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package main
import (
"fmt"
"io"
"net/http"
"net/url"
"strings"
"time"
)
// fetch makes a GET request to refURL, returning the HTML contents of
// that webpage. An error is also returned.
//
// A [url.URL] type is used for refURL to simplify recursive or else
// repeated use of this function when crawling webpages to, say, build
// a sitemap.
func fetch(refURL url.URL) ([]byte, error) {
rawURL := refURL.String()
// FIXME: make the timeout configurable.
client := http.Client{
Timeout: 2 * time.Second,
}
req, err := http.NewRequest(http.MethodGet, rawURL, nil)
if err != nil {
return nil, fmt.Errorf("can't create request: %w", err)
}
req.Header.Add("user-agent", "urls/1.0, GNU/Linux")
resp, err := client.Do(req)
if err != nil {
return nil, fmt.Errorf("client failed: %w", err)
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("status for %s for %s: %s", http.MethodGet, rawURL, resp.Status)
}
if contentType := resp.Header.Get("content-type"); !goodContentType(contentType) {
return nil, fmt.Errorf("non-html content-type: %s", contentType)
}
htmlBytes, err := io.ReadAll(resp.Body)
if err != nil {
return nil, fmt.Errorf("can't read reponse body into byte buffer")
}
return htmlBytes, nil
}
func goodContentType(contentType string) bool {
what := strings.TrimSpace(strings.SplitN(contentType, ";", 2)[0])
return what == "text/html"
}
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