"""
07_python_network — hello pipeline with a Python node in the middle.

Graph:
  [ProduceNode] --int--> [py_double] --int--> [PrintItNode]

ProduceNode and PrintItNode are C++ nodes wrapped in VariantNodeWrapper.
py_double is a pure Python callable — doubles its input using Python arithmetic.
"""

import sys
import time
sys.path.insert(0, "build/python")

import kpn_python as kpn

def py_double(x: int) -> int:
    return x * 2

net = kpn.Network()

net.add("src",  kpn.make_produce())
net.add_node("dbl", py_double, inputs=["int"], outputs=["int"])
net.add("sink", kpn.make_print_it())

net.connect("src",  0, "dbl",  0)
net.connect("dbl",  0, "sink", 0)

net.build()
net.start()
time.sleep(0.1)
net.stop()

# Drop the network deterministically: it holds the Python callable, which forms
# a reference cycle via globals(). Deleting the global breaks it so the network
# is reclaimed now rather than lingering to interpreter shutdown.
del net