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use crate::imp_prelude::*;
use crate::Zip;
use approx::{AbsDiffEq, RelativeEq, UlpsEq};

/// **Requires crate feature `"approx"`**
impl<A, B, S, S2, D> AbsDiffEq<ArrayBase<S2, D>> for ArrayBase<S, D>
where
    A: AbsDiffEq<B>,
    A::Epsilon: Clone,
    S: Data<Elem = A>,
    S2: Data<Elem = B>,
    D: Dimension,
{
    type Epsilon = A::Epsilon;

    fn default_epsilon() -> A::Epsilon {
        A::default_epsilon()
    }

    fn abs_diff_eq(&self, other: &ArrayBase<S2, D>, epsilon: A::Epsilon) -> bool {
        if self.shape() != other.shape() {
            return false;
        }

        Zip::from(self)
            .and(other)
            .all(move |a, b| A::abs_diff_eq(a, b, epsilon.clone()))
    }
}

/// **Requires crate feature `"approx"`**
impl<A, B, S, S2, D> RelativeEq<ArrayBase<S2, D>> for ArrayBase<S, D>
where
    A: RelativeEq<B>,
    A::Epsilon: Clone,
    S: Data<Elem = A>,
    S2: Data<Elem = B>,
    D: Dimension,
{
    fn default_max_relative() -> A::Epsilon {
        A::default_max_relative()
    }

    fn relative_eq(
        &self,
        other: &ArrayBase<S2, D>,
        epsilon: A::Epsilon,
        max_relative: A::Epsilon,
    ) -> bool {
        if self.shape() != other.shape() {
            return false;
        }

        Zip::from(self)
            .and(other)
            .all(move |a, b| A::relative_eq(a, b, epsilon.clone(), max_relative.clone()))
    }
}

/// **Requires crate feature `"approx"`**
impl<A, B, S, S2, D> UlpsEq<ArrayBase<S2, D>> for ArrayBase<S, D>
where
    A: UlpsEq<B>,
    A::Epsilon: Clone,
    S: Data<Elem = A>,
    S2: Data<Elem = B>,
    D: Dimension,
{
    fn default_max_ulps() -> u32 {
        A::default_max_ulps()
    }

    fn ulps_eq(&self, other: &ArrayBase<S2, D>, epsilon: A::Epsilon, max_ulps: u32) -> bool {
        if self.shape() != other.shape() {
            return false;
        }

        Zip::from(self)
            .and(other)
            .all(move |a, b| A::ulps_eq(a, b, epsilon.clone(), max_ulps))
    }
}

impl<A, S, D> ArrayBase<S, D>
where
    S: Data<Elem = A>,
    D: Dimension,
{
    /// A test for equality that uses the elementwise absolute difference to compute the
    /// approximate equality of two arrays.
    ///
    /// **Requires crate feature `"approx"`**
    pub fn abs_diff_eq<S2>(&self, other: &ArrayBase<S2, D>, epsilon: A::Epsilon) -> bool
    where
        A: AbsDiffEq<S2::Elem>,
        A::Epsilon: Clone,
        S2: Data,
    {
        <Self as AbsDiffEq<_>>::abs_diff_eq(self, other, epsilon)
    }

    /// A test for equality that uses an elementwise relative comparison if the values are far
    /// apart; and the absolute difference otherwise.
    ///
    /// **Requires crate feature `"approx"`**
    pub fn relative_eq<S2>(
        &self,
        other: &ArrayBase<S2, D>,
        epsilon: A::Epsilon,
        max_relative: A::Epsilon,
    ) -> bool
    where
        A: RelativeEq<S2::Elem>,
        A::Epsilon: Clone,
        S2: Data
    {
        <Self as RelativeEq<_>>::relative_eq(self, other, epsilon, max_relative)
    }
}


#[cfg(test)]
mod tests {
    use crate::prelude::*;
    use alloc::vec;
    use approx::{
        assert_abs_diff_eq, assert_abs_diff_ne, assert_relative_eq, assert_relative_ne,
        assert_ulps_eq, assert_ulps_ne,
    };

    #[test]
    fn abs_diff_eq() {
        let a: Array2<f32> = array![[0., 2.], [-0.000010001, 100000000.]];
        let mut b: Array2<f32> = array![[0., 1.], [-0.000010002, 100000001.]];
        assert_abs_diff_ne!(a, b);
        b[(0, 1)] = 2.;
        assert_abs_diff_eq!(a, b);

        // Check epsilon.
        assert_abs_diff_eq!(array![0.0f32], array![1e-40f32], epsilon = 1e-40f32);
        assert_abs_diff_ne!(array![0.0f32], array![1e-40f32], epsilon = 1e-41f32);

        // Make sure we can compare different shapes without failure.
        let c = array![[1., 2.]];
        assert_abs_diff_ne!(a, c);
    }

    #[test]
    fn relative_eq() {
        let a: Array2<f32> = array![[1., 2.], [-0.000010001, 100000000.]];
        let mut b: Array2<f32> = array![[1., 1.], [-0.000010002, 100000001.]];
        assert_relative_ne!(a, b);
        b[(0, 1)] = 2.;
        assert_relative_eq!(a, b);

        // Check epsilon.
        assert_relative_eq!(array![0.0f32], array![1e-40f32], epsilon = 1e-40f32);
        assert_relative_ne!(array![0.0f32], array![1e-40f32], epsilon = 1e-41f32);

        // Make sure we can compare different shapes without failure.
        let c = array![[1., 2.]];
        assert_relative_ne!(a, c);
    }

    #[test]
    fn ulps_eq() {
        let a: Array2<f32> = array![[1., 2.], [-0.000010001, 100000000.]];
        let mut b: Array2<f32> = array![[1., 1.], [-0.000010002, 100000001.]];
        assert_ulps_ne!(a, b);
        b[(0, 1)] = 2.;
        assert_ulps_eq!(a, b);

        // Check epsilon.
        assert_ulps_eq!(array![0.0f32], array![1e-40f32], epsilon = 1e-40f32);
        assert_ulps_ne!(array![0.0f32], array![1e-40f32], epsilon = 1e-41f32);

        // Make sure we can compare different shapes without failure.
        let c = array![[1., 2.]];
        assert_ulps_ne!(a, c);
    }
}