Allow the bot to prioritize playing against humans or bots (#979)

Allow the bot to prioritize playing against humans or bots. For example, if someone changes preference to human and has sort_by set to best, then the bot will prefer to play with a human even if they are rated lower than a bot. The order of opponents will be:

HUMAN A (2100)
HUMAN B (1800)
HUMAN C (1500)
BOT A (3000)
BOT B (2500)

config.yml.default

@@ -127,6 +127,7 @@ correspondence:
 challenge:                         # Incoming challenges.
   concurrency: 1                   # Number of games to play simultaneously.
   sort_by: "best"                  # Possible values: "best" and "first".
+  preference: "none"               # Possible values: "none", "human", "bot".
   accept_bot: true                 # Accepts challenges coming from other bots.
   only_bot: false                  # Accept challenges by bots only.
   max_increment: 20                # Maximum amount of increment to accept a challenge in seconds. The max is 180. Set to 0 for no increment.

lib/config.py

@@ -196,6 +196,7 @@ def insert_default_values(CONFIG: CONFIG_DICT_TYPE) -> None:
     set_config_default(CONFIG, "engine", "polyglot", key="min_weight", default=1)
     set_config_default(CONFIG, "challenge", key="concurrency", default=1)
     set_config_default(CONFIG, "challenge", key="sort_by", default="best")
+    set_config_default(CONFIG, "challenge", key="preference", default="none")
     set_config_default(CONFIG, "challenge", key="accept_bot", default=False)
     set_config_default(CONFIG, "challenge", key="only_bot", default=False)
     set_config_default(CONFIG, "challenge", key="max_increment", default=180)
@@ -289,6 +290,10 @@ def validate_config(CONFIG: CONFIG_DICT_TYPE) -> None:
             config_assert(online_section.get("move_quality") != "suggest" or not online_section.get("enabled"),
                           f"XBoard engines can't be used with `move_quality` set to `suggest` in {subsection}.")
 
+    config_assert(CONFIG["challenge"]["sort_by"] in ["best", "first"], "challenge.sort_by can be either `first` or `best`.")
+    config_assert(CONFIG["challenge"]["preference"] in ["none", "human", "bot"],
+                  "challenge.preference should be `none`, `human`, or `bot`.")
+
     pgn_directory = CONFIG["pgn_directory"]
     in_docker = os.environ.get("LICHESS_BOT_DOCKER")
     config_warn(not pgn_directory or not in_docker, "Games will be saved to '{}', please ensure this folder is in a mounted "

lichess-bot.py

@@ -489,12 +489,15 @@ def sort_challenges(challenge_queue: MULTIPROCESSING_LIST_TYPE, challenge_config
     Sort the challenges.
 
     They can be sorted either by rating (the best challenger is accepted first),
-    or by time (the first challenger is accepted first).
+    or by time (the first challenger is accepted first). The bot can also
+    prioritize playing against humans or bots.
     """
+    challenge_list = list(challenge_queue)
     if challenge_config.sort_by == "best":
-        list_c = list(challenge_queue)
-        list_c.sort(key=lambda c: -c.score())
-        challenge_queue[:] = list_c
+        challenge_list.sort(key=lambda challenger: challenger.score(), reverse=True)
+    if challenge_config.preference != "none":
+        challenge_list.sort(key=lambda challenger: challenger.challenger.is_bot, reverse=challenge_config.preference == "bot")
+    challenge_queue[:] = challenge_list
 
 
 def game_is_active(li: LICHESS_TYPE, game_id: str) -> bool:

wiki/Configure-lichess-bot.md

@@ -154,6 +154,7 @@ will precede the `go` command to start thinking with `sd 5`. The other `go_comma
 - `challenge`: Control what kind of games for which the bot should accept challenges. All of the following options must be satisfied by a challenge to be accepted.
   - `concurrency`: The maximum number of games to play simultaneously.
   - `sort_by`: Whether to start games by the best rated/titled opponent `"best"` or by first-come-first-serve `"first"`.
+  - `preference`: Whether to prioritize human opponents, bot opponents, or treat them equally.
   - `accept_bot`: Whether to accept challenges from other bots.
   - `only_bot`: Whether to only accept challenges from other bots.
   - `max_increment`: The maximum value of time increment.