main.go

package main

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"os"
	"strings"

	"github.com/anthropics/anthropic-sdk-go"
	"github.com/anthropics/anthropic-sdk-go/option"
)

// Config holds the assistant's runtime configuration.
// Loaded from config.json if present, otherwise uses defaults.
type Config struct {
	SystemPrompt string `json:"system_prompt"`
	Model        string `json:"model"`
	MaxTokens    int64  `json:"max_tokens"`
}

func loadConfig() Config {
	cfg := Config{
		SystemPrompt: "You are a helpful assistant. Be concise and direct.",
		Model:        string(anthropic.ModelClaudeOpus4_7),
		MaxTokens:    1024,
	}

	data, err := os.ReadFile("config.json")
	if err == nil {
		json.Unmarshal(data, &cfg) // silently ignore parse errors, use defaults
	}
	return cfg
}

func main() {
	client := anthropic.NewClient(option.WithAPIKey(os.Getenv("ANTHROPIC_API_KEY")))
	ctx := context.Background()
	cfg := loadConfig()

	history := []anthropic.MessageParam{}
	scanner := bufio.NewScanner(os.Stdin)

	fmt.Println("Claude CLI Assistant — type 'exit' to quit, 'reset' to clear history")
	fmt.Printf("Model: %s | System: %q\n\n", cfg.Model, cfg.SystemPrompt)

	for {
		fmt.Print("You: ")
		if !scanner.Scan() {
			break
		}
		input := strings.TrimSpace(scanner.Text())
		if input == "" {
			continue
		}
		if input == "exit" {
			fmt.Println("Goodbye!")
			break
		}
		if input == "reset" {
			history = nil
			fmt.Println("[History cleared]")
			continue
		}

		history = append(history, anthropic.NewUserMessage(anthropic.NewTextBlock(input)))

		stream := client.Messages.NewStreaming(ctx, anthropic.MessageNewParams{
			Model:     anthropic.Model(cfg.Model),
			MaxTokens: cfg.MaxTokens,
			System: []anthropic.TextBlockParam{
				anthropic.NewTextBlockParam(cfg.SystemPrompt),
			},
			Messages: history,
		})

		message := anthropic.Message{}
		fmt.Print("Claude: ")

		for stream.Next() {
			event := stream.Current()
			message.Accumulate(event)
			switch delta := event.Delta.(type) {
			case anthropic.ContentBlockDeltaEventDelta:
				if delta.Type == "text_delta" {
					fmt.Print(delta.Text)
				}
			}
		}

		if err := stream.Err(); err != nil {
			fmt.Fprintf(os.Stderr, "\nstream error: %v\n", err)
			continue
		}

		fmt.Println()
		history = append(history, message.ToParam())
	}
}