refactor(chat_gpt): decompose the two large handlers (#607)

Splits the ~80-line handle_chat_gpt_question and ~60-line handle_reply
into small, single-purpose helpers (§4):
- `bot_configuration_for_message` / `bot_configuration_for_profile`:
  pure profile-selection functions, now covered by unit tests.
- `build_question_context`: the summary-vs-rolling context routing.
- `send_gpt_reply`: thread-aware reply send (used by the question path).

handle_reply is additionally flattened from `if let Ok { .. }` to a
`let Ok(..) else { return Ok(()) }` guard. Its send stays non-threaded
to preserve exact current behavior.

Pure refactor — no happy-path behavior change (chat_gpt_e2e is the
backstop). 3 new unit tests; local gate green (fmt, clippy -D warnings,
11 unit tests, integration tests compile).

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: nolik

src/chat_gpt_handler.rs

@@ -10,7 +10,7 @@ use redis::aio::ConnectionManager;
 use regex::Regex;
 use serde::{Deserialize, Serialize};
 use teloxide::prelude::*;
-use teloxide::types::ReplyParameters;
+use teloxide::types::{MessageId, ReplyParameters, ThreadId};
 use teloxide::RequestError;
 
 const FEDOR_CHAT_GPT_SYSTEM_CONTEXT: &str = "Предоставь грубый ответ. \
@@ -76,55 +76,37 @@ pub async fn handle_chat_gpt_question(
         return Ok(());
     };
     info!("gpt invocation: chat_id: {chat_id}, message: {message}");
-    let bot_profiles = &*BOT_PROFILES;
-    let bot_configuration = bot_profiles
-        .iter()
-        .find(|&x| x.is_correct_config(message))
-        .unwrap_or(&bot_profiles[0]);
-    let bot_context_key = &format!("{:#?}:chat:{:#?}", bot_configuration.profile, chat_id.0);
+
+    let bot_configuration = bot_configuration_for_message(message);
+    let bot_context_key = format!("{:#?}:chat:{:#?}", bot_configuration.profile, chat_id.0);
     let user_message = ChatMessage {
         role: User,
         content: message.to_string(),
     };
-    let summary_request_regex = &*CHAT_SUMMARY_REQUEST_REGEX;
     let mut redis_cm = gpt_parameters.redis_connection_manager.clone();
-    let context = match summary_request_regex.is_match(message) {
-        true => {
-            fetch_chat_summary_context(
-                &mut redis_cm,
-                chat_id.0,
-                &user_message,
-                bot_configuration.gpt_system_context,
-            )
-            .await
-        }
-        false => {
-            fetch_bot_context(
-                &mut redis_cm,
-                bot_context_key,
-                &user_message,
-                bot_configuration.gpt_system_context,
-            )
-            .await
-        }
-    };
+    let context = build_question_context(
+        &mut redis_cm,
+        chat_id,
+        &bot_context_key,
+        &user_message,
+        bot_configuration,
+    )
+    .await;
 
     let gpt_response_message = gpt_service::chat_gpt_call(gpt_parameters, chat_id, context).await;
-    let bot_reply_msg_response = if let Some(thread_id) = msg.thread_id {
-        bot.send_message(chat_id, &gpt_response_message.content)
-            .reply_parameters(ReplyParameters::new(msg.id))
-            .message_thread_id(thread_id)
-            .await
-    } else {
-        bot.send_message(chat_id, &gpt_response_message.content)
-            .reply_parameters(ReplyParameters::new(msg.id))
-            .await
-    };
+    let bot_reply_msg_response = send_gpt_reply(
+        &bot,
+        chat_id,
+        msg.id,
+        msg.thread_id,
+        &gpt_response_message.content,
+    )
+    .await;
 
     update_bot_context_and_identifiers(
         &mut redis_cm,
         bot_configuration.profile,
-        bot_context_key,
+        &bot_context_key,
         &user_message,
         &gpt_response_message,
         bot_reply_msg_response,
@@ -133,6 +115,72 @@ pub async fn handle_chat_gpt_question(
     Ok(())
 }
 
+/// Pick the bot profile whose mention regex matches the message, falling back
+/// to the first profile when none match.
+fn bot_configuration_for_message(message: &str) -> &'static BotConfiguration<'static> {
+    let bot_profiles = &*BOT_PROFILES;
+    bot_profiles
+        .iter()
+        .find(|&config| config.is_correct_config(message))
+        .unwrap_or(&bot_profiles[0])
+}
+
+/// Look up the bot profile a previous bot message was sent under, falling back
+/// to the first profile when it is unknown.
+fn bot_configuration_for_profile(profile: BotProfile) -> &'static BotConfiguration<'static> {
+    let bot_profiles = &*BOT_PROFILES;
+    bot_profiles
+        .iter()
+        .find(|&config| config.profile == profile)
+        .unwrap_or(&bot_profiles[0])
+}
+
+/// Build the GPT context for a fresh question: a chat-history summary when the
+/// message asks "what's going on", otherwise the profile's rolling context.
+async fn build_question_context(
+    redis_cm: &mut ConnectionManager,
+    chat_id: ChatId,
+    bot_context_key: &String,
+    user_message: &ChatMessage,
+    bot_configuration: &BotConfiguration<'_>,
+) -> Vec<ChatMessage> {
+    if CHAT_SUMMARY_REQUEST_REGEX.is_match(&user_message.content) {
+        fetch_chat_summary_context(
+            redis_cm,
+            chat_id.0,
+            user_message,
+            bot_configuration.gpt_system_context,
+        )
+        .await
+    } else {
+        fetch_bot_context(
+            redis_cm,
+            bot_context_key,
+            user_message,
+            bot_configuration.gpt_system_context,
+        )
+        .await
+    }
+}
+
+/// Send a bot reply, routing it into the originating message thread when there
+/// is one.
+async fn send_gpt_reply(
+    bot: &Bot,
+    chat_id: ChatId,
+    reply_to: MessageId,
+    thread_id: Option<ThreadId>,
+    content: &str,
+) -> Result<Message, RequestError> {
+    let request = bot
+        .send_message(chat_id, content.to_owned())
+        .reply_parameters(ReplyParameters::new(reply_to));
+    match thread_id {
+        Some(thread_id) => request.message_thread_id(thread_id).await,
+        None => request.await,
+    }
+}
+
 async fn update_bot_context_and_identifiers(
     redis_connection_manager: &mut ConnectionManager,
     bot_profile: BotProfile,
@@ -182,51 +230,48 @@ pub async fn handle_reply(
     info!("chat_key: {chat_key:?}");
     let reply_msg_id = reply_msg.id.0;
     let mut redis_cm = gpt_parameters.redis_connection_manager.clone();
-    if let Ok(reply_msg_bot_profile) =
+    let Ok(reply_msg_bot_profile) =
         chat_repository::get_bot_msg_profile(&mut redis_cm, chat_key, reply_msg_id).await
-    {
-        info!(
-            "handle msg of bot msg reply_msg_id:'{reply_msg_id:#?}' under bot profile:'{reply_msg_bot_profile:#?}'"
-        );
-        info!(
-            "truing to reply chat_id:{chat_id:#?}, msg_id: {:?}, thread_id: {:#?}",
-            msg.id, msg.thread_id
-        );
-        let bot_profiles = &*BOT_PROFILES;
-        let bot_configuration = bot_profiles
-            .iter()
-            .find(|&x| x.profile == reply_msg_bot_profile)
-            .unwrap_or(&bot_profiles[0]);
-        let bot_context_key = &format!("{:#?}:chat:{:#?}", bot_configuration.profile, chat_id.0);
-        let user_message = ChatMessage {
-            role: User,
-            content: message.to_string(),
-        };
-        let context = fetch_bot_context(
-            &mut redis_cm,
-            bot_context_key,
-            &user_message,
-            bot_configuration.gpt_system_context,
-        )
-        .await;
+    else {
+        return Ok(());
+    };
+    info!(
+        "handle msg of bot msg reply_msg_id:'{reply_msg_id:#?}' under bot profile:'{reply_msg_bot_profile:#?}'"
+    );
+    info!(
+        "truing to reply chat_id:{chat_id:#?}, msg_id: {:?}, thread_id: {:#?}",
+        msg.id, msg.thread_id
+    );
 
-        let gpt_response_message =
-            gpt_service::chat_gpt_call(gpt_parameters, chat_id, context).await;
-        let bot_reply_msg_response = bot
-            .send_message(chat_id, &gpt_response_message.content)
-            .reply_parameters(ReplyParameters::new(msg.id))
-            .await;
+    let bot_configuration = bot_configuration_for_profile(reply_msg_bot_profile);
+    let bot_context_key = format!("{:#?}:chat:{:#?}", bot_configuration.profile, chat_id.0);
+    let user_message = ChatMessage {
+        role: User,
+        content: message.to_string(),
+    };
+    let context = fetch_bot_context(
+        &mut redis_cm,
+        &bot_context_key,
+        &user_message,
+        bot_configuration.gpt_system_context,
+    )
+    .await;
 
-        update_bot_context_and_identifiers(
-            &mut redis_cm,
-            bot_configuration.profile,
-            bot_context_key,
-            &user_message,
-            &gpt_response_message,
-            bot_reply_msg_response,
-        )
+    let gpt_response_message = gpt_service::chat_gpt_call(gpt_parameters, chat_id, context).await;
+    let bot_reply_msg_response = bot
+        .send_message(chat_id, &gpt_response_message.content)
+        .reply_parameters(ReplyParameters::new(msg.id))
         .await;
-    }
+
+    update_bot_context_and_identifiers(
+        &mut redis_cm,
+        bot_configuration.profile,
+        &bot_context_key,
+        &user_message,
+        &gpt_response_message,
+        bot_reply_msg_response,
+    )
+    .await;
     Ok(())
 }
 
@@ -300,6 +345,7 @@ pub enum BotProfile {
 
 #[cfg(test)]
 mod tests {
+    use super::{bot_configuration_for_message, bot_configuration_for_profile, BotProfile};
     use crate::chat_gpt_handler::SUMMARY_REQUEST_REGEX;
     use regex::Regex;
 
@@ -311,4 +357,36 @@ mod tests {
         assert!(summary_regex.is_match("Фёдор, что тут происходит?"));
         assert!(!summary_regex.is_match("Fedor, kak dela?"));
     }
+
+    #[test]
+    fn bot_configuration_for_message_selects_by_mention() {
+        assert_eq!(
+            bot_configuration_for_message("привет fedor").profile,
+            BotProfile::Fedor
+        );
+        assert_eq!(
+            bot_configuration_for_message("а вот и феликс").profile,
+            BotProfile::Felix
+        );
+        assert_eq!(
+            bot_configuration_for_message("ferris the crab").profile,
+            BotProfile::Ferris
+        );
+    }
+
+    #[test]
+    fn bot_configuration_for_message_defaults_to_first_profile() {
+        // No mention keyword -> first configured profile (Fedor).
+        assert_eq!(
+            bot_configuration_for_message("nothing relevant here").profile,
+            BotProfile::Fedor
+        );
+    }
+
+    #[test]
+    fn bot_configuration_for_profile_round_trips() {
+        for profile in [BotProfile::Fedor, BotProfile::Felix, BotProfile::Ferris] {
+            assert_eq!(bot_configuration_for_profile(profile).profile, profile);
+        }
+    }
 }