1// Package main provides a simple streaming agent example of using the fantasy AI SDK.
 2package main
 3
 4import (
 5	"context"
 6	"fmt"
 7	"os"
 8
 9	"charm.land/fantasy"
10	"charm.land/fantasy/providers/openai"
11)
12
13func main() {
14	// Check for API key
15	apiKey := os.Getenv("OPENAI_API_KEY")
16	if apiKey == "" {
17		fmt.Println("Please set OPENAI_API_KEY environment variable")
18		os.Exit(1)
19	}
20
21	// Create provider and model
22	provider := openai.New(
23		openai.WithAPIKey(apiKey),
24	)
25	model, err := provider.LanguageModel("gpt-4o-mini")
26	if err != nil {
27		fmt.Println(err)
28		os.Exit(1)
29	}
30
31	// Create echo tool using the new type-safe API
32	type EchoInput struct {
33		Message string `json:"message" description:"The message to echo back"`
34	}
35
36	echoTool := fantasy.NewAgentTool(
37		"echo",
38		"Echo back the provided message",
39		func(_ context.Context, input EchoInput, _ fantasy.ToolCall) (fantasy.ToolResponse, error) {
40			return fantasy.NewTextResponse("Echo: " + input.Message), nil
41		},
42	)
43
44	// Create streaming agent
45	agent := fantasy.NewAgent(
46		model,
47		fantasy.WithSystemPrompt("You are a helpful assistant."),
48		fantasy.WithTools(echoTool),
49	)
50
51	ctx := context.Background()
52
53	fmt.Println("Simple Streaming Agent Example")
54	fmt.Println("==============================")
55	fmt.Println()
56
57	// Basic streaming with key callbacks
58	streamCall := fantasy.AgentStreamCall{
59		Prompt: "Please echo back 'Hello, streaming world!'",
60
61		// Show real-time text as it streams
62		OnTextDelta: func(_ string, text string) error {
63			fmt.Print(text)
64			return nil
65		},
66
67		// Show when tools are called
68		OnToolCall: func(toolCall fantasy.ToolCallContent) error {
69			fmt.Printf("\n[Tool: %s called]\n", toolCall.ToolName)
70			return nil
71		},
72
73		// Show tool results
74		OnToolResult: func(_ fantasy.ToolResultContent) error {
75			fmt.Printf("[Tool result received]\n")
76			return nil
77		},
78
79		// Show when each step completes
80		OnStepFinish: func(step fantasy.StepResult) error {
81			fmt.Printf("\n[Step completed: %s]\n", step.FinishReason)
82			return nil
83		},
84	}
85
86	fmt.Println("Assistant response:")
87	result, err := agent.Stream(ctx, streamCall)
88	if err != nil {
89		fmt.Printf("Error: %v\n", err)
90		os.Exit(1)
91	}
92
93	fmt.Printf("\n\nFinal result: %s\n", result.Response.Content.Text())
94	fmt.Printf("Steps: %d, Total tokens: %d\n", len(result.Steps), result.TotalUsage.TotalTokens)
95}