Add Node.compareDocumentPosition implementation (#16)

Author: kuzmadom

src/entries/dom-api.js

@@ -1,8 +1,93 @@
 import {document as lightJsDocument} from '@litejs/dom';
 import {CSSStyleDeclaration} from '@litejs/dom/css';
+import {Node} from '@litejs/dom/dom';
 
 CSSStyleDeclaration.prototype.setProperty = function(key, value) {
 	this[key] = value;
 };
 
+Node.DOCUMENT_POSITION_DISCONNECTED = 1;
+Node.DOCUMENT_POSITION_PRECEDING = 2;
+Node.DOCUMENT_POSITION_FOLLOWING = 4;
+Node.DOCUMENT_POSITION_CONTAINS = 8;
+Node.DOCUMENT_POSITION_CONTAINED_BY = 16;
+Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC = 32;
+
+Node.compareDocumentPosition = compareDocumentPosition;
+
+function recursivelyWalk(nodes, cb) {
+    for (let i = 0, len = nodes.length; i < len; i++) {
+        const node = nodes[i];
+
+        if (cb(node)) {
+            return cb(node);
+        }
+        
+		if (node.childNodes?.length) {
+            const ret = recursivelyWalk(node.childNodes, cb);
+            if (ret) {
+                return ret;
+            }
+        }
+    }
+}
+
+function compareDocumentPosition(other) {
+    if (this === other) {
+        return 0;
+    }
+
+	let reference = this,
+	referenceTop = this,
+	otherTop = other;
+
+    while (referenceTop.parentNode) {
+        referenceTop = referenceTop.parentNode;
+    }
+    while (otherTop.parentNode) {
+        otherTop = otherTop.parentNode;
+    }
+
+    if (referenceTop !== otherTop) {
+        return Node.DOCUMENT_POSITION_DISCONNECTED;
+    }
+
+    let children = reference.childNodes;
+    let ret = recursivelyWalk(
+        children,
+		(node) => node === other,
+    );
+    if (ret) {
+        return Node.DOCUMENT_POSITION_CONTAINED_BY;
+    }
+
+    children = other.childNodes;
+    ret = recursivelyWalk(
+        children, 
+		(node) => node === reference,
+    );
+    if (ret) {
+        return Node.DOCUMENT_POSITION_CONTAINS;
+    }
+
+    ret = recursivelyWalk(
+        [referenceTop],
+        (node) => {
+			if (node === other) {
+				return 'other';
+			} 
+			
+			if (node === reference) {
+				return 'reference';
+			}
+		}
+    );
+
+    if (ret === 'other') {
+        return Node.DOCUMENT_POSITION_PRECEDING;
+    } 
+
+    return Node.DOCUMENT_POSITION_FOLLOWING;
+}
+
 export const document = lightJsDocument;