use a linked list for filter runs. (#5206)

* Changed the filterrunprefixes to use LinkedList

* Testing for Linked List

* Finishing touches to LinkedList

* Minor corrections to link-list coding style

* Corrected for sneaky bug in linkedList

editions/test/tiddlers/tests/test-linked-list.js

@@ -0,0 +1,130 @@
+/*\
+title: test-linked-list.js
+type: application/javascript
+tags: [[$:/tags/test-spec]]
+
+Tests the utils.LinkedList class.
+
+LinkedList was built to behave exactly as $tw.utils.pushTop and
+Array.prototype.push would behave with an array.
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+describe("LinkedList class tests", function() {
+
+	it("can pushTop", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'C');
+		// singles
+		list.pushTop('X');
+		list.pushTop('B');
+		expect(list.toArray()).toEqual(['A', 'C', 'X', 'B']);
+		expect(list.length).toBe(4);
+		//arrays
+		list.pushTop(['X', 'A', 'G', 'A']);
+		// If the pushedTopped list has duplicates, they go in unempeded.
+		expect(list.toArray()).toEqual(['C', 'B', 'X', 'A', 'G', 'A']);
+		expect(list.length).toBe(6);
+	});
+
+	it("can pushTop with tricky duplicates", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'A', 'C', 'A', 'end');
+		// If the original list contains duplicates, only one instance is cut
+		list.pushTop('A');
+		expect(list.toArray()).toEqual(['B', 'A', 'C', 'A', 'end', 'A']);
+		expect(list.length).toBe(6);
+
+		// And the Llist properly knows the next 'A' to cut if pushed again
+		list.pushTop(['X', 'A']);
+		expect(list.toArray()).toEqual(['B', 'C', 'A', 'end', 'A', 'X', 'A']);
+		expect(list.length).toBe(7);
+
+		// One last time, to make sure we maintain the linked chain of copies
+		list.pushTop('A');
+		expect(list.toArray()).toEqual(['B', 'C', 'end', 'A', 'X', 'A', 'A']);
+		expect(list.length).toBe(7);
+	});
+
+	it("can handle particularly nasty pushTop pitfall", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'A', 'C');
+		list.pushTop('A'); // BACA
+		list.pushTop('X'); // BACAX
+		list.remove('A');  // BCAX
+		list.pushTop('A'); // BCXA
+		list.remove('A');  // BCX
+		// But! The way I initially coded the copy chains, a mystery A could
+		// hang around.
+		expect(list.toArray()).toEqual(['B', 'C', 'X']);
+		expect(list.length).toBe(3);
+	});
+
+	it("can push", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'C');
+		// singles
+		list.push('B');
+		expect(list.toArray()).toEqual(['A', 'B', 'C', 'B']);
+		expect(list.length).toBe(4);
+
+		// multiple args
+		list.push('A', 'B', 'C');
+		expect(list.toArray()).toEqual(['A', 'B', 'C', 'B', 'A', 'B', 'C']);
+		expect(list.length).toBe(7);
+	});
+
+	it("can clear", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'C');
+		list.clear();
+		expect(list.toArray()).toEqual([]);
+		expect(list.length).toBe(0);
+	});
+
+	it("can remove", function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'x', 'C', 'x', 'D', 'x', 'E', 'x');
+		// single
+		list.remove('x');
+		expect(list.toArray()).toEqual(['A', 'C', 'x', 'D', 'x', 'E', 'x']);
+		expect(list.length).toBe(7);
+
+		// arrays
+		list.remove(['x', 'A', 'x']);
+		expect(list.toArray()).toEqual(['C', 'D', 'E', 'x']);
+		expect(list.length).toBe(4);
+	});
+
+	it('can ignore removal of nonexistent items', function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('A', 'B', 'C', 'D');
+		// single
+		list.remove('Z');
+		expect(list.toArray()).toEqual(['A', 'B', 'C', 'D']);
+		expect(list.length).toBe(4);
+
+		// array
+		list.remove(['Z', 'B', 'X']);
+		expect(list.toArray()).toEqual(['A', 'C', 'D']);
+		expect(list.length).toBe(3);
+	});
+
+	it('can iterate with each', function() {
+		var list = new $tw.utils.LinkedList();
+		list.push('0', '1', '2', '3');
+		var counter = 0;
+		list.each(function(value) {
+			expect(value).toBe(counter.toString());
+			counter = counter + 1;
+		});
+		expect(counter).toBe(4);
+	});
+});
+
+})();