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use core::*;
use geometry::{Space, Vector};
use std::collections::HashMap;
use super::{Projection, CandidateFeature};

/// Trait for basis projectors.
pub trait Projector<I: ?Sized>: Space<Value = Projection> {
    /// Project data from an input space onto the basis.
    fn project(&self, input: &I) -> Projection;

    /// Project data from an input space onto the basis and convert into a raw,
    /// dense vector.
    fn project_expanded(&self, input: &I) -> DenseT { self.project(input).expanded(self.dim()) }
}

/// Trait for projectors with adaptive bases.
pub trait AdaptiveProjector<I: ?Sized>: Projector<I> {
    fn discover(&mut self, input: &I, error: f64) -> Option<HashMap<usize, IndexSet>>;
    fn add_feature(&mut self, feature: CandidateFeature) -> Option<(usize, IndexSet)>;
}

impl<P: Projector<[f64]>> Projector<Vec<f64>> for P {
    fn project(&self, input: &Vec<f64>) -> Projection { Projector::<[f64]>::project(self, &input) }
}

impl<P: Projector<[f64]>> Projector<Vector<f64>> for P {
    fn project(&self, input: &Vector<f64>) -> Projection {
        Projector::<[f64]>::project(self, input.as_slice().unwrap())
    }
}

macro_rules! impl_fixed {
    ($($n:expr),*) => {
        $(
            impl<P: Projector<[f64]>> Projector<[f64; $n]> for P {
                fn project(&self, input: &[f64; $n]) -> Projection {
                    Projector::<[f64]>::project(self, input)
                }
            }
        )*
    }
}

impl_fixed!(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24);