1package tools
2
3import (
4 "context"
5 "encoding/json"
6 "fmt"
7 "io"
8 "net/http"
9 "strings"
10 "time"
11
12 md "github.com/JohannesKaufmann/html-to-markdown"
13 "github.com/PuerkitoBio/goquery"
14 "github.com/opencode-ai/opencode/internal/config"
15 "github.com/opencode-ai/opencode/internal/permission"
16)
17
18type FetchParams struct {
19 URL string `json:"url"`
20 Format string `json:"format"`
21 Timeout int `json:"timeout,omitempty"`
22}
23
24type FetchPermissionsParams struct {
25 URL string `json:"url"`
26 Format string `json:"format"`
27 Timeout int `json:"timeout,omitempty"`
28}
29
30type fetchTool struct {
31 client *http.Client
32 permissions permission.Service
33}
34
35const (
36 FetchToolName = "fetch"
37 fetchToolDescription = `Fetches content from a URL and returns it in the specified format.
38
39WHEN TO USE THIS TOOL:
40- Use when you need to download content from a URL
41- Helpful for retrieving documentation, API responses, or web content
42- Useful for getting external information to assist with tasks
43
44HOW TO USE:
45- Provide the URL to fetch content from
46- Specify the desired output format (text, markdown, or html)
47- Optionally set a timeout for the request
48
49FEATURES:
50- Supports three output formats: text, markdown, and html
51- Automatically handles HTTP redirects
52- Sets reasonable timeouts to prevent hanging
53- Validates input parameters before making requests
54
55LIMITATIONS:
56- Maximum response size is 5MB
57- Only supports HTTP and HTTPS protocols
58- Cannot handle authentication or cookies
59- Some websites may block automated requests
60
61TIPS:
62- Use text format for plain text content or simple API responses
63- Use markdown format for content that should be rendered with formatting
64- Use html format when you need the raw HTML structure
65- Set appropriate timeouts for potentially slow websites`
66)
67
68func NewFetchTool(permissions permission.Service) BaseTool {
69 return &fetchTool{
70 client: &http.Client{
71 Timeout: 30 * time.Second,
72 },
73 permissions: permissions,
74 }
75}
76
77func (t *fetchTool) Info() ToolInfo {
78 return ToolInfo{
79 Name: FetchToolName,
80 Description: fetchToolDescription,
81 Parameters: map[string]any{
82 "url": map[string]any{
83 "type": "string",
84 "description": "The URL to fetch content from",
85 },
86 "format": map[string]any{
87 "type": "string",
88 "description": "The format to return the content in (text, markdown, or html)",
89 "enum": []string{"text", "markdown", "html"},
90 },
91 "timeout": map[string]any{
92 "type": "number",
93 "description": "Optional timeout in seconds (max 120)",
94 },
95 },
96 Required: []string{"url", "format"},
97 }
98}
99
100func (t *fetchTool) Run(ctx context.Context, call ToolCall) (ToolResponse, error) {
101 var params FetchParams
102 if err := json.Unmarshal([]byte(call.Input), ¶ms); err != nil {
103 return NewTextErrorResponse("Failed to parse fetch parameters: " + err.Error()), nil
104 }
105
106 if params.URL == "" {
107 return NewTextErrorResponse("URL parameter is required"), nil
108 }
109
110 format := strings.ToLower(params.Format)
111 if format != "text" && format != "markdown" && format != "html" {
112 return NewTextErrorResponse("Format must be one of: text, markdown, html"), nil
113 }
114
115 if !strings.HasPrefix(params.URL, "http://") && !strings.HasPrefix(params.URL, "https://") {
116 return NewTextErrorResponse("URL must start with http:// or https://"), nil
117 }
118
119 sessionID, messageID := GetContextValues(ctx)
120 if sessionID == "" || messageID == "" {
121 return ToolResponse{}, fmt.Errorf("session ID and message ID are required for creating a new file")
122 }
123
124 p := t.permissions.Request(
125 permission.CreatePermissionRequest{
126 SessionID: sessionID,
127 Path: config.WorkingDirectory(),
128 ToolName: FetchToolName,
129 Action: "fetch",
130 Description: fmt.Sprintf("Fetch content from URL: %s", params.URL),
131 Params: FetchPermissionsParams(params),
132 },
133 )
134
135 if !p {
136 return ToolResponse{}, permission.ErrorPermissionDenied
137 }
138
139 client := t.client
140 if params.Timeout > 0 {
141 maxTimeout := 120 // 2 minutes
142 if params.Timeout > maxTimeout {
143 params.Timeout = maxTimeout
144 }
145 client = &http.Client{
146 Timeout: time.Duration(params.Timeout) * time.Second,
147 }
148 }
149
150 req, err := http.NewRequestWithContext(ctx, "GET", params.URL, nil)
151 if err != nil {
152 return ToolResponse{}, fmt.Errorf("failed to create request: %w", err)
153 }
154
155 req.Header.Set("User-Agent", "opencode/1.0")
156
157 resp, err := client.Do(req)
158 if err != nil {
159 return ToolResponse{}, fmt.Errorf("failed to fetch URL: %w", err)
160 }
161 defer resp.Body.Close()
162
163 if resp.StatusCode != http.StatusOK {
164 return NewTextErrorResponse(fmt.Sprintf("Request failed with status code: %d", resp.StatusCode)), nil
165 }
166
167 maxSize := int64(5 * 1024 * 1024) // 5MB
168 body, err := io.ReadAll(io.LimitReader(resp.Body, maxSize))
169 if err != nil {
170 return NewTextErrorResponse("Failed to read response body: " + err.Error()), nil
171 }
172
173 content := string(body)
174 contentType := resp.Header.Get("Content-Type")
175
176 switch format {
177 case "text":
178 if strings.Contains(contentType, "text/html") {
179 text, err := extractTextFromHTML(content)
180 if err != nil {
181 return NewTextErrorResponse("Failed to extract text from HTML: " + err.Error()), nil
182 }
183 return NewTextResponse(text), nil
184 }
185 return NewTextResponse(content), nil
186
187 case "markdown":
188 if strings.Contains(contentType, "text/html") {
189 markdown, err := convertHTMLToMarkdown(content)
190 if err != nil {
191 return NewTextErrorResponse("Failed to convert HTML to Markdown: " + err.Error()), nil
192 }
193 return NewTextResponse(markdown), nil
194 }
195
196 return NewTextResponse("```\n" + content + "\n```"), nil
197
198 case "html":
199 return NewTextResponse(content), nil
200
201 default:
202 return NewTextResponse(content), nil
203 }
204}
205
206func extractTextFromHTML(html string) (string, error) {
207 doc, err := goquery.NewDocumentFromReader(strings.NewReader(html))
208 if err != nil {
209 return "", err
210 }
211
212 text := doc.Text()
213 text = strings.Join(strings.Fields(text), " ")
214
215 return text, nil
216}
217
218func convertHTMLToMarkdown(html string) (string, error) {
219 converter := md.NewConverter("", true, nil)
220
221 markdown, err := converter.ConvertString(html)
222 if err != nil {
223 return "", err
224 }
225
226 return markdown, nil
227}