Fix regression

mmcli/mmcli.py

@@ -4,6 +4,7 @@ import sys
 import argparse
 import os
 import json
+import itertools
 from typing import Dict, Optional, List, Iterable, Tuple
 import re
 from time import sleep
@@ -50,7 +51,7 @@ def get_user_id(mm_api: mattermost.MMApi):
 	return mm_api._my_user_id
 
 
-def get_posts_for_channel(self, channel_id: str, progress=lambda x: None, after=None, **kwargs) -> Iterable[Dict]:
+def get_posts_for_channel(self, channel_id: str, progress=lambda x: None, after=None, maximum=None, **kwargs) -> Iterable[Dict]:
 	"""
 	@raises ApiException: Passed on from lower layers.
 	"""
@@ -59,6 +60,9 @@ def get_posts_for_channel(self, channel_id: str, progress=lambda x: None, after=
 	total = 0
 
 	if after:
+		if maximum is not None:
+			raise ValueError("after and maximum cannot be used together")
+
 		# Posts in channel after a given ID: API gives pages with OLDEST messages first, so we can
 		# yield each page when it is fetched
 		while True:
@@ -86,14 +90,19 @@ def get_posts_for_channel(self, channel_id: str, progress=lambda x: None, after=
 			data_page = self._get(f"/v4/channels/{channel_id}/posts", params={"page": page, "per_page": per_page, **kwargs})
 			order = data_page["order"]
 
-			posts.extend(
+			this_maximum = None if maximum is None else maximum - len(posts)
+
+			posts.extend(itertools.islice(
+				(
 					data_page["posts"][post_id]
 					for post_id in order
 					if post_id not in post_ids
-			)
+				),
+				this_maximum
+			))
 			post_ids |= set(order)
 			progress(len(posts))
-			if len(order) < per_page:
+			if len(order) < per_page or (maximum is not None and len(posts) >= maximum):
 				break
 			page += 1
 			sleep(0.1)
@@ -254,6 +263,8 @@ def cat(mm_api: mattermost.MMApi, cmdline_args):
 
 def tail(mm_api: mattermost.MMApi, cmdline_args):
 
+	desired_count = cmdline_args.number
+
 	team, channel = resolve_team_channel(mm_api, cmdline_args.channel)
 
 	if not cmdline_args.ids:
@@ -276,12 +287,7 @@ def tail(mm_api: mattermost.MMApi, cmdline_args):
 	backlog_lock = threading.Lock()
 
 	def print_initial_messages():
-		data_page = mm_api._get(f"/v4/channels/{channel['id']}/posts")
-		order = data_page["order"]
-		posts = [
-			data_page["posts"][post_id]
-			for post_id in reversed(order)
-		]
+		posts = get_posts_for_channel(mm_api, channel["id"], maximum=desired_count)
 
 		for post in posts:
 			print(str_for_post(attribute, post, cmdline_args))
@@ -616,6 +622,7 @@ Security note: Other programs and users can typically read which arguments you g
 	parser_tail = subparsers.add_parser("tail", help="list newest messages in channel")
 	parser_tail.add_argument("channel", help="URL names of team and channel: '<team>/<channel>'")
 	parser_tail.add_argument("-f", "--follow", action="store_true", help="keep running, printing new posts as they come in")
+	parser_tail.add_argument("-n", "--number", type=int, default=200, help="maximum amount of messages of backlog to fetch (when using with -f, new posts will be printed without limit)")
 
 	parser_ls = subparsers.add_parser("ls", help="list channels")
 	parser_ls.add_argument("team", help="URL name of team")