#!/usr/bin/env python3

import sys
import os
from collections import defaultdict
import datetime
from time import sleep
import json
from typing import Dict, Set
import mattermost
import mattermost.ws

SERVER = "mattermost.zeus.gent"
TEAM_NAME = "zeus"
CHAN_NAME = "pannenkoeken"
EMOJI_NAME = "pancakes"
DOUBLE_EMOJI_NAME = "own_pancakes"
TAGGERS = [
	# Board
	"flynn",
	"bobby",
	"pcassima",
	"redfast00",
	"francis.",
	"hannes",
	"arnhoudt",
	"mel",

	# Sneaky backdoor (actually just for testing and if you read this, nobody has removed it)
	"midgard",
]

TOKEN = os.getenv("MM_ACCESS_TOKEN")
USER = os.getenv("MM_USERNAME")
PASSWORD = os.getenv("MM_PASSWORD")

# Set to False to disable reacting with an emoji for the count
CONFIRMATION_EMOJI = True


since_arg_i = None
try:
	since_arg_i = sys.argv.index("--since")
except ValueError:
	SINCE = datetime.datetime.now(tz=datetime.timezone.utc)
	print(f"Warning: no start time provided, using now. Use `--since "
		f"{SINCE.isoformat(timespec='seconds')}` to pin the start time.", file=sys.stderr)
if since_arg_i:
	SINCE = datetime.datetime.fromisoformat(sys.argv[since_arg_i + 1])

clean = "--clean" in sys.argv[1:]
live = "--live" in sys.argv[1:]
if "--no-confirm" in sys.argv[1:]:
	CONFIRMATION_EMOJI = False



if not clean and sys.stdout.isatty():
	print("To use this data, redirect stdout to a file and use table.py on it.", file=sys.stderr)


def first(iterable, default=None):
	for x in iterable:
		return x
	return default


##################################
# Log in
mm = mattermost.MMApi(f"https://{SERVER}/api")

if TOKEN:
	mm.login(bearer=TOKEN)
else:
	assert USER, "USER and PASSWORD or TOKEN envvars must be set"
	assert PASSWORD, "USER and PASSWORD or TOKEN envvars must be set"
	mm.login(USER, PASSWORD)

# pylint: disable=protected-access # bad library design: can't fix this without extra API request
our_user_id = mm._my_user_id


##################################
# Get channel
team_data = first(filter(
	lambda team: team["name"] == TEAM_NAME,
	mm.get_teams()
))
assert team_data, "Team should exist"

channel_data = first(filter(
	lambda chan: chan["name"] == CHAN_NAME,
	mm.get_team_channels(team_data["id"])
))
assert channel_data, "Channel should exist"
channel = channel_data["id"]


##################################
# Get users

# People who are authorized to do verifications
tagger_ids = {u["id"]: u["username"] for u in mm.get_users_by_usernames_list(TAGGERS)}

users = {u["id"]: u for u in mm.get_users(in_channel=channel)}
for user in users.values():
	assert user["username"].find(" ") == -1, f"{user['username']} shouldn't have spaces in username"

def get_username(userid):
	# When someone joined later
	if userid not in users:
		users[userid] = mm.get_user(userid)

	username = users[userid]["username"]
	assert username.find(" ") == -1, f"{username} shouldn't have spaces in username"
	return username


##################################
# Get posts
posts = {}
def get_post(postid, force_fetch=False):
	if postid not in posts or force_fetch:
		posts[postid] = mm.get_post(postid)

	return posts[postid]


def parse_mm_timestamp(mm_timestamp):
	return datetime.datetime.fromtimestamp(mm_timestamp / 1000, datetime.timezone.utc)

def to_mm_timestamp(dt):
	# pylint: disable=invalid-name
	return int(dt.timestamp() * 1000)


def reaction_qualifies(reaction):
	if reaction["user_id"] not in tagger_ids:
		return 0
	if reaction["emoji_name"] == EMOJI_NAME:
		return 1
	if reaction["emoji_name"] == DOUBLE_EMOJI_NAME:
		return 2
	return 0


def post_score(awardee_id, post_id, awarder_id):
	return max(awarded[awardee_id][post_id][awarder_id], default=0)


def emit_change_line(post, awardee_id, awarder_id, prev_score, score):
	if score == prev_score:
		return

	awardee = get_username(awardee_id)
	awarder = get_username(awarder_id)

	post_time = parse_mm_timestamp(post["create_at"]).isoformat(timespec="microseconds")

	if score == 0:
		message = f"{awarder} retracted their verification"
	elif prev_score == 0:
		message = f"{awarder} verified with score {score}"
	else:
		message = f"{awarder} updated their verification's score from {prev_score} to {score}"

	print(f"{awardee} {post['id']} at {post_time}: {message}", flush=True)


# awarded[awardee][post_id][verifier]: set of values
awarded: Dict[str, Dict[str, Dict[str, Set[int]]]] = \
	defaultdict(lambda: defaultdict(lambda: defaultdict(set)))


def process_change(reaction, action):
	value = reaction_qualifies(reaction)
	if value == 0:
		return

	post = get_post(reaction["post_id"])
	if parse_mm_timestamp(post["create_at"]) < SINCE:
		return

	awardee_id = post["user_id"]
	awarder_id = reaction["user_id"]

	prev_score = post_score(awardee_id, post["id"], awarder_id)
	action(awarded[awardee_id][post["id"]][awarder_id], value)
	score      = post_score(awardee_id, post["id"], awarder_id)

	emit_change_line(post, awardee_id, awarder_id, prev_score, score)
	update_confirmation(post["id"])


def award_if_appropriate(reaction):
	process_change(
		reaction,
		lambda values_set, value: values_set.add(value)
	)

def retract_if_appropriate(reaction):
	process_change(
		reaction,
		lambda values_set, value: values_set.discard(value)
	)


def get_posts_for_channel(mmapi, channel_id, since, **kwargs):
	after = None
	while True:
		data_page = mmapi._get("/v4/channels/"+channel_id+"/posts", params=(
			{ "after": after }
			if after else
			{ "since": to_mm_timestamp(since) }
		), **kwargs)

		order = list(reversed(data_page["order"]))
		for post_id in order:
			yield data_page["posts"][post_id]

		if not order:
			return
		after = order[-1]


CONFIRMATION_EMOJI_NAMES = [
	*(f"num{i}" for i in range(1, 99 + 1)),
	"heavy_plus_sign"
]
def confirmation_emoji_name(count):
	if count < 0:
		return "exclamation"
	try:
		return CONFIRMATION_EMOJI_NAMES[count - 1]
	except IndexError:
		return CONFIRMATION_EMOJI_NAMES[-1]


def persevere(f, e_type=Exception, backoff=1):
	while True:
		try:
			f()
			return
		except e_type as exc:
			print(exc, file=sys.stderr)
		print(f"Trying again in {backoff} second(s)", file=sys.stderr)
		sleep(backoff)


# awarded[awardee][post_id][verifier]: set of values
def count_verifications(user_id):
	return sum(
		max(
			(
				max(values, default=0) for values in post_verifications.values()
			),
			default=0
		)
		for post_verifications in awarded[user_id].values()
	)


def update_confirmation(post_id):
	if not CONFIRMATION_EMOJI:
		return

	post = get_post(post_id, force_fetch=True)
	remove_reactions_from_post(post)

	new_count = count_verifications(post["user_id"])

	if new_count > 0:
		persevere(lambda: mm.create_reaction(our_user_id, post_id, confirmation_emoji_name(new_count)))


def remove_reactions_from_post(post):
	for reaction in post.get("metadata", {}).get("reactions", []):
		if reaction["user_id"] == our_user_id:
			# pylint: disable=cell-var-from-loop # persevere doesn't store lambda
			persevere(lambda: remove_reaction(post["id"], reaction["emoji_name"]))


def remove_reaction(post_id, emoji_name):
	# pylint: disable=protected-access # library recommends this in docs
	mm._delete(f"/v4/users/me/posts/{post_id}/reactions/{emoji_name}")


def handle_backlog(since):
	for post in get_posts_for_channel(mm, channel, since):
		remove_reactions_from_post(post)
		for reaction in post.get("metadata", {}).get("reactions", []):
			award_if_appropriate(reaction)


def handle_live():
	def ws_handler(_mmws, event_data):
		if event_data["broadcast"]["channel_id"] != channel:
			return

		if event_data["event"] == "reaction_added":
			award_if_appropriate(json.loads(event_data["data"]["reaction"]))
		elif event_data["event"] == "reaction_removed":
			retract_if_appropriate(json.loads(event_data["data"]["reaction"]))

	_ = mattermost.ws.MMws(ws_handler, mm, f"wss://{SERVER}/api/v4/websocket")
	while True:
		sleep(60 * 1000)


if clean:
	for _post in get_posts_for_channel(mm, channel, SINCE):
		remove_reactions_from_post(_post)

else:
	# Note: skipping this step and updating an existing file would be dangerous:
	# you would miss revocations that happened while not listening.
	handle_backlog(SINCE)

	if live:
		print("Now watching for live posts.", file=sys.stderr)
		handle_live()

	else:
		print("Use --live to keep watching new posts.", file=sys.stderr)


# Logout
if not TOKEN:
	mm.revoke_user_session()