from xmodule.modulestore import Location
from xmodule.modulestore.exceptions import ItemNotFoundError
from xmodule.modulestore.inheritance import own_metadata
import json
from json.encoder import JSONEncoder
import time
from contentstore.utils import get_modulestore
from models.settings import course_grading
from contentstore.utils import update_item
from xmodule.fields import Date
import re
import logging


class CourseDetails(object):
    def __init__(self, location):
        self.course_location = location    # a Location obj
        self.start_date = None  # 'start'
        self.end_date = None    # 'end'
        self.enrollment_start = None
        self.enrollment_end = None
        self.syllabus = None    # a pdf file asset
        self.overview = ""      # html to render as the overview
        self.intro_video = None    # a video pointer
        self.effort = None      # int hours/week

    @classmethod
    def fetch(cls, course_location):
        """
        Fetch the course details for the given course from persistence and return a CourseDetails model.
        """
        if not isinstance(course_location, Location):
            course_location = Location(course_location)

        course = cls(course_location)

        descriptor = get_modulestore(course_location).get_item(course_location)

        course.start_date = descriptor.start
        course.end_date = descriptor.end
        course.enrollment_start = descriptor.enrollment_start
        course.enrollment_end = descriptor.enrollment_end

        temploc = course_location._replace(category='about', name='syllabus')
        try:
            course.syllabus = get_modulestore(temploc).get_item(temploc).data
        except ItemNotFoundError:
            pass

        temploc = temploc._replace(name='overview')
        try:
            course.overview = get_modulestore(temploc).get_item(temploc).data
        except ItemNotFoundError:
            pass

        temploc = temploc._replace(name='effort')
        try:
            course.effort = get_modulestore(temploc).get_item(temploc).data
        except ItemNotFoundError:
            pass

        temploc = temploc._replace(name='video')
        try:
            raw_video = get_modulestore(temploc).get_item(temploc).data
            course.intro_video = CourseDetails.parse_video_tag(raw_video)
        except ItemNotFoundError:
            pass

        return course

    @classmethod
    def update_from_json(cls, jsondict):
        """
        Decode the json into CourseDetails and save any changed attrs to the db
        """
        ## TODO make it an error for this to be undefined & for it to not be retrievable from modulestore
        course_location = jsondict['course_location']
        ## Will probably want to cache the inflight courses because every blur generates an update
        descriptor = get_modulestore(course_location).get_item(course_location)

        dirty = False

        # In the descriptor's setter, the date is converted to JSON using Date's to_json method.
        # Calling to_json on something that is already JSON doesn't work. Since reaching directly
        # into the model is nasty, convert the JSON Date to a Python date, which is what the
        # setter expects as input.
        date = Date()

        if 'start_date' in jsondict:
            converted = date.from_json(jsondict['start_date'])
        else:
            converted = None
        if converted != descriptor.start:
            dirty = True
            descriptor.start = converted

        if 'end_date' in jsondict:
            converted = date.from_json(jsondict['end_date'])
        else:
            converted = None

        if converted != descriptor.end:
            dirty = True
            descriptor.end = converted

        if 'enrollment_start' in jsondict:
            converted = date.from_json(jsondict['enrollment_start'])
        else:
            converted = None

        if converted != descriptor.enrollment_start:
            dirty = True
            descriptor.enrollment_start = converted

        if 'enrollment_end' in jsondict:
            converted = date.from_json(jsondict['enrollment_end'])
        else:
            converted = None

        if converted != descriptor.enrollment_end:
            dirty = True
            descriptor.enrollment_end = converted

        if dirty:
            get_modulestore(course_location).update_metadata(course_location, own_metadata(descriptor))

        # NOTE: below auto writes to the db w/o verifying that any of the fields actually changed
        # to make faster, could compare against db or could have client send over a list of which fields changed.
        temploc = Location(course_location)._replace(category='about', name='syllabus')
        update_item(temploc, jsondict['syllabus'])

        temploc = temploc._replace(name='overview')
        update_item(temploc, jsondict['overview'])

        temploc = temploc._replace(name='effort')
        update_item(temploc, jsondict['effort'])

        temploc = temploc._replace(name='video')
        recomposed_video_tag = CourseDetails.recompose_video_tag(jsondict['intro_video'])
        update_item(temploc, recomposed_video_tag)

        # Could just generate and return a course obj w/o doing any db reads, but I put the reads in as a means to confirm
        # it persisted correctly
        return CourseDetails.fetch(course_location)

    @staticmethod
    def parse_video_tag(raw_video):
        """
        Because the client really only wants the author to specify the youtube key, that's all we send to and get from the client.
        The problem is that the db stores the html markup as well (which, of course, makes any sitewide changes to how we do videos
        next to impossible.)
        """
        if not raw_video:
            return None

        keystring_matcher = re.search('(?<=embed/)[a-zA-Z0-9_-]+', raw_video)
        if keystring_matcher is None:
            keystring_matcher = re.search('<?=\d+:[a-zA-Z0-9_-]+', raw_video)

        if keystring_matcher:
            return keystring_matcher.group(0)
        else:
            logging.warn("ignoring the content because it doesn't not conform to expected pattern: " + raw_video)
            return None

    @staticmethod
    def recompose_video_tag(video_key):
        # TODO should this use a mako template? Of course, my hope is that this is a short-term workaround for the db not storing
        # the right thing
        result = None
        if video_key:
            result = '<iframe width="560" height="315" src="http://www.youtube.com/embed/' + \
                video_key + '?autoplay=1&rel=0" frameborder="0" allowfullscreen=""></iframe>'
        return result


# TODO move to a more general util? Is there a better way to do the isinstance model check?
class CourseSettingsEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, CourseDetails) or isinstance(obj, course_grading.CourseGradingModel):
            return obj.__dict__
        elif isinstance(obj, Location):
            return obj.dict()
        elif isinstance(obj, time.struct_time):
            return Date().to_json(obj)
        else:
            return JSONEncoder.default(self, obj)
