//! Pure Conversation entity — in-memory message history plus system prompt
//! and LLM generation parameters.
//!
//! # Architecture
//! This is a pure data structure with **no I/O logic**.  Load/save
//! responsibilities live in [`ConversationRepository`](super::repository::ConversationRepository).

#![allow(
    clippy::cast_possible_truncation,
    clippy::cast_sign_loss,
    clippy::cast_precision_loss,
    clippy::cast_possible_wrap
)]

use serde::{Deserialize, Serialize};

pub use zesdex_entities::seaorm::common::message::{ChatMessage, Role};

/// A single conversation's message history and generation settings.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Conversation {
    pub messages: Vec<ChatMessage>,
    pub system_prompt: String,
    pub session_id: String,
    pub model: String,
    pub max_tokens: Option<u32>,
    pub temperature: Option<f32>,
}

impl Conversation {
    /// Create an empty conversation with the given system prompt and
    /// session id, using default model / token / temperature settings.
    pub fn new(system_prompt: String, session_id: String) -> Self {
        Self {
            messages: Vec::new(),
            system_prompt,
            session_id,
            model: "anthropic/claude-opus-4-8".to_string(),
            max_tokens: None,
            temperature: None,
        }
    }

    /// Append a message to the conversation history.
    pub fn push(&mut self, msg: ChatMessage) {
        self.messages.push(msg);
    }

    /// Replace the system prompt and strip any prior `System`-role messages
    /// from history.
    pub fn rebuild_system(&mut self, new_prompt: String) {
        self.system_prompt = new_prompt;
        self.messages.retain(|m| !matches!(m.role, Role::System));
    }

    /// Build the message list to send to the LLM API, with the system
    /// prompt prepended as the first message.
    pub fn to_api_messages(&self) -> Vec<ChatMessage> {
        let mut msgs = Vec::with_capacity(self.messages.len() + 1);
        msgs.push(ChatMessage::system(&self.system_prompt));
        msgs.extend(self.messages.iter().cloned());
        msgs
    }

    /// Number of messages in the conversation history (excluding the
    /// synthesized system message).
    pub fn len(&self) -> usize {
        self.messages.len()
    }

    /// Returns `true` if the conversation has no messages.
    pub fn is_empty(&self) -> bool {
        self.messages.is_empty()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn chat_message_is_the_canonical_entities_type() {
        let canonical = zesdex_entities::seaorm::common::message::ChatMessage::user("hi");
        let via_cms: ChatMessage = canonical;
        assert_eq!(via_cms.content.as_deref(), Some("hi"));
    }
}