#[cfg(feature = "diff")]

use std::{borrow::Cow, mem::size_of};

#[cfg(feature = "diff")]

use v_frame::{

    frame::Frame,

    prelude::{CastFromPrimitive, ChromaSampling, Pixel},

};

#[cfg(feature = "diff")]

pub fn frame_into_u8<T: Pixel>(frame: &Frame<T>, bit_depth: usize) -> Cow<'_, Frame<u8>> {

    if size_of::<T>() == 1 {

        assert_eq!(bit_depth, 8);

        // SAFETY: We know from the size check that this must be a `Frame<u8>`

        Cow::Borrowed(unsafe { &*(frame as *const Frame<T>).cast::<Frame<u8>>() })

    } else if size_of::<T>() == 2 {

        assert!(bit_depth > 8 && bit_depth <= 16);

        let mut u8_frame: Frame<u8> = Frame::new_with_padding(

            frame.planes[0].cfg.width,

            frame.planes[0].cfg.height,

            match frame.planes[1].cfg.xdec + frame.planes[1].cfg.ydec {

                0 => ChromaSampling::Cs444,

                1 => ChromaSampling::Cs422,

                2 => ChromaSampling::Cs420,

                _ => unreachable!(),

            },

            frame.planes[0].cfg.xpad,

        );

        for i in 0..3 {

            let out_plane = &mut u8_frame.planes[i];

            for (i, o) in frame.planes[i]

                .data_origin()

                .iter()

                .zip(out_plane.data_origin_mut().iter_mut())

            {

                *o = (u16::cast_from(*i) >> (bit_depth - 8usize)) as u8;

            }

        }

        Cow::Owned(u8_frame)

    } else {

        unimplemented!("Bit depths greater than 16 are not currently supported");

    }

}