from django.contrib.auth.models import User
from django.db.models import Q, Count, Aggregate, CharField, Value, BooleanField

from bookmarks.models import Bookmark, Tag


class Concat(Aggregate):
    function = 'GROUP_CONCAT'
    template = '%(function)s(%(distinct)s%(expressions)s)'

    def __init__(self, expression, distinct=False, **extra):
        super(Concat, self).__init__(
            expression,
            distinct='DISTINCT ' if distinct else '',
            output_field=CharField(),
            **extra)


def query_bookmarks(user: User, query_string: str):
    # Add aggregated tag info to bookmark instances
    query_set = Bookmark.objects \
        .annotate(tag_count=Count('tags'),
                  tag_string=Concat('tags__name'),
                  tag_projection=Value(True, BooleanField()))

    # Filter for user
    query_set = query_set.filter(owner=user)

    # Split query into search terms and tags
    query = _parse_query_string(query_string)

    # Filter for search terms and tags
    for term in query['search_terms']:
        query_set = query_set.filter(
            Q(title__contains=term)
            | Q(description__contains=term)
            | Q(website_title__contains=term)
            | Q(website_description__contains=term)
        )

    for tag_name in query['tag_names']:
        query_set = query_set.filter(
            tags__name=tag_name
        )

    # Sort by modification date
    query_set = query_set.order_by('-date_modified')

    return query_set


def query_tags(user: User, query_string: str):
    query_set = Tag.objects

    # Filter for user
    query_set = query_set.filter(owner=user)

    # Only show tags which have bookmarks
    query_set = query_set.filter(bookmark__isnull=False)

    # Split query into search terms and tags
    query = _parse_query_string(query_string)

    # Filter for search terms and tags
    for term in query['search_terms']:
        query_set = query_set.filter(
            Q(bookmark__title__contains=term)
            | Q(bookmark__description__contains=term)
            | Q(bookmark__website_title__contains=term)
            | Q(bookmark__website_description__contains=term)
        )

    for tag_name in query['tag_names']:
        query_set = query_set.filter(
            bookmark__tags__name=tag_name
        )

    return query_set.distinct()


def _parse_query_string(query_string):
    # Sanitize query params
    if not query_string:
        query_string = ''

    # Split query into search terms and tags
    keywords = query_string.strip().split(' ')
    keywords = [word for word in keywords if word]

    search_terms = [word for word in keywords if word[0] != '#']
    tag_names = [word[1:] for word in keywords if word[0] == '#']

    return {
        'search_terms': search_terms,
        'tag_names': tag_names,
    }