import xml.etree.ElementTree as et

from boards.models import Post, Tag

TAG_THREAD = 'thread'
TAG_TAGS = 'tags'
TAG_TAG = 'tag'
TAG_TIME_FROM = 'timestamp_from'


class PostFilter:
    def __init__(self, content=None):
        self.content = content

    def filter(self, posts):
        return posts

    def add_filter(self, model_tag, value):
        return model_tag


class ThreadFilter(PostFilter):
    def filter(self, posts):
        op_id = self.content.text

        op = Post.objects.filter(opening=True, id=op_id).first()
        if op:
            return posts.filter(thread=op.get_thread())
        else:
            return posts.none()

    def add_filter(self, model_tag, value):
        thread_tag = et.SubElement(model_tag, TAG_THREAD)
        thread_tag.text = str(value)


class TagsFilter(PostFilter):
    def filter(self, posts):
        tags = []
        for tag_tag in self.content:
            try:
                tags.append(Tag.objects.get(name=tag_tag.text))
            except Tag.DoesNotExist:
                pass

        if tags:
            return posts.filter(thread__tags__in=tags)
        else:
            return posts.none()

    def add_filter(self, model_tag, value):
        tags_tag = et.SubElement(model_tag, TAG_TAGS)
        for tag_name in value:
            tag_tag = et.SubElement(tags_tag, TAG_TAG)
            tag_tag.text = tag_name


class TimestampFromFilter(PostFilter):
    def filter(self, posts):
        from_time = self.content.text
        return posts.filter(pub_time__gt=from_time)

    def add_filter(self, model_tag, value):
        tags_from_time = et.SubElement(model_tag, TAG_TIME_FROM)
        tags_from_time.text = value