//! This module contains the structs needed to build faces.

use std::fmt;

#[derive(Copy, Clone, PartialEq)]
/// The indices needed for each vertex of a face.
pub struct FaceVertex {

    /// The index of the vertex.
    pub vertex: usize,

    /// The index of the texture coordinate, None if there is no texture coordinate.
    pub texture_coordinate: Option<usize>,

    /// The index of the normal, None if there is no normal.
    pub normal: Option<usize>,
}

impl FaceVertex {

    /// Creates a new face vertex from its attributes.
    pub fn new(vertex: usize, texture_coordinate: Option<usize>, normal: Option<usize>) -> FaceVertex {
        FaceVertex {
            vertex: vertex,
            texture_coordinate: texture_coordinate,
            normal: normal,
        }
    }

}

impl fmt::Debug for FaceVertex {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {

        let texture_coordinate = if let Some(tc) = self.texture_coordinate {
            tc.to_string()
        } else {
            "".to_owned()
        };

        let normal = if let Some(n) = self.normal {
            n.to_string()
        } else {
            "".to_owned()
        };

        write!(formatter, "{}/{}/{}", self.vertex, texture_coordinate, normal)
    }
}

#[derive(Clone, PartialEq, Debug)]
/// A 3D Face.
///
/// It contains exactly 3 face vertices, and the name of the corresponding material.
pub struct Face {

    /// The first vertex of the face.
    pub a: FaceVertex,

    /// The second vertex of the face.
    pub b: FaceVertex,

    /// The third vertex of the face.
    pub c: FaceVertex,

    /// The name of the material, None if no material is specified.
    pub material_name: Option<String>,

    /// Id of the face, number of the face in the original file.
    pub id: Option<usize>,

}

impl Face {

    /// Creates a new face from its attributes.
    ///
    /// Material name defaults to None.
    pub fn new(a: FaceVertex, b: FaceVertex, c: FaceVertex) -> Face {
        Face {
            a: a,
            b: b,
            c: c,
            material_name: None,
            id: None,
        }
    }
}