use num::{Zero, One};
use std::cmp;
use std::ptr;

use core::{DefaultAllocator, Scalar, Matrix, DMatrix, MatrixMN, Vector};
use core::dimension::{Dim, DimName, DimSub, DimDiff, DimAdd, DimSum, DimMin, DimMinimum, U1, Dynamic};
use core::constraint::{ShapeConstraint, DimEq};
use core::allocator::{Allocator, Reallocator};
use core::storage::{Storage, StorageMut};

impl<N: Scalar + Zero, R: Dim, C: Dim, S: Storage<N, R, C>> Matrix<N, R, C, S> {
    /// Extracts the upper triangular part of this matrix (including the diagonal).
    #[inline]
    pub fn upper_triangle(&self) -> MatrixMN<N, R, C>
        where DefaultAllocator: Allocator<N, R, C> {
        let mut res = self.clone_owned();
        res.fill_lower_triangle(N::zero(), 1);

        res
    }

    /// Extracts the upper triangular part of this matrix (including the diagonal).
    #[inline]
    pub fn lower_triangle(&self) -> MatrixMN<N, R, C>
        where DefaultAllocator: Allocator<N, R, C> {
        let mut res = self.clone_owned();
        res.fill_upper_triangle(N::zero(), 1);

        res
    }
}

impl<N: Scalar, R: Dim, C: Dim, S: StorageMut<N, R, C>> Matrix<N, R, C, S> {
    /// Sets all the elements of this matrix to `val`.
    #[inline]
    pub fn fill(&mut self, val: N) {
        for e in self.iter_mut() {
            *e = val
        }
    }

    /// Fills `self` with the identity matrix.
    #[inline]
    pub fn fill_with_identity(&mut self)
        where N: Zero + One {
        self.fill(N::zero());
        self.fill_diagonal(N::one());
    }

    /// Sets all the diagonal elements of this matrix to `val`.
    #[inline]
    pub fn fill_diagonal(&mut self, val: N) {
        let (nrows, ncols) = self.shape();
        let n = cmp::min(nrows, ncols);

        for i in 0 .. n {
            unsafe { *self.get_unchecked_mut(i, i) = val }
        }
    }

    /// Sets all the elements of the selected row to `val`.
    #[inline]
    pub fn fill_row(&mut self, i: usize, val: N) {
        assert!(i < self.nrows(), "Row index out of bounds.");
        for j in 0 .. self.ncols() {
            unsafe { *self.get_unchecked_mut(i, j) = val }
        }
    }

    /// Sets all the elements of the selected column to `val`.
    #[inline]
    pub fn fill_column(&mut self, j: usize, val: N) {
        assert!(j < self.ncols(), "Row index out of bounds.");
        for i in 0 .. self.nrows() {
            unsafe { *self.get_unchecked_mut(i, j) = val }
        }
    }

    /// Fills the diagonal of this matrix with the content of the given vector.
    #[inline]
    pub fn set_diagonal<R2: Dim, S2>(&mut self, diag: &Vector<N, R2, S2>)
        where R:  DimMin<C>,
              S2: Storage<N, R2>,
              ShapeConstraint: DimEq<DimMinimum<R, C>, R2> {
        let (nrows, ncols)  = self.shape();
        let min_nrows_ncols = cmp::min(nrows, ncols);
        assert_eq!(diag.len(), min_nrows_ncols, "Mismatched dimensions.");

        for i in 0 .. min_nrows_ncols {
            unsafe { *self.get_unchecked_mut(i, i) = *diag.vget_unchecked(i) }
        }
    }

    /// Sets all the elements of the lower-triangular part of this matrix to `val`.
    ///
    /// The parameter `shift` allows some subdiagonals to be left untouched:
    /// * If `shift = 0` then the diagonal is overwritten as well.
    /// * If `shift = 1` then the diagonal is left untouched.
    /// * If `shift > 1`, then the diagonal and the first `shift - 1` subdiagonals are left
    /// untouched.
    #[inline]
    pub fn fill_lower_triangle(&mut self, val: N, shift: usize) {
        for j in 0 .. self.ncols() {
            for i in (j + shift) .. self.nrows() {
                unsafe { *self.get_unchecked_mut(i, j) = val }
            }
        }
    }

    /// Sets all the elements of the lower-triangular part of this matrix to `val`.
    ///
    /// The parameter `shift` allows some superdiagonals to be left untouched:
    /// * If `shift = 0` then the diagonal is overwritten as well.
    /// * If `shift = 1` then the diagonal is left untouched.
    /// * If `shift > 1`, then the diagonal and the first `shift - 1` superdiagonals are left
    /// untouched.
    #[inline]
    pub fn fill_upper_triangle(&mut self, val: N, shift: usize) {
        for j in shift .. self.ncols() {
            // FIXME: is there a more efficient way to avoid the min ?
            // (necessary for rectangular matrices)
            for i in 0 .. cmp::min(j + 1 - shift, self.nrows()) {
                unsafe { *self.get_unchecked_mut(i, j) = val }
            }
        }
    }

    /// Swaps two rows in-place.
    #[inline]
    pub fn swap_rows(&mut self, irow1: usize, irow2: usize) {
        assert!(irow1 < self.nrows() && irow2 < self.nrows());

        if irow1 != irow2 {
            // FIXME: optimize that.
            for i in 0 .. self.ncols() {
                unsafe { self.swap_unchecked((irow1, i), (irow2, i)) }
            }
        }
        // Otherwise do nothing.
    }

    /// Swaps two columns in-place.
    #[inline]
    pub fn swap_columns(&mut self, icol1: usize, icol2: usize) {
        assert!(icol1 < self.ncols() && icol2 < self.ncols());

        if icol1 != icol2 {
            // FIXME: optimize that.
            for i in 0 .. self.nrows() {
                unsafe { self.swap_unchecked((i, icol1), (i, icol2)) }
            }
        }
        // Otherwise do nothing.
    }
}

impl<N: Scalar, D: Dim, S: StorageMut<N, D, D>> Matrix<N, D, D, S> {
    /// Copies the upper-triangle of this matrix to its lower-triangular part.
    ///
    /// This makes the matrix symmetric. Panics if the matrix is not square.
    pub fn fill_lower_triangle_with_upper_triangle(&mut self) {
        assert!(self.is_square(), "The input matrix should be square.");

        let dim = self.nrows();
        for j in 0 .. dim {
            for i in j + 1 .. dim {
                unsafe {
                    *self.get_unchecked_mut(i, j) = *self.get_unchecked(j, i);
                }
            }
        }
    }

    /// Copies the upper-triangle of this matrix to its upper-triangular part.
    ///
    /// This makes the matrix symmetric. Panics if the matrix is not square.
    pub fn fill_upper_triangle_with_lower_triangle(&mut self) {
        assert!(self.is_square(), "The input matrix should be square.");

        for j in 1 .. self.ncols() {
            for i in 0 .. j {
                unsafe {
                    *self.get_unchecked_mut(i, j) = *self.get_unchecked(j, i);
                }
            }
        }
    }
}

/*
 *
 * FIXME: specialize all the following for slices.
 *
 */
impl<N: Scalar, R: Dim, C: Dim, S: Storage<N, R, C>> Matrix<N, R, C, S> {
    /*
     *
     * Column removal.
     *
     */
    /// Removes the `i`-th column from this matrix.
    #[inline]
    pub fn remove_column(self, i: usize) -> MatrixMN<N, R, DimDiff<C, U1>>
        where C: DimSub<U1>,
              DefaultAllocator: Reallocator<N, R, C, R, DimDiff<C, U1>> {
        self.remove_fixed_columns::<U1>(i)
    }

    /// Removes a fixed number − `D::dim()` − of consecutive columns from this matrix, starting
    /// with the `i`-th (included).
    #[inline]
    pub fn remove_fixed_columns<D>(self, i: usize) -> MatrixMN<N, R, DimDiff<C, D>>
        where D: DimName,
              C: DimSub<D>,
              DefaultAllocator: Reallocator<N, R, C, R, DimDiff<C, D>> {

        self.remove_columns_generic(i, D::name())
    }

    /// Removes `n` consecutive columns from this matrix, starting with the `i`-th (included).
    #[inline]
    pub fn remove_columns(self, i: usize, n: usize) -> MatrixMN<N, R, Dynamic>
        where C: DimSub<Dynamic, Output = Dynamic>,
              DefaultAllocator: Reallocator<N, R, C, R, Dynamic> {

        self.remove_columns_generic(i, Dynamic::new(n))
    }

    /// Removes `nremove.value()` columns from this matrix, starting with the `i`-th (included).
    ///
    /// This is the generic implementation of `.remove_columns(...)` and
    /// `.remove_fixed_columns(...)` which have nicer API interfaces.
    #[inline]
    pub fn remove_columns_generic<D>(self, i: usize, nremove: D) -> MatrixMN<N, R, DimDiff<C, D>>
        where D: Dim,
              C: DimSub<D>,
              DefaultAllocator: Reallocator<N, R, C, R, DimDiff<C, D>> {

        let mut m = self.into_owned();
        let (nrows, ncols) = m.data.shape();
        assert!(i + nremove.value() <= ncols.value(), "Column index out of range.");

        if nremove.value() != 0 && i + nremove.value() < ncols.value() {
            // The first `deleted_i * nrows` are left untouched.
            let copied_value_start = i + nremove.value();

            unsafe {
                let ptr_in  = m.data.ptr().offset((copied_value_start * nrows.value()) as isize);
                let ptr_out = m.data.ptr_mut().offset((i * nrows.value()) as isize);

                ptr::copy(ptr_in, ptr_out, (ncols.value() - copied_value_start) * nrows.value());
            }
        }

        unsafe {
            Matrix::from_data(DefaultAllocator::reallocate_copy(nrows, ncols.sub(nremove), m.data))
        }
    }


    /*
     *
     * Row removal.
     *
     */
    /// Removes the `i`-th row from this matrix.
    #[inline]
    pub fn remove_row(self, i: usize) -> MatrixMN<N, DimDiff<R, U1>, C>
        where R: DimSub<U1>,
              DefaultAllocator: Reallocator<N, R, C, DimDiff<R, U1>, C> {
        self.remove_fixed_rows::<U1>(i)
    }

    /// Removes a fixed number − `D::dim()` − of consecutive rows from this matrix, starting
    /// with the `i`-th (included).
    #[inline]
    pub fn remove_fixed_rows<D>(self, i: usize) -> MatrixMN<N, DimDiff<R, D>, C>
        where D: DimName,
              R: DimSub<D>,
              DefaultAllocator: Reallocator<N, R, C, DimDiff<R, D>, C> {

        self.remove_rows_generic(i, D::name())
    }

    /// Removes `n` consecutive rows from this matrix, starting with the `i`-th (included).
    #[inline]
    pub fn remove_rows(self, i: usize, n: usize) -> MatrixMN<N, Dynamic, C>
        where R: DimSub<Dynamic, Output = Dynamic>,
              DefaultAllocator: Reallocator<N, R, C, Dynamic, C> {

        self.remove_rows_generic(i, Dynamic::new(n))
    }

    /// Removes `nremove.value()` rows from this matrix, starting with the `i`-th (included).
    ///
    /// This is the generic implementation of `.remove_rows(...)` and `.remove_fixed_rows(...)`
    /// which have nicer API interfaces.
    #[inline]
    pub fn remove_rows_generic<D>(self, i: usize, nremove: D) -> MatrixMN<N, DimDiff<R, D>, C>
        where D: Dim,
              R: DimSub<D>,
              DefaultAllocator: Reallocator<N, R, C, DimDiff<R, D>, C> {
        let mut m = self.into_owned();
        let (nrows, ncols) = m.data.shape();
        assert!(i + nremove.value() <= nrows.value(), "Row index out of range.");

        if nremove.value() != 0 {
            unsafe {
                compress_rows(&mut m.data.as_mut_slice(), nrows.value(), ncols.value(), i, nremove.value());
            }
        }

        unsafe {
            Matrix::from_data(DefaultAllocator::reallocate_copy(nrows.sub(nremove), ncols, m.data))
        }
    }

    /*
     *
     * Columns insertion.
     *
     */
    /// Inserts a column filled with `val` at the `i-th` position.
    #[inline]
    pub fn insert_column(self, i: usize, val: N) -> MatrixMN<N, R, DimSum<C, U1>>
        where C: DimAdd<U1>,
              DefaultAllocator: Reallocator<N, R, C, R, DimSum<C, U1>> {
        self.insert_fixed_columns::<U1>(i, val)
    }

    /// Inserts `D` column filled with `val` at the `i-th` position.
    #[inline]
    pub fn insert_fixed_columns<D>(self, i: usize, val: N) -> MatrixMN<N, R, DimSum<C, D>>
        where D: DimName,
              C: DimAdd<D>,
              DefaultAllocator: Reallocator<N, R, C, R, DimSum<C, D>> {
        let mut res = unsafe { self.insert_columns_generic_uninitialized(i, D::name()) };
        res.fixed_columns_mut::<D>(i).fill(val);
        res
    }

    /// Inserts `n` column filled with `val` at the `i-th` position.
    #[inline]
    pub fn insert_columns(self, i: usize, n: usize, val: N) -> MatrixMN<N, R, Dynamic>
        where C: DimAdd<Dynamic, Output = Dynamic>,
              DefaultAllocator: Reallocator<N, R, C, R, Dynamic> {
        let mut res = unsafe { self.insert_columns_generic_uninitialized(i, Dynamic::new(n)) };
        res.columns_mut(i, n).fill(val);
        res
    }

    /// Inserts `ninsert.value()` columns at the `i-th` place of this matrix.
    ///
    /// The added column values are not initialized.
    #[inline]
    pub unsafe fn insert_columns_generic_uninitialized<D>(self, i: usize, ninsert: D)
        -> MatrixMN<N, R, DimSum<C, D>>
        where D: Dim,
              C: DimAdd<D>,
              DefaultAllocator: Reallocator<N, R, C, R, DimSum<C, D>> {

        let m = self.into_owned();
        let (nrows, ncols) = m.data.shape();
        let mut res = Matrix::from_data(DefaultAllocator::reallocate_copy(nrows, ncols.add(ninsert), m.data));

        assert!(i <= ncols.value(), "Column insertion index out of range.");

        if ninsert.value() != 0 && i != ncols.value() {
            let ptr_in  = res.data.ptr().offset((i * nrows.value()) as isize);
            let ptr_out = res.data.ptr_mut().offset(((i + ninsert.value()) * nrows.value()) as isize);

            ptr::copy(ptr_in, ptr_out, (ncols.value() - i) * nrows.value())
        }

        res
    }

    /*
     *
     * Rows insertion.
     *
     */
    /// Inserts a row filled with `val` at the `i-th` position.
    #[inline]
    pub fn insert_row(self, i: usize, val: N) -> MatrixMN<N, DimSum<R, U1>, C>
        where R: DimAdd<U1>,
              DefaultAllocator: Reallocator<N, R, C, DimSum<R, U1>, C> {
        self.insert_fixed_rows::<U1>(i, val)
    }

    /// Inserts `D` row filled with `val` at the `i-th` position.
    #[inline]
    pub fn insert_fixed_rows<D>(self, i: usize, val: N) -> MatrixMN<N, DimSum<R, D>, C>
        where D: DimName,
              R: DimAdd<D>,
              DefaultAllocator: Reallocator<N, R, C, DimSum<R, D>, C> {
        let mut res = unsafe { self.insert_rows_generic_uninitialized(i, D::name()) };
        res.fixed_rows_mut::<D>(i).fill(val);
        res
    }

    /// Inserts `n` rows filled with `val` at the `i-th` position.
    #[inline]
    pub fn insert_rows(self, i: usize, n: usize, val: N) -> MatrixMN<N, Dynamic, C>
        where R: DimAdd<Dynamic, Output = Dynamic>,
              DefaultAllocator: Reallocator<N, R, C, Dynamic, C> {
        let mut res = unsafe { self.insert_rows_generic_uninitialized(i, Dynamic::new(n)) };
        res.rows_mut(i, n).fill(val);
        res
    }

    /// Inserts `ninsert.value()` rows at the `i-th` place of this matrix.
    ///
    /// The added rows values are not initialized.
    #[inline]
    pub unsafe fn insert_rows_generic_uninitialized<D>(self, i: usize, ninsert: D)
        -> MatrixMN<N, DimSum<R, D>, C>
        where D: Dim,
              R: DimAdd<D>,
              DefaultAllocator: Reallocator<N, R, C, DimSum<R, D>, C> {

        let m = self.into_owned();
        let (nrows, ncols) = m.data.shape();
        let mut res = Matrix::from_data(DefaultAllocator::reallocate_copy(nrows.add(ninsert), ncols, m.data));

        assert!(i <= nrows.value(), "Row insertion index out of range.");

        if ninsert.value() != 0 {
            extend_rows(&mut res.data.as_mut_slice(), nrows.value(), ncols.value(), i, ninsert.value());
        }

        res
    }

    /*
     *
     * Resizing.
     *
     */

    pub fn resize(self, new_nrows: usize, new_ncols: usize, val: N) -> DMatrix<N>
        where DefaultAllocator: Reallocator<N, R, C, Dynamic, Dynamic> {

        self.resize_generic(Dynamic::new(new_nrows), Dynamic::new(new_ncols), val)
    }

    pub fn fixed_resize<R2: DimName, C2: DimName>(self, val: N) -> MatrixMN<N, R2, C2>
        where DefaultAllocator: Reallocator<N, R, C, R2, C2> {

        self.resize_generic(R2::name(), C2::name(), val)
    }

    /// Resizes `self` such that it has dimensions `new_nrows × now_ncols`. The values are copied
    /// such that `self[(i, j)] == result[(i, j)]`. If the result has more rows and/or columns than
    /// `self`, then the extra rows or columns are filled with `val`.
    #[inline]
    pub fn resize_generic<R2: Dim, C2: Dim>(self, new_nrows: R2, new_ncols: C2, val: N) -> MatrixMN<N, R2, C2>
        where DefaultAllocator: Reallocator<N, R, C, R2, C2> {

        let (nrows, ncols) = self.shape();
        let mut data = self.data.into_owned();

        if new_nrows.value() == nrows {
            let res = unsafe { DefaultAllocator::reallocate_copy(new_nrows, new_ncols, data) };

            Matrix::from_data(res)
        }
        else {
            let mut res;

            unsafe {
                if new_nrows.value() < nrows {
                    compress_rows(&mut data.as_mut_slice(), nrows, ncols, new_nrows.value(), nrows - new_nrows.value());
                    res = Matrix::from_data(DefaultAllocator::reallocate_copy(new_nrows, new_ncols, data));
                }
                else {
                    res = Matrix::from_data(DefaultAllocator::reallocate_copy(new_nrows, new_ncols, data));
                    extend_rows(&mut res.data.as_mut_slice(), nrows, ncols, nrows, new_nrows.value() - nrows);
                }
            }

            if new_ncols.value() > ncols {
                res.columns_range_mut(ncols ..).fill(val);
            }

            if new_nrows.value() > nrows {
                res.slice_range_mut(nrows .., .. cmp::min(ncols, new_ncols.value())).fill(val);
            }

            res
        }
    }
}


unsafe fn compress_rows<N: Scalar>(data: &mut [N], nrows: usize, ncols: usize, i: usize, nremove: usize) {
    let new_nrows = nrows - nremove;
    let ptr_in    = data.as_ptr();
    let ptr_out   = data.as_mut_ptr();

    let mut curr_i = i;

    for k in 0 .. ncols - 1 {
        ptr::copy(ptr_in.offset((curr_i + (k + 1) * nremove) as isize),
                  ptr_out.offset(curr_i as isize),
                  new_nrows);

        curr_i += new_nrows;
    }

    // Deal with the last column from which less values have to be copied.
    let remaining_len = nrows - i - nremove;
    ptr::copy(ptr_in.offset((nrows * ncols - remaining_len) as isize),
              ptr_out.offset(curr_i as isize),
              remaining_len);
}


unsafe fn extend_rows<N: Scalar>(data: &mut [N], nrows: usize, ncols: usize, i: usize, ninsert: usize) {
    let new_nrows = nrows + ninsert;
    let ptr_in    = data.as_ptr();
    let ptr_out   = data.as_mut_ptr();

    let remaining_len = nrows - i;
    let mut curr_i = new_nrows * ncols - remaining_len;

    // Deal with the last column from which less values have to be copied.
    ptr::copy(ptr_in.offset((nrows * ncols - remaining_len) as isize),
              ptr_out.offset(curr_i as isize),
              remaining_len);

    for k in (0 .. ncols - 1).rev() {
        curr_i -= new_nrows;

        ptr::copy(ptr_in.offset((k * nrows + i) as isize),
                  ptr_out.offset(curr_i as isize),
                  nrows);
    }
}