draco-oxide 0.1.0-alpha.5

use serde::ser::SerializeSeq;
use serde::Serialize;
use std::{mem, ptr};

use crate::core::attribute::ComponentDataType;
use crate::core::shared::Vector;
use crate::core::shared::{AttributeValueIdx, DataValue};

use super::RawBuffer;

pub(crate) struct AttributeBuffer {
    /// Contains the data of the attribute.
    data: RawBuffer,

    /// The number of values of the attribute.
    len: usize,

    /// pointer to the last element.
    #[allow(unused)]
    last: *mut u8,

    /// component type of the attribute.
    component_type: ComponentDataType,

    num_components: usize,
}

impl AttributeBuffer {
    pub(crate) fn new(component_type: ComponentDataType, num_components: usize) -> Self {
        let data = RawBuffer::with_capacity(0);
        let len = 0;
        let last = unsafe {
            data.as_ptr()
                .add(len * component_type.size() * num_components)
        };

        Self {
            data,
            len,
            last,
            component_type,
            num_components,
        }
    }

    fn as_ptr(&self) -> *mut u8 {
        self.data.as_ptr()
    }

    pub(crate) fn get<Data, const N: usize>(&self, idx: AttributeValueIdx) -> Data
    where
        Data: Vector<N>,
        Data::Component: DataValue,
    {
        let idx_usize = usize::from(idx);
        assert!(
            size_of::<Data>() == self.component_type.size() * self.num_components,
            "Cannot read from buffer: Trying to read data of size {}, but the buffer stores the elements of size {} with {} components", 
            size_of::<Data>(), self.component_type.size(), self.num_components
        );
        assert!(idx_usize < self.len, "Index out of bounds: The index {} is out of bounds for the attribute buffer with length {}", idx_usize, self.len);
        // just checked the condition
        unsafe { self.get_unchecked::<Data, N>(idx) }
    }

    /// # Safety:
    /// Two checks are ignored in this function:
    /// (1) 'std::mem::size_of::<Data>()==component.size() * num_components', and
    /// (2) idx < self.len
    pub(crate) unsafe fn get_unchecked<Data, const N: usize>(&self, idx: AttributeValueIdx) -> Data
    where
        Data: Vector<N>,
        Data::Component: DataValue,
    {
        let idx = usize::from(idx);
        debug_assert!(
            size_of::<Data>() == self.component_type.size() * self.num_components,
            "Cannot read from buffer: Trying to read {}, but the buffer stores the elements of type {} with {} components", 
            size_of::<Data>(), self.component_type.size(), self.num_components
        );
        debug_assert!(idx < self.len, "Index out of bounds: The index {} is out of bounds for the attribute buffer with length {}", idx, self.len);
        let size = mem::size_of::<Data>();
        let ptr = unsafe { self.as_ptr().add(size * idx) };
        // Safety: upheld
        ptr::read(ptr as *const Data)
    }

    pub(crate) fn get_component_type(&self) -> ComponentDataType {
        self.component_type
    }

    pub(crate) fn set_component_type(&mut self, component_type: ComponentDataType) {
        self.component_type = component_type;
    }

    pub(crate) fn set_num_components(&mut self, num_components: usize) {
        self.num_components = num_components;
    }

    pub(crate) fn get_num_components(&self) -> usize {
        self.num_components
    }

    #[allow(unused)]
    pub(crate) fn push<Data, const N: usize>(&mut self, data: Data)
    where
        Data: Vector<N>,
        Data::Component: DataValue,
    {
        assert_eq!(
            Data::Component::get_dyn(),
            self.component_type,
            "Data type mismatch: Cannot push data of type {:?} into attribute buffer of type {:?}",
            Data::Component::get_dyn(),
            self.component_type
        );
        assert!(
            N == self.num_components,
            "Number of components mismatch: Cannot push data with {} components into attribute buffer with {} components",
            N, self.num_components
        );
        unsafe {
            self.push_type_unchecked(data);
        }
    }

    /// pushes a value into the buffer without checking the type and the number of components.
    /// # Safety
    /// This function is unsafe because it does not check the type and the number of components of the data.
    pub(crate) unsafe fn push_type_unchecked<Data, const N: usize>(&mut self, data: Data)
    where
        Data: Vector<N>,
        Data::Component: DataValue,
    {
        debug_assert_eq!(
            Data::Component::get_dyn(), self.component_type,
            "Unsafe Condition Failed: Data type mismatch: Cannot push data of type {:?} into attribute buffer of type {:?}", 
            Data::Component::get_dyn(), self.component_type
        );
        debug_assert!(
            N == self.num_components,
            "Unsafe Condition Failed: Number of components mismatch: Cannot push data with {} components into attribute buffer with {} components",
            N, self.num_components
        );

        self.len += 1;
        if self.len * size_of::<Data>() > self.data.cap {
            self.data.double();
        }

        ptr::write(self.last as *mut Data, data);
    }

    #[inline(always)]
    /// Returns the number of values of the attribute.
    pub fn len(&self) -> usize {
        self.len
    }

    #[inline]
    /// Returns a slice of all the values in the buffer casted to the static type `Data`.
    /// # Safety
    /// This function assumes that the buffer's data is properly aligned and matches the type `Data`.
    pub(crate) unsafe fn as_slice<Data>(&self) -> &[Data] {
        debug_assert!(
            mem::size_of::<Data>() == self.component_type.size() * self.num_components,
            "Cannot create slice: Trying to cast to data of size {}, but the buffer stores elements of type {}D vector of {:?}, which has size {}",
            mem::size_of::<Data>(),
            self.num_components,
            self.component_type,
            self.component_type.size(),
        );

        std::slice::from_raw_parts(self.as_ptr() as *const Data, self.len)
    }

    #[inline]
    /// Returns the mutable slice of all the values in the buffer casted to the static type `Data`.
    /// # Safety
    /// This function assumes that the buffer's data is properly aligned and matches the type `Data`.
    pub(crate) unsafe fn as_slice_mut<Data>(&mut self) -> &mut [Data] {
        debug_assert!(
            mem::size_of::<Data>() == self.component_type.size() * self.num_components,
            "Cannot create slice: Trying to cast to data of size {}, but the buffer stores elements of type {}D vector of {:?}, which has size {}",
            mem::size_of::<Data>(),
            self.num_components,
            self.component_type,
            self.component_type.size(),
        );

        std::slice::from_raw_parts_mut(self.as_ptr() as *mut Data, self.len)
    }

    #[allow(unused)]
    pub unsafe fn into_vec<Data, const N: usize>(self) -> Vec<Data>
    where
        Data: Vector<N>,
    {
        assert_eq!(
            Data::Component::get_dyn(),
            self.component_type,
            "Data type mismatch: Cannot push data of type {:?} into attribute buffer of type {:?}",
            Data::Component::get_dyn(),
            self.component_type
        );
        assert!(
            N == self.num_components,
            "Number of components mismatch: Cannot push data with {} components into attribute buffer with {} components",
            N, self.num_components
        );

        self.into_vec_unchecked()
    }

    pub unsafe fn into_vec_unchecked<Data, const N: usize>(self) -> Vec<Data>
    where
        Data: Vector<N>,
    {
        debug_assert_eq!(
            Data::Component::get_dyn(),
            self.component_type,
            "Data type mismatch: Cannot push data of type {:?} into attribute buffer of type {:?}",
            Data::Component::get_dyn(),
            self.component_type
        );
        debug_assert!(
            N == self.num_components,
            "Number of components mismatch: Cannot push data with {} components into attribute buffer with {} components",
            N, self.num_components
        );

        unsafe {
            let slice = self.as_slice::<Data>();
            Vec::from_raw_parts(slice.as_ptr() as *mut Data, self.len, self.len)
        }
    }

    #[inline]
    /// Returns a slice of all the values in the buffer casted to the static type `u8`.
    pub fn as_slice_u8(&self) -> &[u8] {
        unsafe {
            std::slice::from_raw_parts(
                self.as_ptr(),
                self.len * self.num_components * self.component_type.size(),
            )
        }
    }

    /// #Safety
    /// This function assumes that the permutation is welll-defined in the sense that
    /// (1) it has the same length as the buffer,
    /// (2) its elements are distinct.
    pub unsafe fn permute_unchecked(&mut self, permutation: &[usize]) {
        debug_assert_eq!(
            self.len,
            permutation.len(),
            "Permutation length does not match the buffer length"
        );
        debug_assert!(
            {
                let mut p = permutation.to_vec();
                p.sort();
                p.into_iter().enumerate().all(|(i, x)| i == x)
            },
            "Permutation is not a valid permutation: This violates the safety contract of the function, so need to get resolved immediately. permutation: {:?}",
            permutation
        );
        let mut tmp_att = self.clone();

        let elem_size = self.num_components * self.component_type.size();
        for (i, &new_idx) in permutation.iter().enumerate() {
            // Copy the value at self[i] to tmp_att[new_idx]
            // We need to copy the raw bytes for each element.
            let src = unsafe { self.as_ptr().add(i * elem_size) };
            let dst = unsafe { tmp_att.as_ptr().add(new_idx * elem_size) };
            unsafe {
                std::ptr::copy_nonoverlapping(src, dst, elem_size);
            }
        }
        mem::swap(self, &mut tmp_att);
    }

    /// Swaps the elements at indices `i` and `j` in the buffer without checking the bounds.
    /// # Safety
    /// This function assumes that `i` and `j` are within the bounds of the buffer.
    pub unsafe fn swap_unchecked(&mut self, i: usize, j: usize) {
        debug_assert!(i < self.len, "Index out of bounds: The index {} is out of bounds for the attribute buffer with length {}", i, self.len);
        debug_assert!(j < self.len, "Index out of bounds: The index {} is out of bounds for the attribute buffer with length {}", j, self.len);

        let elem_size = self.num_components * self.component_type.size();
        let ptr_i = unsafe { self.as_ptr().add(i * elem_size) };
        let ptr_j = unsafe { self.as_ptr().add(j * elem_size) };
        unsafe {
            std::ptr::copy_nonoverlapping(ptr_i, ptr_j, elem_size);
        }
    }

    pub fn from_vec<Data, const N: usize>(data: Vec<Data>) -> Self
    where
        Data: Vector<N>,
        Data::Component: DataValue,
    {
        let component_type = Data::Component::get_dyn();
        let num_components = N;
        let len = data.len();
        let buffer = RawBuffer::from_vec(data);
        let last = unsafe { buffer.as_ptr().add(len * mem::size_of::<Data>()) };

        Self {
            data: buffer,
            len,
            last,
            component_type,
            num_components,
        }
    }

    pub fn remove<Data, const N: usize>(&mut self, i: usize) {
        assert!(i < self.len, "Index out of bounds: The index {} is out of bounds for the attribute buffer with length {}", i, self.len);
        let elem_size = self.num_components * self.component_type.size();
        let ptr = unsafe { self.as_ptr().add(i * elem_size) };
        unsafe {
            std::ptr::copy(ptr.add(elem_size), ptr, (self.len - i - 1) * elem_size);
        }
        self.len -= 1;
        // Update the last pointer
        self.last = unsafe { self.as_ptr().add(self.len * elem_size) };
    }

    /// Retains only the elements at the given sorted indices, compacting the buffer in O(n).
    /// `keep_indices` must be sorted in ascending order and contain valid indices < self.len.
    pub fn retain_indices(&mut self, keep_indices: &[usize]) {
        let elem_size = self.num_components * self.component_type.size();
        let mut write_pos = 0;
        for &idx in keep_indices {
            debug_assert!(idx < self.len, "retain_indices: index {} out of bounds (len {})", idx, self.len);
            if write_pos != idx {
                unsafe {
                    let src = self.as_ptr().add(idx * elem_size);
                    let dst = self.as_ptr().add(write_pos * elem_size);
                    ptr::copy_nonoverlapping(src, dst, elem_size);
                }
            }
            write_pos += 1;
        }
        self.len = keep_indices.len();
        self.last = unsafe { self.as_ptr().add(self.len * elem_size) };
    }
}

impl Serialize for AttributeBuffer {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        let mut s = serializer.serialize_seq(Some(self.len))?;
        match self.component_type {
            ComponentDataType::U8 => match self.num_components {
                1 => s.serialize_element(unsafe { self.as_slice::<[u8; 1]>() }),
                2 => s.serialize_element(unsafe { self.as_slice::<[u8; 2]>() }),
                3 => s.serialize_element(unsafe { self.as_slice::<[u8; 3]>() }),
                4 => s.serialize_element(unsafe { self.as_slice::<[u8; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::U16 => match self.num_components {
                1 => s.serialize_element(unsafe { self.as_slice::<[u16; 1]>() }),
                2 => s.serialize_element(unsafe { self.as_slice::<[u16; 2]>() }),
                3 => s.serialize_element(unsafe { self.as_slice::<[u16; 3]>() }),
                4 => s.serialize_element(unsafe { self.as_slice::<[u16; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::U32 => match self.num_components {
                1 => s.serialize_element(unsafe { self.as_slice::<[u32; 1]>() }),
                2 => s.serialize_element(unsafe { self.as_slice::<[u32; 2]>() }),
                3 => s.serialize_element(unsafe { self.as_slice::<[u32; 3]>() }),
                4 => s.serialize_element(unsafe { self.as_slice::<[u32; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::U64 => match self.num_components {
                1 => s.serialize_element(unsafe { self.as_slice::<[u64; 1]>() }),
                2 => s.serialize_element(unsafe { self.as_slice::<[u64; 2]>() }),
                3 => s.serialize_element(unsafe { self.as_slice::<[u64; 3]>() }),
                4 => s.serialize_element(unsafe { self.as_slice::<[u64; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::F32 => match self.num_components {
                1 => s.serialize_element(unsafe { self.as_slice::<[f32; 1]>() }),
                2 => s.serialize_element(unsafe { self.as_slice::<[f32; 2]>() }),
                3 => s.serialize_element(unsafe { self.as_slice::<[f32; 3]>() }),
                4 => s.serialize_element(unsafe { self.as_slice::<[f32; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::F64 => match self.num_components {
                1 => s.serialize_element(unsafe { self.as_slice::<[f64; 1]>() }),
                2 => s.serialize_element(unsafe { self.as_slice::<[f64; 2]>() }),
                3 => s.serialize_element(unsafe { self.as_slice::<[f64; 3]>() }),
                4 => s.serialize_element(unsafe { self.as_slice::<[f64; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            _ => unimplemented!(),
        }?;
        s.end()
    }
}

impl Clone for AttributeBuffer {
    fn clone(&self) -> Self {
        let data = self.as_slice_u8().to_vec();
        let component_type = self.component_type;
        let num_components = self.num_components;
        let len = self.len;
        let buffer = RawBuffer::from_vec(data);
        let last = unsafe { buffer.as_ptr().add(len * mem::size_of::<u8>()) };

        Self {
            data: buffer,
            len,
            last,
            component_type,
            num_components,
        }
    }
}

impl std::fmt::Debug for AttributeBuffer {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let data = match self.component_type {
            ComponentDataType::Invalid => {
                return format!("Invalid component type").fmt(f);
            }
            ComponentDataType::U8 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[u8; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[u8; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[u8; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[u8; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::U16 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[u16; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[u16; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[u16; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[u16; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::U32 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[u32; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[u32; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[u32; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[u32; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::U64 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[u64; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[u64; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[u64; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[u64; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::F32 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[f32; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[f32; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[f32; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[f32; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::F64 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[f64; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[f64; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[f64; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[f64; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::I8 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[i8; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[i8; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[i8; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[i8; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::I16 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[i16; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[i16; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[i16; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[i16; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::I32 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[i32; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[i32; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[i32; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[i32; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
            ComponentDataType::I64 => match self.num_components {
                1 => format!("{:?}", unsafe { self.as_slice::<[i64; 1]>() }),
                2 => format!("{:?}", unsafe { self.as_slice::<[i64; 2]>() }),
                3 => format!("{:?}", unsafe { self.as_slice::<[i64; 3]>() }),
                4 => format!("{:?}", unsafe { self.as_slice::<[i64; 4]>() }),
                _ => panic!("Unsupported number of components: {}", self.num_components),
            },
        };
        f.debug_struct("AttributeBuffer")
            .field("len", &self.len)
            .field("component_type", &self.component_type)
            .field("num_components", &self.num_components)
            .field("data", &data)
            .finish()
    }
}

impl std::cmp::PartialEq for AttributeBuffer {
    fn eq(&self, other: &Self) -> bool {
        self.len == other.len
            && self.component_type == other.component_type
            && self.num_components == other.num_components
            && (0..self.len() * self.num_components * self.component_type.size()).all(|i| {
                let self_ptr = unsafe { self.as_ptr().add(i) };
                let other_ptr = unsafe { other.as_ptr().add(i) };
                unsafe { ptr::read(self_ptr) == ptr::read(other_ptr) }
            })
    }
}

pub(crate) struct MaybeInitAttributeBuffer {
    /// Contains the data of the attribute.
    data: RawBuffer,

    /// The length of allocation.
    len: usize,

    /// pointer of the last element.
    last: *mut u8,

    component_type: ComponentDataType,

    num_components: usize,

    /// Debugging purpose only; this will not be used in the release mode.
    initialized_elements: Vec<bool>,
}

impl MaybeInitAttributeBuffer {
    /// Creates a new attribute buffer with the given component type and number of components.
    /// This allocates memory for the buffer, but does not initialize it.
    #[allow(unused)]
    pub fn new(len: usize, component_type: ComponentDataType, num_components: usize) -> Self {
        let data = RawBuffer::with_capacity(len * component_type.size() * num_components);
        let last = unsafe {
            data.as_ptr()
                .add(len * component_type.size() * num_components)
        };
        let mut initialized_elements = Vec::with_capacity(len);
        #[cfg(debug_assertions)]
        {
            initialized_elements.resize(len, false);
        }
        Self {
            data,
            len,
            last,
            component_type,
            num_components,
            initialized_elements,
        }
    }

    /// Returns a slice of all the values in the buffer casted to the static type `Data`.
    /// Safety: Callers must know exactly which part of resulting slice is valid. \
    /// Dereferencing the uninitialized part of the slice is undefined behavior.
    /// Moreover, 'num_components * component_type.size()' must equal 'std::mem::size_of::<Data>()'.
    #[allow(unused)]
    pub fn as_slice_unchecked<Data, const N: usize>(&self) -> &[Data]
    where
        Data: Vector<N>,
        Data::Component: DataValue,
    {
        debug_assert_eq!(
            mem::size_of::<Data>(), self.component_type.size() * self.num_components,
            "Cannot create slice: Trying to cast to {}, but the buffer stores elements of type {}D vector of {:?}, which has size {}",
            mem::size_of::<Data>(), self.num_components, self.component_type, self.component_type.size(),
        );
        // Safety: upheld.
        unsafe { std::slice::from_raw_parts(self.data.as_ptr() as *const Data, self.len) }
    }

    #[allow(unused)]
    #[inline]
    pub fn write<Data, const N: usize>(&mut self, idx: usize, data: Data)
    where
        Data: Vector<N>,
        Data::Component: DataValue,
    {
        assert_eq!(
            Data::Component::get_dyn(),
            self.component_type,
            "Data type mismatch: Cannot push data of type {:?} into attribute buffer of type {:?}",
            Data::Component::get_dyn(),
            self.component_type
        );
        assert!(
            N == self.num_components,
            "Number of components mismatch: Cannot push data with {} components into attribute buffer with {} components",
            N, self.num_components
        );
        assert!(idx < self.len, "Index out of bounds: The index {} is out of bounds for the attribute buffer with length {}", idx, self.len);

        self.write_type_unchecked(idx, data);
    }

    /// Safety: The caller must ensure that the type of the data matches the type of the buffer.
    /// Furthermore, the index must be within the bounds of the buffer.
    #[inline]
    pub fn write_type_unchecked<Data, const N: usize>(&mut self, idx: usize, data: Data)
    where
        Data: Vector<N>,
        Data::Component: DataValue,
    {
        debug_assert_eq!(
            Data::Component::get_dyn(),
            self.component_type,
            "Data type mismatch: Cannot push data of type {:?} into attribute buffer of type {:?}",
            Data::Component::get_dyn(),
            self.component_type
        );
        debug_assert!(
            N == self.num_components,
            "Number of components mismatch: Cannot push data with {} components into attribute buffer with {} components",
            N, self.num_components
        );

        debug_assert!(idx < self.len, "Index out of bounds: The index {} is out of bounds for the attribute buffer with length {}", idx, self.len);

        #[cfg(debug_assertions)]
        {
            self.initialized_elements[idx] = true;
        }

        unsafe {
            (self.data.as_ptr() as *mut Data).add(idx).write(data);
        }
    }

    /// Returns the number of values of the attribute.
    #[inline(always)]
    #[allow(unused)]
    pub fn len(&self) -> usize {
        self.len
    }

    /// Returns the component type of the attribute.
    #[inline(always)]
    #[allow(unused)]
    pub fn get_component_type(&self) -> ComponentDataType {
        self.component_type
    }

    /// Returns the number of components.
    #[inline(always)]
    #[allow(unused)]
    pub fn get_num_components(&self) -> usize {
        self.num_components
    }
}

impl From<MaybeInitAttributeBuffer> for AttributeBuffer {
    fn from(maybe_init: MaybeInitAttributeBuffer) -> Self {
        debug_assert!(
            maybe_init.initialized_elements.iter().all(|&x| x),
            "Not all elements are initialized: Out of {} elements, uninitialized are {:?}",
            maybe_init.len,
            maybe_init.initialized_elements.iter().filter(|&&x| !x)
        );

        Self {
            data: maybe_init.data,
            len: maybe_init.len,
            last: maybe_init.last,
            component_type: maybe_init.component_type,
            num_components: maybe_init.num_components,
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::prelude::NdVector;

    use super::*;
    #[test]
    fn clone() {
        let data = vec![
            NdVector::from([1.0f32, 2.0, 3.0]),
            NdVector::from([4.0f32, 5.0, 6.0]),
            NdVector::from([7.0f32, 8.0, 9.0]),
        ];

        let att = AttributeBuffer::from_vec(data);

        let att_clone = att.clone();
        assert_eq!(att, att_clone, "The clone is not equal to the original");
    }

    #[test]
    fn maybe_init() {
        let mut buffer = MaybeInitAttributeBuffer::new(5, ComponentDataType::F32, 3);
        let data = (0..5)
            .map(|i| NdVector::from([i as f32, i as f32, i as f32]))
            .collect::<Vec<_>>();
        let mut idx = 1;
        for _ in 0..5 {
            idx = (idx * 2) % 5; // 2 is a generator of $ \Z / 5 \Z $
            buffer.write(idx, data[idx]);
        }
        buffer.write(0, data[0]);

        let att = AttributeBuffer::from(buffer);
        // check if the data is correct
        let answer = AttributeBuffer::from_vec(data);
        assert_eq!(
            att, answer,
            "The attribute buffer is not equal to the original"
        );
    }

    #[test]
    fn test_permute() {
        let data = vec![
            NdVector::from([1f32, 2.0, 3.0]),
            NdVector::from([4f32, 5.0, 6.0]),
            NdVector::from([7f32, 8.0, 9.0]),
        ];
        let mut att = AttributeBuffer::from_vec(data);
        let permutation = vec![2, 1, 0];
        unsafe {
            att.permute_unchecked(&permutation);
        }
        let expected_data = vec![
            NdVector::from([7f32, 8.0, 9.0]),
            NdVector::from([4f32, 5.0, 6.0]),
            NdVector::from([1f32, 2.0, 3.0]),
        ];
        let expected_att = AttributeBuffer::from_vec(expected_data);
        assert_eq!(att, expected_att);
    }
}