feat(orion): add endpoint for link metadata
This commit is contained in:
Arjun Patel
+15
-2
@@ -6,6 +6,7 @@ import (
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"log/slog"
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"net/http"
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"os"
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"strings"
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"cloud.google.com/go/firestore"
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"cloud.google.com/go/storage"
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@@ -173,6 +174,9 @@ func main() {
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// Particles
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mux.Handle("GET /particles/{id}/download", withAuth(h.DownloadParticleMedia))
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// Link metadata
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mux.Handle("GET /metadata", withAuth(h.GetLinkMetadata))
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// Depot
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mux.Handle("POST /depot/upload", withAuth(h.PrepareUpload))
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mux.Handle("POST /depot/objects/{id}/confirm", withAuth(h.ConfirmUpload))
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@@ -185,8 +189,17 @@ func main() {
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mux.Handle("GET /waitlist/{email}", withAuth(h.GetWaitlistEntry))
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mux.Handle("POST /waitlist/invite", withAuth(h.InviteWaitlistEntrant))
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// nil = allow all origins (Electron app needs it).
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muxWithCors := middleware.CORS(nil)(mux)
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// CORS_ALLOWED_ORIGINS is a comma-separated whitelist for the web client.
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// Empty / unset = allow all
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var allowedOrigins []string
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if raw := os.Getenv("CORS_ALLOWED_ORIGINS"); raw != "" {
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for _, o := range strings.Split(raw, ",") {
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if o = strings.TrimSpace(o); o != "" {
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allowedOrigins = append(allowedOrigins, o)
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}
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}
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}
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muxWithCors := middleware.CORS(allowedOrigins)(mux)
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addr := fmt.Sprintf("0.0.0.0:%s", port)
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slog.Info("running server", "addr", addr)
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@@ -0,0 +1,213 @@
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package handler
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import (
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"context"
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"errors"
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"io"
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"log/slog"
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"net"
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"net/http"
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"net/url"
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"regexp"
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"strings"
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"sync"
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"time"
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)
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// LinkMetadata mirrors the TS shape in
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// `js/desktop/src/lib/link-metadata.ts`. The Electron client does this fetch
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// in its main process; the web client can't (browser CORS), so it calls this
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// endpoint instead.
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type LinkMetadata struct {
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URL string `json:"url"`
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Title *string `json:"title"`
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Description *string `json:"description"`
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Image *string `json:"image"`
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Favicon *string `json:"favicon"`
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Domain string `json:"domain"`
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}
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const (
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metadataFetchTimeout = 5 * time.Second
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metadataMaxBytes = 50 * 1024
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metadataUserAgent = "Mozilla/5.0 (compatible; llink/1.0)"
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)
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// In-process cache, unbounded but only successful results are stored. Mirrors
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// the Electron-main implementation; URL space is bounded in practice.
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var metadataCache sync.Map // map[string]LinkMetadata
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func (h *Handler) GetLinkMetadata(w http.ResponseWriter, r *http.Request) {
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raw := r.URL.Query().Get("url")
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if raw == "" {
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http.Error(w, "url is required", http.StatusBadRequest)
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return
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}
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parsed, err := url.Parse(raw)
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if err != nil || (parsed.Scheme != "http" && parsed.Scheme != "https") || parsed.Host == "" {
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http.Error(w, "invalid url", http.StatusBadRequest)
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return
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}
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if cached, ok := metadataCache.Load(raw); ok {
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writeJSON(w, cached)
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return
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}
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if err := guardSSRF(parsed.Hostname()); err != nil {
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// Treat unresolvable / private hosts as "no metadata" rather than 4xx — the
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// client treats a null body as a progressive-enhancement miss.
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writeJSON(w, nil)
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return
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}
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meta, err := fetchLinkMetadata(r.Context(), parsed)
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if err != nil {
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slog.Warn("link metadata fetch failed", "url", raw, "error", err)
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writeJSON(w, nil)
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return
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}
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metadataCache.Store(raw, *meta)
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writeJSON(w, meta)
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}
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// guardSSRF resolves the host and rejects loopback, private, link-local, and
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// unspecified addresses so the endpoint can't be turned into an internal-network
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// probe.
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func guardSSRF(host string) error {
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ips, err := net.LookupIP(host)
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if err != nil {
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return err
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}
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if len(ips) == 0 {
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return errors.New("no addresses for host")
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}
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for _, ip := range ips {
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if ip.IsLoopback() || ip.IsPrivate() || ip.IsLinkLocalUnicast() ||
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ip.IsLinkLocalMulticast() || ip.IsUnspecified() {
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return errors.New("private or local address")
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}
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}
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return nil
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}
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func fetchLinkMetadata(ctx context.Context, target *url.URL) (*LinkMetadata, error) {
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ctx, cancel := context.WithTimeout(ctx, metadataFetchTimeout)
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defer cancel()
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req, err := http.NewRequestWithContext(ctx, http.MethodGet, target.String(), nil)
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if err != nil {
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return nil, err
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}
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req.Header.Set("User-Agent", metadataUserAgent)
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req.Header.Set("Accept", "text/html")
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resp, err := http.DefaultClient.Do(req)
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if err != nil {
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return nil, err
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}
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defer resp.Body.Close()
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if resp.StatusCode < 200 || resp.StatusCode >= 300 {
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return nil, errors.New("upstream non-2xx")
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}
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body, err := io.ReadAll(io.LimitReader(resp.Body, metadataMaxBytes))
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if err != nil {
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return nil, err
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}
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html := string(body)
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domain := strings.TrimPrefix(target.Hostname(), "www.")
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title := firstNonNil(metaContent(html, "og:title"), parseTitle(html))
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description := firstNonNil(
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metaContent(html, "og:description"),
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metaContent(html, "description"),
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)
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image := resolveURL(metaContent(html, "og:image"), target)
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favicon := parseFavicon(html, target)
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return &LinkMetadata{
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URL: target.String(),
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Title: title,
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Description: description,
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Image: image,
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Favicon: favicon,
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Domain: domain,
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}, nil
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}
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// Regex patterns mirror the JS impl in `js/desktop/src/main.ts` so both clients
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// derive the same metadata until the JS path is retired.
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var titleRe = regexp.MustCompile(`(?i)<title[^>]*>([^<]*)</title>`)
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func parseTitle(html string) *string {
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m := titleRe.FindStringSubmatch(html)
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if len(m) < 2 {
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return nil
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}
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s := strings.TrimSpace(m[1])
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if s == "" {
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return nil
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}
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return &s
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}
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// metaContent finds <meta property|name="<prop>" content="..."> in either attribute order.
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func metaContent(html, prop string) *string {
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escaped := regexp.QuoteMeta(prop)
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re := regexp.MustCompile(
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`(?i)<meta[^>]*(?:property|name)=["']` + escaped + `["'][^>]*content=["']([^"']*)["']` +
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`|<meta[^>]*content=["']([^"']*)["'][^>]*(?:property|name)=["']` + escaped + `["']`,
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)
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m := re.FindStringSubmatch(html)
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if len(m) == 0 {
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return nil
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}
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for _, g := range m[1:] {
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if g != "" {
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return &g
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}
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}
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return nil
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}
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var (
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faviconRe1 = regexp.MustCompile(`(?i)<link[^>]*rel=["'](?:shortcut )?icon["'][^>]*href=["']([^"']*)["']`)
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faviconRe2 = regexp.MustCompile(`(?i)<link[^>]*href=["']([^"']*)["'][^>]*rel=["'](?:shortcut )?icon["']`)
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)
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func parseFavicon(html string, base *url.URL) *string {
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for _, re := range []*regexp.Regexp{faviconRe1, faviconRe2} {
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if m := re.FindStringSubmatch(html); len(m) >= 2 {
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return resolveURL(&m[1], base)
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}
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}
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// Fall back to /favicon.ico
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fallback := (&url.URL{Scheme: base.Scheme, Host: base.Host, Path: "/favicon.ico"}).String()
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return &fallback
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}
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func resolveURL(src *string, base *url.URL) *string {
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if src == nil || *src == "" {
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return nil
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}
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parsed, err := url.Parse(*src)
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if err != nil {
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return src
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}
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resolved := base.ResolveReference(parsed).String()
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return &resolved
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}
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func firstNonNil(values ...*string) *string {
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for _, v := range values {
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if v != nil && *v != "" {
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return v
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}
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}
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return nil
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}
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@@ -79,6 +79,9 @@ spec:
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value: "llink://billing/success"
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- name: "BILLING_CANCEL_URL"
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value: "llink://billing/cancel"
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# Web client origins
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- name: "CORS_ALLOWED_ORIGINS"
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value: "http://localhost:5173,http://localhost:5174,http://localhost:5175,https://llink.dev.flowy.live"
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---
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@@ -76,6 +76,9 @@ spec:
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value: "llink://billing/success"
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- name: "BILLING_CANCEL_URL"
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value: "llink://billing/cancel"
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# Web client origins
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- name: "CORS_ALLOWED_ORIGINS"
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value: "https://llink.flowy.live"
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---
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