from sympy import (S, Dummy, Lambda, symbols, Interval, Intersection, Set,
                   EmptySet, FiniteSet, Union, ComplexRegion)
from sympy.multipledispatch import dispatch
from sympy.sets.conditionset import ConditionSet
from sympy.sets.fancysets import (Integers, Naturals, Reals, Range,
    ImageSet, Rationals)
from sympy.sets.sets import UniversalSet, imageset, ProductSet


@dispatch(ConditionSet, ConditionSet)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return None

@dispatch(ConditionSet, Set)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return ConditionSet(a.sym, a.condition, Intersection(a.base_set, b))

@dispatch(Naturals, Integers)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return a

@dispatch(Naturals, Naturals)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return a if a is S.Naturals else b

@dispatch(Interval, Naturals)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return intersection_sets(b, a)

@dispatch(ComplexRegion, Set)  # type: ignore # noqa:F811
def intersection_sets(self, other): # noqa:F811
    if other.is_ComplexRegion:
        # self in rectangular form
        if (not self.polar) and (not other.polar):
            return ComplexRegion(Intersection(self.sets, other.sets))

        # self in polar form
        elif self.polar and other.polar:
            r1, theta1 = self.a_interval, self.b_interval
            r2, theta2 = other.a_interval, other.b_interval
            new_r_interval = Intersection(r1, r2)
            new_theta_interval = Intersection(theta1, theta2)

            # 0 and 2*Pi means the same
            if ((2*S.Pi in theta1 and S.Zero in theta2) or
               (2*S.Pi in theta2 and S.Zero in theta1)):
                new_theta_interval = Union(new_theta_interval,
                                           FiniteSet(0))
            return ComplexRegion(new_r_interval*new_theta_interval,
                                polar=True)


    if other.is_subset(S.Reals):
        new_interval = []
        x = symbols("x", cls=Dummy, real=True)

        # self in rectangular form
        if not self.polar:
            for element in self.psets:
                if S.Zero in element.args[1]:
                    new_interval.append(element.args[0])
            new_interval = Union(*new_interval)
            return Intersection(new_interval, other)

        # self in polar form
        elif self.polar:
            for element in self.psets:
                if S.Zero in element.args[1]:
                    new_interval.append(element.args[0])
                if S.Pi in element.args[1]:
                    new_interval.append(ImageSet(Lambda(x, -x), element.args[0]))
                if S.Zero in element.args[0]:
                    new_interval.append(FiniteSet(0))
            new_interval = Union(*new_interval)
            return Intersection(new_interval, other)

@dispatch(Integers, Reals)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return a

@dispatch(Range, Interval)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    from sympy.functions.elementary.integers import floor, ceiling
    if not all(i.is_number for i in b.args[:2]):
        return

    # In case of null Range, return an EmptySet.
    if a.size == 0:
        return S.EmptySet

    # trim down to self's size, and represent
    # as a Range with step 1.
    start = ceiling(max(b.inf, a.inf))
    if start not in b:
        start += 1
    end = floor(min(b.sup, a.sup))
    if end not in b:
        end -= 1
    return intersection_sets(a, Range(start, end + 1))

@dispatch(Range, Naturals)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return intersection_sets(a, Interval(b.inf, S.Infinity))

@dispatch(Range, Range)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    from sympy.solvers.diophantine.diophantine import diop_linear
    from sympy.core.numbers import ilcm
    from sympy import sign

    # non-overlap quick exits
    if not b:
        return S.EmptySet
    if not a:
        return S.EmptySet
    if b.sup < a.inf:
        return S.EmptySet
    if b.inf > a.sup:
        return S.EmptySet

    # work with finite end at the start
    r1 = a
    if r1.start.is_infinite:
        r1 = r1.reversed
    r2 = b
    if r2.start.is_infinite:
        r2 = r2.reversed

    # If both ends are infinite then it means that one Range is just the set
    # of all integers (the step must be 1).
    if r1.start.is_infinite:
        return b
    if r2.start.is_infinite:
        return a

    # this equation represents the values of the Range;
    # it's a linear equation
    eq = lambda r, i: r.start + i*r.step

    # we want to know when the two equations might
    # have integer solutions so we use the diophantine
    # solver
    va, vb = diop_linear(eq(r1, Dummy('a')) - eq(r2, Dummy('b')))

    # check for no solution
    no_solution = va is None and vb is None
    if no_solution:
        return S.EmptySet

    # there is a solution
    # -------------------

    # find the coincident point, c
    a0 = va.as_coeff_Add()[0]
    c = eq(r1, a0)

    # find the first point, if possible, in each range
    # since c may not be that point
    def _first_finite_point(r1, c):
        if c == r1.start:
            return c
        # st is the signed step we need to take to
        # get from c to r1.start
        st = sign(r1.start - c)*step
        # use Range to calculate the first point:
        # we want to get as close as possible to
        # r1.start; the Range will not be null since
        # it will at least contain c
        s1 = Range(c, r1.start + st, st)[-1]
        if s1 == r1.start:
            pass
        else:
            # if we didn't hit r1.start then, if the
            # sign of st didn't match the sign of r1.step
            # we are off by one and s1 is not in r1
            if sign(r1.step) != sign(st):
                s1 -= st
        if s1 not in r1:
            return
        return s1

    # calculate the step size of the new Range
    step = abs(ilcm(r1.step, r2.step))
    s1 = _first_finite_point(r1, c)
    if s1 is None:
        return S.EmptySet
    s2 = _first_finite_point(r2, c)
    if s2 is None:
        return S.EmptySet

    # replace the corresponding start or stop in
    # the original Ranges with these points; the
    # result must have at least one point since
    # we know that s1 and s2 are in the Ranges
    def _updated_range(r, first):
        st = sign(r.step)*step
        if r.start.is_finite:
            rv = Range(first, r.stop, st)
        else:
            rv = Range(r.start, first + st, st)
        return rv
    r1 = _updated_range(a, s1)
    r2 = _updated_range(b, s2)

    # work with them both in the increasing direction
    if sign(r1.step) < 0:
        r1 = r1.reversed
    if sign(r2.step) < 0:
        r2 = r2.reversed

    # return clipped Range with positive step; it
    # can't be empty at this point
    start = max(r1.start, r2.start)
    stop = min(r1.stop, r2.stop)
    return Range(start, stop, step)


@dispatch(Range, Integers)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return a


@dispatch(ImageSet, Set)  # type: ignore # noqa:F811
def intersection_sets(self, other): # noqa:F811
    from sympy.solvers.diophantine import diophantine

    # Only handle the straight-forward univariate case
    if (len(self.lamda.variables) > 1
            or self.lamda.signature != self.lamda.variables):
        return None
    base_set = self.base_sets[0]

    # Intersection between ImageSets with Integers as base set
    # For {f(n) : n in Integers} & {g(m) : m in Integers} we solve the
    # diophantine equations f(n)=g(m).
    # If the solutions for n are {h(t) : t in Integers} then we return
    # {f(h(t)) : t in integers}.
    # If the solutions for n are {n_1, n_2, ..., n_k} then we return
    # {f(n_i) : 1 <= i <= k}.
    if base_set is S.Integers:
        gm = None
        if isinstance(other, ImageSet) and other.base_sets == (S.Integers,):
            gm = other.lamda.expr
            var = other.lamda.variables[0]
            # Symbol of second ImageSet lambda must be distinct from first
            m = Dummy('m')
            gm = gm.subs(var, m)
        elif other is S.Integers:
            m = gm = Dummy('m')
        if gm is not None:
            fn = self.lamda.expr
            n = self.lamda.variables[0]
            try:
                solns = list(diophantine(fn - gm, syms=(n, m), permute=True))
            except (TypeError, NotImplementedError):
                # TypeError if equation not polynomial with rational coeff.
                # NotImplementedError if correct format but no solver.
                return
            # 3 cases are possible for solns:
            # - empty set,
            # - one or more parametric (infinite) solutions,
            # - a finite number of (non-parametric) solution couples.
            # Among those, there is one type of solution set that is
            # not helpful here: multiple parametric solutions.
            if len(solns) == 0:
                return EmptySet
            elif any(not isinstance(s, int) and s.free_symbols
                     for tupl in solns for s in tupl):
                if len(solns) == 1:
                    soln, solm = solns[0]
                    (t,) = soln.free_symbols
                    expr = fn.subs(n, soln.subs(t, n)).expand()
                    return imageset(Lambda(n, expr), S.Integers)
                else:
                    return
            else:
                return FiniteSet(*(fn.subs(n, s[0]) for s in solns))

    if other == S.Reals:
        from sympy.solvers.solveset import solveset_real
        from sympy.core.function import expand_complex

        f = self.lamda.expr
        n = self.lamda.variables[0]

        n_ = Dummy(n.name, real=True)
        f_ = f.subs(n, n_)

        re, im = f_.as_real_imag()
        im = expand_complex(im)

        re = re.subs(n_, n)
        im = im.subs(n_, n)
        ifree = im.free_symbols
        lam = Lambda(n, re)
        if not im:
            # allow re-evaluation
            # of self in this case to make
            # the result canonical
            pass
        elif im.is_zero is False:
            return S.EmptySet
        elif ifree != {n}:
            return None
        else:
            # univarite imaginary part in same variable
            base_set = base_set.intersect(solveset_real(im, n))
        return imageset(lam, base_set)

    elif isinstance(other, Interval):
        from sympy.solvers.solveset import (invert_real, invert_complex,
                                            solveset)

        f = self.lamda.expr
        n = self.lamda.variables[0]
        new_inf, new_sup = None, None
        new_lopen, new_ropen = other.left_open, other.right_open

        if f.is_real:
            inverter = invert_real
        else:
            inverter = invert_complex

        g1, h1 = inverter(f, other.inf, n)
        g2, h2 = inverter(f, other.sup, n)

        if all(isinstance(i, FiniteSet) for i in (h1, h2)):
            if g1 == n:
                if len(h1) == 1:
                    new_inf = h1.args[0]
            if g2 == n:
                if len(h2) == 1:
                    new_sup = h2.args[0]
            # TODO: Design a technique to handle multiple-inverse
            # functions

            # Any of the new boundary values cannot be determined
            if any(i is None for i in (new_sup, new_inf)):
                return


            range_set = S.EmptySet

            if all(i.is_real for i in (new_sup, new_inf)):
                # this assumes continuity of underlying function
                # however fixes the case when it is decreasing
                if new_inf > new_sup:
                    new_inf, new_sup = new_sup, new_inf
                new_interval = Interval(new_inf, new_sup, new_lopen, new_ropen)
                range_set = base_set.intersect(new_interval)
            else:
                if other.is_subset(S.Reals):
                    solutions = solveset(f, n, S.Reals)
                    if not isinstance(range_set, (ImageSet, ConditionSet)):
                        range_set = solutions.intersect(other)
                    else:
                        return

            if range_set is S.EmptySet:
                return S.EmptySet
            elif isinstance(range_set, Range) and range_set.size is not S.Infinity:
                range_set = FiniteSet(*list(range_set))

            if range_set is not None:
                return imageset(Lambda(n, f), range_set)
            return
        else:
            return


@dispatch(ProductSet, ProductSet)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    if len(b.args) != len(a.args):
        return S.EmptySet
    return ProductSet(*(i.intersect(j) for i, j in zip(a.sets, b.sets)))


@dispatch(Interval, Interval)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    # handle (-oo, oo)
    infty = S.NegativeInfinity, S.Infinity
    if a == Interval(*infty):
        l, r = a.left, a.right
        if l.is_real or l in infty or r.is_real or r in infty:
            return b

    # We can't intersect [0,3] with [x,6] -- we don't know if x>0 or x<0
    if not a._is_comparable(b):
        return None

    empty = False

    if a.start <= b.end and b.start <= a.end:
        # Get topology right.
        if a.start < b.start:
            start = b.start
            left_open = b.left_open
        elif a.start > b.start:
            start = a.start
            left_open = a.left_open
        else:
            start = a.start
            left_open = a.left_open or b.left_open

        if a.end < b.end:
            end = a.end
            right_open = a.right_open
        elif a.end > b.end:
            end = b.end
            right_open = b.right_open
        else:
            end = a.end
            right_open = a.right_open or b.right_open

        if end - start == 0 and (left_open or right_open):
            empty = True
    else:
        empty = True

    if empty:
        return S.EmptySet

    return Interval(start, end, left_open, right_open)

@dispatch(type(EmptySet), Set)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return S.EmptySet

@dispatch(UniversalSet, Set)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return b

@dispatch(FiniteSet, FiniteSet)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return FiniteSet(*(a._elements & b._elements))

@dispatch(FiniteSet, Set)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    try:
        return FiniteSet(*[el for el in a if el in b])
    except TypeError:
        return None  # could not evaluate `el in b` due to symbolic ranges.

@dispatch(Set, Set)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return None

@dispatch(Integers, Rationals)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return a

@dispatch(Naturals, Rationals)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return a

@dispatch(Rationals, Reals)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return a

def _intlike_interval(a, b):
    try:
        from sympy.functions.elementary.integers import floor, ceiling
        if b._inf is S.NegativeInfinity and b._sup is S.Infinity:
            return a
        s = Range(max(a.inf, ceiling(b.left)), floor(b.right) + 1)
        return intersection_sets(s, b)  # take out endpoints if open interval
    except ValueError:
        return None

@dispatch(Integers, Interval)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return _intlike_interval(a, b)

@dispatch(Naturals, Interval)  # type: ignore # noqa:F811
def intersection_sets(a, b): # noqa:F811
    return _intlike_interval(a, b)
