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node_modules/generic-pool/lib/DoublyLinkedList.js

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+"use strict";
+
+/**
+ * A Doubly Linked List, because there aren't enough in the world...
+ * this is pretty much a direct JS port of the one wikipedia
+ * https://en.wikipedia.org/wiki/Doubly_linked_list
+ *
+ * For most usage 'insertBeginning' and 'insertEnd' should be enough
+ *
+ * nodes are expected to something like a POJSO like
+ * {
+ *   prev: null,
+ *   next: null,
+ *   something: 'whatever you like'
+ * }
+ */
+class DoublyLinkedList {
+  constructor() {
+    this.head = null;
+    this.tail = null;
+    this.length = 0;
+  }
+
+  insertBeginning(node) {
+    if (this.head === null) {
+      this.head = node;
+      this.tail = node;
+      node.prev = null;
+      node.next = null;
+      this.length++;
+    } else {
+      this.insertBefore(this.head, node);
+    }
+  }
+
+  insertEnd(node) {
+    if (this.tail === null) {
+      this.insertBeginning(node);
+    } else {
+      this.insertAfter(this.tail, node);
+    }
+  }
+
+  insertAfter(node, newNode) {
+    newNode.prev = node;
+    newNode.next = node.next;
+    if (node.next === null) {
+      this.tail = newNode;
+    } else {
+      node.next.prev = newNode;
+    }
+    node.next = newNode;
+    this.length++;
+  }
+
+  insertBefore(node, newNode) {
+    newNode.prev = node.prev;
+    newNode.next = node;
+    if (node.prev === null) {
+      this.head = newNode;
+    } else {
+      node.prev.next = newNode;
+    }
+    node.prev = newNode;
+    this.length++;
+  }
+
+  remove(node) {
+    if (node.prev === null) {
+      this.head = node.next;
+    } else {
+      node.prev.next = node.next;
+    }
+    if (node.next === null) {
+      this.tail = node.prev;
+    } else {
+      node.next.prev = node.prev;
+    }
+    node.prev = null;
+    node.next = null;
+    this.length--;
+  }
+
+  // FIXME: this should not live here and has become a dumping ground...
+  static createNode(data) {
+    return {
+      prev: null,
+      next: null,
+      data: data
+    };
+  }
+}
+
+module.exports = DoublyLinkedList;