from __future__ import print_function, division

from sympy import ask, Q
from sympy.core import Tuple, Basic, Add
from sympy.strategies import typed, exhaust, condition, debug, do_one, unpack, chain
from sympy.strategies.traverse import bottom_up
from sympy.utilities import sift

from sympy.matrices.expressions.matexpr import MatrixExpr, ZeroMatrix, Identity
from sympy.matrices.expressions.matmul import MatMul
from sympy.matrices.expressions.matadd import MatAdd
from sympy.matrices.expressions.matpow import MatPow
from sympy.matrices.expressions.transpose import Transpose, transpose
from sympy.matrices.expressions.trace import Trace
from sympy.matrices.expressions.determinant import det, Determinant
from sympy.matrices.expressions.slice import MatrixSlice
from sympy.matrices.expressions.inverse import Inverse
from sympy.matrices import Matrix, eye, ShapeError


class BlockMatrix(MatrixExpr):
    """A BlockMatrix is a Matrix composed of other smaller, submatrices

    The submatrices are stored in a SymPy Matrix object but accessed as part of
    a Matrix Expression

    >>> from sympy import (MatrixSymbol, BlockMatrix, symbols,
    ...     Identity, ZeroMatrix, block_collapse)
    >>> n,m,l = symbols('n m l')
    >>> X = MatrixSymbol('X', n, n)
    >>> Y = MatrixSymbol('Y', m ,m)
    >>> Z = MatrixSymbol('Z', n, m)
    >>> B = BlockMatrix([[X, Z], [ZeroMatrix(m,n), Y]])
    >>> print(B)
    Matrix([
    [X, Z],
    [0, Y]])

    >>> C = BlockMatrix([[Identity(n), Z]])
    >>> print(C)
    Matrix([[I, Z]])

    >>> print(block_collapse(C*B))
    Matrix([[X, Z*Y + Z]])

    """
    def __new__(cls, *args):
        from sympy.matrices.immutable import ImmutableMatrix
        mat = ImmutableMatrix(*args)

        obj = Basic.__new__(cls, mat)
        return obj

    @property
    def shape(self):
        numrows = numcols = 0
        M = self.blocks
        for i in range(M.shape[0]):
            numrows += M[i, 0].shape[0]
        for i in range(M.shape[1]):
            numcols += M[0, i].shape[1]
        return (numrows, numcols)

    @property
    def blockshape(self):
        return self.blocks.shape

    @property
    def blocks(self):
        return self.args[0]

    @property
    def rowblocksizes(self):
        return [self.blocks[i, 0].rows for i in range(self.blockshape[0])]

    @property
    def colblocksizes(self):
        return [self.blocks[0, i].cols for i in range(self.blockshape[1])]

    def structurally_equal(self, other):
        return (isinstance(other, BlockMatrix)
            and self.shape == other.shape
            and self.blockshape == other.blockshape
            and self.rowblocksizes == other.rowblocksizes
            and self.colblocksizes == other.colblocksizes)

    def _blockmul(self, other):
        if (isinstance(other, BlockMatrix) and
                self.colblocksizes == other.rowblocksizes):
            return BlockMatrix(self.blocks*other.blocks)

        return self * other

    def _blockadd(self, other):
        if (isinstance(other, BlockMatrix)
                and self.structurally_equal(other)):
            return BlockMatrix(self.blocks + other.blocks)

        return self + other

    def _eval_transpose(self):
        # Flip all the individual matrices
        matrices = [transpose(matrix) for matrix in self.blocks]
        # Make a copy
        M = Matrix(self.blockshape[0], self.blockshape[1], matrices)
        # Transpose the block structure
        M = M.transpose()
        return BlockMatrix(M)

    def _eval_trace(self):
        if self.rowblocksizes == self.colblocksizes:
            return Add(*[Trace(self.blocks[i, i])
                        for i in range(self.blockshape[0])])
        raise NotImplementedError(
            "Can't perform trace of irregular blockshape")

    def _eval_determinant(self):
        if self.blockshape == (2, 2):
            [[A, B],
             [C, D]] = self.blocks.tolist()
            if ask(Q.invertible(A)):
                return det(A)*det(D - C*A.I*B)
            elif ask(Q.invertible(D)):
                return det(D)*det(A - B*D.I*C)
        return Determinant(self)

    def transpose(self):
        """Return transpose of matrix.

        Examples
        ========

        >>> from sympy import MatrixSymbol, BlockMatrix, ZeroMatrix
        >>> from sympy.abc import l, m, n
        >>> X = MatrixSymbol('X', n, n)
        >>> Y = MatrixSymbol('Y', m ,m)
        >>> Z = MatrixSymbol('Z', n, m)
        >>> B = BlockMatrix([[X, Z], [ZeroMatrix(m,n), Y]])
        >>> B.transpose()
        Matrix([
        [X',  0],
        [Z', Y']])
        >>> _.transpose()
        Matrix([
        [X, Z],
        [0, Y]])
        """
        return self._eval_transpose()

    def _entry(self, i, j):
        # Find row entry
        for row_block, numrows in enumerate(self.rowblocksizes):
            if (i < numrows) is not False:
                break
            else:
                i -= numrows
        for col_block, numcols in enumerate(self.colblocksizes):
            if (j < numcols) is not False:
                break
            else:
                j -= numcols
        return self.blocks[row_block, col_block][i, j]

    @property
    def is_Identity(self):
        if self.blockshape[0] != self.blockshape[1]:
            return False
        for i in range(self.blockshape[0]):
            for j in range(self.blockshape[1]):
                if i==j and not self.blocks[i, j].is_Identity:
                    return False
                if i!=j and not self.blocks[i, j].is_ZeroMatrix:
                    return False
        return True

    @property
    def is_structurally_symmetric(self):
        return self.rowblocksizes == self.colblocksizes

    def equals(self, other):
        if self == other:
            return True
        if (isinstance(other, BlockMatrix) and self.blocks == other.blocks):
            return True
        return super(BlockMatrix, self).equals(other)

class BlockDiagMatrix(BlockMatrix):
    """
    A BlockDiagMatrix is a BlockMatrix with matrices only along the diagonal

    >>> from sympy import MatrixSymbol, BlockDiagMatrix, symbols, Identity
    >>> n,m,l = symbols('n m l')
    >>> X = MatrixSymbol('X', n, n)
    >>> Y = MatrixSymbol('Y', m ,m)
    >>> BlockDiagMatrix(X, Y)
    Matrix([
    [X, 0],
    [0, Y]])

    """
    def __new__(cls, *mats):
        return Basic.__new__(BlockDiagMatrix, *mats)

    @property
    def diag(self):
        return self.args

    @property
    def blocks(self):
        from sympy.matrices.immutable import ImmutableMatrix
        mats = self.args
        data = [[mats[i] if i == j else ZeroMatrix(mats[i].rows, mats[j].cols)
                        for j in range(len(mats))]
                        for i in range(len(mats))]
        return ImmutableMatrix(data)

    @property
    def shape(self):
        return (sum(block.rows for block in self.args),
                sum(block.cols for block in self.args))

    @property
    def blockshape(self):
        n = len(self.args)
        return (n, n)

    @property
    def rowblocksizes(self):
        return [block.rows for block in self.args]

    @property
    def colblocksizes(self):
        return [block.cols for block in self.args]

    def _eval_inverse(self, expand='ignored'):
        return BlockDiagMatrix(*[mat.inverse() for mat in self.args])

    def _blockmul(self, other):
        if (isinstance(other, BlockDiagMatrix) and
                self.colblocksizes == other.rowblocksizes):
            return BlockDiagMatrix(*[a*b for a, b in zip(self.args, other.args)])
        else:
            return BlockMatrix._blockmul(self, other)

    def _blockadd(self, other):
        if (isinstance(other, BlockDiagMatrix) and
                self.blockshape == other.blockshape and
                self.rowblocksizes == other.rowblocksizes and
                self.colblocksizes == other.colblocksizes):
            return BlockDiagMatrix(*[a + b for a, b in zip(self.args, other.args)])
        else:
            return BlockMatrix._blockadd(self, other)


def block_collapse(expr):
    """Evaluates a block matrix expression

    >>> from sympy import MatrixSymbol, BlockMatrix, symbols, \
                          Identity, Matrix, ZeroMatrix, block_collapse
    >>> n,m,l = symbols('n m l')
    >>> X = MatrixSymbol('X', n, n)
    >>> Y = MatrixSymbol('Y', m ,m)
    >>> Z = MatrixSymbol('Z', n, m)
    >>> B = BlockMatrix([[X, Z], [ZeroMatrix(m, n), Y]])
    >>> print(B)
    Matrix([
    [X, Z],
    [0, Y]])

    >>> C = BlockMatrix([[Identity(n), Z]])
    >>> print(C)
    Matrix([[I, Z]])

    >>> print(block_collapse(C*B))
    Matrix([[X, Z*Y + Z]])
    """
    hasbm = lambda expr: isinstance(expr, MatrixExpr) and expr.has(BlockMatrix)
    rule = exhaust(
        bottom_up(exhaust(condition(hasbm, typed(
            {MatAdd: do_one(bc_matadd, bc_block_plus_ident),
             MatMul: do_one(bc_matmul, bc_dist),
             Transpose: bc_transpose,
             Inverse: bc_inverse,
             BlockMatrix: do_one(bc_unpack, deblock)})))))
    result = rule(expr)
    try:
        return result.doit()
    except AttributeError:
        return result

def bc_unpack(expr):
    if expr.blockshape == (1, 1):
        return expr.blocks[0, 0]
    return expr

def bc_matadd(expr):
    args = sift(expr.args, lambda M: isinstance(M, BlockMatrix))
    blocks = args[True]
    if not blocks:
        return expr

    nonblocks = args[False]
    block = blocks[0]
    for b in blocks[1:]:
        block = block._blockadd(b)
    if nonblocks:
        return MatAdd(*nonblocks) + block
    else:
        return block

def bc_block_plus_ident(expr):
    idents = [arg for arg in expr.args if arg.is_Identity]
    if not idents:
        return expr

    blocks = [arg for arg in expr.args if isinstance(arg, BlockMatrix)]
    if (blocks and all(b.structurally_equal(blocks[0]) for b in blocks)
               and blocks[0].is_structurally_symmetric):
        block_id = BlockDiagMatrix(*[Identity(k)
                                        for k in blocks[0].rowblocksizes])
        return MatAdd(block_id * len(idents), *blocks).doit()

    return expr

def bc_dist(expr):
    """ Turn  a*[X, Y] into [a*X, a*Y] """
    factor, mat = expr.as_coeff_mmul()
    if factor != 1 and isinstance(unpack(mat), BlockMatrix):
        B = unpack(mat).blocks
        return BlockMatrix([[factor * B[i, j] for j in range(B.cols)]
                                              for i in range(B.rows)])
    return expr


def bc_matmul(expr):
    factor, matrices = expr.as_coeff_matrices()

    i = 0
    while (i+1 < len(matrices)):
        A, B = matrices[i:i+2]
        if isinstance(A, BlockMatrix) and isinstance(B, BlockMatrix):
            matrices[i] = A._blockmul(B)
            matrices.pop(i+1)
        elif isinstance(A, BlockMatrix):
            matrices[i] = A._blockmul(BlockMatrix([[B]]))
            matrices.pop(i+1)
        elif isinstance(B, BlockMatrix):
            matrices[i] = BlockMatrix([[A]])._blockmul(B)
            matrices.pop(i+1)
        else:
            i+=1
    return MatMul(factor, *matrices).doit()

def bc_transpose(expr):
    return BlockMatrix(block_collapse(expr.arg).blocks.applyfunc(transpose).T)


def bc_inverse(expr):
    expr2 = blockinverse_1x1(expr)
    if expr != expr2:
        return expr2
    return blockinverse_2x2(Inverse(reblock_2x2(expr.arg)))

def blockinverse_1x1(expr):
    if isinstance(expr.arg, BlockMatrix) and expr.arg.blockshape == (1, 1):
        mat = Matrix([[expr.arg.blocks[0].inverse()]])
        return BlockMatrix(mat)
    return expr

def blockinverse_2x2(expr):
    if isinstance(expr.arg, BlockMatrix) and expr.arg.blockshape == (2, 2):
        # Cite: The Matrix Cookbook Section 9.1.3
        [[A, B],
         [C, D]] = expr.arg.blocks.tolist()

        return BlockMatrix([[ (A - B*D.I*C).I,  (-A).I*B*(D - C*A.I*B).I],
                            [-(D - C*A.I*B).I*C*A.I,     (D - C*A.I*B).I]])
    else:
        return expr

def deblock(B):
    """ Flatten a BlockMatrix of BlockMatrices """
    if not isinstance(B, BlockMatrix) or not B.blocks.has(BlockMatrix):
        return B
    wrap = lambda x: x if isinstance(x, BlockMatrix) else BlockMatrix([[x]])
    bb = B.blocks.applyfunc(wrap)  # everything is a block

    from sympy import Matrix
    try:
        MM = Matrix(0, sum(bb[0, i].blocks.shape[1] for i in range(bb.shape[1])), [])
        for row in range(0, bb.shape[0]):
            M = Matrix(bb[row, 0].blocks)
            for col in range(1, bb.shape[1]):
                M = M.row_join(bb[row, col].blocks)
            MM = MM.col_join(M)

        return BlockMatrix(MM)
    except ShapeError:
        return B



def reblock_2x2(B):
    """ Reblock a BlockMatrix so that it has 2x2 blocks of block matrices """
    if not isinstance(B, BlockMatrix) or not all(d > 2 for d in B.blocks.shape):
        return B

    BM = BlockMatrix  # for brevity's sake
    return BM([[   B.blocks[0,  0],  BM(B.blocks[0,  1:])],
               [BM(B.blocks[1:, 0]), BM(B.blocks[1:, 1:])]])


def bounds(sizes):
    """ Convert sequence of numbers into pairs of low-high pairs

    >>> from sympy.matrices.expressions.blockmatrix import bounds
    >>> bounds((1, 10, 50))
    [(0, 1), (1, 11), (11, 61)]
    """
    low = 0
    rv = []
    for size in sizes:
        rv.append((low, low + size))
        low += size
    return rv

def blockcut(expr, rowsizes, colsizes):
    """ Cut a matrix expression into Blocks

    >>> from sympy import ImmutableMatrix, blockcut
    >>> M = ImmutableMatrix(4, 4, range(16))
    >>> B = blockcut(M, (1, 3), (1, 3))
    >>> type(B).__name__
    'BlockMatrix'
    >>> ImmutableMatrix(B.blocks[0, 1])
    Matrix([[1, 2, 3]])
    """

    rowbounds = bounds(rowsizes)
    colbounds = bounds(colsizes)
    return BlockMatrix([[MatrixSlice(expr, rowbound, colbound)
                         for colbound in colbounds]
                         for rowbound in rowbounds])
