"""
Views for the course_mode module
"""

import decimal
from django.core.urlresolvers import reverse
from django.conf import settings
from django.http import HttpResponse, HttpResponseBadRequest
from django.shortcuts import redirect
from django.views.generic.base import View
from django.utils.translation import ugettext as _
from django.contrib.auth.decorators import login_required
from django.utils.decorators import method_decorator

from edxmako.shortcuts import render_to_response

from course_modes.models import CourseMode
from courseware.access import has_access
from student.models import CourseEnrollment
from opaque_keys.edx.locations import SlashSeparatedCourseKey
from opaque_keys.edx.keys import CourseKey
from util.db import commit_on_success_with_read_committed
from xmodule.modulestore.django import modulestore


class ChooseModeView(View):
    """View used when the user is asked to pick a mode.

    When a get request is used, shows the selection page.

    When a post request is used, assumes that it is a form submission
    from the selection page, parses the response, and then sends user
    to the next step in the flow.

    """

    @method_decorator(login_required)
    def get(self, request, course_id, error=None):
        """Displays the course mode choice page.

        Args:
            request (`Request`): The Django Request object.
            course_id (unicode): The slash-separated course key.

        Keyword Args:
            error (unicode): If provided, display this error message
                on the page.

        Returns:
            Response

        """
        course_key = CourseKey.from_string(course_id)

        upgrade = request.GET.get('upgrade', False)
        request.session['attempting_upgrade'] = upgrade

        # TODO (ECOM-188): Once the A/B test of decoupled/verified flows
        # completes, we can remove this flag.
        # The A/B test framework will reload the page with the ?separate-verified GET param
        # set if the user is in the experimental condition.  We then store this flag
        # in a session variable so downstream views can check it.
        if request.GET.get('separate-verified', False):
            request.session['separate-verified'] = True
        elif request.GET.get('disable-separate-verified', False) and 'separate-verified' in request.session:
            del request.session['separate-verified']

        enrollment_mode, is_active = CourseEnrollment.enrollment_mode_for_user(request.user, course_key)
        modes = CourseMode.modes_for_course_dict(course_key)

        # We assume that, if 'professional' is one of the modes, it is the *only* mode.
        # If we offer more modes alongside 'professional' in the future, this will need to route
        # to the usual "choose your track" page.
        has_enrolled_professional = (enrollment_mode == "professional" and is_active)
        if "professional" in modes and not has_enrolled_professional:
            # TODO (ECOM-188): Once the A/B test of separating verification / payment completes,
            # we can remove the check for the session variable.
            if settings.FEATURES.get('SEPARATE_VERIFICATION_FROM_PAYMENT') and request.session.get('separate-verified', False):
                return redirect(
                    reverse(
                        'verify_student_start_flow',
                        kwargs={'course_id': unicode(course_key)}
                    )
                )
            else:
                return redirect(
                    reverse(
                        'verify_student_show_requirements',
                        kwargs={'course_id': unicode(course_key)}
                    )
                )

        # If there isn't a verified mode available, then there's nothing
        # to do on this page.  The user has almost certainly been auto-registered
        # in the "honor" track by this point, so we send the user
        # to the dashboard.
        if not CourseMode.has_verified_mode(modes):
            return redirect(reverse('dashboard'))

        # If a user has already paid, redirect them to the dashboard.
        if is_active and enrollment_mode in CourseMode.VERIFIED_MODES:
            return redirect(reverse('dashboard'))

        donation_for_course = request.session.get("donation_for_course", {})
        chosen_price = donation_for_course.get(unicode(course_key), None)

        course = modulestore().get_course(course_key)
        context = {
            "course_modes_choose_url": reverse("course_modes_choose", kwargs={'course_id': course_key.to_deprecated_string()}),
            "modes": modes,
            "course_name": course.display_name_with_default,
            "course_org": course.display_org_with_default,
            "course_num": course.display_number_with_default,
            "chosen_price": chosen_price,
            "error": error,
            "upgrade": upgrade,
            "can_audit": "audit" in modes,
            "responsive": True
        }
        if "verified" in modes:
            context["suggested_prices"] = [
                decimal.Decimal(x.strip())
                for x in modes["verified"].suggested_prices.split(",")
                if x.strip()
            ]
            context["currency"] = modes["verified"].currency.upper()
            context["min_price"] = modes["verified"].min_price
            context["verified_name"] = modes["verified"].name
            context["verified_description"] = modes["verified"].description

        return render_to_response("course_modes/choose.html", context)

    @method_decorator(login_required)
    @method_decorator(commit_on_success_with_read_committed)
    def post(self, request, course_id):
        """Takes the form submission from the page and parses it.

        Args:
            request (`Request`): The Django Request object.
            course_id (unicode): The slash-separated course key.

        Returns:
            Status code 400 when the requested mode is unsupported. When the honor mode
            is selected, redirects to the dashboard. When the verified mode is selected,
            returns error messages if the indicated contribution amount is invalid or
            below the minimum, otherwise redirects to the verification flow.

        """
        course_key = SlashSeparatedCourseKey.from_deprecated_string(course_id)
        user = request.user

        # This is a bit redundant with logic in student.views.change_enrollment,
        # but I don't really have the time to refactor it more nicely and test.
        course = modulestore().get_course(course_key)
        if not has_access(user, 'enroll', course):
            error_msg = _("Enrollment is closed")
            return self.get(request, course_id, error=error_msg)

        upgrade = request.GET.get('upgrade', False)

        requested_mode = self._get_requested_mode(request.POST)

        allowed_modes = CourseMode.modes_for_course_dict(course_key)
        if requested_mode not in allowed_modes:
            return HttpResponseBadRequest(_("Enrollment mode not supported"))

        if requested_mode == 'honor':
            # The user will have already been enrolled in the honor mode at this
            # point, so we just redirect them to the dashboard, thereby avoiding
            # hitting the database a second time attempting to enroll them.
            return redirect(reverse('dashboard'))

        mode_info = allowed_modes[requested_mode]

        if requested_mode == 'verified':
            amount = request.POST.get("contribution") or \
                request.POST.get("contribution-other-amt") or 0

            try:
                # Validate the amount passed in and force it into two digits
                amount_value = decimal.Decimal(amount).quantize(decimal.Decimal('.01'), rounding=decimal.ROUND_DOWN)
            except decimal.InvalidOperation:
                error_msg = _("Invalid amount selected.")
                return self.get(request, course_id, error=error_msg)

            # Check for minimum pricing
            if amount_value < mode_info.min_price:
                error_msg = _("No selected price or selected price is too low.")
                return self.get(request, course_id, error=error_msg)

            donation_for_course = request.session.get("donation_for_course", {})
            donation_for_course[unicode(course_key)] = amount_value
            request.session["donation_for_course"] = donation_for_course

            # TODO (ECOM-188): Once the A/B test of separate verification flow completes,
            # we can remove the check for the session variable.
            if settings.FEATURES.get('SEPARATE_VERIFICATION_FROM_PAYMENT') and request.session.get('separate-verified', False):
                return redirect(
                    reverse(
                        'verify_student_start_flow',
                        kwargs={'course_id': unicode(course_key)}
                    )
                )
            else:
                return redirect(
                    reverse(
                        'verify_student_show_requirements',
                        kwargs={'course_id': unicode(course_key)}
                    ) + "?upgrade={}".format(upgrade)
                )

    def _get_requested_mode(self, request_dict):
        """Get the user's requested mode

        Args:
            request_dict (`QueryDict`): A dictionary-like object containing all given HTTP POST parameters.

        Returns:
            The course mode slug corresponding to the choice in the POST parameters,
            None if the choice in the POST parameters is missing or is an unsupported mode.

        """
        if 'verified_mode' in request_dict:
            return 'verified'
        if 'honor_mode' in request_dict:
            return 'honor'
        else:
            return None


def create_mode(request, course_id):
    """Add a mode to the course corresponding to the given course ID.

    Only available when settings.FEATURES['MODE_CREATION_FOR_TESTING'] is True.

    Attempts to use the following querystring parameters from the request:
        `mode_slug` (str): The mode to add, either 'honor', 'verified', or 'professional'
        `mode_display_name` (str): Describes the new course mode
        `min_price` (int): The minimum price a user must pay to enroll in the new course mode
        `suggested_prices` (str): Comma-separated prices to suggest to the user.
        `currency` (str): The currency in which to list prices.

    By default, this endpoint will create an 'honor' mode for the given course with display name
    'Honor Code', a minimum price of 0, no suggested prices, and using USD as the currency.

    Args:
        request (`Request`): The Django Request object.
        course_id (unicode): The slash-separated course key.

    Returns:
        Response
    """
    PARAMETERS = {
        'mode_slug': u'honor',
        'mode_display_name': u'Honor Code Certificate',
        'min_price': 0,
        'suggested_prices': u'',
        'currency': u'usd',
    }

    # Try pulling querystring parameters out of the request
    for parameter, default in PARAMETERS.iteritems():
        PARAMETERS[parameter] = request.GET.get(parameter, default)

    # Attempt to create the new mode for the given course
    course_key = CourseKey.from_string(course_id)
    CourseMode.objects.get_or_create(course_id=course_key, **PARAMETERS)

    # Return a success message and a 200 response
    return HttpResponse("Mode '{mode_slug}' created for course with ID '{course_id}'.".format(
        mode_slug=PARAMETERS['mode_slug'],
        course_id=course_id
    ))
