""" Models for the history. This history should be able to generate history
entries, which looks like human-based browsing, according to a dedicated user
interests, keywords...
"""

from collections import namedtuple
import random
from math import floor
from xml.etree import ElementTree as ET
from datetime import datetime
from django.db import models
from django.core.exceptions import ValidationError
import profiles.models as profiles
from crawl import crawl
from pinocchio.settings import HISTORY_MIN
from .tor_runner import TorInstance


class InvalidXml(Exception):
    def __init__(self, what='unexpected XML data.'):
        super().__init__()
        self.what = what

    def __str__(self):
        return "Invalid XML: " + self.what


class HistoryEntry(models.Model):
    """ A history entry, aka a url, and a timestamp.
    """
    search = models.URLField(help_text="The url to be searched")
    timestamp = models.DateTimeField()
    history = models.ForeignKey(
        'History',
        on_delete=models.CASCADE
    )

    def __str__(self):
        """ Returns the string representation of a history entry.
        """
        return "{} : {}".format(self.timestamp, self.search)

    def to_xml(self, xml_root):
        entry = ET.Element('history')
        entry_url = ET.Element('url')
        entry_url.text = self.search
        entry_ts = ET.Element('timestamp')
        entry_ts.text = self.timestamp.timestamp()
        entry.append(entry_url)
        entry.append(entry_ts)
        xml_root.append(entry)

    @staticmethod
    def from_xml(xml_root, in_history):
        if xml_root.tag != 'history':
            raise InvalidXml("expected <history> tag here.")
        url, timestamp = None, None

        for child in xml_root:
            if child.tag == 'url':
                url = child.text
            elif child.tag == 'timestamp':
                try:
                    timestamp = datetime.fromtimestamp(child.text)
                except TypeError:
                    raise InvalidXml("invalid timestamp {}".format(child.text))
            else:
                raise InvalidXml("unknown tag {} as child of <history>".format(
                    child.tag))
        output = HistoryEntry()
        output.search = url
        output.timestamp = timestamp
        output.history = in_history

        return output


class History(models.Model):
    """ A history for a user, containing some web connections (http, https).
    Each history is timed, in a human-behaviour manner. """

    start_ts = models.DateTimeField(
        help_text=('The starting timestamp of the history. Useful for '
                   'cron-like structure.')

    )
    played = models.BooleanField(default=False)
    user = models.ForeignKey(
        profiles.Profile,
        on_delete=models.CASCADE
    )

    def return_history(self):
        """ Returns the history, sorted by increasing timestamps
        """
        output_history = self.historyentry_set.order_by('timestamp')
        output_history = [(item.search, item.timestamp.date())
                          for item in output_history]
        return output_history

    def __str__(self):
        """ Returns the string representation of a history.
        """
        entries = self.historyentry_set.order_by('timestamp')
        output = "[History]:\n"
        for entry in entries:
            output += str(entry) + '\n'
        return output

    async def play_histories(self):
        """ Actually plays the history.
        """
        self.played = True
        runner = await TorInstance.create(
            self.return_history(),
            self.user.browser_fingerprint.serialize_headers())
        runner.run()
        self.save()

    def to_xml(self, xml_root=None):
        ''' Exports the current history to xml '''
        standalone = False
        if xml_root is None:
            standalone = True
            xml_root = ET.Element('root')

        hist_node = ET.Element("history", attrib={
            'start-ts': self.start_ts,
            'played': 1 if self.played else 0,
            'user': self.user.pk,
        })
        xml_root.append(hist_node)
        for entry in self.historyentry_set.all():
            entry.to_xml(hist_node)

        if standalone:
            return xml_root

    @staticmethod
    def from_xml(xml_root):
        ''' Loads an history from an XML file '''

        REQUIRED_ATTR = ['start-ts', 'played', 'user']

        if xml_root.tag != 'history':
            raise InvalidXml('unexpected node {} as root of an history'.format(
                xml_root.tag))
        for attr in REQUIRED_ATTR:
            if attr not in xml_root.attrib:
                raise InvalidXml(('missing attribute "{}" for tag of type '
                                  'history').format(attr))
        start_ts = xml_root.attrib['start-ts']
        played = xml_root.attrib['played']
        user_pk = xml_root.attrib['user']
        users = History.objects.filter(pk=1)
        if len(users) != 1:
            raise InvalidXml('primary key for History {} is invalid'.format(
                user_pk))

        output = History()
        output.start_ts = start_ts
        output.played = played > 0
        output.user = users[0]

        for child in xml_root:
            HistoryEntry.from_xml(child, output)

        return output


PartialHistoryEntry = namedtuple('PartialHistoryEntry',
                                 ['url', 'timestamp'])


def generate_partial_history(user, t_start):
    """ Generate the part of the history resulting from the crawl starting at
    the given url.
    """
    timestamp = t_start
    result = []
    basis = generate_first_url(user)
    result.append(PartialHistoryEntry(basis, timestamp))
    t_start += 5 * random.weibullvariate(1, 1.5)
    crawler = crawl.CrawlingThread(basis)
    crawler.start()
    crawler.join()
    urls_tree = crawler.output_tree

    open_time = {}
    for elem in urls_tree:
        url, parent = elem.url, elem.parent
        timestamp = 0
        if parent is None:
            timestamp = t_start
        else:
            timestamp = open_time[parent] + 5 * random.weibullvariate(1, 1.5)
        open_time[elem] = timestamp
        result.append(PartialHistoryEntry(url, timestamp))
    return result


def generate_first_url(user):
    """ Generate the first url of a partial history, based on the user
    information. """

    def nonempty(seq):
        out = []
        for elt in seq:
            if elt:
                out.append(elt)
        return out

    all_keywords = profiles.Keyword.objects.filter(
        interest__profile__in=[user])
    all_websites = profiles.Website.objects.filter(
        interest__profile__in=[user])
    all_places = profiles.Place.objects.filter(
        interest__profile__in=[user])
    all_events = profiles.Event.objects.filter(
        interest__profile__in=[user])

    interest = random.choice(nonempty([
        all_keywords,
        all_websites,
        all_places,
        all_events,
    ]))
    search_term = random.choice(interest)
    url = search_term.generate_url(user)
    return url


def generate_history(user, start_time):
    """ Generate a new history for the user `user`, starting from timestamp
    `ts_start`.
    A few heuristics are used in order to give the impression that the history
    is actually played by a user.
    """

    # let's define a new history object.
    history = History(start_ts=start_time, user=user)
    length = HISTORY_MIN + floor(10 * random.weibullvariate(1, 1.5))
    history.full_clean()
    history.save()

    current_timestamp = start_time.timestamp()

    hist_size = 0

    while hist_size < length:
        current_timestamp += 5 * random.weibullvariate(1, 2.8)
        history_list = generate_partial_history(user, current_timestamp)
        current_timestamp = \
            history_list[-1].timestamp + 5 * random.weibullvariate(1, 5)
        for (url, timestamp) in history_list:
            if len(url) < 200:
                new_line = HistoryEntry(
                    search=url,
                    timestamp=datetime.fromtimestamp(timestamp),
                    history=history
                )
                try:
                    new_line.full_clean()
                    new_line.save()
                    hist_size += 1
                except ValidationError:
                    continue

    return history