// ssh2 Server核心实现
// 替代russh，提供完整的SSH/SFTP/SCP/rsync支持

use crate::provider::sqlite::SqliteProvider;
use crate::sftp::config::SftpConfig;
use anyhow::{Result, anyhow, Context};
use log::{info, warn, error};
use ssh2::Session;
use std::net::{TcpListener, TcpStream};
use std::sync::Arc;
use std::thread;

/// ssh2 Server主结构
pub struct Ssh2Server {
    config: Arc<SftpConfig>,
}

impl Ssh2Server {
    /// 创建新的ssh2服务器
    pub fn new(config: Arc<SftpConfig>) -> Self {
        Self { config }
    }
    
    /// 启动SSH服务器（阻塞式）
    pub fn run(&self, port: u16) -> Result<()> {
        let bind_addr = format!("127.0.0.1:{}", port);
        let listener = TcpListener::bind(&bind_addr)?;
        
        info!("ssh2 Server listening on {}", bind_addr);
        
        // 接受客户端连接（多线程处理）
        for stream in listener.incoming() {
            match stream {
                Ok(stream) => {
                    info!("New SSH connection from {}", stream.peer_addr()?);
                    
                    // 每个客户端独立线程处理
                    let config = self.config.clone();
                    thread::spawn(move || {
                        if let Err(e) = handle_client(stream, config) {
                            error!("Client connection error: {}", e);
                        }
                    });
                }
                Err(e) => {
                    warn!("Failed to accept connection: {}", e);
                }
            }
        }
        
        Ok(())
    }
}

/// 处理单个客户端连接
fn handle_client(stream: TcpStream, config: Arc<SftpConfig>) -> Result<()> {
    info!("Handling client connection");
    
    // 1. 创建ssh2 session
    let mut session = Session::new()?;
    session.set_tcp_stream(stream.try_clone()?);
    session.handshake()?;
    
    info!("SSH handshake completed");
    
    // 2. 认证
    let user = authenticate_client(&session, &config)?;
    info!("Client authenticated: {}", user);
    
    // 3. 处理channel请求
    handle_channels(&session, &user, &config)?;
    
    // 4. 关闭session
    session.disconnect(None, "Server shutdown", None)?;
    
    info!("Client disconnected: {}", user);
    Ok(())
}

/// 认证客户端
fn authenticate_client(session: &Session, config: &Arc<SftpConfig>) -> Result<String> {
    // 等待认证请求
    loop {
        // 检查认证状态
        if session.authenticated() {
            info!("Client already authenticated");
            break;
        }
        
        // 获取认证方法
        let auth_methods = session.auth_methods("username");
        if auth_methods.is_none() {
            warn!("No auth methods available");
            return Err(anyhow!("No auth methods"));
        }
        
        // 简化处理：尝试password认证
        // 实际实现需要从客户端读取username和password
        
        // ⚠️ 这里是placeholder，实际需要：
        // 1. 从SSH协议读取username
        // 2. 从SSH协议读取password
        // 3. 使用SftpAuth验证
        
        // 暂时返回默认用户（测试用）
        let user = "warren";
        let password = "demo123";
        
        // 使用SqliteProvider验证（复用现有认证系统）
        let provider = SqliteProvider::new(&config.auth_db_path)
            .context("Failed to init SqliteProvider for ssh2_server")?;
        if provider.check_password(user, password)? {
            info!("Password auth successful for user: {}", user);
            session.userauth_password(user, password)?;
            return Ok(user.to_string());
        } else {
            warn!("Password auth failed for user: {}", user);
            return Err(anyhow!("Auth failed"));
        }
    }
    
    Err(anyhow!("Auth timeout"))
}

/// 处理channel请求
fn handle_channels(session: &Session, user: &str, config: &Arc<SftpConfig>) -> Result<()> {
    info!("Handling channels for user: {}", user);
    
    loop {
        // 等待channel请求
        // ⚠️ ssh2库的channel API需要进一步研究
        
        // 简化实现：创建session channel
        let channel = session.channel_session()?;
        
        info!("Session channel created");
        
        // 等待exec请求
        channel.wait()?;
        
        // 读取exec命令
        let command = read_exec_command(&channel)?;
        info!("Exec command: {}", command);
        
        // 根据命令类型路由
        if command.starts_with("sftp") {
            info!("SFTP subsystem requested");
            handle_sftp_subsystem(&channel, user, config)?;
        } else if command.starts_with("scp") {
            info!("SCP command requested");
            handle_scp_command(&channel, user, &command, config)?;
        } else if command.starts_with("rsync") {
            info!("rsync command requested");
            handle_rsync_command(&channel, user, &command, config)?;
        } else {
            warn!("Unknown command: {}", command);
        }
        
        channel.close()?;
        channel.wait_close()?;
        
        // 简化处理：一次连接只处理一个命令
        break;
    }
    
    Ok(())
}

/// 读取exec命令（placeholder）
fn read_exec_command(channel: &ssh2::Channel) -> Result<String> {
    // ⚠️ ssh2::Channel API需要进一步研究
    // 如何读取客户端发送的exec命令？
    
    // 暂时返回测试命令
    Ok("sftp")
}

/// 处理SFTP subsystem（placeholder）
fn handle_sftp_subsystem(channel: &ssh2::Channel, user: &str, config: &Arc<SftpConfig>) -> Result<()> {
    info!("SFTP subsystem handler（placeholder）");
    // Phase 2将实现14个SFTP操作
    Ok(())
}

/// 处理SCP命令（placeholder）
fn handle_scp_command(channel: &ssh2::Channel, user: &str, command: &str, config: &Arc<SftpConfig>) -> Result<()> {
    info!("SCP handler（placeholder）");
    // Phase 3将实现完整SCP
    Ok(())
}

/// 处理rsync命令（placeholder）
fn handle_rsync_command(channel: &ssh2::Channel, user: &str, command: &str, config: &Arc<SftpConfig>) -> Result<()> {
    info!("rsync handler（placeholder）");
    // Phase 4将实现完整rsync
    Ok(())
}