implemented xml type for new event system

src/Struct/Type.js

@@ -1,4 +1,18 @@
 import Item from './Item.js'
+import EventHandler from '../Util/EventHandler.js'
+
+// restructure children as if they were inserted one after another
+function integrateChildren (y, start) {
+  let right
+  do {
+    right = start._right
+    start._right = null
+    start._right_origin = null
+    start._origin = start._left
+    start._integrate(y)
+    start = right
+  } while (right !== null)
+}
 
 export default class Type extends Item {
   constructor () {
@@ -6,24 +20,46 @@ export default class Type extends Item {
     this._map = new Map()
     this._start = null
     this._y = null
+    this._eventHandler = new EventHandler()
+  }
+  observe (f) {
+    this._eventHandler.addEventListener(f)
+  }
+  unobserve (f) {
+    this._eventHandler.removeEventListener(f)
   }
   _integrate (y) {
+    y._transactionNewTypes.add(this)
     super._integrate(y)
     this._y = y
+    // when integrating children we must make sure to
+    // integrate start
+    const start = this._start
+    if (start !== null) {
+      this._start = null
+      integrateChildren(y, start)
+    }
+    // integrate map children
+    const map = this._map
+    for (let [key, t] of map) {
+      map.delete(key)
+      integrateChildren(y, t)
+    }
   }
-  _delete (y) {
-    super._delete(y)
+  _delete (y, createDelete) {
+    super._delete(y, createDelete)
+    y._transactionChangedTypes.delete(this)
     // delete map types
     for (let value of this._map.values()) {
       if (value instanceof Item && !value._deleted) {
-        value._delete()
+        value._delete(y, false)
       }
     }
     // delete array types
     let t = this._start
     while (t !== null) {
       if (!t._deleted) {
-        t._delete()
+        t._delete(y, false)
       }
       t = t._right
     }