better logic for relative urls

pkg/appview/readme/fetcher.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"regexp"
 	"strings"
 	"time"
 
@@ -192,6 +193,15 @@ func (f *Fetcher) RenderMarkdown(content []byte) (string, error) {
 	return f.renderMarkdown(content, "")
 }
 
+// Regex patterns for matching relative URLs that need rewriting
+// These match src="..." or href="..." where the URL is relative (not absolute, not data:, not #anchor)
+var (
+	// Match src="filename" where filename doesn't start with http://, https://, //, /, #, data:, or mailto:
+	relativeSrcPattern = regexp.MustCompile(`src="([^"/:][^"]*)"`)
+	// Match href="filename" where filename doesn't start with http://, https://, //, /, #, data:, or mailto:
+	relativeHrefPattern = regexp.MustCompile(`href="([^"/:][^"]*)"`)
+)
+
 // rewriteRelativeURLs converts relative URLs to absolute URLs
 func rewriteRelativeURLs(html, baseURL string) string {
 	if baseURL == "" {
@@ -203,20 +213,51 @@ func rewriteRelativeURLs(html, baseURL string) string {
 		return html
 	}
 
-	// Simple string replacement for common patterns
-	// This is a basic implementation - for production, consider using an HTML parser
+	// Handle root-relative URLs (starting with /) first
+	// Must be done before bare relative URLs to avoid double-processing
+	if base.Scheme != "" && base.Host != "" {
+		root := fmt.Sprintf("%s://%s/", base.Scheme, base.Host)
+		// Replace src="/" and href="/" but not src="//" (protocol-relative URLs)
+		html = strings.ReplaceAll(html, `src="/`, fmt.Sprintf(`src="%s`, root))
+		html = strings.ReplaceAll(html, `href="/`, fmt.Sprintf(`href="%s`, root))
+	}
+
+	// Handle explicit relative paths (./something and ../something)
 	html = strings.ReplaceAll(html, `src="./`, fmt.Sprintf(`src="%s`, baseURL))
 	html = strings.ReplaceAll(html, `href="./`, fmt.Sprintf(`href="%s`, baseURL))
 	html = strings.ReplaceAll(html, `src="../`, fmt.Sprintf(`src="%s../`, baseURL))
 	html = strings.ReplaceAll(html, `href="../`, fmt.Sprintf(`href="%s../`, baseURL))
 
-	// Handle root-relative URLs (starting with /)
-	if base.Scheme != "" && base.Host != "" {
-		root := fmt.Sprintf("%s://%s/", base.Scheme, base.Host)
-		// Replace src="/" and href="/" but not src="//" (absolute URLs)
-		html = strings.ReplaceAll(html, `src="/`, fmt.Sprintf(`src="%s`, root))
-		html = strings.ReplaceAll(html, `href="/`, fmt.Sprintf(`href="%s`, root))
-	}
+	// Handle bare relative URLs (e.g., src="image.png" without ./ prefix)
+	// Skip URLs that are already absolute (start with http://, https://, or //)
+	// Skip anchors (#), data URLs (data:), and mailto links
+	html = relativeSrcPattern.ReplaceAllStringFunc(html, func(match string) string {
+		// Extract the URL from src="..."
+		url := match[5 : len(match)-1] // Remove 'src="' and '"'
+
+		// Skip if already processed or is a special URL type
+		if strings.HasPrefix(url, "http://") || strings.HasPrefix(url, "https://") ||
+			strings.HasPrefix(url, "//") || strings.HasPrefix(url, "#") ||
+			strings.HasPrefix(url, "data:") || strings.HasPrefix(url, "mailto:") {
+			return match
+		}
+
+		return fmt.Sprintf(`src="%s%s"`, baseURL, url)
+	})
+
+	html = relativeHrefPattern.ReplaceAllStringFunc(html, func(match string) string {
+		// Extract the URL from href="..."
+		url := match[6 : len(match)-1] // Remove 'href="' and '"'
+
+		// Skip if already processed or is a special URL type
+		if strings.HasPrefix(url, "http://") || strings.HasPrefix(url, "https://") ||
+			strings.HasPrefix(url, "//") || strings.HasPrefix(url, "#") ||
+			strings.HasPrefix(url, "data:") || strings.HasPrefix(url, "mailto:") {
+			return match
+		}
+
+		return fmt.Sprintf(`href="%s%s"`, baseURL, url)
+	})
 
 	return html
 }

pkg/appview/readme/fetcher_test.go

@@ -145,6 +145,48 @@ func TestRewriteRelativeURLs(t *testing.T) {
 			baseURL:  "https://example.com/docs/",
 			expected: `<img src="https://example.com//cdn.example.com/image.png">`,
 		},
+		{
+			name:     "bare relative src (no ./ prefix)",
+			html:     `<img src="image.png">`,
+			baseURL:  "https://example.com/docs/",
+			expected: `<img src="https://example.com/docs/image.png">`,
+		},
+		{
+			name:     "bare relative href (no ./ prefix)",
+			html:     `<a href="page.html">link</a>`,
+			baseURL:  "https://example.com/docs/",
+			expected: `<a href="https://example.com/docs/page.html">link</a>`,
+		},
+		{
+			name:     "bare relative with path",
+			html:     `<img src="images/logo.png">`,
+			baseURL:  "https://example.com/docs/",
+			expected: `<img src="https://example.com/docs/images/logo.png">`,
+		},
+		{
+			name:     "anchor links unchanged",
+			html:     `<a href="#section">link</a>`,
+			baseURL:  "https://example.com/docs/",
+			expected: `<a href="#section">link</a>`,
+		},
+		{
+			name:     "data URLs unchanged",
+			html:     `<img src="data:image/png;base64,abc123">`,
+			baseURL:  "https://example.com/docs/",
+			expected: `<img src="data:image/png;base64,abc123">`,
+		},
+		{
+			name:     "mailto links unchanged",
+			html:     `<a href="mailto:test@example.com">email</a>`,
+			baseURL:  "https://example.com/docs/",
+			expected: `<a href="mailto:test@example.com">email</a>`,
+		},
+		{
+			name:     "mixed bare and prefixed relative URLs",
+			html:     `<img src="slices_and_lucy.png"><a href="./other.md">link</a>`,
+			baseURL:  "https://github.com/user/repo/blob/main/",
+			expected: `<img src="https://github.com/user/repo/blob/main/slices_and_lucy.png"><a href="https://github.com/user/repo/blob/main/other.md">link</a>`,
+		},
 	}
 
 	for _, tt := range tests {