Add anvilmcp: MCP server for 9p agent communication
- Implements MCP protocol server that translates to 9p operations - Three tools: read_inbox, send_message, list_sessions - Uses plan9port 9p client for filesystem operations - Debug logging to stderr, JSON-RPC on stdout - Enables MCP clients to interact with anvilsrv daemon
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Levi Neely
parent
4b87a7795f
commit
b0c069bfa4
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package main
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import (
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"bufio"
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"encoding/json"
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"fmt"
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"os"
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"os/exec"
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"strings"
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)
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type MCPRequest struct {
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JSONRPC string `json:"jsonrpc"`
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ID interface{} `json:"id"`
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Method string `json:"method"`
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Params json.RawMessage `json:"params,omitempty"`
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}
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type MCPResponse struct {
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JSONRPC string `json:"jsonrpc"`
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ID interface{} `json:"id"`
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Result interface{} `json:"result,omitempty"`
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Error *MCPError `json:"error,omitempty"`
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}
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type MCPError struct {
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Code int `json:"code"`
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Message string `json:"message"`
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}
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type Tool struct {
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Name string `json:"name"`
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Description string `json:"description"`
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InputSchema InputSchema `json:"inputSchema"`
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}
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type InputSchema struct {
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Type string `json:"type"`
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Properties map[string]Property `json:"properties"`
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Required []string `json:"required,omitempty"`
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}
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type Property struct {
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Type string `json:"type"`
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Description string `json:"description"`
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Items *Items `json:"items,omitempty"`
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Enum []string `json:"enum,omitempty"`
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}
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type Items struct {
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Type string `json:"type"`
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}
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func main() {
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fmt.Fprintln(os.Stderr, "[anvilmcp] Starting MCP server")
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scanner := bufio.NewScanner(os.Stdin)
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for scanner.Scan() {
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line := scanner.Bytes()
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fmt.Fprintf(os.Stderr, "[anvilmcp] Received: %s\n", string(line))
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var req MCPRequest
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if err := json.Unmarshal(line, &req); err != nil {
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fmt.Fprintf(os.Stderr, "[anvilmcp] Parse error: %v\n", err)
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sendError(nil, -32700, "Parse error")
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continue
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}
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fmt.Fprintf(os.Stderr, "[anvilmcp] Method: %s\n", req.Method)
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switch req.Method {
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case "initialize":
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sendResponse(req.ID, map[string]interface{}{
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"protocolVersion": "2024-11-05",
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"capabilities": map[string]interface{}{
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"tools": map[string]bool{},
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},
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"serverInfo": map[string]string{
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"name": "anvilmcp",
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"version": "0.1.0",
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},
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})
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case "tools/list":
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sendResponse(req.ID, map[string]interface{}{
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"tools": []Tool{
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{
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Name: "read_inbox",
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Description: "Read messages from agent's inbox",
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InputSchema: InputSchema{
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Type: "object",
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Properties: map[string]Property{
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"agent_id": {Type: "string", Description: "Agent session ID (or 'user')"},
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},
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Required: []string{"agent_id"},
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},
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},
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{
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Name: "send_message",
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Description: "Send message to another agent or user",
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InputSchema: InputSchema{
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Type: "object",
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Properties: map[string]Property{
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"from": {Type: "string", Description: "Sender agent ID (or 'user')"},
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"to": {Type: "string", Description: "Recipient agent ID (or 'user')"},
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"type": {Type: "string", Description: "Message type"},
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"subject": {Type: "string", Description: "Message subject"},
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"body": {Type: "string", Description: "Message body"},
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},
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Required: []string{"from", "to", "type", "subject", "body"},
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},
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},
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{
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Name: "list_sessions",
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Description: "List all active sessions",
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InputSchema: InputSchema{
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Type: "object",
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Properties: map[string]Property{},
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},
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},
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},
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})
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case "tools/call":
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handleToolCall(req)
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default:
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sendError(req.ID, -32601, "Method not found")
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}
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}
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}
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func handleToolCall(req MCPRequest) {
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var params struct {
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Name string `json:"name"`
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Arguments map[string]interface{} `json:"arguments"`
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}
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if err := json.Unmarshal(req.Params, ¶ms); err != nil {
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fmt.Fprintf(os.Stderr, "[anvilmcp] Invalid params: %v\n", err)
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sendError(req.ID, -32602, "Invalid params")
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return
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}
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fmt.Fprintf(os.Stderr, "[anvilmcp] Tool call: %s with args: %v\n", params.Name, params.Arguments)
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switch params.Name {
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case "read_inbox":
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agentID, _ := params.Arguments["agent_id"].(string)
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fmt.Fprintf(os.Stderr, "[anvilmcp] Reading inbox for: %s\n", agentID)
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result, err := readInbox(agentID)
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if err != nil {
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fmt.Fprintf(os.Stderr, "[anvilmcp] Error: %v\n", err)
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sendError(req.ID, -32000, err.Error())
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return
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}
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fmt.Fprintf(os.Stderr, "[anvilmcp] Success: %d bytes\n", len(result))
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sendResponse(req.ID, map[string]interface{}{
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"content": []map[string]string{
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{"type": "text", "text": result},
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},
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})
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case "send_message":
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from, _ := params.Arguments["from"].(string)
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to, _ := params.Arguments["to"].(string)
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msgType, _ := params.Arguments["type"].(string)
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subject, _ := params.Arguments["subject"].(string)
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body, _ := params.Arguments["body"].(string)
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fmt.Fprintf(os.Stderr, "[anvilmcp] Sending message: %s -> %s (type: %s)\n", from, to, msgType)
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err := sendMessage(from, to, msgType, subject, body)
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if err != nil {
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fmt.Fprintf(os.Stderr, "[anvilmcp] Error: %v\n", err)
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sendError(req.ID, -32000, err.Error())
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return
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}
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fmt.Fprintf(os.Stderr, "[anvilmcp] Message sent successfully\n")
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sendResponse(req.ID, map[string]interface{}{
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"content": []map[string]string{
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{"type": "text", "text": "Message sent"},
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},
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})
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case "list_sessions":
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fmt.Fprintf(os.Stderr, "[anvilmcp] Listing sessions\n")
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result, err := listSessions()
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if err != nil {
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fmt.Fprintf(os.Stderr, "[anvilmcp] Error: %v\n", err)
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sendError(req.ID, -32000, err.Error())
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return
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}
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fmt.Fprintf(os.Stderr, "[anvilmcp] Found sessions: %d bytes\n", len(result))
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sendResponse(req.ID, map[string]interface{}{
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"content": []map[string]string{
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{"type": "text", "text": result},
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},
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})
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default:
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sendError(req.ID, -32601, "Tool not found")
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}
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}
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func readInbox(agentID string) (string, error) {
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inboxPath := fmt.Sprintf("agent/%s/inbox", agentID)
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cmd := exec.Command("9p", "ls", inboxPath)
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output, err := cmd.Output()
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if err != nil {
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return "", fmt.Errorf("failed to list inbox: %v", err)
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}
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files := strings.Split(strings.TrimSpace(string(output)), "\n")
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if len(files) == 0 || files[0] == "" {
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return "No messages", nil
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}
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var messages []string
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for _, file := range files {
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if !strings.HasSuffix(file, ".json") {
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continue
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}
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msgPath := fmt.Sprintf("%s/%s", inboxPath, file)
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cmd := exec.Command("9p", "read", msgPath)
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data, err := cmd.Output()
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if err != nil {
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continue
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}
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messages = append(messages, string(data))
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}
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if len(messages) == 0 {
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return "No messages", nil
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}
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return strings.Join(messages, "\n---\n"), nil
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}
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func sendMessage(from, to, msgType, subject, body string) error {
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msg := map[string]string{
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"to": to,
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"type": msgType,
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"subject": subject,
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"body": body,
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}
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data, err := json.Marshal(msg)
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if err != nil {
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return err
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}
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mailPath := fmt.Sprintf("agent/%s/mail", from)
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cmd := exec.Command("9p", "write", mailPath)
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cmd.Stdin = strings.NewReader(string(data))
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return cmd.Run()
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}
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func listSessions() (string, error) {
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cmd := exec.Command("9p", "read", "agent/list")
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output, err := cmd.Output()
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if err != nil {
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return "", err
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}
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return string(output), nil
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}
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func sendResponse(id interface{}, result interface{}) {
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resp := MCPResponse{
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JSONRPC: "2.0",
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ID: id,
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Result: result,
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}
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data, _ := json.Marshal(resp)
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fmt.Println(string(data))
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}
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func sendError(id interface{}, code int, message string) {
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resp := MCPResponse{
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JSONRPC: "2.0",
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ID: id,
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Error: &MCPError{Code: code, Message: message},
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}
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data, _ := json.Marshal(resp)
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fmt.Println(string(data))
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}
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