/// This crate will utilize a textured quad to draw a texture onto a surface

use vulkano::buffer::{Buffer, BufferContents, BufferCreateInfo, BufferUsage, Subbuffer};
use vulkano::memory::allocator::{AllocationCreateInfo, MemoryUsage, StandardMemoryAllocator};
use vulkano::pipeline::graphics::vertex_input::Vertex;

// We now create a buffer that will store the shape of our triangle. We use `#[repr(C)]` here
// to force rustc to use a defined layout for our data, as the default representation has *no
// guarantees*.
#[derive(BufferContents, Vertex)]
#[repr(C)]
pub struct TexturedVertex {
    // vertex coordinates in object space
    // in this case also equals to view space
    #[format(R32G32_SFLOAT)]
    position: [f32; 2],
    // uv coordinates per vertex
    #[format(R32G32_SFLOAT)]
    texture: [f32; 2]
}

fn textured_quad() -> (Vec<TexturedVertex>, Vec<u32>) {
    (
        // vertex list
        vec![
            TexturedVertex {
                position: [-1.0, -1.0],
                texture: [0.0, 0.0]
            },
            TexturedVertex {
                position: [1.0, -1.0],
                texture: [1.0, 0.0]
            },
            TexturedVertex {
                position: [1.0, 1.0],
                texture: [1.0, 1.0]
            },
            TexturedVertex {
                position: [-1.0, 1.0],
                texture: [0.0, 1.0]
            }
        ],
        // indices list
        vec![
            0, 1, 2,
            0, 2, 3
        ]
    )
}

pub fn create_quad_buffer(memory_allocator: &StandardMemoryAllocator) -> (Subbuffer<[TexturedVertex]>, Subbuffer<[u32]>) {
    let (vertices, indices) = textured_quad();

    let vertex_buffer = Buffer::from_iter(
        memory_allocator,
        BufferCreateInfo {
            usage: BufferUsage::VERTEX_BUFFER,
            ..Default::default()
        },
        AllocationCreateInfo {
            usage: MemoryUsage::Upload,
            ..Default::default()
        },
        vertices,
    ).unwrap();

    let index_buffer = Buffer::from_iter(
        memory_allocator,
        BufferCreateInfo {
            usage: BufferUsage::INDEX_BUFFER,
            ..Default::default()
        },
        AllocationCreateInfo {
            usage: MemoryUsage::Upload,
            ..Default::default()
        },
        indices,
    ).unwrap();

    (vertex_buffer, index_buffer)
}