sync: phase 1 backend + frontend from server

internal/embed/embed.go

@@ -0,0 +1,149 @@
+package embed
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"io"
+	"net/http"
+	"regexp"
+	"strings"
+	"time"
+)
+
+var urlRegex = regexp.MustCompile(`https?://[^\s<>"{}|\^\[\]]+`)
+
+// Embed represents a stored link preview.
+type Embed struct {
+	ID          string `json:"id"`
+	MessageID   string `json:"message_id"`
+	URL         string `json:"url"`
+	Title       string `json:"title"`
+	Description string `json:"description"`
+	ImageURL    string `json:"image_url"`
+	SiteName    string `json:"site_name"`
+}
+
+// ExtractURLs returns all HTTP/HTTPS URLs found in text.
+func ExtractURLs(text string) []string {
+	matches := urlRegex.FindAllString(text, -1)
+	seen := make(map[string]struct{})
+	var out []string
+	for _, u := range matches {
+		if _, ok := seen[u]; ok {
+			continue
+		}
+		seen[u] = struct{}{}
+		out = append(out, u)
+	}
+	if len(out) > 5 {
+		out = out[:5]
+	}
+	return out
+}
+
+// FetchEmbed retrieves OpenGraph meta tags for a URL.
+func FetchEmbed(url string) *Embed {
+	client := &http.Client{Timeout: 2 * time.Second}
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil
+	}
+	req.Header.Set("User-Agent", "Mozilla/5.0 (compatible; DumpsterBot/1.0)")
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil
+	}
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 256*1024))
+	if err != nil {
+		return nil
+	}
+	html := string(body)
+	return &Embed{
+		URL:         url,
+		Title:       ogTag(html, "og:title"),
+		Description: ogTag(html, "og:description"),
+		ImageURL:    ogTag(html, "og:image"),
+		SiteName:    ogTag(html, "og:site_name"),
+	}
+}
+
+func ogTag(html, property string) string {
+	// Try property
+	re := regexp.MustCompile(`<meta[^>]+property=["']` + regexp.QuoteMeta(property) + `["'][^>]+content=["']([^"']*)["']`)
+	m := re.FindStringSubmatch(html)
+	if len(m) > 1 && m[1] != "" {
+		return strings.TrimSpace(m[1])
+	}
+	// Try name
+	re = regexp.MustCompile(`<meta[^>]+name=["']` + regexp.QuoteMeta(property) + `["'][^>]+content=["']([^"']*)["']`)
+	m = re.FindStringSubmatch(html)
+	if len(m) > 1 && m[1] != "" {
+		return strings.TrimSpace(m[1])
+	}
+	// Fallback for title
+	if property == "og:title" {
+		re = regexp.MustCompile(`<title[^>]*>([^<]+)</title>`)
+		m = re.FindStringSubmatch(html)
+		if len(m) > 1 {
+			return strings.TrimSpace(m[1])
+		}
+	}
+	return ""
+}
+
+// FetchAndStore extracts URLs from content, fetches embeds, and stores them.
+func FetchAndStore(db *sql.DB, messageID string, content string) {
+	urls := ExtractURLs(content)
+	if len(urls) == 0 {
+		return
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
+	defer cancel()
+	for _, url := range urls {
+		emb := FetchEmbed(url)
+		if emb == nil || (emb.Title == "" && emb.Description == "" && emb.ImageURL == "") {
+			continue
+		}
+		_, err := db.ExecContext(ctx, `
+			INSERT INTO embeds (message_id, url, title, description, image_url, site_name)
+			VALUES ($1, $2, $3, $4, $5, $6)
+		`, messageID, emb.URL, emb.Title, emb.Description, emb.ImageURL, emb.SiteName)
+		if err != nil {
+			fmt.Printf("failed to store embed: %v\n", err)
+		}
+	}
+}
+
+// LoadForMessages returns embeds grouped by message_id.
+func LoadForMessages(ctx context.Context, db *sql.DB, messageIDs []string) (map[string][]Embed, error) {
+	result := make(map[string][]Embed)
+	if len(messageIDs) == 0 {
+		return result, nil
+	}
+	placeholders := make([]string, len(messageIDs))
+	args := make([]interface{}, len(messageIDs))
+	for i, id := range messageIDs {
+		placeholders[i] = fmt.Sprintf("$%d", i+1)
+		args[i] = id
+	}
+	query := "SELECT message_id, id, url, title, description, image_url, site_name FROM embeds WHERE message_id IN (" + strings.Join(placeholders, ",") + ")"
+	rows, err := db.QueryContext(ctx, query, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var e Embed
+		var mid string
+		if err := rows.Scan(&mid, &e.ID, &e.URL, &e.Title, &e.Description, &e.ImageURL, &e.SiteName); err != nil {
+			continue
+		}
+		result[mid] = append(result[mid], e)
+	}
+	return result, nil
+}