# Licensed under a 3-clause BSD style license - see LICENSE.rst
""" This module contains functions to determine where configuration and
data/cache files used by Astropy should be placed.
"""

from ..utils.decorators import wraps

import os
import shutil
import sys


__all__ = ['get_config_dir', 'get_cache_dir', 'set_temp_config',
           'set_temp_cache']


def _find_home():
    """ Locates and return the home directory (or best approximation) on this
    system.

    Raises
    ------
    OSError
        If the home directory cannot be located - usually means you are running
        Astropy on some obscure platform that doesn't have standard home
        directories.
    """

    # First find the home directory - this is inspired by the scheme ipython
    # uses to identify "home"
    if os.name == 'posix':
        # Linux, Unix, AIX, OS X
        if 'HOME' in os.environ:
            homedir = os.environ['HOME']
        else:
            raise OSError('Could not find unix home directory to search for '
                          'astropy config dir')
    elif os.name == 'nt':  # This is for all modern Windows (NT or after)
        if 'MSYSTEM' in os.environ and os.environ.get('HOME'):
            # Likely using an msys shell; use whatever it is using for its
            # $HOME directory
            homedir = os.environ['HOME']
        # Next try for a network home
        elif 'HOMESHARE' in os.environ:
            homedir = os.environ['HOMESHARE']
        # See if there's a local home
        elif 'HOMEDRIVE' in os.environ and 'HOMEPATH' in os.environ:
            homedir = os.path.join(os.environ['HOMEDRIVE'],
                                   os.environ['HOMEPATH'])
        # Maybe a user profile?
        elif 'USERPROFILE' in os.environ:
            homedir = os.path.join(os.environ['USERPROFILE'])
        else:
            try:
                import winreg as wreg
                shell_folders = r'Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders'
                key = wreg.OpenKey(wreg.HKEY_CURRENT_USER, shell_folders)

                homedir = wreg.QueryValueEx(key, 'Personal')[0]
                key.Close()
            except Exception:
                # As a final possible resort, see if HOME is present
                if 'HOME' in os.environ:
                    homedir = os.environ['HOME']
                else:
                    raise OSError('Could not find windows home directory to '
                                  'search for astropy config dir')
    else:
        # for other platforms, try HOME, although it probably isn't there
        if 'HOME' in os.environ:
            homedir = os.environ['HOME']
        else:
            raise OSError('Could not find a home directory to search for '
                          'astropy config dir - are you on an unspported '
                          'platform?')
    return homedir


def get_config_dir(create=True):
    """
    Determines the Astropy configuration directory name and creates the
    directory if it doesn't exist.

    This directory is typically ``$HOME/.astropy/config``, but if the
    XDG_CONFIG_HOME environment variable is set and the
    ``$XDG_CONFIG_HOME/astropy`` directory exists, it will be that directory.
    If neither exists, the former will be created and symlinked to the latter.

    Returns
    -------
    configdir : str
        The absolute path to the configuration directory.

    """

    # symlink will be set to this if the directory is created
    linkto = None

    # If using set_temp_config, that overrides all
    if set_temp_config._temp_path is not None:
        xch = set_temp_config._temp_path
        config_path = os.path.join(xch, 'astropy')
        if not os.path.exists(config_path):
            os.mkdir(config_path)
        return os.path.abspath(config_path)

    # first look for XDG_CONFIG_HOME
    xch = os.environ.get('XDG_CONFIG_HOME')

    if xch is not None and os.path.exists(xch):
        xchpth = os.path.join(xch, 'astropy')
        if not os.path.islink(xchpth):
            if os.path.exists(xchpth):
                return os.path.abspath(xchpth)
            else:
                linkto = xchpth
    return os.path.abspath(_find_or_create_astropy_dir('config', linkto))


def get_cache_dir():
    """
    Determines the Astropy cache directory name and creates the directory if it
    doesn't exist.

    This directory is typically ``$HOME/.astropy/cache``, but if the
    XDG_CACHE_HOME environment variable is set and the