import py

try:

    from py.magic import greenlet

except (ImportError, RuntimeError), e:

    py.test.skip(str(e))

class genlet(greenlet):

    def __init__(self, *args, **kwds):

        self.args = args

        self.kwds = kwds

    def run(self):

        fn, = self.fn

        fn(*self.args, **self.kwds)

    def __iter__(self):

        return self

    def next(self):

        self.parent = greenlet.getcurrent()

        result = self.switch()

        if self:

            return result

        else:

            raise StopIteration

def Yield(value):

    g = greenlet.getcurrent()

    while not isinstance(g, genlet):

        if g is None:

            raise RuntimeError, 'yield outside a genlet'

        g = g.parent

    g.parent.switch(value)

def generator(func):

    class generator(genlet):

        fn = (func,)

    return generator

# ____________________________________________________________

def test_generator():

    seen = []

    def g(n):

        for i in range(n):

            seen.append(i)

            Yield(i)

    g = generator(g)

    for k in range(3):

        for j in g(5):

            seen.append(j)

    assert seen == 3 * [0, 0, 1, 1, 2, 2, 3, 3, 4, 4]