from sympy import (symbols, Symbol, product, factorial, rf, sqrt, cos,
                   Function, Product, Rational, Sum, oo, exp, log, S)
from sympy.utilities.pytest import raises
from sympy import simplify

a, k, n, m, x = symbols('a,k,n,m,x', integer=True)
f = Function('f')


def test_karr_convention():
    # Test the Karr product convention that we want to hold.
    # See his paper "Summation in Finite Terms" for a detailed
    # reasoning why we really want exactly this definition.
    # The convention is described for sums on page 309 and
    # essentially in section 1.4, definition 3. For products
    # we can find in analogy:
    #
    # \prod_{m <= i < n} f(i) 'has the obvious meaning'      for m < n
    # \prod_{m <= i < n} f(i) = 0                            for m = n
    # \prod_{m <= i < n} f(i) = 1 / \prod_{n <= i < m} f(i)  for m > n
    #
    # It is important to note that he defines all products with
    # the upper limit being *exclusive*.
    # In contrast, sympy and the usual mathematical notation has:
    #
    # prod_{i = a}^b f(i) = f(a) * f(a+1) * ... * f(b-1) * f(b)
    #
    # with the upper limit *inclusive*. So translating between
    # the two we find that:
    #
    # \prod_{m <= i < n} f(i) = \prod_{i = m}^{n-1} f(i)
    #
    # where we intentionally used two different ways to typeset the
    # products and its limits.

    i = Symbol("i", integer=True)
    k = Symbol("k", integer=True)
    j = Symbol("j", integer=True)

    # A simple example with a concrete factors and symbolic limits.

    # The normal product: m = k and n = k + j and therefore m < n:
    m = k
    n = k + j

    a = m
    b = n - 1
    S1 = Product(i**2, (i, a, b)).doit()

    # The reversed product: m = k + j and n = k and therefore m > n:
    m = k + j
    n = k

    a = m
    b = n - 1
    S2 = Product(i**2, (i, a, b)).doit()

    assert simplify(S1 * S2) == 1

    # Test the empty product: m = k and n = k and therefore m = n:
    m = k
    n = k

    a = m
    b = n - 1
    Sz = Product(i**2, (i, a, b)).doit()

    assert Sz == 1

    # Another example this time with an unspecified factor and
    # numeric limits. (We can not do both tests in the same example.)
    f = Function("f")

    # The normal product with m < n:
    m = 2
    n = 11

    a = m
    b = n - 1
    S1 = Product(f(i), (i, a, b)).doit()

    # The reversed product with m > n:
    m = 11
    n = 2

    a = m
    b = n - 1
    S2 = Product(f(i), (i, a, b)).doit()

    assert simplify(S1 * S2) == 1

    # Test the empty product with m = n:
    m = 5
    n = 5

    a = m
    b = n - 1
    Sz = Product(f(i), (i, a, b)).doit()

    assert Sz == 1


def test_karr_proposition_2a():
    # Test Karr, page 309, proposition 2, part a
    i = Symbol("i", integer=True)
    u = Symbol("u", integer=True)
    v = Symbol("v", integer=True)

    def test_the_product(m, n):
        # g
        g = i**3 + 2*i**2 - 3*i
        # f = Delta g
        f = simplify(g.subs(i, i+1) / g)
        # The product
        a = m
        b = n - 1
        P = Product(f, (i, a, b)).doit()
        # Test if Product_{m <= i < n} f(i) = g(n) / g(m)
        assert simplify(P / (g.subs(i, n) / g.subs(i, m))) == 1

    # m < n
    test_the_product(u, u+v)
    # m = n
    test_the_product(u, u)
    # m > n
    test_the_product(u+v, u)


def test_karr_proposition_2b():
    # Test Karr, page 309, proposition 2, part b
    i = Symbol("i", integer=True)
    u = Symbol("u", integer=True)
    v = Symbol("v", integer=True)
    w = Symbol("w", integer=True)

    def test_the_product(l, n, m):
        # Productmand
        s = i**3
        # First product
        a = l
        b = n - 1
        S1 = Product(s, (i, a, b)).doit()
        # Second product
        a = l
        b = m - 1
        S2 = Product(s, (i, a, b)).doit()
        # Third product
        a = m
        b = n - 1
        S3 = Product(s, (i, a, b)).doit()
        # Test if S1 = S2 * S3 as required
        assert simplify(S1 / (S2 * S3)) == 1

    # l < m < n
    test_the_product(u, u+v, u+v+w)
    # l < m = n
    test_the_product(u, u+v, u+v)
    # l < m > n
    test_the_product(u, u+v+w, v)
    # l = m < n
    test_the_product(u, u, u+v)
    # l = m = n
    test_the_product(u, u, u)
    # l = m > n
    test_the_product(u+v, u+v, u)
    # l > m < n
    test_the_product(u+v, u, u+w)
    # l > m = n
    test_the_product(u+v, u, u)
    # l > m > n
    test_the_product(u+v+w, u+v, u)


def test_simple_products():
    assert product(2, (k, a, n)) == 2**(n - a + 1)
    assert product(k, (k, 1, n)) == factorial(n)
    assert product(k**3, (k, 1, n)) == factorial(n)**3

    assert product(k + 1, (k, 0, n - 1)) == factorial(n)
    assert product(k + 1, (k, a, n - 1)) == rf(1 + a, n - a)

    assert product(cos(k), (k, 0, 5)) == cos(1)*cos(2)*cos(3)*cos(4)*cos(5)
    assert product(cos(k), (k, 3, 5)) == cos(3)*cos(4)*cos(5)
    assert product(cos(k), (k, 1, Rational(5, 2))) != cos(1)*cos(2)

    assert isinstance(product(k**k, (k, 1, n)), Product)

    assert Product(x**k, (k, 1, n)).variables == [k]

    raises(ValueError, lambda: Product(n))
    raises(ValueError, lambda: Product(n, k))
    raises(ValueError, lambda: Product(n, k, 1))
    raises(ValueError, lambda: Product(n, k, 1, 10))
    raises(ValueError, lambda: Product(n, (k, 1)))

    assert product(1, (n, 1, oo)) == 1  # issue 8301
    assert product(2, (n, 1, oo)) == oo
    assert product(-1, (n, 1, oo)).func is Product


def test_multiple_products():
    assert product(x, (n, 1, k), (k, 1, m)) == x**(m**2/2 + m/2)
    assert product(f(n), (
        n, 1, m), (m, 1, k)) == Product(f(n), (n, 1, m), (m, 1, k)).doit()
    assert Product(f(n), (m, 1, k), (n, 1, k)).doit() == \
        Product(Product(f(n), (m, 1, k)), (n, 1, k)).doit() == \
        product(f(n), (m, 1, k), (n, 1, k)) == \
        product(product(f(n), (m, 1, k)), (n, 1, k)) == \
        Product(f(n)**k, (n, 1, k))
    assert Product(
        x, (x, 1, k), (k, 1, n)).doit() == Product(factorial(k), (k, 1, n))

    assert Product(x**k, (n, 1, k), (k, 1, m)).variables == [n, k]


def test_rational_products():
    assert product(1 + 1/k, (k, 1, n)) == rf(2, n)/factorial(n)


def test_special_products():
    # Wallis product
    assert product((4*k)**2 / (4*k**2 - 1), (k, 1, n)) == \
        4**n*factorial(n)**2/rf(Rational(1, 2), n)/rf(Rational(3, 2), n)

    # Euler's product formula for sin
    assert product(1 + a/k**2, (k, 1, n)) == \
        rf(1 - sqrt(-a), n)*rf(1 + sqrt(-a), n)/factorial(n)**2


def test__eval_product():
    from sympy.abc import i, n
    # issue 4809
    a = Function('a')
    assert product(2*a(i), (i, 1, n)) == 2**n * Product(a(i), (i, 1, n))
    # issue 4810
    assert product(2**i, (i, 1, n)) == 2**(n/2 + n**2/2)


def test_product_pow():
    # issue 4817
    assert product(2**f(k), (k, 1, n)) == 2**Sum(f(k), (k, 1, n))
    assert product(2**(2*f(k)), (k, 1, n)) == 2**Sum(2*f(k), (k, 1, n))


def test_infinite_product():
    # issue 5737
    assert isinstance(Product(2**(1/factorial(n)), (n, 0, oo)), Product)


def test_conjugate_transpose():
    p = Product(x**k, (k, 1, 3))
    assert p.adjoint().doit() == p.doit().adjoint()
    assert p.conjugate().doit() == p.doit().conjugate()
    assert p.transpose().doit() == p.doit().transpose()

    A, B = symbols("A B", commutative=False)
    p = Product(A*B**k, (k, 1, 3))
    assert p.adjoint().doit() == p.doit().adjoint()
    assert p.conjugate().doit() == p.doit().conjugate()
    assert p.transpose().doit() == p.doit().transpose()


def test_simplify():
    y, t, b, c = symbols('y, t, b, c', integer = True)

    assert simplify(Product(x*y, (x, n, m), (y, a, k)) * \
        Product(y, (x, n, m), (y, a, k))) == \
            Product(x*y**2, (x, n, m), (y, a, k))
    assert simplify(3 * y* Product(x, (x, n, m)) * Product(x, (x, m + 1, a))) \
        == 3 * y * Product(x, (x, n, a))
    assert simplify(Product(x, (x, k + 1, a)) * Product(x, (x, n, k))) == \
        Product(x, (x, n, a))
    assert simplify(Product(x, (x, k + 1, a)) * Product(x + 1, (x, n, k))) == \
        Product(x, (x, k + 1, a)) * Product(x + 1, (x, n, k))
    assert simplify(Product(x, (t, a, b)) * Product(y, (t, a, b)) * \
        Product(x, (t, b+1, c))) == Product(x*y, (t, a, b)) * \
            Product(x, (t, b+1, c))
    assert simplify(Product(x, (t, a, b)) * Product(x, (t, b+1, c)) * \
        Product(y, (t, a, b))) == Product(x*y, (t, a, b)) * \
            Product(x, (t, b+1, c))


def test_change_index():
    b, y, c, d, z = symbols('b, y, c, d, z', integer = True)

    assert Product(x, (x, a, b)).change_index(x, x + 1, y) == \
        Product(y - 1, (y, a + 1, b + 1))
    assert Product(x**2, (x, a, b)).change_index(x, x - 1) == \
        Product((x + 1)**2, (x, a - 1, b - 1))
    assert Product(x**2, (x, a, b)).change_index(x, -x, y) == \
        Product((-y)**2, (y, -b, -a))
    assert Product(x, (x, a, b)).change_index(x, -x - 1) == \
        Product(-x - 1, (x, - b - 1, -a - 1))
    assert Product(x*y, (x, a, b), (y, c, d)).change_index(x, x - 1, z) == \
        Product((z + 1)*y, (z, a - 1, b - 1), (y, c, d))


def test_reorder():
    b, y, c, d, z = symbols('b, y, c, d, z', integer = True)

    assert Product(x*y, (x, a, b), (y, c, d)).reorder((0, 1)) == \
        Product(x*y, (y, c, d), (x, a, b))
    assert Product(x, (x, a, b), (x, c, d)).reorder((0, 1)) == \
        Product(x, (x, c, d), (x, a, b))
    assert Product(x*y + z, (x, a, b), (z, m, n), (y, c, d)).reorder(\
        (2, 0), (0, 1)) == Product(x*y + z, (z, m, n), (y, c, d), (x, a, b))
    assert Product(x*y*z, (x, a, b), (y, c, d), (z, m, n)).reorder(\
        (0, 1), (1, 2), (0, 2)) == \
        Product(x*y*z, (x, a, b), (z, m, n), (y, c, d))
    assert Product(x*y*z, (x, a, b), (y, c, d), (z, m, n)).reorder(\
        (x, y), (y, z), (x, z)) == \
        Product(x*y*z, (x, a, b), (z, m, n), (y, c, d))
    assert Product(x*y, (x, a, b), (y, c, d)).reorder((x, 1)) == \
        Product(x*y, (y, c, d), (x, a, b))
    assert Product(x*y, (x, a, b), (y, c, d)).reorder((y, x)) == \
        Product(x*y, (y, c, d), (x, a, b))


def test_Product_is_convergent():
    assert Product(1/n**2, (n, 1, oo)).is_convergent() is S.false
    assert Product(exp(1/n**2), (n, 1, oo)).is_convergent() is S.true
    assert Product(1/n, (n, 1, oo)).is_convergent() is S.false
    assert Product(1 + 1/n, (n, 1, oo)).is_convergent() is S.false
    assert Product(1 + 1/n**2, (n, 1, oo)).is_convergent() is S.true


def test_reverse_order():
    x, y, a, b, c, d= symbols('x, y, a, b, c, d', integer = True)

    assert Product(x, (x, 0, 3)).reverse_order(0) == Product(1/x, (x, 4, -1))
    assert Product(x*y, (x, 1, 5), (y, 0, 6)).reverse_order(0, 1) == \
           Product(x*y, (x, 6, 0), (y, 7, -1))
    assert Product(x, (x, 1, 2)).reverse_order(0) == Product(1/x, (x, 3, 0))
    assert Product(x, (x, 1, 3)).reverse_order(0) == Product(1/x, (x, 4, 0))
    assert Product(x, (x, 1, a)).reverse_order(0) == Product(1/x, (x, a + 1, 0))
    assert Product(x, (x, a, 5)).reverse_order(0) == Product(1/x, (x, 6, a - 1))
    assert Product(x, (x, a + 1, a + 5)).reverse_order(0) == \
           Product(1/x, (x, a + 6, a))
    assert Product(x, (x, a + 1, a + 2)).reverse_order(0) == \
           Product(1/x, (x, a + 3, a))
    assert Product(x, (x, a + 1, a + 1)).reverse_order(0) == \
           Product(1/x, (x, a + 2, a))
    assert Product(x, (x, a, b)).reverse_order(0) == Product(1/x, (x, b + 1, a - 1))
    assert Product(x, (x, a, b)).reverse_order(x) == Product(1/x, (x, b + 1, a - 1))
    assert Product(x*y, (x, a, b), (y, 2, 5)).reverse_order(x, 1) == \
           Product(x*y, (x, b + 1, a - 1), (y, 6, 1))
    assert Product(x*y, (x, a, b), (y, 2, 5)).reverse_order(y, x) == \
           Product(x*y, (x, b + 1, a - 1), (y, 6, 1))


def test_rewrite_Sum():
    assert Product(1 - S.Half**2/k**2, (k, 1, oo)).rewrite(Sum) == \
        exp(Sum(log(1 - 1/(4*k**2)), (k, 1, oo)))
