from datetime import datetime, timedelta
from datetime import time as dtime
import os
from random import random
import time
import math
import re
import hashlib

from django.core.cache import cache
from django.core.paginator import Paginator

from django.db import models
from django.http import Http404
from django.utils import timezone
from markupfield.fields import MarkupField

from neboard import settings
from boards import thumbs

MAX_TITLE_LENGTH = 50

APP_LABEL_BOARDS = 'boards'

CACHE_KEY_PPD = 'ppd'

POSTS_PER_DAY_RANGE = range(7)

BAN_REASON_AUTO = 'Auto'

IMAGE_THUMB_SIZE = (200, 150)

TITLE_MAX_LENGTH = 50

DEFAULT_MARKUP_TYPE = 'markdown'

NO_PARENT = -1
NO_IP = '0.0.0.0'
UNKNOWN_UA = ''
ALL_PAGES = -1
IMAGES_DIRECTORY = 'images/'
FILE_EXTENSION_DELIMITER = '.'

SETTING_MODERATE = "moderate"

REGEX_REPLY = re.compile('>>(\d+)')


class PostManager(models.Manager):

    def create_post(self, title, text, image=None, thread=None,
                    ip=NO_IP, tags=None, user=None):
        """
        Create new post
        """

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

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

        thread.replies.add(post)
        if tags:
            linked_tags = []
            for tag in tags:
                tag_linked_tags = tag.get_linked_tags()
                if len(tag_linked_tags) > 0:
                    linked_tags.extend(tag_linked_tags)

            tags.extend(linked_tags)
            map(thread.add_tag, tags)

        self._delete_old_threads()
        self.connect_replies(post)

        return post

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

        thread = post.thread_new

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

            post.delete()

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

        posts = self.filter(poster_ip=ip)
        map(self.delete_post, posts)

    # TODO This method may not be needed any more, because django's paginator
    # is used
    def get_threads(self, tag=None, page=ALL_PAGES,
                    order_by='-bump_time', archived=False):
        if tag:
            threads = tag.threads

            if not threads.exists():
                raise Http404
        else:
            threads = Thread.objects.all()

        threads = threads.filter(archived=archived).order_by(order_by)

        if page != ALL_PAGES:
            threads = Paginator(threads, settings.THREADS_PER_PAGE).page(
                    page).object_list

        return threads

    # TODO Move this method to thread manager
    def _delete_old_threads(self):
        """
        Preserves maximum thread count. If there are too many threads,
        archive the old ones.
        """

        threads = self.get_threads()
        thread_count = threads.count()

        if thread_count > settings.MAX_THREAD_COUNT:
            num_threads_to_delete = thread_count - settings.MAX_THREAD_COUNT
            old_threads = threads[thread_count - num_threads_to_delete:]

            for thread in old_threads:
                thread.archived = True
                thread.last_edit_time = timezone.now()
                thread.save()

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

        for reply_number in re.finditer(REGEX_REPLY, post.text.raw):
            post_id = reply_number.group(1)
            ref_post = self.filter(id=post_id)
            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.save()

                referenced_thread = referenced_post.thread_new
                referenced_thread.last_edit_time = post.pub_time
                referenced_thread.save()

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

        today = datetime.now().date()
        ppd = cache.get(CACHE_KEY_PPD + str(today))
        if ppd:
            return ppd

        posts_per_days = []
        for i in POSTS_PER_DAY_RANGE:
            day_end = today - timedelta(i + 1)
            day_start = today - timedelta(i + 2)

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

        ppd = (sum(posts_per_day for posts_per_day in posts_per_days) /
               len(posts_per_days))
        cache.set(CACHE_KEY_PPD, ppd)
        return ppd


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

    objects = PostManager()

    class Meta:
        app_label = APP_LABEL_BOARDS

    # TODO Save original file name to some field
    def _update_image_filename(self, filename):
        """Get unique image filename"""

        path = IMAGES_DIRECTORY
        new_name = str(int(time.mktime(time.gmtime())))
        new_name += str(int(random() * 1000))
        new_name += FILE_EXTENSION_DELIMITER
        new_name += filename.split(FILE_EXTENSION_DELIMITER)[-1:][0]

        return os.path.join(path, new_name)

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

    image_width = models.IntegerField(default=0)
    image_height = models.IntegerField(default=0)

    image_pre_width = models.IntegerField(default=0)
    image_pre_height = models.IntegerField(default=0)

    image = thumbs.ImageWithThumbsField(upload_to=_update_image_filename,
                                        blank=True, sizes=(IMAGE_THUMB_SIZE,),
                                        width_field='image_width',
                                        height_field='image_height',
                                        preview_width_field='image_pre_width',
                                        preview_height_field='image_pre_height')
    image_hash = models.CharField(max_length=36)

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

    thread = models.ForeignKey('Post', null=True, default=None)
    thread_new = models.ForeignKey('Thread', null=True, default=None)
    last_edit_time = models.DateTimeField()
    user = models.ForeignKey('User', null=True, default=None)

    referenced_posts = models.ManyToManyField('Post', symmetrical=False,
                                              null=True,
                                              blank=True, related_name='rfp+')

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

    def get_title(self):
        title = self.title
        if len(title) == 0:
            title = self.text.rendered

        return title

    def get_sorted_referenced_posts(self):
        return self.referenced_posts.order_by('id')

    def is_referenced(self):
        return self.referenced_posts.all().exists()

    def is_opening(self):
        return self.thread_new.get_replies()[0] == self

    def save(self, *args, **kwargs):
        """
        Save the model and compute the image hash
        """

        if not self.pk and self.image:
            md5 = hashlib.md5()
            for chunk in self.image.chunks():
                md5.update(chunk)
            self.image_hash = md5.hexdigest()
        super(Post, self).save(*args, **kwargs)


class Thread(models.Model):

    class Meta:
        app_label = APP_LABEL_BOARDS

    tags = models.ManyToManyField('Tag')
    bump_time = models.DateTimeField()
    last_edit_time = models.DateTimeField()
    replies = models.ManyToManyField('Post', symmetrical=False, null=True,
                                     blank=True, related_name='tre+')
    archived = models.BooleanField(default=False)

    def get_tags(self):
        """
        Get a sorted tag list
        """

        return self.tags.order_by('name')

    def bump(self):
        """
        Bump (move to up) thread
        """

        if self.can_bump():
            self.bump_time = timezone.now()

    def get_reply_count(self):
        return self.replies.count()

    def get_images_count(self):
        return self.replies.filter(image_width__gt=0).count()

    def can_bump(self):
        """
        Check if the thread can be bumped by replying
        """

        if self.archived:
            return False

        post_count = self.get_reply_count()

        return post_count < settings.MAX_POSTS_PER_THREAD

    def delete_with_posts(self):
        """
        Completely delete thread and all its posts
        """

        if self.replies.count() > 0:
            self.replies.all().delete()

        self.delete()

    def get_last_replies(self):
        """
        Get last replies, not including opening post
        """

        if settings.LAST_REPLIES_COUNT > 0:
            reply_count = self.get_reply_count()

            if reply_count > 0:
                reply_count_to_show = min(settings.LAST_REPLIES_COUNT,
                                          reply_count - 1)
                last_replies = self.replies.all().order_by('pub_time')[
                               reply_count - reply_count_to_show:]

                return last_replies

    def get_skipped_replies_count(self):
        last_replies = self.get_last_replies()
        return self.get_reply_count() - len(last_replies) - 1

    def get_replies(self):
        """
        Get sorted thread posts
        """

        return self.replies.all().order_by('pub_time')

    def add_tag(self, tag):
        """
        Connect thread to a tag and tag to a thread
        """

        self.tags.add(tag)
        tag.threads.add(self)

    def get_opening_post(self):
        """
        Get first post of the thread
        """

        return self.get_replies()[0]

    def __unicode__(self):
        return str(self.id)

    def get_pub_time(self):
        """
        Thread does not have its own pub time, so we need to get it from
        the opening post
        """

        return self.get_opening_post().pub_time