//! L1 元胞层: 元胞自动机路由（CAR - Cellular Automaton Routing）
//!
//! 元胞自动机路由特点:
//! - 每个元胞维护到目标文明的特征向量梯度
//! - 数据包在当前元胞选择梯度下降最快的邻居转发
//! - 无中央路由表，完全分布式

use crate::types::{CellId, CellState, CivilizationId, CivilizationVector};
use crate::error::{Nrpc4Error, Result};
use std::collections::HashMap;
use tracing::{debug, info, warn};

/// 元胞自动机路由器
pub struct CellularAutomatonRouter {
    /// 本地元胞状态
    cell_state: CellState,
    /// 路由表 (文明ID -> 最佳下一跳元胞ID)
    routing_table: HashMap<CivilizationId, CellId>,
}

impl CellularAutomatonRouter {
    /// 创建新的元胞路由器
    pub fn new(cell_id: CellId) -> Self {
        info!("Creating new CAR with cell_id: {:?}", cell_id);
        Self {
            cell_state: CellState::new(cell_id),
            routing_table: HashMap::new(),
        }
    }

    /// 更新邻居梯度
    pub fn update_neighbor_gradient(
        &mut self,
        civilization_id: CivilizationId,
        vector: CivilizationVector,
    ) {
        debug!(
            "Updating gradient for civilization: {} from cell: {:?}",
            civilization_id, self.cell_state.cell_id
        );
        self.cell_state.update_gradient(civilization_id, vector);
    }

    /// 计算到目标文明的梯度下降路径
    ///
    /// 算法:
    /// 1. 查询所有邻居的梯度信息
    /// 2. 选择梯度下降最快的邻居
    /// 3. 返回最佳下一跳
    pub fn compute_gradient_descent(&self, target_civilization: &CivilizationId) -> Result<CellId> {
        debug!("Computing gradient descent to civilization: {}", target_civilization);

        // 查找目标文明的梯度信息
        let gradients = &self.cell_state.neighbor_gradients;
        
        if let Some(_vector) = gradients.get(target_civilization) {
            // 简化实现: 返回第一个活跃连接
            // 实际实现应该计算梯度并选择最优路径
            if let Some(&next_hop) = self.cell_state.active_connections.first() {
                debug!("Found next hop: {:?}", next_hop);
                return Ok(next_hop);
            }
        }

        warn!("No route found to civilization: {}", target_civilization);
        Err(Nrpc4Error::CellRoutingError(format!(
            "No route to civilization: {}",
            target_civilization
        )))
    }

    /// 路由数据包
    pub fn route_packet(
        &mut self,
        target_civilization: &CivilizationId,
        payload: Vec<u8>,
    ) -> Result<(CellId, Vec<u8>)> {
        info!(
            "Routing packet to civilization: {} (payload size: {} bytes)",
            target_civilization,
            payload.len()
        );

        // 计算下一跳
        let next_hop = self.compute_gradient_descent(target_civilization)?;

        // 增加意识温度 (表示网络活跃度)
        self.cell_state.increase_consciousness(1);

        Ok((next_hop, payload))
    }

    /// 添加活跃连接
    pub fn add_connection(&mut self, peer_cell_id: CellId) {
        if !self.cell_state.active_connections.contains(&peer_cell_id) {
            info!("Adding connection to cell: {:?}", peer_cell_id);
            self.cell_state.active_connections.push(peer_cell_id);
        }
    }

    /// 移除连接
    pub fn remove_connection(&mut self, peer_cell_id: &CellId) {
        self.cell_state.active_connections.retain(|id| id != peer_cell_id);
        info!("Removed connection to cell: {:?}", peer_cell_id);
    }

    /// 获取当前意识温度
    pub fn get_consciousness_temp(&self) -> u64 {
        self.cell_state.consciousness_temp
    }

    /// 获取元胞ID
    pub fn get_cell_id(&self) -> CellId {
        self.cell_state.cell_id
    }
}

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

    #[test]
    fn test_car_creation() {
        let cell_id = [1u8; 32];
        let router = CellularAutomatonRouter::new(cell_id);
        assert_eq!(router.get_cell_id(), cell_id);
        assert_eq!(router.get_consciousness_temp(), 0);
    }

    #[test]
    fn test_add_connection() {
        let mut router = CellularAutomatonRouter::new([1u8; 32]);
        let peer_id = [2u8; 32];
        router.add_connection(peer_id);
        assert_eq!(router.cell_state.active_connections.len(), 1);
    }

    #[test]
    fn test_route_packet() {
        let mut router = CellularAutomatonRouter::new([1u8; 32]);
        let peer_id = [2u8; 32];
        router.add_connection(peer_id);

        let civ_id = "nac-mainnet-001".to_string();
        let vector = CivilizationVector::new(civ_id.clone(), [0u8; 32], [1u8; 32]);
        router.update_neighbor_gradient(civ_id.clone(), vector);

        let payload = vec![1, 2, 3, 4];
        let result = router.route_packet(&civ_id, payload.clone());
        assert!(result.is_ok());
        
        let (next_hop, returned_payload) = result.unwrap();
        assert_eq!(next_hop, peer_id);
        assert_eq!(returned_payload, payload);
        assert_eq!(router.get_consciousness_temp(), 1);
    }
}