//! Session metadata: id, title, workspace roots, and message/token counts,
//! persisted as `session.json` per session directory.
//!
//! # Flow
//!
//! Created via [`Session::new`] → mutated in-memory → persisted via repository.
//!
//! # Components
//!
//! - `Session` struct — fields for all session metadata
//! - `new` — timestamped constructor
//! - `session_dir` / `conversation_path` — pure path computation
use chrono::Utc;
use serde::{Deserialize, Serialize};
use std::path::{Path, PathBuf};

/// Metadata for one conversation session (distinct from the message
/// history itself, which lives in `Conversation`/the msglog).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Session {
    /// Unique session identifier (validated against path traversal in `load`).
    pub id: String,
    /// Epoch-millis timestamp of creation (`Utc::now().timestamp_millis()`).
    pub created_at: i64,
    /// Epoch-millis timestamp of last update.
    pub updated_at: i64,
    /// Human-readable title for the conversation.
    pub title: String,
    /// Model identifier string, e.g. `"anthropic/claude-opus-4-8"`.
    pub model: String,
    /// Workspace root directories associated with this session.
    pub workspace_roots: Vec<PathBuf>,
    /// Running count of messages in the conversation.
    pub message_count: u32,
    /// Running count of tokens consumed.
    pub token_count: u32,
    /// Soft-delete flag — archived sessions are hidden from the default list.
    pub archived: bool,
    /// Optional AI-generated conversation summary (used for compact context).
    pub summary: Option<String>,
}

impl Session {
    /// Create a new session with the given id/title, defaulting the
    /// model, workspace root (current dir), and counters.
    pub fn new(id: String, title: String) -> Self {
        let now = Utc::now().timestamp_millis();
        Session {
            id,
            created_at: now,
            updated_at: now,
            title,
            model: "anthropic/claude-opus-4-8".to_string(),
            workspace_roots: vec![std::env::current_dir().unwrap_or_default()],
            message_count: 0,
            token_count: 0,
            archived: false,
            summary: None,
        }
    }

    /// Compute this session's directory under `<base_dir>/sessions/<id>`.
    pub fn session_dir(&self, base_dir: &Path) -> PathBuf {
        base_dir.join("sessions").join(&self.id)
    }

    /// Compute this session's `conversation.json` path.
    pub fn conversation_path(&self, base_dir: &Path) -> PathBuf {
        self.session_dir(base_dir).join("conversation.json")
    }
}