From 75a13a0aa4acab0471e92ca95a1904a9ed4efd9e Mon Sep 17 00:00:00 2001
From: Arman Ozak <arman@armanozak.com>
Date: Wed, 25 Mar 2020 17:54:11 +0300
Subject: [PATCH] feat(core): add doubly linked list as shared utility

---
 .../core/src/lib/tests/linked-list.spec.ts    | 720 ++++++++++++++++++
 .../packages/core/src/lib/utils/index.ts      |   1 +
 .../core/src/lib/utils/linked-list.ts         | 240 ++++++
 3 files changed, 961 insertions(+)
 create mode 100644 npm/ng-packs/packages/core/src/lib/tests/linked-list.spec.ts
 create mode 100644 npm/ng-packs/packages/core/src/lib/utils/linked-list.ts

diff --git a/npm/ng-packs/packages/core/src/lib/tests/linked-list.spec.ts b/npm/ng-packs/packages/core/src/lib/tests/linked-list.spec.ts
new file mode 100644
index 0000000000..cd0a00096e
--- /dev/null
+++ b/npm/ng-packs/packages/core/src/lib/tests/linked-list.spec.ts
@@ -0,0 +1,720 @@
+import { LinkedList } from '../utils/linked-list';
+
+describe('Linked List (Doubly)', () => {
+  let list: LinkedList;
+
+  beforeEach(() => (list = new LinkedList()));
+
+  describe('#length', () => {
+    it('should initially be 0', () => {
+      expect(list.length).toBe(0);
+    });
+  });
+
+  describe('#head', () => {
+    it('should initially be undefined', () => {
+      expect(list.head).toBeUndefined();
+    });
+  });
+
+  describe('#tail', () => {
+    it('should initially be undefined', () => {
+      expect(list.tail).toBeUndefined();
+    });
+  });
+
+  describe('#add', () => {
+    describe('#head', () => {
+      it('should add node to the head of the list', () => {
+        list.addHead('a');
+
+        // "a"
+
+        expect(list.head.value).toBe('a');
+        expect(list.tail.value).toBe('a');
+      });
+
+      it('should create reference to previous and next nodes', () => {
+        list.add('a').head();
+        list.add('b').head();
+        list.add('c').head();
+
+        // "c" <-> "b" <-> "a"
+
+        expect(list.length).toBe(3);
+        expect(list.head.value).toBe('c');
+        expect(list.head.next.value).toBe('b');
+        expect(list.head.previous).toBeUndefined();
+        expect(list.tail.value).toBe('a');
+        expect(list.tail.previous.value).toBe('b');
+        expect(list.tail.next).toBeUndefined();
+      });
+    });
+
+    describe('#tail', () => {
+      it('should add node to the tail of the list', () => {
+        list.addTail('a');
+
+        // "a"
+
+        expect(list.head.value).toBe('a');
+        expect(list.tail.value).toBe('a');
+        expect(list.tail.next).toBeUndefined();
+      });
+
+      it('should create reference to previous and next nodes', () => {
+        list.add('a').tail();
+        list.add('b').tail();
+        list.add('c').tail();
+
+        // "a" <-> "b" <-> "c"
+
+        expect(list.length).toBe(3);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('b');
+        expect(list.head.previous).toBeUndefined();
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('b');
+        expect(list.tail.next).toBeUndefined();
+      });
+    });
+
+    describe('#after', () => {
+      it('should place a node after node with given value', () => {
+        list.add('a').tail();
+        list.add('b').tail();
+        list.add('c').tail();
+
+        // "a" <-> "b" <-> "c"
+
+        list.add('x').after('b');
+
+        // "a" <-> "b" <-> "x" <-> "c"
+
+        expect(list.length).toBe(4);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('b');
+        expect(list.head.next.next.value).toBe('x');
+        expect(list.head.next.next.next.value).toBe('c');
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('x');
+        expect(list.tail.previous.previous.value).toBe('b');
+        expect(list.tail.previous.previous.previous.value).toBe('a');
+      });
+
+      it('should be able to receive a custom compareFn', () => {
+        list.add({ x: 1 }).tail();
+        list.add({ x: 2 }).tail();
+        list.add({ x: 3 }).tail();
+
+        // {"x":1} <-> {"x":2} <-> {"x":3}
+
+        list.add({ x: 0 }).after({ x: 1 }, (v1: X, v2: X) => v1.x === v2.x);
+
+        // {"x":1} <-> {"x":0} <-> {"x":2} <-> {"x":3}
+
+        expect(list.length).toBe(4);
+        expect(list.head.value.x).toBe(1);
+        expect(list.head.next.value.x).toBe(0);
+        expect(list.head.next.next.value.x).toBe(2);
+        expect(list.head.next.next.next.value.x).toBe(3);
+        expect(list.tail.value.x).toBe(3);
+        expect(list.tail.previous.value.x).toBe(2);
+        expect(list.tail.previous.previous.value.x).toBe(0);
+        expect(list.tail.previous.previous.previous.value.x).toBe(1);
+      });
+    });
+
+    describe('#before', () => {
+      it('should place a node before node with given value', () => {
+        list.add('a').tail();
+        list.add('b').tail();
+        list.add('c').tail();
+
+        // "a" <-> "b" <-> "c"
+
+        list.add('x').before('b');
+
+        // "a" <-> "x" <-> "b" <-> "c"
+
+        expect(list.length).toBe(4);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('x');
+        expect(list.head.next.next.value).toBe('b');
+        expect(list.head.next.next.next.value).toBe('c');
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('b');
+        expect(list.tail.previous.previous.value).toBe('x');
+        expect(list.tail.previous.previous.previous.value).toBe('a');
+      });
+
+      it('should be able to receive a custom compareFn', () => {
+        list.add({ x: 1 }).tail();
+        list.add({ x: 2 }).tail();
+        list.add({ x: 3 }).tail();
+
+        // {"x":1} <-> {"x":2} <-> {"x":3}
+
+        list.add({ x: 0 }).before({ x: 2 }, (v1: X, v2: X) => v1.x === v2.x);
+
+        // {"x":1} <-> {"x":0} <-> {"x":2} <-> {"x":3}
+
+        expect(list.length).toBe(4);
+        expect(list.head.value.x).toBe(1);
+        expect(list.head.next.value.x).toBe(0);
+        expect(list.head.next.next.value.x).toBe(2);
+        expect(list.head.next.next.next.value.x).toBe(3);
+        expect(list.tail.value.x).toBe(3);
+        expect(list.tail.previous.value.x).toBe(2);
+        expect(list.tail.previous.previous.value.x).toBe(0);
+        expect(list.tail.previous.previous.previous.value.x).toBe(1);
+      });
+    });
+
+    describe('#byIndex', () => {
+      it('should place a node at given index', () => {
+        list.add('a').tail();
+        list.add('b').tail();
+        list.add('c').tail();
+
+        // "a" <-> "b" <-> "c"
+
+        list.add('x').byIndex(1);
+
+        // "a" <-> "x" <-> "b" <-> "c"
+
+        list.add('y').byIndex(3);
+
+        // "a" <-> "x" <-> "b" <-> "y" <-> "c"
+
+        expect(list.length).toBe(5);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('x');
+        expect(list.head.next.next.value).toBe('b');
+        expect(list.head.next.next.next.value).toBe('y');
+        expect(list.head.next.next.next.next.value).toBe('c');
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('y');
+        expect(list.tail.previous.previous.value).toBe('b');
+        expect(list.tail.previous.previous.previous.value).toBe('x');
+        expect(list.tail.previous.previous.previous.previous.value).toBe('a');
+      });
+    });
+  });
+
+  describe('#find', () => {
+    it('should return the first node found based on given predicate', () => {
+      list.add('a').tail();
+      list.add('x').tail();
+      list.add('b').tail();
+      list.add('x').tail();
+      list.add('c').tail();
+
+      // "a" <-> "x" <-> "b" <-> "x" <-> "c"
+
+      const node1 = list.find(value => value === 'x');
+
+      expect(node1.value).toBe('x');
+      expect(node1.previous.value).toBe('a');
+      expect(node1.next.value).toBe('b');
+
+      // "a" <-> "x" <-> "b" <-> "x" <-> "c"
+
+      const node2 = list.find((_, index) => index === 3);
+
+      expect(node2.value).toBe('x');
+      expect(node2.previous.value).toBe('b');
+      expect(node2.next.value).toBe('c');
+    });
+
+    it('should return undefined when list is empty', () => {
+      const node = list.find(value => value === 'x');
+
+      expect(node).toBeUndefined();
+    });
+
+    it('should return undefined when predicate finds no match', () => {
+      list.add('a').tail();
+      list.add('b').tail();
+      list.add('c').tail();
+
+      // "a" <-> "b" <-> "c"
+
+      const node = list.find(value => value === 'x');
+
+      expect(node).toBeUndefined();
+      expect(list.length).toBe(3);
+      expect(list.head.value).toBe('a');
+      expect(list.head.next.value).toBe('b');
+      expect(list.head.next.next.value).toBe('c');
+      expect(list.tail.value).toBe('c');
+      expect(list.tail.previous.value).toBe('b');
+      expect(list.tail.previous.previous.value).toBe('a');
+    });
+  });
+
+  describe('#findIndex', () => {
+    it('should return the index of the first node found based on given predicate', () => {
+      list.add('a').tail();
+      list.add('x').tail();
+      list.add('b').tail();
+      list.add('x').tail();
+      list.add('c').tail();
+
+      // "a" <-> "x" <-> "b" <-> "x" <-> "c"
+
+      const index1 = list.findIndex(value => value === 'x');
+
+      expect(index1).toBe(1);
+
+      // "a" <-> "x" <-> "b" <-> "x" <-> "c"
+
+      let timesFound = 0;
+      const index2 = list.findIndex(value => {
+        if (timesFound > 1) return false;
+
+        timesFound += Number(value === 'x');
+
+        return timesFound > 1;
+      });
+
+      expect(index2).toBe(3);
+    });
+
+    it('should return -1 when list is empty', () => {
+      const index = list.findIndex(value => value === 'x');
+
+      expect(index).toBe(-1);
+    });
+
+    it('should return -1 when no match is found', () => {
+      list.add('a').tail();
+      list.add('b').tail();
+      list.add('c').tail();
+
+      // "a" <-> "b" <-> "c"
+
+      const index = list.findIndex(value => value === 'x');
+
+      expect(index).toBe(-1);
+      expect(list.length).toBe(3);
+      expect(list.head.value).toBe('a');
+      expect(list.head.next.value).toBe('b');
+      expect(list.head.next.next.value).toBe('c');
+      expect(list.tail.value).toBe('c');
+      expect(list.tail.previous.value).toBe('b');
+      expect(list.tail.previous.previous.value).toBe('a');
+    });
+  });
+
+  describe('#forEach', () => {
+    it('should call given function for each node of the list', () => {
+      list.add('a').tail();
+      list.add('b').tail();
+      list.add('c').tail();
+
+      // "a" <-> "b" <-> "c"
+
+      const spy = jest.fn();
+      list.forEach(spy);
+
+      expect(spy.mock.calls).toEqual([
+        ['a', 0, list],
+        ['b', 1, list],
+        ['c', 2, list],
+      ]);
+    });
+
+    it('should not call given function when list is empty', () => {
+      const spy = jest.fn();
+      list.forEach(spy);
+
+      expect(spy).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('#drop', () => {
+    describe('#head', () => {
+      it('should return undefined when there is no head', () => {
+        expect(list.drop().head()).toBeUndefined();
+      });
+
+      it('should remove the node from the head of the list', () => {
+        list.add('a').tail();
+        list.add('b').tail();
+        list.add('c').tail();
+
+        // "a" <-> "b" <-> "c"
+
+        list.drop().head();
+
+        // "b" <-> "c"
+
+        expect(list.length).toBe(2);
+        expect(list.head.value).toBe('b');
+        expect(list.head.next.value).toBe('c');
+        expect(list.head.previous).toBeUndefined();
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('b');
+        expect(list.tail.next).toBeUndefined();
+      });
+    });
+
+    describe('#head', () => {
+      it('should return undefined when there is no tail', () => {
+        expect(list.drop().tail()).toBeUndefined();
+      });
+
+      it('should remove the node from the tail of the list', () => {
+        list.add('a').tail();
+        list.add('b').tail();
+        list.add('c').tail();
+
+        // "a" <-> "b" <-> "c"
+
+        list.drop().tail();
+
+        // "a" <-> "b"
+
+        expect(list.length).toBe(2);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('b');
+        expect(list.head.previous).toBeUndefined();
+        expect(list.tail.value).toBe('b');
+        expect(list.tail.previous.value).toBe('a');
+        expect(list.tail.next).toBeUndefined();
+      });
+    });
+
+    describe('#byIndex', () => {
+      it('should remove the node at given index', () => {
+        list.add('a').tail();
+        list.add('b').tail();
+        list.add('c').tail();
+        list.add('d').tail();
+        list.add('e').tail();
+
+        // "a" <-> "b" <-> "c" <-> "d" <-> "e"
+
+        list.drop().byIndex(1);
+
+        // "a" <-> "c" <-> "d" <-> "e"
+
+        list.drop().byIndex(2);
+
+        // "a" <-> "c" <-> "e"
+
+        expect(list.length).toBe(3);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('c');
+        expect(list.head.next.next.value).toBe('e');
+        expect(list.tail.value).toBe('e');
+        expect(list.tail.previous.value).toBe('c');
+        expect(list.tail.previous.previous.value).toBe('a');
+      });
+
+      it('should return undefined when list is empty', () => {
+        const node = list.drop().byIndex(0);
+        expect(node).toBeUndefined();
+      });
+
+      it('should return undefined when given index does not exist', () => {
+        list.add('a').tail();
+        list.add('b').tail();
+        list.add('c').tail();
+
+        // "a" <-> "b" <-> "c"
+
+        const node1 = list.drop().byIndex(4);
+
+        // "a" <-> "b" <-> "c"
+
+        expect(node1).toBeUndefined();
+        expect(list.length).toBe(3);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('b');
+        expect(list.head.next.next.value).toBe('c');
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('b');
+        expect(list.tail.previous.previous.value).toBe('a');
+
+        // "a" <-> "b" <-> "c"
+
+        const node2 = list.drop().byIndex(-1);
+
+        // "a" <-> "b" <-> "c"
+
+        expect(node2).toBeUndefined();
+        expect(list.length).toBe(3);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('b');
+        expect(list.head.next.next.value).toBe('c');
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('b');
+        expect(list.tail.previous.previous.value).toBe('a');
+      });
+    });
+
+    describe('#byValue', () => {
+      it('should remove the first node with given value', () => {
+        list.add('a').tail();
+        list.add('x').tail();
+        list.add('b').tail();
+        list.add('x').tail();
+        list.add('c').tail();
+
+        // "a" <-> "x" <-> "b" <-> "x" <-> "c"
+
+        list.drop().byValue('x');
+
+        // "a" <-> "b" <-> "x" <-> "c"
+
+        expect(list.length).toBe(4);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('b');
+        expect(list.head.next.next.value).toBe('x');
+        expect(list.head.next.next.next.value).toBe('c');
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('x');
+        expect(list.tail.previous.previous.value).toBe('b');
+        expect(list.tail.previous.previous.previous.value).toBe('a');
+
+        // "a" <-> "b" <-> "x" <-> "c"
+
+        list.drop().byValue('x');
+
+        // "a" <-> "b" <-> "c"
+
+        expect(list.length).toBe(3);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('b');
+        expect(list.head.next.next.value).toBe('c');
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('b');
+        expect(list.tail.previous.previous.value).toBe('a');
+      });
+
+      it('should be able to receive a custom compareFn', () => {
+        list.add({ x: 1 }).tail();
+        list.add({ x: 2 }).tail();
+        list.add({ x: 3 }).tail();
+
+        // {"x":1} <-> {"x":2} <-> {"x":3}
+
+        list.drop().byValue({ x: 2 }, (v1: X, v2: X) => v1.x === v2.x);
+
+        // {"x":1} <-> {"x":3}
+
+        expect(list.length).toBe(2);
+        expect(list.head.value.x).toBe(1);
+        expect(list.head.next.value.x).toBe(3);
+        expect(list.tail.value.x).toBe(3);
+        expect(list.tail.previous.value.x).toBe(1);
+      });
+
+      it('should return undefined when list is empty', () => {
+        const node = list.drop().byValue('x');
+        expect(node).toBeUndefined();
+      });
+
+      it('should return undefined when given value is not found', () => {
+        list.add('a').tail();
+        list.add('b').tail();
+        list.add('c').tail();
+
+        // "a" <-> "b" <-> "c"
+
+        const node = list.drop().byValue('x');
+
+        // "a" <-> "b" <-> "c"
+
+        expect(node).toBeUndefined();
+        expect(list.length).toBe(3);
+        expect(list.head.value).toBe('a');
+        expect(list.head.next.value).toBe('b');
+        expect(list.head.next.next.value).toBe('c');
+        expect(list.tail.value).toBe('c');
+        expect(list.tail.previous.value).toBe('b');
+        expect(list.tail.previous.previous.value).toBe('a');
+      });
+    });
+  });
+
+  describe('#get', () => {
+    it('should return node at given index', () => {
+      list.add('a').tail();
+      list.add('b').tail();
+      list.add('c').tail();
+
+      // "a" <-> "b" <-> "c"
+
+      const node = list.get(1);
+
+      expect(node.value).toBe('b');
+      expect(node.previous.value).toBe('a');
+      expect(node.next.value).toBe('c');
+    });
+
+    it('should return undefined when list is empty', () => {
+      const node = list.get(1);
+
+      expect(node).toBeUndefined();
+    });
+
+    it('should return undefined when predicate finds no match', () => {
+      list.add('a').tail();
+      list.add('b').tail();
+      list.add('c').tail();
+
+      // "a" <-> "b" <-> "c"
+
+      const node1 = list.get(4);
+
+      expect(node1).toBeUndefined();
+      expect(list.length).toBe(3);
+      expect(list.head.value).toBe('a');
+      expect(list.head.next.value).toBe('b');
+      expect(list.head.next.next.value).toBe('c');
+      expect(list.tail.value).toBe('c');
+      expect(list.tail.previous.value).toBe('b');
+      expect(list.tail.previous.previous.value).toBe('a');
+
+      // "a" <-> "b" <-> "c"
+
+      const node2 = list.get(-1);
+
+      expect(node2).toBeUndefined();
+      expect(list.length).toBe(3);
+      expect(list.head.value).toBe('a');
+      expect(list.head.next.value).toBe('b');
+      expect(list.head.next.next.value).toBe('c');
+      expect(list.tail.value).toBe('c');
+      expect(list.tail.previous.value).toBe('b');
+      expect(list.tail.previous.previous.value).toBe('a');
+    });
+  });
+
+  describe('#indexOf', () => {
+    it('should return the index of the first node found based on given value', () => {
+      list.add('a').tail();
+      list.add('x').tail();
+      list.add('b').tail();
+      list.add('x').tail();
+      list.add('c').tail();
+
+      // "a" <-> "x" <-> "b" <-> "x" <-> "c"
+
+      const index1 = list.indexOf('x');
+
+      expect(index1).toBe(1);
+
+      // "a" <-> "x" <-> "b" <-> "x" <-> "c"
+
+      let timesFound = 0;
+      const index2 = list.indexOf('x', (v1: string, v2: string) => {
+        if (timesFound > 1) return false;
+
+        timesFound += Number(v1 === v2);
+
+        return timesFound > 1;
+      });
+
+      expect(index2).toBe(3);
+    });
+
+    it('should be able to receive a custom compareFn', () => {
+      list.add({ x: 1 }).tail();
+      list.add({ x: 2 }).tail();
+      list.add({ x: 3 }).tail();
+
+      // {"x":1} <-> {"x":2} <-> {"x":3}
+
+      const index = list.indexOf({ x: 2 }, (v1: X, v2: X) => v1.x === v2.x);
+
+      expect(index).toBe(1);
+    });
+
+    it('should return -1 when list is empty', () => {
+      const index = list.indexOf('x');
+
+      expect(index).toBe(-1);
+    });
+
+    it('should return -1 when no match is found', () => {
+      list.add('a').tail();
+      list.add('b').tail();
+      list.add('c').tail();
+
+      // "a" <-> "b" <-> "c"
+
+      const index = list.indexOf('x');
+
+      expect(index).toBe(-1);
+      expect(list.length).toBe(3);
+      expect(list.head.value).toBe('a');
+      expect(list.head.next.value).toBe('b');
+      expect(list.head.next.next.value).toBe('c');
+      expect(list.tail.value).toBe('c');
+      expect(list.tail.previous.value).toBe('b');
+      expect(list.tail.previous.previous.value).toBe('a');
+    });
+  });
+
+  describe('#toArray', () => {
+    it('should return array representation', () => {
+      list.addTail('a');
+      list.addTail(2);
+      list.addTail('c');
+      list.addTail({ k: 4, v: 'd' });
+
+      // "a" <-> 2 <-> "c" <-> {"k":4,"v":"d"}
+
+      const arr = list.toArray();
+      expect(arr).toEqual(['a', 2, 'c', { k: 4, v: 'd' }]);
+    });
+
+    it('should return empty array when list is empty', () => {
+      const arr = list.toArray();
+      expect(arr).toEqual([]);
+    });
+  });
+
+  describe('#toString', () => {
+    it('should return string representation', () => {
+      list.addTail('a');
+      list.addTail(2);
+      list.addTail('c');
+      list.addTail({ k: 4, v: 'd' });
+
+      // "a" <-> 2 <-> "c" <-> {"k":4,"v":"d"}
+
+      const str = list.toString();
+      expect(str).toBe('"a" <-> 2 <-> "c" <-> {"k":4,"v":"d"}');
+    });
+
+    it('should return empty string when list is empty', () => {
+      const str = list.toString();
+      expect(str).toBe('');
+    });
+  });
+
+  it('should be iterable', () => {
+    list.addTail('a');
+    list.addTail('b');
+    list.addTail('c');
+
+    // "a" <-> "b" <-> "c"
+
+    const arr = [];
+
+    for (let value of list) {
+      arr.push(value);
+    }
+
+    expect(arr).toEqual(['a', 'b', 'c']);
+  });
+});
+
+interface X {
+  [k: string]: any;
+}
diff --git a/npm/ng-packs/packages/core/src/lib/utils/index.ts b/npm/ng-packs/packages/core/src/lib/utils/index.ts
index 0043152ada..a112d9acd8 100644
--- a/npm/ng-packs/packages/core/src/lib/utils/index.ts
+++ b/npm/ng-packs/packages/core/src/lib/utils/index.ts
@@ -1,5 +1,6 @@
 export * from './common-utils';
 export * from './generator-utils';
 export * from './initial-utils';
+export * from './linked-list';
 export * from './route-utils';
 export * from './rxjs-utils';
diff --git a/npm/ng-packs/packages/core/src/lib/utils/linked-list.ts b/npm/ng-packs/packages/core/src/lib/utils/linked-list.ts
new file mode 100644
index 0000000000..f5a027e882
--- /dev/null
+++ b/npm/ng-packs/packages/core/src/lib/utils/linked-list.ts
@@ -0,0 +1,240 @@
+import compare from 'just-compare';
+
+export class ListNode<T = any> {
+  readonly value: T;
+  next: ListNode | undefined;
+  previous: ListNode | undefined;
+
+  constructor(value: T) {
+    this.value = value;
+  }
+}
+
+export class LinkedList<T = any> {
+  private first: ListNode<T> | undefined;
+  private last: ListNode<T> | undefined;
+  private size = 0;
+
+  get head(): ListNode<T> | undefined {
+    return this.first;
+  }
+  get tail(): ListNode<T> | undefined {
+    return this.last;
+  }
+  get length(): number {
+    return this.size;
+  }
+
+  private linkWith(value: T, previousNode: ListNode<T>, nextNode: ListNode<T>): ListNode<T> {
+    const node = new ListNode(value);
+
+    if (!previousNode) return this.addHead(value);
+    if (!nextNode) return this.addTail(value);
+
+    node.previous = previousNode;
+    previousNode.next = node;
+    node.next = nextNode;
+    nextNode.previous = node;
+
+    this.size += 1;
+
+    return node;
+  }
+
+  add(value: T) {
+    return {
+      after: (previousValue: T, compareFn = compare) => {
+        return this.addAfter(value, previousValue, compareFn);
+      },
+      before: (nextValue: T, compareFn = compare) => {
+        return this.addBefore(value, nextValue, compareFn);
+      },
+      byIndex: (position: number): ListNode<T> => {
+        return this.addByIndex(value, position);
+      },
+      head: (): ListNode<T> => {
+        return this.addHead(value);
+      },
+      tail: (): ListNode<T> => {
+        return this.addTail(value);
+      },
+    };
+  }
+
+  addAfter(value: T, previousValue: T, compareFn = compare): ListNode<T> {
+    const previous = this.find(currentValue => compareFn(currentValue, previousValue));
+
+    return previous ? this.linkWith(value, previous, previous.next) : this.addTail(value);
+  }
+
+  addBefore(value: T, nextValue: T, compareFn = compare): ListNode<T> {
+    const next = this.find(currentValue => compareFn(currentValue, nextValue));
+
+    return next ? this.linkWith(value, next.previous, next) : this.addHead(value);
+  }
+
+  addByIndex(value: T, position: number): ListNode<T> {
+    if (position <= 0) return this.addHead(value);
+    if (position >= this.size) return this.addTail(value);
+
+    const next = this.get(position)!;
+
+    return this.linkWith(value, next.previous, next);
+  }
+
+  addHead(value: T): ListNode<T> {
+    const node = new ListNode(value);
+
+    node.next = this.first;
+
+    if (this.first) this.first.previous = node;
+    else this.last = node;
+
+    this.first = node;
+    this.size += 1;
+
+    return node;
+  }
+
+  addTail(value: T): ListNode<T> {
+    const node = new ListNode(value);
+
+    if (this.first) {
+      node.previous = this.last;
+      this.last!.next = node;
+      this.last = node;
+    } else {
+      this.first = node;
+      this.last = node;
+    }
+
+    this.size += 1;
+
+    return node;
+  }
+
+  drop() {
+    return {
+      byIndex: (position: number) => this.dropByIndex(position),
+      byValue: (value: T, compareFn = compare) => this.dropByValue(value, compareFn),
+      head: () => this.dropHead(),
+      tail: () => this.dropTail(),
+    };
+  }
+
+  dropByIndex(position: number): ListNode<T> | undefined {
+    if (position === 0) return this.dropHead();
+    else if (position === this.size - 1) return this.dropTail();
+
+    const current = this.get(position);
+
+    if (current) {
+      current.previous!.next = current.next;
+      current.next!.previous = current.previous;
+
+      this.size -= 1;
+
+      return current;
+    }
+
+    return undefined;
+  }
+
+  dropByValue(value: T, compareFn = compare): ListNode<T> | undefined {
+    const position = this.findIndex(currentValue => compareFn(currentValue, value));
+
+    if (position < 0) return undefined;
+
+    return this.dropByIndex(position);
+  }
+
+  dropHead(): ListNode<T> | undefined {
+    const head = this.first;
+
+    if (head) {
+      this.first = head.next;
+
+      if (this.first) this.first.previous = undefined;
+      else this.last = undefined;
+
+      this.size -= 1;
+
+      return head;
+    }
+
+    return undefined;
+  }
+
+  dropTail(): ListNode<T> | undefined {
+    const tail = this.last;
+
+    if (tail) {
+      this.last = tail.previous;
+
+      if (this.last) this.last.next = undefined;
+      else this.first = undefined;
+
+      this.size -= 1;
+
+      return tail;
+    }
+
+    return undefined;
+  }
+
+  find(predicate: ListIteratorFunction<T>): ListNode<T> | undefined {
+    for (let current = this.first, position = 0; current; position += 1, current = current.next) {
+      if (predicate(current.value, position, this)) return current;
+    }
+
+    return undefined;
+  }
+
+  findIndex(predicate: ListIteratorFunction<T>): number {
+    for (let current = this.first, position = 0; current; position += 1, current = current.next) {
+      if (predicate(current.value, position, this)) return position;
+    }
+
+    return -1;
+  }
+
+  forEach<R = boolean>(callback: ListIteratorFunction<T, R>) {
+    for (let node = this.first, position = 0; node; position += 1, node = node.next) {
+      callback(node.value, position, this);
+    }
+  }
+
+  get(position: number): ListNode<T> | undefined {
+    return this.find((_, index) => position === index);
+  }
+
+  indexOf(value: T, compareFn = compare): number {
+    return this.findIndex(currentValue => compareFn(currentValue, value));
+  }
+
+  toArray(): T[] {
+    const array = new Array(this.size);
+
+    this.forEach((value, index) => (array[index!] = value));
+
+    return array;
+  }
+
+  toString(): string {
+    return this.toArray()
+      .map(value => JSON.stringify(value))
+      .join(' <-> ');
+  }
+
+  *[Symbol.iterator]() {
+    for (let node = this.first, position = 0; node; position += 1, node = node.next) {
+      yield node.value;
+    }
+  }
+}
+
+export type ListIteratorFunction<T = any, R = boolean> = (
+  value: T,
+  index?: number,
+  list?: LinkedList,
+) => R;