// 文件: grpc/server.go
package grpc

import (
	"bufio"
	"io"
	"log"
	relaypb "memobus_relay_server/relay_server/proto"
	"memobus_relay_server/session"
	"net/http"
	"net/http/httptest"
	"strings"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

// InternalRelayServer 实现了用于代理请求的 gRPC 服务
type InternalRelayServer struct {
	relaypb.UnimplementedInternalRelayServer
}

// NewInternalRelayServer 创建一个新的 gRPC 服务实例
func NewInternalRelayServer() *InternalRelayServer {
	return &InternalRelayServer{}
}

// ProxyRequest 是核心的 gRPC 流处理器，实现了完整的请求代理和流式响应
func (s *InternalRelayServer) ProxyRequest(stream relaypb.InternalRelay_ProxyRequestServer) error {
	// --- 1. 接收和解析请求头 ---
	headerMsg, err := stream.Recv()
	if err != nil {
		log.Printf("ERROR (gRPC): Failed to receive initial header: %v", err)
		return status.Errorf(codes.InvalidArgument, "failed to receive header: %v", err)
	}
	header := headerMsg.GetHeader()
	if header == nil {
		return status.Errorf(codes.InvalidArgument, "first message must be a header")
	}

	// [新增调试日志]
	if header.Headers["Upgrade"] == "websocket" {
		log.Printf("DEBUG (WebSocket): gRPC server received WebSocket upgrade request. Headers: Connection='%s', Upgrade='%s'", header.Headers["Connection"], header.Headers["Upgrade"])
	}

	// 检查是否是 WebSocket 握手请求
	isWebSocket := header.Headers["Upgrade"] == "websocket" && strings.Contains(strings.ToLower(header.Headers["Connection"]), "upgrade")

	pathParts := strings.SplitN(strings.TrimPrefix(header.Url, "/"), "/", 3)
	if len(pathParts) < 2 {
		return status.Errorf(codes.InvalidArgument, "invalid URL format in gRPC header")
	}
	deviceSN := pathParts[1]
	appUserID := header.GetAppUserId()

	if appUserID == "" {
		return status.Errorf(codes.InvalidArgument, "app_user_id is missing in gRPC header")
	}

	log.Printf("gRPC Proxy: Handling request for device '%s' from user '%s'", deviceSN, appUserID)

	// --- 2. 查找本地会话并进行授权检查 ---
	sessionInfo, ok := session.GlobalManager.GetLocalSession(deviceSN)
	if !ok {
		return status.Errorf(codes.NotFound, "device '%s' not connected to this instance", deviceSN)
	}

	if sessionInfo.UserID != appUserID {
		log.Printf("Forbidden (gRPC): User '%s' attempted to access device '%s' owned by '%s'", appUserID, deviceSN, sessionInfo.UserID)
		return sendForbiddenResponse(stream)
	}

	log.Printf("gRPC Proxy: Handling request for device '%s' from user '%s'", deviceSN, appUserID)

	// --- 3. [核心修改] 根据请求类型进行分流 ---
	if isWebSocket {
		log.Println("gRPC Proxy: Detected WebSocket request, diverting to transparent proxy handler.")
		return s.handleWebSocketProxy(stream, sessionInfo, deviceSN, header)
	} else {
		// 如果是普通 HTTP, 调用原来的 ReverseProxy 处理器
		log.Println("gRPC Proxy: Detected HTTP request, using ReverseProxy handler.")
		// 注意：我把原来的 ProxyRequest 逻辑提取到了一个新函数中，以保持整洁
		return s.handleHTTPProxy(stream, sessionInfo, deviceSN, header)
	}
}

func (s *InternalRelayServer) handleWebSocketProxy(stream relaypb.InternalRelay_ProxyRequestServer, sessionInfo *session.SessionInfo, deviceSN string, header *relaypb.ProxyRequestHeader) error {
	// 1. 打开到后端 (yamux) 的连接
	backendConn, err := sessionInfo.Session.Open()
	if err != nil {
		log.Printf("ERROR (WebSocket Proxy): Failed to dial backend: %v", err)
		return status.Errorf(codes.Internal, "failed to connect to backend service")
	}
	defer backendConn.Close()

	// 2. 重建原始的 HTTP 升级请求
	req := httptest.NewRequest(header.Method, "http://internal-proxy"+header.Url, nil)
	for k, v := range header.Headers {
		req.Header.Set(k, v)
	}
	req.Host = "immich-internal" // 模拟 ReverseProxy 的行为
	pathParts := strings.SplitN(strings.TrimPrefix(req.URL.Path, "/"), "/", 3)
	if len(pathParts) > 2 {
		req.URL.Path = "/" + pathParts[2]
	} else {
		req.URL.Path = "/"
	}

	// 3. 将升级请求写入后端连接，发起握手
	if err := req.Write(backendConn); err != nil {
		log.Printf("ERROR (WebSocket Proxy): Failed to write upgrade request to backend: %v", err)
		return status.Errorf(codes.Internal, "failed to send upgrade request to backend")
	}

	// 4. 读取后端的响应 (握手结果)
	backendReader := bufio.NewReader(backendConn)
	resp, err := http.ReadResponse(backendReader, req)
	if err != nil {
		log.Printf("ERROR (WebSocket Proxy): Failed to read handshake response from backend: %v", err)
		return status.Errorf(codes.Internal, "failed to read handshake response from backend")
	}

	// 5. 将后端的握手响应通过 gRPC 发回给代理节点
	respHeaderMsg := &relaypb.ProxyResponseMessage{
		Payload: &relaypb.ProxyResponseMessage_Header{
			Header: &relaypb.ProxyResponseHeader{
				StatusCode: int32(resp.StatusCode),
				Headers:    make(map[string]string),
			},
		},
	}
	for k, v := range resp.Header {
		respHeaderMsg.GetHeader().Headers[k] = strings.Join(v, ",")
	}
	if err := stream.Send(respHeaderMsg); err != nil {
		log.Printf("ERROR (WebSocket Proxy): Failed to send handshake response via gRPC: %v", err)
		return err
	}

	// 6. 如果握手失败 (不是 101)，则流程结束
	if resp.StatusCode != http.StatusSwitchingProtocols {
		log.Printf("WARN (WebSocket Proxy): Backend returned non-101 status for upgrade: %d", resp.StatusCode)
		return nil
	}

	log.Printf("WebSocket handshake for device %s successful. Starting bi-directional stream copy.", deviceSN)

	// 7. 握手成功！现在在 gRPC 流和 yamux 流之间建立双向数据拷贝
	errChan := make(chan error, 2)

	// Goroutine 1: gRPC 请求流 (来自 App) -> yamux 流 (下行数据)
	go func() {
		// 这个方向的逻辑没有问题
		for {
			msg, err := stream.Recv()
			if err == io.EOF {
				backendConn.Close()
				errChan <- nil
				return
			}
			if err != nil {
				errChan <- err
				return
			}
			if chunk := msg.GetBodyChunk(); chunk != nil {
				if _, err := backendConn.Write(chunk.Data); err != nil {
					errChan <- err
					return
				}
			}
		}
	}()

	// Goroutine 2: yamux 流 (来自设备) -> gRPC 响应流 (上行数据)
	go func() {
		// [核心修正]
		// 我们必须从 backendReader (而不是原始的 backendConn) 开始读取，
		// 以确保 http.ReadResponse 预读到缓冲区的数据不会丢失。
		// io.Copy 会首先清空 backendReader 的内部缓冲区，然后再继续从底层的 backendConn 读取。
		if _, err := io.Copy(&grpcResponseWriter{stream: stream}, backendReader); err != nil {
			// 过滤掉正常的连接关闭错误
			if err != io.EOF && err != io.ErrClosedPipe && !strings.Contains(err.Error(), "use of closed") {
				errChan <- err
			} else {
				errChan <- nil
			}
		} else {
			errChan <- nil
		}
	}()

	// 等待两个 goroutine 都结束
	err1 := <-errChan
	err2 := <-errChan

	if err1 != nil && err1 != io.EOF {
		log.Printf("WebSocket stream finished with error: %v", err1)
		return err1
	}
	if err2 != nil && err2 != io.EOF {
		log.Printf("WebSocket stream finished with error: %v", err2)
		return err2
	}

	log.Printf("WebSocket stream for device %s finished gracefully.", deviceSN)
	return nil
}

// [新增] handleHTTPProxy 包含了原来 ProxyRequest 的所有逻辑
func (s *InternalRelayServer) handleHTTPProxy(stream relaypb.InternalRelay_ProxyRequestServer, sessionInfo *session.SessionInfo, deviceSN string, header *relaypb.ProxyRequestHeader) error {
	// 这部分代码就是你之前工作正常的、使用 io.Pipe 和 ReverseProxy 的完整流式版本
	// 我直接粘贴过来

	// --- 3. 创建请求和响应的管道 ---
	reqPr, reqPw := io.Pipe()
	req := httptest.NewRequest(header.Method, "http://internal-proxy"+header.Url, reqPr)
	for k, v := range header.Headers {
		req.Header.Set(k, v)
	}
	req.Header.Set("X-Forwarded-For", header.RemoteAddr)

	respPr, respPw := io.Pipe()
	customResponseWriter := &streamResponseWriter{
		header:        make(http.Header),
		pipeWriter:    respPw,
		headerWritten: make(chan struct{}),
	}

	// --- 4. 启动 Goroutines ---
	go func() {
		defer reqPw.Close()
		for {
			bodyMsg, err := stream.Recv()
			if err == io.EOF {
				return
			}
			if err != nil {
				reqPw.CloseWithError(err)
				return
			}
			if bodyChunk := bodyMsg.GetBodyChunk(); bodyChunk != nil {
				if _, err := reqPw.Write(bodyChunk.Data); err != nil {
					return
				}
			}
		}
	}()

	errChan := make(chan error, 1)
	go func() {
		defer close(errChan)
		<-customResponseWriter.headerWritten
		// b. [修正] 完整地构造 gRPC 响应头
		respHeaderMsg := &relaypb.ProxyResponseMessage{
			Payload: &relaypb.ProxyResponseMessage_Header{
				Header: &relaypb.ProxyResponseHeader{
					StatusCode: int32(customResponseWriter.statusCode),
					Headers:    make(map[string]string),
				},
			},
		}
		for k, v := range customResponseWriter.header {
			respHeaderMsg.GetHeader().Headers[k] = strings.Join(v, ",")
		}
		if err := stream.Send(respHeaderMsg); err != nil {
			errChan <- err
			return
		}

		buf := make([]byte, 1024*32)
		if _, err := io.CopyBuffer(&grpcResponseWriter{stream: stream}, respPr, buf); err != nil {
			if err != io.ErrClosedPipe {
				errChan <- err
			}
		}
	}()

	// --- 5. 执行代理 ---
	proxy := session.CreateReverseProxy(sessionInfo, deviceSN, req.URL.Path, req.URL.RawQuery)
	proxy.ServeHTTP(customResponseWriter, req)

	// --- 6. 清理 ---
	respPw.Close()
	return <-errChan
}

// sendForbiddenResponse 是一个辅助函数，用于发送模拟的 403 响应
func sendForbiddenResponse(stream relaypb.InternalRelay_ProxyRequestServer) error {
	respHeader := &relaypb.ProxyResponseMessage{
		Payload: &relaypb.ProxyResponseMessage_Header{
			Header: &relaypb.ProxyResponseHeader{
				StatusCode: http.StatusForbidden,
				Headers:    map[string]string{"Content-Type": "text/plain; charset=utf-8"},
			},
		},
	}
	if err := stream.Send(respHeader); err != nil {
		return err
	}
	respBody := &relaypb.ProxyResponseMessage{
		Payload: &relaypb.ProxyResponseMessage_BodyChunk{
			BodyChunk: &relaypb.ProxyResponseBodyChunk{Data: []byte("Forbidden")},
		},
	}
	stream.Send(respBody)
	return nil // 正常关闭流
}

// streamResponseWriter 是一个自定义的 http.ResponseWriter
type streamResponseWriter struct {
	header        http.Header
	pipeWriter    *io.PipeWriter
	statusCode    int
	headerWritten chan struct{}
}

func (w *streamResponseWriter) Header() http.Header {
	return w.header
}

func (w *streamResponseWriter) Write(b []byte) (int, error) {
	w.WriteHeader(http.StatusOK)
	return w.pipeWriter.Write(b)
}

func (w *streamResponseWriter) WriteHeader(statusCode int) {
	select {
	case <-w.headerWritten:
		return
	default:
		w.statusCode = statusCode
		close(w.headerWritten)
	}
}

// grpcResponseWriter 是一个适配器，实现了 io.Writer 接口
type grpcResponseWriter struct {
	stream relaypb.InternalRelay_ProxyRequestServer
}

func (w *grpcResponseWriter) Write(p []byte) (n int, err error) {
	err = w.stream.Send(&relaypb.ProxyResponseMessage{
		Payload: &relaypb.ProxyResponseMessage_BodyChunk{
			BodyChunk: &relaypb.ProxyResponseBodyChunk{Data: p},
		},
	})
	if err != nil {
		return 0, err
	}
	return len(p), nil
}

// writeChunk 辅助函数 - 确保这个函数也存在于你的 grpc/server.go 文件中
func writeChunk(stream relaypb.InternalRelay_ProxyRequestServer, data []byte) error {
	return stream.Send(&relaypb.ProxyResponseMessage{
		Payload: &relaypb.ProxyResponseMessage_BodyChunk{
			BodyChunk: &relaypb.ProxyResponseBodyChunk{Data: data},
		},
	})
}