import hashlib
import re
import time
import logging

import pytz

from django import forms
from django.core.files.uploadedfile import SimpleUploadedFile
from django.core.exceptions import ObjectDoesNotExist
from django.forms.utils import ErrorList
from django.utils.translation import ugettext_lazy as _, ungettext_lazy
from django.utils import timezone

from boards.mdx_neboard import formatters
from boards.models.attachment.downloaders import Downloader
from boards.models.post import TITLE_MAX_LENGTH
from boards.models import Tag, Post
from boards.utils import validate_file_size, get_file_mimetype, \
    FILE_EXTENSION_DELIMITER
from neboard import settings
import boards.settings as board_settings
import neboard

POW_HASH_LENGTH = 16
POW_LIFE_MINUTES = 5

REGEX_TAGS = re.compile(r'^[\w\s\d]+$', re.UNICODE)
REGEX_USERNAMES = re.compile(r'^[\w\s\d,]+$', re.UNICODE)

VETERAN_POSTING_DELAY = 5

ATTRIBUTE_PLACEHOLDER = 'placeholder'
ATTRIBUTE_ROWS = 'rows'

LAST_POST_TIME = 'last_post_time'
LAST_LOGIN_TIME = 'last_login_time'
TEXT_PLACEHOLDER = _('Type message here. Use formatting panel for more advanced usage.')
TAGS_PLACEHOLDER = _('music images i_dont_like_tags')

LABEL_TITLE = _('Title')
LABEL_TEXT = _('Text')
LABEL_TAG = _('Tag')
LABEL_SEARCH = _('Search')

ERROR_SPEED = 'Please wait %(delay)d second before sending message'
ERROR_SPEED_PLURAL = 'Please wait %(delay)d seconds before sending message'

TAG_MAX_LENGTH = 20

TEXTAREA_ROWS = 4

TRIPCODE_DELIM = '#'

# TODO Maybe this may be converted into the database table?
MIMETYPE_EXTENSIONS = {
    'image/jpeg': 'jpeg',
    'image/png': 'png',
    'image/gif': 'gif',
    'video/webm': 'webm',
    'application/pdf': 'pdf',
    'x-diff': 'diff',
    'image/svg+xml': 'svg',
    'application/x-shockwave-flash': 'swf',
    'image/x-ms-bmp': 'bmp',
    'image/bmp': 'bmp',
}


def get_timezones():
    timezones = []
    for tz in pytz.common_timezones:
        timezones.append((tz, tz),)
    return timezones


class FormatPanel(forms.Textarea):
    """
    Panel for text formatting. Consists of buttons to add different tags to the
    form text area.
    """

    def render(self, name, value, attrs=None):
        output = '<div id="mark-panel">'
        for formatter in formatters:
            output += '<span class="mark_btn"' + \
                      ' onClick="addMarkToMsg(\'' + formatter.format_left + \
                      '\', \'' + formatter.format_right + '\')">' + \
                      formatter.preview_left + formatter.name + \
                      formatter.preview_right + '</span>'

        output += '</div>'
        output += super(FormatPanel, self).render(name, value, attrs=attrs)

        return output


class PlainErrorList(ErrorList):
    def __unicode__(self):
        return self.as_text()

    def as_text(self):
        return ''.join(['(!) %s ' % e for e in self])


class NeboardForm(forms.Form):
    """
    Form with neboard-specific formatting.
    """

    def as_div(self):
        """
        Returns this form rendered as HTML <as_div>s.
        """

        return self._html_output(
            # TODO Do not show hidden rows in the list here
            normal_row='<div class="form-row">'
                       '<div class="form-label">'
                       '%(label)s'
                       '</div>'
                       '<div class="form-input">'
                       '%(field)s'
                       '</div>'
                       '</div>'
                       '<div class="form-row">'
                       '%(help_text)s'
                       '</div>',
            error_row='<div class="form-row">'
                      '<div class="form-label"></div>'
                      '<div class="form-errors">%s</div>'
                      '</div>',
            row_ender='</div>',
            help_text_html='%s',
            errors_on_separate_row=True)

    def as_json_errors(self):
        errors = []

        for name, field in list(self.fields.items()):
            if self[name].errors:
                errors.append({
                    'field': name,
                    'errors': self[name].errors.as_text(),
                })

        return errors


class PostForm(NeboardForm):

    title = forms.CharField(max_length=TITLE_MAX_LENGTH, required=False,
                            label=LABEL_TITLE,
                            widget=forms.TextInput(
                                attrs={ATTRIBUTE_PLACEHOLDER:
                                           'test#tripcode'}))
    text = forms.CharField(
        widget=FormatPanel(attrs={
            ATTRIBUTE_PLACEHOLDER: TEXT_PLACEHOLDER,
            ATTRIBUTE_ROWS: TEXTAREA_ROWS,
        }),
        required=False, label=LABEL_TEXT)
    file = forms.FileField(required=False, label=_('File'),
                             widget=forms.ClearableFileInput(
                                 attrs={'accept': 'file/*'}))
    file_url = forms.CharField(required=False, label=_('File URL'),
                                widget=forms.TextInput(
                                    attrs={ATTRIBUTE_PLACEHOLDER:
                                               'http://example.com/image.png'}))

    # This field is for spam prevention only
    email = forms.CharField(max_length=100, required=False, label=_('e-mail'),
                            widget=forms.TextInput(attrs={
                                'class': 'form-email'}))
    threads = forms.CharField(required=False, label=_('Additional threads'),
            widget=forms.TextInput(attrs={ATTRIBUTE_PLACEHOLDER:
                '123 456 789'}))

    guess = forms.CharField(widget=forms.HiddenInput(), required=False)
    timestamp = forms.CharField(widget=forms.HiddenInput(), required=False)
    iteration = forms.CharField(widget=forms.HiddenInput(), required=False)

    session = None
    need_to_ban = False

    def _update_file_extension(self, file):
        if file:
            mimetype = get_file_mimetype(file)
            extension = MIMETYPE_EXTENSIONS.get(mimetype)
            if extension:
                filename = file.name.split(FILE_EXTENSION_DELIMITER, 1)[0]
                new_filename = filename + FILE_EXTENSION_DELIMITER + extension

                file.name = new_filename
            else:
                logger = logging.getLogger('boards.forms.extension')

                logger.info('Unrecognized file mimetype: {}'.format(mimetype))

    def clean_title(self):
        title = self.cleaned_data['title']
        if title:
            if len(title) > TITLE_MAX_LENGTH:
                raise forms.ValidationError(_('Title must have less than %s '
                                              'characters') %
                                            str(TITLE_MAX_LENGTH))
        return title

    def clean_text(self):
        text = self.cleaned_data['text'].strip()
        if text:
            max_length = board_settings.get_int('Forms', 'MaxTextLength')
            if len(text) > max_length:
                raise forms.ValidationError(_('Text must have less than %s '
                                              'characters') % str(max_length))
        return text

    def clean_file(self):
        file = self.cleaned_data['file']

        if file:
            validate_file_size(file.size)
        self._update_file_extension(file)

        return file

    def clean_file_url(self):
        url = self.cleaned_data['file_url']

        file = None
        if url:
            file = self._get_file_from_url(url)

            if not file:
                raise forms.ValidationError(_('Invalid URL'))
            else:
                validate_file_size(file.size)
        self._update_file_extension(file)

        return file

    def clean_threads(self):
        threads_str = self.cleaned_data['threads']

        if len(threads_str) > 0:
            threads_id_list = threads_str.split(' ')

            threads = list()

            for thread_id in threads_id_list:
                try:
                    thread = Post.objects.get(id=int(thread_id))
                    if not thread.is_opening() or thread.get_thread().is_archived():
                        raise ObjectDoesNotExist()
                    threads.append(thread)
                except (ObjectDoesNotExist, ValueError):
                    raise forms.ValidationError(_('Invalid additional thread list'))

            return threads

    def clean(self):
        cleaned_data = super(PostForm, self).clean()

        if cleaned_data['email']:
            self.need_to_ban = True
            raise forms.ValidationError('A human cannot enter a hidden field')

        if not self.errors:
            self._clean_text_file()

        limit_speed = board_settings.get_bool('Forms', 'LimitPostingSpeed')
        if not self.errors and limit_speed:
            pow_difficulty = board_settings.get_int('Forms', 'PowDifficulty')
            if pow_difficulty > 0 and cleaned_data['timestamp'] and cleaned_data['iteration'] and cleaned_data['guess']:
                self._validate_hash(cleaned_data['timestamp'], cleaned_data['iteration'], cleaned_data['guess'], cleaned_data['text'])
            else:
                self._validate_posting_speed()

        return cleaned_data

    def get_file(self):
        """
        Gets file from form or URL.
        """

        file = self.cleaned_data['file']
        return file or self.cleaned_data['file_url']

    def get_tripcode(self):
        title = self.cleaned_data['title']
        if title is not None and TRIPCODE_DELIM in title:
            code = title.split(TRIPCODE_DELIM, maxsplit=1)[1] + neboard.settings.SECRET_KEY
            tripcode = hashlib.md5(code.encode()).hexdigest()
        else:
            tripcode = ''
        return tripcode

    def get_title(self):
        title = self.cleaned_data['title']
        if title is not None and TRIPCODE_DELIM in title:
            return title.split(TRIPCODE_DELIM, maxsplit=1)[0]
        else:
            return title

    def _clean_text_file(self):
        text = self.cleaned_data.get('text')
        file = self.get_file()

        if (not text) and (not file):
            error_message = _('Either text or file must be entered.')
            self._errors['text'] = self.error_class([error_message])

    def _validate_posting_speed(self):
        can_post = True

        posting_delay = settings.POSTING_DELAY

        if board_settings.get_bool('Forms', 'LimitPostingSpeed'):
            now = time.time()

            current_delay = 0

            if LAST_POST_TIME not in self.session:
                self.session[LAST_POST_TIME] = now

                need_delay = True
            else:
                last_post_time = self.session.get(LAST_POST_TIME)
                current_delay = int(now - last_post_time)

                need_delay = current_delay < posting_delay

            if need_delay:
                delay = posting_delay - current_delay
                error_message = ungettext_lazy(ERROR_SPEED, ERROR_SPEED_PLURAL,
                                               delay) % {'delay': delay}
                self._errors['text'] = self.error_class([error_message])

                can_post = False

            if can_post:
                self.session[LAST_POST_TIME] = now

    def _get_file_from_url(self, url: str) -> SimpleUploadedFile:
        """
        Gets an file file from URL.
        """

        img_temp = None

        try:
            for downloader in Downloader.__subclasses__():
                if downloader.handles(url):
                    return downloader.download(url)
            # If nobody of the specific downloaders handles this, use generic
            # one
            return Downloader.download(url)
        except forms.ValidationError as e:
            raise e
        except Exception as e:
            raise forms.ValidationError(e)

    def _validate_hash(self, timestamp: str, iteration: str, guess: str, message: str):
        post_time = timezone.datetime.fromtimestamp(
            int(timestamp[:-3]), tz=timezone.get_current_timezone())
        timedelta = (timezone.now() - post_time).seconds / 60
        if timedelta > POW_LIFE_MINUTES:
            self._errors['text'] = self.error_class([_('Stale PoW.')])

        payload = timestamp + message.replace('\r\n', '\n')
        difficulty = board_settings.get_int('Forms', 'PowDifficulty')
        target = str(int(2 ** (POW_HASH_LENGTH * 3) / difficulty))
        if len(target) < POW_HASH_LENGTH:
            target = '0' * (POW_HASH_LENGTH - len(target)) + target

        computed_guess = hashlib.sha256((payload + iteration).encode())\
                             .hexdigest()[0:POW_HASH_LENGTH]
        if guess != computed_guess or guess > target:
            self._errors['text'] = self.error_class(
                [_('Invalid PoW.')])


class ThreadForm(PostForm):

    tags = forms.CharField(
        widget=forms.TextInput(attrs={ATTRIBUTE_PLACEHOLDER: TAGS_PLACEHOLDER}),
        max_length=100, label=_('Tags'), required=True)
    monochrome = forms.BooleanField(label=_('Monochrome'), required=False)

    def clean_tags(self):
        tags = self.cleaned_data['tags'].strip()

        if not tags or not REGEX_TAGS.match(tags):
            raise forms.ValidationError(
                _('Inappropriate characters in tags.'))

        required_tag_exists = False
        tag_set = set()
        for tag_string in tags.split():
            tag, created = Tag.objects.get_or_create(name=tag_string.strip().lower())
            tag_set.add(tag)

            # If this is a new tag, don't check for its parents because nobody
            # added them yet
            if not created:
                tag_set |= set(tag.get_all_parents())

        for tag in tag_set:
            if tag.required:
                required_tag_exists = True
                break

        if not required_tag_exists:
            raise forms.ValidationError(
                _('Need at least one section.'))

        return tag_set

    def clean(self):
        cleaned_data = super(ThreadForm, self).clean()

        return cleaned_data

    def is_monochrome(self):
        return self.cleaned_data['monochrome']


class SettingsForm(NeboardForm):

    theme = forms.ChoiceField(choices=settings.THEMES, label=_('Theme'))
    image_viewer = forms.ChoiceField(choices=settings.IMAGE_VIEWERS, label=_('Image view mode'))
    username = forms.CharField(label=_('User name'), required=False)
    timezone = forms.ChoiceField(choices=get_timezones(), label=_('Time zone'))

    def clean_username(self):
        username = self.cleaned_data['username']

        if username and not REGEX_USERNAMES.match(username):
            raise forms.ValidationError(_('Inappropriate characters.'))

        return username


class SearchForm(NeboardForm):
    query = forms.CharField(max_length=500, label=LABEL_SEARCH, required=False)