use super::GLContext;
use glow::HasContext;
use std::marker::PhantomData;
use std::mem;

pub struct GLArrayBuffer<ArrayMemberType> {
    buffer_id: <GLContext as HasContext>::Buffer,
    _type_marker: PhantomData<ArrayMemberType>,
}

impl<ArrayMemberType> GLArrayBuffer<ArrayMemberType> {
    pub fn new(gl: &glow::Context, data: &[ArrayMemberType]) -> Self {
        let buffer_id = unsafe { gl.create_buffer().expect("vertex buffer") };

        unsafe {
            gl.bind_buffer(glow::ARRAY_BUFFER, Some(buffer_id));

            let byte_len = mem::size_of_val(&data[0]) * data.len() / mem::size_of::<u8>();
            let byte_slice = std::slice::from_raw_parts(data.as_ptr() as *const u8, byte_len);
            gl.buffer_data_u8_slice(glow::ARRAY_BUFFER, byte_slice, glow::STATIC_DRAW);
        }

        Self { buffer_id, _type_marker: PhantomData }
    }

    pub fn bind(&self, gl: &glow::Context, attribute_location: u32) {
        unsafe {
            gl.bind_buffer(glow::ARRAY_BUFFER, Some(self.buffer_id));

            // TODO #5: generalize GL array buffer size/data_type handling beyond f32
            gl.vertex_attrib_pointer_f32(
                attribute_location,
                (mem::size_of::<ArrayMemberType>() / mem::size_of::<f32>()) as i32,
                glow::FLOAT,
                false,
                0,
                0,
            );
            gl.enable_vertex_attrib_array(attribute_location);
        }
    }

    // TODO #3: make sure we release GL resources
    /*
    fn drop(&mut self, gl: &glow::Context) {
        unsafe {
            gl.delete_buffer(self.buffer_id);
        }
    }
    */
}

pub struct GLIndexBuffer<IndexType> {
    buffer_id: <GLContext as HasContext>::Buffer,
    pub len: i32,
    _vertex_marker: PhantomData<IndexType>,
}

impl<IndexType> GLIndexBuffer<IndexType> {
    pub fn new(gl: &glow::Context, data: &[IndexType]) -> Self {
        let buffer_id = unsafe { gl.create_buffer().expect("vertex buffer") };

        unsafe {
            gl.bind_buffer(glow::ELEMENT_ARRAY_BUFFER, Some(buffer_id));

            let byte_len = mem::size_of_val(&data[0]) * data.len() / mem::size_of::<u8>();
            let byte_slice = std::slice::from_raw_parts(data.as_ptr() as *const u8, byte_len);
            gl.buffer_data_u8_slice(glow::ELEMENT_ARRAY_BUFFER, byte_slice, glow::STATIC_DRAW);
        }

        Self { buffer_id, len: data.len() as i32, _vertex_marker: PhantomData }
    }

    pub fn bind(&self, gl: &glow::Context) {
        unsafe {
            gl.bind_buffer(glow::ELEMENT_ARRAY_BUFFER, Some(self.buffer_id));
        }
    }

    // TODO #3: make sure we release GL resources
    /*
    fn drop(&mut self, gl: &glow::Context) {
        unsafe {
            gl.delete_buffer(self.buffer_id);
        }
    }
    */
}