"""
Views related to course tabs
"""
from access import has_access
from util.json_request import expect_json

from django.http import HttpResponse, HttpResponseBadRequest
from django.contrib.auth.decorators import login_required
from django.core.exceptions import PermissionDenied
from django_future.csrf import ensure_csrf_cookie
from mitxmako.shortcuts import render_to_response
from xmodule.modulestore import Location
from xmodule.modulestore.inheritance import own_metadata
from xmodule.modulestore.django import modulestore

from ..utils import get_course_for_item, get_modulestore
from .access import get_location_and_verify_access


__all__ = ['edit_tabs', 'reorder_static_tabs', 'static_pages']


def initialize_course_tabs(course):
    """
    set up the default tabs
    I've added this because when we add static tabs, the LMS either expects a None for the tabs list or
    at least a list populated with the minimal times
    @TODO: I don't like the fact that the presentation tier is away of these data related constraints, let's find a better
    place for this. Also rather than using a simple list of dictionaries a nice class model would be helpful here
    """

    # This logic is repeated in xmodule/modulestore/tests/factories.py
    # so if you change anything here, you need to also change it there.
    course.tabs = [{"type": "courseware"},
                   {"type": "course_info", "name": "Course Info"},
                   {"type": "discussion", "name": "Discussion"},
                   {"type": "wiki", "name": "Wiki"},
                   {"type": "progress", "name": "Progress"}]

    modulestore('direct').update_metadata(course.location.url(), own_metadata(course))


@login_required
@expect_json
def reorder_static_tabs(request):
    "Order the static tabs in the requested order"
    tabs = request.POST['tabs']
    course = get_course_for_item(tabs[0])

    if not has_access(request.user, course.location):
        raise PermissionDenied()

    # get list of existing static tabs in course
    # make sure they are the same lengths (i.e. the number of passed in tabs equals the number
    # that we know about) otherwise we can drop some!

    existing_static_tabs = [t for t in course.tabs if t['type'] == 'static_tab']
    if len(existing_static_tabs) != len(tabs):
        return HttpResponseBadRequest()

    # load all reference tabs, return BadRequest if we can't find any of them
    tab_items = []
    for tab in tabs:
        item = modulestore('direct').get_item(Location(tab))
        if item is None:
            return HttpResponseBadRequest()

        tab_items.append(item)

    # now just go through the existing course_tabs and re-order the static tabs
    reordered_tabs = []
    static_tab_idx = 0
    for tab in course.tabs:
        if tab['type'] == 'static_tab':
            reordered_tabs.append({'type': 'static_tab',
                                   'name': tab_items[static_tab_idx].display_name,
                                   'url_slug': tab_items[static_tab_idx].location.name})
            static_tab_idx += 1
        else:
            reordered_tabs.append(tab)

    # OK, re-assemble the static tabs in the new order
    course.tabs = reordered_tabs
    # Save the data that we've just changed to the underlying
    # MongoKeyValueStore before we update the mongo datastore.
    course.save()
    modulestore('direct').update_metadata(course.location, own_metadata(course))
    # TODO: above two lines are used for the primitive-save case. Maybe factor them out?
    return HttpResponse()


@login_required
@ensure_csrf_cookie
def edit_tabs(request, org, course, coursename):
    "Edit tabs"
    location = ['i4x', org, course, 'course', coursename]
    store = get_modulestore(location)
    course_item = store.get_item(location)

    # check that logged in user has permissions to this item
    if not has_access(request.user, location):
        raise PermissionDenied()

    # see tabs have been uninitialized (e.g. supporing courses created before tab support in studio)
    if course_item.tabs is None or len(course_item.tabs) == 0:
        initialize_course_tabs(course_item)

    # first get all static tabs from the tabs list
    # we do this because this is also the order in which items are displayed in the LMS
    static_tabs_refs = [t for t in course_item.tabs if t['type'] == 'static_tab']

    static_tabs = []
    for static_tab_ref in static_tabs_refs:
        static_tab_loc = Location(location)._replace(category='static_tab', name=static_tab_ref['url_slug'])
        static_tabs.append(modulestore('direct').get_item(static_tab_loc))

    components = [
        static_tab.location.url()
        for static_tab
        in static_tabs
    ]

    return render_to_response('edit-tabs.html', {
        'context_course': course_item,
        'components': components
    })


@login_required
@ensure_csrf_cookie
def static_pages(request, org, course, coursename):
    "Static pages view"

    location = get_location_and_verify_access(request, org, course, coursename)

    course = modulestore().get_item(location)

    return render_to_response('static-pages.html', {
        'context_course': course,
    })


# "primitive" tab edit functions driven by the command line.
# These should be replaced/deleted by a more capable GUI someday.
# Note that the command line UI identifies the tabs with 1-based
# indexing, but this implementation code is standard 0-based.

def validate_args(num, tab_type):
    "Throws for the disallowed cases."
    if num <= 1:
        raise ValueError('Tabs 1 and 2 cannot be edited')
    if tab_type == 'static_tab':
        raise ValueError('Tabs of type static_tab cannot be edited here (use Studio)')


def primitive_delete(course, num):
    "Deletes the given tab number (0 based)."
    tabs = course.tabs
    validate_args(num, tabs[num].get('type', ''))
    del tabs[num]
    # Note for future implementations: if you delete a static_tab, then Chris Dodge
    # points out that there's other stuff to delete beyond this element.
    # This code happens to not delete static_tab so it doesn't come up.
    primitive_save(course)


def primitive_insert(course, num, tab_type, name):
    "Inserts a new tab at the given number (0 based)."
    validate_args(num, tab_type)
    new_tab = {u'type': unicode(tab_type), u'name': unicode(name)}
    tabs = course.tabs
    tabs.insert(num, new_tab)
    primitive_save(course)


def primitive_save(course):
    "Saves the course back to modulestore."
    # This code copied from reorder_static_tabs above
    course.save()
    modulestore('direct').update_metadata(course.location, own_metadata(course))
