Save followers and followings to a cache file and remember users that were suggested.

Also fix bug that always suggested the first user in the list of followers.

README.md

@@ -25,8 +25,6 @@ For example, to get the numeric id for the account @chuso@mastodon.social: https
 
 Planned features that may be implemented, or may not, depending on when I lose interest on this:
 
-* Remember which users were already suggested so they are not repeated.
-* Cache followers and followings so we don't need to download them from the server every time.
 * Try to guess when the cache needs to be updated.
 * Optionally return more than one user.
 * Proper configuration support.

mastoroulette.py

@@ -2,10 +2,16 @@
 
 # SPDX-License-Identifier: Artistic-2.0
 
+from argparse import ArgumentParser
+from appdirs import user_cache_dir
+from datetime import datetime
+import json
+import os
 from random import shuffle
 from requests import get
 from requests.utils import parse_header_links
-from sys import exit
+from sys import stderr, exit
+from urllib.parse import urlparse
 
 # Configuration (the required user id is the numeric one)
 INSTANCE = ''
@@ -17,6 +23,12 @@ BEARER = ""
 # USER = '206178'
 # BEARER = "aV8bTnC2xR3eG7sH6mF1kP0lY9jI4wDqZoXnS2cRGwq"
 
+# Set cache file path
+cache_file = os.path.join(
+    user_cache_dir("mastoroulette"),
+    "{}@{}.json".format(USER, urlparse(INSTANCE).netloc)
+)
+
 
 # Function to retrieve API results when they are paginated
 def get_paged_results(url):
@@ -45,9 +57,37 @@ def get_paged_results(url):
     return results
 
 
-# Retrieve lists of followers and followings
-followers = get_paged_results(f'{INSTANCE}/api/v1/accounts/{USER}/followers')
-followings = get_paged_results(f'{INSTANCE}/api/v1/accounts/{USER}/following')
+# Build arguments list and parse current arguments
+parser = ArgumentParser(
+    description="Suggests Mastodon users to follow among the followers you don't follow.",
+    epilog="https://git.chuso.net/chuso/mastoroulette")
+parser.add_argument("-u", "--update-cache",
+                    action="store_true", help="Update the cache")
+args = parser.parse_args()
+
+# A forced update was not requested
+if not args.update_cache:
+    try:
+        # Try to load data from the cache file
+        with open(cache_file, "r") as f:
+            cache = json.load(f)
+        followers = cache["followers"]
+        followings = cache["followings"]
+        suggested = cache["suggested"]
+        print("Using cache last updated on {}".format(datetime.fromtimestamp(os.path.getmtime(cache_file))))
+    except Exception as e:
+        # If opening the cache file failed, we reset args.update_cache to True
+        # as if an update was requested, because we do need to run an update
+        # when the cache file is not available
+        print("Ignoring cache, failed to open: {}".format(str(e)), file=stderr)
+        args.update_cache = True
+        suggested = []
+
+# An update was requested (either manually or because the cache file is unavailable)
+if args.update_cache:
+    # Retrieve lists of followers and followings
+    followers = get_paged_results(f'{INSTANCE}/api/v1/accounts/{USER}/followers')
+    followings = get_paged_results(f'{INSTANCE}/api/v1/accounts/{USER}/following')
 
 # Shuffle followers list
 shuffle(followers)
@@ -59,5 +99,18 @@ for f in followers:
     if [u for u in followings if u["uri"] == f["uri"]]:
         continue
 
-    print(followers[0]["url"])
+    print(f["url"])
+
+    # Add the new suggested account to the list of users that were
+    # already suggested and write all data to the cache
+    suggested.append(f["id"])
+
+    os.makedirs(os.path.dirname(cache_file), 0o700, True)
+    with open(cache_file, "w") as f:
+        json.dump({
+            "followers": followers,
+            "followings": followings,
+            "suggested": suggested
+        }, f)
+
     break