"""
Wrap conda commandline program
"""
import os
import subprocess
import json
import hashlib
import contextlib
import tempfile
import urllib.request
from distutils.version import LooseVersion as V


def md5_file(fname):
    """
    Return md5 of a given filename

    Copied from https://stackoverflow.com/a/3431838
    """
    hash_md5 = hashlib.md5()
    with open(fname, "rb") as f:
        for chunk in iter(lambda: f.read(4096), b""):
            hash_md5.update(chunk)
    return hash_md5.hexdigest()


def check_miniconda_version(prefix, version):
    """
    Return true if a miniconda install with version exists at prefix
    """
    try:
        installed_version = subprocess.check_output([
            os.path.join(prefix, 'bin', 'conda'),
            '-V'
        ]).decode().strip().split()[1]
        return V(installed_version) >= V(version)
    except (subprocess.CalledProcessError, FileNotFoundError):
        # Conda doesn't exist
        return False


@contextlib.contextmanager
def download_miniconda_installer(version, md5sum):
    """
    Context manager to download miniconda installer of given version.

    This should be used as a contextmanager. It downloads miniconda installer
    of given version, verifies the md5sum & provides path to it to the `with`
    block to run.
    """
    with tempfile.NamedTemporaryFile() as f:
        installer_url = "https://repo.continuum.io/miniconda/Miniconda3-{}-Linux-x86_64.sh".format(version)
        urllib.request.urlretrieve(installer_url, f.name)

        if md5_file(f.name) != md5sum:
            raise Exception('md5 hash mismatch! Downloaded file corrupted')

        yield f.name


def install_miniconda(installer_path, prefix):
    """
    Install miniconda with installer at installer_path under prefix
    """
    subprocess.check_output([
        '/bin/bash',
        installer_path,
        '-u', '-b',
        '-p', prefix
    ], stderr=subprocess.STDOUT)
    # fix permissions on initial install
    # a few files have the wrong ownership and permissions initially
    # when the installer is run as root
    subprocess.check_call(
        ["chown", "-R", "{}:{}".format(os.getuid(), os.getgid()), prefix]
    )
    subprocess.check_call(["chmod", "-R", "o-w", prefix])


def ensure_conda_env(prefix):
    """
    Ensure a conda environment in the prefix
    """
    conda_executable = [os.path.join(prefix, 'bin', 'python'), '-m', 'conda']
    abspath = os.path.abspath(prefix)
    try:
        output = json.loads(
            subprocess.check_output(conda_executable + ['create', '--json', '--prefix', abspath]).decode()
        )
    except subprocess.CalledProcessError as e:
        output = json.loads(e.output.decode())
        if 'error' in output and output['error'] == f'CondaValueError: prefix already exists: {abspath}':
            return
        raise
    if 'success' in output and output['success'] == True:
        return


def ensure_conda_packages(prefix, packages):
    """
    Ensure packages (from conda-forge) are installed in the conda prefix.
    """
    conda_executable = [os.path.join(prefix, 'bin', 'python'), '-m', 'conda']
    abspath = os.path.abspath(prefix)
    # Let subprocess errors propagate
    # FIXME: raise different exception when using
    raw_output = subprocess.check_output(conda_executable + [
        'install',
        '-c', 'conda-forge',  # Make customizable if we ever need to
        '--json',
        '--prefix', abspath
    ] + packages).decode()
    # `conda install` outputs JSON lines for fetch updates,
    # and a undelimited output at the end. There is no reasonable way to
    # parse this outside of this kludge.
    filtered_output = '\n'.join([
        l for l in raw_output.split('\n')
        # Sometimes the JSON messages start with a \x00. The lstrip removes these.
        # conda messages seem to randomly throw \x00 in places for no reason
        if not l.lstrip('\x00').startswith('{"fetch"')
    ])
    output = json.loads(filtered_output.lstrip('\x00'))
    if 'success' in output and output['success'] == True:
        return


def ensure_pip_packages(prefix, packages):
    """
    Ensure pip packages are installed in the given conda prefix.
    """
    abspath = os.path.abspath(prefix)
    pip_executable = [os.path.join(abspath, 'bin', 'python'), '-m', 'pip']

    subprocess.check_output(pip_executable + [
        'install',
        '--no-cache-dir',
    ] + packages)


def ensure_pip_requirements(prefix, requirements_path):
    """
    Ensure pip packages from given requirements_path are installed in given conda prefix.

    requirements_path can be a file or a URL.
    """
    abspath = os.path.abspath(prefix)
    pip_executable = [os.path.join(abspath, 'bin', 'python'), '-m', 'pip']

    subprocess.check_output(pip_executable + [
        'install',
        '-r',
        requirements_path
    ])