import logging
import os
import re
from six.moves.urllib.request import urlopen


from flask import Flask
from flask_ask import Ask, request, session, question, statement


app = Flask(__name__)
ask = Ask(app, "/")
logging.getLogger('flask_ask').setLevel(logging.DEBUG)


# URL prefix to download history content from Wikipedia.
URL_PREFIX = 'https://en.wikipedia.org/w/api.php?action=query&prop=extracts' + \
    '&format=json&explaintext=&exsectionformat=plain&redirects=&titles='

# Constant defining number of events to be read at one time.
PAGINATION_SIZE = 3

# Length of the delimiter between individual events.
DELIMITER_SIZE = 2

# Size of events from Wikipedia response.
SIZE_OF_EVENTS = 10

# Constant defining session attribute key for the event index
SESSION_INDEX = 'index'

# Constant defining session attribute key for the event text key for date of events.
SESSION_TEXT = 'text'


@ask.launch
def launch():
    speech_output = 'History buff. What day do you want events for?'
    reprompt_text = "With History Buff, you can get historical events for any day of the year. " + \
                    "For example, you could say today, or August thirtieth. " + \
                    "Now, which day do you want?"
    return question(speech_output).reprompt(reprompt_text)


@ask.intent('GetFirstEventIntent', convert={ 'day': 'date' })
def get_first_event(day):
    month_name = day.strftime('%B')
    day_number = day.day
    events = _get_json_events_from_wikipedia(month_name, day_number)
    if not events:
        speech_output = "There is a problem connecting to Wikipedia at this time. Please try again later."
        return statement('<speak>{}</speak>'.format(speech_output))
    else:
        card_title = "Events on {} {}".format(month_name, day_number)
        speech_output = "<p>For {} {}</p>".format(month_name, day_number)
        card_output = ""
        for i in range(PAGINATION_SIZE):
            speech_output += "<p>{}</p>".format(events[i])
            card_output += "{}\n".format(events[i])
        speech_output += " Wanna go deeper into history?"
        card_output += " Wanna go deeper into history?"
        reprompt_text = "With History Buff, you can get historical events for any day of the year. " + \
                        "For example, you could say today, or August thirtieth. " + \
                        "Now, which day do you want?"
        session.attributes[SESSION_INDEX] = PAGINATION_SIZE
        session.attributes[SESSION_TEXT] = events
        speech_output = '<speak>{}</speak>'.format(speech_output)
        return question(speech_output).reprompt(reprompt_text).simple_card(card_title, card_output)


@ask.intent('GetNextEventIntent')
def get_next_event():
    events = session.attributes[SESSION_TEXT]
    index = session.attributes[SESSION_INDEX]
    card_title = "More events on this day in history"
    speech_output = ""
    card_output = ""
    i = 0
    while i < PAGINATION_SIZE and index < len(events):
        speech_output += "<p>{}</p>".format(events[index])
        card_output += "{}\n".format(events[index])
        i += 1
        index += 1
    speech_output += " Wanna go deeper into history?"
    reprompt_text = "Do you want to know more about what happened on this date?"
    session.attributes[SESSION_INDEX] = index
    speech_output = '<speak>{}</speak>'.format(speech_output)
    return question(speech_output).reprompt(reprompt_text).simple_card(card_title, card_output)


@ask.intent('AMAZON.StopIntent')
def stop():
    return statement("Goodbye")


@ask.intent('AMAZON.CancelIntent')
def cancel():
    return statement("Goodbye")


@ask.session_ended
def session_ended():
    return "{}", 200


def _get_json_events_from_wikipedia(month, date):
    url = "{}{}_{}".format(URL_PREFIX, month, date)
    data = urlopen(url).read().decode('utf-8')
    return _parse_json(data)


def _parse_json(text):
    events = []
    try:
        slice_start = text.index("\\nEvents\\n") + SIZE_OF_EVENTS
        slice_end = text.index("\\n\\n\\nBirths")
        text = text[slice_start:slice_end];
    except ValueError:
        return events
    start_index = end_index = 0
    done = False
    while not done:
        try:
            end_index = text.index('\\n', start_index + DELIMITER_SIZE)
            event_text = text[start_index:end_index]
            start_index = end_index + 2
        except ValueError:
            event_text = text[start_index:]
            done = True
        # replace dashes returned in text from Wikipedia's API
        event_text = event_text.replace('\\u2013', '')
        # add comma after year so Alexa pauses before continuing with the sentence
        event_text = re.sub('^\d+', r'\g<0>,', event_text)
        events.append(event_text)
    events.reverse()
    return events


if __name__ == '__main__':
    if 'ASK_VERIFY_REQUESTS' in os.environ:
        verify = str(os.environ.get('ASK_VERIFY_REQUESTS', '')).lower()
        if verify == 'false':
            app.config['ASK_VERIFY_REQUESTS'] = False
    app.run(debug=True)