import os

import pytest

from .files import build_files
from .textwrap import DALS


futures = pytest.importorskip('concurrent.futures')
importlib = pytest.importorskip('importlib')


class BuildBackendBase(object):
    def __init__(self, cwd=None, env={}, backend_name='setuptools.build_meta'):
        self.cwd = cwd
        self.env = env
        self.backend_name = backend_name


class BuildBackend(BuildBackendBase):
    """PEP 517 Build Backend"""
    def __init__(self, *args, **kwargs):
        super(BuildBackend, self).__init__(*args, **kwargs)
        self.pool = futures.ProcessPoolExecutor()

    def __getattr__(self, name):
        """Handles aribrary function invocations on the build backend."""
        def method(*args, **kw):
            root = os.path.abspath(self.cwd)
            caller = BuildBackendCaller(root, self.env, self.backend_name)
            return self.pool.submit(caller, name, *args, **kw).result()

        return method


class BuildBackendCaller(BuildBackendBase):
    def __call__(self, name, *args, **kw):
        """Handles aribrary function invocations on the build backend."""
        os.chdir(self.cwd)
        os.environ.update(self.env)
        mod = importlib.import_module(self.backend_name)
        return getattr(mod, name)(*args, **kw)


@pytest.fixture
def build_backend(tmpdir):
    defn = {
        'setup.py': DALS("""
            __import__('setuptools').setup(
                name='foo',
                py_modules=['hello'],
                setup_requires=['six'],
            )
            """),
        'hello.py': DALS("""
            def run():
                print('hello')
            """),
    }
    build_files(defn, prefix=str(tmpdir))
    with tmpdir.as_cwd():
        yield BuildBackend(cwd='.')


def test_get_requires_for_build_wheel(build_backend):
    actual = build_backend.get_requires_for_build_wheel()
    expected = ['six', 'setuptools', 'wheel']
    assert sorted(actual) == sorted(expected)


def test_build_wheel(build_backend):
    dist_dir = os.path.abspath('pip-wheel')
    os.makedirs(dist_dir)
    wheel_name = build_backend.build_wheel(dist_dir)

    assert os.path.isfile(os.path.join(dist_dir, wheel_name))


def test_build_sdist(build_backend):
    dist_dir = os.path.abspath('pip-sdist')
    os.makedirs(dist_dir)
    sdist_name = build_backend.build_sdist(dist_dir)

    assert os.path.isfile(os.path.join(dist_dir, sdist_name))


def test_prepare_metadata_for_build_wheel(build_backend):
    dist_dir = os.path.abspath('pip-dist-info')
    os.makedirs(dist_dir)

    dist_info = build_backend.prepare_metadata_for_build_wheel(dist_dir)

    assert os.path.isfile(os.path.join(dist_dir, dist_info, 'METADATA'))