from sympy import symbols, Integer

from sympy.physics.quantum.dagger import Dagger
from sympy.physics.quantum.commutator import Commutator as Comm
from sympy.physics.quantum.operator import Operator


a, b, c = symbols('a,b,c')
A, B, C, D = symbols('A,B,C,D', commutative=False)


def test_commutator():
    c = Comm(A,B)
    assert c.is_commutative == False
    assert isinstance(c, Comm)
    assert c.subs(A,C) == Comm(C,B)


def test_commutator_identities():
    assert Comm(a*A,b*B) == a*b*Comm(A,B)
    assert Comm(A, A) == 0
    assert Comm(a, b) == 0
    assert Comm(A,B) == -Comm(B,A)
    assert Comm(A,B).doit() == A*B - B*A
    assert Comm(A,B*C).expand(commutator=True) == Comm(A,B)*C + B*Comm(A,C)
    assert Comm(A*B,C).expand(commutator=True) == A*Comm(B,C) + Comm(A,C)*B
    assert Comm(A+B,C).expand(commutator=True) == Comm(A,C) + Comm(B,C)
    assert Comm(A,B+C).expand(commutator=True) == Comm(A,B) + Comm(A,C)
    e = Comm(A,Comm(B,C))+Comm(B,Comm(C,A))+Comm(C,Comm(A,B))
    assert e.doit().expand() == 0


def test_commutator_dagger():
    comm = Comm(A*B,C)
    assert Dagger(comm).expand(commutator=True) ==\
        - Comm(Dagger(B),Dagger(C))*Dagger(A) -\
        Dagger(B)*Comm(Dagger(A),Dagger(C))


class Foo(Operator):

    def _eval_commutator_Bar(self, bar):
        return Integer(0)


class Bar(Operator):
    pass


class Tam(Operator):

    def _eval_commutator_Foo(self, foo):
        return Integer(1)


def test_eval_commutator():
    F = Foo('F')
    B = Bar('B')
    T = Tam('T')
    assert Comm(F,B).doit() == 0
    assert Comm(B,F).doit() == 0
    assert Comm(F,T).doit() == -1
    assert Comm(T,F).doit() == 1
    assert Comm(B,T).doit() == B*T - T*B
