"""
Views for user API
"""

from django.shortcuts import redirect
from django.utils import dateparse

from rest_framework import generics, views
from rest_framework.decorators import api_view
from rest_framework.response import Response

from opaque_keys.edx.keys import UsageKey
from opaque_keys import InvalidKeyError

from courseware.access import is_mobile_available_for_user
from courseware.model_data import FieldDataCache
from courseware.module_render import get_module_for_descriptor
from courseware.views import get_current_child, save_positions_recursively_up
from student.models import CourseEnrollment, User

from xblock.fields import Scope
from xblock.runtime import KeyValueStore
from xmodule.modulestore.django import modulestore
from xmodule.modulestore.exceptions import ItemNotFoundError

from .serializers import CourseEnrollmentSerializer, UserSerializer
from .. import errors
from ..utils import mobile_view, mobile_course_access


@mobile_view(is_user=True)
class UserDetail(generics.RetrieveAPIView):
    """
    **Use Case**

        Get information about the specified user and access other resources
        the user has permissions for.

        Users are redirected to this endpoint after they sign in.

        You can use the **course_enrollments** value in the response to get a
        list of courses the user is enrolled in.

    **Example Request**

        GET /api/mobile/v0.5/users/{username}

    **Response Values**

        If the request is successful, the request returns an HTTP 200 "OK" response.

        The HTTP 200 response has the following values.

        * course_enrollments: The URI to list the courses the currently signed
          in user is enrolled in.
        * email: The email address of the currently signed in user.
        * id: The ID of the user.
        * name: The full name of the currently signed in user.
        * username: The username of the currently signed in user.
    """
    queryset = (
        User.objects.all()
        .select_related('profile', 'course_enrollments')
    )
    serializer_class = UserSerializer
    lookup_field = 'username'


@mobile_view(is_user=True)
class UserCourseStatus(views.APIView):
    """
    **Use Cases**

        Get or update the ID of the module that the specified user last
        visited in the specified course.

    **Example Requests**

        GET /api/mobile/v0.5/users/{username}/course_status_info/{course_id}

        PATCH /api/mobile/v0.5/users/{username}/course_status_info/{course_id}

        **PATCH Parameters**

          The body of the PATCH request can include the following parameters.

          * last_visited_module_id={module_id}
          * modification_date={date}

            The modification_date parameter is optional. If it is present, the
            update will only take effect if the modification_date in the
            request is later than the modification_date saved on the server.

    **Response Values**

        If the request is successful, the request returns an HTTP 200 "OK" response.

        The HTTP 200 response has the following values.

        * last_visited_module_id: The ID of the last module that the user
          visited in the course.
        * last_visited_module_path: The ID of the modules in the path from the
          last visited module to the course module.
    """

    http_method_names = ["get", "patch"]

    def _last_visited_module_path(self, request, course):
        """
        Returns the path from the last module visited by the current user in the given course up to
        the course module. If there is no such visit, the first item deep enough down the course
        tree is used.
        """
        field_data_cache = FieldDataCache.cache_for_descriptor_descendents(
            course.id, request.user, course, depth=2)

        course_module = get_module_for_descriptor(
            request.user, request, course, field_data_cache, course.id, course=course
        )

        path = [course_module]
        chapter = get_current_child(course_module, min_depth=2)
        if chapter is not None:
            path.append(chapter)
            section = get_current_child(chapter, min_depth=1)
            if section is not None:
                path.append(section)

        path.reverse()
        return path

    def _get_course_info(self, request, course):
        """
        Returns the course status
        """
        path = self._last_visited_module_path(request, course)
        path_ids = [unicode(module.location) for module in path]
        return Response({
            "last_visited_module_id": path_ids[0],
            "last_visited_module_path": path_ids,
        })

    def _update_last_visited_module_id(self, request, course, module_key, modification_date):
        """
        Saves the module id if the found modification_date is less recent than the passed modification date
        """
        field_data_cache = FieldDataCache.cache_for_descriptor_descendents(
            course.id, request.user, course, depth=2)
        try:
            module_descriptor = modulestore().get_item(module_key)
        except ItemNotFoundError:
            return Response(errors.ERROR_INVALID_MODULE_ID, status=400)
        module = get_module_for_descriptor(
            request.user, request, module_descriptor, field_data_cache, course.id, course=course
        )

        if modification_date:
            key = KeyValueStore.Key(
                scope=Scope.user_state,
                user_id=request.user.id,
                block_scope_id=course.location,
                field_name='position'
            )
            original_store_date = field_data_cache.last_modified(key)
            if original_store_date is not None and modification_date < original_store_date:
                # old modification date so skip update
                return self._get_course_info(request, course)

        save_positions_recursively_up(request.user, request, field_data_cache, module, course=course)
        return self._get_course_info(request, course)

    @mobile_course_access(depth=2)
    def get(self, request, course, *args, **kwargs):  # pylint: disable=unused-argument
        """
        Get the ID of the module that the specified user last visited in the specified course.
        """

        return self._get_course_info(request, course)

    @mobile_course_access(depth=2)
    def patch(self, request, course, *args, **kwargs):  # pylint: disable=unused-argument
        """
        Update the ID of the module that the specified user last visited in the specified course.
        """
        module_id = request.DATA.get("last_visited_module_id")
        modification_date_string = request.DATA.get("modification_date")
        modification_date = None
        if modification_date_string:
            modification_date = dateparse.parse_datetime(modification_date_string)
            if not modification_date or not modification_date.tzinfo:
                return Response(errors.ERROR_INVALID_MODIFICATION_DATE, status=400)

        if module_id:
            try:
                module_key = UsageKey.from_string(module_id)
            except InvalidKeyError:
                return Response(errors.ERROR_INVALID_MODULE_ID, status=400)

            return self._update_last_visited_module_id(request, course, module_key, modification_date)
        else:
            # The arguments are optional, so if there's no argument just succeed
            return self._get_course_info(request, course)


@mobile_view(is_user=True)
class UserCourseEnrollmentsList(generics.ListAPIView):
    """
    **Use Case**

        Get information about the courses that the currently signed in user is
        enrolled in.

    **Example Request**

        GET /api/mobile/v0.5/users/{username}/course_enrollments/

    **Response Values**

        If the request for information about the user is successful, the
        request returns an HTTP 200 "OK" response.

        The HTTP 200 response has the following values.

        * certificate: Information about the user's earned certificate in the
          course.
        * course: A collection of the following data about the course.

          * course_handouts: The URI to get data for course handouts.
          * course_image: The path to the course image.
          * course_updates: The URI to get data for course updates.
          * end: The end date of the course.
          * id: The unique ID of the course.
          * latest_updates: Reserved for future use.
          * name: The name of the course.
          * number: The course number.
          * org: The organization that created the course.
          * start: The date and time when the course starts.
          * subscription_id: A unique "clean" (alphanumeric with '_') ID of
            the course.
          * video_outline: The URI to get the list of all videos that the user
            can access in the course.

        * created: The date the course was created.
        * is_active: Whether the course is currently active. Possible values
          are true or false.
        * mode: The type of certificate registration for this course (honor or
          certified).
        * url: URL to the downloadable version of the certificate, if exists.
    """
    queryset = CourseEnrollment.objects.all()
    serializer_class = CourseEnrollmentSerializer
    lookup_field = 'username'

    def get_queryset(self):
        enrollments = self.queryset.filter(
            user__username=self.kwargs['username'],
            is_active=True
        ).order_by('created').reverse()
        return [
            enrollment for enrollment in enrollments
            if enrollment.course_overview and
            is_mobile_available_for_user(self.request.user, enrollment.course_overview)
        ]


@api_view(["GET"])
@mobile_view()
def my_user_info(request):
    """
    Redirect to the currently-logged-in user's info page
    """
    return redirect("user-detail", username=request.user.username)
