package services import ( "context" "fmt" "io" "net/http" neturl "net/url" "regexp" "strings" "sync" "time" ) // LinkPreview adalah hasil ringkas OpenGraph/fallback dari satu URL. type LinkPreview struct { URL string `json:"url"` Title string `json:"title"` Description string `json:"description,omitempty"` Image string `json:"image,omitempty"` SiteName string `json:"site_name,omitempty"` Favicon string `json:"favicon,omitempty"` } // linkPreviewCache membatasi fetch berulang URL yang sama (thread panjang, // bubble lama yang masuk viewport). Entry kecil; LRU sederhana via umur. var linkPreviewCache = struct { sync.Mutex items map[string]linkPreviewEntry maxItems int }{items: make(map[string]linkPreviewEntry), maxItems: 200} type linkPreviewEntry struct { preview LinkPreview fetchedAt time.Time } const ( linkPreviewTTL = 10 * time.Minute linkPreviewMaxBody = 256 << 10 // 256 KB cukup untuk linkPreviewRedirect = 5 ) var ( ogTitleRe = regexp.MustCompile(`(?is)]+property=["']og:title["'][^>]+content=["']([^"']{1,300})["']`) ogTitleReAlt = regexp.MustCompile(`(?is)]+content=["']([^"']{1,300})["'][^>]+property=["']og:title["']`) ogDescRe = regexp.MustCompile(`(?is)]+property=["']og:description["'][^>]+content=["']([^"']{1,600})["']`) ogDescReAlt = regexp.MustCompile(`(?is)]+content=["']([^"']{1,600})["'][^>]+property=["']og:description["']`) ogImageRe = regexp.MustCompile(`(?is)]+property=["']og:image["'][^>]+content=["']([^"']{1,1000})["']`) ogImageReAlt = regexp.MustCompile(`(?is)]+content=["']([^"']{1,1000})["'][^>]+property=["']og:image["']`) ogSiteRe = regexp.MustCompile(`(?is)]+property=["']og:site_name["'][^>]+content=["']([^"']{1,200})["']`) ogSiteReAlt = regexp.MustCompile(`(?is)]+content=["']([^"']{1,200})["'][^>]+property=["']og:site_name["']`) faviconLinkRe = regexp.MustCompile(`(?is)]+rel=["'](?:shortcut )?icon["'][^>]+href=["']([^"']{1,1000})["']`) faviconLinkReAlt = regexp.MustCompile(`(?is)]+href=["']([^"']{1,1000})["'][^>]+rel=["'](?:shortcut )?icon["']`) ) // FetchLinkPreview mengambil OpenGraph satu URL dengan proteksi SSRF yang sama // dengan enrichment AI. Kosong (bukan error) bila tidak ada data og/title. func FetchLinkPreview(rawURL string) (LinkPreview, error) { trimmed := strings.TrimSpace(rawURL) if err := assertPublicHTTPURL(trimmed); err != nil { return LinkPreview{}, err } key := strings.ToLower(trimmed) linkPreviewCache.Lock() if e, ok := linkPreviewCache.items[key]; ok && time.Since(e.fetchedAt) < linkPreviewTTL { linkPreviewCache.Unlock() return e.preview, nil } linkPreviewCache.Unlock() ctx, cancel := context.WithTimeout(context.Background(), 7*time.Second) defer cancel() client := NewPublicHTTPClient(7*time.Second, linkPreviewRedirect) req, err := http.NewRequestWithContext(ctx, http.MethodGet, trimmed, nil) if err != nil { return LinkPreview{}, err } req.Header.Set("User-Agent", "ChatLoopBot/1.0 (+link-preview; customer-service)") req.Header.Set("Accept", "text/html,application/xhtml+xml") resp, err := client.Do(req) if err != nil { return LinkPreview{}, err } defer resp.Body.Close() if resp.StatusCode < 200 || resp.StatusCode >= 400 { return LinkPreview{}, fmt.Errorf("HTTP %d", resp.StatusCode) } ct := strings.ToLower(resp.Header.Get("Content-Type")) if ct != "" && !strings.Contains(ct, "html") && !strings.Contains(ct, "text/plain") { return LinkPreview{}, fmt.Errorf("bukan HTML") } body, err := io.ReadAll(io.LimitReader(resp.Body, linkPreviewMaxBody)) if err != nil || len(body) == 0 { return LinkPreview{}, fmt.Errorf("body kosong") } final := trimmed if resp.Request != nil && resp.Request.URL != nil { final = resp.Request.URL.String() } base, _ := neturl.Parse(final) title := firstMatch(body, ogTitleRe, ogTitleReAlt) if title == "" { if m := htmlTitleRe.FindSubmatch(body); len(m) == 2 { title = cleanHTMLText(string(m[1])) } } desc := firstMatch(body, ogDescRe, ogDescReAlt) image := resolveRelative(base, firstMatch(body, ogImageRe, ogImageReAlt)) site := firstMatch(body, ogSiteRe, ogSiteReAlt) favicon := resolveRelative(base, firstMatch(body, faviconLinkRe, faviconLinkReAlt)) preview := LinkPreview{ URL: final, Title: cleanHTMLText(title), Description: cleanHTMLText(desc), Image: image, SiteName: cleanHTMLText(site), Favicon: favicon, } if preview.Title == "" && preview.Image == "" { return LinkPreview{}, fmt.Errorf("tidak ada data preview") } linkPreviewCache.Lock() if len(linkPreviewCache.items) >= linkPreviewCache.maxItems { // Buang setengah entri tertua bila penuh. now := time.Now() for k, e := range linkPreviewCache.items { if now.Sub(e.fetchedAt) > linkPreviewTTL/2 { delete(linkPreviewCache.items, k) } } } linkPreviewCache.items[key] = linkPreviewEntry{preview: preview, fetchedAt: time.Now()} linkPreviewCache.Unlock() return preview, nil } func firstMatch(body []byte, res ...*regexp.Regexp) string { for _, re := range res { if m := re.FindSubmatch(body); len(m) == 2 { if s := strings.TrimSpace(string(m[1])); s != "" { return s } } } return "" } // resolveRelative mengubah URL relatif (mis. "/img/cover.jpg") menjadi absolut // terhadap base; mengembalikan string kosong bila tidak valid. func resolveRelative(base *neturl.URL, raw string) string { raw = strings.TrimSpace(raw) if raw == "" || base == nil { return "" } u, err := neturl.Parse(raw) if err != nil { return "" } if u.IsAbs() { return u.String() } return base.ResolveReference(u).String() } // ClearLinkPreviewCacheForTest membersihkan cache (dipakai test regresi). func ClearLinkPreviewCacheForTest() { linkPreviewCache.Lock() linkPreviewCache.items = make(map[string]linkPreviewEntry) linkPreviewCache.Unlock() }