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messenger_linkpreview.go
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/
messenger_linkpreview.go
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package protocol
import (
"errors"
"fmt"
"net/http"
neturl "net/url"
"regexp"
"strings"
"go.uber.org/zap"
"golang.org/x/net/publicsuffix"
"github.com/status-im/markdown"
"github.com/status-im/status-go/protocol/common"
"github.com/status-im/status-go/protocol/linkpreview/unfurlers"
)
type LinkPreview struct {
common.LinkPreview
}
func normalizeHostname(hostname string) string {
hostname = strings.ToLower(hostname)
re := regexp.MustCompile(`^www\.(.*)$`)
return re.ReplaceAllString(hostname, "$1")
}
func (m *Messenger) newURLUnfurler(httpClient *http.Client, url *neturl.URL) unfurlers.Unfurler {
if unfurlers.IsSupportedImageURL(url) {
return unfurlers.NewImageUnfurler(
url,
m.logger,
httpClient)
}
switch normalizeHostname(url.Hostname()) {
case "reddit.com":
return unfurlers.NewOEmbedUnfurler(
"https://www.reddit.com/oembed",
url,
m.logger,
httpClient)
default:
return unfurlers.NewOpenGraphUnfurler(
url,
m.logger,
httpClient)
}
}
func (m *Messenger) unfurlURL(httpClient *http.Client, url string) (common.LinkPreview, error) {
var preview common.LinkPreview
parsedURL, err := neturl.Parse(url)
if err != nil {
return preview, err
}
unfurler := m.newURLUnfurler(httpClient, parsedURL)
preview, err = unfurler.Unfurl()
if err != nil {
return preview, err
}
preview.Hostname = strings.ToLower(parsedURL.Hostname())
return preview, nil
}
// parseValidURL is a stricter version of url.Parse that performs additional
// checks to ensure the URL is valid for clients to request a link preview.
func parseValidURL(rawURL string) (*neturl.URL, error) {
u, err := neturl.Parse(rawURL)
if err != nil {
return nil, fmt.Errorf("parsing URL failed: %w", err)
}
if u.Scheme == "" {
return nil, errors.New("missing URL scheme")
}
_, err = publicsuffix.EffectiveTLDPlusOne(u.Hostname())
if err != nil {
return nil, fmt.Errorf("missing known URL domain: %w", err)
}
return u, nil
}
// GetURLs returns only what we consider unfurleable URLs.
//
// If we wanted to be extra precise and help improve UX, we could ignore URLs
// that we know can't be unfurled. This is at least possible with the oEmbed
// protocol because providers must specify an endpoint scheme.
func GetURLs(text string) []string {
parsedText := markdown.Parse([]byte(text), nil)
visitor := common.RunLinksVisitor(parsedText)
urls := make([]string, 0, len(visitor.Links))
indexed := make(map[string]any, len(visitor.Links))
for _, rawURL := range visitor.Links {
parsedURL, err := parseValidURL(rawURL)
if err != nil {
continue
}
// Lowercase the host so the URL can be used as a cache key. Particularly on
// mobile clients it is common that the first character in a text input is
// automatically uppercased. In WhatsApp they incorrectly lowercase the
// URL's path, but this is incorrect. For instance, some URL shorteners are
// case-sensitive, some websites encode base64 in the path, etc.
parsedURL.Host = strings.ToLower(parsedURL.Host)
idx := parsedURL.String()
// Removes the spurious trailing forward slash.
idx = strings.TrimRight(idx, "/")
if _, exists := indexed[idx]; exists {
continue
} else {
indexed[idx] = nil
urls = append(urls, idx)
}
}
return urls
}
func NewDefaultHTTPClient() *http.Client {
return &http.Client{Timeout: unfurlers.DefaultRequestTimeout}
}
// UnfurlURLs assumes clients pass URLs verbatim that were validated and
// processed by GetURLs.
func (m *Messenger) UnfurlURLs(httpClient *http.Client, urls []string) ([]common.LinkPreview, error) {
if httpClient == nil {
httpClient = NewDefaultHTTPClient()
}
previews := make([]common.LinkPreview, 0, len(urls))
for _, url := range urls {
m.logger.Debug("unfurling", zap.String("url", url))
p, err := m.unfurlURL(httpClient, url)
if err != nil {
m.logger.Info("failed to unfurl", zap.String("url", url), zap.Error(err))
continue
}
previews = append(previews, p)
}
return previews, nil
}