feat: 🎸 add Equatable helper class

core/src/main/kotlin/tw/xcc/gumtree/api/Equatable.kt

@@ -0,0 +1,23 @@
+package tw.xcc.gumtree.api
+
+/**
+ * A base class to facilitate [operator ==] and [hashCode] overrides.
+ * */
+abstract class Equatable {
+    /**
+     * The list of properties that will be used to determine whether two instances are equal.
+     * */
+    protected abstract val equatableProps: List<Any?>
+
+    final override operator fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is Equatable) return false
+        if (equatableProps.size != other.equatableProps.size) return false
+        for (i in equatableProps.indices) {
+            if (equatableProps[i] != other.equatableProps[i]) return false
+        }
+        return true
+    }
+
+    final override fun hashCode(): Int = equatableProps.hashCode() xor javaClass.hashCode()
+}

core/src/main/kotlin/tw/xcc/gumtree/model/BasicTree.kt

@@ -1,12 +1,13 @@
 package tw.xcc.gumtree.model
 
+import tw.xcc.gumtree.api.Equatable
 import tw.xcc.gumtree.api.tree.Tree
 import java.util.concurrent.atomic.AtomicReference
 
 /**
  * The general thread-safe implementation of a tree structure.
  * */
-abstract class BasicTree<T> : Tree<T> where T : BasicTree<T> {
+abstract class BasicTree<T> : Equatable(), Tree<T> where T : BasicTree<T> {
     protected abstract val self: T
 
     private val _parent = AtomicReference<T?>()
@@ -50,9 +51,7 @@ abstract class BasicTree<T> : Tree<T> where T : BasicTree<T> {
 
     final override fun isLeaf(): Boolean = synchronized(this) { childrenMap.get().isEmpty() }
 
-    abstract override fun equals(other: Any?): Boolean
+    abstract fun similarityHashCode(): Int
 
-    abstract override fun hashCode(): Int
-
-    abstract fun structureHashCode(): Int
+    abstract fun similarityStructureHashCode(): Int
 }

core/src/main/kotlin/tw/xcc/gumtree/model/GumTree.kt

@@ -8,6 +8,9 @@ class GumTree :
     Traversable<GumTree>,
     Comparable<GumTree> {
     private val traversalHelper = TraversalHelper(this)
+    private val compareHelper = CompareHelper(this)
+
+    override val equatableProps: List<Any?> = listOf()
 
     fun insertChildAt(
         pos: Int,
@@ -33,23 +36,15 @@ class GumTree :
 
     override fun postOrdered(): List<GumTree> = traversalHelper.postOrdered()
 
-    override infix fun isIsomorphicTo(other: GumTree): Boolean {
-        TODO("Not yet implemented")
-    }
-
-    override infix fun isIsoStructuralTo(other: GumTree): Boolean {
-        TODO("Not yet implemented")
-    }
+    override infix fun isIsomorphicTo(other: GumTree): Boolean = compareHelper.isIsomorphicTo(other)
 
-    override fun equals(other: Any?): Boolean {
-        TODO("Not yet implemented")
-    }
+    override infix fun isIsoStructuralTo(other: GumTree): Boolean = compareHelper.isIsoStructuralTo(other)
 
-    override fun hashCode(): Int {
+    override fun similarityHashCode(): Int {
         TODO("Not yet implemented")
     }
 
-    override fun structureHashCode(): Int {
+    override fun similarityStructureHashCode(): Int {
         TODO("Not yet implemented")
     }