use super::Texture;
use super::{Material, Mesh, Vertex};
use anyhow::Result;
use bytemuck::{Pod, Zeroable};
use std::path::Path;
use tobj::LoadOptions;
use wgpu::util::DeviceExt;

pub struct Model {
    pub meshes: Vec<Mesh>,
    pub materials: Vec<Material>,
}

impl Model {
    pub fn Load<P: AsRef<Path>>(
        device: &wgpu::Device,
        queue: &wgpu::Queue,
        layout: &wgpu::BindGroupLayout,
        path: P,
    ) -> Result<Self> {
        let (obj_models, obj_materials) = tobj::load_obj(
            path.as_ref(),
            &LoadOptions {
                triangulate: true,
                single_index: true,
                ..Default::default()
            },
        )?;

        let obj_materials = obj_materials?;

        // We're assuming that the texture files are stored with the obj file
        let containing_folder = path.as_ref().parent().expect("Directory has no parent");

        let mut materials = Vec::new();
        for mat in obj_materials {
            let diffuse_path = mat.diffuse_texture;
            let diffuse_texture =
                Texture::Load(device, queue, containing_folder.join(diffuse_path))?;

            let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
                layout,
                entries: &[
                    wgpu::BindGroupEntry {
                        binding: 0,
                        resource: wgpu::BindingResource::TextureView(&diffuse_texture.view),
                    },
                    wgpu::BindGroupEntry {
                        binding: 1,
                        resource: wgpu::BindingResource::Sampler(&diffuse_texture.sampler),
                    },
                ],
                label: None,
            });

            materials.push(Material {
                name: mat.name,
                diffuse_texture,
                bind_group,
            });
        }

        let mut meshes = Vec::new();
        for m in obj_models {
            let mut vertices = Vec::new();
            for i in 0..m.mesh.positions.len() / 3 {
                vertices.push(ModelVertex {
                    position: [
                        m.mesh.positions[i * 3],
                        m.mesh.positions[i * 3 + 1],
                        m.mesh.positions[i * 3 + 2],
                    ],
                    tex_coords: [m.mesh.texcoords[i * 2], m.mesh.texcoords[i * 2 + 1]],
                    normal: [
                        m.mesh.normals[i * 3],
                        m.mesh.normals[i * 3 + 1],
                        m.mesh.normals[i * 3 + 2],
                    ],
                });
            }

            let vertex_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
                label: Some(&format!("{:?} Vertex Buffer", path.as_ref())),
                contents: bytemuck::cast_slice(&vertices),
                usage: wgpu::BufferUsages::VERTEX,
            });
            let index_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
                label: Some(&format!("{:?} Index Buffer", path.as_ref())),
                contents: bytemuck::cast_slice(&m.mesh.indices),
                usage: wgpu::BufferUsages::INDEX,
            });

            meshes.push(Mesh {
                name: m.name,
                vertex_buffer,
                index_buffer,
                num_elements: m.mesh.indices.len() as u32,
                material: m.mesh.material_id.unwrap_or(0),
            });
        }

        Ok(Self { meshes, materials })
    }
}

#[repr(C)]
#[derive(Copy, Clone, Debug, Pod, Zeroable)]
pub struct ModelVertex {
    position: [f32; 3],
    tex_coords: [f32; 2],
    normal: [f32; 3],
}

impl Vertex for ModelVertex {
    fn GetDescriptor<'a>() -> wgpu::VertexBufferLayout<'a> {
        use std::mem;
        wgpu::VertexBufferLayout {
            array_stride: mem::size_of::<ModelVertex>() as wgpu::BufferAddress,
            step_mode: wgpu::VertexStepMode::Vertex,
            attributes: &[
                wgpu::VertexAttribute {
                    offset: 0,
                    shader_location: 0,
                    format: wgpu::VertexFormat::Float32x3,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 3]>() as wgpu::BufferAddress,
                    shader_location: 1,
                    format: wgpu::VertexFormat::Float32x2,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 5]>() as wgpu::BufferAddress,
                    shader_location: 2,
                    format: wgpu::VertexFormat::Float32x3,
                },
            ],
        }
    }
}