More work on HTML parsing.

The style tag parsing ideally needs rewriting using an actual CSS parser, but we can get away with this hacky approach in the short term.

src/main/java/org/qortal/api/resource/WebsiteResource.java

@@ -298,7 +298,7 @@ public class WebsiteResource {
             Elements href = document.select("[href]");
             for (Element element : href)  {
                 String elementHtml = element.attr("href");
-                if (!elementHtml.startsWith("http") && !elementHtml.startsWith("//")) {
+                if (this.isRelativeLink(elementHtml)) {
                     String slash = (elementHtml.startsWith("/") ? "" : File.separator);
                     element.attr("href", "/site/" +resourceId + slash + element.attr("href"));
                 }
@@ -306,16 +306,72 @@ public class WebsiteResource {
             Elements src = document.select("[src]");
             for (Element element : src)  {
                 String elementHtml = element.attr("src");
-                if (!elementHtml.startsWith("http") && !elementHtml.startsWith("//")) {
+                if (this.isRelativeLink(elementHtml)) {
                     String slash = (elementHtml.startsWith("/") ? "" : File.separator);
                     element.attr("src", "/site/" +resourceId + slash + element.attr("src"));
                 }
             }
+            Elements srcset = document.select("[srcset]");
+            for (Element element : srcset)  {
+                String elementHtml = element.attr("srcset").trim();
+                if (this.isRelativeLink(elementHtml)) {
+                    String[] parts = element.attr("srcset").split(",");
+                    ArrayList<String> newParts = new ArrayList<>();
+                    for (String part : parts) {
+                        part = part.trim();
+                        String slash = (elementHtml.startsWith("/") ? "" : File.separator);
+                        String newPart = "/site/" +resourceId + slash + part;
+                        newParts.add(newPart);
+                    }
+                    String newString = String.join(",", newParts);
+                    element.attr("srcset", newString);
+                }
+            }
+            Elements style = document.select("[style]");
+            for (Element element : style)  {
+                String elementHtml = element.attr("style");
+                if (elementHtml.contains("url(")) {
+                    String[] parts = elementHtml.split("url\\(");
+                    String[] parts2 = parts[1].split("\\)");
+                    String link = parts2[0];
+                    if (link != null) {
+                        link = this.removeQuotes(link);
+                        if (this.isRelativeLink(link)) {
+                            String slash = (link.startsWith("/") ? "" : File.separator);
+                            String modifiedLink = "url('" + "/site/" + resourceId + slash + link + "')";
+                            element.attr("style", parts[0] + modifiedLink + parts2[1]);
+                        }
+                    }
+                }
+            }
             return document.html().getBytes();
         }
         return data;
     }
 
+    private boolean isRelativeLink(String elementHtml) {
+        List<String> prefixes = new ArrayList<>();
+        prefixes.add("http");
+        prefixes.add("//");
+        prefixes.add("javascript:");
+        for (String prefix : prefixes) {
+            if (elementHtml.startsWith(prefix)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private String removeQuotes(String elementHtml) {
+        if (elementHtml.startsWith("\"") || elementHtml.startsWith("\'")) {
+            elementHtml = elementHtml.substring(1);
+        }
+        if (elementHtml.endsWith("\"") || elementHtml.endsWith("\'")) {
+            elementHtml = elementHtml.substring(0, elementHtml.length() - 1);
+        }
+        return elementHtml;
+    }
+
     private List<String> indexFiles() {
         List<String> indexFiles = new ArrayList<>();
         indexFiles.add("index.html");