can also fetch first image for the preview

2 files changed, 110 insertions, 30 deletions

diff --git a/internal/platforms/linkedin/preview.go b/internal/platforms/linkedin/preview.go
index 1c0e5a7..03bf7e6 100644
--- a/internal/platforms/linkedin/preview.go
+++ b/internal/platforms/linkedin/preview.go
@@ -6,26 +6,30 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"net/url"
 
 	"golang.org/x/net/html"
 )
 
-var errNoTitleElementFound = errors.New("no title element found")
+var (
+	errNoTitleElementFound = errors.New("no title element found")
+	errNoImageElementFound = errors.New("no image element found")
+)
 
 type preview struct {
-	title, url string
+	title, imageURL, url string
 }
 
 func NewPreview(ctx context.Context, urls []string) (preview, error) {
 	if len(urls) == 0 {
 		return preview{}, nil
 	}
-	title, err := fetchHTMLTitle(ctx, urls[0])
+	title, imageURL, err := fetchHTMLTitleAndFirstImage(ctx, urls[0])
 	if errors.Is(err, errNoTitleElementFound) || (err == nil && title == "") {
 		log.Println("Setting title to", urls[0])
 		title = urls[0]
 	}
-	return preview{title: title, url: urls[0]}, err
+	return preview{title: title, imageURL: imageURL, url: urls[0]}, err
 }
 
 func (p preview) String() string {
@@ -36,47 +40,97 @@ func (p preview) Empty() bool {
 	return p.url == ""
 }
 
-func fetchHTMLTitle(ctx context.Context, url string) (string, error) {
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+func findTitle(n *html.Node) (string, error) {
+	var title string
+	var traverse func(*html.Node)
+	traverse = func(n *html.Node) {
+		if n.Type == html.ElementNode && n.Data == "title" {
+			if n.FirstChild != nil {
+				title = n.FirstChild.Data
+			}
+			return
+		}
+		for c := n.FirstChild; c != nil; c = c.NextSibling {
+			traverse(c)
+		}
+	}
+	traverse(n)
+	if title == "" {
+		return "", errNoTitleElementFound
+	}
+	return title, nil
+}
+
+func findFirstImage(n *html.Node) (string, error) {
+	var imageURL string
+	var traverse func(*html.Node) bool
+	traverse = func(n *html.Node) bool {
+		if n.Type == html.ElementNode && n.Data == "img" {
+			for _, attr := range n.Attr {
+				if attr.Key == "src" {
+					imageURL = attr.Val
+					return true // Stop searching when the first image's URL is found
+				}
+			}
+		}
+		for c := n.FirstChild; c != nil; c = c.NextSibling {
+			if traverse(c) {
+				return true
+			}
+		}
+		return false
+	}
+	if !traverse(n) {
+		return "", errNoImageElementFound
+	}
+	return imageURL, nil
+}
+
+func resolveURL(baseURL, rawURL string) (string, error) {
+	base, err := url.Parse(baseURL)
+	if err != nil {
+		return "", fmt.Errorf("failed to parse base URL: %w", err)
+	}
+	u, err := url.Parse(rawURL)
 	if err != nil {
-		return "", fmt.Errorf("failed to create request: %w", err)
+		return "", fmt.Errorf("failed to parse raw URL: %w", err)
 	}
+	return base.ResolveReference(u).String(), nil
+}
 
+func fetchHTMLTitleAndFirstImage(ctx context.Context, url string) (string, string, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return "", "", fmt.Errorf("failed to create request: %w", err)
+	}
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
-		return "", fmt.Errorf("failed to get URL: %w", err)
+		return "", "", fmt.Errorf("failed to get URL: %w", err)
 	}
 	defer resp.Body.Close()
 
 	if resp.StatusCode != http.StatusOK {
-		return "", fmt.Errorf("failed to get a successful response: %v", resp.StatusCode)
+		return "", "", fmt.Errorf("failed to get a successful response: %v", resp.StatusCode)
 	}
-
 	doc, err := html.Parse(resp.Body)
 	if err != nil {
-		return "", fmt.Errorf("failed to parse HTML: %w", err)
+		return "", "", fmt.Errorf("failed to parse HTML: %w", err)
 	}
 
-	// Traverse the document and find the <title> tag
-	var title string
-	var f func(*html.Node)
-	f = func(n *html.Node) {
-		if n.Type == html.ElementNode && n.Data == "title" {
-			if n.FirstChild != nil {
-				title = n.FirstChild.Data
-			}
-			return
-		}
-		for c := n.FirstChild; c != nil; c = c.NextSibling {
-			f(c)
-		}
+	var errs error
+	title, err := findTitle(doc)
+	if err != nil {
+		errs = errors.Join(errs, err)
 	}
 
-	// Call the function to search for the title
-	f(doc)
-
-	if title == "" {
-		return "", errNoTitleElementFound
+	imageURL, err := findFirstImage(doc)
+	if err != nil {
+		errs = errors.Join(errs, err)
+	} else if imageURL != "" {
+		if imageURL, err = resolveURL(url, imageURL); err != nil {
+			errs = errors.Join(errs, err)
+		}
 	}
-	return title, nil
+
+	return title, imageURL, errs
 }
diff --git a/internal/platforms/linkedin/preview_test.go b/internal/platforms/linkedin/preview_test.go
new file mode 100644
index 0000000..ea47d08
--- /dev/null
+++ b/internal/platforms/linkedin/preview_test.go
@@ -0,0 +1,26 @@
+package linkedin
+
+import (
+	"context"
+	"testing"
+)
+
+// TODO: Mock the http request, and serve a local HTML page!
+func TestFetchHTMLTitleAndFirstImage(t *testing.T) {
+	var (
+		url              = "https://foo.zone/about/"
+		expectedTitle    = "About"
+		expectedImageURL = "https://foo.zone/about/paul.jpg"
+	)
+
+	title, imageURL, err := fetchHTMLTitleAndFirstImage(context.Background(), url)
+	if err != nil {
+		t.Error(err)
+	}
+	if title != expectedTitle {
+		t.Errorf("expected title '%s' but got '%s'", expectedTitle, title)
+	}
+	if imageURL != expectedImageURL {
+		t.Errorf("expected imageURL '%s' but got '%s'", expectedImageURL, imageURL)
+	}
+}