lyra-engine/lyra-resource/src/material.rs

use std::{fs::File, io::{BufReader, Read}, collections::hash_map::DefaultHasher, hash::{Hash, Hasher}};

use crate::{Texture, ResHandle, ResourceManager, util};

/// PBR metallic roughness 
#[derive(Clone, Debug, Default)]
pub struct PbrRoughness {
    /// The rgba base color of the PBR material
    pub base_color: [f32; 4],
    /// The metalness of the material
    /// From 0.0 (non-metal) to 1.0 (metal)
    pub metallic: f32,
    /// The roughness of the material
    /// From 0.0 (smooth) to 1.0 (rough)
    pub roughness: f32,
    // TODO: base_color_texture and metallic_roughness_texture
}

impl From<gltf::material::PbrMetallicRoughness<'_>> for PbrRoughness {
    fn from(value: gltf::material::PbrMetallicRoughness) -> Self {
        PbrRoughness {
            base_color: value.base_color_factor(),
            metallic: value.metallic_factor(),
            roughness: value.roughness_factor(),
        }
    }
}

#[derive(Clone, Debug, Default)]
pub struct PbrGlossiness {
    /// The rgba diffuse color of the material
    pub diffuse_color: glam::Vec4,
    // The base color texture
    // pub diffuse_texture // TODO
    pub specular: glam::Vec3,
    /// The glossiness factor of the material.
    /// From 0.0 (no glossiness) to 1.0 (full glossiness)
    pub glossiness: f32,
    // pub glossiness_texture // TODO
}

impl From<gltf::material::PbrSpecularGlossiness<'_>> for PbrGlossiness {
    fn from(value: gltf::material::PbrSpecularGlossiness) -> Self {
        PbrGlossiness {
            diffuse_color: value.diffuse_factor().into(),
            specular: value.specular_factor().into(),
            glossiness: value.glossiness_factor()
        }
    }
}

/// The alpha rendering mode of a material.
/// This is essentially a re-export of gltf::material::AlphaMode
#[derive(Clone, Copy, Eq, PartialEq, Debug, Default)]
pub enum AlphaMode {
    /// The alpha value is ignored and the rendered output is fully opaque.
    #[default]
    Opaque = 1,

    /// The rendered output is either fully opaque or fully transparent depending on
    /// the alpha value and the specified alpha cutoff value.
    Mask,

    /// The alpha value is used, to determine the transparency of the rendered output.
    /// The alpha cutoff value is ignored.
    Blend,
}

impl From<gltf::material::AlphaMode> for AlphaMode {
    fn from(value: gltf::material::AlphaMode) -> Self {
        match value {
            gltf::material::AlphaMode::Opaque => AlphaMode::Opaque,
            gltf::material::AlphaMode::Mask => AlphaMode::Mask,
            gltf::material::AlphaMode::Blend => AlphaMode::Blend,
        }
    }
}

#[derive(Clone, Default)]
pub struct Material {
    pub shader_uuid: Option<u64>,
    pub name: Option<String>,
    pub double_sided: bool,
    
    //pub pbr_roughness: PbrRoughness,
    /// The RGBA base color of the model. If a texture is supplied with `base_color_texture`, this value
    /// will tint the texture. If a texture is not provided, this value would be the color of the Material.
    pub base_color: glam::Vec4,
    /// The metalness of the material
    /// From 0.0 (non-metal) to 1.0 (metal)
    pub metallic: f32,
    /// The roughness of the material
    /// From 0.0 (smooth) to 1.0 (rough)
    pub roughness: f32,
    /// The base color texture of the model.
    pub base_color_texture: Option<ResHandle<Texture>>,

    /// The metallic-roughness texture.
    /// 
    /// The metalness values are sampled from the B channel. The roughness values are sampled from
    /// the G channel. These values are linear. If other channels are present (R or A), they are
    /// ignored for metallic-roughness calculations.
    pub metallic_roughness_texture: Option<ResHandle<Texture>>,

    /// A set of parameter values that are used to define the specular-glossiness material model
    /// from Physically-Based Rendering (PBR) methodology.
    /// GLTF extension: [KHR_materials_pbrSpecularGlossiness](https://kcoley.github.io/glTF/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness)
    pub pbr_glossiness: Option<PbrGlossiness>,

    /// The optional alpha cutoff value of the material.
    pub alpha_cutoff: Option<f32>,

    /// The alpha rendering mode of the material.  The material's alpha rendering
    /// mode enumeration specifying the interpretation of the alpha value of the main
    /// factor and texture.
    ///
    /// * In `Opaque` mode (default) the alpha value is ignored
    ///   and the rendered output is fully opaque.
    /// * In `Mask` mode, the rendered
    ///   output is either fully opaque or fully transparent depending on the alpha
    ///   value and the specified alpha cutoff value.
    /// * In `Blend` mode, the alpha value is used to composite the source and
    ///   destination areas and the rendered output is combined with the background
    ///   using the normal painting operation (i.e. the Porter and Duff over
    ///   operator).
    pub alpha_mode: AlphaMode,

    //pub texture: Option<ResHandle<Texture>>,
}

impl Material {
    /// Get a uri's identifier
    /// 
    /// I'm not actually sure how identifiable this would be
    fn uri_ident(gltf_rel_path: &str, uri: &str) -> String {
        let mut hasher = DefaultHasher::new();
        uri.hash(&mut hasher);
        let hash = hasher.finish();

        format!("{gltf_rel_path};{hash}")
    }

    fn source_ident(gltf_rel_path: &str, src: &gltf::image::Source) -> Option<String> {
        match src {
            gltf::image::Source::View { view, mime_type } => {
                let buf = view.buffer();
                let src = buf.source();

                match src {
                    gltf::buffer::Source::Bin => None,
                    gltf::buffer::Source::Uri(uri) => {
                        Some(Material::uri_ident(gltf_rel_path, uri))
                    }
                }
            },
            gltf::image::Source::Uri { uri, mime_type } => {
                Some(Material::uri_ident(gltf_rel_path, uri))
            },
        }
    }

    fn read_source(resource_manager: &mut ResourceManager, gltf_rel_path: &str, src: gltf::image::Source) -> Result<Vec<u8>, util::UriReadError> {
        // TODO: Don't copy sources
        match src {
            gltf::image::Source::View { view, mime_type } => {
                let buf = view.buffer();
                let src = buf.source();

                let offset = view.offset();
                let len = view.length();

                match src {
                    gltf::buffer::Source::Bin => todo!("Read material source from gltf Bin"),
                    gltf::buffer::Source::Uri(uri) => {
                        util::gltf_read_buffer_uri(gltf_rel_path, uri)
                            .map(|mut buf| {
                                buf.drain(0..offset);
                                buf.truncate(len);
                                buf
                            })
                    }
                }
            },
            gltf::image::Source::Uri { uri, mime_type } => {
                util::gltf_read_buffer_uri(gltf_rel_path, uri)
            },
        }
    }

    fn load_texture(resource_manager: &mut ResourceManager, gltf_rel_path: &str, texture_info: gltf::texture::Info<'_>) -> ResHandle<Texture> {
        // TODO: texture_info.tex_coord() 
        let tex = texture_info.texture();
        let img = tex.source();
        let src = img.source();
        
        let buf = Material::read_source(resource_manager, gltf_rel_path, src).unwrap();
        let buflen = buf.len();
        let mime_type = infer::get(&buf).expect("Failed to get file type").mime_type();

        resource_manager.load_bytes::<Texture>(&uuid::Uuid::new_v4().to_string(), mime_type,
            buf, 0, buflen).unwrap()
    }

    /// Load the Material from a gltf::Material.
    /// 
    /// `gltf_rel_path`: The relative path of the gltf file,
    ///     e.g. gltf model path is "resource/models/player.gltf", the relative path would be "resource/models/"
    pub fn from_gltf(resource_manager: &mut ResourceManager, gltf_rel_path: &str, gltf_mat: gltf::Material) -> Self {
        let pbr_rough = gltf_mat.pbr_metallic_roughness();
        let base_color = pbr_rough.base_color_factor().into();
        let metallic = pbr_rough.metallic_factor();
        let roughness = pbr_rough.roughness_factor();
        
        let base_color_texture = pbr_rough.base_color_texture()
            .map(|info| Material::load_texture(resource_manager, gltf_rel_path, info));

        let metallic_roughness_texture = pbr_rough.metallic_roughness_texture()
            .map(|info| Material::load_texture(resource_manager, gltf_rel_path, info));

        /* let base_color_texture = if let Some(base_tex_info) = pbr_rough.base_color_texture() {
            Some(Material::load_texture(resource_manager, gltf_rel_path, base_tex_info))
        } else { None }; */
        
        Material {
            name: gltf_mat.name()
                .map(|s| s.to_string()),
            double_sided: gltf_mat.double_sided(),
            base_color,
            metallic,
            roughness,
            pbr_glossiness: gltf_mat.pbr_specular_glossiness()
                .map(|o| o.into()),
            alpha_cutoff: gltf_mat.alpha_cutoff(),
            alpha_mode: gltf_mat.alpha_mode().into(),
            shader_uuid: None,
            
            // TODO
            base_color_texture,
            metallic_roughness_texture,
        }
    }
}