"""This file houses various core utility functions"""
from contextlib import contextmanager
import datetime
import logging
import os
import re
import tempfile

from django.contrib.sites.models import Site
from django.conf import settings
import django.core.mail

import core.tasks


class TemporaryFile(object):
    """Context manager class for working with temporary files.

    The file will be closed and removed when the context is exited.
    """
    def __init__(self, **kwargs):
        """kwargs will be passed to mkstemp."""
        self.kwargs = kwargs

    def __enter__(self):
        self.fd, self.filename = tempfile.mkstemp(**self.kwargs)
        self.file = os.fdopen(self.fd, 'w+b')
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        self.file.close()
        os.remove(self.filename)


@contextmanager
def remove_file(path):
    """Context manager for removing a file when the context is exited."""
    try:
        yield path
    finally:
        os.remove(path)


def send_mail(subject, message, from_email, recipient_list, reply_to=None, defer=True):
    """
    The main send email function. Use this function to send email from the
    site. All applications should use this function instead of calling
    Django's directly.
    If defer is True, the email will be sent to a Celery task to actually send
    the email. Otherwise it is sent on the caller's thread. In any event, the
    email will be logged at the DEBUG level.

    """
    # Guard against empty email addresses
    recipient_list = [dest for dest in recipient_list if dest]
    if not recipient_list:
        logging.warning("Empty recipient_list in send_mail")
        return

    logging.debug('EMAIL:\nFrom: %s\nTo: %s\nReply-To: %s\nSubject: %s\nMessage:\n%s',
        from_email, str(recipient_list), reply_to, subject, message)

    headers = {'Reply-To': reply_to} if reply_to else None
    msg_kwargs = {
        'subject': subject,
        'body': message,
        'from_email': from_email,
        'to': recipient_list,
        'headers': headers,
    }

    if defer:
        core.tasks.send_mail.delay(**msg_kwargs)
    else:
        msg = django.core.mail.EmailMessage(**msg_kwargs)
        msg.send()


def email_admins(subject, message):
    """Emails the site admins. Goes through the site send_mail function."""
    site = Site.objects.get_current()
    subject = '[%s] %s' % (site.name, subject)
    send_mail(subject,
            message,
            '%s@%s' % (settings.GPP_NO_REPLY_EMAIL, site.domain),
            [mail_tuple[1] for mail_tuple in settings.ADMINS])


def email_managers(subject, message):
    """Emails the site managers. Goes through the site send_mail function."""
    site = Site.objects.get_current()
    subject = '[%s] %s' % (site.name, subject)
    send_mail(subject,
            message,
            '%s@%s' % (settings.GPP_NO_REPLY_EMAIL, site.domain),
            [mail_tuple[1] for mail_tuple in settings.MANAGERS])


def get_full_name(user):
    """Returns the user's full name if available, otherwise falls back
    to the username."""
    full_name = user.get_full_name()
    if full_name:
        return full_name
    return user.username


BASE_YEAR = 2010

def copyright_str():
    curr_year = datetime.datetime.now().year
    if curr_year == BASE_YEAR:
        year_range = str(BASE_YEAR)
    else:
        year_range = "%d - %d" % (BASE_YEAR, curr_year)

    return 'Copyright (C) %s, SurfGuitar101.com' % year_range


IP_PAT = re.compile('(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})')

def get_ip(request):
    """Returns the IP from the request or None if it cannot be retrieved."""
    ip = request.META.get('HTTP_X_FORWARDED_FOR',
            request.META.get('REMOTE_ADDR'))

    if ip:
        match = IP_PAT.match(ip)
        ip = match.group(1) if match else None

    return ip


def get_page(qdict):
    """Attempts to retrieve the value for "page" from the given query dict and
    return it as an integer. If the key cannot be found or converted to an
    integer, 1 is returned.
    """
    n = qdict.get('page', 1)
    try:
        n = int(n)
    except ValueError:
        n = 1
    return n


def quote_message(who, message):
    """
    Builds a message reply by quoting the existing message in a
    typical email-like fashion. The quoting is compatible with Markdown.
    """
    msg = "> %s" % message.rstrip().replace('\n', '\n> ')
    if msg.endswith('\n> '):
        msg = msg[:-2]

    return "*%s wrote:*\n\n%s\n\n" % (who, msg)