1package tools
 2
 3import (
 4	"context"
 5	_ "embed"
 6	"fmt"
 7	"net/http"
 8	"os"
 9	"strings"
10	"time"
11
12	"charm.land/fantasy"
13)
14
15//go:embed web_fetch.md
16var webFetchToolDescription []byte
17
18// NewWebFetchTool creates a simple web fetch tool for sub-agents (no permissions needed).
19func NewWebFetchTool(workingDir string, client *http.Client) fantasy.AgentTool {
20	if client == nil {
21		client = &http.Client{
22			Timeout: 30 * time.Second,
23			Transport: &http.Transport{
24				MaxIdleConns:        100,
25				MaxIdleConnsPerHost: 10,
26				IdleConnTimeout:     90 * time.Second,
27			},
28		}
29	}
30
31	return fantasy.NewAgentTool(
32		WebFetchToolName,
33		string(webFetchToolDescription),
34		func(ctx context.Context, params WebFetchParams, call fantasy.ToolCall) (fantasy.ToolResponse, error) {
35			if params.URL == "" {
36				return fantasy.NewTextErrorResponse("url is required"), nil
37			}
38
39			content, err := FetchURLAndConvert(ctx, client, params.URL)
40			if err != nil {
41				return fantasy.NewTextErrorResponse(fmt.Sprintf("Failed to fetch URL: %s", err)), nil
42			}
43
44			hasLargeContent := len(content) > LargeContentThreshold
45			var result strings.Builder
46
47			if hasLargeContent {
48				tempFile, err := os.CreateTemp(workingDir, "page-*.md")
49				if err != nil {
50					return fantasy.NewTextErrorResponse(fmt.Sprintf("Failed to create temporary file: %s", err)), nil
51				}
52				tempFilePath := tempFile.Name()
53
54				if _, err := tempFile.WriteString(content); err != nil {
55					_ = tempFile.Close() // Best effort close
56					return fantasy.NewTextErrorResponse(fmt.Sprintf("Failed to write content to file: %s", err)), nil
57				}
58				if err := tempFile.Close(); err != nil {
59					return fantasy.NewTextErrorResponse(fmt.Sprintf("Failed to close temporary file: %s", err)), nil
60				}
61
62				result.WriteString(fmt.Sprintf("Fetched content from %s (large page)\n\n", params.URL))
63				result.WriteString(fmt.Sprintf("Content saved to: %s\n\n", tempFilePath))
64				result.WriteString("Use the view and grep tools to analyze this file.")
65			} else {
66				result.WriteString(fmt.Sprintf("Fetched content from %s:\n\n", params.URL))
67				result.WriteString(content)
68			}
69
70			return fantasy.NewTextResponse(result.String()), nil
71		})
72}