//! Conversation use-case implementation.
//!
//! `ConversationServiceImpl` implements [`ConversationService`] from the
//! domain layer. It is generic over `R: ConversationRepository`, delegating
//! all persistence to that adapter.
//!
//! # Flow
//!
//! Each method computes the session directory from the session ID, then
//! delegates the actual I/O to the injected `repo`. Error context is
//! added at this layer to identify which session caused the failure.

use std::path::PathBuf;
use tracing;

use zesdex_domain::cms::{Conversation, ConversationRepository, ServiceError};
use zesdex_domain::core::ChatMessage;

/// Service implementation for conversation CRUD operations.
///
/// Generic over `R: ConversationRepository` so the persistence layer
/// can be swapped without changing business logic.
pub struct ConversationServiceImpl<R> {
    pub repo: R,
    /// Base directory containing session subdirectories.
    pub sessions_dir: PathBuf,
}

impl<R: ConversationRepository> ConversationServiceImpl<R> {
    /// Create a new service with the given repository and sessions directory.
    pub fn new(repo: R, sessions_dir: impl Into<PathBuf>) -> Self {
        tracing::debug!("creating ConversationServiceImpl");
        Self {
            repo,
            sessions_dir: sessions_dir.into(),
        }
    }

    /// Compute the session directory for a given session id.
    fn session_dir(&self, session_id: &str) -> PathBuf {
        self.sessions_dir.join(session_id)
    }
}

impl<R: ConversationRepository> zesdex_domain::cms::ConversationService
    for ConversationServiceImpl<R>
{
    fn load_conversation(&self, session_id: &str) -> Result<Conversation, ServiceError> {
        tracing::debug!("loading conversation for session {session_id}");
        let dir = self.session_dir(session_id);
        self.repo.load(&dir).map_err(ServiceError::Repository)
    }

    fn save_conversation(&self, conv: &Conversation) -> Result<(), ServiceError> {
        tracing::debug!("saving conversation for session {}", conv.session_id);
        let dir = self.session_dir(&conv.session_id);
        self.repo.save(&dir, conv)?;
        Ok(())
    }

    fn add_message(
        &self,
        conv: &mut Conversation,
        msg: ChatMessage,
    ) -> Result<(), ServiceError> {
        tracing::debug!("adding message to session {}", conv.session_id);
        conv.push(msg);
        let dir = self.session_dir(&conv.session_id);
        self.repo.save(&dir, conv)?;
        Ok(())
    }
}