Allow for prompt caching to work by using baibot_conversation_start_time_utc instead of baibot_now_utc

This patch introduces a new `baibot_conversation_start_time_utc`
variable which indicates the time the conversation got started.

Using `baibot_now_utc` is still possible, but given that the current
time is a moving target, its use is in conflict with prompt caching.

Because the new `baibot_conversation_start_time_utc` prompt variable
is a more reasonable default, we're now using it in all sample configs.

src/conversation/llm/entity.rs

@@ -1,3 +1,5 @@
+use chrono::{DateTime, Utc};
+
 #[derive(Debug, Clone, PartialEq)]
 pub enum Author {
     Prompt,
@@ -9,6 +11,7 @@ pub enum Author {
 pub struct Message {
     pub author: Author,
     pub message_text: String,
+    pub timestamp: DateTime<Utc>,
 }
 
 #[derive(Debug)]
@@ -52,39 +55,59 @@ impl Conversation {
             messages: new_messages,
         }
     }
+
+    pub fn start_time(&self) -> Option<DateTime<Utc>> {
+        self.messages.first().map(|message| message.timestamp)
+    }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use chrono::{TimeZone, Utc};
 
     #[test]
     fn combine_consecutive_messages() {
+        let timestamp_1 = Utc.with_ymd_and_hms(2024, 9, 20, 18, 34, 15).unwrap();
+
+        let timestamp_2 = Utc.with_ymd_and_hms(2024, 9, 21, 18, 34, 15).unwrap();
+
+        let timestamp_3 = Utc.with_ymd_and_hms(2024, 9, 22, 18, 34, 15).unwrap();
+
         let conversation = Conversation {
             messages: vec![
+                // User's turn
                 Message {
                     author: Author::User,
                     message_text: "Hello".to_string(),
+                    timestamp: timestamp_1,
                 },
                 Message {
                     author: Author::User,
                     message_text: "How are you?".to_string(),
+                    timestamp: timestamp_2,
                 },
                 Message {
                     author: Author::User,
                     message_text: "I'm OK, btw.".to_string(),
+                    timestamp: timestamp_3,
                 },
+                // Assistant's turn
                 Message {
                     author: Author::Assistant,
                     message_text: "Hi there!".to_string(),
+                    timestamp: timestamp_2,
                 },
                 Message {
                     author: Author::Assistant,
                     message_text: "I'm doing well, thank you.".to_string(),
+                    timestamp: timestamp_3,
                 },
+                // User's turn
                 Message {
                     author: Author::User,
                     message_text: "That's great!".to_string(),
+                    timestamp: timestamp_3,
                 },
             ],
         };
@@ -97,12 +120,17 @@ mod tests {
             conversation.messages[0].message_text,
             "Hello\nHow are you?\nI'm OK, btw."
         );
+        assert_eq!(conversation.messages[0].timestamp, timestamp_1);
+
         assert_eq!(conversation.messages[1].author, Author::Assistant);
         assert_eq!(
             conversation.messages[1].message_text,
             "Hi there!\nI'm doing well, thank you."
         );
+        assert_eq!(conversation.messages[1].timestamp, timestamp_2);
+
         assert_eq!(conversation.messages[2].author, Author::User);
         assert_eq!(conversation.messages[2].message_text, "That's great!");
+        assert_eq!(conversation.messages[2].timestamp, timestamp_3);
     }
 }

src/conversation/llm/tests.rs

@@ -15,6 +15,7 @@ fn test_messages_by_the_bot_are_identified_correctly() {
         message_type: super::super::matrix::MatrixMessageType::Text,
         message_text: "Hello!".to_owned(),
         mentioned_users: vec![],
+        timestamp: chrono::Utc::now(),
     };
 
     let llm_message = convert_matrix_message_to_llm_message(&matrix_message, &bot_user_id).unwrap();
@@ -39,6 +40,7 @@ fn test_notice_messages_by_bot_with_speech_to_text_prefix_are_cleaned_up_and_con
         message_type: super::super::matrix::MatrixMessageType::Notice,
         message_text,
         mentioned_users: vec![],
+        timestamp: chrono::Utc::now(),
     };
 
     let llm_message = convert_matrix_message_to_llm_message(&matrix_message, &bot_user_id).unwrap();
@@ -62,6 +64,7 @@ fn test_notice_error_messages_by_bot_are_ignored() {
         message_type: super::super::matrix::MatrixMessageType::Notice,
         message_text,
         mentioned_users: vec![],
+        timestamp: chrono::Utc::now(),
     };
 
     let llm_message = convert_matrix_message_to_llm_message(&matrix_message, &bot_user_id);
@@ -86,6 +89,7 @@ fn test_other_notice_messages_by_the_bot_are_ignored() {
         message_type: super::super::matrix::MatrixMessageType::Notice,
         message_text: message_text.to_owned(),
         mentioned_users: vec![],
+        timestamp: chrono::Utc::now(),
     };
 
     let llm_message = convert_matrix_message_to_llm_message(&matrix_message, &bot_user_id);

src/conversation/llm/tokenization.rs

@@ -86,6 +86,7 @@ pub mod test {
         let message = super::Message {
             author: super::Author::User,
             message_text: "Hello there!".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
 
         let tokens = super::calculate_token_size_for_message(&bpe, model, &message);
@@ -104,6 +105,7 @@ pub mod test {
         let prompt = super::Message {
             author: super::Author::Prompt,
             message_text: "You are a bot!".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let prompt_length = 10;
 
@@ -117,6 +119,7 @@ pub mod test {
         let first = super::Message {
             author: super::Author::User,
             message_text: "Hello there!".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let first_length = 8;
 
@@ -130,6 +133,7 @@ pub mod test {
         let second = super::Message {
             author: super::Author::Assistant,
             message_text: "Hello!".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let second_length = 7;
 
@@ -144,6 +148,7 @@ pub mod test {
             author: super::Author::User,
             message_text: "This is the 3rd message in this conversation. It shall be preserved."
                 .to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let third_length = 21;
 
@@ -157,6 +162,7 @@ pub mod test {
         let forth = super::Message {
             author: super::Author::Assistant,
             message_text: "This is yet another message that shall be preserved.".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let forth_length = 15;
 
@@ -201,6 +207,7 @@ pub mod test {
         let prompt = super::Message {
             author: super::Author::User,
             message_text: "あなたはボットです。".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let prompt_length = 14;
 
@@ -214,6 +221,7 @@ pub mod test {
         let first = super::Message {
             author: super::Author::User,
             message_text: "こんにちは!".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let first_length = 7;
 
@@ -227,6 +235,7 @@ pub mod test {
         let second = super::Message {
             author: super::Author::Assistant,
             message_text: "こんにちは。今日は元気ですか。".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let second_length = 15;
 
@@ -240,6 +249,7 @@ pub mod test {
         let third = super::Message {
             author: super::Author::User,
             message_text: "これは第3のメッセージなので、保存されます。".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let third_length = 22;
 
@@ -253,6 +263,7 @@ pub mod test {
         let forth = super::Message {
             author: super::Author::Assistant,
             message_text: "これはもう一つの保存されますメッセージです。".to_owned(),
+            timestamp: chrono::Utc::now(),
         };
         let forth_length = 21;
 

src/conversation/llm/utils.rs

@@ -17,19 +17,30 @@ pub fn convert_matrix_message_to_llm_message(
 
 fn convert_bot_message(matrix_message: &MatrixMessage) -> Option<Message> {
     match matrix_message.message_type {
-        MatrixMessageType::Text => convert_bot_text_message(&matrix_message.message_text),
-        MatrixMessageType::Notice => convert_bot_notice_message(&matrix_message.message_text),
+        MatrixMessageType::Text => {
+            convert_bot_text_message(&matrix_message.message_text, &matrix_message.timestamp)
+        }
+        MatrixMessageType::Notice => {
+            convert_bot_notice_message(&matrix_message.message_text, &matrix_message.timestamp)
+        }
     }
 }
 
-fn convert_bot_text_message(text: &str) -> Option<Message> {
+fn convert_bot_text_message(
+    text: &str,
+    timestamp: &chrono::DateTime<chrono::Utc>,
+) -> Option<Message> {
     Some(Message {
         author: Author::Assistant,
         message_text: text.to_owned(),
+        timestamp: timestamp.to_owned(),
     })
 }
 
-fn convert_bot_notice_message(text: &str) -> Option<Message> {
+fn convert_bot_notice_message(
+    text: &str,
+    timestamp: &chrono::DateTime<chrono::Utc>,
+) -> Option<Message> {
     // Notice messages sent by the bot are usually transcriptions of previous messages sent by the user.
     // Such transcriptions are prefixed with an emoji and blockquoted.
     // If we find a notice that doesn't match this pattern, we skip it.
@@ -42,6 +53,7 @@ fn convert_bot_notice_message(text: &str) -> Option<Message> {
         return Some(Message {
             author: Author::User,
             message_text: text.to_owned(),
+            timestamp: timestamp.to_owned(),
         });
     }
 
@@ -52,5 +64,6 @@ fn convert_user_message(matrix_message: &MatrixMessage) -> Option<Message> {
     Some(Message {
         author: Author::User,
         message_text: matrix_message.message_text.clone(),
+        timestamp: matrix_message.timestamp.to_owned(),
     })
 }