add mcp-client for testing purpose

Author: yinebebt

client.go

@@ -0,0 +1,219 @@
+//go:build client
+
+// A simple mcp-client that can be used to test the mcp server.
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+type MCPMessage struct {
+	JSONRPC string      `json:"jsonrpc"`
+	ID      int         `json:"id"`
+	Method  string      `json:"method,omitempty"`
+	Params  interface{} `json:"params,omitempty"`
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("Usage: go run mcp-client.go <your-mcp-server-binary> [args...]")
+		fmt.Println("Example: go run mcp-client.go ./my-mcp-server")
+		fmt.Println("Example: go run mcp-client.go node my-server.js")
+		os.Exit(1)
+	}
+
+	// Start your MCP server
+	args := os.Args[2:] // Skip program name and server binary
+	cmd := exec.Command(os.Args[1], args...)
+
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		fmt.Printf("❌ Error creating stdin pipe: %v\n", err)
+		return
+	}
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		fmt.Printf("❌ Error creating stdout pipe: %v\n", err)
+		return
+	}
+
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		fmt.Printf("❌ Error creating stderr pipe: %v\n", err)
+		return
+	}
+
+	fmt.Printf("Starting MCP server: %s %s\n", os.Args[1], strings.Join(args, " "))
+	if err := cmd.Start(); err != nil {
+		fmt.Printf("❌ Error starting server: %v\n", err)
+		return
+	}
+
+	// Handle server logs (stderr)
+	go func() {
+		scanner := bufio.NewScanner(stderr)
+		for scanner.Scan() {
+			fmt.Printf("Server Stderr: %s\n", scanner.Text())
+		}
+	}()
+
+	// Handle server responses (stdout)
+	responseChan := make(chan string)
+	go func() {
+		scanner := bufio.NewScanner(stdout)
+		for scanner.Scan() {
+			line := scanner.Text()
+			if strings.TrimSpace(line) != "" {
+				responseChan <- line
+			}
+		}
+		close(responseChan)
+	}()
+
+	messageID := 1
+	reader := bufio.NewReader(os.Stdin)
+
+	for {
+		fmt.Println("\n" + strings.Repeat("=", 60))
+		fmt.Println(" MCP Client - Choose an action:")
+		fmt.Println("1. Initialize connection")
+		fmt.Println("2. List available tools")
+		fmt.Println("3. Calculate 3 + 3")
+		fmt.Println("4. Calculate custom expression")
+		fmt.Println("5. Send custom JSON-RPC message")
+		fmt.Println("6. Exit")
+		fmt.Println(strings.Repeat("=", 60))
+
+		fmt.Print("Enter choice (1-6): ")
+		choice, _ := reader.ReadString('\n')
+		choice = strings.TrimSpace(choice)
+
+		var message MCPMessage
+
+		switch choice {
+		case "1":
+			message = MCPMessage{
+				JSONRPC: "2.0",
+				ID:      messageID,
+				Method:  "initialize",
+				Params: map[string]interface{}{
+					"protocolVersion": "2024-11-05",
+					"capabilities":    map[string]interface{}{},
+					"clientInfo": map[string]string{
+						"name":    "test-client",
+						"version": "1.0.0",
+					},
+				},
+			}
+
+		case "2":
+			message = MCPMessage{
+				JSONRPC: "2.0",
+				ID:      messageID,
+				Method:  "tools/list",
+				Params:  map[string]interface{}{},
+			}
+
+		case "3":
+			message = MCPMessage{
+				JSONRPC: "2.0",
+				ID:      messageID,
+				Method:  "tools/call",
+				Params: map[string]interface{}{
+					"name": "local__calculator__calculate",
+					"arguments": map[string]string{
+						"expression": "3 + 3",
+					},
+				},
+			}
+
+		case "4":
+			fmt.Print("Enter mathematical expression: ")
+			expr, _ := reader.ReadString('\n')
+			expr = strings.TrimSpace(expr)
+
+			message = MCPMessage{
+				JSONRPC: "2.0",
+				ID:      messageID,
+				Method:  "tools/call",
+				Params: map[string]interface{}{
+					"name": "local__calculator__calculate",
+					"arguments": map[string]string{
+						"expression": expr,
+					},
+				},
+			}
+
+		case "5":
+			fmt.Print("Enter JSON-RPC message: ")
+			jsonMsg, _ := reader.ReadString('\n')
+			jsonMsg = strings.TrimSpace(jsonMsg)
+
+			// Send raw JSON
+			fmt.Println("\nSENDING RAW JSON:")
+			fmt.Println(jsonMsg)
+			stdin.Write([]byte(jsonMsg + "\n"))
+
+			// Wait for response
+			waitForResponse(responseChan)
+			continue
+
+		case "6":
+			fmt.Println("Shutting down...")
+			stdin.Close()
+			cmd.Process.Kill()
+			return
+
+		default:
+			fmt.Println("Invalid choice")
+			continue
+		}
+
+		// Send message to server
+		fmt.Println("\nSENDING TO SERVER:")
+		prettyJSON, _ := json.MarshalIndent(message, "", "  ")
+		fmt.Println(string(prettyJSON))
+
+		jsonData, _ := json.Marshal(message)
+		fmt.Printf("\nRAW JSON PAYLOAD:\n%s\n", string(jsonData))
+
+		stdin.Write(append(jsonData, '\n'))
+		messageID++
+
+		// Wait for response
+		waitForResponse(responseChan)
+	}
+}
+
+func waitForResponse(responseChan chan string) {
+	fmt.Println("\nWaiting for server response...")
+
+	select {
+	case response, ok := <-responseChan:
+		if !ok {
+			fmt.Println("Server closed connection")
+			return
+		}
+
+		fmt.Println("\nSERVER RESPONSE:")
+
+		// Try to pretty print JSON
+		var jsonData interface{}
+		if err := json.Unmarshal([]byte(response), &jsonData); err == nil {
+			prettyJSON, _ := json.MarshalIndent(jsonData, "", "  ")
+			fmt.Println(string(prettyJSON))
+		} else {
+			fmt.Printf("Raw response: %s\n", response)
+		}
+
+	case <-time.After(5 * time.Second):
+		fmt.Println("Timeout waiting for response")
+	}
+}