"""Tools for manipulating of large commutative expressions. """

from sympy.core.add import Add
from sympy.core.compatibility import iterable, is_sequence, SYMPY_INTS
from sympy.core.mul import Mul, _keep_coeff
from sympy.core.power import Pow
from sympy.core.basic import Basic, preorder_traversal
from sympy.core.expr import Expr
from sympy.core.sympify import sympify
from sympy.core.numbers import Rational, Integer, Number, I
from sympy.core.singleton import S
from sympy.core.symbol import Dummy
from sympy.core.coreerrors import NonCommutativeExpression
from sympy.core.containers import Tuple, Dict
from sympy.utilities import default_sort_key
from sympy.utilities.iterables import (common_prefix, common_suffix,
        variations, ordered)

from collections import defaultdict


_eps = Dummy(positive=True)


def _isnumber(i):
    return isinstance(i, (SYMPY_INTS, float)) or i.is_Number


def _monotonic_sign(self):
    """Return the value closest to 0 that ``self`` may have if all symbols
    are signed and the result is uniformly the same sign for all values of symbols.
    If a symbol is only signed but not known to be an
    integer or the result is 0 then a symbol representative of the sign of self
    will be returned. Otherwise, None is returned if a) the sign could be positive
    or negative or b) self is not in one of the following forms:

    - L(x, y, ...) + A: a function linear in all symbols x, y, ... with an
      additive constant; if A is zero then the function can be a monomial whose
      sign is monotonic over the range of the variables, e.g. (x + 1)**3 if x is
      nonnegative.
    - A/L(x, y, ...) + B: the inverse of a function linear in all symbols x, y, ...
      that does not have a sign change from positive to negative for any set
      of values for the variables.
    - M(x, y, ...) + A: a monomial M whose factors are all signed and a constant, A.
    - A/M(x, y, ...) + B: the inverse of a monomial and constants A and B.
    - P(x): a univariate polynomial

    Examples
    ========

    >>> from sympy.core.exprtools import _monotonic_sign as F
    >>> from sympy import Dummy
    >>> nn = Dummy(integer=True, nonnegative=True)
    >>> p = Dummy(integer=True, positive=True)
    >>> p2 = Dummy(integer=True, positive=True)
    >>> F(nn + 1)
    1
    >>> F(p - 1)
    _nneg
    >>> F(nn*p + 1)
    1
    >>> F(p2*p + 1)
    2
    >>> F(nn - 1)  # could be negative, zero or positive
    """
    if not self.is_extended_real:
        return

    if (-self).is_Symbol:
        rv = _monotonic_sign(-self)
        return rv if rv is None else -rv

    if not self.is_Add and self.as_numer_denom()[1].is_number:
        s = self
        if s.is_prime:
            if s.is_odd:
                return S(3)
            else:
                return S(2)
        elif s.is_composite:
            if s.is_odd:
                return S(9)
            else:
                return S(4)
        elif s.is_positive:
            if s.is_even:
                if s.is_prime is False:
                    return S(4)
                else:
                    return S(2)
            elif s.is_integer:
                return S.One
            else:
                return _eps
        elif s.is_extended_negative:
            if s.is_even:
                return S(-2)
            elif s.is_integer:
                return S.NegativeOne
            else:
                return -_eps
        if s.is_zero or s.is_extended_nonpositive or s.is_extended_nonnegative:
            return S.Zero
        return None

    # univariate polynomial
    free = self.free_symbols
    if len(free) == 1:
        if self.is_polynomial():
            from sympy.polys.polytools import real_roots
            from sympy.polys.polyroots import roots
            from sympy.polys.polyerrors import PolynomialError
            x = free.pop()
            x0 = _monotonic_sign(x)
            if x0 == _eps or x0 == -_eps:
                x0 = S.Zero
            if x0 is not None:
                d = self.diff(x)
                if d.is_number:
                    currentroots = []
                else:
                    try:
                        currentroots = real_roots(d)
                    except (PolynomialError, NotImplementedError):
                        currentroots = [r for r in roots(d, x) if r.is_extended_real]
                y = self.subs(x, x0)
                if x.is_nonnegative and all(r <= x0 for r in currentroots):
                    if y.is_nonnegative and d.is_positive:
                        if y:
                            return y if y.is_positive else Dummy('pos', positive=True)
                        else:
                            return Dummy('nneg', nonnegative=True)
                    if y.is_nonpositive and d.is_negative:
                        if y:
                            return y if y.is_negative else Dummy('neg', negative=True)
                        else:
                            return Dummy('npos', nonpositive=True)
                elif x.is_nonpositive and all(r >= x0 for r in currentroots):
                    if y.is_nonnegative and d.is_negative:
                        if y:
                            return Dummy('pos', positive=True)
                        else:
                            return Dummy('nneg', nonnegative=True)
                    if y.is_nonpositive and d.is_positive:
                        if y:
                            return Dummy('neg', negative=True)
                        else:
                            return Dummy('npos', nonpositive=True)
        else:
            n, d = self.as_numer_denom()
            den = None
            if n.is_number:
                den = _monotonic_sign(d)
            elif not d.is_number:
                if _monotonic_sign(n) is not None:
                    den = _monotonic_sign(d)
            if den is not None and (den.is_positive or den.is_negative):
                v = n*den
                if v.is_positive:
                    return Dummy('pos', positive=True)
                elif v.is_nonnegative:
                    return Dummy('nneg', nonnegative=True)
                elif v.is_negative:
                    return Dummy('neg', negative=True)
                elif v.is_nonpositive:
                    return Dummy('npos', nonpositive=True)
        return None

    # multivariate
    c, a = self.as_coeff_Add()
    v = None
    if not a.is_polynomial():
        # F/A or A/F where A is a number and F is a signed, rational monomial
        n, d = a.as_numer_denom()
        if not (n.is_number or d.is_number):
            return
        if (
                a.is_Mul or a.is_Pow) and \
                a.is_rational and \
                all(p.exp.is_Integer for p in a.atoms(Pow) if p.is_Pow) and \
                (a.is_positive or a.is_negative):
            v = S.One
            for ai in Mul.make_args(a):
                if ai.is_number:
                    v *= ai
                    continue
                reps = {}
                for x in ai.free_symbols:
                    reps[x] = _monotonic_sign(x)
                    if reps[x] is None:
                        return
                v *= ai.subs(reps)
    elif c:
        # signed linear expression
        if not any(p for p in a.atoms(Pow) if not p.is_number) and (a.is_nonpositive or a.is_nonnegative):
            free = list(a.free_symbols)
            p = {}
            for i in free:
                v = _monotonic_sign(i)
                if v is None:
                    return
                p[i] = v or (_eps if i.is_nonnegative else -_eps)
            v = a.xreplace(p)
    if v is not None:
        rv = v + c
        if v.is_nonnegative and rv.is_positive:
            return rv.subs(_eps, 0)
        if v.is_nonpositive and rv.is_negative:
            return rv.subs(_eps, 0)


def decompose_power(expr):
    """
    Decompose power into symbolic base and integer exponent.

    Explanation
    ===========

    This is strictly only valid if the exponent from which
    the integer is extracted is itself an integer or the
    base is positive. These conditions are assumed and not
    checked here.

    Examples
    ========

    >>> from sympy.core.exprtools import decompose_power
    >>> from sympy.abc import x, y

    >>> decompose_power(x)
    (x, 1)
    >>> decompose_power(x**2)
    (x, 2)
    >>> decompose_power(x**(2*y))
    (x**y, 2)
    >>> decompose_power(x**(2*y/3))
    (x**(y/3), 2)

    """
    base, exp = expr.as_base_exp()

    if exp.is_Number:
        if exp.is_Rational:
            if not exp.is_Integer:
                base = Pow(base, Rational(1, exp.q))

            exp = exp.p
        else:
            base, exp = expr, 1
    else:
        exp, tail = exp.as_coeff_Mul(rational=True)

        if exp is S.NegativeOne:
            base, exp = Pow(base, tail), -1
        elif exp is not S.One:
            tail = _keep_coeff(Rational(1, exp.q), tail)
            base, exp = Pow(base, tail), exp.p
        else:
            base, exp = expr, 1

    return base, exp


def decompose_power_rat(expr):
    """
    Decompose power into symbolic base and rational exponent.

    """
    base, exp = expr.as_base_exp()

    if exp.is_Number:
        if not exp.is_Rational:
            base, exp = expr, 1
    else:
        exp, tail = exp.as_coeff_Mul(rational=True)

        if exp is S.NegativeOne:
            base, exp = Pow(base, tail), -1
        elif exp is not S.One:
            tail = _keep_coeff(Rational(1, exp.q), tail)
            base, exp = Pow(base, tail), exp.p
        else:
            base, exp = expr, 1

    return base, exp


class Factors:
    """Efficient representation of ``f_1*f_2*...*f_n``."""

    __slots__ = ('factors', 'gens')

    def __init__(self, factors=None):  # Factors
        """Initialize Factors from dict or expr.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x
        >>> from sympy import I
        >>> e = 2*x**3
        >>> Factors(e)
        Factors({2: 1, x: 3})
        >>> Factors(e.as_powers_dict())
        Factors({2: 1, x: 3})
        >>> f = _
        >>> f.factors  # underlying dictionary
        {2: 1, x: 3}
        >>> f.gens  # base of each factor
        frozenset({2, x})
        >>> Factors(0)
        Factors({0: 1})
        >>> Factors(I)
        Factors({I: 1})

        Notes
        =====

        Although a dictionary can be passed, only minimal checking is
        performed: powers of -1 and I are made canonical.

        """
        if isinstance(factors, (SYMPY_INTS, float)):
            factors = S(factors)
        if isinstance(factors, Factors):
            factors = factors.factors.copy()
        elif factors is None or factors is S.One:
            factors = {}
        elif factors is S.Zero or factors == 0:
            factors = {S.Zero: S.One}
        elif isinstance(factors, Number):
            n = factors
            factors = {}
            if n < 0:
                factors[S.NegativeOne] = S.One
                n = -n
            if n is not S.One:
                if n.is_Float or n.is_Integer or n is S.Infinity:
                    factors[n] = S.One
                elif n.is_Rational:
                    # since we're processing Numbers, the denominator is
                    # stored with a negative exponent; all other factors
                    # are left .
                    if n.p != 1:
                        factors[Integer(n.p)] = S.One
                    factors[Integer(n.q)] = S.NegativeOne
                else:
                    raise ValueError('Expected Float|Rational|Integer, not %s' % n)
        elif isinstance(factors, Basic) and not factors.args:
            factors = {factors: S.One}
        elif isinstance(factors, Expr):
            c, nc = factors.args_cnc()
            i = c.count(I)
            for _ in range(i):
                c.remove(I)
            factors = dict(Mul._from_args(c).as_powers_dict())
            # Handle all rational Coefficients
            for f in list(factors.keys()):
                if isinstance(f, Rational) and not isinstance(f, Integer):
                    p, q = Integer(f.p), Integer(f.q)
                    factors[p] = (factors[p] if p in factors else S.Zero) + factors[f]
                    factors[q] = (factors[q] if q in factors else S.Zero) - factors[f]
                    factors.pop(f)
            if i:
                factors[I] = factors.get(I, S.Zero) + i
            if nc:
                factors[Mul(*nc, evaluate=False)] = S.One
        else:
            factors = factors.copy()  # /!\ should be dict-like

            # tidy up -/+1 and I exponents if Rational

            handle = []
            for k in factors:
                if k is I or k in (-1, 1):
                    handle.append(k)
            if handle:
                i1 = S.One
                for k in handle:
                    if not _isnumber(factors[k]):
                        continue
                    i1 *= k**factors.pop(k)
                if i1 is not S.One:
                    for a in i1.args if i1.is_Mul else [i1]:  # at worst, -1.0*I*(-1)**e
                        if a is S.NegativeOne:
                            factors[a] = S.One
                        elif a is I:
                            factors[I] = S.One
                        elif a.is_Pow:
                            factors[a.base] = factors.get(a.base, S.Zero) + a.exp
                        elif a == 1:
                            factors[a] = S.One
                        elif a == -1:
                            factors[-a] = S.One
                            factors[S.NegativeOne] = S.One
                        else:
                            raise ValueError('unexpected factor in i1: %s' % a)

        self.factors = factors
        keys = getattr(factors, 'keys', None)
        if keys is None:
            raise TypeError('expecting Expr or dictionary')
        self.gens = frozenset(keys())

    def __hash__(self):  # Factors
        keys = tuple(ordered(self.factors.keys()))
        values = [self.factors[k] for k in keys]
        return hash((keys, values))

    def __repr__(self):  # Factors
        return "Factors({%s})" % ', '.join(
            ['%s: %s' % (k, v) for k, v in ordered(self.factors.items())])

    @property
    def is_zero(self):  # Factors
        """
        >>> from sympy.core.exprtools import Factors
        >>> Factors(0).is_zero
        True
        """
        f = self.factors
        return len(f) == 1 and S.Zero in f

    @property
    def is_one(self):  # Factors
        """
        >>> from sympy.core.exprtools import Factors
        >>> Factors(1).is_one
        True
        """
        return not self.factors

    def as_expr(self):  # Factors
        """Return the underlying expression.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x, y
        >>> Factors((x*y**2).as_powers_dict()).as_expr()
        x*y**2

        """

        args = []
        for factor, exp in self.factors.items():
            if exp != 1:
                if isinstance(exp, Integer):
                    b, e = factor.as_base_exp()
                    e = _keep_coeff(exp, e)
                    args.append(b**e)
                else:
                    args.append(factor**exp)
            else:
                args.append(factor)
        return Mul(*args)

    def mul(self, other):  # Factors
        """Return Factors of ``self * other``.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x, y, z
        >>> a = Factors((x*y**2).as_powers_dict())
        >>> b = Factors((x*y/z).as_powers_dict())
        >>> a.mul(b)
        Factors({x: 2, y: 3, z: -1})
        >>> a*b
        Factors({x: 2, y: 3, z: -1})
        """
        if not isinstance(other, Factors):
            other = Factors(other)
        if any(f.is_zero for f in (self, other)):
            return Factors(S.Zero)
        factors = dict(self.factors)

        for factor, exp in other.factors.items():
            if factor in factors:
                exp = factors[factor] + exp

                if not exp:
                    del factors[factor]
                    continue

            factors[factor] = exp

        return Factors(factors)

    def normal(self, other):
        """Return ``self`` and ``other`` with ``gcd`` removed from each.
        The only differences between this and method ``div`` is that this
        is 1) optimized for the case when there are few factors in common and
        2) this does not raise an error if ``other`` is zero.

        See Also
        ========
        div

        """
        if not isinstance(other, Factors):
            other = Factors(other)
            if other.is_zero:
                return (Factors(), Factors(S.Zero))
            if self.is_zero:
                return (Factors(S.Zero), Factors())

        self_factors = dict(self.factors)
        other_factors = dict(other.factors)

        for factor, self_exp in self.factors.items():
            try:
                other_exp = other.factors[factor]
            except KeyError:
                continue

            exp = self_exp - other_exp

            if not exp:
                del self_factors[factor]
                del other_factors[factor]
            elif _isnumber(exp):
                if exp > 0:
                    self_factors[factor] = exp
                    del other_factors[factor]
                else:
                    del self_factors[factor]
                    other_factors[factor] = -exp
            else:
                r = self_exp.extract_additively(other_exp)
                if r is not None:
                    if r:
                        self_factors[factor] = r
                        del other_factors[factor]
                    else:  # should be handled already
                        del self_factors[factor]
                        del other_factors[factor]
                else:
                    sc, sa = self_exp.as_coeff_Add()
                    if sc:
                        oc, oa = other_exp.as_coeff_Add()
                        diff = sc - oc
                        if diff > 0:
                            self_factors[factor] -= oc
                            other_exp = oa
                        elif diff < 0:
                            self_factors[factor] -= sc
                            other_factors[factor] -= sc
                            other_exp = oa - diff
                        else:
                            self_factors[factor] = sa
                            other_exp = oa
                    if other_exp:
                        other_factors[factor] = other_exp
                    else:
                        del other_factors[factor]

        return Factors(self_factors), Factors(other_factors)

    def div(self, other):  # Factors
        """Return ``self`` and ``other`` with ``gcd`` removed from each.
        This is optimized for the case when there are many factors in common.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x, y, z
        >>> from sympy import S

        >>> a = Factors((x*y**2).as_powers_dict())
        >>> a.div(a)
        (Factors({}), Factors({}))
        >>> a.div(x*z)
        (Factors({y: 2}), Factors({z: 1}))

        The ``/`` operator only gives ``quo``:

        >>> a/x
        Factors({y: 2})

        Factors treats its factors as though they are all in the numerator, so
        if you violate this assumption the results will be correct but will
        not strictly correspond to the numerator and denominator of the ratio:

        >>> a.div(x/z)
        (Factors({y: 2}), Factors({z: -1}))

        Factors is also naive about bases: it does not attempt any denesting
        of Rational-base terms, for example the following does not become
        2**(2*x)/2.

        >>> Factors(2**(2*x + 2)).div(S(8))
        (Factors({2: 2*x + 2}), Factors({8: 1}))

        factor_terms can clean up such Rational-bases powers:

        >>> from sympy.core.exprtools import factor_terms
        >>> n, d = Factors(2**(2*x + 2)).div(S(8))
        >>> n.as_expr()/d.as_expr()
        2**(2*x + 2)/8
        >>> factor_terms(_)
        2**(2*x)/2

        """
        quo, rem = dict(self.factors), {}

        if not isinstance(other, Factors):
            other = Factors(other)
            if other.is_zero:
                raise ZeroDivisionError
            if self.is_zero:
                return (Factors(S.Zero), Factors())

        for factor, exp in other.factors.items():
            if factor in quo:
                d = quo[factor] - exp
                if _isnumber(d):
                    if d <= 0:
                        del quo[factor]

                    if d >= 0:
                        if d:
                            quo[factor] = d

                        continue

                    exp = -d

                else:
                    r = quo[factor].extract_additively(exp)
                    if r is not None:
                        if r:
                            quo[factor] = r
                        else:  # should be handled already
                            del quo[factor]
                    else:
                        other_exp = exp
                        sc, sa = quo[factor].as_coeff_Add()
                        if sc:
                            oc, oa = other_exp.as_coeff_Add()
                            diff = sc - oc
                            if diff > 0:
                                quo[factor] -= oc
                                other_exp = oa
                            elif diff < 0:
                                quo[factor] -= sc
                                other_exp = oa - diff
                            else:
                                quo[factor] = sa
                                other_exp = oa
                        if other_exp:
                            rem[factor] = other_exp
                        else:
                            assert factor not in rem
                    continue

            rem[factor] = exp

        return Factors(quo), Factors(rem)

    def quo(self, other):  # Factors
        """Return numerator Factor of ``self / other``.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x, y, z
        >>> a = Factors((x*y**2).as_powers_dict())
        >>> b = Factors((x*y/z).as_powers_dict())
        >>> a.quo(b)  # same as a/b
        Factors({y: 1})
        """
        return self.div(other)[0]

    def rem(self, other):  # Factors
        """Return denominator Factors of ``self / other``.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x, y, z
        >>> a = Factors((x*y**2).as_powers_dict())
        >>> b = Factors((x*y/z).as_powers_dict())
        >>> a.rem(b)
        Factors({z: -1})
        >>> a.rem(a)
        Factors({})
        """
        return self.div(other)[1]

    def pow(self, other):  # Factors
        """Return self raised to a non-negative integer power.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x, y
        >>> a = Factors((x*y**2).as_powers_dict())
        >>> a**2
        Factors({x: 2, y: 4})

        """
        if isinstance(other, Factors):
            other = other.as_expr()
            if other.is_Integer:
                other = int(other)
        if isinstance(other, SYMPY_INTS) and other >= 0:
            factors = {}

            if other:
                for factor, exp in self.factors.items():
                    factors[factor] = exp*other

            return Factors(factors)
        else:
            raise ValueError("expected non-negative integer, got %s" % other)

    def gcd(self, other):  # Factors
        """Return Factors of ``gcd(self, other)``. The keys are
        the intersection of factors with the minimum exponent for
        each factor.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x, y, z
        >>> a = Factors((x*y**2).as_powers_dict())
        >>> b = Factors((x*y/z).as_powers_dict())
        >>> a.gcd(b)
        Factors({x: 1, y: 1})
        """
        if not isinstance(other, Factors):
            other = Factors(other)
            if other.is_zero:
                return Factors(self.factors)

        factors = {}

        for factor, exp in self.factors.items():
            factor, exp = sympify(factor), sympify(exp)
            if factor in other.factors:
                lt = (exp - other.factors[factor]).is_negative
                if lt == True:
                    factors[factor] = exp
                elif lt == False:
                    factors[factor] = other.factors[factor]

        return Factors(factors)

    def lcm(self, other):  # Factors
        """Return Factors of ``lcm(self, other)`` which are
        the union of factors with the maximum exponent for
        each factor.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x, y, z
        >>> a = Factors((x*y**2).as_powers_dict())
        >>> b = Factors((x*y/z).as_powers_dict())
        >>> a.lcm(b)
        Factors({x: 1, y: 2, z: -1})
        """
        if not isinstance(other, Factors):
            other = Factors(other)
            if any(f.is_zero for f in (self, other)):
                return Factors(S.Zero)

        factors = dict(self.factors)

        for factor, exp in other.factors.items():
            if factor in factors:
                exp = max(exp, factors[factor])

            factors[factor] = exp

        return Factors(factors)

    def __mul__(self, other):  # Factors
        return self.mul(other)

    def __divmod__(self, other):  # Factors
        return self.div(other)

    def __truediv__(self, other):  # Factors
        return self.quo(other)

    def __mod__(self, other):  # Factors
        return self.rem(other)

    def __pow__(self, other):  # Factors
        return self.pow(other)

    def __eq__(self, other):  # Factors
        if not isinstance(other, Factors):
            other = Factors(other)
        return self.factors == other.factors

    def __ne__(self, other):  # Factors
        return not self == other


class Term:
    """Efficient representation of ``coeff*(numer/denom)``. """

    __slots__ = ('coeff', 'numer', 'denom')

    def __init__(self, term, numer=None, denom=None):  # Term
        if numer is None and denom is None:
            if not term.is_commutative:
                raise NonCommutativeExpression(
                    'commutative expression expected')

            coeff, factors = term.as_coeff_mul()
            numer, denom = defaultdict(int), defaultdict(int)

            for factor in factors:
                base, exp = decompose_power(factor)

                if base.is_Add:
                    cont, base = base.primitive()
                    coeff *= cont**exp

                if exp > 0:
                    numer[base] += exp
                else:
                    denom[base] += -exp

            numer = Factors(numer)
            denom = Factors(denom)
        else:
            coeff = term

            if numer is None:
                numer = Factors()

            if denom is None:
                denom = Factors()

        self.coeff = coeff
        self.numer = numer
        self.denom = denom

    def __hash__(self):  # Term
        return hash((self.coeff, self.numer, self.denom))

    def __repr__(self):  # Term
        return "Term(%s, %s, %s)" % (self.coeff, self.numer, self.denom)

    def as_expr(self):  # Term
        return self.coeff*(self.numer.as_expr()/self.denom.as_expr())

    def mul(self, other):  # Term
        coeff = self.coeff*other.coeff
        numer = self.numer.mul(other.numer)
        denom = self.denom.mul(other.denom)

        numer, denom = numer.normal(denom)

        return Term(coeff, numer, denom)

    def inv(self):  # Term
        return Term(1/self.coeff, self.denom, self.numer)

    def quo(self, other):  # Term
        return self.mul(other.inv())

    def pow(self, other):  # Term
        if other < 0:
            return self.inv().pow(-other)
        else:
            return Term(self.coeff ** other,
                        self.numer.pow(other),
                        self.denom.pow(other))

    def gcd(self, other):  # Term
        return Term(self.coeff.gcd(other.coeff),
                    self.numer.gcd(other.numer),
                    self.denom.gcd(other.denom))

    def lcm(self, other):  # Term
        return Term(self.coeff.lcm(other.coeff),
                    self.numer.lcm(other.numer),
                    self.denom.lcm(other.denom))

    def __mul__(self, other):  # Term
        if isinstance(other, Term):
            return self.mul(other)
        else:
            return NotImplemented

    def __truediv__(self, other):  # Term
        if isinstance(other, Term):
            return self.quo(other)
        else:
            return NotImplemented

    def __pow__(self, other):  # Term
        if isinstance(other, SYMPY_INTS):
            return self.pow(other)
        else:
            return NotImplemented

    def __eq__(self, other):  # Term
        return (self.coeff == other.coeff and
                self.numer == other.numer and
                self.denom == other.denom)

    def __ne__(self, other):  # Term
        return not self == other


def _gcd_terms(terms, isprimitive=False, fraction=True):
    """Helper function for :func:`gcd_terms`.

    Parameters
    ==========

    isprimitive : boolean, optional
        If ``isprimitive`` is True then the call to primitive
        for an Add will be skipped. This is useful when the
        content has already been extrated.

    fraction : boolean, optional
        If ``fraction`` is True then the expression will appear over a common
        denominator, the lcm of all term denominators.
    """

    if isinstance(terms, Basic) and not isinstance(terms, Tuple):
        terms = Add.make_args(terms)

    terms = list(map(Term, [t for t in terms if t]))

    # there is some simplification that may happen if we leave this
    # here rather than duplicate it before the mapping of Term onto
    # the terms
    if len(terms) == 0:
        return S.Zero, S.Zero, S.One

    if len(terms) == 1:
        cont = terms[0].coeff
        numer = terms[0].numer.as_expr()
        denom = terms[0].denom.as_expr()

    else:
        cont = terms[0]
        for term in terms[1:]:
            cont = cont.gcd(term)

        for i, term in enumerate(terms):
            terms[i] = term.quo(cont)

        if fraction:
            denom = terms[0].denom

            for term in terms[1:]:
                denom = denom.lcm(term.denom)

            numers = []
            for term in terms:
                numer = term.numer.mul(denom.quo(term.denom))
                numers.append(term.coeff*numer.as_expr())
        else:
            numers = [t.as_expr() for t in terms]
            denom = Term(S.One).numer

        cont = cont.as_expr()
        numer = Add(*numers)
        denom = denom.as_expr()

    if not isprimitive and numer.is_Add:
        _cont, numer = numer.primitive()
        cont *= _cont

    return cont, numer, denom


def gcd_terms(terms, isprimitive=False, clear=True, fraction=True):
    """Compute the GCD of ``terms`` and put them together.

    Parameters
    ==========

    terms : Expr
        Can be an expression or a non-Basic sequence of expressions
        which will be handled as though they are terms from a sum.

    isprimitive : bool, optional
        If ``isprimitive`` is True the _gcd_terms will not run the primitive
        method on the terms.

    clear : bool, optional
        It controls the removal of integers from the denominator of an Add
        expression. When True (default), all numerical denominator will be cleared;
        when False the denominators will be cleared only if all terms had numerical
        denominators other than 1.

    fraction : bool, optional
        When True (default), will put the expression over a common
        denominator.

    Examples
    ========

    >>> from sympy.core import gcd_terms
    >>> from sympy.abc import x, y

    >>> gcd_terms((x + 1)**2*y + (x + 1)*y**2)
    y*(x + 1)*(x + y + 1)
    >>> gcd_terms(x/2 + 1)
    (x + 2)/2
    >>> gcd_terms(x/2 + 1, clear=False)
    x/2 + 1
    >>> gcd_terms(x/2 + y/2, clear=False)
    (x + y)/2
    >>> gcd_terms(x/2 + 1/x)
    (x**2 + 2)/(2*x)
    >>> gcd_terms(x/2 + 1/x, fraction=False)
    (x + 2/x)/2
    >>> gcd_terms(x/2 + 1/x, fraction=False, clear=False)
    x/2 + 1/x

    >>> gcd_terms(x/2/y + 1/x/y)
    (x**2 + 2)/(2*x*y)
    >>> gcd_terms(x/2/y + 1/x/y, clear=False)
    (x**2/2 + 1)/(x*y)
    >>> gcd_terms(x/2/y + 1/x/y, clear=False, fraction=False)
    (x/2 + 1/x)/y

    The ``clear`` flag was ignored in this case because the returned
    expression was a rational expression, not a simple sum.

    See Also
    ========

    factor_terms, sympy.polys.polytools.terms_gcd

    """
    def mask(terms):
        """replace nc portions of each term with a unique Dummy symbols
        and return the replacements to restore them"""
        args = [(a, []) if a.is_commutative else a.args_cnc() for a in terms]
        reps = []
        for i, (c, nc) in enumerate(args):
            if nc:
                nc = Mul(*nc)
                d = Dummy()
                reps.append((d, nc))
                c.append(d)
                args[i] = Mul(*c)
            else:
                args[i] = c
        return args, dict(reps)

    isadd = isinstance(terms, Add)
    addlike = isadd or not isinstance(terms, Basic) and \
        is_sequence(terms, include=set) and \
        not isinstance(terms, Dict)

    if addlike:
        if isadd:  # i.e. an Add
            terms = list(terms.args)
        else:
            terms = sympify(terms)
        terms, reps = mask(terms)
        cont, numer, denom = _gcd_terms(terms, isprimitive, fraction)
        numer = numer.xreplace(reps)
        coeff, factors = cont.as_coeff_Mul()
        if not clear:
            c, _coeff = coeff.as_coeff_Mul()
            if not c.is_Integer and not clear and numer.is_Add:
                n, d = c.as_numer_denom()
                _numer = numer/d
                if any(a.as_coeff_Mul()[0].is_Integer
                        for a in _numer.args):
                    numer = _numer
                    coeff = n*_coeff
        return _keep_coeff(coeff, factors*numer/denom, clear=clear)

    if not isinstance(terms, Basic):
        return terms

    if terms.is_Atom:
        return terms

    if terms.is_Mul:
        c, args = terms.as_coeff_mul()
        return _keep_coeff(c, Mul(*[gcd_terms(i, isprimitive, clear, fraction)
            for i in args]), clear=clear)

    def handle(a):
        # don't treat internal args like terms of an Add
        if not isinstance(a, Expr):
            if isinstance(a, Basic):
                if not a.args:
                    return a
                return a.func(*[handle(i) for i in a.args])
            return type(a)([handle(i) for i in a])
        return gcd_terms(a, isprimitive, clear, fraction)

    if isinstance(terms, Dict):
        return Dict(*[(k, handle(v)) for k, v in terms.args])
    return terms.func(*[handle(i) for i in terms.args])


def _factor_sum_int(expr, **kwargs):
    """Return Sum or Integral object with factors that are not
    in the wrt variables removed. In cases where there are additive
    terms in the function of the object that are independent, the
    object will be separated into two objects.

    Examples
    ========

    >>> from sympy import Sum, factor_terms
    >>> from sympy.abc import x, y
    >>> factor_terms(Sum(x + y, (x, 1, 3)))
    y*Sum(1, (x, 1, 3)) + Sum(x, (x, 1, 3))
    >>> factor_terms(Sum(x*y, (x, 1, 3)))
    y*Sum(x, (x, 1, 3))

    Notes
    =====

    If a function in the summand or integrand is replaced
    with a symbol, then this simplification should not be
    done or else an incorrect result will be obtained when
    the symbol is replaced with an expression that depends
    on the variables of summation/integration:

    >>> eq = Sum(y, (x, 1, 3))
    >>> factor_terms(eq).subs(y, x).doit()
    3*x
    >>> eq.subs(y, x).doit()
    6
    """
    result = expr.function
    if result == 0:
        return S.Zero
    limits = expr.limits

    # get the wrt variables
    wrt = {i.args[0] for i in limits}

    # factor out any common terms that are independent of wrt
    f = factor_terms(result, **kwargs)
    i, d = f.as_independent(*wrt)
    if isinstance(f, Add):
        return i * expr.func(1, *limits) + expr.func(d, *limits)
    else:
        return i * expr.func(d, *limits)


def factor_terms(expr, radical=False, clear=False, fraction=False, sign=True):
    """Remove common factors from terms in all arguments without
    changing the underlying structure of the expr. No expansion or
    simplification (and no processing of non-commutatives) is performed.

    Parameters
    ==========

    radical: bool, optional
        If radical=True then a radical common to all terms will be factored
        out of any Add sub-expressions of the expr.

    clear : bool, optional
        If clear=False (default) then coefficients will not be separated
        from a single Add if they can be distributed to leave one or more
        terms with integer coefficients.

    fraction : bool, optional
        If fraction=True (default is False) then a common denominator will be
        constructed for the expression.

    sign : bool, optional
        If sign=True (default) then even if the only factor in common is a -1,
        it will be factored out of the expression.

    Examples
    ========

    >>> from sympy import factor_terms, Symbol
    >>> from sympy.abc import x, y
    >>> factor_terms(x + x*(2 + 4*y)**3)
    x*(8*(2*y + 1)**3 + 1)
    >>> A = Symbol('A', commutative=False)
    >>> factor_terms(x*A + x*A + x*y*A)
    x*(y*A + 2*A)

    When ``clear`` is False, a rational will only be factored out of an
    Add expression if all terms of the Add have coefficients that are
    fractions:

    >>> factor_terms(x/2 + 1, clear=False)
    x/2 + 1
    >>> factor_terms(x/2 + 1, clear=True)
    (x + 2)/2

    If a -1 is all that can be factored out, to *not* factor it out, the
    flag ``sign`` must be False:

    >>> factor_terms(-x - y)
    -(x + y)
    >>> factor_terms(-x - y, sign=False)
    -x - y
    >>> factor_terms(-2*x - 2*y, sign=False)
    -2*(x + y)

    See Also
    ========

    gcd_terms, sympy.polys.polytools.terms_gcd

    """
    def do(expr):
        from sympy.concrete.summations import Sum
        from sympy.integrals.integrals import Integral
        is_iterable = iterable(expr)

        if not isinstance(expr, Basic) or expr.is_Atom:
            if is_iterable:
                return type(expr)([do(i) for i in expr])
            return expr

        if expr.is_Pow or expr.is_Function or \
                is_iterable or not hasattr(expr, 'args_cnc'):
            args = expr.args
            newargs = tuple([do(i) for i in args])
            if newargs == args:
                return expr
            return expr.func(*newargs)

        if isinstance(expr, (Sum, Integral)):
            return _factor_sum_int(expr,
                radical=radical, clear=clear,
                fraction=fraction, sign=sign)

        cont, p = expr.as_content_primitive(radical=radical, clear=clear)
        if p.is_Add:
            list_args = [do(a) for a in Add.make_args(p)]
            # get a common negative (if there) which gcd_terms does not remove
            if all(a.as_coeff_Mul()[0].extract_multiplicatively(-1) is not None
                   for a in list_args):
                cont = -cont
                list_args = [-a for a in list_args]
            # watch out for exp(-(x+2)) which gcd_terms will change to exp(-x-2)
            special = {}
            for i, a in enumerate(list_args):
                b, e = a.as_base_exp()
                if e.is_Mul and e != Mul(*e.args):
                    list_args[i] = Dummy()
                    special[list_args[i]] = a
            # rebuild p not worrying about the order which gcd_terms will fix
            p = Add._from_args(list_args)
            p = gcd_terms(p,
                isprimitive=True,
                clear=clear,
                fraction=fraction).xreplace(special)
        elif p.args:
            p = p.func(
                *[do(a) for a in p.args])
        rv = _keep_coeff(cont, p, clear=clear, sign=sign)
        return rv
    expr = sympify(expr)
    return do(expr)


def _mask_nc(eq, name=None):
    """
    Return ``eq`` with non-commutative objects replaced with Dummy
    symbols. A dictionary that can be used to restore the original
    values is returned: if it is None, the expression is noncommutative
    and cannot be made commutative. The third value returned is a list
    of any non-commutative symbols that appear in the returned equation.

    Explanation
    ===========

    All non-commutative objects other than Symbols are replaced with
    a non-commutative Symbol. Identical objects will be identified
    by identical symbols.

    If there is only 1 non-commutative object in an expression it will
    be replaced with a commutative symbol. Otherwise, the non-commutative
    entities are retained and the calling routine should handle
    replacements in this case since some care must be taken to keep
    track of the ordering of symbols when they occur within Muls.

    Parameters
    ==========

    name : str
        ``name``, if given, is the name that will be used with numbered Dummy
        variables that will replace the non-commutative objects and is mainly
        used for doctesting purposes.

    Examples
    ========

    >>> from sympy.physics.secondquant import Commutator, NO, F, Fd
    >>> from sympy import symbols
    >>> from sympy.core.exprtools import _mask_nc
    >>> from sympy.abc import x, y
    >>> A, B, C = symbols('A,B,C', commutative=False)

    One nc-symbol:

    >>> _mask_nc(A**2 - x**2, 'd')
    (_d0**2 - x**2, {_d0: A}, [])

    Multiple nc-symbols:

    >>> _mask_nc(A**2 - B**2, 'd')
    (A**2 - B**2, {}, [A, B])

    An nc-object with nc-symbols but no others outside of it:

    >>> _mask_nc(1 + x*Commutator(A, B), 'd')
    (_d0*x + 1, {_d0: Commutator(A, B)}, [])
    >>> _mask_nc(NO(Fd(x)*F(y)), 'd')
    (_d0, {_d0: NO(CreateFermion(x)*AnnihilateFermion(y))}, [])

    Multiple nc-objects:

    >>> eq = x*Commutator(A, B) + x*Commutator(A, C)*Commutator(A, B)
    >>> _mask_nc(eq, 'd')
    (x*_d0 + x*_d1*_d0, {_d0: Commutator(A, B), _d1: Commutator(A, C)}, [_d0, _d1])

    Multiple nc-objects and nc-symbols:

    >>> eq = A*Commutator(A, B) + B*Commutator(A, C)
    >>> _mask_nc(eq, 'd')
    (A*_d0 + B*_d1, {_d0: Commutator(A, B), _d1: Commutator(A, C)}, [_d0, _d1, A, B])

    """
    name = name or 'mask'
    # Make Dummy() append sequential numbers to the name

    def numbered_names():
        i = 0
        while True:
            yield name + str(i)
            i += 1

    names = numbered_names()

    def Dummy(*args, **kwargs):
        from sympy import Dummy
        return Dummy(next(names), *args, **kwargs)

    expr = eq
    if expr.is_commutative:
        return eq, {}, []

    # identify nc-objects; symbols and other
    rep = []
    nc_obj = set()
    nc_syms = set()
    pot = preorder_traversal(expr, keys=default_sort_key)
    for i, a in enumerate(pot):
        if any(a == r[0] for r in rep):
            pot.skip()
        elif not a.is_commutative:
            if a.is_symbol:
                nc_syms.add(a)
                pot.skip()
            elif not (a.is_Add or a.is_Mul or a.is_Pow):
                nc_obj.add(a)
                pot.skip()

    # If there is only one nc symbol or object, it can be factored regularly
    # but polys is going to complain, so replace it with a Dummy.
    if len(nc_obj) == 1 and not nc_syms:
        rep.append((nc_obj.pop(), Dummy()))
    elif len(nc_syms) == 1 and not nc_obj:
        rep.append((nc_syms.pop(), Dummy()))

    # Any remaining nc-objects will be replaced with an nc-Dummy and
    # identified as an nc-Symbol to watch out for
    nc_obj = sorted(nc_obj, key=default_sort_key)
    for n in nc_obj:
        nc = Dummy(commutative=False)
        rep.append((n, nc))
        nc_syms.add(nc)
    expr = expr.subs(rep)

    nc_syms = list(nc_syms)
    nc_syms.sort(key=default_sort_key)
    return expr, {v: k for k, v in rep}, nc_syms


def factor_nc(expr):
    """Return the factored form of ``expr`` while handling non-commutative
    expressions.

    Examples
    ========

    >>> from sympy.core.exprtools import factor_nc
    >>> from sympy import Symbol
    >>> from sympy.abc import x
    >>> A = Symbol('A', commutative=False)
    >>> B = Symbol('B', commutative=False)
    >>> factor_nc((x**2 + 2*A*x + A**2).expand())
    (x + A)**2
    >>> factor_nc(((x + A)*(x + B)).expand())
    (x + A)*(x + B)
    """
    from sympy.simplify.simplify import powsimp
    from sympy.polys import gcd, factor

    def _pemexpand(expr):
        "Expand with the minimal set of hints necessary to check the result."
        return expr.expand(deep=True, mul=True, power_exp=True,
            power_base=False, basic=False, multinomial=True, log=False)

    expr = sympify(expr)
    if not isinstance(expr, Expr) or not expr.args:
        return expr
    if not expr.is_Add:
        return expr.func(*[factor_nc(a) for a in expr.args])

    expr, rep, nc_symbols = _mask_nc(expr)
    if rep:
        return factor(expr).subs(rep)
    else:
        args = [a.args_cnc() for a in Add.make_args(expr)]
        c = g = l = r = S.One
        hit = False
        # find any commutative gcd term
        for i, a in enumerate(args):
            if i == 0:
                c = Mul._from_args(a[0])
            elif a[0]:
                c = gcd(c, Mul._from_args(a[0]))
            else:
                c = S.One
        if c is not S.One:
            hit = True
            c, g = c.as_coeff_Mul()
            if g is not S.One:
                for i, (cc, _) in enumerate(args):
                    cc = list(Mul.make_args(Mul._from_args(list(cc))/g))
                    args[i][0] = cc
            for i, (cc, _) in enumerate(args):
                cc[0] = cc[0]/c
                args[i][0] = cc
        # find any noncommutative common prefix
        for i, a in enumerate(args):
            if i == 0:
                n = a[1][:]
            else:
                n = common_prefix(n, a[1])
            if not n:
                # is there a power that can be extracted?
                if not args[0][1]:
                    break
                b, e = args[0][1][0].as_base_exp()
                ok = False
                if e.is_Integer:
                    for t in args:
                        if not t[1]:
                            break
                        bt, et = t[1][0].as_base_exp()
                        if et.is_Integer and bt == b:
                            e = min(e, et)
                        else:
                            break
                    else:
                        ok = hit = True
                        l = b**e
                        il = b**-e
                        for _ in args:
                            _[1][0] = il*_[1][0]
                        break
                if not ok:
                    break
        else:
            hit = True
            lenn = len(n)
            l = Mul(*n)
            for _ in args:
                _[1] = _[1][lenn:]
        # find any noncommutative common suffix
        for i, a in enumerate(args):
            if i == 0:
                n = a[1][:]
            else:
                n = common_suffix(n, a[1])
            if not n:
                # is there a power that can be extracted?
                if not args[0][1]:
                    break
                b, e = args[0][1][-1].as_base_exp()
                ok = False
                if e.is_Integer:
                    for t in args:
                        if not t[1]:
                            break
                        bt, et = t[1][-1].as_base_exp()
                        if et.is_Integer and bt == b:
                            e = min(e, et)
                        else:
                            break
                    else:
                        ok = hit = True
                        r = b**e
                        il = b**-e
                        for _ in args:
                            _[1][-1] = _[1][-1]*il
                        break
                if not ok:
                    break
        else:
            hit = True
            lenn = len(n)
            r = Mul(*n)
            for _ in args:
                _[1] = _[1][:len(_[1]) - lenn]
        if hit:
            mid = Add(*[Mul(*cc)*Mul(*nc) for cc, nc in args])
        else:
            mid = expr

        # sort the symbols so the Dummys would appear in the same
        # order as the original symbols, otherwise you may introduce
        # a factor of -1, e.g. A**2 - B**2) -- {A:y, B:x} --> y**2 - x**2
        # and the former factors into two terms, (A - B)*(A + B) while the
        # latter factors into 3 terms, (-1)*(x - y)*(x + y)
        rep1 = [(n, Dummy()) for n in sorted(nc_symbols, key=default_sort_key)]
        unrep1 = [(v, k) for k, v in rep1]
        unrep1.reverse()
        new_mid, r2, _ = _mask_nc(mid.subs(rep1))
        new_mid = powsimp(factor(new_mid))

        new_mid = new_mid.subs(r2).subs(unrep1)

        if new_mid.is_Pow:
            return _keep_coeff(c, g*l*new_mid*r)

        if new_mid.is_Mul:
            # XXX TODO there should be a way to inspect what order the terms
            # must be in and just select the plausible ordering without
            # checking permutations
            cfac = []
            ncfac = []
            for f in new_mid.args:
                if f.is_commutative:
                    cfac.append(f)
                else:
                    b, e = f.as_base_exp()
                    if e.is_Integer:
                        ncfac.extend([b]*e)
                    else:
                        ncfac.append(f)
            pre_mid = g*Mul(*cfac)*l
            target = _pemexpand(expr/c)
            for s in variations(ncfac, len(ncfac)):
                ok = pre_mid*Mul(*s)*r
                if _pemexpand(ok) == target:
                    return _keep_coeff(c, ok)

        # mid was an Add that didn't factor successfully
        return _keep_coeff(c, g*l*mid*r)
