use std::sync::Arc;

use bson::Document;
use dashmap::DashMap;
use rustdb_index::IndexEngine;
use rustdb_storage::StorageAdapter;
use rustdb_txn::{SessionEngine, TransactionEngine};

/// Shared command execution context, passed to all handlers.
pub struct CommandContext {
    /// The storage backend.
    pub storage: Arc<dyn StorageAdapter>,
    /// Index engines per namespace: "db.collection" -> IndexEngine.
    pub indexes: Arc<DashMap<String, IndexEngine>>,
    /// Transaction engine for multi-document transactions.
    pub transactions: Arc<TransactionEngine>,
    /// Session engine for logical sessions.
    pub sessions: Arc<SessionEngine>,
    /// Active cursors for getMore / killCursors.
    pub cursors: Arc<DashMap<i64, CursorState>>,
    /// Server start time (for uptime reporting).
    pub start_time: std::time::Instant,
}

/// State of an open cursor from a find or aggregate command.
pub struct CursorState {
    /// Documents remaining to be returned.
    pub documents: Vec<Document>,
    /// Current read position within `documents`.
    pub position: usize,
    /// Database the cursor belongs to.
    pub database: String,
    /// Collection the cursor belongs to.
    pub collection: String,
}