#!/usr/bin/env python3

import sys
import argparse
import os
from collections import defaultdict
import datetime
from time import sleep
import time
import json
from typing import Dict, Set, Generator, Optional, NamedTuple
import mattermost
import mattermost.ws
import re


class NotFound(Exception):
	def __init__(self, type_: str, name: str):
		super().__init__(f"{type_} {name} not found")
		self.type = type_
		self.name = name


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


def yes_no(x):
	return "yes" if x else "no"


def get_posts_for_channel(self, channel_id: str, progress=lambda x: None, **kwargs) -> Generator[Dict, None, None]:
	"""
	@raises ApiException: Passed on from lower layers.
	"""
	page = 0
	posts = []

	while True:
		data_page = self._get(f"/v4/channels/{channel_id}/posts", params={"page":str(page), "per_page":200, **kwargs})

		if data_page["order"] == []:
			break
		page += 1

		posts.extend(data_page["posts"][order] for order in data_page["order"])
		progress(len(posts))
		sleep(0.1)

	# Mattermost gives newest first, so reverse order
	posts.reverse()

	return posts



ID_PREFIX = "id:"

def predicate_for_query(query: str):
	"""
	@return: a function that returns whether `query` matches its argument
	"""
	if query.startswith(ID_PREFIX):
		id_ = query[len(ID_PREFIX):]
		return lambda x: x["id"] == id_
	else:
		return lambda x: x["name"] == query


def resolve_team(mm_api: mattermost.MMApi, query: str) -> Optional[Dict]:
	return first(filter(
		predicate_for_query(query),
		mm_api.get_teams()
	))


def resolve_channel(mm_api: mattermost.MMApi, team_id: str, query: str) -> Optional[Dict]:
	return first(filter(
		predicate_for_query(query),
		mm_api.get_team_channels(team_id)
	))


def resolve_team_channel(mm_api: mattermost.MMApi, query: str) -> Dict:
	query_parts = query.split("/")
	del query
	if len(query_parts) != 2:
		raise ValueError("Team/channel ID should be '<team>/<channel>'")

	team = resolve_team(mm_api, query_parts[0])
	if not team:
		raise NotFound("team", query_parts[0])

	channel = resolve_channel(mm_api, team["id"], query_parts[1])
	if not channel:
		return NotFound("channel", query_parts[1])

	return team, channel


def login(mm_api, parsed):
	print(
		f"Logging in as {parsed.user}; password provided: {yes_no(parsed.password)}; "
		f"TOTP token provided: {yes_no(parsed.totp)}",
		file=sys.stderr)
	mm_api.login(parsed.user, parsed.password, parsed.totp)

	if parsed.format == "json":
		print(json.dumps({"token": mm_api._bearer}))
	elif parsed.format == "tsv":
		print(mm_api._bearer)
	else:
		assert False


def cat(mm_api: mattermost.MMApi, parsed):

	channels = [
		resolve_team_channel(mm_api, query)
		for query in parsed.channels
	]

	users = list(mm_api.get_users())

	for team, channel in channels:
		if not parsed.ids:
			def attribute(key_value):
				key, value = key_value
				if key == "channel_id":
					assert value == channel["id"]
					return "channel", channel["name"]
				if key == "user_id":
					return "username", first(u["username"] for u in users if u["id"] == value)
				return key_value
		else:
			def attribute(key_value):
				return key_value

		posts = get_posts_for_channel(mm_api, channel["id"], after=parsed.after)
		for post in posts:
			print(post_str(attribute, post, parsed))


def send(mm_api: mattermost.MMApi, parsed):
	read_stdin = parsed.message is None or parsed.channel is None

	team, channel = resolve_team_channel(mm_api, parsed.channel) if parsed.channel is not None else (None, None)

	if read_stdin:
		if sys.stdin.isatty():
			print("Reading from tty. (You can type the message objects below. Or maybe you meant to redirect something to stdin.)", file=sys.stderr)

		for line in sys.stdin:
			msg = json.loads(line)

			if "channel_id" in msg:
				channel_id = msg["channel_id"]
			elif "channel" in msg:
				_, local_channel = resolve_team_channel(mm_api, msg["channel"])
				channel_id = local_channel["id"]
			elif channel is not None:
				channel_id = channel["id"]
			else:
				print(f"Illegal message, missing channel: {line.strip()}", file=sys.stderr)
				raise ValueError("Illegal message, missing channel")

			sent = mm_api.create_post(channel_id, msg["message"], props={"from_mmcli": "true"}, filepaths=msg.get("attachments", msg.get("attachments")))
			print(sent)

	else:
		sent = mm_api.create_post(channel["id"], parsed.message, props={"from_mmcli": "true"}, filepaths=parsed.attach)
		print(sent)


def post_str(attribute, post, parsed):
	obj = {
		k: v
		for k, v in map(attribute, post.items())
		if (v or k == "message") and (k != "update_at" or post["update_at"] != post["create_at"])
	}

	if parsed.format == "json":
		return json.dumps(obj)
	if parsed.format == "tsv":
		msg = obj.get("message", "").replace("\\", "\\\\").replace("\t", r"\t").replace("\n", r"\n")
		return f"{obj['id']}\t{obj['create_at']}\t{obj.get('username') or obj['user_id']}\t{msg}"
	assert False


ACTIONS = {
	"login": {"function": login, "accesstoken_required": False},
	"cat": {"function": cat},
	"send": {"function": send},
}

FORMATTERS = { "json", "tsv" }

ENVVAR_SERVER = "MM_SERVER"
ENVVAR_USERNAME = "MM_USERNAME"
ENVVAR_PASSWORD = "MM_PASSWORD"
ENVVAR_TOTP = "MM_TOTP"
ENVVAR_ACCESSTOKEN = "MM_ACCESSTOKEN"

def main():
	prog_name = os.path.basename(sys.argv[0])
	description = "Interact with Mattermost on the CLI"
	epilog = f"""
For further help, use `{prog_name} <action> -h`.

Where a "URL name" is required, "id:" plus an ID can also be used instead. So these could both be valid:
  town-square
  id:123abc456def789ghi012jkl34

Hint: JSON output can be filtered on the command line with jq(1).
	""".strip()

	argparser = argparse.ArgumentParser(
		prog_name, description=description, epilog=epilog,
		formatter_class=argparse.RawTextHelpFormatter
	)
	argparser.add_argument("-i", "--ids", help="use IDs instead of names", action="store_true")
	argparser.add_argument(
		"--format", help="output format; only json has all fields; default: json", choices=FORMATTERS, default="json")

	argparser.add_argument(
		"--server",
		help="e.g.: mattermost.example.org; example.org/mattermost; envvar: {ENVVAR_SERVER}",
		default=os.getenv(ENVVAR_SERVER))

	subparsers = argparser.add_subparsers(title="actions", dest="action", required=True)

	parser_login = subparsers.add_parser("login", help="retrieve an access token")
	parser_login.add_argument("login_id", help="username or email", default=os.getenv(ENVVAR_USERNAME))
	parser_login.add_argument("--password", default=os.getenv(ENVVAR_PASSWORD))
	parser_login.add_argument("--totp", default=os.getenv(ENVVAR_TOTP))

	# TODO support multiple channels
	# parser_cat = subparsers.add_parser("cat", help="list messages in channel(s)")
	# parser_cat.add_argument(
		# "channels", nargs="+", help="URL names of team and channel: '<team>/<channel>'")
	parser_cat = subparsers.add_parser("cat", help="list messages in channel")
	parser_cat.add_argument("channel", help="URL names of team and channel: '<team>/<channel>'")
	# ---
	parser_cat.add_argument("--after", help="all after post with ID")
	parser_cat.add_argument("--since", help="all after timestamp")
	parser_cat.add_argument("-f", "--follow", help="keep running, printing new posts as they come in")

	parser_send = subparsers.add_parser("send", help="send message(s)")
	parser_send.add_argument(
		"--channel", help="URL names of team and channel: '<team>/<channel>'; if not provided, "
		"messages must be provided on stdin and each must specify channel")
	parser_send.add_argument(
		"--message", help="message; if not provided, messages will be expected on stdin")
	parser_send.add_argument(
		"--attach", nargs="+", help="filename of file to attach")

	parsed = argparser.parse_args()

	if not parsed.server:
		argparser.error(
			f"server is required; use argument --server or environment variable {ENVVAR_SERVER}")

	access_token = os.getenv(ENVVAR_ACCESSTOKEN)
	if ACTIONS[parsed.action].get("accesstoken_required", True) and not access_token:
		argparser.error(
			f"`{prog_name} {parsed.action}` requires access token; get one with `{prog_name} login` "
			f"and set environment variable {ENVVAR_ACCESSTOKEN}")

	mm_api = mattermost.MMApi(f"https://{parsed.server}/api")
	if access_token:
		mm_api._headers.update({"Authorization": f"Bearer {access_token}"})

	ACTIONS[parsed.action]["function"](mm_api, parsed)


if __name__ == "__main__":
	main()