arp/mcp/protocol.go

package mcp

import "encoding/json"

// MCP Protocol constants
const (
	ProtocolVersion = "2024-11-05"
	ContentType     = "application/json"
)

// JSON-RPC 2.0 types
type JSONRPCRequest struct {
	JSONRPC string          `json:"jsonrpc"`
	ID      interface{}     `json:"id,omitempty"`
	Method  string          `json:"method"`
	Params  json.RawMessage `json:"params,omitempty"`
}

type JSONRPCResponse struct {
	JSONRPC string      `json:"jsonrpc"`
	ID      interface{} `json:"id,omitempty"`
	Result  interface{} `json:"result,omitempty"`
	Error   *RPCError   `json:"error,omitempty"`
}

type RPCError struct {
	Code    int         `json:"code"`
	Message string      `json:"message"`
	Data    interface{} `json:"data,omitempty"`
}

// Standard JSON-RPC error codes
var (
	ErrParseError     = &RPCError{Code: -32700, Message: "Parse error"}
	ErrInvalidRequest = &RPCError{Code: -32600, Message: "Invalid request"}
	ErrMethodNotFound = &RPCError{Code: -32601, Message: "Method not found"}
	ErrInvalidParams  = &RPCError{Code: -32602, Message: "Invalid params"}
	ErrInternal       = &RPCError{Code: -32603, Message: "Internal error"}
)

// MCP specific types
type InitializeParams struct {
	ProtocolVersion string                 `json:"protocolVersion"`
	Capabilities    ClientCapabilities     `json:"capabilities"`
	ClientInfo      ImplementationInfo     `json:"clientInfo"`
	Meta            map[string]interface{} `json:"_meta,omitempty"`
}

type InitializeResult struct {
	ProtocolVersion string             `json:"protocolVersion"`
	Capabilities    ServerCapabilities `json:"capabilities"`
	ServerInfo      ImplementationInfo `json:"serverInfo"`
	Instructions    string             `json:"instructions,omitempty"`
}

type ClientCapabilities struct {
	Experimental map[string]interface{} `json:"experimental,omitempty"`
	Roots        *RootsCapability       `json:"roots,omitempty"`
	Sampling     *SamplingCapability    `json:"sampling,omitempty"`
}

type RootsCapability struct {
	ListChanged bool `json:"listChanged,omitempty"`
}

type SamplingCapability struct{}

type ServerCapabilities struct {
	Experimental map[string]interface{} `json:"experimental,omitempty"`
	Tools        *ToolsCapability       `json:"tools,omitempty"`
	Resources    *ResourcesCapability   `json:"resources,omitempty"`
}

type ToolsCapability struct {
	ListChanged bool `json:"listChanged,omitempty"`
}

type ResourcesCapability struct {
	Subscribe   bool `json:"subscribe,omitempty"`
	ListChanged bool `json:"listChanged,omitempty"`
}

type ImplementationInfo struct {
	Name    string `json:"name"`
	Version string `json:"version"`
}

// Tool types
type Tool struct {
	Name        string      `json:"name"`
	Description string      `json:"description"`
	InputSchema InputSchema `json:"inputSchema"`
}

type InputSchema struct {
	Type                 string              `json:"type"`
	Properties           map[string]Property `json:"properties,omitempty"`
	Required             []string            `json:"required,omitempty"`
	AdditionalProperties bool                `json:"additionalProperties"`
}

type Property struct {
	Type        string `json:"type"`
	Description string `json:"description,omitempty"`
}

type ListToolsResult struct {
	Tools []Tool `json:"tools"`
}

type CallToolParams struct {
	Name      string                 `json:"name"`
	Arguments map[string]interface{} `json:"arguments,omitempty"`
}

type CallToolResult struct {
	Content []ContentBlock `json:"content"`
	IsError bool           `json:"isError,omitempty"`
}

type ContentBlock struct {
	Type string `json:"type"`
	Text string `json:"text"`
}

// Ping
type PingResult struct{}

// Resource types for subscriptions
type Resource struct {
	URI         string `json:"uri"`
	Name        string `json:"name"`
	Description string `json:"description,omitempty"`
	MimeType    string `json:"mimeType,omitempty"`
}

type ListResourcesResult struct {
	Resources []Resource `json:"resources"`
}

type ReadResourceParams struct {
	URI string `json:"uri"`
}

type ReadResourceResult struct {
	Contents []ResourceContents `json:"contents"`
}

type ResourceContents struct {
	URI      string `json:"uri"`
	MimeType string `json:"mimeType,omitempty"`
	Text     string `json:"text,omitempty"`
	Blob     string `json:"blob,omitempty"` // base64 encoded
}

// Subscription types
type SubscribeParams struct {
	URI string `json:"uri"`
}

type UnsubscribeParams struct {
	URI string `json:"uri"`
}

// Resource update notification
type ResourceUpdatedNotification struct {
	URI      string           `json:"uri"`
	Contents ResourceContents `json:"contents"`
}

// JSON-RPC Notification
type JSONRPCNotification struct {
	JSONRPC string      `json:"jsonrpc"`
	Method  string      `json:"method"`
	Params  interface{} `json:"params,omitempty"`
}

// CreateResourceNotification creates a JSON-RPC notification for resource updates
func CreateResourceNotification(uri string, data interface{}) *JSONRPCNotification {
	// Marshal the data to JSON
	dataBytes, err := json.Marshal(data)
	if err != nil {
		dataBytes = []byte("{}")
	}

	return &JSONRPCNotification{
		JSONRPC: "2.0",
		Method:  "notifications/resources/updated",
		Params: ResourceUpdatedNotification{
			URI: uri,
			Contents: ResourceContents{
				URI:      uri,
				MimeType: "application/json",
				Text:     string(dataBytes),
			},
		},
	}
}