feat: 🎸 implement tree similarity comparison methods

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

@@ -0,0 +1,41 @@
+package tw.xcc.gumtree.model
+
+import tw.xcc.gumtree.api.tree.Comparable
+
+class CompareHelper(private val tree: GumTree) : Comparable<GumTree> {
+    override fun isIsomorphicTo(other: GumTree): Boolean =
+        compareTrees(other, true) { child, otherChild ->
+            child isIsomorphicTo otherChild
+        }
+
+    override fun isIsoStructuralTo(other: GumTree): Boolean =
+        compareTrees(other, false) { child, otherChild ->
+            child isIsoStructuralTo otherChild
+        }
+
+    private inline fun compareTrees(
+        other: GumTree,
+        shouldCheckLabel: Boolean,
+        childComparison: (GumTree, GumTree) -> Boolean
+    ): Boolean {
+        synchronized(tree) {
+            if (!(tree hasSameTypeAs other && tree.childCount() == other.childCount())) {
+                return false
+            }
+
+            if (shouldCheckLabel && !(tree hasSameLabelAs other)) {
+                return false
+            }
+
+            for (i in 0 until tree.childCount()) {
+                val child = tree.childAt(i) ?: return false
+                val otherChild = other.childAt(i) ?: return false
+                if (!childComparison(child, otherChild)) {
+                    return false
+                }
+            }
+
+            return true
+        }
+    }
+}

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

@@ -10,7 +10,11 @@ class GumTree :
     private val traversalHelper = TraversalHelper(this)
     private val compareHelper = CompareHelper(this)
 
-
+    val type: TreeType = TreeType("")
+    var label: String = ""
+    val pos: Int = -1
+    val length: Int = -1
+
     fun insertChildAt(
         pos: Int,
         child: GumTree
@@ -31,6 +35,10 @@ class GumTree :
         }
     }
 
+    infix fun hasSameTypeAs(other: GumTree): Boolean = type == other.type
+
+    infix fun hasSameLabelAs(other: GumTree): Boolean = label == other.label
+
     override fun preOrdered(): List<GumTree> = traversalHelper.preOrdered()
 
     override fun postOrdered(): List<GumTree> = traversalHelper.postOrdered()

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

@@ -0,0 +1,5 @@
+package tw.xcc.gumtree.model
+
+data class TreeType(val name: String) {
+    fun isEmpty(): Boolean = name.isEmpty()
+}