import numpy
import operator

from math import sqrt

from amuse.support import exceptions
from amuse.support import console

from amuse.support.core import late
from amuse.support.core import compare_version_strings
from amuse.units import core
from amuse.units.si import none
from amuse.units.core import zero_unit

try:
    import astropy.units
    import amuse.units.si
    HAS_ASTROPY = True
except ImportError:
    HAS_ASTROPY = False

"""
"""
class Quantity(object):
    """
    A Quantity objects represents a scalar or vector with a
    specific unit. Quantity is an abstract base class
    for VectorQuantity and ScalarQuantity.

    Quantities should be constructed using *or-operator* ("|"),
    *new_quantity* or *unit.new_quantity*.

    Quantities emulate numeric types.

    Examples

    >>> from amuse.units import units
    >>> 100 | units.m
    quantity<100 m>
    >>> (100 | units.m) + (1 | units.km)
    quantity<1100.0 m>

    Quantities can be tested

    >>> from amuse.units import units
    >>> x = 100 | units.m
    >>> x.is_quantity()
    True
    >>> x.is_scalar()
    True
    >>> x.is_vector()
    False
    >>> v = [100, 200, 300] | units.g
    >>> v.is_quantity()
    True
    >>> v.is_scalar()
    False
    >>> v.is_vector()
    True

    Quantities can be converted to numbers

    >>> from amuse.units import units
    >>> x = 1000.0 | units.m
    >>> x.value_in(units.m)
    1000.0
    >>> x.value_in(units.km)
    1.0
    >>> x.value_in(units.g) # but only if the units are compatible!
    Traceback (most recent call last):
        File "<stdin>", line 1, in ?
    IncompatibleUnitsException: Cannot express m in g, the units do not have the same bases


    """
    __slots__ = ['unit']

    __array_priority__ = 101

    def __init__(self, unit):
        self.unit = unit

    def __str__(self):
        return console.current_printing_strategy.quantity_to_string(self)

    def is_quantity(self):
        """
        True for all quantities.
        """
        return True

    def is_scalar(self):
        """
        True for scalar quantities.
        """
        return False

    def is_vector(self):
        """
        True for vector quantities.
        """
        return False

    def __repr__(self):
        return 'quantity<'+str(self)+'>'

    def __add__(self, other):
        if self.unit.is_zero():
            other=to_quantity(other)
            return new_quantity(other.number, other.unit)
        else:
            other = to_quantity(other)
            factor = other.unit.conversion_factor_from(self.unit)
            return new_quantity(self.number + factor*other.number, self.unit)
    __radd__ = __add__

    def __sub__(self, other):
        if self.unit.is_zero():
            return -other
        else:
            other_in_my_units = to_quantity(other).as_quantity_in(self.unit)
            return new_quantity(self.number - other_in_my_units.number, self.unit)

    def __rsub__(self, other):
        if self.unit.is_zero():
            return new_quantity(other.number, other.unit)
        other_in_my_units = to_quantity(other).as_quantity_in(self.unit)
        return new_quantity(other_in_my_units.number - self.number, self.unit)

    def __mul__(self, other):
        other = to_quantity(other)
        return new_quantity_nonone(self.number * other.number, (self.unit * other.unit).to_simple_form())

    __rmul__ = __mul__

    def __pow__(self, other):
        return new_quantity(self.number ** other, self.unit ** other)

    def __truediv__(self, other):
        other = to_quantity(other)
        return new_quantity_nonone(operator.__truediv__(self.number,other.number), (self.unit / other.unit).to_simple_form())

    def __rtruediv__(self, other):
        return new_quantity_nonone(operator.__truediv__(other,self.number), (1.0 / self.unit).to_simple_form())

    def __floordiv__(self, other):
        other = to_quantity(other)
        return new_quantity_nonone(operator.__floordiv__(self.number,other.number), (self.unit / other.unit).to_simple_form())

    def __rfloordiv__(self, other):
        return new_quantity_nonone(operator.__floordiv__(other,self.number), (1.0 / self.unit).to_simple_form())

    def __div__(self, other):
        other = to_quantity(other)
        return new_quantity_nonone(self.number/other.number, (self.unit / other.unit).to_simple_form())

    def __rdiv__(self, other):
        return new_quantity_nonone(other/self.number, (1.0 / self.unit).to_simple_form())

    def __mod__(self, other):
        other_in_my_units = to_quantity(other).as_quantity_in(self.unit)
        return new_quantity_nonone(numpy.mod(self.number , other_in_my_units.number), self.unit)

    def __rmod__(self, other):
        other_in_my_units = to_quantity(other).as_quantity_in(self.unit)
        return new_quantity_nonone(numpy.mod(other_in_my_units.number , self.number), self.unit)

    def in_base(self):
        unit=self.unit.base_unit()
        return self.as_quantity_in(unit)

    def sqrt(self):
        """Calculate the square root of each component

        >>> from amuse.units import units
        >>> s1 = 144.0 | units.m**2
        >>> s1.sqrt()
        quantity<12.0 m>
        >>> v1 = [16.0, 25.0, 36.0] | units.kg
        >>> v1.sqrt()
        quantity<[4.0, 5.0, 6.0] kg**0.5>
        """
        return new_quantity(numpy.sqrt(self.number), (self.unit ** 0.5).to_simple_form())




    def as_quantity_in(self, another_unit):
        """
        Reproduce quantity in another unit.
        The new unit must have the same basic si quantities.

        :argument another_unit: unit to convert quantity to
        :returns: quantity converted to new unit
        """
        if isinstance(another_unit, Quantity):
            raise exceptions.AmuseException("Cannot expres a unit in a quantity")
        factor = self.unit.conversion_factor_from(another_unit)
        return new_quantity(self.number * factor, another_unit)

    in_=as_quantity_in

    def as_string_in(self, another_unit):
        """
        Create a string representing the quantity in another unit.
        The new unit must have the same basic si quantities.

        :argument another_unit: unit to convert quantity to
        :returns: string representing quantity converted to new unit
        """
        return console.DefaultPrintingStrategy().quantity_to_string(self.as_quantity_in(another_unit))

    def value_in(self, unit):
        """
        Return a numeric value (for scalars) or array (for vectors)
        in the given unit.

        A number is returned without any unit information. Use this
        function only to transfer values to other libraries that have
        no support for quantities (for example plotting).

        :argument unit: wanted unit of the value
        :returns: number in the given unit

        >>> from amuse.units import units
        >>> x = 10 | units.km
        >>> x.value_in(units.m)
        10000.0

        """
        value_of_unit_in_another_unit = self.unit.value_in(unit)
        return self.number * value_of_unit_in_another_unit

    def __abs__(self):
        """
        Return the absolute value of this quantity

        >>> from amuse.units import units
        >>> x = -10 | units.km
        >>> print abs(x)
        10 km
        """
        return new_quantity(abs(self.number), self.unit)

    def __neg__(self):
        """
        Unary minus.

        >>> from amuse.units import units
        >>> x = -10 | units.km
        >>> print -x
        10 km
        """
        return new_quantity(-self.number, self.unit)

    def __lt__(self, other):
        return self.value_in(self.unit) < to_quantity(other).value_in(self.unit)

    def __gt__(self, other):
        return self.value_in(self.unit) > to_quantity(other).value_in(self.unit)

    def __eq__(self, other):
        return self.value_in(self.unit) == to_quantity(other).value_in(self.unit)

    def __ne__(self, other):
        return self.value_in(self.unit) != to_quantity(other).value_in(self.unit)

    def __le__(self, other):
        return self.value_in(self.unit) <= to_quantity(other).value_in(self.unit)

    def __ge__(self, other):
        return self.value_in(self.unit) >= to_quantity(other).value_in(self.unit)

    if HAS_ASTROPY:
        def as_astropy_quantity(self):
            return to_astropy(self)


class ScalarQuantity(Quantity):
    """
    A ScalarQuantity object represents a physical scalar
    quantity.
    """
    __slots__ = ['number']

    def __init__(self, number, unit):
        # Quantity.__init__(self, unit)
        # commented out super call, this speeds thing up
        self.unit = unit
        if unit.dtype is None:
            self.number = number
        else:
            if isinstance(unit.dtype, numpy.dtype):
                self.number = unit.dtype.type(number)
            else:
                self.number = unit.dtype(number)


    def is_scalar(self):
        return True

    def as_vector_with_length(self, length):
        return VectorQuantity(numpy.ones(length, dtype=self.unit.dtype) * self.number, self.unit)


    def reshape(self, shape):
        if shape == -1 or (len(shape) == 1 and shape[0] == 1):
            return VectorQuantity([self.number], self.unit)
        else:
            raise exceptions.AmuseException("Cannot reshape a scalar to vector of shape '{0}'".format(shape))

    def __getitem__(self, index):
        if index == 0:
            return self
        else:
            raise exceptions.AmuseException("ScalarQuantity does not support indexing")

    def copy(self):
        return new_quantity(self.number, self.unit)

    def to_unit(self):
        in_base=self.in_base()
        return in_base.number * in_base.unit

    def __getstate__(self):
        return (self.unit, self.number)

    def round(self, decimals = 0):
        return new_quantity(numpy.round(self.number, decimals), self.unit)


    def new_zeros_array(self, length):
        array = numpy.zeros(length, dtype=self.unit.dtype)
        return new_quantity(array, self.unit)

    def __setstate__(self, x):
        self.unit = x[0]
        self.number = x[1]

    def sum(self, axis=None, dtype=None, out=None):
        return self
    def cumsum(self, axis=None, dtype=None, out=None):
        return self
    def prod(self, axis=None, dtype=None):
        return self
    def min(self, axis = None):
        return self
    def max(self, axis = None):
        return self
    amin=min
    amax=max
    def sorted(self):
        return self

    def as_unit(self):
        return self.number * self.unit

class _flatiter_wrapper(object):
    def __init__(self, quantity):
        self.flat=quantity.number.flat
        self.quantity=quantity
    def __iter__(self):
        return self
    def __next__(self):
        return new_quantity(next(self.flat),self.quantity.unit)
    def __getitem__(self,x): 
        return new_quantity(self.flat[x], self.quantity.unit)
    def __setitem__(self,index,x):
        return self.flat.__setitem__(index,x.value_in(self.quantity.unit))
    @property
    def base(self):
        return self.quantity
    @property
    def index(self):
        return self.flat.index
    @property
    def coords(self):
        return self.flat.coords
    @property
    def unit(self):
        return self.quantity.unit
    @property
    def number(self):
        return self.flat
    def copy(self):
        return new_quantity(self.flat.copy(), self.quantity.unit)
    def is_quantity(self):
        return True
    def value_in(self, unit):
        return self.copy().value_in(unit)
    def as_quantity_in(self, unit):
        return self.copy().as_quantity_in(unit)
    # todo: add as required

class VectorQuantity(Quantity):
    """
    A VectorQuantity object represents a physical vector
    quantity.

    >>> from amuse.units import units
    >>> v1 = [0.0, 1.0, 2.0] | units.kg
    >>> v2 = [2.0, 4.0, 6.0] | units.kg
    >>> v1 + v2
    quantity<[2.0, 5.0, 8.0] kg>
    >>> len(v1)
    3
    """
    __slots__ = ['_number']

    def __init__(self, array, unit):
        Quantity.__init__(self, unit)
        if unit is None:
            self._number = numpy.array((), dtype='float64')
        else:
            self._number = numpy.asarray(array, dtype=unit.dtype)

    @classmethod
    def new_from_scalar_quantities(cls, *values):
        unit=to_quantity(values[0]).unit
        try:
            array=[value_in(x,unit) for x in values]
        except core.IncompatibleUnitsException:
            raise exceptions.AmuseException("not all values have conforming units")
        return cls(array, unit)

    @classmethod
    def new_from_array(cls, array):
        shape=array.shape
        vector=cls.new_from_scalar_quantities(*array.flat)
        return vector.reshape(shape)

    def aszeros(self):
        return new_quantity(numpy.zeros(self.shape, dtype=self.number.dtype), self.unit)


    def new_zeros_array(self, length):
        array = numpy.zeros(length, dtype=self.unit.dtype)
        return type(self)(array, self.unit)

    @classmethod
    def zeros(cls, length, unit):
        array = numpy.zeros(length, dtype=unit.dtype)
        return cls(array, unit)

    @classmethod
    def arange(cls, begin, end, step):
        return arange(begin, end, step)

    @property
    def shape(self):
        return self.number.shape

    @property
    def dtype(self):
        return self.number.dtype

    def flatten(self):
        return new_quantity(self.number.flatten(), self.unit)
    
    @property
    def flat(self):                
        return _flatiter_wrapper(self)
        
    def is_vector(self):
        return True


    def as_vector_with_length(self, length):
        if len(self)==length:
            return self.copy()
        if len(self)==1:
            return self.new_from_scalar_quantities(*[self[0]]*length)
        raise exceptions.AmuseException("as_vector_with_length only valid for same length or 1")

    def as_vector_quantity(self):
        return self

    def __len__(self):
        return len(self._number)

    def split(self, indices_or_sections, axis = 0):
        parts = numpy.split(self.number, indices_or_sections, axis)
        return [VectorQuantity(x, self.unit) for x in parts]

    def array_split(self, indices_or_sections, axis = 0):
        parts = numpy.array_split(self.number, indices_or_sections, axis)
        return [VectorQuantity(x, self.unit) for x in parts]

    def sum(self, axis=None, dtype=None, out=None):
        """Calculate the sum of the vector components

        >>> from amuse.units import units
        >>> v1 = [0.0, 1.0, 2.0] | units.kg
        >>> v1.sum()
        quantity<3.0 kg>
        """
        return new_quantity(self.number.sum(axis, dtype, out), self.unit)

    def cumsum(self, axis=None, dtype=None, out=None):
        """ Calculate  the cumulative sum of the elements along a given axis. """

        return new_quantity(numpy.cumsum(self.number, axis, dtype, out), self.unit)

    def prod(self, axis=None, dtype=None):
        """Calculate the product of the vector components

        >>> from amuse.units import units
        >>> v1 = [1.0, 2.0, 3.0] | units.m
        >>> v1.prod()
        quantity<6.0 m**3>
        >>> v1 = [[2.0, 3.0], [2.0, 4.0], [5.0,3.0] ] | units.m
        >>> v1.prod()
        quantity<720.0 m**6>
        >>> v1.prod(0)
        quantity<[20.0, 36.0] m**3>
        >>> v1.prod(1)
        quantity<[6.0, 8.0, 15.0] m**2>

        >>> v1 = [[[2.0, 3.0], [2.0, 4.0]],[[5.0, 2.0], [3.0, 4.0]]] | units.m
        >>> v1.prod() # doctest:+ELLIPSIS
        quantity<5760.0 m**8...>
        >>> v1.prod(0)
        quantity<[[10.0, 6.0], [6.0, 16.0]] m**2>
        >>> v1.prod(1)
        quantity<[[4.0, 12.0], [15.0, 8.0]] m**2>
        >>> v1.prod(2)
        quantity<[[6.0, 8.0], [10.0, 12.0]] m**2>
        """
        if axis is None:
            return new_quantity_nonone(self.number.prod(axis, dtype), self.unit ** numpy.prod(self.number.shape))
        else:
            return new_quantity_nonone(self.number.prod(axis, dtype), self.unit ** self.number.shape[axis])



    def inner(self, other):
        """Calculate the inner product of self with other.

        >>> from amuse.units import units
        >>> v1 = [1.0, 2.0, 3.0] | units.m
        >>> v1.inner(v1)
        quantity<14.0 m**2>
        """
        other = to_quantity(other)
        return new_quantity_nonone(numpy.inner(self._number, other._number), (self.unit * other.unit).to_simple_form())


    def length_squared(self):
        """Calculate the squared length of the vector.

        >>> from amuse.units import units
        >>> v1 = [2.0, 3.0, 4.0] | units.m
        >>> v1.length_squared()
        quantity<29.0 m**2>
        """
        return (self * self).sum()

    def length(self):
        """Calculate the length of the vector.

        >>> from amuse.units import units
        >>> v1 = [0.0, 3.0, 4.0] | units.m
        >>> v1.length()
        quantity<5.0 m>
        """
        return self.length_squared().sqrt()

    def lengths(self):
        """Calculate the length of the vectors in this vector.

        >>> from amuse.units import units
        >>> v1 = [[0.0, 3.0, 4.0],[2.0 , 2.0 , 1.0]] | units.m
        >>> v1.lengths()
        quantity<[5.0, 3.0] m>
        """
        return self.lengths_squared().sqrt()

    def lengths_squared(self):
        """Calculate the length of the vectors in this vector

        >>> from amuse.units import units
        >>> v1 = [[0.0, 3.0, 4.0],[4.0, 2.0, 1.0]] | units.m
        >>> v1.lengths_squared()
        quantity<[25.0, 21.0] m**2>
        """
        return (self.unit**2).new_quantity((self.number * self.number).sum(self.number.ndim - 1))

    def __getitem__(self, index):
        """Return the "index" component as a quantity.

        :argument index: index of the component, valid values
            for 3 dimensional vectors are: ``[0,1,2]``
        :returns: quantity with the same units

        >>> from amuse.units import si
        >>> vector = [0.0, 1.0, 2.0] | si.kg
        >>> print vector[1]
        1.0 kg
        >>> print vector[0:2]
        [0.0, 1.0] kg
        >>> print vector[[0,2,]]
        [0.0, 2.0] kg
        """
        return new_quantity(self._number[index], self.unit)

    def take(self, indices):
        return VectorQuantity(self._number.take(indices), self.unit)

    def put(self, indices, vector):
        try:
            if self.unit.is_zero():
                self.unit = vector.unit

            self._number.put(indices, vector.value_in(self.unit))
        except AttributeError:
            if not is_quantity(vector):
                raise ValueError("Tried to put a non quantity value in a quantity")
            raise

    def __setitem__(self, index, quantity):
        """Update the "index" component to the specified quantity.

        :argument index: index of the component, valid values
            for 3 dimensional vectors are: ``[0,1,2]``
        :quantity: quantity to set, will be converted to
            the unit of this vector

        >>> from amuse.units import si
        >>> vector = [0.0, 1.0, 2.0] | si.kg
        >>> g = si.kg / 1000
        >>> vector[1] = 3500 | g
        >>> print vector
        [0.0, 3.5, 2.0] kg
        """
        quantity = as_vector_quantity(quantity)
        if self.unit.is_zero():
            self.unit = quantity.unit
        self._number[index] = quantity.value_in(self.unit)

    @property
    def number(self):
        return self._number

    @property
    def x(self):
        """The x axis component of a 3 dimensional vector.
        This is equavalent to the first component of vector.

        :returns: x axis component as a quantity

        >>> from amuse.units import si
        >>> vector = [1.0, 2.0, 3.0] | si.kg
        >>> print vector.x
        1.0 kg
        """
        return new_quantity(self.number[numpy.newaxis, ..., 0][0], self.unit)

    @property
    def y(self):
        """The y axis component of a 3 dimensional vector.
        This is equavalent to the second component of vector.

        :returns: y axis component as a quantity

        >>> from amuse.units import si
        >>> vector = [1.0, 2.0, 3.0] | si.kg
        >>> print vector.y
        2.0 kg
        """
        return new_quantity(self.number[numpy.newaxis, ..., 1][0], self.unit)

    @property
    def z(self):
        """The z axis component of a 3 dimensional vector.
        This is equavalent to the third component of vector.

        :returns: z axis component as a quantity

        >>> from amuse.units import si
        >>> vector = [1.0, 2.0, 3.0] | si.kg
        >>> print vector.z
        3.0 kg
        """
        return new_quantity(self.number[numpy.newaxis, ..., 2][0], self.unit)

    def indices(self):
        for x in len(self._number):
            yield x

    def copy(self):
        return new_quantity(self.number.copy(), self.unit)

    def norm_squared(self):
        return self.length_squared()

    def norm(self):
        return self.length()


    def append(self, scalar_quantity):
        """
        Append a scalar quantity to this vector.

        >>> from amuse.units import si
        >>> vector = [1.0, 2.0, 3.0] | si.kg
        >>> vector.append(4.0 | si.kg)
        >>> print vector
        [1.0, 2.0, 3.0, 4.0] kg
        """
        append_number = numpy.array(scalar_quantity.value_in(self.unit)) # fix for deg, unitless
        # The following lines make sure that appending vectors works as expected,
        # e.g. ([]|units.m).append([1,2,3]|units.m) -> [[1,2,3]] | units.m
        # e.g. ([[1,2,3]]|units.m).append([4,5,6]|units.m) -> [[1,2,3],[4,5,6]] | units.m
        if (append_number.shape and (len(self._number) == 0 or self._number.shape[1:] == append_number.shape)):
            new_shape = [1 + self._number.shape[0]] + list(append_number.shape)
        else:
            new_shape = -1
        self._number = numpy.append(self._number, append_number).reshape(new_shape)

    def extend(self, vector_quantity):
        """
        Concatenate the vector quantity to this vector.
        If the units differ, the vector_quantity argument
        is converted to the units of this vector.

        >>> from amuse.units import units
        >>> vector1 = [1.0, 2.0, 3.0] | units.kg
        >>> vector2 = [1500, 2500, 6000] | units.g
        >>> vector1.extend(vector2)
        >>> print vector1
        [1.0, 2.0, 3.0, 1.5, 2.5, 6.0] kg
        """
        self._number = numpy.concatenate((self._number, vector_quantity.value_in(self.unit)))

    def prepend(self, scalar_quantity):
        """
        Prepend the scalar quantity before this vector.
        If the units differ, the scalar_quantity argument
        is converted to the units of this vector.

        >>> from amuse.units import units
        >>> vector1 = [1.0, 2.0, 3.0] | units.kg
        >>> vector1.prepend(0.0 | units.kg)
        >>> print vector1
        [0.0, 1.0, 2.0, 3.0] kg
        """
        self._number = numpy.concatenate(([scalar_quantity.value_in(self.unit)], self._number))

    def minimum(self, other):
        """
        Return the minimum of self and the argument.

        >>> from amuse.units import si
        >>> v1 = [1.0, 2.0, 3.0] | si.kg
        >>> v2 = [0.0, 3.0, 4.0] | si.kg
        >>> v1.minimum(v2)
        quantity<[0.0, 2.0, 3.0] kg>

        """
        other_in_my_units = other.as_quantity_in(self.unit)
        is_smaller_than = self.number < other_in_my_units.number
        values = numpy.where(is_smaller_than, self.number, other_in_my_units.number)
        return VectorQuantity(values, self.unit)

    def maximum(self, other):
        """
        Return the maximum of self and the argument.

        >>> from amuse.units import si
        >>> v1 = [1.0, 2.0, 3.0] | si.kg
        >>> v2 = [0.0, 3.0, 4.0] | si.kg
        >>> v1.maximum(v2)
        quantity<[1.0, 3.0, 4.0] kg>
        """
        other_in_my_units = other.as_quantity_in(self.unit)
        is_larger_than = self.number > other_in_my_units.number
        values = numpy.where(is_larger_than, self.number, other_in_my_units.number)
        return VectorQuantity(values, self.unit)

    def max(self, axis = None):
        """
        Return the maximum along an axis.

        >>> from amuse.units import si
        >>> v1 = [1.0, 2.0, 3.0] | si.kg
        >>> v1.amax()
        quantity<3.0 kg>
        """

        return self.unit.new_quantity(numpy.amax(self.number, axis = axis))

    def min(self, axis = None):
        """
        Return the minimum value along an axis.

        >>> from amuse.units import si
        >>> v1 = [1.0, 2.0, 3.0] | si.kg
        >>> v1.amin()
        quantity<1.0 kg>
        """

        return self.unit.new_quantity(numpy.amin(self.number, axis = axis))
    amin=min
    amax=max

    def argmax(self, axis = None):
        """
        Return the indices of the maximum values along an axis.

        >>> from amuse.units import si
        >>> v1 = [[1.0, 2.0, 3.0], [2.5, 2.5, 2.5]] | si.kg
        >>> v1.argmax(axis=0)
        array([1, 1, 0])
        """
        return numpy.argmax(self.number, axis = axis)

    def argmin(self, axis = None):
        """
        Return the indices of the minimum values along an axis.

        >>> from amuse.units import si
        >>> v1 = [[1.0, 2.0, 3.0], [2.5, 2.5, 2.5]] | si.kg
        >>> v1.argmin(axis=0)
        array([0, 0, 1])
        """

        return numpy.argmin(self.number, axis = axis)

    def sorted(self):
        """
        Return a new vector with all items sorted.

        >>> from amuse.units import si
        >>> v1 = [3.0, 1.0, 2.0] | si.kg
        >>> v1.sorted()
        quantity<[1.0, 2.0, 3.0] kg>
        """
        sorted_values = numpy.sort(self.number)
        return VectorQuantity(sorted_values, self.unit)

    def argsort(self, **options):
        """
        Returns the indices that would sort an array.

        >>> from amuse.units import si
        >>> v1 = [3.0, 1.0, 2.0] | si.kg
        >>> v1.argsort()
        array([1, 2, 0])
        """
        return numpy.argsort(self.number, **options)

    def argmax(self, **options):
        """
        Returns the index of the maximum item

        >>> from amuse.units import si
        >>> v1 = [1.0, 3.0, 2.0] | si.kg
        >>> v1.argmax()
        1
        """
        return numpy.argmax(self.number, **options)

    def sorted_with(self, *others):
        """
        Return a new vector with all items sorted. Perform
        all the same move operations on the other vectors.

        :argument: kind, the sort method for supported kinds see
            the numpy.sort documentation

        >>> from amuse.units import si
        >>> v1 = [3.0, 1.0, 2.0] | si.kg
        >>> v2 = [2.0, 3.0, 2.0] | si.m
        >>> v3 = [1.0, 4.0, 5.0] | si.s
        >>> list(v1.sorted_with(v2, v3))
        [quantity<[1.0, 2.0, 3.0] kg>, quantity<[3.0, 2.0, 2.0] m>, quantity<[4.0, 5.0, 1.0] s>]
        """
        indices = numpy.lexsort([self.number])
        vectors = []
        vectors.append(self)
        for x in others:
            vectors.append(x)

        for x in vectors:
            yield VectorQuantity(numpy.take(x.number, indices), x.unit)

    def accumulate(self):
        return VectorQuantity(numpy.add.accumulate(self.number), self.unit)

    def reshape(self, shape):
        return VectorQuantity(self.number.reshape(shape), self.unit)

    def transpose(self, axes=None):
        return VectorQuantity(self.number.transpose(axes), self.unit)

    @property
    def T(self):
        return VectorQuantity(self.number.T, self.unit)

    def mean(self, axis=None, dtype=None, out=None):
        return new_quantity(self.number.mean(axis, dtype, out), self.unit)

    def median(self, **kwargs):
        return new_quantity(numpy.median(self.number, **kwargs), self.unit)

    def std(self, axis=None, dtype=None, out=None, ddof=0):
        return new_quantity(self.number.std(axis, dtype, out, ddof), self.unit)

    def cross(self, other, axisa=-1, axisb=-1, axisc=-1, axis=None):
        """
        Return the cross product of this vector quantity with the supplied vector (quantity).
        """
        other = to_quantity(other)
        return new_quantity_nonone(
            numpy.cross(self.number, other.number, axisa=axisa, axisb=axisb, axisc=axisc, axis=axis),
            (self.unit * other.unit).to_simple_form()
        )

    def dot(self, other, **kwargs):
        """
        Return the dot product of this vector quantity with the supplied vector (quantity).

        >>> from amuse.units import units
        >>> v1 = [1.0, 2.0, 3.0] | units.m
        >>> v1.dot(v1)
        quantity<14.0 m**2>
        """
        other = to_quantity(other)
        return new_quantity_nonone(
            numpy.dot(self.number, other.number, **kwargs),
            (self.unit * other.unit).to_simple_form()
        )

    def __getstate__(self):
        return (self.unit, self.number)

    def __setstate__(self, x):
        self.unit = x[0]
        self._number = x[1]


class ZeroQuantity(Quantity):
    """
    A ZeroQuantity object represents zero in all units and
    can be used as the start for summing up purposes.

    >>> from amuse.units import si
    >>> x = zero
    >>> x += 2.0 | si.kg
    >>> x
    quantity<2.0 kg>

    """


    def __init__(self):
        Quantity.__init__(self, zero_unit())
        self.base = ()
        self.factor = 1
        self.number = 0.0
        self.dtype = 'float64'

    def is_scalar(self):
        """
        True for scalar quantities.
        """
        return False

    def is_vector(self):
        """
        True for vector quantities.
        """
        return False

    def is_non_numeric(self):
        return False

    def iskey(self):
        return False

    def __str__(self):
        return "zero"

    def __add__(self, other):
        return other

    def __sub__(self, other):
        return -other


    def __mul__(self, other):
        return self


    def __pow__(self, other):
        return self

    def __rmul__(self, other):
        return self


    def __truediv__(self, other):
        return self

    def __rtruediv__(self, other):
        return other/self.number

    def __div__(self, other):
        return self.__truediv__(other)

    def __rdiv__(self, other):
        return self.__rtruediv__(other)

    def in_base(self):
        return self


    def new_zeros_array(self, length):
        array = numpy.zeros(length, dtype=self.dtype)
        return new_quantity(array, zero_unit())

    def sqrt(self):
        return self

    def as_quantity_in(self, another_unit):
        return new_quantity(self.number, another_unit)

    def value_in(self, unit):
        return self.number

    def __abs__(self):
        return self

    def __neg__(self):
        return self

    def as_vector_with_length(self, length):
        return self.new_zeros_array(length)

    def __reduce__(self):
        return "zero"

    def __lt__(self, other):
        other_as_q=to_quantity(other)
        return 0 < other_as_q.value_in(other_as_q.unit)

    def __gt__(self, other):
        other_as_q=to_quantity(other)
        return 0 > other_as_q.value_in(other_as_q.unit)

    def __eq__(self, other):
        other_as_q=to_quantity(other)
        return 0 == other_as_q.value_in(other_as_q.unit)

    def __ne__(self, other):
        other_as_q=to_quantity(other)
        return 0 != other_as_q.value_in(other_as_q.unit)

    def __le__(self, other):
        other_as_q=to_quantity(other)
        return 0 <= other_as_q.value_in(other_as_q.unit)

    def __ge__(self, other):
        other_as_q=to_quantity(other)
        return 0 >= other_as_q.value_in(other_as_q.unit)



zero = ZeroQuantity()

class NonNumericQuantity(Quantity):
    """
    A Non Numeric Quantity object represents a quantity without
    a physical meaning.

    These Quantity objects cannot be used in
    numeric operations (like addition or multiplication). Also,
    conversion to another unit is not possible.

    Examples are string quantities or enumerated value quantities.

    >>> from amuse.units.core import enumeration_unit
    >>> my_unit = enumeration_unit(
    ...     "x",
    ...     "x",
    ...     [1,3,4],
    ...     ["first", "second", "third"])
    ...
    >>> 3 | my_unit
    quantity<3 - second>
    >>> (3 | my_unit).value_in(my_unit)
    3

    """

    def __init__(self, value, unit):
        Quantity.__init__(self, unit)
        self.value = value
        if not unit.is_valid_value(value):
            raise exceptions.AmuseException("<{0}> is not a valid value for {1!r}".format(value, unit))

    def as_quantity_in(self, another_unit):
        if not another_unit == self.unit:
            raise exceptions.AmuseException("Cannot convert non-numeric quantities in to another unit")

        return new_quantity(self.value, another_unit)

    def value_in(self, unit):
        if not unit == self.unit:
            raise exceptions.AmuseException("Cannot convert non-numeric quantities in to another unit")

        return self.value

    def __str__(self):
        return self.unit.value_to_string(self.value)

    def __repr__(self):
        return 'quantity<'+str(self.value)+ ' - ' +str(self)+'>'


    def as_vector_with_length(self, length):
        return VectorQuantity(numpy.array([self.value] * length), self.unit)

    def as_vector_quantity(self):
        return VectorQuantity([self.value], self.unit)

    def new_zeros_array(self, length):
        array = numpy.zeros(length, dtype=self.unit.dtype)
        return new_quantity(array, self.unit)


    def __getstate__(self):
        return (self.unit, self.value)

    def __setstate__(self, x):
        self.unit = x[0]
        self.value = x[1]

class AdaptingVectorQuantity(VectorQuantity):
    """
    Adapting vector quanity objects will adapt their units to the
    first object added to the vector
    """

    def __init__(self, value = [], unit = None):
        VectorQuantity.__init__(self, value, unit)
        del self._number
        self._number_list = list(value)
        if unit is None:
            self.append = self.append_start
            self.prepend = self.prepend_start
        else:
            self.append = self.append_normal
            self.prepend = self.prepend_normal

    def __getattr__(self, attribute):
        if attribute == "_number":
            if self.unit is None:
                return numpy.array(self._number_list)
            else:
                return numpy.array(self._number_list, dtype=self.unit.dtype)
        else:
            raise AttributeError

    def append_start(self, quantity):
        self.unit = quantity.unit
        self._number_list.append(quantity.value_in(self.unit))
        self.append = self.append_normal
        self.prepend = self.prepend_normal

    def append_normal(self, quantity):
        self._number_list.append(quantity.value_in(self.unit))

    prepend_start = append_start

    def prepend_normal(self, quantity):
        self._number_list.insert(0, quantity.value_in(self.unit))

    def extend(self, quantity):
        for x in quantity:
            self.append(x)

    def __setitem__(self, index, quantity):
        quantity_in_my_units = quantity.as_quantity_in(self.unit)
        self._number_list[index] = quantity_in_my_units.number
        self._remove_cached_number()

    def __getitem__(self, index):
        return new_quantity(self.number[index], self.unit)

    def __str__(self):
        if self.unit is None:
            return str(self._number_list)
        else:
            return console.current_printing_strategy.quantity_to_string(self)

__array_like =  (list, tuple, numpy.ndarray)
def new_quantity(value, unit):
    """Create a new Quantity object.

    :argument value: numeric value of the quantity, can be
        a number or a sequence (list or ndarray)
    :argument unit: unit of the quantity
    :returns: new ScalarQuantity or VectorQuantity object
    """
    if isinstance(value, __array_like):
        return VectorQuantity(value, unit)
    if unit.is_non_numeric():
        return NonNumericQuantity(value, unit)
    return ScalarQuantity(value, unit)

def new_quantity_from_unit(unit, value):
    return new_quantity(value, unit)

core.unit.new_quantity = new_quantity_from_unit

def new_quantity_nonone(value, unit):
    """Create a new Quantity object.

    :argument value: numeric value of the quantity, can be
        a number or a sequence (list or ndarray)
    :argument unit: unit of the quantity
    :returns: new ScalarQuantity or VectorQuantity object
    """
    if not unit.base:
        if isinstance(value, __array_like):
            return numpy.asarray(value) * unit.factor
        else:
            return value * unit.factor
    if isinstance(value, list):
        return VectorQuantity(value, unit)
    if isinstance(value, tuple):
        return VectorQuantity(value, unit)
    if isinstance(value, numpy.ndarray):
        return VectorQuantity(value, unit)
    if unit.is_non_numeric():
        return NonNumericQuantity(value, unit)
    return ScalarQuantity(value, unit)

def is_quantity(x):
    return hasattr(x, "is_quantity") and x.is_quantity()

def is_unit(x):
    return hasattr(x, "base")

def isNumber(x):
    try:
        return 0 == x*0
    except:
        return False

def as_vector_quantity(value):
    if is_quantity(value): 
        return value
    else:
        if isinstance(value, numpy.ndarray) and  numpy.issubdtype(value.dtype, numpy.number):
            return new_quantity(value, none)
        if isinstance(value, __array_like): # its not a homogeneous numpy array, this can be slow
            result = AdaptingVectorQuantity()
            for subvalue in value:
                result.append(as_vector_quantity(subvalue))
            return result
        else:
            if isNumber(value):
                return new_quantity(value, none)
            else:
                raise Exception("Cannot convert '{0!r}' to a vector quantity".format(value))

def to_quantity(x):
    if is_quantity(x):
        return x
    else:
        return new_quantity(x, none)

def as_quantity_in(x,unit):
    return to_quantity(x).as_quantity_in(unit)

def value_in(x,unit):
    return to_quantity(x).value_in(unit)

def concatenate(quantities):
    first = quantities[0]
    if not is_quantity(first):
        return numpy.concatenate(quantities)
    unit = first.unit
    numbers = list([x.value_in(unit) for x in quantities])
    concatenated = numpy.concatenate(numbers)
    return VectorQuantity(concatenated, unit)

def column_stack( args ):
    args_=[to_quantity(x) for x in args]
    units=set([x.unit for x in args_])
    if len(units)==1:
      return new_quantity(numpy.column_stack([x.number for x in args_]),args_[0].unit)
    else:
      return numpy.column_stack(args)

def stack( args ):
    args_=[to_quantity(x) for x in args]
    units=set([x.unit for x in args_])
    if len(units)==1:
      return new_quantity(numpy.stack([x.number for x in args_]),args_[0].unit)
    else:
      return numpy.stack(args)

def arange(start, stop, step):
    if not is_quantity(start):
        return numpy.arange(start, stop, step)

    unit = start.unit
    start_value = start.value_in(unit)
    stop_value = stop.value_in(unit)
    step_value = step.value_in(unit)
    array = numpy.arange(start_value, stop_value, step_value)
    return new_quantity(array, unit)


def linspace(start, stop, num = 50,  endpoint=True, retstep=False):
    if not is_quantity(start):
        return numpy.linspace(start, stop, num,  endpoint, retstep)

    unit = start.unit
    start_value = start.value_in(unit)
    stop_value = stop.value_in(unit)
    array = numpy.linspace(start_value, stop_value, num,  endpoint, retstep)

    if retstep:
        return new_quantity(array[0], unit), new_quantity(array[1], unit)
    else:
        return new_quantity(array, unit)

def separate_numbers_and_units(values):
    number = []
    unit = []
    for value in values:
        if is_quantity(value):
            number.append(value.number)
            unit.append(value.unit)
        else:
            number.append(value)
            unit.append(none)

    return number, unit

def meshgrid(*xi, **kwargs):
    unitless_xi, units = separate_numbers_and_units(xi)

    result = numpy.meshgrid(*unitless_xi, **kwargs)

    return [matrix | unit for matrix, unit in zip(result, units)]

def polyfit(x, y, deg):
    (x_number, y_number), (x_unit, y_unit) = separate_numbers_and_units([x, y])

    fit = numpy.polyfit(x_number, y_number, deg)
    fit = [f | y_unit/(x_unit**(deg-i)) for i, f in enumerate(fit)]

    return fit

def polyval(p, x):
    if len(p) == 1:
        return numpy.ones(x.shape) * p[0]

    p_number, p_unit = separate_numbers_and_units(p)
    y_unit = p_unit[-1].to_reduced_form()
    x_unit = (y_unit/p_unit[-2]).to_reduced_form()

    if x_unit != none:
        x = x.value_in(x_unit)

    value = numpy.polyval(p_number, x)

    return value | y_unit


def searchsorted(a, v, **kwargs):
    if is_quantity(a):
        return numpy.searchsorted(a.value_in(a.unit), v.value_in(a.unit), **kwargs)
    else:
        return numpy.searchsorted(a, v, **kwargs)

def sign(x):
    return numpy.sign(to_quantity(x).number)

if HAS_ASTROPY:
    def to_astropy(quantity):
        "Convert a quantity from AMUSE to Astropy"
        # NOTE: we need to go through SI base here because AMUSE and Astropy
        # don't necessarily agree on derived unit definitions...

        # Find the SI bases of the unit
        unit = quantity.unit
        unit_bases = unit.base

        # Find the quantity's value in base units
        value = quantity.value_in(unit.base_unit())

        # Reconstruct the quantity in Astropy units
        ap_quantity = value
        for base_unit in unit_bases:
            if base_unit[1] == amuse.units.si.m:
                ap_quantity = ap_quantity * astropy.units.m**base_unit[0]
            elif base_unit[1] == amuse.units.si.kg:
                ap_quantity = ap_quantity * astropy.units.kg**base_unit[0]
            elif base_unit[1] == amuse.units.si.s:
                ap_quantity = ap_quantity * astropy.units.s**base_unit[0]
            elif base_unit[1] == amuse.units.si.A:
                ap_quantity = ap_quantity * astropy.units.A**base_unit[0]
            elif base_unit[1] == amuse.units.si.K:
                ap_quantity = ap_quantity * astropy.units.K**base_unit[0]
            elif base_unit[1] == amuse.units.si.mol:
                ap_quantity = ap_quantity * astropy.units.mol**base_unit[0]
            elif base_unit[1] == amuse.units.si.cd:
                ap_quantity = ap_quantity * astropy.units.cd**base_unit[0]
        return ap_quantity

    def from_astropy(ap_quantity):
        "Convert a quantity from Astropy to AMUSE"
        # NOTE: we need to go through SI base here because AMUSE and Astropy
        # don't necessarily agree on derived unit definitions...

        # Find SI bases of the unit
        si_bases = ap_quantity.si.unit.bases
        si_powers = ap_quantity.si.unit.powers
        si_units = list(zip(si_powers, si_bases))

        # Find the quantity's value in base units
        si_value = ap_quantity.si.value

        # Reconstruct the quantity in AMUSE units
        amuse_quantity = si_value
        for base_unit in si_units:
            if base_unit[1].name == "m":
                amuse_quantity = amuse_quantity * (
                    1 | amuse.units.si.m**base_unit[0]
                )
            elif base_unit[1].name == "kg":
                amuse_quantity = amuse_quantity * (
                    1 | amuse.units.si.kg**base_unit[0]
                )
            elif base_unit[1].name == "s":
                amuse_quantity = amuse_quantity * (
                    1 | amuse.units.si.s**base_unit[0]
                )
            elif base_unit[1].name == "A":
                amuse_quantity = amuse_quantity * (
                    1 | amuse.units.si.A**base_unit[0]
                )
            elif base_unit[1].name == "K":
                amuse_quantity = amuse_quantity * (
                    1 | amuse.units.si.K**base_unit[0]
                )
            elif base_unit[1].name == "mol":
                amuse_quantity = amuse_quantity * (
                    1 | amuse.units.si.mol**base_unit[0]
                )
            elif base_unit[1].name == "cd":
                amuse_quantity = amuse_quantity * (
                    1 | amuse.units.si.cd**base_unit[0]
                )

        return amuse_quantity
