Merge pull request #1035 from ckeditor/t/1033

Feature: Introduced `model.Node#getCommonAncestor()` and `view.Node#getCommonAncestor()`. Closes #1033.

src/model/node.js

@@ -269,6 +269,26 @@ export default class Node {
 		return ancestors;
 	}
 
+	/**
+	 * Returns a {@link module:engine/model/element~Element} or {@link module:engine/model/documentfragment~DocumentFragment}
+	 * which is a common ancestor of both nodes.
+	 *
+	 * @param {module:engine/model/node~Node} node The second node.
+	 * @returns {module:engine/model/element~Element|module:engine/model/documentfragment~DocumentFragment|null}
+	 */
+	getCommonAncestor( node ) {
+		const ancestorsA = this.getAncestors();
+		const ancestorsB = node.getAncestors();
+
+		let i = 0;
+
+		while ( ancestorsA[ i ] == ancestorsB[ i ] && ancestorsA[ i ] ) {
+			i++;
+		}
+
+		return i === 0 ? null : ancestorsA[ i - 1 ];
+	}
+
 	/**
 	 * Removes this node from it's parent.
 	 */

src/view/node.js

@@ -138,6 +138,26 @@ export default class Node {
 		return ancestors;
 	}
 
+	/**
+	 * Returns a {@link module:engine/view/element~Element} or {@link module:engine/view/documentfragment~DocumentFragment}
+	 * which is a common ancestor of both nodes.
+	 *
+	 * @param {module:engine/view/node~Node} node The second node.
+	 * @returns {module:engine/view/element~Element|module:engine/view/documentfragment~DocumentFragment|null}
+	 */
+	getCommonAncestor( node ) {
+		const ancestorsA = this.getAncestors();
+		const ancestorsB = node.getAncestors();
+
+		let i = 0;
+
+		while ( ancestorsA[ i ] == ancestorsB[ i ] && ancestorsA[ i ] ) {
+			i++;
+		}
+
+		return i === 0 ? null : ancestorsA[ i - 1 ];
+	}
+
 	/**
 	 * Removes node from parent.
 	 */

tests/model/node.js

@@ -108,7 +108,7 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'getIndex', () => {
+	describe( 'getIndex()', () => {
 		it( 'should return null if the parent is null', () => {
 			expect( root.index ).to.be.null;
 		} );
@@ -134,7 +134,7 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'clone', () => {
+	describe( 'clone()', () => {
 		it( 'should return a copy of cloned node', () => {
 			const node = new Node( { foo: 'bar' } );
 			const copy = node.clone();
@@ -144,7 +144,7 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'remove', () => {
+	describe( 'remove()', () => {
 		it( 'should remove node from it\'s parent', () => {
 			const element = new Element( 'p' );
 			element.appendChildren( node );
@@ -204,7 +204,7 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'getPath', () => {
+	describe( 'getPath()', () => {
 		it( 'should return proper path', () => {
 			expect( root.getPath() ).to.deep.equal( [] );
 
@@ -218,7 +218,7 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'getAncestors', () => {
+	describe( 'getAncestors()', () => {
 		it( 'should return proper array of ancestor nodes', () => {
 			expect( root.getAncestors() ).to.deep.equal( [] );
 			expect( two.getAncestors() ).to.deep.equal( [ root ] );
@@ -242,6 +242,57 @@ describe( 'Node', () => {
 		} );
 	} );
 
+	describe( 'getCommonAncestor()', () => {
+		it( 'should return the parent element for the same node', () => {
+			expect( img.getCommonAncestor( img ) ).to.equal( two );
+		} );
+
+		it( 'should return null for detached subtrees', () => {
+			const detached = new Element( 'foo' );
+
+			expect( img.getCommonAncestor( detached ) ).to.be.null;
+			expect( detached.getCommonAncestor( img ) ).to.be.null;
+		} );
+
+		it( 'should return null when one of the nodes is a tree root itself', () => {
+			expect( root.getCommonAncestor( img ) ).to.be.null;
+			expect( img.getCommonAncestor( root ) ).to.be.null;
+			expect( root.getCommonAncestor( root ) ).to.be.null;
+		} );
+
+		it( 'should return parent of the nodes at the same level', () => {
+			expect( img.getCommonAncestor( textBA ) ).to.equal( two );
+			expect( textR.getCommonAncestor( textBA ) ).to.equal( two );
+		} );
+
+		it( 'should return proper element for nodes in different branches and on different levels', () => {
+			const foo = new Text( 'foo' );
+			const bar = new Text( 'bar' );
+			const bom = new Text( 'bom' );
+			const d = new Element( 'd', null, [ bar ] );
+			const c = new Element( 'c', null, [ foo, d ] );
+			const b = new Element( 'b', null, [ c ] );
+			const e = new Element( 'e', null, [ bom ] );
+			const a = new Element( 'a', null, [ b, e ] );
+
+			// <a><b><c>foo<d>bar</d></c></b><e>bom</e></a>
+
+			expect( bar.getCommonAncestor( foo ), 1 ).to.equal( c );
+			expect( foo.getCommonAncestor( d ), 2 ).to.equal( c );
+			expect( c.getCommonAncestor( b ), 3 ).to.equal( a );
+			expect( bom.getCommonAncestor( d ), 4 ).to.equal( a );
+			expect( b.getCommonAncestor( bom ), 5 ).to.equal( a );
+		} );
+
+		it( 'should return document fragment', () => {
+			const foo = new Text( 'foo' );
+			const bar = new Text( 'bar' );
+			const df = new DocumentFragment( [ foo, bar ] );
+
+			expect( foo.getCommonAncestor( bar ) ).to.equal( df );
+		} );
+	} );
+
 	describe( 'attributes interface', () => {
 		const node = new Node( { foo: 'bar' } );
 

tests/view/node.js

@@ -29,7 +29,7 @@ describe( 'Node', () => {
 		root = new Element( null, null, [ one, two, three ] );
 	} );
 
-	describe( 'getNextSibling/getPreviousSibling', () => {
+	describe( 'getNextSibling/getPreviousSibling()', () => {
 		it( 'should return next sibling', () => {
 			expect( root.nextSibling ).to.be.null;
 
@@ -57,7 +57,7 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'getAncestors', () => {
+	describe( 'getAncestors()', () => {
 		it( 'should return empty array for node without ancestors', () => {
 			const result = root.getAncestors();
 			expect( result ).to.be.an( 'array' );
@@ -109,7 +109,58 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'getIndex', () => {
+	describe( 'getCommonAncestor()', () => {
+		it( 'should return the parent element for the same node', () => {
+			expect( img.getCommonAncestor( img ) ).to.equal( two );
+		} );
+
+		it( 'should return null for detached subtrees', () => {
+			const detached = new Element( 'foo' );
+
+			expect( img.getCommonAncestor( detached ) ).to.be.null;
+			expect( detached.getCommonAncestor( img ) ).to.be.null;
+		} );
+
+		it( 'should return null when one of the nodes is a tree root itself', () => {
+			expect( root.getCommonAncestor( img ) ).to.be.null;
+			expect( img.getCommonAncestor( root ) ).to.be.null;
+			expect( root.getCommonAncestor( root ) ).to.be.null;
+		} );
+
+		it( 'should return parent of the nodes at the same level', () => {
+			expect( img.getCommonAncestor( charA ) ).to.equal( two );
+			expect( charB.getCommonAncestor( charA ) ).to.equal( two );
+		} );
+
+		it( 'should return proper element for nodes in different branches and on different levels', () => {
+			const foo = new Text( 'foo' );
+			const bar = new Text( 'bar' );
+			const bom = new Text( 'bom' );
+			const d = new Element( 'd', null, [ bar ] );
+			const c = new Element( 'c', null, [ foo, d ] );
+			const b = new Element( 'b', null, [ c ] );
+			const e = new Element( 'e', null, [ bom ] );
+			const a = new Element( 'a', null, [ b, e ] );
+
+			// <a><b><c>foo<d>bar</d></c></b><e>bom</e></a>
+
+			expect( bar.getCommonAncestor( foo ), 1 ).to.equal( c );
+			expect( foo.getCommonAncestor( d ), 2 ).to.equal( c );
+			expect( c.getCommonAncestor( b ), 3 ).to.equal( a );
+			expect( bom.getCommonAncestor( d ), 4 ).to.equal( a );
+			expect( b.getCommonAncestor( bom ), 5 ).to.equal( a );
+		} );
+
+		it( 'should return document fragment', () => {
+			const foo = new Text( 'foo' );
+			const bar = new Text( 'bar' );
+			const df = new DocumentFragment( [ foo, bar ] );
+
+			expect( foo.getCommonAncestor( bar ) ).to.equal( df );
+		} );
+	} );
+
+	describe( 'getIndex()', () => {
 		it( 'should return null if the parent is null', () => {
 			expect( root.index ).to.be.null;
 		} );
@@ -139,7 +190,7 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'getDocument', () => {
+	describe( 'getDocument()', () => {
 		it( 'should return null if any parent has not set Document', () => {
 			expect( charA.document ).to.be.null;
 		} );
@@ -164,7 +215,7 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'getRoot', () => {
+	describe( 'getRoot()', () => {
 		it( 'should return this element if it has no parent', () => {
 			const child = new Element( 'p' );
 
@@ -183,7 +234,7 @@ describe( 'Node', () => {
 		} );
 	} );
 
-	describe( 'remove', () => {
+	describe( 'remove()', () => {
 		it( 'should remove node from its parent', () => {
 			const char = new Text( 'a' );
 			const parent = new Element( 'p', null, [ char ] );
@@ -246,7 +297,7 @@ describe( 'Node', () => {
 			sinon.assert.calledWith( rootChangeSpy, 'attributes', img );
 		} );
 
-		describe( 'setAttribute', () => {
+		describe( 'setAttribute()', () => {
 			it( 'should fire change event', () => {
 				img.setAttribute( 'width', 100 );
 
@@ -255,7 +306,7 @@ describe( 'Node', () => {
 			} );
 		} );
 
-		describe( 'removeAttribute', () => {
+		describe( 'removeAttribute()', () => {
 			it( 'should fire change event', () => {
 				img.removeAttribute( 'src' );
 
@@ -264,7 +315,7 @@ describe( 'Node', () => {
 			} );
 		} );
 
-		describe( 'insertChildren', () => {
+		describe( 'insertChildren()', () => {
 			it( 'should fire change event', () => {
 				root.insertChildren( 1, new Element( 'img' ) );
 
@@ -273,7 +324,7 @@ describe( 'Node', () => {
 			} );
 		} );
 
-		describe( 'appendChildren', () => {
+		describe( 'appendChildren()', () => {
 			it( 'should fire change event', () => {
 				root.appendChildren( new Element( 'img' ) );
 
@@ -282,7 +333,7 @@ describe( 'Node', () => {
 			} );
 		} );
 
-		describe( 'removeChildren', () => {
+		describe( 'removeChildren()', () => {
 			it( 'should fire change event', () => {
 				root.removeChildren( 1, 1 );
 
@@ -291,7 +342,7 @@ describe( 'Node', () => {
 			} );
 		} );
 
-		describe( 'removeChildren', () => {
+		describe( 'removeChildren()', () => {
 			it( 'should fire change event', () => {
 				text.data = 'bar';