import contextlib
import os
import threading
from textwrap import dedent
import unittest

from test.support import interpreters


def _captured_script(script):
    r, w = os.pipe()
    indented = script.replace('\n', '\n                ')
    wrapped = dedent(f"""
        import contextlib
        with open({w}, 'w', encoding='utf-8') as spipe:
            with contextlib.redirect_stdout(spipe):
                {indented}
        """)
    return wrapped, open(r, encoding='utf-8')


def clean_up_interpreters():
    for interp in interpreters.list_all():
        if interp.id == 0:  # main
            continue
        try:
            interp.close()
        except RuntimeError:
            pass  # already destroyed


def _run_output(interp, request, channels=None):
    script, rpipe = _captured_script(request)
    with rpipe:
        interp.exec_sync(script, channels=channels)
        return rpipe.read()


@contextlib.contextmanager
def _running(interp):
    r, w = os.pipe()
    def run():
        interp.exec_sync(dedent(f"""
            # wait for "signal"
            with open({r}) as rpipe:
                rpipe.read()
            """))

    t = threading.Thread(target=run)
    t.start()

    yield

    with open(w, 'w') as spipe:
        spipe.write('done')
    t.join()


class TestBase(unittest.TestCase):

    def pipe(self):
        def ensure_closed(fd):
            try:
                os.close(fd)
            except OSError:
                pass
        r, w = os.pipe()
        self.addCleanup(lambda: ensure_closed(r))
        self.addCleanup(lambda: ensure_closed(w))
        return r, w

    def tearDown(self):
        clean_up_interpreters()