package handler

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"yunion.io/x/log"
	"yunion.io/x/pkg/errors"
	"yunion.io/x/pkg/util/httputils"

	"yunion.io/x/onecloud/pkg/apigateway/options"
	"yunion.io/x/onecloud/pkg/appsrv"
	"yunion.io/x/onecloud/pkg/httperrors"
	"yunion.io/x/onecloud/pkg/mcclient/auth"
	modules "yunion.io/x/onecloud/pkg/mcclient/modules/llm"
	mcpServerOption "yunion.io/x/onecloud/pkg/mcp-server/options"
)

func mcpServersConfigHandler(ctx context.Context, w http.ResponseWriter, r *http.Request) {
	serviceName := "mcp-server"
	url, err := auth.GetPublicServiceURL(serviceName, options.Options.Region, "", httputils.GET)
	if err != nil {
		log.Warningf("GetPublicServiceURL for %s failed: %v", serviceName, err)
	}
	sseURL := fmt.Sprintf("%s/sse", url)

	responseType := r.URL.Query().Get("type")
	switch responseType {
	case "claude":
		// Claude 仅支持单个自定义 header，使用 X-API-Key。填写方式：
		// base64(ak:sk)：`echo -n "你的AK:你的SK" | base64`，将输出填入
		cmd := fmt.Sprintf("claude mcp add --transport sse %s --header \"X-API-Key: <填写 token 或 base64(AK:SK)>\"", sseURL)
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		w.Write([]byte(cmd))
		return
	case "cursor":
		// fall through to JSON
	default:
		// default: return JSON (cursor format)
	}

	// Cursor：在 headers 中填写控制台/CLI 获取的 Access Key 与 Secret Key
	config := map[string]interface{}{
		"mcpServers": map[string]interface{}{
			mcpServerOption.Options.MCPServerName: map[string]interface{}{
				"url": sseURL,
				"headers": map[string]string{
					"AK": "<填写 Access Key>",
					"SK": "<填写 Secret Key>",
				},
			},
		},
	}
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(config)
}

func chatHandlerInfo(method, prefix string, handler func(context.Context, http.ResponseWriter, *http.Request)) *appsrv.SHandlerInfo {
	log.Debugf("%s - %s", method, prefix)
	hi := appsrv.SHandlerInfo{}
	hi.SetMethod(method)
	hi.SetPath(prefix)
	hi.SetHandler(handler)
	hi.SetProcessTimeout(6 * time.Hour)
	// Use default worker manager with default pool size (usually 32)
	// instead of uploader worker which has limited pool size (4)
	return &hi
}

func mcpAgentChatStreamHandler(ctx context.Context, w http.ResponseWriter, r *http.Request) {
	params, _, body := appsrv.FetchEnv(ctx, w, r)
	id := params["<id>"]
	if len(id) == 0 {
		httperrors.MissingParameterError(ctx, w, "id")
		return
	}

	token := AppContextToken(ctx)
	s := auth.GetSession(ctx, token, FetchRegion(r))

	// Prepare request to backend
	headers := http.Header{}
	headers.Set("Content-Type", "application/json")

	// Forward the request body to the backend
	var bodyReader io.Reader
	if body != nil {
		bodyStr := body.String()
		bodyReader = strings.NewReader(bodyStr)
	}

	path := fmt.Sprintf("/mcp_agents/%s/chat-stream", id)
	resp, err := s.RawVersionRequest(
		modules.MCPAgent.ServiceType(),
		modules.MCPAgent.EndpointType(),
		"POST",
		path,
		headers,
		bodyReader,
	)
	if err != nil {
		httperrors.GeneralServerError(ctx, w, errors.Wrap(err, "request backend"))
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		// Read error body
		respBody, _ := io.ReadAll(resp.Body)
		// Try to parse as JSON error if possible, or just return as is
		if resp.StatusCode >= 400 && resp.StatusCode < 500 {
			httperrors.InputParameterError(ctx, w, "backend error: %s", string(respBody))
		} else {
			httperrors.GeneralServerError(ctx, w, fmt.Errorf("backend error %d: %s", resp.StatusCode, string(respBody)))
		}
		return
	}

	// Set SSE headers
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	// For now just standard SSE headers.

	if f, ok := w.(http.Flusher); ok {
		f.Flush()
	}

	// Stream the response from backend to client
	buf := make([]byte, 1024)
	for {
		n, err := resp.Body.Read(buf)
		if n > 0 {
			if _, wErr := w.Write(buf[:n]); wErr != nil {
				log.Errorf("write response error: %v", wErr)
				return
			}
			if f, ok := w.(http.Flusher); ok {
				f.Flush()
			}
		}
		if err != nil {
			if err != io.EOF {
				log.Errorf("read backend response error: %v", err)
			}
			break
		}
	}
}

// mcpAgentDefaultChatStreamHandler 将请求转发到 region 的 default-chat-stream（使用 default_agent=true 的条目）
func mcpAgentDefaultChatStreamHandler(ctx context.Context, w http.ResponseWriter, r *http.Request) {
	token := AppContextToken(ctx)
	s := auth.GetSession(ctx, token, FetchRegion(r))

	headers := http.Header{}
	headers.Set("Content-Type", "application/json")

	var bodyReader io.Reader
	if r.Body != nil {
		bodyReader = r.Body
	}

	path := "/mcp_agents/default-chat-stream"
	resp, err := s.RawVersionRequest(
		modules.MCPAgent.ServiceType(),
		modules.MCPAgent.EndpointType(),
		"POST",
		path,
		headers,
		bodyReader,
	)
	if err != nil {
		httperrors.GeneralServerError(ctx, w, errors.Wrap(err, "request backend"))
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		respBody, _ := io.ReadAll(resp.Body)
		if resp.StatusCode >= 400 && resp.StatusCode < 500 {
			httperrors.InputParameterError(ctx, w, "backend error: %s", string(respBody))
		} else {
			httperrors.GeneralServerError(ctx, w, fmt.Errorf("backend error %d: %s", resp.StatusCode, string(respBody)))
		}
		return
	}

	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	if f, ok := w.(http.Flusher); ok {
		f.Flush()
	}

	buf := make([]byte, 1024)
	for {
		n, err := resp.Body.Read(buf)
		if n > 0 {
			if _, wErr := w.Write(buf[:n]); wErr != nil {
				log.Errorf("write response error: %v", wErr)
				return
			}
			if f, ok := w.(http.Flusher); ok {
				f.Flush()
			}
		}
		if err != nil {
			if err != io.EOF {
				log.Errorf("read backend response error: %v", err)
			}
			break
		}
	}
}

// mcpAgentDefaultToolsHandler 将 GET 请求转发到 region 的 default-mcp-tools（仅使用 options.MCPServerURL，不通过 mcp_agent 条目）
func mcpAgentDefaultToolsHandler(ctx context.Context, w http.ResponseWriter, r *http.Request) {
	token := AppContextToken(ctx)
	s := auth.GetSession(ctx, token, FetchRegion(r))

	path := "/mcp_agents/default-mcp-tools"
	resp, err := s.RawVersionRequest(
		modules.MCPAgent.ServiceType(),
		modules.MCPAgent.EndpointType(),
		"GET",
		path,
		nil,
		nil,
	)
	if err != nil {
		httperrors.GeneralServerError(ctx, w, errors.Wrap(err, "request backend"))
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		respBody, _ := io.ReadAll(resp.Body)
		if resp.StatusCode >= 400 && resp.StatusCode < 500 {
			httperrors.InputParameterError(ctx, w, "backend error: %s", string(respBody))
		} else {
			httperrors.GeneralServerError(ctx, w, fmt.Errorf("backend error %d: %s", resp.StatusCode, string(respBody)))
		}
		return
	}

	w.Header().Set("Content-Type", "application/json")
	_, err = io.Copy(w, resp.Body)
	if err != nil {
		log.Errorf("write default mcp tools response error: %v", err)
	}
}