//! The convert module.
//!
//! Contains implementations of `std::convert::From`
//! for Matrix and Vector types.

use std::convert::From;

use libnum::{Zero, ToPrimitive, NumCast};

use error::{Error, ErrorKind};

use super::matrix::{DiagOffset, Matrix, MatrixSlice, MatrixSliceMut, BaseMatrix,
                    Row, RowMut, Column, ColumnMut};
use super::vector::Vector;

impl<T> From<Vec<T>> for Vector<T> {
    fn from(vec: Vec<T>) -> Self {
        Vector::new(vec)
    }
}

impl<'a, T> From<&'a [T]> for Vector<T>
    where T: Clone
{
    fn from(slice: &'a [T]) -> Self {
        Vector::new(slice.to_owned())
    }
}

impl<T> From<Vector<T>> for Matrix<T> {
    fn from(vector: Vector<T>) -> Self {
        Matrix::new(vector.size(), 1, vector.into_vec())
    }
}

macro_rules! impl_matrix_from {
    ($slice_type:ident) => {
        impl<'a, T: Copy> From<$slice_type<'a, T>> for Matrix<T> {
            fn from(slice: $slice_type<'a, T>) -> Self {
                slice.row_iter().collect::<Matrix<T>>()
            }
        }
    }
}

impl_matrix_from!(MatrixSlice);
impl_matrix_from!(MatrixSliceMut);


macro_rules! impl_diag_offset_from {
    ($signed_type:ty) => {
impl From<$signed_type> for DiagOffset {
    fn from(int: $signed_type) -> Self {
        if int.is_zero() {
            DiagOffset::Main
        } else if int.is_positive() {
            DiagOffset::Above(int as usize)
        } else {
            DiagOffset::Below((-int) as usize)
        }
    }
}
    }
}

impl_diag_offset_from!(i8);
impl_diag_offset_from!(i16);
impl_diag_offset_from!(i32);
impl_diag_offset_from!(i64);
impl_diag_offset_from!(isize);

impl<T: ToPrimitive> Matrix<T> {
    /// Attempts to convert the matrix into a new matrix of different scalar type.
    ///
    /// # Failures
    /// - One or more of the elements in the matrix cannot be converted into
    ///   the new type.
    pub fn try_into<U: NumCast>(self) -> Result<Matrix<U>, Error> {
        let (m, n) = (self.rows(), self.cols());
        let ref make_error = || {
            Error::new(ErrorKind::ScalarConversionFailure,
                       "Failed to convert between scalar types.")
        };
        let converted_data = self.into_vec()
            .into_iter()
            .map(|x| U::from(x).ok_or_else(make_error))
            .collect::<Result<Vec<_>, Error>>();

        Ok(Matrix::<U>::new(m, n, try!(converted_data)))
    }
}

macro_rules! impl_row_to_vector (
    ($t:ident) => (

impl<'a, T: Clone> From<$t<'a, T>> for Vector<T> {
    fn from(row: $t<'a, T>) -> Self {
        Vector::new(row.raw_slice())
    }
}

    );
);
impl_row_to_vector!(Row);
impl_row_to_vector!(RowMut);

macro_rules! impl_column_to_vector (
    ($t:ident) => (

impl<'a, T: Clone> From<$t<'a, T>> for Vector<T> {
    fn from(column: $t<'a, T>) -> Self {
        column.iter().cloned().collect::<Self>()
    }
}

    );
);
impl_column_to_vector!(Column);
impl_column_to_vector!(ColumnMut);


#[cfg(test)]
mod tests {
    use matrix::{DiagOffset, Matrix, MatrixSlice, MatrixSliceMut,
                 BaseMatrix, BaseMatrixMut};
    use vector::Vector;

    #[test]
    fn inner_product_as_matrix_multiplication() {
        let u: Vector<f32> = vector![1., 2., 3.];
        let v: Vector<f32> = vector![3., 4., 5.];
        let dot_product = u.dot(&v);

        let um: Matrix<f32> = u.into();
        let vm: Matrix<f32> = v.into();
        let matrix_product = um.transpose() * vm;

        assert_eq!(dot_product, matrix_product.data()[0]);
    }

    #[test]
    fn matrix_from_slice() {
        let mut a = Matrix::new(3, 3, vec![2.0; 9]);

        {
            let b = MatrixSlice::from_matrix(&a, [1, 1], 2, 2);
            let c = Matrix::from(b);
            assert_eq!(c.rows(), 2);
            assert_eq!(c.cols(), 2);
        }

        let d = MatrixSliceMut::from_matrix(&mut a, [1, 1], 2, 2);
        let e = Matrix::from(d);
        assert_eq!(e.rows(), 2);
        assert_eq!(e.cols(), 2);
    }

    #[test]
    fn diag_offset_from_int() {
        let a: DiagOffset = 3.into();
        assert_eq!(a, DiagOffset::Above(3));
        let a: DiagOffset = (-3).into();
        assert_eq!(a, DiagOffset::Below(3));
        let a: DiagOffset = 0.into();
        assert_eq!(a, DiagOffset::Main);
    }

    #[test]
    fn try_into_empty_matrix() {
        {
            let x: Matrix<f64> = matrix![];
            let y: Matrix<f32> = x.try_into().unwrap();
            assert_matrix_eq!(y, matrix![]);
        }

        {
            let x: Matrix<u64> = matrix![];
            let y: Matrix<u32> = x.try_into().unwrap();
            assert_matrix_eq!(y, matrix![]);
        }

        {
            let x: Matrix<f64> = matrix![];
            let y: Matrix<u64> = x.try_into().unwrap();
            assert_matrix_eq!(y, matrix![]);
        }

        {
            let x: Matrix<u8> = matrix![];
            let y: Matrix<u64> = x.try_into().unwrap();
            assert_matrix_eq!(y, matrix![]);
        }
    }

    #[test]
    fn try_into_f64_to_i64() {
        let x: Matrix<f64> = matrix![ 1.0, 2.0;
                                     -3.0, 4.0];
        let y: Matrix<i64> = x.try_into().unwrap();
        let expected = matrix![ 1, 2;
                               -3, 4];
        assert_matrix_eq!(y, expected);
    }

    #[test]
    fn try_into_f64_to_u64() {
        let x: Matrix<f64> = matrix![ 1.0, 2.0;
                                      3.0, 4.0];
        let y: Matrix<u64> = x.try_into().unwrap();
        let expected = matrix![ 1, 2;
                                3, 4];
        assert_matrix_eq!(y, expected);
    }

    #[test]
    fn try_into_i64_to_f64() {
        {
            let x: Matrix<i64> = matrix![ 1, 2;
                                         -3, 4];
            let y: Matrix<f64> = x.try_into().unwrap();

            let expected = matrix![ 1.0, 2.0;
                                   -3.0, 4.0];
            assert_matrix_eq!(y, expected);
        }

        {
            // Recall that f64 cannot exactly represent integers of sufficiently
            // large absolute value. Yet, Rust will cast and round as necessary,
            // so we only check that the result is Ok.
            {
                let x: Matrix<i64> = matrix![1, 2, i64::max_value()];
                let y_result = x.try_into::<f64>();
                assert!(y_result.is_ok());
            }

            {
                let x: Matrix<i64> = matrix![1, 2, i64::min_value()];
                let y_result = x.try_into::<f64>();
                assert!(y_result.is_ok());
            }
        }
    }

    #[test]
    fn try_into_u64_to_f64() {
        {
            let x: Matrix<u64> = matrix![ 1, 2;
                                          3, 4];
            let y: Matrix<f64> = x.try_into().unwrap();

            let expected = matrix![ 1.0, 2.0;
                                    3.0, 4.0];
            assert_matrix_eq!(y, expected);
        }

        {
            // Recall that f64 cannot exactly represent integers of sufficiently
            // large absolute value. Yet, Rust will cast and round as necessary,
            // so we only check that the result is Ok.
            {
                let x: Matrix<u64> = matrix![1, 2, u64::max_value()];
                let y_result = x.try_into::<f64>();
                assert!(y_result.is_ok());
            }
        }
    }

    #[test]
    fn try_into_signed_unsigned() {
        {
            let x: Matrix<u64> = matrix![ 1, 2;
                                          3, 4];
            let y: Matrix<i64> = x.try_into().unwrap();

            let expected = matrix![ 1, 2;
                                    3, 4];
            assert_matrix_eq!(y, expected);
        }

        {
            let x: Matrix<i64> = matrix![ 1, 2;
                                          3, 4];
            let y: Matrix<u64> = x.try_into().unwrap();

            let expected = matrix![ 1, 2;
                                    3, 4];
            assert_matrix_eq!(y, expected);
        }

        {
            // Cannot cast negative values into unsigned
            let x = matrix![ 1, -2;
                             3,  4];
            let y_result = x.try_into::<u64>();
            assert!(y_result.is_err());
        }
    }

    #[test]
    fn test_row_convert() {
        let a: Matrix<i64> = matrix![1, 2, 3, 4;
                                     5, 6, 7, 8;
                                     9, 10, 11, 12];
        let row = a.row(1);
        let v: Vector<i64> = row.into();
        assert_eq!(v, vector![5, 6, 7, 8]);

        let row = a.row(2);
        let v = Vector::from(row);
        assert_eq!(v, vector![9, 10, 11, 12]);
    }

    #[test]
    fn test_row_convert_mut() {
        let mut a: Matrix<i64> = matrix![1, 2, 3, 4;
                                         5, 6, 7, 8;
                                         9, 10, 11, 12];

        let row = a.row_mut(1);
        let v: Vector<i64> = row.into();
        assert_eq!(v, vector![5, 6, 7, 8]);

        let mut a: Matrix<i64> = matrix![1, 2, 3, 4;
                                         5, 6, 7, 8;
                                         9, 10, 11, 12];
        let row = a.row_mut(2);
        let v = Vector::from(row);
        assert_eq!(v, vector![9, 10, 11, 12]);
    }

    #[test]
    fn test_column_convert() {
        let a: Matrix<i64> = matrix![1, 2, 3, 4;
                                     5, 6, 7, 8;
                                     9, 10, 11, 12];
        let row = a.col(1);
        let v: Vector<i64> = row.into();
        assert_eq!(v, vector![2, 6, 10]);

        let row = a.col(2);
        let v = Vector::from(row);
        assert_eq!(v, vector![3, 7, 11]);
    }

    #[test]
    fn test_column_convert_mut() {
        let mut a: Matrix<i64> = matrix![1, 2, 3, 4;
                                         5, 6, 7, 8;
                                         9, 10, 11, 12];

        let row = a.col_mut(1);
        let v: Vector<i64> = row.into();
        assert_eq!(v, vector![2, 6, 10]);

        let mut a: Matrix<i64> = matrix![1, 2, 3, 4;
                                         5, 6, 7, 8;
                                         9, 10, 11, 12];
        let row = a.col_mut(2);
        let v = Vector::from(row);
        assert_eq!(v, vector![3, 7, 11]);
    }
}