import uuid

import hashlib
import re
from django.db import models
from django.db.models import TextField
from django.template.defaultfilters import truncatewords, striptags
from django.template.loader import render_to_string
from django.urls import reverse

from boards.abstracts.constants import REGEX_REPLY
from boards.abstracts.tripcode import Tripcode
from boards.models import Attachment, KeyPair, GlobalId
from boards.models.attachment import FILE_TYPES_IMAGE
from boards.models.base import Viewable
from boards.models.post.export import get_exporter, DIFF_TYPE_JSON
from boards.models.post.manager import PostManager, NO_IP
from boards.utils import datetime_to_epoch

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'

CSS_CLASS_DELIMITER = ' '

TITLE_MAX_WORDS = 10

APP_LABEL_BOARDS = 'boards'

BAN_REASON_AUTO = 'Auto'

TITLE_MAX_LENGTH = 200

REGEX_GLOBAL_REPLY = re.compile(r'\[post\](\w+)::([^:]+)::(\d+)\[/post\]')
REGEX_URL = re.compile(r'https?\://[a-zA-Z0-9\-\.]+\.[a-zA-Z]{2,3}(/\S*)?')
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',
    'tree_depth',
)

TEMPLATE_POST = 'boards/post.html'


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

    attachments = models.ManyToManyField(Attachment, blank=True,
                                         related_name='attachment_posts')

    poster_ip = models.GenericIPAddressField()

    # Used for cache and threads updating
    last_edit_time = models.DateTimeField()

    referenced_posts = models.ManyToManyField('Post', symmetrical=False,
                                              blank=True, related_name='refposts',
                                              db_index=True)
    refmap = models.TextField(null=True, blank=True)
    thread = models.ForeignKey('Thread', on_delete=models.CASCADE,
                               db_index=True, related_name='replies')

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

    # 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,
                                     on_delete=models.CASCADE)

    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_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, excluded_ids=None) -> 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.
        """

        replies = self.referenced_posts
        if excluded_ids is not None:
            replies = replies.exclude(id__in=excluded_ids)
        else:
            replies = replies.all()

        post_urls = [refpost.get_link_view() for refpost in replies]

        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 is cached only for the "main" thread. When getting url
        # for other threads, do it manually.
        return self.url or self._build_url()

    def get_thread(self):
        return self.thread

    def get_thread_id(self):
        return self.thread_id

    def _get_cache_key(self):
        return [datetime_to_epoch(self.last_edit_time)]

    def get_view_params(self, *args, **kwargs):
        """
        Gets the parameters required for viewing the post based on the arguments
        given and the post itself.
        """
        thread = kwargs.get('thread') or 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: CSS_CLASS_DELIMITER.join(css_classes),
        })

        return params

    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.
        """
        params = self.get_view_params(*args, **kwargs)

        return render_to_string(TEMPLATE_POST, params)

    def get_images(self) -> Attachment:
        return self.attachments.filter(mimetype__in=FILE_TYPES_IMAGE)

    def get_first_image(self) -> Attachment:
        try:
            return self.get_images().earliest('-id')
        except Attachment.DoesNotExist:
            return None

    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_str(self):
        return str(self.pub_time)

    def get_replied_ids(self):
        """
        Gets ID list of the posts that this post replies.
        """

        raw_text = self.get_raw_text()

        local_replied = REGEX_REPLY.findall(raw_text)
        global_replied = []
        for match in REGEX_GLOBAL_REPLY.findall(raw_text):
            key_type = match[0]
            key = match[1]
            local_id = match[2]

            try:
                global_id = GlobalId.objects.get(key_type=key_type,
                                                 key=key, local_id=local_id)
                for post in Post.objects.filter(global_id=global_id).only('id'):
                    global_replied.append(post.id)
            except GlobalId.DoesNotExist:
                pass
        return local_replied + global_replied

    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 _build_url(self):
        if self.id:
            opening = self.is_opening()
            opening_id = self.id if opening else self.get_thread().get_opening_post_id()
            url = reverse('thread', kwargs={'post_id': opening_id})
            if not opening:
                url += '#' + str(self.id)

            return url

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

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

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

        if new_post:
            if not self.url:
                self.url = self._build_url()
            super().save(update_fields=['url'])

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

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

    def get_sync_text(self) -> str:
        """
        Returns text applicable for sync. It has absolute post reflinks.
        """

        replacements = dict()
        for post_id in REGEX_REPLY.findall(self.get_raw_text()):
            try:
                absolute_post_id = str(Post.objects.get(id=post_id).global_id)
                replacements[post_id] = absolute_post_id
            except Post.DoesNotExist:
                pass

        text = self.get_raw_text() or ''
        for key in replacements:
            text = text.replace('[post]{}[/post]'.format(key),
                                '[post]{}[/post]'.format(replacements[key]))
        text = text.replace('\r\n', '\n').replace('\r', '\n')

        return text

    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

    def clear_cache(self):
        """
        Clears sync data (content cache, signatures etc).
        """
        global_id = self.global_id
        if global_id is not None and global_id.is_local()\
                and global_id.content is not None:
            global_id.clear_cache()

    def get_tags(self):
        return self.get_thread().get_tags()

    def get_ip_color(self):
        return hashlib.md5(self.poster_ip.encode()).hexdigest()[:6]

    def has_ip(self):
        return self.poster_ip != NO_IP

    def has_global_id(self):
        return self.global_id_id is not None