create ElementClass struct

TODO: test struct methods, integration with Node and tests within Node

.gitignore

@@ -1 +1,5 @@
-target/
+target/
+
+# vim
+*.swp*
+*.swo*

src/html5_parser/element_class.rs

@@ -0,0 +1,54 @@
+use std::collections::HashMap;
+
+pub struct ElementClass {
+    /// a map of classes applied to an HTML element.
+    /// key = name, value = is_active
+    /// the is_active is used to toggle a class (JavaScript API)
+    class_map: HashMap<String, bool>,
+}
+
+impl ElementClass {
+    /// Check if class name exists
+    pub fn contains(&self, name: &str) -> bool {
+        self.class_map.contains_key(name)
+    }
+
+    /// Add a new class (if already exists, does nothing)
+    pub fn add(&mut self, name: &str) -> () {
+        // by default, adding a new class will be active.
+        // however, map.insert will update a key if it exists
+        // and we don't want to overwrite an inactive class to make it active unintentionally
+        // so we ignore this operation if the class already exists
+        if !self.contains(name) {
+            self.class_map.insert(name.to_owned(), true);
+        }
+    }
+
+    /// Remove a class (does nothing if not exists)
+    pub fn remove(&mut self, name: &str) -> () {
+        self.class_map.remove(name);
+    }
+
+    /// Toggle a class active/inactive. Does nothing if class doesn't exist
+    pub fn toggle(&mut self, name: &str) {
+        if let Some(is_active) = self.class_map.get_mut(name) {
+            *is_active = !*is_active;
+        }
+    }
+
+    /// Set explicitly if a class is active or not. Does nothing if class doesn't exist
+    pub fn set_active(&mut self, name: &str, is_active: bool) -> () {
+        if let Some(is_active_item) = self.class_map.get_mut(name) {
+            *is_active_item = is_active;
+        }
+    }
+
+    /// Check if a class is active. Returns false if class doesn't exist
+    pub fn is_active(&self, name: &str) -> bool {
+        if let Some(is_active) = self.class_map.get(name) {
+            return *is_active;
+        }
+
+        return false;
+    }
+}

src/html5_parser/mod.rs

@@ -7,4 +7,6 @@ pub mod dom;
 pub mod error_logger;
 pub mod input_stream;
 
+pub mod element_class;
+
 mod node_arena;