from datetime import datetime, timedelta, date
from datetime import time as dtime
import logging
import re
import xml.etree.ElementTree as et

from django.core.cache import cache
from django.core.urlresolvers import reverse
from django.db import models, transaction
from django.template.loader import render_to_string
from django.utils import timezone

from markupfield.fields import MarkupField

from boards.models import PostImage, KeyPair, GlobalId, Signature
from boards.models.base import Viewable
from boards.models.thread import Thread
from boards import utils


APP_LABEL_BOARDS = 'boards'

CACHE_KEY_PPD = 'ppd'
CACHE_KEY_POST_URL = 'post_url'

POSTS_PER_DAY_RANGE = 7

BAN_REASON_AUTO = 'Auto'

IMAGE_THUMB_SIZE = (200, 150)

TITLE_MAX_LENGTH = 200

DEFAULT_MARKUP_TYPE = 'bbcode'

# TODO This should be removed
NO_IP = '0.0.0.0'

# TODO Real user agent should be saved instead of this
UNKNOWN_UA = ''

REGEX_REPLY = re.compile(r'\[post\](\d+)\[/post\]')

TAG_MODEL = 'model'
TAG_REQUEST = 'request'
TAG_RESPONSE = 'response'
TAG_ID = 'id'
TAG_STATUS = 'status'
TAG_MODELS = 'models'
TAG_TITLE = 'title'
TAG_TEXT = 'text'
TAG_THREAD = 'thread'
TAG_PUB_TIME = 'pub-time'
TAG_EDIT_TIME = 'edit-time'
TAG_PREVIOUS = 'previous'
TAG_NEXT = 'next'
TAG_SIGNATURES = 'signatures'
TAG_SIGNATURE = 'signature'
TAG_CONTENT = 'content'

TYPE_GET = 'get'

ATTR_VERSION = 'version'
ATTR_TYPE = 'type'
ATTR_NAME = 'name'
ATTR_VALUE = 'value'

STATUS_SUCCESS = 'success'

logger = logging.getLogger(__name__)


class PostManager(models.Manager):
    def create_post(self, title, text, image=None, thread=None, ip=NO_IP,
                    tags=None):
        """
        Creates new post
        """

        if not tags:
            tags = []

        posting_time = timezone.now()
        if not thread:
            thread = Thread.objects.create(bump_time=posting_time,
                                           last_edit_time=posting_time)
            new_thread = True
        else:
            thread.bump()
            thread.last_edit_time = posting_time
            thread.save()
            new_thread = False

        post = self.create(title=title,
                           text=text,
                           pub_time=posting_time,
                           thread_new=thread,
                           poster_ip=ip,
                           poster_user_agent=UNKNOWN_UA,  # TODO Get UA at
                           # last!
                           last_edit_time=posting_time)

        post.set_global_id()

        if image:
            post_image = PostImage.objects.create(image=image)
            post.images.add(post_image)
            logger.info('Created image #%d for post #%d' % (post_image.id,
                                                            post.id))

        thread.replies.add(post)
        list(map(thread.add_tag, tags))

        if new_thread:
            Thread.objects.process_oldest_threads()
        self.connect_replies(post)

        logger.info('Created post #%d with title %s'
                    % (post.id, post.get_title()))

        return post

    def delete_post(self, post):
        """
        Deletes post and update or delete its thread
        """

        post_id = post.id

        thread = post.get_thread()

        if post.is_opening():
            thread.delete()
        else:
            thread.last_edit_time = timezone.now()
            thread.save()

            post.delete()

        logger.info('Deleted post #%d (%s)' % (post_id, post.get_title()))

    def delete_posts_by_ip(self, ip):
        """
        Deletes all posts of the author with same IP
        """

        posts = self.filter(poster_ip=ip)
        for post in posts:
            self.delete_post(post)

    def connect_replies(self, post):
        """
        Connects replies to a post to show them as a reflink map
        """

        for reply_number in post.get_replied_ids():
            ref_post = self.filter(id=reply_number)
            if ref_post.count() > 0:
                referenced_post = ref_post[0]
                referenced_post.referenced_posts.add(post)
                referenced_post.last_edit_time = post.pub_time
                referenced_post.build_refmap()
                referenced_post.save(update_fields=['refmap', 'last_edit_time'])

                referenced_thread = referenced_post.get_thread()
                referenced_thread.last_edit_time = post.pub_time
                referenced_thread.save(update_fields=['last_edit_time'])

    def get_posts_per_day(self):
        """
        Gets average count of posts per day for the last 7 days
        """

        day_end = date.today()
        day_start = day_end - timedelta(POSTS_PER_DAY_RANGE)

        cache_key = CACHE_KEY_PPD + str(day_end)
        ppd = cache.get(cache_key)
        if ppd:
            return ppd

        day_time_start = timezone.make_aware(datetime.combine(
            day_start, dtime()), timezone.get_current_timezone())
        day_time_end = timezone.make_aware(datetime.combine(
            day_end, dtime()), timezone.get_current_timezone())

        posts_per_period = float(self.filter(
            pub_time__lte=day_time_end,
            pub_time__gte=day_time_start).count())

        ppd = posts_per_period / POSTS_PER_DAY_RANGE

        cache.set(cache_key, ppd)
        return ppd

    def generate_request_get(self, model_list: list):
        """
        Form a get request from a list of ModelId objects.
        """

        request = et.Element(TAG_REQUEST)
        request.set(ATTR_TYPE, TYPE_GET)
        request.set(ATTR_VERSION, '1.0')

        model = et.SubElement(request, TAG_MODEL)
        model.set(ATTR_VERSION, '1.0')
        model.set(ATTR_NAME, 'post')

        for post in model_list:
            tag_id = et.SubElement(model, TAG_ID)
            post.global_id.to_xml_element(tag_id)

        return et.tostring(request, 'unicode')

    def generate_response_get(self, model_list: list):
        response = et.Element(TAG_RESPONSE)

        status = et.SubElement(response, TAG_STATUS)
        status.text = STATUS_SUCCESS

        models = et.SubElement(response, TAG_MODELS)

        for post in model_list:
            model = et.SubElement(models, TAG_MODEL)
            model.set(ATTR_NAME, 'post')

            content_tag = et.SubElement(model, TAG_CONTENT)

            tag_id = et.SubElement(content_tag, TAG_ID)
            post.global_id.to_xml_element(tag_id)

            title = et.SubElement(content_tag, TAG_TITLE)
            title.text = post.title

            text = et.SubElement(content_tag, TAG_TEXT)
            text.text = post.text.raw

            if not post.is_opening():
                thread = et.SubElement(content_tag, TAG_THREAD)
                thread.text = str(post.get_thread().get_opening_post_id())

            pub_time = et.SubElement(content_tag, TAG_PUB_TIME)
            pub_time.text = str(post.get_pub_time_epoch())

            signatures_tag = et.SubElement(model, TAG_SIGNATURES)
            post_signatures = post.signature.all()
            if post_signatures:
                signatures = post.signatures
            else:
                # TODO Maybe the signature can be computed only once after
                # the post is added? Need to add some on_save signal queue
                # and add this there.
                key = KeyPair.objects.get(public_key=post.global_id.key)
                signatures = [Signature(
                    key_type=key.key_type,
                    key=key.public_key,
                    signature=key.sign(et.tostring(model, 'unicode')),
                    )]
            for signature in signatures:
                signature_tag = et.SubElement(signatures_tag, TAG_SIGNATURE)
                signature_tag.set(ATTR_TYPE, signature.key_type)
                signature_tag.set(ATTR_VALUE, signature.signature)

        return et.tostring(response, 'unicode')


class Post(models.Model, Viewable):
    """A post is a message."""

    objects = PostManager()

    class Meta:
        app_label = APP_LABEL_BOARDS
        ordering = ('id',)

    title = models.CharField(max_length=TITLE_MAX_LENGTH)
    pub_time = models.DateTimeField()
    text = MarkupField(default_markup_type=DEFAULT_MARKUP_TYPE,
                       escape_html=False)

    images = models.ManyToManyField(PostImage, null=True, blank=True,
                                    related_name='ip+', db_index=True)

    poster_ip = models.GenericIPAddressField()
    poster_user_agent = models.TextField()

    thread_new = models.ForeignKey('Thread', null=True, default=None,
                                   db_index=True)
    last_edit_time = models.DateTimeField()

    # Replies to the post
    referenced_posts = models.ManyToManyField('Post', symmetrical=False,
                                              null=True,
                                              blank=True, related_name='rfp+',
                                              db_index=True)

    # Replies map. This is built from the referenced posts list to speed up
    # page loading (no need to get all the referenced posts from the database).
    refmap = models.TextField(null=True, blank=True)

    # Global ID with author key. If the message was downloaded from another
    # server, this indicates the server.
    global_id = models.OneToOneField('GlobalId', null=True, blank=True)

    # One post can be signed by many nodes that give their trust to it
    signature = models.ManyToManyField('Signature', null=True, blank=True)

    def __unicode__(self):
        return '#' + str(self.id) + ' ' + self.title + ' (' + \
               self.text.raw[:50] + ')'

    def get_title(self):
        """
        Gets original post title or part of its text.
        """

        title = self.title
        if not title:
            title = self.text.rendered

        return title

    def build_refmap(self):
        """
        Builds a replies map string from replies list. This is a cache to stop
        the server from recalculating the map on every post show.
        """
        map_string = ''

        first = True
        for refpost in self.referenced_posts.all():
            if not first:
                map_string += ', '
            map_string += '<a href="%s">&gt;&gt;%s</a>' % (refpost.get_url(),
                                                           refpost.id)
            first = False

        self.refmap = map_string

    def get_sorted_referenced_posts(self):
        return self.refmap

    def is_referenced(self):
        return len(self.refmap) > 0

    def is_opening(self):
        """
        Checks if this is an opening post or just a reply.
        """

        return self.get_thread().get_opening_post_id() == self.id

    @transaction.atomic
    def add_tag(self, tag):
        edit_time = timezone.now()

        thread = self.get_thread()
        thread.add_tag(tag)
        self.last_edit_time = edit_time
        self.save(update_fields=['last_edit_time'])

        thread.last_edit_time = edit_time
        thread.save(update_fields=['last_edit_time'])

    @transaction.atomic
    def remove_tag(self, tag):
        edit_time = timezone.now()

        thread = self.get_thread()
        thread.remove_tag(tag)
        self.last_edit_time = edit_time
        self.save(update_fields=['last_edit_time'])

        thread.last_edit_time = edit_time
        thread.save(update_fields=['last_edit_time'])

    def get_url(self, thread=None):
        """
        Gets full url to the post.
        """

        cache_key = CACHE_KEY_POST_URL + str(self.id)
        link = cache.get(cache_key)

        if not link:
            if not thread:
                thread = self.get_thread()

            opening_id = thread.get_opening_post_id()

            if self.id != opening_id:
                link = reverse('thread', kwargs={
                    'post_id': opening_id}) + '#' + str(self.id)
            else:
                link = reverse('thread', kwargs={'post_id': self.id})

            cache.set(cache_key, link)

        return link

    def get_thread(self):
        """
        Gets post's thread.
        """

        return self.thread_new

    def get_referenced_posts(self):
        return self.referenced_posts.only('id', 'thread_new')

    def get_text(self):
        return self.text

    def get_view(self, moderator=False, need_open_link=False,
                 truncated=False, *args, **kwargs):
        if 'is_opening' in kwargs:
            is_opening = kwargs['is_opening']
        else:
            is_opening = self.is_opening()

        if 'thread' in kwargs:
            thread = kwargs['thread']
        else:
            thread = self.get_thread()

        if 'can_bump' in kwargs:
            can_bump = kwargs['can_bump']
        else:
            can_bump = thread.can_bump()

        if is_opening:
            opening_post_id = self.id
        else:
            opening_post_id = thread.get_opening_post_id()

        return render_to_string('boards/post.html', {
            'post': self,
            'moderator': moderator,
            'is_opening': is_opening,
            'thread': thread,
            'bumpable': can_bump,
            'need_open_link': need_open_link,
            'truncated': truncated,
            'opening_post_id': opening_post_id,
        })

    def get_first_image(self):
        return self.images.earliest('id')

    def delete(self, using=None):
        """
        Deletes all post images and the post itself.
        """

        self.images.all().delete()
        self.signature.all().delete()
        if self.global_id:
            self.global_id.delete()

        super(Post, self).delete(using)

    def set_global_id(self, key_pair=None):
        """
        Sets global id based on the given key pair. If no key pair is given,
        default one is used.
        """

        if key_pair:
            key = key_pair
        else:
            try:
                key = KeyPair.objects.get(primary=True)
            except KeyPair.DoesNotExist:
                # Do not update the global id because there is no key defined
                return
        global_id = GlobalId(key_type=key.key_type,
                             key=key.public_key,
                             local_id = self.id)
        global_id.save()

        self.global_id = global_id

        self.save(update_fields=['global_id'])

    def get_pub_time_epoch(self):
        return utils.datetime_to_epoch(self.pub_time)

    def get_edit_time_epoch(self):
        return utils.datetime_to_epoch(self.last_edit_time)

    def get_replied_ids(self):
        return re.findall(REGEX_REPLY, self.text.raw)