import logging
import re
import uuid

from django.core.exceptions import ObjectDoesNotExist
from django.core.urlresolvers import reverse
from django.db import models
from django.db.models import TextField, QuerySet
from django.template.defaultfilters import striptags, truncatewords
from django.template.loader import render_to_string
from django.utils import timezone

from boards import settings
from boards.abstracts.tripcode import Tripcode
from boards.mdx_neboard import Parser
from boards.models import PostImage, Attachment
from boards.models.base import Viewable
from boards.models.post.export import get_exporter, DIFF_TYPE_JSON
from boards.models.post.manager import PostManager
from boards.models.user import Notification

CSS_CLS_HIDDEN_POST = 'hidden_post'
CSS_CLS_DEAD_POST = 'dead_post'
CSS_CLS_ARCHIVE_POST = 'archive_post'
CSS_CLS_POST = 'post'
CSS_CLS_MONOCHROME = 'monochrome'

TITLE_MAX_WORDS = 10

APP_LABEL_BOARDS = 'boards'

BAN_REASON_AUTO = 'Auto'

IMAGE_THUMB_SIZE = (200, 150)

TITLE_MAX_LENGTH = 200

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

PARAMETER_TRUNCATED = 'truncated'
PARAMETER_TAG = 'tag'
PARAMETER_OFFSET = 'offset'
PARAMETER_DIFF_TYPE = 'type'
PARAMETER_CSS_CLASS = 'css_class'
PARAMETER_THREAD = 'thread'
PARAMETER_IS_OPENING = 'is_opening'
PARAMETER_POST = 'post'
PARAMETER_OP_ID = 'opening_post_id'
PARAMETER_NEED_OPEN_LINK = 'need_open_link'
PARAMETER_REPLY_LINK = 'reply_link'
PARAMETER_NEED_OP_DATA = 'need_op_data'

POST_VIEW_PARAMS = (
    'need_op_data',
    'reply_link',
    'need_open_link',
    'truncated',
    'mode_tree',
    'perms',
)


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, null=True, blank=True)
    pub_time = models.DateTimeField()
    text = TextField(blank=True, null=True)
    _text_rendered = TextField(blank=True, null=True, editable=False)

    images = models.ManyToManyField(PostImage, null=True, blank=True,
                                    related_name='post_images', db_index=True)
    attachments = models.ManyToManyField(Attachment, null=True, blank=True,
                                         related_name='attachment_posts')

    poster_ip = models.GenericIPAddressField()

    # TODO This field can be removed cause UID is used for update now
    last_edit_time = models.DateTimeField()

    referenced_posts = models.ManyToManyField('Post', symmetrical=False,
                                              null=True,
                                              blank=True, related_name='refposts',
                                              db_index=True)
    refmap = models.TextField(null=True, blank=True)
    threads = models.ManyToManyField('Thread', db_index=True,
                                     related_name='multi_replies')
    thread = models.ForeignKey('Thread', db_index=True, related_name='pt+')

    url = models.TextField()
    uid = models.TextField(db_index=True)

    tripcode = models.CharField(max_length=50, blank=True, default='')
    opening = models.BooleanField(db_index=True)
    hidden = models.BooleanField(default=False)

    def __str__(self):
        return 'P#{}/{}'.format(self.id, self.get_title())

    def get_referenced_posts(self):
        threads = self.get_threads().all()
        return self.referenced_posts.filter(threads__in=threads)\
            .order_by('pub_time').distinct().all()

    def get_title(self) -> str:
        return self.title

    def get_title_or_text(self):
        title = self.get_title()
        if not title:
            title = truncatewords(striptags(self.get_text()), TITLE_MAX_WORDS)

        return title

    def build_refmap(self) -> None:
        """
        Builds a replies map string from replies list. This is a cache to stop
        the server from recalculating the map on every post show.
        """

        post_urls = [refpost.get_link_view()
                     for refpost in self.referenced_posts.all()]

        self.refmap = ', '.join(post_urls)

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

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

        return self.opening

    def get_absolute_url(self, thread=None):
        url = None

        if thread is None:
            thread = self.get_thread()

            # Url is cached only for the "main" thread. When getting url
            # for other threads, do it manually.
            if self.url:
                url = self.url

        if url is None:
            opening_id = thread.get_opening_post_id()
            url = reverse('thread', kwargs={'post_id': opening_id})
            if self.id != opening_id:
                url += '#' + str(self.id)

        return url

    def get_thread(self):
        return self.thread

    def get_threads(self) -> QuerySet:
        """
        Gets post's thread.
        """

        return self.threads

    def get_view(self, *args, **kwargs) -> str:
        """
        Renders post's HTML view. Some of the post params can be passed over
        kwargs for the means of caching (if we view the thread, some params
        are same for every post and don't need to be computed over and over.
        """

        thread = self.get_thread()

        css_classes = [CSS_CLS_POST]
        if thread.is_archived():
            css_classes.append(CSS_CLS_ARCHIVE_POST)
        elif not thread.can_bump():
            css_classes.append(CSS_CLS_DEAD_POST)
        if self.is_hidden():
            css_classes.append(CSS_CLS_HIDDEN_POST)
        if thread.is_monochrome():
            css_classes.append(CSS_CLS_MONOCHROME)

        params = dict()
        for param in POST_VIEW_PARAMS:
            if param in kwargs:
                params[param] = kwargs[param]

        params.update({
            PARAMETER_POST: self,
            PARAMETER_IS_OPENING: self.is_opening(),
            PARAMETER_THREAD: thread,
            PARAMETER_CSS_CLASS: ' '.join(css_classes),
        })

        return render_to_string('boards/post.html', params)

    def get_search_view(self, *args, **kwargs):
        return self.get_view(need_op_data=True, *args, **kwargs)

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

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

        for image in self.images.all():
            image_refs_count = image.post_images.count()
            if image_refs_count == 1:
                image.delete()

        for attachment in self.attachments.all():
            attachment_refs_count = attachment.attachment_posts.count()
            if attachment_refs_count == 1:
                attachment.delete()

        thread = self.get_thread()
        thread.last_edit_time = timezone.now()
        thread.save()

        super(Post, self).delete(using)

        logging.getLogger('boards.post.delete').info(
            'Deleted post {}'.format(self))

    def get_post_data(self, format_type=DIFF_TYPE_JSON, request=None,
                      include_last_update=False) -> str:
        """
        Gets post HTML or JSON data that can be rendered on a page or used by
        API.
        """

        return get_exporter(format_type).export(self, request,
                                                include_last_update)

    def notify_clients(self, recursive=True):
        """
        Sends post HTML data to the thread web socket.
        """

        if not settings.get_bool('External', 'WebsocketsEnabled'):
            return

        thread_ids = list()
        for thread in self.get_threads().all():
            thread_ids.append(thread.id)

            thread.notify_clients()

        if recursive:
            for reply_number in re.finditer(REGEX_REPLY, self.get_raw_text()):
                post_id = reply_number.group(1)

                try:
                    ref_post = Post.objects.get(id=post_id)

                    if ref_post.get_threads().exclude(id__in=thread_ids).exists():
                        # If post is in this thread, its thread was already notified.
                        # Otherwise, notify its thread separately.
                        ref_post.notify_clients(recursive=False)
                except ObjectDoesNotExist:
                    pass

    def build_url(self):
        self.url = self.get_absolute_url()
        self.save(update_fields=['url'])

    def save(self, force_insert=False, force_update=False, using=None,
             update_fields=None):
        new_post = self.id is None

        self._text_rendered = Parser().parse(self.get_raw_text())

        self.uid = str(uuid.uuid4())
        if update_fields is not None and 'uid' not in update_fields:
            update_fields += ['uid']

        if not new_post:
            for thread in self.get_threads().all():
                thread.last_edit_time = self.last_edit_time

                thread.save(update_fields=['last_edit_time', 'status'])

        super().save(force_insert, force_update, using, update_fields)

        # Post save triggers
        if new_post:
            self.build_url()

        self._connect_replies()
        self._connect_notifications()

    def get_text(self) -> str:
        return self._text_rendered

    def get_raw_text(self) -> str:
        return self.text

    def get_absolute_id(self) -> str:
        """
        If the post has many threads, shows its main thread OP id in the post
        ID.
        """

        if self.get_threads().count() > 1:
            return '{}/{}'.format(self.get_thread().get_opening_post_id(), self.id)
        else:
            return str(self.id)

    def _connect_notifications(self):
        for reply_number in re.finditer(REGEX_NOTIFICATION, self.get_raw_text()):
            user_name = reply_number.group(1).lower()
            Notification.objects.get_or_create(name=user_name, post=self)

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

        for reply_number in re.finditer(REGEX_REPLY, self.get_raw_text()):
            post_id = reply_number.group(1)

            try:
                referenced_post = Post.objects.get(id=post_id)

                referenced_post.referenced_posts.add(self)
                referenced_post.last_edit_time = self.pub_time
                referenced_post.build_refmap()
                referenced_post.save(update_fields=['refmap', 'last_edit_time'])
            except ObjectDoesNotExist:
                pass

    def connect_threads(self, opening_posts):
        for opening_post in opening_posts:
            threads = opening_post.get_threads().all()
            for thread in threads:
                if thread.can_bump():
                    thread.update_bump_status()

                thread.last_edit_time = self.last_edit_time
                thread.save(update_fields=['last_edit_time', 'status'])
            self.threads.add(opening_post.get_thread())

    def get_tripcode(self):
        if self.tripcode:
            return Tripcode(self.tripcode)

    def get_link_view(self):
        """
        Gets view of a reflink to the post.
        """
        result = '<a href="{}">&gt;&gt;{}</a>'.format(self.get_absolute_url(),
                                                      self.id)
        if self.is_opening():
            result = '<b>{}</b>'.format(result)

        return result

    def is_hidden(self) -> bool:
        return self.hidden

    def set_hidden(self, hidden):
        self.hidden = hidden