from sys import stdout
from typing import Optional

import gevent
from flask import g, request
from pusher_push_notifications import PushNotifications
from sqlalchemy import select, update
from sqlalchemy.orm import Query, aliased
from sqlalchemy.sql.expression import alias, func, text

from files.classes import Comment, Notification, Subscription, User
from files.helpers.alerts import NOTIFY_USERS
from files.helpers.assetcache import assetcache_path
from files.helpers.config.environment import (PUSHER_ID, PUSHER_KEY, SITE_FULL,
                                              SITE_ID)

if PUSHER_ID != 'blahblahblah':
	beams_client = PushNotifications(instance_id=PUSHER_ID, secret_key=PUSHER_KEY)

def pusher_thread(interests, c, username):
	if len(c.body) > 500: notifbody = c.body[:500] + '...'
	else: notifbody = c.body

	beams_client.publish_to_interests(
		interests=[interests],
		publish_body={
			'web': {
				'notification': {
					'title': f'New reply by @{username}',
					'body': notifbody,
					'deep_link': f'{SITE_FULL}/comment/{c.id}?context=8&read=true#context',
					'icon': SITE_FULL + assetcache_path(f'images/{SITE_ID}/icon.webp'),
				}
			},
			'fcm': {
				'notification': {
					'title': f'New reply by @{username}',
					'body': notifbody,
				},
				'data': {
					'url': f'/comment/{c.id}?context=8&read=true#context',
				}
			}
		},
	)
	stdout.flush()


def update_stateful_counters(comment, delta):
	"""
	When a comment changes publish status, we need to update all affected stateful
	comment counters (e.g. author comment count, post comment count)
	"""
	update_post_comment_count(comment, delta)
	update_author_comment_count(comment, delta)
	update_ancestor_descendant_counts(comment, delta)

def update_post_comment_count(comment, delta):
	author = comment.author
	comment.post.comment_count += delta
	g.db.add(comment.post)

def update_author_comment_count(comment, delta):
	author = comment.author
	comment.author.comment_count = g.db.query(Comment).filter(
		Comment.author_id == comment.author_id,
		Comment.parent_submission != None,
		Comment.is_banned == False,
		Comment.deleted_utc == 0,
	).count()
	g.db.add(comment.author)

def update_ancestor_descendant_counts(comment, delta):
	parent = comment.parent_comment_writable
	if parent is None:
		return
	parent.descendant_count += delta
	g.db.add(parent)
	update_ancestor_descendant_counts(parent, delta)

def bulk_recompute_descendant_counts(predicate = None, db=None):
	"""
	Recomputes the descendant_count of a large number of comments.

	The descendant_count of a comment is equal to the number of direct visible child comments
	plus the sum of the descendant_count of those visible child comments.

	:param predicate: If set, only update comments matching this predicate
	:param db: If set, use this instead of g.db

	So for example

		>>> bulk_update_descendant_counts()

	will update all comments, while

		>>> bulk_update_descendant_counts(lambda q: q.where(Comment.parent_submission == 32)

	will only update the descendant counts of comments where parent_submission=32

	Internally, how this works is
		1. Find the maximum level of comments matching the predicate
		2. Starting from that level and going down, for each level update the descendant_counts

	Since the comments at the max level will always have 0 children, this means that we will perform
	`level` updates to update all comments.

	The update query looks like

		UPDATE comments
		SET descendant_count=descendant_counts.descendant_count
		FROM (
			SELECT
				parent_comments.id AS id,
				coalesce(sum(child_comments.descendant_count + 1), 0) AS descendant_count
			FROM comments AS parent_comments
				LEFT OUTER JOIN comments AS child_comments ON parent_comments.id = child_comments.parent_comment_id
			GROUP BY parent_comments.id
		) AS descendant_counts
		WHERE comments.id = descendant_counts.id
			AND comments.level = :level_1
			<predicate goes here>
	"""
	db = db if db is not None else g.db
	max_level_query = db.query(func.max(Comment.level))
	if predicate:
		max_level_query = predicate(max_level_query)

	max_level = max_level_query.scalar()

	if max_level is None:
		max_level = 0

	for level in range(max_level, 0, -1):
		parent_comments = alias(Comment, name="parent_comments")
		child_comments = alias(Comment, name="child_comments")
		descendant_counts = aliased(
			Comment,
			(
				select(parent_comments)
				.join(
					child_comments,
					parent_comments.corresponding_column(Comment.id) == child_comments.corresponding_column(Comment.parent_comment_id),
					True
				)
				.group_by(parent_comments.corresponding_column(Comment.id))
				.with_only_columns(
					parent_comments.corresponding_column(Comment.id),
					func.coalesce(
						func.sum(child_comments.corresponding_column(Comment.descendant_count) + text(str(1))),
						text(str(0))
					).label('descendant_count')
				)
				.subquery(name='descendant_counts')
			),
			adapt_on_names=True
		)
		update_statement = (
			update(Comment)
			.values(descendant_count=descendant_counts.descendant_count)
			.execution_options(synchronize_session=False)
			.where(Comment.id == descendant_counts.id)
			.where(Comment.level == level)
		)
		if predicate:
			update_statement = predicate(update_statement)
		db.execute(update_statement)
	db.commit()

def comment_on_publish(comment:Comment):
	"""
	Run when comment becomes visible: immediately for non-filtered comments,
	or on approval for previously filtered comments.
	Should be used to update stateful counters, notifications, etc. that
	reflect the comments users will actually see.
	"""
	author = comment.author

	# Shadowbanned users are invisible. This may lead to inconsistencies if
	# a user comments while shadowed and is later unshadowed. (TODO?)
	if author.shadowbanned:
		return

	# Comment instances used for purposes other than actual comments (notifs,
	# DMs) shouldn't be considered published.
	if not comment.parent_submission:
		return

	# Generate notifs for: mentions, post subscribers, parent post/comment
	to_notify = NOTIFY_USERS(comment.body, comment.author)

	post_subscribers = g.db.query(Subscription.user_id).filter(
			Subscription.submission_id == comment.parent_submission,
			Subscription.user_id != comment.author_id,
		).all()
	to_notify.update([x[0] for x in post_subscribers])

	parent = comment.parent
	if parent and parent.author_id != comment.author_id and not parent.author.is_blocking(author):
		to_notify.add(parent.author_id)

	for uid in to_notify:
		notif = Notification(comment_id=comment.id, user_id=uid)
		g.db.add(notif)

	update_stateful_counters(comment, +1)

	# Generate push notifications if enabled.
	if PUSHER_ID != 'blahblahblah' and comment.author_id != parent.author_id:
		try:
			gevent.spawn(pusher_thread, f'{request.host}{parent.author.id}',
				comment, comment.author_name)
		except: pass

def comment_on_unpublish(comment:Comment):
	"""
	Run when a comment becomes invisible: when a moderator makes the comment non-visible
	by changing the filter_state to "removed", or when the user deletes the comment.
	Should be used to update stateful counters, notifications, etc. that
	reflect the comments users will actually see.
	"""
	update_stateful_counters(comment, -1)


def comment_filter_moderated(q: Query, v: Optional[User]) -> Query:
	if not (v and v.shadowbanned) and not (v and v.admin_level > 2):
		q = q.join(User, User.id == Comment.author_id) \
		     .filter(User.shadowbanned == None)
	if not v or v.admin_level < 2:
		q = q.filter(
			((Comment.filter_state != 'filtered')
				& (Comment.filter_state != 'removed'))
			| (Comment.author_id == ((v and v.id) or 0))
		)
	return q