//! Tiny OBJ loader, inspired by Syoyo's excellent [tinyobjloader](https://github.com/syoyo/tinyobjloader).
//! Aims to be a simple and lightweight option for loading OBJ files, just returns two vecs
//! containing loaded models and materials. All models are made of triangles, any quad or polygon faces
//! in an OBJ file will be converted to triangles. Note that only polygons that are trivially
//! convertible to triangle fans are supported, arbitrary polygons may not behave as expected.
//! The best solution would be to re-export your mesh using only triangles in your modeling software.
//!
//! It is assumed that all meshes will at least have positions, but normals and texture coordinates
//! are optional. If no normals or texture coordinates were found then the corresponding vecs for
//! the mesh will be empty. Values are stored packed as floats in vecs, eg. the positions member of
//! a loaded mesh will contain `[x, y, z, x, y, z, ...]` which you can then use however you like.
//! Indices are also loaded and may re-use vertices already existing in the mesh, this data is
//! stored in the `indices` member.
//!
//! Standard MTL attributes are supported as well and any unrecognized parameters will be stored in a
//! `HashMap` containing the key-value pairs of the unrecognized parameter and its value.
//!
//! # Example
//! In this simple example we load the classic Cornell Box model that only defines positions and
//! print out its attributes. This example is a slightly trimmed down version of `print_model_info`
//! and `print_material_info` combined together, see them for a version that also prints out
//! normals and texture coordinates if the model has them.
//!
//! ```
//! use tobj;
//!
//! let cornell_box = tobj::load_obj("cornell_box.obj", true);
//! assert!(cornell_box.is_ok());
//! let (models, materials) = cornell_box.unwrap();
//!
//! println!("# of models: {}", models.len());
//! println!("# of materials: {}", materials.len());
//! for (i, m) in models.iter().enumerate() {
//!     let mesh = &m.mesh;
//!     println!("model[{}].name = \'{}\'", i, m.name);
//!     println!("model[{}].mesh.material_id = {:?}", i, mesh.material_id);
//!
//!     println!("Size of model[{}].num_face_indices: {}", i, mesh.num_face_indices.len());
//!     let mut next_face = 0;
//!     for f in 0..mesh.num_face_indices.len() {
//!         let end = next_face + mesh.num_face_indices[f] as usize;
//!         let face_indices: Vec<_> = mesh.indices[next_face..end].iter().collect();
//!         println!("    face[{}] = {:?}", f, face_indices);
//!         next_face = end;
//!     }
//!
//!     // Normals and texture coordinates are also loaded, but not printed in this example
//!     println!("model[{}].vertices: {}", i, mesh.positions.len() / 3);
//!     assert!(mesh.positions.len() % 3 == 0);
//!     for v in 0..mesh.positions.len() / 3 {
//!         println!("    v[{}] = ({}, {}, {})", v, mesh.positions[3 * v],
//!         mesh.positions[3 * v + 1], mesh.positions[3 * v + 2]);
//!     }
//! }
//!
//! for (i, m) in materials.iter().enumerate() {
//!     println!("material[{}].name = \'{}\'", i, m.name);
//!     println!("    material.Ka = ({}, {}, {})", m.ambient[0], m.ambient[1],
//!     m.ambient[2]);
//!     println!("    material.Kd = ({}, {}, {})", m.diffuse[0], m.diffuse[1],
//!     m.diffuse[2]);
//!     println!("    material.Ks = ({}, {}, {})", m.specular[0], m.specular[1],
//!     m.specular[2]);
//!     println!("    material.Ns = {}", m.shininess);
//!     println!("    material.d = {}", m.dissolve);
//!     println!("    material.map_Ka = {}", m.ambient_texture);
//!     println!("    material.map_Kd = {}", m.diffuse_texture);
//!     println!("    material.map_Ks = {}", m.specular_texture);
//!     println!("    material.map_Ns = {}", m.shininess_texture);
//!     println!("    material.map_Bump = {}", m.normal_texture);
//!     println!("    material.map_d = {}", m.dissolve_texture);
//!     for (k, v) in &m.unknown_param {
//!         println!("    material.{} = {}", k, v);
//!     }
//! }
//! ```
//!
//! # Rendering Examples
//! For an example of integration with [glium](https://github.com/tomaka/glium) to make a simple OBJ viewer,
//! check out [tobj viewer](https://github.com/Twinklebear/tobj_viewer). Some sample images can be found in
//! tobj viewer's readme or in [this gallery](http://imgur.com/a/xsg6v).
//!
//! The Rungholt model shown below is reasonably large (6.7M triangles, 12.3M vertices) and is loaded
//! in ~7.47s using a peak of ~1.1GB of memory on a Windows 10 machine with an i7-4790k and 16GB of
//! 1600Mhz DDR3 RAM with tobj 0.1.1 on rustc 1.6.0.
//! The model can be found on [Morgan McGuire's](http://graphics.cs.williams.edu/data/meshes.xml) meshes page and
//! was originally built by kescha. Future work will focus on improving performance and memory usage.
//!
//! <img src="http://i.imgur.com/wImyNG4.png" alt="Rungholt"
//!     style="display:block; max-width:100%; height:auto">
//!
//! For an example of integration within a ray tracer, check out tray\_rust's
//! [mesh module](https://github.com/Twinklebear/tray_rust/blob/master/src/geometry/mesh.rs).
//! The Stanford Buddha and Dragon from the
//! [Stanford 3D Scanning Repository](http://graphics.stanford.edu/data/3Dscanrep/) both load quite quickly.
//! The Rust logo model was made by
//! [Nylithius on BlenderArtists](http://blenderartists.org/forum/showthread.php?362836-Rust-language-3D-logo).
//! The materials used are from the [MERL BRDF Database](http://www.merl.com/brdf/).
//!
//! <img src="http://i.imgur.com/E1ylrZW.png" alt="Rust logo with friends"
//!     style="display:block; max-width:100%; height:auto">
//!

#![allow(dead_code)]
#![cfg_attr(all(test, feature = "unstable"), feature(test))]
#![cfg_attr(feature = "unstable", feature(plugin))]
#![cfg_attr(feature = "unstable", plugin(clippy))]

#[cfg(all(test, feature = "unstable"))]
extern crate test;

use std::collections::HashMap;
use std::error::Error;
use std::fmt;
use std::fs::File;
use std::io::prelude::*;
use std::io::BufReader;
use std::path::Path;
use std::str::{FromStr, SplitWhitespace};

/// A mesh made up of triangles loaded from some OBJ file
///
/// It is assumed that all meshes will at least have positions, but normals and texture coordinates
/// are optional. If no normals or texture coordinates where found then the corresponding vecs for
/// the mesh will be empty. Values are stored packed as floats in vecs, eg. the positions member of
/// a loaded mesh will contain `[x, y, z, x, y, z, ...]` which you can then use however you like.
/// Indices are also loaded and may re-use vertices already existing in the mesh, this data is
/// stored in the `indices` member.
///
/// # Example:
/// Load the Cornell box and get the attributes of the first vertex. It's assumed all meshes will
/// have positions (required), but normals and texture coordinates are optional, in which case the
/// corresponding Vec will be empty.
///
/// ```
/// let cornell_box = tobj::load_obj("cornell_box.obj", true);
/// assert!(cornell_box.is_ok());
/// let (models, materials) = cornell_box.unwrap();
///
/// let mesh = &models[0].mesh;
/// let i = mesh.indices[0] as usize;
/// // pos = [x, y, z]
/// let pos = [mesh.positions[i * 3], mesh.positions[i * 3 + 1],
///             mesh.positions[i * 3 + 2]];
///
/// if !mesh.normals.is_empty() {
///     // normal = [x, y, z]
///     let normal = [mesh.normals[i * 3], mesh.normals[i * 3 + 1],
///                   mesh.normals[i * 3 + 2]];
/// }
///
/// if !mesh.texcoords.is_empty() {
///     // texcoord = [u, v];
///     let texcoord = [mesh.texcoords[i * 2], mesh.texcoords[i * 2 + 1]];
/// }
/// ```
#[derive(Debug, Clone)]
pub struct Mesh {
    /// Flattened 3 component floating point vectors, storing positions of vertices in the mesh
    pub positions: Vec<f32>,
    /// Flattened 3 component floating point vectors, storing normals of vertices in the mesh. Not
    /// all meshes have normals, if no normals are specified this Vec will be empty
    pub normals: Vec<f32>,
    /// Flattened 2 component floating point vectors, storing texture coordinates of vertices in
    /// the mesh. Not all meshes have normals, if no texture coordinates are specified this Vec
    /// will be empty
    pub texcoords: Vec<f32>,
    /// Indices for vertices of each triangle. If loaded with `triangulate_faces`, each face in the
    /// mesh is a triangle, otherwise the `num_face_indices` vector indicates how many indices
    /// are used by each face. The indices specify the position, normal and texture coordinate
    /// for each vertex of the face.
    pub indices: Vec<u32>,
    /// The number of vertices used by each face. When using non-triangulated faces, the offset
    /// for the starting index of a face can be found by iterating through the `num_face_indices`
    /// until reaching the desired face, accumulating the number of vertices used so far.
    pub num_face_indices: Vec<u32>,
    /// Optional material id associated with this mesh. The material id indexes into the Vec of
    /// Materials loaded from the associated MTL file
    pub material_id: Option<usize>,
}

impl Mesh {
    /// Create a new empty mesh
    pub fn empty() -> Mesh {
        Mesh {
            positions: Vec::new(),
            normals: Vec::new(),
            texcoords: Vec::new(),
            indices: Vec::new(),
            num_face_indices: Vec::new(),
            material_id: None,
        }
    }
}

/// A named model within the file, associates some mesh with a name that was specified with an `o`
/// or `g` keyword in the OBJ file
#[derive(Clone, Debug)]
pub struct Model {
    /// Mesh used by the model containing its geometry
    pub mesh: Mesh,
    /// Name assigned to this mesh
    pub name: String,
}

impl Model {
    /// Create a new model, associating a name with a mesh
    pub fn new(mesh: Mesh, name: String) -> Model {
        Model { mesh, name }
    }
}

/// A material that may be referenced by one or more meshes. Standard MTL attributes are supported.
/// Any unrecognized parameters will be stored as key-value pairs in the `unknown_param` `HashMap`,
/// which maps the unknown parameter to the value set for it.
#[derive(Clone, Debug)]
pub struct Material {
    /// Material name as specified in the MTL file
    pub name: String,
    /// Ambient color of the material
    pub ambient: [f32; 3],
    /// Diffuse color of the material
    pub diffuse: [f32; 3],
    /// Specular color of the material
    pub specular: [f32; 3],
    /// Material shininess attribute
    pub shininess: f32,
    /// Dissolve attribute is the alpha term for the material. Referred to as dissolve since that's
    /// what the MTL file format docs refer to it as
    pub dissolve: f32,
    /// Optical density also known as index of refraction. Called optical_density in the MTL specc.
    /// Takes on a value between 0.001 and 10.0. 1.0 means light does not bend as it passed through
    /// the object.
    pub optical_density: f32,
    /// Name of the ambient texture file for the material. No path is pre-pended to the texture
    /// file names specified in the MTL file
    pub ambient_texture: String,
    /// Name of the diffuse texture file for the material. No path is pre-pended to the texture
    /// file names specified in the MTL file
    pub diffuse_texture: String,
    /// Name of the specular texture file for the material. No path is pre-pended to the texture
    /// file names specified in the MTL file
    pub specular_texture: String,
    /// Name of the normal map texture file for the material. No path is pre-pended to the texture
    /// file names specified in the MTL file
    pub normal_texture: String,
    /// Name of the shininess map texture file for the material. No path is pre-pended to the texture
    /// file names specified in the MTL file
    pub shininess_texture: String,
    /// Name of the alpha map texture file for the material. No path is pre-pended to the texture
    /// file names specified in the MTL file. Referred to as dissolve to match the MTL file format
    /// specification
    pub dissolve_texture: String,
    /// The illumnination model to use for this material. The different illumnination models are
    /// specified in http://paulbourke.net/dataformats/mtl/
    pub illumination_model: Option<u8>,
    /// Key value pairs of any unrecognized parameters encountered while parsing the material
    pub unknown_param: HashMap<String, String>,
}

impl Material {
    pub fn empty() -> Material {
        Material {
            name: String::new(),
            ambient: [0.0; 3],
            diffuse: [0.0; 3],
            specular: [0.0; 3],
            shininess: 0.0,
            dissolve: 1.0,
            optical_density: 1.0,
            ambient_texture: String::new(),
            diffuse_texture: String::new(),
            specular_texture: String::new(),
            normal_texture: String::new(),
            shininess_texture: String::new(),
            dissolve_texture: String::new(),
            illumination_model: None,
            unknown_param: HashMap::new(),
        }
    }
}

/// Possible errors that may occur while loading OBJ and MTL files
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum LoadError {
    OpenFileFailed,
    ReadError,
    UnrecognizedCharacter,
    PositionParseError,
    NormalParseError,
    TexcoordParseError,
    FaceParseError,
    MaterialParseError,
    InvalidObjectName,
    FaceVertexOutOfBounds,
    FaceTexCoordOutOfBounds,
    FaceNormalOutOfBounds,
    GenericFailure,
}

impl fmt::Display for LoadError {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        let msg = match *self {
            LoadError::OpenFileFailed => "open file failed",
            LoadError::ReadError => "read error",
            LoadError::UnrecognizedCharacter => "unrecognized character",
            LoadError::PositionParseError => "position parse error",
            LoadError::NormalParseError => "normal parse error",
            LoadError::TexcoordParseError => "texcoord parse error",
            LoadError::FaceParseError => "face parse error",
            LoadError::MaterialParseError => "material parse error",
            LoadError::InvalidObjectName => "invalid object name",
            LoadError::FaceVertexOutOfBounds => "face vertex index out of bounds",
            LoadError::FaceTexCoordOutOfBounds => "face texcoord index out of bounds",
            LoadError::FaceNormalOutOfBounds => "face normal index out of bounds",
            LoadError::GenericFailure => "generic failure",
        };

        f.write_str(msg)
    }
}

impl Error for LoadError {}

/// `LoadResult` is a result containing all the models loaded from the file and any materials from
/// referenced material libraries, or an error that occured while loading
pub type LoadResult = Result<(Vec<Model>, Vec<Material>), LoadError>;

/// `MTLLoadResult` is a result containing all the materials loaded from the file and a map of MTL
/// name to index or the error that occured while loading
pub type MTLLoadResult = Result<(Vec<Material>, HashMap<String, usize>), LoadError>;

/// Struct storing indices corresponding to the vertex
/// Some vertices may not have texcoords or normals, 0 is used to indicate this
/// as OBJ indices begin at 1
#[derive(Hash, Eq, PartialEq, PartialOrd, Ord, Debug, Copy, Clone)]
struct VertexIndices {
    pub v: isize,
    pub vt: isize,
    pub vn: isize,
}

impl VertexIndices {
    /// Parse the vertex indices from the face string
    /// Valid face strings are those that are valid for a Wavefront OBJ file
    /// Also handles relative face indices (negative values) which is why passing the number of
    /// positions, texcoords and normals is required
    /// Returns None if the face string is invalid
    fn parse(
        face_str: &str,
        pos_sz: usize,
        tex_sz: usize,
        norm_sz: usize,
    ) -> Option<VertexIndices> {
        let mut indices = [-1; 3];
        for i in face_str.split('/').enumerate() {
            // Catch case of v//vn where we'll find an empty string in one of our splits
            // since there are no texcoords for the mesh
            if !i.1.is_empty() {
                match isize::from_str(i.1) {
                    Ok(x) => {
                        // Handle relative indices
                        indices[i.0] = if x < 0 {
                            match i.0 {
                                0 => x + pos_sz as isize,
                                1 => x + tex_sz as isize,
                                2 => x + norm_sz as isize,
                                _ => panic!("Invalid number of elements for a face (> 3)!"),
                            }
                        } else {
                            x - 1
                        };
                    }
                    Err(_) => return None,
                }
            }
        }
        Some(VertexIndices {
            v: indices[0],
            vt: indices[1],
            vn: indices[2],
        })
    }
}

/// Enum representing either a quad or triangle face, storing indices for the face vertices
#[derive(Debug)]
enum Face {
    Line(VertexIndices, VertexIndices),
    Triangle(VertexIndices, VertexIndices, VertexIndices),
    Quad(VertexIndices, VertexIndices, VertexIndices, VertexIndices),
    Polygon(Vec<VertexIndices>),
}

/// Parse the floatn information from the words, words is an iterator over the float strings
/// Returns false if parsing failed
fn parse_floatn(val_str: SplitWhitespace, vals: &mut Vec<f32>, n: usize) -> bool {
    let sz = vals.len();
    for p in val_str {
        if sz + n == vals.len() {
            return true;
        }
        match FromStr::from_str(p) {
            Ok(x) => vals.push(x),
            Err(_) => return false,
        }
    }
    // Require that we found the desired number of floats
    sz + n == vals.len()
}

/// Parse the float3 into the array passed, returns false if parsing failed
fn parse_float3(val_str: SplitWhitespace, vals: &mut [f32; 3]) -> bool {
    for (i, p) in val_str.enumerate().take(3) {
        match FromStr::from_str(p) {
            Ok(x) => vals[i] = x,
            Err(_) => return false,
        }
    }
    true
}

/// Parse vertex indices for a face and append it to the list of faces passed
/// Also handles relative face indices (negative values) which is why passing the number of
/// positions, texcoords and normals is required
/// returns false if an error occured parsing the face
fn parse_face(
    face_str: SplitWhitespace,
    faces: &mut Vec<Face>,
    pos_sz: usize,
    tex_sz: usize,
    norm_sz: usize,
) -> bool {
    let mut indices = Vec::new();
    for f in face_str {
        match VertexIndices::parse(f, pos_sz, tex_sz, norm_sz) {
            Some(v) => indices.push(v),
            None => return false,
        }
    }
    // Check if we read a triangle or a quad face and push it on
    match indices.len() {
        2 => faces.push(Face::Line(indices[0], indices[1])),
        3 => faces.push(Face::Triangle(indices[0], indices[1], indices[2])),
        4 => faces.push(Face::Quad(indices[0], indices[1], indices[2], indices[3])),
        _ => faces.push(Face::Polygon(indices)),
    }
    true
}

/// Add a vertex to a mesh by either re-using an existing index (eg. it's in the `index_map`)
/// or appending the position, texcoord and normal as appropriate and creating a new vertex
fn add_vertex(
    mesh: &mut Mesh,
    index_map: &mut HashMap<VertexIndices, u32>,
    vert: &VertexIndices,
    pos: &[f32],
    texcoord: &[f32],
    normal: &[f32],
) -> Result<(), LoadError> {
    match index_map.get(vert) {
        Some(&i) => mesh.indices.push(i),
        None => {
            let v = vert.v as usize;
            if v * 3 + 2 >= pos.len() {
                return Err(LoadError::FaceVertexOutOfBounds);
            }
            // Add the vertex to the mesh
            mesh.positions.push(pos[v * 3]);
            mesh.positions.push(pos[v * 3 + 1]);
            mesh.positions.push(pos[v * 3 + 2]);
            if !texcoord.is_empty() && vert.vt > -1 {
                let vt = vert.vt as usize;
                if vt * 2 + 1 >= texcoord.len() {
                    return Err(LoadError::FaceTexCoordOutOfBounds);
                }
                mesh.texcoords.push(texcoord[vt * 2]);
                mesh.texcoords.push(texcoord[vt * 2 + 1]);
            }
            if !normal.is_empty() && vert.vn > -1 {
                let vn = vert.vn as usize;
                if vn * 3 + 2 >= normal.len() {
                    return Err(LoadError::FaceNormalOutOfBounds);
                }
                mesh.normals.push(normal[vn * 3]);
                mesh.normals.push(normal[vn * 3 + 1]);
                mesh.normals.push(normal[vn * 3 + 2]);
            }
            let next = index_map.len() as u32;
            mesh.indices.push(next);
            index_map.insert(*vert, next);
        }
    }
    Ok(())
}

/// Export a list of faces to a mesh and return it, converting quads to tris
fn export_faces(
    pos: &[f32],
    texcoord: &[f32],
    normal: &[f32],
    faces: &[Face],
    mat_id: Option<usize>,
    triangulate_faces: bool,
) -> Result<Mesh, LoadError> {
    let mut index_map = HashMap::new();
    let mut mesh = Mesh::empty();
    mesh.material_id = mat_id;
    for f in faces {
        // Optimized paths for Triangles and Quads, Polygon handles the general case of an unknown
        // length triangle fan
        match *f {
            Face::Line(ref a, ref b) => {
                add_vertex(&mut mesh, &mut index_map, a, pos, texcoord, normal)?;
                add_vertex(&mut mesh, &mut index_map, b, pos, texcoord, normal)?;
                mesh.num_face_indices.push(2);
            }
            Face::Triangle(ref a, ref b, ref c) => {
                add_vertex(&mut mesh, &mut index_map, a, pos, texcoord, normal)?;
                add_vertex(&mut mesh, &mut index_map, b, pos, texcoord, normal)?;
                add_vertex(&mut mesh, &mut index_map, c, pos, texcoord, normal)?;
                mesh.num_face_indices.push(3);
            }
            Face::Quad(ref a, ref b, ref c, ref d) => {
                if triangulate_faces {
                    add_vertex(&mut mesh, &mut index_map, a, pos, texcoord, normal)?;
                    add_vertex(&mut mesh, &mut index_map, b, pos, texcoord, normal)?;
                    add_vertex(&mut mesh, &mut index_map, c, pos, texcoord, normal)?;
                    mesh.num_face_indices.push(3);

                    add_vertex(&mut mesh, &mut index_map, a, pos, texcoord, normal)?;
                    add_vertex(&mut mesh, &mut index_map, c, pos, texcoord, normal)?;
                    add_vertex(&mut mesh, &mut index_map, d, pos, texcoord, normal)?;
                    mesh.num_face_indices.push(3);
                } else {
                    add_vertex(&mut mesh, &mut index_map, a, pos, texcoord, normal)?;
                    add_vertex(&mut mesh, &mut index_map, b, pos, texcoord, normal)?;
                    add_vertex(&mut mesh, &mut index_map, c, pos, texcoord, normal)?;
                    add_vertex(&mut mesh, &mut index_map, d, pos, texcoord, normal)?;
                    mesh.num_face_indices.push(4);
                }
            }
            Face::Polygon(ref indices) => {
                if triangulate_faces {
                    let a = &indices[0];
                    let mut b = &indices[1];
                    for c in indices.iter().skip(2) {
                        add_vertex(&mut mesh, &mut index_map, a, pos, texcoord, normal)?;
                        add_vertex(&mut mesh, &mut index_map, b, pos, texcoord, normal)?;
                        add_vertex(&mut mesh, &mut index_map, c, pos, texcoord, normal)?;
                        mesh.num_face_indices.push(3);
                        b = c;
                    }
                } else {
                    for i in indices.iter() {
                        add_vertex(&mut mesh, &mut index_map, i, pos, texcoord, normal)?;
                    }
                    mesh.num_face_indices.push(indices.len() as u32);
                }
            }
        }
    }
    Ok(mesh)
}

/// Load the various objects specified in the OBJ file and any associated MTL file
/// Returns a pair of Vecs containing the loaded models and materials from the file.
pub fn load_obj<P>(file_name: P, triangulate_faces: bool) -> LoadResult
where
    P: AsRef<Path> + fmt::Debug,
{
    let file = match File::open(file_name.as_ref()) {
        Ok(f) => f,
        Err(_e) => {
            #[cfg(feature = "log")]
            log::error!("load_obj - failed to open {:?} due to {}", file_name, _e);
            return Err(LoadError::OpenFileFailed);
        }
    };
    let mut reader = BufReader::new(file);
    load_obj_buf(&mut reader, triangulate_faces, |mat_path| {
        let full_path = if let Some(parent) = file_name.as_ref().parent() {
            parent.join(mat_path)
        } else {
            mat_path.to_owned()
        };

        self::load_mtl(&full_path)
    })
}

/// Load the materials defined in a MTL file
/// Returns a pair with a `Vec` holding all loaded materials and a `HashMap` containing a mapping of
/// material names to indices in the Vec.
pub fn load_mtl<P>(file_name: P) -> MTLLoadResult
where
    P: AsRef<Path> + fmt::Debug,
{
    let file = match File::open(file_name.as_ref()) {
        Ok(f) => f,
        Err(_e) => {
            #[cfg(feature = "log")]
            log::error!("load_mtl - failed to open {:?} due to {}", file_name, _e);
            return Err(LoadError::OpenFileFailed);
        }
    };
    let mut reader = BufReader::new(file);
    load_mtl_buf(&mut reader)
}

/// Load the various meshes in an OBJ buffer of some kind, e.g. a
/// network stream, text file already in memory or so on.
///
/// You must pass a "material loader" function, which will return a material
/// given a name. A trivial material loader may just look at the file
/// name and then call `load_mtl_buf` with the in-memory MTL file source.
/// Alternatively it could pass an MTL file in memory to `load_mtl_buf` to
/// parse materials from some buffer.
///
/// # Example
/// The test for `load_obj_buf` includes the OBJ and MTL files as strings
/// and uses a `Cursor` to provide a `BufRead` interface on the buffer.
///
/// ```
/// use std::env;
/// use std::fs::File;
/// use std::io::BufReader;
///
/// let dir = env::current_dir().unwrap();
/// let mut cornell_box_obj = dir.clone();
/// cornell_box_obj.push("cornell_box.obj");
/// let mut cornell_box_file = BufReader::new(File::open(cornell_box_obj.as_path()).unwrap());
///
/// let mut cornell_box_mtl1 = dir.clone();
/// cornell_box_mtl1.push("cornell_box.mtl");
///
/// let mut cornell_box_mtl2 = dir.clone();
/// cornell_box_mtl2.push("cornell_box2.mtl");
///
/// let m = tobj::load_obj_buf(&mut cornell_box_file, true, |p| {
///     match p.file_name().unwrap().to_str().unwrap() {
///         "cornell_box.mtl" => {
///             let f = File::open(cornell_box_mtl1.as_path()).unwrap();
///             tobj::load_mtl_buf(&mut BufReader::new(f))
///         },
///         "cornell_box2.mtl" => {
///             let f = File::open(cornell_box_mtl2.as_path()).unwrap();
///             tobj::load_mtl_buf(&mut BufReader::new(f))
///         },
///         _ => unreachable!(),
///     }
/// });
/// ```
pub fn load_obj_buf<B, ML>(
    reader: &mut B,
    triangulate_faces: bool,
    material_loader: ML,
) -> LoadResult
where
    B: BufRead,
    ML: Fn(&Path) -> MTLLoadResult,
{
    let mut models = Vec::new();
    let mut materials = Vec::new();
    let mut mat_map = HashMap::new();

    let mut tmp_pos = Vec::new();
    let mut tmp_texcoord = Vec::new();
    let mut tmp_normal = Vec::new();
    let mut tmp_faces: Vec<Face> = Vec::new();
    // name of the current object being parsed
    let mut name = "unnamed_object".to_owned();
    // material used by the current object being parsed
    let mut mat_id = None;
    for line in reader.lines() {
        let (line, mut words) = match line {
            Ok(ref line) => (&line[..], line[..].split_whitespace()),
            Err(_e) => {
                #[cfg(feature = "log")]
                log::error!("load_obj - failed to read line due to {}", _e);
                return Err(LoadError::ReadError);
            }
        };
        match words.next() {
            Some("#") | None => continue,
            Some("v") => {
                if !parse_floatn(words, &mut tmp_pos, 3) {
                    return Err(LoadError::PositionParseError);
                }
            }
            Some("vt") => {
                if !parse_floatn(words, &mut tmp_texcoord, 2) {
                    return Err(LoadError::TexcoordParseError);
                }
            }
            Some("vn") => {
                if !parse_floatn(words, &mut tmp_normal, 3) {
                    return Err(LoadError::NormalParseError);
                }
            }
            Some("f") | Some("l") => {
                if !parse_face(
                    words,
                    &mut tmp_faces,
                    tmp_pos.len() / 3,
                    tmp_texcoord.len() / 2,
                    tmp_normal.len() / 3,
                ) {
                    return Err(LoadError::FaceParseError);
                }
            }
            // Just treating object and group tags identically. Should there be different behavior
            // for them?
            Some("o") | Some("g") => {
                // If we were already parsing an object then a new object name
                // signals the end of the current one, so push it onto our list of objects
                if !tmp_faces.is_empty() {
                    models.push(Model::new(
                        export_faces(
                            &tmp_pos,
                            &tmp_texcoord,
                            &tmp_normal,
                            &tmp_faces,
                            mat_id,
                            triangulate_faces,
                        )?,
                        name,
                    ));
                    tmp_faces.clear();
                }
                name = line[1..].trim().to_owned();
                if name.is_empty() {
                    name = "unnamed_object".to_owned();
                }
            }
            Some("mtllib") => {
                if let Some(mtllib) = words.next() {
                    let mat_file = Path::new(mtllib).to_path_buf();
                    match material_loader(mat_file.as_path()) {
                        Ok((mut mats, map)) => {
                            // Merge the loaded material lib with any currently loaded ones, offsetting
                            // the indices of the appended materials by our current length
                            let mat_offset = materials.len();
                            materials.append(&mut mats);
                            for m in map {
                                mat_map.insert(m.0, m.1 + mat_offset);
                            }
                        }
                        Err(e) => return Err(e),
                    }
                } else {
                    return Err(LoadError::MaterialParseError);
                }
            }
            Some("usemtl") => {
                let mat_name = line[7..].trim().to_owned();
                if !mat_name.is_empty() {
                    let new_mat = mat_map.get(&mat_name).cloned();
                    // As materials are returned per-model, a new material within an object
                    // has to emit a new model with the same name but different material
                    if mat_id != new_mat && !tmp_faces.is_empty() {
                        models.push(Model::new(
                            export_faces(
                                &tmp_pos,
                                &tmp_texcoord,
                                &tmp_normal,
                                &tmp_faces,
                                mat_id,
                                triangulate_faces,
                            )?,
                            name.clone(),
                        ));
                        tmp_faces.clear();
                    }
                    if new_mat.is_none() {
                        #[cfg(feature = "log")]
                        log::warn!("Object {} refers to unfound material: {}", name, mat_name);
                    }
                    mat_id = new_mat;
                } else {
                    return Err(LoadError::MaterialParseError);
                }
            }
            // Just ignore unrecognized characters
            Some(_) => {}
        }
    }
    // For the last object in the file we won't encounter another object name to tell us when it's
    // done, so if we're parsing an object push the last one on the list as well
    models.push(Model::new(
        export_faces(
            &tmp_pos,
            &tmp_texcoord,
            &tmp_normal,
            &tmp_faces,
            mat_id,
            triangulate_faces,
        )?,
        name,
    ));
    Ok((models, materials))
}

/// Load the various materials in a MTL buffer
pub fn load_mtl_buf<B: BufRead>(reader: &mut B) -> MTLLoadResult {
    let mut materials = Vec::new();
    let mut mat_map = HashMap::new();
    // The current material being parsed
    let mut cur_mat = Material::empty();
    for line in reader.lines() {
        let (line, mut words) = match line {
            Ok(ref line) => (line.trim(), line[..].split_whitespace()),
            Err(_e) => {
                #[cfg(feature = "log")]
                log::error!("load_obj - failed to read line due to {}", _e);
                return Err(LoadError::ReadError);
            }
        };
        match words.next() {
            Some("#") | None => continue,
            Some("newmtl") => {
                // If we were passing a material save it out to our vector
                if !cur_mat.name.is_empty() {
                    mat_map.insert(cur_mat.name.clone(), materials.len());
                    materials.push(cur_mat);
                }
                cur_mat = Material::empty();
                cur_mat.name = line[6..].trim().to_owned();
                if cur_mat.name.is_empty() {
                    return Err(LoadError::InvalidObjectName);
                }
            }
            Some("Ka") => {
                if !parse_float3(words, &mut cur_mat.ambient) {
                    return Err(LoadError::MaterialParseError);
                }
            }
            Some("Kd") => {
                if !parse_float3(words, &mut cur_mat.diffuse) {
                    return Err(LoadError::MaterialParseError);
                }
            }
            Some("Ks") => {
                if !parse_float3(words, &mut cur_mat.specular) {
                    return Err(LoadError::MaterialParseError);
                }
            }
            Some("Ns") => {
                if let Some(p) = words.next() {
                    match FromStr::from_str(p) {
                        Ok(x) => cur_mat.shininess = x,
                        Err(_) => return Err(LoadError::MaterialParseError),
                    }
                } else {
                    return Err(LoadError::MaterialParseError);
                }
            }
            Some("Ni") => {
                if let Some(p) = words.next() {
                    match FromStr::from_str(p) {
                        Ok(x) => cur_mat.optical_density = x,
                        Err(_) => return Err(LoadError::MaterialParseError),
                    }
                } else {
                    return Err(LoadError::MaterialParseError);
                }
            }
            Some("d") => {
                if let Some(p) = words.next() {
                    match FromStr::from_str(p) {
                        Ok(x) => cur_mat.dissolve = x,
                        Err(_) => return Err(LoadError::MaterialParseError),
                    }
                } else {
                    return Err(LoadError::MaterialParseError);
                }
            }
            Some("map_Ka") => match line.get(6..).map(str::trim) {
                Some("") | None => return Err(LoadError::MaterialParseError),
                Some(tex) => cur_mat.ambient_texture = tex.to_owned(),
            },
            Some("map_Kd") => match line.get(6..).map(str::trim) {
                Some("") | None => return Err(LoadError::MaterialParseError),
                Some(tex) => cur_mat.diffuse_texture = tex.to_owned(),
            },
            Some("map_Ks") => match line.get(6..).map(str::trim) {
                Some("") | None => return Err(LoadError::MaterialParseError),
                Some(tex) => cur_mat.specular_texture = tex.to_owned(),
            },
            Some("map_Bump") | Some("map_bump") => match line.get(8..).map(str::trim) {
                Some("") | None => return Err(LoadError::MaterialParseError),
                Some(tex) => cur_mat.normal_texture = tex.to_owned(),
            },
            Some("map_Ns") | Some("map_ns") | Some("map_NS") => {
                match line.get(6..).map(str::trim) {
                    Some("") | None => return Err(LoadError::MaterialParseError),
                    Some(tex) => cur_mat.shininess_texture = tex.to_owned(),
                }
            }
            Some("bump") => match line.get(4..).map(str::trim) {
                Some("") | None => return Err(LoadError::MaterialParseError),
                Some(tex) => cur_mat.normal_texture = tex.to_owned(),
            },
            Some("map_d") => match line.get(5..).map(str::trim) {
                Some("") | None => return Err(LoadError::MaterialParseError),
                Some(tex) => cur_mat.dissolve_texture = tex.to_owned(),
            },
            Some("illum") => {
                if let Some(p) = words.next() {
                    match FromStr::from_str(p) {
                        Ok(x) => cur_mat.illumination_model = Some(x),
                        Err(_) => return Err(LoadError::MaterialParseError),
                    }
                } else {
                    return Err(LoadError::MaterialParseError);
                }
            }
            Some(unknown) => {
                if !unknown.is_empty() {
                    let param = line[unknown.len()..].trim().to_owned();
                    cur_mat.unknown_param.insert(unknown.to_owned(), param);
                }
            }
        }
    }
    // Finalize the last material we were parsing
    if !cur_mat.name.is_empty() {
        mat_map.insert(cur_mat.name.clone(), materials.len());
        materials.push(cur_mat);
    }
    Ok((materials, mat_map))
}