initial commit

internal/reader/extract.go

@@ -0,0 +1,38 @@
+package reader
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/chromedp/cdproto/cdp"
+	"github.com/chromedp/chromedp"
+)
+
+// extractHTML returns the outer HTML of the first element matching
+// selector, or the full document HTML when selector is empty. It runs as
+// a separate chromedp.Run so a slow extraction does not re-do navigation.
+func (r *Reader) extractHTML(ctx context.Context, selector string) (string, error) {
+	if selector == "" {
+		var html string
+		if err := chromedp.Run(ctx, chromedp.OuterHTML("html", &html, chromedp.ByQuery)); err != nil {
+			return "", fmt.Errorf("read document: %w", err)
+		}
+		return html, nil
+	}
+
+	// Verify the selector matches at least one node; an empty result is
+	// almost always a caller mistake, not an empty page.
+	var nodes []*cdp.Node
+	if err := chromedp.Run(ctx, chromedp.Nodes(selector, &nodes, chromedp.ByQuery)); err != nil {
+		return "", fmt.Errorf("locate %q: %w", selector, err)
+	}
+	if len(nodes) == 0 {
+		return "", fmt.Errorf("selector %q matched no elements", selector)
+	}
+
+	var html string
+	if err := chromedp.Run(ctx, chromedp.OuterHTML(selector, &html, chromedp.ByQuery)); err != nil {
+		return "", fmt.Errorf("extract %q: %w", selector, err)
+	}
+	return html, nil
+}