optic-render 0.0.1

use optic_core::ATTRType;

/// Trait for types that can be used as vertex or instance attribute data.
///
/// Implemented for `i8`, `u8`, `i16`, `u16`, `i32`, `u32`, `f32`, `f64` and
/// their fixed-size arrays `[T; 2]`, `[T; 3]`, `[T; 4]`.
///
/// # Constants
///
/// * [`DataType::ATTR_FORMAT`] — the GL attribute type enum
/// * [`DataType::BYTE_COUNT`] — size of one scalar element in bytes
/// * [`DataType::ELEM_COUNT`] — number of scalar elements (1 for scalars, N for arrays)
///
/// # Example
///
/// ```
/// use optic_render::asset::attr::DataType;
///
/// assert_eq!(<f32 as DataType>::BYTE_COUNT, 4);
/// assert_eq!(<[f32; 3] as DataType>::ELEM_COUNT, 3);
/// ```
pub trait DataType {
    const ATTR_FORMAT: ATTRType;
    const BYTE_COUNT: usize;
    const ELEM_COUNT: usize;
    fn u8ify(&self) -> Vec<u8>;
}

macro_rules! u8ify_impl {
    ([$t:ty; $s:literal]) => {
        fn u8ify(&self) -> Vec<u8> {
            let mut vec = Vec::new();
            for elem in self.iter() {
                vec.extend_from_slice(&elem.to_ne_bytes());
            }
            vec
        }
    };
    ($t:ty) => {
        fn u8ify(&self) -> Vec<u8> {
            self.to_ne_bytes().to_vec()
        }
    };
}

macro_rules! datatype {
    ($type:ty, $attr_format:expr, $byte_count:expr) => {
        impl DataType for $type {
            const ATTR_FORMAT: ATTRType = $attr_format;
            const BYTE_COUNT: usize = $byte_count;
            const ELEM_COUNT: usize = 1;
            u8ify_impl!($type);
        }

        impl DataType for [$type; 2] {
            const ATTR_FORMAT: ATTRType = $attr_format;
            const BYTE_COUNT: usize = $byte_count;
            const ELEM_COUNT: usize = 2;
            u8ify_impl!([$type; 2]);
        }

        impl DataType for [$type; 3] {
            const ATTR_FORMAT: ATTRType = $attr_format;
            const BYTE_COUNT: usize = $byte_count;
            const ELEM_COUNT: usize = 3;
            u8ify_impl!([$type; 3]);
        }

        impl DataType for [$type; 4] {
            const ATTR_FORMAT: ATTRType = $attr_format;
            const BYTE_COUNT: usize = $byte_count;
            const ELEM_COUNT: usize = 4;
            u8ify_impl!([$type; 4]);
        }
    };
}

datatype!(i8, ATTRType::I8, 1);
datatype!(u8, ATTRType::U8, 1);
datatype!(i16, ATTRType::I16, 2);
datatype!(u16, ATTRType::U16, 2);
datatype!(i32, ATTRType::I32, 4);
datatype!(u32, ATTRType::U32, 4);
datatype!(f32, ATTRType::F32, 4);
datatype!(f64, ATTRType::F64, 8);

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn f32_scalar_u8ify() {
        let v: f32 = 1.0;
        let bytes = v.u8ify();
        assert_eq!(bytes.len(), 4);
    }

    #[test]
    fn f32_array2_u8ify() {
        let v: [f32; 2] = [1.0, 2.0];
        let bytes = v.u8ify();
        assert_eq!(bytes.len(), 8);
    }

    #[test]
    fn f32_array3_u8ify() {
        let v: [f32; 3] = [1.0, 2.0, 3.0];
        let bytes = v.u8ify();
        assert_eq!(bytes.len(), 12);
    }

    #[test]
    fn f32_array4_u8ify() {
        let v: [f32; 4] = [1.0, 2.0, 3.0, 4.0];
        let bytes = v.u8ify();
        assert_eq!(bytes.len(), 16);
    }

    #[test]
    fn u32_scalar_u8ify() {
        let v: u32 = 0x12345678;
        let bytes = v.u8ify();
        assert_eq!(bytes.len(), 4);
    }

    #[test]
    fn u32_array2_u8ify() {
        let v: [u32; 2] = [1, 2];
        let bytes = v.u8ify();
        assert_eq!(bytes.len(), 8);
    }

    #[test]
    fn u8_scalar_u8ify() {
        let v: u8 = 255;
        let bytes = v.u8ify();
        assert_eq!(bytes.len(), 1);
    }

    #[test]
    fn i32_scalar_u8ify() {
        let v: i32 = -42;
        let bytes = v.u8ify();
        assert_eq!(bytes.len(), 4);
    }

    #[test]
    fn f64_scalar_u8ify() {
        let v: f64 = 3.14159;
        let bytes = v.u8ify();
        assert_eq!(bytes.len(), 8);
    }

    #[test]
    fn const_byte_count() {
        assert_eq!(<u8 as DataType>::BYTE_COUNT, 1);
        assert_eq!(<i8 as DataType>::BYTE_COUNT, 1);
        assert_eq!(<u16 as DataType>::BYTE_COUNT, 2);
        assert_eq!(<i16 as DataType>::BYTE_COUNT, 2);
        assert_eq!(<u32 as DataType>::BYTE_COUNT, 4);
        assert_eq!(<i32 as DataType>::BYTE_COUNT, 4);
        assert_eq!(<f32 as DataType>::BYTE_COUNT, 4);
        assert_eq!(<f64 as DataType>::BYTE_COUNT, 8);
    }

    #[test]
    fn const_elem_count() {
        assert_eq!(<[f32; 3] as DataType>::ELEM_COUNT, 3);
        assert_eq!(<[f32; 2] as DataType>::ELEM_COUNT, 2);
        assert_eq!(<[f32; 4] as DataType>::ELEM_COUNT, 4);
        assert_eq!(<u32 as DataType>::ELEM_COUNT, 1);
    }
}