from __future__ import absolute_import

from copy import copy
from functools import wraps
from itertools import chain
import os
import sys
import urllib

from django.conf import settings

from .subprocess import check_output


def _options_to_args(**options):
    """Converts ``options`` into a list of command-line arguments."""
    flags = []
    for name in sorted(options):
        value = options[name]
        if value is None:
            continue
        flags.append('--' + name.replace('_', '-'))
        if value is not True:
            flags.append(unicode(value))
    return flags


def wkhtmltopdf(pages, output=None, **kwargs):
    """
    Converts html to PDF using http://code.google.com/p/wkhtmltopdf/.

    pages: List of file paths or URLs of the html to be converted.
    output: Optional output file path. If None, the output is returned.
    **kwargs: Passed to wkhtmltopdf via _extra_args() (See
              https://github.com/antialize/wkhtmltopdf/blob/master/README_WKHTMLTOPDF
              for acceptable args.)
              Kwargs is passed through as arguments. e.g.:
                  {'footer_html': 'http://example.com/foot.html'}
              becomes
                  '--footer-html http://example.com/foot.html'

              Where there is no value passed, use True. e.g.:
                  {'disable_javascript': True}
              becomes:
                  '--disable-javascript'

              To disable a default option, use None. e.g:
                  {'quiet': None'}
              becomes:
                  ''

    example usage:
        wkhtmltopdf(pages=['/tmp/example.html'],
                    dpi=300,
                    orientation='Landscape',
                    disable_javascript=True)
    """
    if isinstance(pages, basestring):
        # Support a single page.
        pages = [pages]

    if output is None:
        # Standard output.
        output = '-'

    # Default options:
    options = getattr(settings, 'WKHTMLTOPDF_CMD_OPTIONS', None)
    if options is None:
        options = {'quiet': True}
    else:
        options = copy(options)
    options.update(kwargs)

    # Force --encoding utf8 unless the user has explicitly overridden this.
    options.setdefault('encoding', 'utf8')

    env = getattr(settings, 'WKHTMLTOPDF_ENV', None)
    if env is not None:
        env = dict(os.environ, **env)

    cmd = getattr(settings, 'WKHTMLTOPDF_CMD', 'wkhtmltopdf')
    args = list(chain([cmd],
                      _options_to_args(**options),
                      list(pages),
                      [output]))
    return check_output(args, stderr=sys.stderr, env=env)


def content_disposition_filename(filename):
    """
    Sanitize a file name to be used in the Content-Disposition HTTP
    header.

    Even if the standard is quite permissive in terms of
    characters, there are a lot of edge cases that are not supported by
    different browsers.

    See http://greenbytes.de/tech/tc2231/#attmultinstances for more details.
    """
    filename = filename.replace(';', '').replace('"', '')
    return http_quote(filename)


def http_quote(string):
    """
    Given a unicode string, will do its dandiest to give you back a
    valid ascii charset string you can use in, say, http headers and the
    like.
    """
    if isinstance(string, unicode):
        try:
            import unidecode
            string = unidecode.unidecode(string)
        except ImportError:
            string = string.encode('ascii', 'replace')
    # Wrap in double-quotes for ; , and the like
    return '"{0!s}"'.format(string.replace('\\', '\\\\').replace('"', '\\"'))


def pathname2fileurl(pathname):
    """Returns a file:// URL for pathname. Handles OS-specific conversions."""
    return 'file://' + urllib.pathname2url(pathname)


try:
    # From Django 1.4
    from django.conf import override_settings
except ImportError:
    class override_settings(object):
        """
        Acts as either a decorator, or a context manager. If it's a decorator it
        takes a function and returns a wrapped function. If it's a contextmanager
        it's used with the ``with`` statement. In either event entering/exiting
        are called before and after, respectively, the function/block is executed.
        """
        def __init__(self, **kwargs):
            self.options = kwargs
            self.wrapped = settings._wrapped

        def __enter__(self):
            self.enable()

        def __exit__(self, exc_type, exc_value, traceback):
            self.disable()

        def __call__(self, test_func):
            from django.test import TransactionTestCase
            if isinstance(test_func, type) and issubclass(test_func, TransactionTestCase):
                original_pre_setup = test_func._pre_setup
                original_post_teardown = test_func._post_teardown
                def _pre_setup(innerself):
                    self.enable()
                    original_pre_setup(innerself)
                def _post_teardown(innerself):
                    original_post_teardown(innerself)
                    self.disable()
                test_func._pre_setup = _pre_setup
                test_func._post_teardown = _post_teardown
                return test_func
            else:
                @wraps(test_func)
                def inner(*args, **kwargs):
                    with self:
                        return test_func(*args, **kwargs)
            return inner

        def enable(self):
            override = copy(settings._wrapped)
            for key, new_value in self.options.items():
                setattr(override, key, new_value)
            settings._wrapped = override

        def disable(self):
            settings._wrapped = self.wrapped