import glob
import os
import shutil
import subprocess
from contextlib import contextmanager
from tempfile import mkdtemp


@contextmanager
def workdir():
    cwd = os.getcwd()
    tmpdir = mkdtemp()
    os.chdir(tmpdir)
    try:
        yield
    finally:
        os.chdir(cwd)
        shutil.rmtree(tmpdir)


@contextmanager
def redirect(stdchannel, dest_filename):
    oldstdchannel = os.dup(stdchannel.fileno())
    dest_file = open(dest_filename, 'w')
    os.dup2(dest_file.fileno(), stdchannel.fileno())
    try:
        yield
    finally:
        if oldstdchannel is not None:
            os.dup2(oldstdchannel, stdchannel.fileno())
        if dest_file is not None:
            dest_file.close()


def absolute(*paths):
    op = os.path
    return op.realpath(op.abspath(op.join(op.dirname(__file__), *paths)))


def build_flags(library, type_, path):
    """Return separated build flags from pkg-config output"""

    pkg_config_path = [path]
    if 'PKG_CONFIG_PATH' in os.environ:
        pkg_config_path.append(os.environ['PKG_CONFIG_PATH'])
    if 'LIB_DIR' in os.environ:
        pkg_config_path.append(os.environ['LIB_DIR'])
        pkg_config_path.append(os.path.join(os.environ['LIB_DIR'], 'pkgconfig'))

    options = ['--static', {'I': '--cflags-only-I', 'L': '--libs-only-L', 'l': '--libs-only-l'}[type_]]

    return [
        flag.strip('-{}'.format(type_))
        for flag in subprocess.check_output(
            ['pkg-config'] + options + [library], env=dict(os.environ, PKG_CONFIG_PATH=':'.join(pkg_config_path))
        )
        .decode('UTF-8')
        .split()
    ]


def _find_lib():
    if 'COINCURVE_IGNORE_SYSTEM_LIB' in os.environ:
        return False

    from cffi import FFI

    ffi = FFI()
    try:
        ffi.dlopen('secp256k1')
        if os.path.exists('/usr/include/secp256k1_ecdh.h'):
            return True
        else:
            # The system library lacks the ecdh module
            return False
    except OSError:
        if 'LIB_DIR' in os.environ:
            for path in glob.glob(os.path.join(os.environ['LIB_DIR'], '*secp256k1*')):
                try:
                    FFI().dlopen(path)
                    return True
                except OSError:
                    pass
        # We couldn't locate libsecp256k1 so we'll use the bundled one
        return False
    else:
        # If we got this far then the system library should be good enough
        return True


_has_system_lib = None


def has_system_lib():
    global _has_system_lib
    if _has_system_lib is None:
        _has_system_lib = _find_lib()
    return _has_system_lib


def detect_dll():
    here = os.path.dirname(os.path.abspath(__file__))
    for fn in os.listdir(os.path.join(here, 'coincurve')):
        if fn.endswith('.dll'):
            return True
    return False