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use crate::{
    basis::Composable,
    core::{Features, Projector},
    geometry::{Card, Space},
};

/// Fixed uniform basis projector.
#[derive(Clone, Copy, Serialize, Deserialize, Debug)]
pub struct Constant {
    n_features: usize,
    value: f64,
}

impl Constant {
    pub fn new(n_features: usize, value: f64) -> Self {
        Constant {
            n_features: n_features,
            value: value,
        }
    }

    pub fn zeros(n_features: usize) -> Self { Constant::new(n_features, 0.0) }

    pub fn ones(n_features: usize) -> Self { Constant::new(n_features, 1.0) }
}

impl Space for Constant {
    type Value = Features;

    fn dim(&self) -> usize { self.n_features }

    fn card(&self) -> Card { unimplemented!() }
}

impl<I: ?Sized> Projector<I> for Constant {
    fn project(&self, _: &I) -> Features { vec![self.value; self.n_features].into() }
}

impl Composable for Constant {}

/// Fixed uniform basis projector.
#[derive(Clone)]
pub struct Indices {
    n_features: usize,
    active_features: Vec<usize>,
}

impl Indices {
    pub fn new(n_features: usize, active_features: Vec<usize>) -> Self {
        Indices {
            n_features,
            active_features,
        }
    }
}

impl Space for Indices {
    type Value = Features;

    fn dim(&self) -> usize { self.n_features }

    fn card(&self) -> Card { unimplemented!() }
}

impl<I: ?Sized> Projector<I> for Indices {
    fn project(&self, _: &I) -> Features { self.active_features.iter().cloned().collect() }
}

impl Composable for Indices {}

#[cfg(test)]
mod tests {
    use super::*;
    use quickcheck::quickcheck;

    #[test]
    fn test_project_zeros() {
        fn prop_output(length: usize, input: Vec<f64>) -> bool {
            match Constant::zeros(length).project(&input) {
                Features::Sparse(_) => false,
                Features::Dense(activations) => {
                    activations.len() == length && activations.into_iter().all(|&v| v == 0.0)
                },
            }
        }

        quickcheck(prop_output as fn(usize, Vec<f64>) -> bool);
    }

    #[test]
    fn test_project_ones() {
        fn prop_output(length: usize, input: Vec<f64>) -> bool {
            match Constant::ones(length).project(&input) {
                Features::Sparse(_) => false,
                Features::Dense(activations) => {
                    activations.len() == length && activations.into_iter().all(|&v| v == 1.0)
                },
            }
        }

        quickcheck(prop_output as fn(usize, Vec<f64>) -> bool);
    }

    #[test]
    fn test_project_general() {
        fn prop_output(length: usize, value: f64, input: Vec<f64>) -> bool {
            match Constant::new(length, value).project(&input) {
                Features::Sparse(_) => false,
                Features::Dense(activations) => {
                    activations.len() == length && activations.into_iter().all(|&v| v == value)
                },
            }
        }

        quickcheck(prop_output as fn(usize, f64, Vec<f64>) -> bool);
    }
}