Account for quirks in GET /channels/.../posts

mmcli.py

@@ -4,7 +4,7 @@ import sys
 import argparse
 import os
 import json
-from typing import Dict, Optional, List
+from typing import Dict, Optional, List, Iterable
 import re
 from time import sleep
 import threading
@@ -38,28 +38,73 @@ def http_to_ws(url):
 	return "ws" + url[4:]
 
 
-def get_posts_for_channel(self, channel_id: str, progress=lambda x: None, **kwargs) -> List[Dict]:
+def get_posts_for_channel(self, channel_id: str, progress=lambda x: None, after=None, since=None, **kwargs) -> Iterable[Dict]:
 	"""
 	@raises ApiException: Passed on from lower layers.
 	"""
+	per_page = 200
 	page = 0
-	posts = []
+	total = 0
 
-	while True:
-		data_page = self._get(f"/v4/channels/{channel_id}/posts", params={"page":str(page), "per_page":200, **kwargs})
+	# if after and since:
+		# raise ValueError("after and since cannot be used together")
 
-		if data_page["order"] == []:
-			break
-		page += 1
+	if since:
+		raise Exception("'since' functionality is broken in the API and behaves non-deterministically. It cannot be meaningfully used.")
+		# Posts in channel updated after a given timestamp: pagination is broken in the API
+		# current_since = since
+		# while True:
+			# data_page = self._get(f"/v4/channels/{channel_id}/posts", params={"since": current_since, **kwargs})
+			# order = data_page["order"]
 
-		posts.extend(data_page["posts"][order] for order in data_page["order"])
-		progress(len(posts))
-		sleep(0.1)
+			# yield from (
+				# data_page["posts"][post_id]
+				# for post_id in reversed(order)
+			# )
+			# total += len(order)
+			# progress(total)
+			# if len(order) < 1000: # For some reason the pages go up to 1000 posts if 'since' is given
+				# break
+			# current_since = data_page["posts"][order[0]]["create_at"]
+			# sleep(0.1)
 
-	# Mattermost gives newest first, so reverse order
-	posts.reverse()
+	elif after:
+		# 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:
+			data_page = self._get(f"/v4/channels/{channel_id}/posts", params={"page": page, "per_page": per_page, "after": after, **kwargs})
+			order = data_page["order"]
 
-	return posts
+			yield from (
+				data_page["posts"][post_id]
+				for post_id in reversed(order)
+			)
+			total += len(order)
+			progress(total)
+			if len(order) < per_page:
+				break
+			page += 1
+			sleep(0.1)
+
+	else:
+		# All posts in channel: API gives pages with NEWEST messages first, so reverse the order in
+		# the end (and don't reverse the order of each page separately)
+		posts = []
+		while True:
+			data_page = self._get(f"/v4/channels/{channel_id}/posts", params={"page": page, "per_page": per_page, **kwargs})
+			order = data_page["order"]
+
+			posts.extend(
+				data_page["posts"][post_id]
+				for post_id in order
+			)
+			progress(len(posts))
+			if len(order) < per_page:
+				break
+			page += 1
+			sleep(0.1)
+
+		yield from reversed(posts)
 
 
 
@@ -150,7 +195,7 @@ def cat(mm_api: mattermost.MMApi, parsed):
 	backlog_lock = threading.Lock()
 
 	def print_initial_messages():
-		posts = get_posts_for_channel(mm_api, channel["id"], after=parsed.after)
+		posts = get_posts_for_channel(mm_api, channel["id"], after=parsed.after, since=parsed.since)
 		for post in posts:
 			print(str_for_post(attribute, post, parsed))