feat: mcp server sdk (#4794)

Signed-off-by: kevin <wanjunfeng@gmail.com>

mcp/vars.go

@@ -0,0 +1,137 @@
+package mcp
+
+import (
+	"time"
+
+	"github.com/zeromicro/go-zero/core/syncx"
+)
+
+// Protocol constants
+const (
+	// JSON-RPC version as defined in the specification
+	jsonRpcVersion = "2.0"
+
+	// Session identifier key used in request URLs
+	sessionIdKey = "session_id"
+)
+
+// Server-Sent Events (SSE) event types
+const (
+	// Standard message event for JSON-RPC responses
+	eventMessage = "message"
+
+	// Endpoint event for sending endpoint URL to clients
+	eventEndpoint = "endpoint"
+)
+
+// Content type identifiers
+const (
+	// Text content type
+	contentTypeText = "text"
+
+	// Image content type
+	contentTypeImage = "image"
+)
+
+// Collection keys for broadcast events
+const (
+	// Key for prompts collection
+	keyPrompts = "prompts"
+
+	// Key for resources collection
+	keyResources = "resources"
+
+	// Key for tools collection
+	keyTools = "tools"
+)
+
+// JSON-RPC error codes
+// Standard error codes from JSON-RPC 2.0 spec
+const (
+	// Invalid JSON was received by the server
+	errCodeInvalidRequest = -32600
+
+	// The method does not exist / is not available
+	errCodeMethodNotFound = -32601
+
+	// Invalid method parameter(s)
+	errCodeInvalidParams = -32602
+
+	// Internal JSON-RPC error
+	errCodeInternalError = -32603
+
+	// Tool execution timed out
+	errCodeTimeout = -32001
+
+	// Resource not found error
+	errCodeResourceNotFound = -32002
+
+	// Client hasn't completed initialization
+	errCodeClientNotInitialized = -32800
+)
+
+// User and assistant role definitions
+const (
+	// The "user" role - the entity asking questions
+	roleUser roleType = "user"
+
+	// The "assistant" role - the entity providing responses
+	roleAssistant roleType = "assistant"
+)
+
+// Method names as defined in the MCP specification
+const (
+	// Initialize the connection between client and server
+	methodInitialize = "initialize"
+
+	// List available tools
+	methodToolsList = "tools/list"
+
+	// Call a specific tool
+	methodToolsCall = "tools/call"
+
+	// List available prompts
+	methodPromptsList = "prompts/list"
+
+	// Get a specific prompt
+	methodPromptsGet = "prompts/get"
+
+	// List available resources
+	methodResourcesList = "resources/list"
+
+	// Read a specific resource
+	methodResourcesRead = "resources/read"
+
+	// Subscribe to resource updates
+	methodResourcesSubscribe = "resources/subscribe"
+
+	// Simple ping to check server availability
+	methodPing = "ping"
+
+	// Notification that client is fully initialized
+	methodNotificationsInitialized = "notifications/initialized"
+
+	// Notification that a request was canceled
+	methodNotificationsCancelled = "notifications/cancelled"
+)
+
+// Event names for Server-Sent Events (SSE)
+const (
+	// Notification of tool list changes
+	eventToolsListChanged = "tools/list_changed"
+
+	// Notification of prompt list changes
+	eventPromptsListChanged = "prompts/list_changed"
+
+	// Notification of resource list changes
+	eventResourcesListChanged = "resources/list_changed"
+)
+
+var (
+	// Default channel size for events
+	eventChanSize = 10
+
+	// Default ping interval for checking connection availability
+	// use syncx.ForAtomicDuration to ensure atomicity in test race
+	pingInterval = syncx.ForAtomicDuration(30 * time.Second)
+)