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use std::mem;
use std::slice;
use std::ops::Deref;
use nalgebra as na;
use na::{Dim, U1, U2, U3, U4};

pub use shaderdata_derive::*;

#[derive(Clone)]
pub struct Data{
    data: Vec<u8>,
}

impl Data{
    pub fn new() -> Data {
        Self::default()
    }

    pub fn with_capacity(capacity: usize) -> Data {
        Data{
            data: Vec::with_capacity(capacity),
        }
    }

    pub fn push<T: WriteStd140>(&mut self, data: T){
        data.write_std140(self)
    }

    pub fn clear(&mut self){
        self.data.clear();
    }

    pub fn bytes(&self) -> usize{
        self.data.len()
    }

    pub fn pad_bytes(&mut self, bytes: usize) {
        self.data.resize(self.data.len() + bytes, 0)
    }

    pub fn pad<T>(&mut self) {
        unsafe{
            self.data.extend_from_slice(slice::from_raw_parts(
                mem::MaybeUninit::<T>::uninit().as_ptr() as *const u8,
                mem::size_of::<T>()
            ))
        };
    }

    pub fn start_struct(&mut self) -> StructBuilder {
        StructBuilder {
            initial_len: self.bytes(),
            data: self,
        }
    }
}

impl Deref for Data{
    type Target = [u8];
    fn deref(&self) -> &[u8]{
        &self.data
    }
}

impl Default for Data{
    fn default() -> Data{
        Data{
            data: vec![],
        }
    }
}

impl PartialEq for Data{
    fn eq(&self, other: &Data) -> bool{
        self.data.eq(&other.data)
    }
}

pub struct StructBuilder<'a> {
    data: &'a mut Data,
    initial_len: usize,
}

impl<'a> Drop for StructBuilder<'a> {
    fn drop(&mut self) {
        let total = self.data.bytes() - self.initial_len;
        let rem = total % 16;
        if rem != 0 {
            let padding = 16 - rem;
            self.data.pad_bytes(padding);
        }
    }
}

impl<'a> StructBuilder<'a>{
    pub fn push<T: WriteStd140>(&mut self, data: T){
        self.data.push(data)
    }

    pub fn pad_bytes(&mut self, bytes: usize) {
        self.data.pad_bytes(bytes)
    }

    pub fn pad<T>(&mut self) {
        self.data.pad::<T>()
    }

    pub fn finish(self) {
        std::mem::drop(self)
    }
}


pub trait Std140: 'static {
    const ALIGNMENT: usize;
}

impl Std140 for f32 {
    const ALIGNMENT: usize = 4;
}

impl Std140 for i32 {
    const ALIGNMENT: usize = 4;
}

impl Std140 for u32 {
    const ALIGNMENT: usize = 4;
}

impl<T: na::Scalar + Std140> Std140 for na::Vector2<T> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 2;
}

impl<T: na::Scalar + Std140> Std140 for (na::Vector2<T>, na::Vector2<T>) {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

impl<T: na::Scalar + Std140> Std140 for na::Point2<T> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 2;
}

impl<T: na::Scalar + Std140> Std140 for [T;2] {
    const ALIGNMENT: usize = mem::size_of::<T>() * 2;
}

impl<T: na::Scalar + Std140> Std140 for na::Vector3<T> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

impl<T: na::Scalar + Std140> Std140 for na::Point3<T> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

impl<T: na::Scalar + Std140> Std140 for [T;3] {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

impl<T: na::Scalar + Std140> Std140 for na::Vector4<T> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

impl<T: na::Scalar + Std140> Std140 for na::Point4<T> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

impl<T: na::Scalar + Std140> Std140 for [T;4] {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

impl<T: na::Scalar + Std140> Std140 for na::Matrix4<T> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

impl<T: Std140> Std140 for na::Unit<T> {
    const ALIGNMENT: usize = T::ALIGNMENT;
}

impl<T: Std140> Std140 for mem::MaybeUninit<T>{
    const ALIGNMENT: usize = T::ALIGNMENT;
}

impl<T: Std140> Std140 for angle::Rad<T>{
    const ALIGNMENT: usize = T::ALIGNMENT;
}

impl<T: Std140> Std140 for angle::Deg<T>{
    const ALIGNMENT: usize = T::ALIGNMENT;
}

impl<T: Std140, S: 'static> Std140 for color::Rgb<T, S> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

impl<T: Std140, S: 'static> Std140 for color::Rg<T, S> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 2;
}

impl<T: Std140, S: 'static> Std140 for color::AlphaColor<T, color::Rgb<T, S>> {
    const ALIGNMENT: usize = mem::size_of::<T>() * 4;
}

pub trait WriteStd140 {
    fn write_std140(&self, data: &mut Data);
}

impl<T: Std140> WriteStd140 for T {
    fn write_std140(&self, data: &mut Data) {
        if data.len() % T::ALIGNMENT != 0 {
            let padding = T::ALIGNMENT - data.len() % T::ALIGNMENT;
            data.pad_bytes(padding);
        }

        unsafe{
            data.data.extend_from_slice(slice::from_raw_parts(
                self as *const T as *const u8,
                mem::size_of::<T>()
            ));
        }
    }
}

impl<T: na::Scalar + Std140 + Copy> WriteStd140 for na::Matrix3<T> {
    fn write_std140(&self, data: &mut Data) {
        data.push(*self.column(0).as_ref());
        data.push(*self.column(1).as_ref());
        data.push(*self.column(2).as_ref());
    }
}

impl<T: WriteStd140> WriteStd140 for Vec<T> {
    fn write_std140(&self, data: &mut Data) {
        for item in self {
            item.write_std140(data);
        }
    }
}

#[test]
fn test() {
    #[derive(Std140, Clone, Copy)]
    struct Std140Struct {
        field0: na::Vector3<f32>,
        field1: f32,
        field2: na::Vector3<f32>,
        field3: f32,
        field4: f32,
    }

    let v = unsafe{ vec![mem::MaybeUninit::<Std140Struct>::uninit().assume_init();10] };
    let mut data = Data::new();
    data.push(v);
    assert_eq!(data.len(), 12 * 4 * 10);
}

#[test]
fn test_manual_padding() {
    let mut data = Data::new();
    data.push(0f32);
    data.push(0f32);
    data.push(na::Vector2::new(0f32, 0f32));
    data.push(na::Vector2::new(0f32, 0f32));
    data.push(0f32);
    data.push(0f32);
    data.push(na::one::<na::Matrix4<f32>>());
    data.push(0i32);
    data.pad::<[f32;3]>();

    assert_eq!(data.bytes(), 28 * 4);
}

#[test]
fn test_struct_buider() {
    let mut data = Data::new();
    let mut struct_data = data.start_struct();
    struct_data.push(na::Vector4::new(0f32, 0f32, 0f32, 0f32));
    struct_data.push(na::Vector3::new(0f32, 0f32, 0f32));
    struct_data.push(0f32);
    struct_data.push(0f32);
    struct_data.push(0f32);
    struct_data.push(na::Vector4::new(0f32, 0f32, 0f32, 0f32));
    struct_data.push(na::Vector4::new(0f32, 0f32, 0f32, 0f32));
    struct_data.push(0f32);
    struct_data.push(na::Vector4::new(0f32, 0f32, 0f32, 0f32));
    struct_data.push(na::Vector4::new(0f32, 0f32, 0f32, 0f32));
    struct_data.push(na::Vector4::new(0i32, 0i32, 0i32, 0i32));
    struct_data.push(na::Vector4::new(0i32, 0i32, 0i32, 0i32));
    struct_data.push(na::one::<na::Matrix4<f32>>());
    std::mem::drop(struct_data);
    assert_eq!(data.bytes(),  56 * 4);
}