fn assert_conversation_state_invariants()

in crates/q_chat/src/conversation_state.rs [770:856]

• 83 lines of code
• 9 McCabe index (conditional complexity)

    fn assert_conversation_state_invariants(state: FigConversationState, assertion_iteration: usize) {
        if let Some(Some(msg)) = state.history.as_ref().map(|h| h.first()) {
            assert!(
                matches!(msg, ChatMessage::UserInputMessage(_)),
                "{assertion_iteration}: First message in the history must be from the user, instead found: {:?}",
                msg
            );
        }
        if let Some(Some(msg)) = state.history.as_ref().map(|h| h.last()) {
            assert!(
                matches!(msg, ChatMessage::AssistantResponseMessage(_)),
                "{assertion_iteration}: Last message in the history must be from the assistant, instead found: {:?}",
                msg
            );
            // If the last message from the assistant contains tool uses, then the next user
            // message must contain tool results.
            match (state.user_input_message.user_input_message_context.as_ref(), msg) {
                (
                    Some(ctx),
                    ChatMessage::AssistantResponseMessage(AssistantResponseMessage {
                        tool_uses: Some(tool_uses),
                        ..
                    }),
                ) if !tool_uses.is_empty() => {
                    assert!(
                        ctx.tool_results.as_ref().is_some_and(|r| !r.is_empty()),
                        "The user input message must contain tool results when the last assistant message contains tool uses"
                    );
                },
                _ => {},
            }
        }

        if let Some(history) = state.history.as_ref() {
            for (i, msg) in history.iter().enumerate() {
                // User message checks.
                if let ChatMessage::UserInputMessage(user) = msg {
                    assert!(
                        user.user_input_message_context
                            .as_ref()
                            .is_none_or(|ctx| ctx.tools.is_none()),
                        "the tool specification should be empty for all user messages in the history"
                    );

                    // Check that messages with tool results are immediately preceded by an
                    // assistant message with tool uses.
                    if user
                        .user_input_message_context
                        .as_ref()
                        .is_some_and(|ctx| ctx.tool_results.as_ref().is_some_and(|r| !r.is_empty()))
                    {
                        match history.get(i.checked_sub(1).unwrap_or_else(|| {
                            panic!(
                                "{assertion_iteration}: first message in the history should not contain tool results"
                            )
                        })) {
                            Some(ChatMessage::AssistantResponseMessage(assistant)) => {
                                assert!(assistant.tool_uses.is_some());
                            },
                            _ => panic!(
                                "expected an assistant response message with tool uses at index: {}",
                                i - 1
                            ),
                        }
                    }
                }
            }
        }

        let actual_history_len = state.history.unwrap_or_default().len();
        assert!(
            actual_history_len <= MAX_CONVERSATION_STATE_HISTORY_LEN,
            "history should not extend past the max limit of {}, instead found length {}",
            MAX_CONVERSATION_STATE_HISTORY_LEN,
            actual_history_len
        );

        let ctx = state
            .user_input_message
            .user_input_message_context
            .as_ref()
            .expect("user input message context must exist");
        assert!(
            ctx.tools.is_some(),
            "Currently, the tool spec must be included in the next user message"
        );
    }