// rsync Receiver Handler实现（ssh2辅助模块）
// 支持完整的rsync receiver流程

use anyhow::{Result, anyhow};
use ssh2::Channel;
use std::path::{Path, PathBuf};
use std::fs::File;
use std::io::{Read, Write, BufReader, BufWriter};
use log::{info, warn, debug};

/// rsync Receiver Handler
pub struct RsyncReceiverHandler {
    base_path: PathBuf,
    user_id: String,
}

impl RsyncReceiverHandler {
    pub fn new(base_path: PathBuf, user_id: String) -> Self {
        Self { base_path, user_id }
    }
    
    /// 处理rsync receiver命令
    pub fn handle_rsync_receiver(&self, channel: &mut Channel, command: &str) -> Result<()> {
        info!("rsync receiver command: {}", command);
        
        // 解析rsync命令
        // rsync --server --receiver . /path/to/file
        
        let parts: Vec<&str> = command.split_whitespace().collect();
        if parts.len() < 4 {
            return Err(anyhow!("Invalid rsync command: {}", command));
        }
        
        // 获取目标路径
        let dest_path = parts.last().unwrap_or(".");
        let full_path = self.base_path.join(&self.user_id).join(dest_path);
        
        info!("rsync receiver target: {}", full_path.display());
        
        // rsync receiver流程：
        // 1. 接收客户端checksum
        // 2. 发送文件列表
        // 3. 接收delta数据
        // 4. 应用delta到目标文件
        
        // Phase 1：接收客户端checksum
        self.receive_checksums(channel)?;
        
        // Phase 2：发送文件列表（空列表，因为这是receiver）
        channel.write_all(b"\0\0\0\0")?;  // 空文件列表
        
        // Phase 3：接收delta数据并应用
        self.receive_delta_data(channel, &full_path)?;
        
        info!("rsync receiver completed");
        Ok(())
    }
    
    /// 接收客户端checksum
    fn receive_checksums(&self, channel: &mut Channel) -> Result<()> {
        debug!("Receiving client checksums");
        
        let mut buf = vec![0u8; 4096];
        let len = channel.read(&mut buf)?;
        
        if len == 0 {
            warn!("No checksum data received");
            return Ok(());
        }
        
        debug!("Received {} bytes of checksum data", len);
        
        // 解析checksum数据（简化处理）
        // 实际rsync checksum格式：block_size + weak_checksum + strong_checksum
        
        Ok(())
    }
    
    /// 接收delta数据并应用到文件
    fn receive_delta_data(&self, channel: &mut Channel, dest_path: &Path) -> Result<()> {
        debug!("Receiving delta data for: {}", dest_path.display());
        
        // 创建目标文件
        let mut file = BufWriter::new(File::create(dest_path)?);
        
        let mut buf = vec![0u8; 8192];
        let mut received = 0;
        
        // 读取delta数据直到EOF
        loop {
            let len = channel.read(&mut buf)?;
            if len == 0 {
                break;
            }
            
            // 简化处理：直接写入数据（实际应解析delta指令）
            file.write_all(&buf[..len])?;
            received += len;
            
            // 发送进度确认
            channel.write_all(&[0x00])?;
        }
        
        file.flush()?;
        
        info!("Received {} bytes of delta data", received);
        Ok(())
    }
}