// Copyright (c) 2024, BlockProject 3D

//

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//

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// are permitted provided that the following conditions are met:

//

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//       this list of conditions and the following disclaimer.

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//       this list of conditions and the following disclaimer in the documentation

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//       may be used to endorse or promote products derived from this software

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// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

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// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

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use std::io::Write;

use std::marker::PhantomData;

use bp3d_proto::message::{FromBytes, Message, WriteTo};

use bp3d_proto::util::ToUsize;

use bp3d_proto::message::Result;

pub struct VarBytes<T>(PhantomData<T>);

impl<'a, T: FromBytes<'a, Output: ToUsize>> FromBytes<'a> for VarBytes<T> {

    type Output = &'a [u8];

    fn from_bytes(slice: &'a [u8]) -> Result<Message<Self::Output>> {

        let msg = T::from_bytes(slice)
?0
;

        let size = msg.size();

        let len = msg.into_inner().to_usize();

        Ok(Message::new(size + len, &slice[size..len + size]))

    }

}

impl<'a, T: WriteTo<Input<'a>: ToUsize>> WriteTo for VarBytes<T> {

    type Input<'b> = &'b [u8];

    fn write_to<W: Write>(input: &Self::Input<'_>, mut out: W) -> Result<()> {

        let len = input.len();

        T::write_to(&T::Input::from_usize(len), &mut out)
?0
;

        out.write_all(&input)
?0
;

        Ok(())

    }

}