
from greenlet import greenlet
from . import TestCase
from .leakcheck import fails_leakcheck

class genlet(greenlet):
    parent = None
    def __init__(self, *args, **kwds):
        self.args = args
        self.kwds = kwds
        self.child = None

    def run(self):
        # Note the function is packed in a tuple
        # to avoid creating a bound method for it.
        fn, = self.fn
        fn(*self.args, **self.kwds)

    def __iter__(self):
        return self

    def set_child(self, child):
        self.child = child

    def __next__(self):
        if self.child:
            child = self.child
            while child.child:
                tmp = child
                child = child.child
                tmp.child = None

            result = child.switch()
        else:
            self.parent = greenlet.getcurrent()
            result = self.switch()

        if self:
            return result

        raise StopIteration

    next = __next__

def Yield(value, level=1):
    g = greenlet.getcurrent()

    while level != 0:
        if not isinstance(g, genlet):
            raise RuntimeError('yield outside a genlet')
        if level > 1:
            g.parent.set_child(g)
        g = g.parent
        level -= 1

    g.switch(value)


def Genlet(func):
    class TheGenlet(genlet):
        fn = (func,)
    return TheGenlet

# ____________________________________________________________


def g1(n, seen):
    for i in range(n):
        seen.append(i + 1)
        yield i


def g2(n, seen):
    for i in range(n):
        seen.append(i + 1)
        Yield(i)

g2 = Genlet(g2)


def nested(i):
    Yield(i)


def g3(n, seen):
    for i in range(n):
        seen.append(i + 1)
        nested(i)
g3 = Genlet(g3)


def a(n):
    if n == 0:
        return
    for ii in ax(n - 1):
        Yield(ii)
    Yield(n)
ax = Genlet(a)


def perms(l):
    if len(l) > 1:
        for e in l:
            # No syntactical sugar for generator expressions
            x = [Yield([e] + p) for p in perms([x for x in l if x != e])]
            assert x
    else:
        Yield(l)
perms = Genlet(perms)


def gr1(n):
    for ii in range(1, n):
        Yield(ii)
        Yield(ii * ii, 2)

gr1 = Genlet(gr1)


def gr2(n, seen):
    for ii in gr1(n):
        seen.append(ii)

gr2 = Genlet(gr2)


class NestedGeneratorTests(TestCase):
    def test_layered_genlets(self):
        seen = []
        for ii in gr2(5, seen):
            seen.append(ii)
        self.assertEqual(seen, [1, 1, 2, 4, 3, 9, 4, 16])

    @fails_leakcheck
    def test_permutations(self):
        gen_perms = perms(list(range(4)))
        permutations = list(gen_perms)
        self.assertEqual(len(permutations), 4 * 3 * 2 * 1)
        self.assertIn([0, 1, 2, 3], permutations)
        self.assertIn([3, 2, 1, 0], permutations)
        res = []
        for ii in zip(perms(list(range(4))), perms(list(range(3)))):
            res.append(ii)
        self.assertEqual(
            res,
            [([0, 1, 2, 3], [0, 1, 2]), ([0, 1, 3, 2], [0, 2, 1]),
             ([0, 2, 1, 3], [1, 0, 2]), ([0, 2, 3, 1], [1, 2, 0]),
             ([0, 3, 1, 2], [2, 0, 1]), ([0, 3, 2, 1], [2, 1, 0])])
        # XXX Test to make sure we are working as a generator expression

    def test_genlet_simple(self):
        for g in [g1, g2, g3]:
            seen = []
            for _ in range(3):
                for j in g(5, seen):
                    seen.append(j)
            self.assertEqual(seen, 3 * [1, 0, 2, 1, 3, 2, 4, 3, 5, 4])

    def test_genlet_bad(self):
        try:
            Yield(10)
        except RuntimeError:
            pass

    def test_nested_genlets(self):
        seen = []
        for ii in ax(5):
            seen.append(ii)
