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use crate::elements::view::ColChar;

/// A Face contains indices to a mesh's collection of vertices and a `ColChar` to fill the face. Indices should be arranged in a clockwise order, as if they appear counter-clockwise when rendering they will not be rendered at all (this is how gemini-engine handles backface culling and maximises performance)
#[derive(Debug, Clone)]
pub struct IndexFace {
    /// The vertex indices of the face
    pub v_indices: Vec<usize>,
    /// The desired appearance of the face when rendered
    pub fill_char: ColChar,
}

impl IndexFace {
    /// Create a new face with the given indexes and [`ColChar`]
    #[must_use]
    pub const fn new(v_indices: Vec<usize>, fill_char: ColChar) -> Self {
        Self {
            v_indices,
            fill_char,
        }
    }

    /// Returns a vector with the elements found at the vertex indices of the given slice
    pub fn index_into<T: Copy>(&self, vertices: &[T]) -> Vec<T> {
        // TODO: return `None` if the input slice isnt large enough
        self.v_indices.iter().map(|vi| vertices[*vi]).collect()
    }
}