from sympy.core.assumptions import StdFactKB
from sympy.core import S, Pow, sympify
from sympy.core.expr import AtomicExpr, Expr
from sympy.core.compatibility import range, default_sort_key
from sympy import sqrt, ImmutableMatrix as Matrix, Add
from sympy.vector.coordsysrect import CoordSys3D
from sympy.vector.basisdependent import (BasisDependent, BasisDependentAdd,
                                         BasisDependentMul, BasisDependentZero)
from sympy.vector.dyadic import BaseDyadic, Dyadic, DyadicAdd


class Vector(BasisDependent):
    """
    Super class for all Vector classes.
    Ideally, neither this class nor any of its subclasses should be
    instantiated by the user.
    """

    is_Vector = True
    _op_priority = 12.0

    @property
    def components(self):
        """
        Returns the components of this vector in the form of a
        Python dictionary mapping BaseVector instances to the
        corresponding measure numbers.

        Examples
        ========

        >>> from sympy.vector import CoordSys3D
        >>> C = CoordSys3D('C')
        >>> v = 3*C.i + 4*C.j + 5*C.k
        >>> v.components
        {C.i: 3, C.j: 4, C.k: 5}

        """
        # The '_components' attribute is defined according to the
        # subclass of Vector the instance belongs to.
        return self._components

    def magnitude(self):
        """
        Returns the magnitude of this vector.
        """
        return sqrt(self & self)

    def normalize(self):
        """
        Returns the normalized version of this vector.
        """
        return self / self.magnitude()

    def dot(self, other):
        """
        Returns the dot product of this Vector, either with another
        Vector, or a Dyadic, or a Del operator.
        If 'other' is a Vector, returns the dot product scalar (Sympy
        expression).
        If 'other' is a Dyadic, the dot product is returned as a Vector.
        If 'other' is an instance of Del, returns the directional
        derivative operator as a Python function. If this function is
        applied to a scalar expression, it returns the directional
        derivative of the scalar field wrt this Vector.

        Parameters
        ==========

        other: Vector/Dyadic/Del
            The Vector or Dyadic we are dotting with, or a Del operator .

        Examples
        ========

        >>> from sympy.vector import CoordSys3D, Del
        >>> C = CoordSys3D('C')
        >>> delop = Del()
        >>> C.i.dot(C.j)
        0
        >>> C.i & C.i
        1
        >>> v = 3*C.i + 4*C.j + 5*C.k
        >>> v.dot(C.k)
        5
        >>> (C.i & delop)(C.x*C.y*C.z)
        C.y*C.z
        >>> d = C.i.outer(C.i)
        >>> C.i.dot(d)
        C.i

        """

        # Check special cases
        if isinstance(other, Dyadic):
            if isinstance(self, VectorZero):
                return Vector.zero
            outvec = Vector.zero
            for k, v in other.components.items():
                vect_dot = k.args[0].dot(self)
                outvec += vect_dot * v * k.args[1]
            return outvec
        from sympy.vector.deloperator import Del
        if not isinstance(other, Vector) and not isinstance(other, Del):
            raise TypeError(str(other) + " is not a vector, dyadic or " +
                            "del operator")

        # Check if the other is a del operator
        if isinstance(other, Del):
            def directional_derivative(field):
                from sympy.vector.functions import directional_derivative
                return directional_derivative(field, self)
            return directional_derivative

        return dot(self, other)

    def __and__(self, other):
        return self.dot(other)

    __and__.__doc__ = dot.__doc__

    def cross(self, other):
        """
        Returns the cross product of this Vector with another Vector or
        Dyadic instance.
        The cross product is a Vector, if 'other' is a Vector. If 'other'
        is a Dyadic, this returns a Dyadic instance.

        Parameters
        ==========

        other: Vector/Dyadic
            The Vector or Dyadic we are crossing with.

        Examples
        ========

        >>> from sympy.vector import CoordSys3D
        >>> C = CoordSys3D('C')
        >>> C.i.cross(C.j)
        C.k
        >>> C.i ^ C.i
        0
        >>> v = 3*C.i + 4*C.j + 5*C.k
        >>> v ^ C.i
        5*C.j + (-4)*C.k
        >>> d = C.i.outer(C.i)
        >>> C.j.cross(d)
        (-1)*(C.k|C.i)

        """

        # Check special cases
        if isinstance(other, Dyadic):
            if isinstance(self, VectorZero):
                return Dyadic.zero
            outdyad = Dyadic.zero
            for k, v in other.components.items():
                cross_product = self.cross(k.args[0])
                outer = cross_product.outer(k.args[1])
                outdyad += v * outer
            return outdyad

        return cross(self, other)

    def __xor__(self, other):
        return self.cross(other)

    __xor__.__doc__ = cross.__doc__

    def outer(self, other):
        """
        Returns the outer product of this vector with another, in the
        form of a Dyadic instance.

        Parameters
        ==========

        other : Vector
            The Vector with respect to which the outer product is to
            be computed.

        Examples
        ========

        >>> from sympy.vector import CoordSys3D
        >>> N = CoordSys3D('N')
        >>> N.i.outer(N.j)
        (N.i|N.j)

        """

        # Handle the special cases
        if not isinstance(other, Vector):
            raise TypeError("Invalid operand for outer product")
        elif (isinstance(self, VectorZero) or
                isinstance(other, VectorZero)):
            return Dyadic.zero

        # Iterate over components of both the vectors to generate
        # the required Dyadic instance
        args = []
        for k1, v1 in self.components.items():
            for k2, v2 in other.components.items():
                args.append((v1 * v2) * BaseDyadic(k1, k2))

        return DyadicAdd(*args)

    def projection(self, other, scalar=False):
        """
        Returns the vector or scalar projection of the 'other' on 'self'.

        Examples
        ========

        >>> from sympy.vector.coordsysrect import CoordSys3D
        >>> from sympy.vector.vector import Vector, BaseVector
        >>> C = CoordSys3D('C')
        >>> i, j, k = C.base_vectors()
        >>> v1 = i + j + k
        >>> v2 = 3*i + 4*j
        >>> v1.projection(v2)
        7/3*C.i + 7/3*C.j + 7/3*C.k
        >>> v1.projection(v2, scalar=True)
        7/3

        """
        if self.equals(Vector.zero):
            return S.zero if scalar else Vector.zero

        if scalar:
            return self.dot(other) / self.dot(self)
        else:
            return self.dot(other) / self.dot(self) * self

    @property
    def _projections(self):
        """
        Returns the components of this vector but the output includes
        also zero values components.

        Examples
        ========

        >>> from sympy.vector import CoordSys3D, Vector
        >>> C = CoordSys3D('C')
        >>> v1 = 3*C.i + 4*C.j + 5*C.k
        >>> v1._projections
        (3, 4, 5)
        >>> v2 = C.x*C.y*C.z*C.i
        >>> v2._projections
        (C.x*C.y*C.z, 0, 0)
        >>> v3 = Vector.zero
        >>> v3._projections
        (0, 0, 0)
        """

        from sympy.vector.operators import _get_coord_sys_from_expr
        if isinstance(self, VectorZero):
            return (S(0), S(0), S(0))
        base_vec = next(iter(_get_coord_sys_from_expr(self))).base_vectors()
        return tuple([self.dot(i) for i in base_vec])

    def __or__(self, other):
        return self.outer(other)

    __or__.__doc__ = outer.__doc__

    def to_matrix(self, system):
        """
        Returns the matrix form of this vector with respect to the
        specified coordinate system.

        Parameters
        ==========

        system : CoordSys3D
            The system wrt which the matrix form is to be computed

        Examples
        ========

        >>> from sympy.vector import CoordSys3D
        >>> C = CoordSys3D('C')
        >>> from sympy.abc import a, b, c
        >>> v = a*C.i + b*C.j + c*C.k
        >>> v.to_matrix(C)
        Matrix([
        [a],
        [b],
        [c]])

        """

        return Matrix([self.dot(unit_vec) for unit_vec in
                       system.base_vectors()])

    def separate(self):
        """
        The constituents of this vector in different coordinate systems,
        as per its definition.

        Returns a dict mapping each CoordSys3D to the corresponding
        constituent Vector.

        Examples
        ========

        >>> from sympy.vector import CoordSys3D
        >>> R1 = CoordSys3D('R1')
        >>> R2 = CoordSys3D('R2')
        >>> v = R1.i + R2.i
        >>> v.separate() == {R1: R1.i, R2: R2.i}
        True

        """

        parts = {}
        for vect, measure in self.components.items():
            parts[vect.system] = (parts.get(vect.system, Vector.zero) +
                                  vect * measure)
        return parts


class BaseVector(Vector, AtomicExpr):
    """
    Class to denote a base vector.

    Unicode pretty forms in Python 2 should use the prefix ``u``.

    """

    def __new__(cls, index, system, pretty_str=None, latex_str=None):
        if pretty_str is None:
            pretty_str = "x{0}".format(index)
        if latex_str is None:
            latex_str = "x_{0}".format(index)
        pretty_str = str(pretty_str)
        latex_str = str(latex_str)
        # Verify arguments
        if index not in range(0, 3):
            raise ValueError("index must be 0, 1 or 2")
        if not isinstance(system, CoordSys3D):
            raise TypeError("system should be a CoordSys3D")
        name = system._vector_names[index]
        # Initialize an object
        obj = super(BaseVector, cls).__new__(cls, S(index), system)
        # Assign important attributes
        obj._base_instance = obj
        obj._components = {obj: S(1)}
        obj._measure_number = S(1)
        obj._name = system._name + '.' + name
        obj._pretty_form = u'' + pretty_str
        obj._latex_form = latex_str
        obj._system = system
        # The _id is used for printing purposes
        obj._id = (index, system)
        assumptions = {'commutative': True}
        obj._assumptions = StdFactKB(assumptions)

        # This attr is used for re-expression to one of the systems
        # involved in the definition of the Vector. Applies to
        # VectorMul and VectorAdd too.
        obj._sys = system

        return obj

    @property
    def system(self):
        return self._system

    def __str__(self, printer=None):
        return self._name

    @property
    def free_symbols(self):
        return {self}

    __repr__ = __str__
    _sympystr = __str__


class VectorAdd(BasisDependentAdd, Vector):
    """
    Class to denote sum of Vector instances.
    """

    def __new__(cls, *args, **options):
        obj = BasisDependentAdd.__new__(cls, *args, **options)
        return obj

    def __str__(self, printer=None):
        ret_str = ''
        items = list(self.separate().items())
        items.sort(key=lambda x: x[0].__str__())
        for system, vect in items:
            base_vects = system.base_vectors()
            for x in base_vects:
                if x in vect.components:
                    temp_vect = self.components[x] * x
                    ret_str += temp_vect.__str__(printer) + " + "
        return ret_str[:-3]

    __repr__ = __str__
    _sympystr = __str__


class VectorMul(BasisDependentMul, Vector):
    """
    Class to denote products of scalars and BaseVectors.
    """

    def __new__(cls, *args, **options):
        obj = BasisDependentMul.__new__(cls, *args, **options)
        return obj

    @property
    def base_vector(self):
        """ The BaseVector involved in the product. """
        return self._base_instance

    @property
    def measure_number(self):
        """ The scalar expression involved in the definition of
        this VectorMul.
        """
        return self._measure_number


class VectorZero(BasisDependentZero, Vector):
    """
    Class to denote a zero vector
    """

    _op_priority = 12.1
    _pretty_form = u'0'
    _latex_form = r'\mathbf{\hat{0}}'

    def __new__(cls):
        obj = BasisDependentZero.__new__(cls)
        return obj


class Cross(Vector):
    """
    Represents unevaluated Cross product.

    Examples
    ========

    >>> from sympy.vector import CoordSys3D, Cross
    >>> R = CoordSys3D('R')
    >>> v1 = R.i + R.j + R.k
    >>> v2 = R.x * R.i + R.y * R.j + R.z * R.k
    >>> Cross(v1, v2)
    Cross(R.i + R.j + R.k, R.x*R.i + R.y*R.j + R.z*R.k)
    >>> Cross(v1, v2).doit()
    (-R.y + R.z)*R.i + (R.x - R.z)*R.j + (-R.x + R.y)*R.k

    """

    def __new__(cls, expr1, expr2):
        expr1 = sympify(expr1)
        expr2 = sympify(expr2)
        if default_sort_key(expr1) > default_sort_key(expr2):
            return -Cross(expr2, expr1)
        obj = Expr.__new__(cls, expr1, expr2)
        obj._expr1 = expr1
        obj._expr2 = expr2
        return obj

    def doit(self, **kwargs):
        return cross(self._expr1, self._expr2)


class Dot(Expr):
    """
    Represents unevaluated Dot product.

    Examples
    ========

    >>> from sympy.vector import CoordSys3D, Dot
    >>> from sympy import symbols
    >>> R = CoordSys3D('R')
    >>> a, b, c = symbols('a b c')
    >>> v1 = R.i + R.j + R.k
    >>> v2 = a * R.i + b * R.j + c * R.k
    >>> Dot(v1, v2)
    Dot(R.i + R.j + R.k, a*R.i + b*R.j + c*R.k)
    >>> Dot(v1, v2).doit()
    a + b + c

    """

    def __new__(cls, expr1, expr2):
        expr1 = sympify(expr1)
        expr2 = sympify(expr2)
        expr1, expr2 = sorted([expr1, expr2], key=default_sort_key)
        obj = Expr.__new__(cls, expr1, expr2)
        obj._expr1 = expr1
        obj._expr2 = expr2
        return obj

    def doit(self, **kwargs):
        return dot(self._expr1, self._expr2)


def cross(vect1, vect2):
    """
    Returns cross product of two vectors.

    Examples
    ========

    >>> from sympy.vector import CoordSys3D
    >>> from sympy.vector.vector import cross
    >>> R = CoordSys3D('R')
    >>> v1 = R.i + R.j + R.k
    >>> v2 = R.x * R.i + R.y * R.j + R.z * R.k
    >>> cross(v1, v2)
    (-R.y + R.z)*R.i + (R.x - R.z)*R.j + (-R.x + R.y)*R.k

    """
    if isinstance(vect1, Add):
        return VectorAdd.fromiter(cross(i, vect2) for i in vect1.args)
    if isinstance(vect2, Add):
        return VectorAdd.fromiter(cross(vect1, i) for i in vect2.args)
    if isinstance(vect1, BaseVector) and isinstance(vect2, BaseVector):
        if vect1._sys == vect2._sys:
            n1 = vect1.args[0]
            n2 = vect2.args[0]
            if n1 == n2:
                return Vector.zero
            n3 = ({0,1,2}.difference({n1, n2})).pop()
            sign = 1 if ((n1 + 1) % 3 == n2) else -1
            return sign*vect1._sys.base_vectors()[n3]
        try:
            from .functions import express
            return cross(express(vect1, vect2._sys), vect2)
        except:
            return Cross(vect1, vect2)
    if isinstance(vect1, VectorZero) or isinstance(vect2, VectorZero):
        return Vector.zero
    if isinstance(vect1, VectorMul):
        v1, m1 = next(iter(vect1.components.items()))
        return m1*cross(v1, vect2)
    if isinstance(vect2, VectorMul):
        v2, m2 = next(iter(vect2.components.items()))
        return m2*cross(vect1, v2)

    return Cross(vect1, vect2)


def dot(vect1, vect2):
    """
    Returns dot product of two vectors.

    Examples
    ========

    >>> from sympy.vector import CoordSys3D
    >>> from sympy.vector.vector import dot
    >>> R = CoordSys3D('R')
    >>> v1 = R.i + R.j + R.k
    >>> v2 = R.x * R.i + R.y * R.j + R.z * R.k
    >>> dot(v1, v2)
    R.x + R.y + R.z

    """
    if isinstance(vect1, Add):
        return Add.fromiter(dot(i, vect2) for i in vect1.args)
    if isinstance(vect2, Add):
        return Add.fromiter(dot(vect1, i) for i in vect2.args)
    if isinstance(vect1, BaseVector) and isinstance(vect2, BaseVector):
        if vect1._sys == vect2._sys:
            return S.One if vect1 == vect2 else S.Zero
        try:
            from .functions import express
            return dot(vect1, express(vect2, vect1._sys))
        except:
            return Dot(vect1, vect2)
    if isinstance(vect1, VectorZero) or isinstance(vect2, VectorZero):
        return S.Zero
    if isinstance(vect1, VectorMul):
        v1, m1 = next(iter(vect1.components.items()))
        return m1*dot(v1, vect2)
    if isinstance(vect2, VectorMul):
        v2, m2 = next(iter(vect2.components.items()))
        return m2*dot(vect1, v2)

    return Dot(vect1, vect2)


def _vect_div(one, other):
    """ Helper for division involving vectors. """
    if isinstance(one, Vector) and isinstance(other, Vector):
        raise TypeError("Cannot divide two vectors")
    elif isinstance(one, Vector):
        if other == S.Zero:
            raise ValueError("Cannot divide a vector by zero")
        return VectorMul(one, Pow(other, S.NegativeOne))
    else:
        raise TypeError("Invalid division involving a vector")


Vector._expr_type = Vector
Vector._mul_func = VectorMul
Vector._add_func = VectorAdd
Vector._zero_func = VectorZero
Vector._base_func = BaseVector
Vector._div_helper = _vect_div
Vector.zero = VectorZero()
