From f53e58a3b86fd9cf3c3357fccfb5bbb4d500696b Mon Sep 17 00:00:00 2001
From: Manuel Thalmann <m@nuth.ch>
Date: Tue, 27 Sep 2022 13:05:36 +0200
Subject: [PATCH] Add a server for checking basic `XML` integrity

---
 .../nuth/zhaw/exbox/WellformedXmlServer.java  | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 app/src/main/java/ch/nuth/zhaw/exbox/WellformedXmlServer.java

diff --git a/app/src/main/java/ch/nuth/zhaw/exbox/WellformedXmlServer.java b/app/src/main/java/ch/nuth/zhaw/exbox/WellformedXmlServer.java
new file mode 100644
index 0000000..860b728
--- /dev/null
+++ b/app/src/main/java/ch/nuth/zhaw/exbox/WellformedXmlServer.java
@@ -0,0 +1,30 @@
+package ch.nuth.zhaw.exbox;
+
+import java.util.regex.MatchResult;
+import java.util.regex.Pattern;
+
+public class WellformedXmlServer implements CommandExecutor {
+    Pattern tagPattern = Pattern.compile("<(/?)(\\w+)( \\w+=\"[^\"]*\")*>");
+
+    @Override
+    public String execute(String command) throws Exception {
+        return Boolean.toString(checkWellformed(command)) + "\n";
+    }
+
+    public boolean checkWellformed(String code) {
+        ListStack openTags = new ListStack();
+        Iterable<MatchResult> results = () -> tagPattern.matcher(code).results().iterator();
+
+        for (MatchResult result : results) {
+            if (result.group(1).length() == 0) {
+                openTags.push(result.group(2));
+            } else if (result.group(2).equals(openTags.peek())) {
+                openTags.pop();
+            } else {
+                return false;
+            }
+        }
+
+        return openTags.isEmpty();
+    }
+}