import datetime
import feedparser
import itertools
import json
import logging
import random
import string
import sys
import time
import urllib
import uuid

from django.conf import settings
from django.contrib.auth import logout, authenticate, login
from django.contrib.auth.forms import PasswordResetForm
from django.contrib.auth.models import User
from django.contrib.auth.decorators import login_required
from django.core.context_processors import csrf
from django.core.mail import send_mail
from django.core.validators import validate_email, validate_slug, ValidationError
from django.db import IntegrityError
from django.http import HttpResponse, Http404
from django.shortcuts import redirect
from mitxmako.shortcuts import render_to_response, render_to_string
from bs4 import BeautifulSoup
from django.core.cache import cache

from django_future.csrf import ensure_csrf_cookie
from student.models import (Registration, UserProfile,
                            PendingNameChange, PendingEmailChange,
                            CourseEnrollment)
from xmodule.course_module import CourseDescriptor
from xmodule.modulestore.exceptions import ItemNotFoundError
from xmodule.modulestore.django import modulestore
from xmodule.modulestore.exceptions import ItemNotFoundError

from datetime import date
from collections import namedtuple
from courseware.courses import get_courses_by_university
from courseware.access import has_access

log = logging.getLogger("mitx.student")
Article = namedtuple('Article', 'title url author image deck publication publish_date')

def csrf_token(context):
    ''' A csrf token that can be included in a form.
    '''
    csrf_token = context.get('csrf_token', '')
    if csrf_token == 'NOTPROVIDED':
        return ''
    return (u'<div style="display:none"><input type="hidden"'
            ' name="csrfmiddlewaretoken" value="%s" /></div>' % (csrf_token))


def index(request, extra_context={}, user=None):
    '''
    Render the edX main page.

    extra_context is used to allow immediate display of certain modal windows, eg signup,
    as used by external_auth.
    '''
    feed_data = cache.get("students_index_rss_feed_data")
    if feed_data == None:
        if hasattr(settings, 'RSS_URL'):
            feed_data = urllib.urlopen(settings.RSS_URL).read()
        else:
            feed_data = render_to_string("feed.rss", None)
        cache.set("students_index_rss_feed_data", feed_data, settings.RSS_TIMEOUT)

    feed = feedparser.parse(feed_data)
    entries = feed['entries'][0:3]
    for entry in entries:
        soup = BeautifulSoup(entry.description)
        entry.image = soup.img['src'] if soup.img else None
        entry.summary = soup.getText()

    # The course selection work is done in courseware.courses.
    domain = settings.MITX_FEATURES.get('FORCE_UNIVERSITY_DOMAIN')	# normally False
    if domain==False:				# do explicit check, because domain=None is valid
        domain = request.META.get('HTTP_HOST')
    universities = get_courses_by_university(None,
                                             domain=domain)
    context = {'universities': universities, 'entries': entries}
    context.update(extra_context)
    if request.REQUEST.get('next', False):
        context['show_login_immediately'] = True
    return render_to_response('index.html', context)

def course_from_id(course_id):
    """Return the CourseDescriptor corresponding to this course_id"""
    course_loc = CourseDescriptor.id_to_location(course_id)
    return modulestore().get_instance(course_id, course_loc)


def press(request):
    json_articles = cache.get("student_press_json_articles")
    if json_articles == None:
        if hasattr(settings, 'RSS_URL'):
            content = urllib.urlopen(settings.PRESS_URL).read()
            json_articles = json.loads(content)
        else:
            content = open(settings.PROJECT_ROOT / "templates" / "press.json").read()
            json_articles = json.loads(content)
        cache.set("student_press_json_articles", json_articles)
    articles = [Article(**article) for article in json_articles]
    return render_to_response('static_templates/press.html', {'articles': articles})


@login_required
@ensure_csrf_cookie
def dashboard(request):
    user = request.user
    enrollments = CourseEnrollment.objects.filter(user=user)

    # Build our courses list for the user, but ignore any courses that no longer
    # exist (because the course IDs have changed). Still, we don't delete those
    # enrollments, because it could have been a data push snafu.
    courses = []
    for enrollment in enrollments:
        try:
            courses.append(course_from_id(enrollment.course_id))
        except ItemNotFoundError:
            log.error("User {0} enrolled in non-existent course {1}"
                      .format(user.username, enrollment.course_id))

    message = ""
    if not user.is_active:
        message = render_to_string('registration/activate_account_notice.html', {'email': user.email})


    # Global staff can see what courses errored on their dashboard
    staff_access = False
    errored_courses = {}
    if has_access(user, 'global', 'staff'):
        # Show any courses that errored on load
        staff_access = True
        errored_courses = modulestore().get_errored_courses()

    show_courseware_links_for = frozenset(course.id for course in courses
                                          if has_access(request.user, course, 'load'))

    context = {'courses': courses,
               'message': message,
               'staff_access': staff_access,
               'errored_courses': errored_courses,
               'show_courseware_links_for' : show_courseware_links_for}

    return render_to_response('dashboard.html', context)


def try_change_enrollment(request):
    """
    This method calls change_enrollment if the necessary POST
    parameters are present, but does not return anything. It
    simply logs the result or exception. This is usually
    called after a registration or login, as secondary action.
    It should not interrupt a successful registration or login.
    """
    if 'enrollment_action' in request.POST:
        try:
            enrollment_output = change_enrollment(request)
            # There isn't really a way to display the results to the user, so we just log it
            # We expect the enrollment to be a success, and will show up on the dashboard anyway
            log.info("Attempted to automatically enroll after login. Results: {0}".format(enrollment_output))
        except Exception, e:
            log.exception("Exception automatically enrolling after login: {0}".format(str(e)))


@login_required
def change_enrollment_view(request):
    """Delegate to change_enrollment to actually do the work."""
    return HttpResponse(json.dumps(change_enrollment(request)))



def change_enrollment(request):
    if request.method != "POST":
        raise Http404

    user = request.user
    if not user.is_authenticated():
        raise Http404

    action = request.POST.get("enrollment_action", "")

    course_id = request.POST.get("course_id", None)
    if course_id == None:
        return HttpResponse(json.dumps({'success': False,
                                        'error': 'There was an error receiving the course id.'}))

    if action == "enroll":
        # Make sure the course exists
        # We don't do this check on unenroll, or a bad course id can't be unenrolled from
        try:
            course = course_from_id(course_id)
        except ItemNotFoundError:
            log.warning("User {0} tried to enroll in non-existant course {1}"
                      .format(user.username, enrollment.course_id))
            return {'success': False, 'error': 'The course requested does not exist.'}

        if not has_access(user, course, 'enroll'):
            return {'success': False,
                    'error': 'enrollment in {} not allowed at this time'
                    .format(course.display_name)}

        enrollment, created = CourseEnrollment.objects.get_or_create(user=user, course_id=course.id)
        return {'success': True}

    elif action == "unenroll":
        try:
            enrollment = CourseEnrollment.objects.get(user=user, course_id=course_id)
            enrollment.delete()
            return {'success': True}
        except CourseEnrollment.DoesNotExist:
            return {'success': False, 'error': 'You are not enrolled for this course.'}
    else:
        return {'success': False, 'error': 'Invalid enrollment_action.'}

    return {'success': False, 'error': 'We weren\'t able to unenroll you. Please try again.'}


# Need different levels of logging
@ensure_csrf_cookie
def login_user(request, error=""):
    ''' AJAX request to log in the user. '''
    if 'email' not in request.POST or 'password' not in request.POST:
        return HttpResponse(json.dumps({'success': False,
                                        'value': 'There was an error receiving your login information. Please email us.'}))  # TODO: User error message

    email = request.POST['email']
    password = request.POST['password']
    try:
        user = User.objects.get(email=email)
    except User.DoesNotExist:
        log.warning("Login failed - Unknown user email: {0}".format(email))
        return HttpResponse(json.dumps({'success': False,
                                        'value': 'Email or password is incorrect.'}))  # TODO: User error message

    username = user.username
    user = authenticate(username=username, password=password)
    if user is None:
        log.warning("Login failed - password for {0} is invalid".format(email))
        return HttpResponse(json.dumps({'success': False,
                                        'value': 'Email or password is incorrect.'}))

    if user is not None and user.is_active:
        try:
            login(request, user)
            if request.POST.get('remember') == 'true':
                request.session.set_expiry(None)  # or change to 604800 for 7 days
                log.debug("Setting user session to never expire")
            else:
                request.session.set_expiry(0)
        except Exception as e:
            log.critical("Login failed - Could not create session. Is memcached running?")
            log.exception(e)

        log.info("Login success - {0} ({1})".format(username, email))

        try_change_enrollment(request)

        return HttpResponse(json.dumps({'success': True}))

    log.warning("Login failed - Account not active for user {0}".format(username))
    return HttpResponse(json.dumps({'success': False,
                                    'value': 'This account has not been activated. Please check your e-mail for the activation instructions.'}))


@ensure_csrf_cookie
def logout_user(request):
    ''' HTTP request to log out the user. Redirects to marketing page'''
    logout(request)
    return redirect('/')


@login_required
@ensure_csrf_cookie
def change_setting(request):
    ''' JSON call to change a profile setting: Right now, location
    '''
    # TODO (vshnayder): location is no longer used
    up = UserProfile.objects.get(user=request.user)  # request.user.profile_cache
    if 'location' in request.POST:
        up.location = request.POST['location']
    up.save()

    return HttpResponse(json.dumps({'success': True,
                                    'location': up.location, }))

def _do_create_account(post_vars):
    """
    Given cleaned post variables, create the User and UserProfile objects, as well as the
    registration for this user.

    Returns a tuple (User, UserProfile, Registration).

    Note: this function is also used for creating test users.
    """
    user = User(username=post_vars['username'],
             email=post_vars['email'],
             is_active=False)
    user.set_password(post_vars['password'])
    registration = Registration()
    # TODO: Rearrange so that if part of the process fails, the whole process fails.
    # Right now, we can have e.g. no registration e-mail sent out and a zombie account
    try:
        user.save()
    except IntegrityError:
        js = {'success': False}
        # Figure out the cause of the integrity error
        if len(User.objects.filter(username=post_vars['username'])) > 0:
            js['value'] = "An account with this username already exists."
            js['field'] = 'username'
            return HttpResponse(json.dumps(js))

        if len(User.objects.filter(email=post_vars['email'])) > 0:
            js['value'] = "An account with this e-mail already exists."
            js['field'] = 'email'
            return HttpResponse(json.dumps(js))

        raise

    registration.register(user)

    profile = UserProfile(user=user)
    profile.name = post_vars['name']
    profile.level_of_education = post_vars.get('level_of_education')
    profile.gender = post_vars.get('gender')
    profile.mailing_address = post_vars.get('mailing_address')
    profile.goals = post_vars.get('goals')

    try:
        profile.year_of_birth = int(post_vars['year_of_birth'])
    except (ValueError, KeyError):
        profile.year_of_birth = None  # If they give us garbage, just ignore it instead
                                # of asking them to put an integer.
    try:
        profile.save()
    except Exception:
        log.exception("UserProfile creation failed for user {0}.".format(user.id))
    return (user, profile, registration)


@ensure_csrf_cookie
def create_account(request, post_override=None):
    '''
    JSON call to create new edX account.
    Used by form in signup_modal.html, which is included into navigation.html
    '''
    js = {'success': False}

    post_vars = post_override if post_override else request.POST

    # if doing signup for an external authorization, then get email, password, name from the eamap
    # don't use the ones from the form, since the user could have hacked those
    DoExternalAuth = 'ExternalAuthMap' in request.session
    if DoExternalAuth:
        eamap = request.session['ExternalAuthMap']
        email = eamap.external_email
        name = eamap.external_name
        password = eamap.internal_password
        post_vars = dict(post_vars.items())
        post_vars.update(dict(email=email, name=name, password=password))
        log.debug('extauth test: post_vars = %s' % post_vars)

    # Confirm we have a properly formed request
    for a in ['username', 'email', 'password', 'name']:
        if a not in post_vars:
            js['value'] = "Error (401 {field}). E-mail us.".format(field=a)
            js['field'] = a
            return HttpResponse(json.dumps(js))

    if post_vars.get('honor_code', 'false') != u'true':
        js['value'] = "To enroll, you must follow the honor code.".format(field=a)
        js['field'] = 'honor_code'
        return HttpResponse(json.dumps(js))

    if post_vars.get('terms_of_service', 'false') != u'true':
        js['value'] = "You must accept the terms of service.".format(field=a)
        js['field'] = 'terms_of_service'
        return HttpResponse(json.dumps(js))

    # Confirm appropriate fields are there.
    # TODO: Check e-mail format is correct.
    # TODO: Confirm e-mail is not from a generic domain (mailinator, etc.)? Not sure if
    # this is a good idea
    # TODO: Check password is sane
    for a in ['username', 'email', 'name', 'password', 'terms_of_service', 'honor_code']:
        if len(post_vars[a]) < 2:
            error_str = {'username': 'Username must be minimum of two characters long.',
                         'email': 'A properly formatted e-mail is required.',
                         'name': 'Your legal name must be a minimum of two characters long.',
                         'password': 'A valid password is required.',
                         'terms_of_service': 'Accepting Terms of Service is required.',
                         'honor_code': 'Agreeing to the Honor Code is required.'}
            js['value'] = error_str[a]
            js['field'] = a
            return HttpResponse(json.dumps(js))

    try:
        validate_email(post_vars['email'])
    except ValidationError:
        js['value'] = "Valid e-mail is required.".format(field=a)
        js['field'] = 'email'
        return HttpResponse(json.dumps(js))

    try:
        validate_slug(post_vars['username'])
    except ValidationError:
        js['value'] = "Username should only consist of A-Z and 0-9.".format(field=a)
        js['field'] = 'username'
        return HttpResponse(json.dumps(js))

    # Ok, looks like everything is legit.  Create the account.
    ret = _do_create_account(post_vars)
    if isinstance(ret,HttpResponse):		# if there was an error then return that
        return ret
    (user, profile, registration) = ret

    d = {'name': post_vars['name'],
         'key': registration.activation_key,
         }

    # composes activation email
    subject = render_to_string('emails/activation_email_subject.txt', d)
    # Email subject *must not* contain newlines
    subject = ''.join(subject.splitlines())
    message = render_to_string('emails/activation_email.txt', d)

    try:
        if settings.MITX_FEATURES.get('REROUTE_ACTIVATION_EMAIL'):
            dest_addr = settings.MITX_FEATURES['REROUTE_ACTIVATION_EMAIL']
            message = ("Activation for %s (%s): %s\n" % (user, user.email, profile.name) +
                       '-' * 80 + '\n\n' + message)
            send_mail(subject, message, settings.DEFAULT_FROM_EMAIL, [dest_addr], fail_silently=False)
        elif not settings.GENERATE_RANDOM_USER_CREDENTIALS:
            res = user.email_user(subject, message, settings.DEFAULT_FROM_EMAIL)
    except:
        log.exception(sys.exc_info())
        js['value'] = 'Could not send activation e-mail.'
        return HttpResponse(json.dumps(js))

    # Immediately after a user creates an account, we log them in. They are only
    # logged in until they close the browser. They can't log in again until they click
    # the activation link from the email.
    login_user = authenticate(username=post_vars['username'], password=post_vars['password'])
    login(request, login_user)
    request.session.set_expiry(0)

    try_change_enrollment(request)

    if DoExternalAuth:
        eamap.user = login_user
        eamap.dtsignup = datetime.datetime.now()
        eamap.save()
        log.debug('Updated ExternalAuthMap for %s to be %s' % (post_vars['username'],eamap))

        if settings.MITX_FEATURES.get('BYPASS_ACTIVATION_EMAIL_FOR_EXTAUTH'):
            log.debug('bypassing activation email')
            login_user.is_active = True
            login_user.save()

    js = {'success': True}
    return HttpResponse(json.dumps(js), mimetype="application/json")


def get_random_post_override():
    """
    Return a dictionary suitable for passing to post_vars of _do_create_account or post_override
    of create_account, with random user info.
    """
    def id_generator(size=6, chars=string.ascii_uppercase + string.ascii_lowercase + string.digits):
        return ''.join(random.choice(chars) for x in range(size))

    return {'username': "random_" + id_generator(),
            'email': id_generator(size=10, chars=string.ascii_lowercase) + "_dummy_test@mitx.mit.edu",
            'password': id_generator(),
            'name': (id_generator(size=5, chars=string.ascii_lowercase) + " " +
                     id_generator(size=7, chars=string.ascii_lowercase)),
                     'honor_code': u'true',
                     'terms_of_service': u'true', }


def create_random_account(create_account_function):
    def inner_create_random_account(request):
        return create_account_function(request, post_override=get_random_post_override())

    return inner_create_random_account

# TODO (vshnayder): do we need GENERATE_RANDOM_USER_CREDENTIALS for anything?
if settings.GENERATE_RANDOM_USER_CREDENTIALS:
    create_account = create_random_account(create_account)


@ensure_csrf_cookie
def activate_account(request, key):
    ''' When link in activation e-mail is clicked
    '''
    r = Registration.objects.filter(activation_key=key)
    if len(r) == 1:
        user_logged_in = request.user.is_authenticated()
        already_active = True
        if not r[0].user.is_active:
            r[0].activate()
            already_active = False
        resp = render_to_response("registration/activation_complete.html", {'user_logged_in': user_logged_in, 'already_active': already_active})
        return resp
    if len(r) == 0:
        return render_to_response("registration/activation_invalid.html", {'csrf': csrf(request)['csrf_token']})
    return HttpResponse("Unknown error. Please e-mail us to let us know how it happened.")


@ensure_csrf_cookie
def password_reset(request):
    ''' Attempts to send a password reset e-mail. '''
    if request.method != "POST":
        raise Http404
    form = PasswordResetForm(request.POST)
    if form.is_valid():
        form.save(use_https = request.is_secure(),
                  from_email = settings.DEFAULT_FROM_EMAIL,
                  request = request,
                  domain_override = request.get_host())
        return HttpResponse(json.dumps({'success':True,
                                        'value': render_to_string('registration/password_reset_done.html', {})}))
    else:
        return HttpResponse(json.dumps({'success': False,
                                        'error': 'Invalid e-mail'}))


@ensure_csrf_cookie
def reactivation_email(request):
    ''' Send an e-mail to reactivate a deactivated account, or to
    resend an activation e-mail. Untested. '''
    email = request.POST['email']
    try:
        user = User.objects.get(email='email')
    except User.DoesNotExist:
        return HttpResponse(json.dumps({'success': False,
                                        'error': 'No inactive user with this e-mail exists'}))

    if user.is_active:
        return HttpResponse(json.dumps({'success': False,
                                        'error': 'User is already active'}))

    reg = Registration.objects.get(user=user)
    reg.register(user)

    d = {'name': UserProfile.get(user=user).name,
       'key': r.activation_key}

    subject = render_to_string('reactivation_email_subject.txt', d)
    subject = ''.join(subject.splitlines())
    message = render_to_string('reactivation_email.txt', d)

    res = user.email_user(subject, message, settings.DEFAULT_FROM_EMAIL)

    return HttpResponse(json.dumps({'success': True}))


@ensure_csrf_cookie
def change_email_request(request):
    ''' AJAX call from the profile page. User wants a new e-mail.
    '''
    ## Make sure it checks for existing e-mail conflicts
    if not request.user.is_authenticated:
        raise Http404

    user = request.user

    if not user.check_password(request.POST['password']):
        return HttpResponse(json.dumps({'success': False,
                                        'error': 'Invalid password'}))

    new_email = request.POST['new_email']
    try:
        validate_email(new_email)
    except ValidationError:
        return HttpResponse(json.dumps({'success': False,
                                        'error': 'Valid e-mail address required.'}))

    if len(User.objects.filter(email=new_email)) != 0:
        ## CRITICAL TODO: Handle case sensitivity for e-mails
        return HttpResponse(json.dumps({'success': False,
                                        'error': 'An account with this e-mail already exists.'}))

    pec_list = PendingEmailChange.objects.filter(user=request.user)
    if len(pec_list) == 0:
        pec = PendingEmailChange()
        pec.user = user
    else:
        pec = pec_list[0]

    pec.new_email = request.POST['new_email']
    pec.activation_key = uuid.uuid4().hex
    pec.save()

    if pec.new_email == user.email:
        pec.delete()
        return HttpResponse(json.dumps({'success': False,
                                        'error': 'Old email is the same as the new email.'}))

    d = {'key': pec.activation_key,
         'old_email': user.email,
         'new_email': pec.new_email}

    subject = render_to_string('emails/email_change_subject.txt', d)
    subject = ''.join(subject.splitlines())
    message = render_to_string('emails/email_change.txt', d)

    res = send_mail(subject, message, settings.DEFAULT_FROM_EMAIL, [pec.new_email])

    return HttpResponse(json.dumps({'success': True}))


@ensure_csrf_cookie
def confirm_email_change(request, key):
    ''' User requested a new e-mail. This is called when the activation
    link is clicked. We confirm with the old e-mail, and update
    '''
    try:
        pec = PendingEmailChange.objects.get(activation_key=key)
    except PendingEmailChange.DoesNotExist:
        return render_to_response("invalid_email_key.html", {})

    user = pec.user
    d = {'old_email': user.email,
         'new_email': pec.new_email}

    if len(User.objects.filter(email=pec.new_email)) != 0:
        return render_to_response("email_exists.html", d)

    subject = render_to_string('emails/email_change_subject.txt', d)
    subject = ''.join(subject.splitlines())
    message = render_to_string('emails/confirm_email_change.txt', d)
    up = UserProfile.objects.get(user=user)
    meta = up.get_meta()
    if 'old_emails' not in meta:
        meta['old_emails'] = []
    meta['old_emails'].append([user.email, datetime.datetime.now().isoformat()])
    up.set_meta(meta)
    up.save()
    user.email = pec.new_email
    user.save()
    pec.delete()
    user.email_user(subject, message, settings.DEFAULT_FROM_EMAIL)

    return render_to_response("email_change_successful.html", d)


@ensure_csrf_cookie
def change_name_request(request):
    ''' Log a request for a new name. '''
    if not request.user.is_authenticated:
        raise Http404

    try:
        pnc = PendingNameChange.objects.get(user=request.user)
    except PendingNameChange.DoesNotExist:
        pnc = PendingNameChange()
    pnc.user = request.user
    pnc.new_name = request.POST['new_name']
    pnc.rationale = request.POST['rationale']
    if len(pnc.new_name) < 2:
        return HttpResponse(json.dumps({'success': False, 'error': 'Name required'}))
    if len(pnc.rationale) < 2:
        return HttpResponse(json.dumps({'success': False, 'error': 'Rationale required'}))
    pnc.save()
    return HttpResponse(json.dumps({'success': True}))


@ensure_csrf_cookie
def pending_name_changes(request):
    ''' Web page which allows staff to approve or reject name changes. '''
    if not request.user.is_staff:
        raise Http404

    changes = list(PendingNameChange.objects.all())
    js = {'students': [{'new_name': c.new_name,
                        'rationale':c.rationale,
                        'old_name':UserProfile.objects.get(user=c.user).name,
                        'email':c.user.email,
                        'uid':c.user.id,
                        'cid':c.id} for c in changes]}
    return render_to_response('name_changes.html', js)


@ensure_csrf_cookie
def reject_name_change(request):
    ''' JSON: Name change process. Course staff clicks 'reject' on a given name change '''
    if not request.user.is_staff:
        raise Http404

    try:
        pnc = PendingNameChange.objects.get(id=int(request.POST['id']))
    except PendingNameChange.DoesNotExist:
        return HttpResponse(json.dumps({'success': False, 'error': 'Invalid ID'}))

    pnc.delete()
    return HttpResponse(json.dumps({'success': True}))


@ensure_csrf_cookie
def accept_name_change(request):
    ''' JSON: Name change process. Course staff clicks 'accept' on a given name change '''
    if not request.user.is_staff:
        raise Http404

    try:
        pnc = PendingNameChange.objects.get(id=int(request.POST['id']))
    except PendingNameChange.DoesNotExist:
        return HttpResponse(json.dumps({'success': False, 'error': 'Invalid ID'}))

    u = pnc.user
    up = UserProfile.objects.get(user=u)

    # Save old name
    meta = up.get_meta()
    if 'old_names' not in meta:
        meta['old_names'] = []
    meta['old_names'].append([up.name, pnc.rationale, datetime.datetime.now().isoformat()])
    up.set_meta(meta)

    up.name = pnc.new_name
    up.save()
    pnc.delete()

    return HttpResponse(json.dumps({'success': True}))
