Add Get Current XPath

This commit also moves some shared code to a common class.

Issue: #85

src/common/index.ts

@@ -2,3 +2,4 @@ export * from "./configuration";
 export * from "./create-document-selector";
 export * from "./extension-state";
 export * from "./native-commands";
+export * from "./xml-traverser";

src/common/xml-traverser.ts

@@ -0,0 +1,129 @@
+import { Position } from "vscode";
+import { DOMParser } from "xmldom";
+
+export class XmlTraverser {
+
+    constructor(private _xmlDocument: Document) { }
+
+    get xmlDocument(): Document {
+        return this._xmlDocument;
+    }
+
+    set xmlDocument(value: Document) {
+        this._xmlDocument = value;
+    }
+
+    getChildAttributeArray(node: Element): any[] {
+        if (!node.attributes) {
+            return [];
+        }
+
+        const array = new Array<any>();
+
+        for (let i = 0; i < node.attributes.length; i++) {
+            array.push(node.attributes[i]);
+        }
+
+        return array;
+    }
+
+    getChildElementArray(node: Node): any[] {
+        if (!node.childNodes) {
+            return [];
+        }
+
+        const array = new Array<any>();
+
+        for (let i = 0; i < node.childNodes.length; i++) {
+            const child = node.childNodes[i];
+
+            if (this.isElement(child)) {
+                array.push(child);
+            }
+        }
+
+        return array;
+    }
+
+    getElementAtPosition(position: Position): Element {
+        const node = this.getNodeAtPosition(position);
+
+        return this.getNearestElementAncestor(node);
+    }
+
+    getNearestElementAncestor(node: Node): Element {
+        if (!this.isElement) {
+            return this.getNearestElementAncestor(node.parentNode);
+        }
+
+        return <Element>node;
+    }
+
+    getNodeAtPosition(position: Position): Node {
+        return this._getNodeAtPositionCore(position, this._xmlDocument.documentElement);
+    }
+
+    getSiblings(node: Node): Node[] {
+        return [...this.getChildAttributeArray(<Element>node.parentNode), ...this.getChildElementArray(node.parentNode)];
+    }
+
+    hasSimilarSiblings(node: Node): boolean {
+        if (!node || !node.parentNode || !this.isElement(node)) {
+            return false;
+        }
+
+        const siblings = this.getChildElementArray(<Element>node.parentNode);
+
+        return (siblings.filter(x => x.tagName === (node as Element).tagName).length > 1);
+    }
+
+    isElement(node: Node): boolean {
+        return (!!node && !!(node as Element).tagName);
+    }
+
+    private _getNodeAtPositionCore(position: Position, contextNode: Node): Node {
+        if (!contextNode) {
+            return undefined;
+        }
+
+        const lineNumber = (contextNode as any).lineNumber;
+        const columnNumber = (contextNode as any).columnNumber;
+        const columnRange = [columnNumber, (columnNumber + (this._getNodeWidthInCharacters(contextNode) - 1))];
+
+        // for some reason, xmldom sets the column number for attributes to the "="
+        if (!this.isElement(contextNode)) {
+            columnRange[0] = (columnRange[0] - contextNode.nodeName.length);
+        }
+
+        if (lineNumber === (position.line + 1) && ((position.character + 1) >= columnRange[0] && (position.character + 1) < columnRange[1])) {
+            return contextNode;
+        }
+
+        if (this.isElement(contextNode)) {
+            const children = [...this.getChildAttributeArray(<Element>contextNode), ...this.getChildElementArray(contextNode)];
+            let result: Node;
+
+            for (let i = 0; i < children.length; i++) {
+                const child = children[i];
+
+                result = this._getNodeAtPositionCore(position, child);
+
+                if (result) {
+                    return result;
+                }
+            }
+        }
+
+        return undefined;
+    }
+
+    private _getNodeWidthInCharacters(node: Node) {
+        if (this.isElement(node)) {
+            return (node.nodeName.length + 2);
+        }
+
+        else {
+            return (node.nodeName.length + node.nodeValue.length + 3);
+        }
+    }
+}