, 's> {
        unsafe {
            // This is unsafe, we now have two unique (mutable) references to
            // the same `Vec`. However, we will only access `self.vec.len`
            // through `self` and only the contents through the `BufferRef`.
            BufferRef::new(wildly_unsafe(self.slice), &mut self.initialized)
        }
    }
}

impl<'d> Buffer<'d> for &'d mut [u8] {
    type Intermediate = SliceBuffer<'d>;
    fn to_to_buffer_ref(self) -> Self::Intermediate {
        SliceBuffer::new(self)
    }
}

impl<'d> ToBufferRef<'d> for SliceBuffer<'d> {
    fn to_buffer_ref<'s>(&'s mut self) -> BufferRef<'d, 's> {
        self.buffer()
    }
}