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use format::compressed::Variant;
use format::{Conventional, Compressed, Diagonal};
use {Element, Size};

impl<'l, T: Element> From<&'l Conventional<T>> for Compressed<T> {
    fn from(conventional: &'l Conventional<T>) -> Self {
        let (rows, columns) = conventional.dimensions();
        let mut matrix = Compressed::new((rows, columns), Variant::Column);
        for (k, &value) in conventional.values.iter().enumerate() {
            if !value.is_zero() {
                matrix.set((k % rows, k / rows), value);
            }
        }
        matrix
    }
}

impl<T: Element> From<Conventional<T>> for Compressed<T> {
    #[inline]
    fn from(matrix: Conventional<T>) -> Self {
        (&matrix).into()
    }
}

impl<'l, T: Element> From<&'l Compressed<T>> for Conventional<T> {
    fn from(matrix: &'l Compressed<T>) -> Self {
        let &Compressed {
            rows, columns, variant, ref values, ref indices, ref offsets, ..
        } = validate!(matrix);

        let mut matrix = Conventional::new((rows, columns));
        match variant {
            Variant::Row => for i in 0..rows {
                for k in offsets[i]..offsets[i + 1] {
                    matrix.values[indices[k] * rows + i] = values[k];
                }
            },
            Variant::Column => for j in 0..columns {
                for k in offsets[j]..offsets[j + 1] {
                    matrix.values[j * rows + indices[k]] = values[k];
                }
            },
        }

        matrix
    }
}

impl<T: Element> From<Compressed<T>> for Conventional<T> {
    #[inline]
    fn from(matrix: Compressed<T>) -> Self {
        (&matrix).into()
    }
}

impl<'l, T: Element> From<&'l Diagonal<T>> for Compressed<T> {
    #[inline]
    fn from(matrix: &'l Diagonal<T>) -> Self {
        matrix.clone().into()
    }
}

impl<T: Element> From<Diagonal<T>> for Compressed<T> {
    fn from(matrix: Diagonal<T>) -> Self {
        let Diagonal { rows, columns, values } = validate!(matrix);
        let nonzeros = values.len();
        let indices = (0..nonzeros).collect();
        let offsets = (0..(columns + 1)).map(|i| {
            if i < nonzeros { i } else { nonzeros }
        }).collect();
        new!(rows, columns, nonzeros, Variant::Column, values, indices, offsets)
    }
}

#[cfg(test)]
mod tests {
    use format::compressed::Variant;
    use prelude::*;

    #[test]
    fn from_conventional() {
        let matrix = Conventional::from_vec((5, 3), matrix![
            0.0, 0.0, 0.0;
            1.0, 0.0, 0.0;
            0.0, 0.0, 0.0;
            0.0, 2.0, 0.0;
            0.0, 3.0, 4.0;
        ]);

        let matrix = Compressed::from(matrix);

        assert_eq!(matrix, new!(5, 3, 4, Variant::Column, vec![1.0, 2.0, 3.0, 4.0],
                                vec![1, 3, 4, 4], vec![0, 1, 3, 4]));
    }

    #[test]
    fn from_diagonal_tall() {
        let matrix = Compressed::from(Diagonal::from_vec((5, 3), vec![1.0, 2.0, 0.0]));

        assert_eq!(matrix, new!(5, 3, 3, Variant::Column, vec![1.0, 2.0, 0.0],
                                vec![0, 1, 2], vec![0, 1, 2, 3]));
    }

    #[test]
    fn from_diagonal_wide() {
        let matrix = Compressed::from(Diagonal::from_vec((3, 5), vec![1.0, 0.0, 3.0]));

        assert_eq!(matrix, new!(3, 5, 3, Variant::Column, vec![1.0, 0.0, 3.0],
                                vec![0, 1, 2], vec![0, 1, 2, 3, 3, 3]));
    }

    #[test]
    fn into_conventional() {
        let matrix = new!(5, 3, 3, Variant::Column, vec![1.0, 2.0, 3.0],
                          vec![0, 1, 2], vec![0, 1, 2, 3]);

        let matrix = Conventional::from(matrix);

        assert_eq!(&*matrix, &*matrix![
            1.0, 0.0, 0.0;
            0.0, 2.0, 0.0;
            0.0, 0.0, 3.0;
            0.0, 0.0, 0.0;
            0.0, 0.0, 0.0;
        ]);
    }
}