'use strict'
/**
 * Copyright (c) 2017~2019, OBCon Inc.
 * All rights reserved.
 */

/**
 * @file
 * @copyright 2017~2019, OBCon Inc.
 * @author gye hyun james kim [pnuskgh@gmail.com]
 */

class Node {
    constructor(data) {
        this.prev = null;
        this.data = data;
        this.next = null;
    }
}

class LinkedList {
    constructor(isSingle=true) {
        this.size = 0;
        this.head = null;
        this.tail = null;
        this.isSingle = isSingle;
    }

    isEmpty() {
        return this.size == 0;
    }

    insert(item) {
        if (this.isSingle) {
            this._insert_single(item);
        } else {
            this._insert_double(item);
        }
    }

    _insert_single(item) {                                          //--- Head에 데이터를 추가 한다.
        if (this.head == null) {
            this.head = new Node(item);
        } else {
            let tmp = this.head;
            this.head = new Node(item);
            this.head.next = tmp;
        }
        this.size = this.size + 1;
    }

    _insert_double(item) {                                          //--- Head에 데이터를 추가 한다.
        if (this.head == null) {
            this.head = new Node(item);
            this.tail = this.head;
        } else {
            let tmp = this.head;
            this.head = new Node(item);
            this.head.next = tmp;
            tmp.prev = this.head;
        }
        this.size = this.size + 1;
    }

    insertAtTail() {
        if (this.tail == null) {
            this.tail = new Node(item);
            this.head = this.tail;
        } else {
            let tmp = this.tail;
            this.tail = new Node(item);
            this.tail.prev = tmp;
            tmp.next = this.tail;
        }
        this.size = this.size + 1;
    }

    remove(item) {
        if (this.isSingle) {
            this._remove_single(item);
        } else {
            this._remove_double(item);
        }
    }

    _remove_single(item) {                                          //--- 값으로 데이터를 삭제 한다.
        let nodePrev = null;
        let nodeCurrent = this.head;
        for (let idx = 0; idx < this.size; idx++) {
            if (nodeCurrent.data == item) {
                if (idx == 0) {
                    this.head = nodeCurrent.next;
                } else {
                    nodePrev.next = nodeCurrent.next;
                }
                this.size = this.size - 1;
                break;
            }

            nodePrev = nodeCurrent;
            nodeCurrent = nodeCurrent.next;
        }
    }

    _remove_double(item) { 
    }

    deleteAtHead() {
        if (this.isSingle) {
            return this._deleteAtHead_single();
        } else {
            return this._deleteAtHead_double();
        }
    }

    _deleteAtHead_single() {
        let rtval = null;

        if (this.head != null) {
            rtval = this.head.data;
            this.head = this.head.next;
            this.size = this.size - 1;
        }
        return rtval;
    }

    _deleteAtHead_double() {
        let rtval = null;

        if (this.head != null) {
            rtval = this.head.data;
            
            if (this.head == this.tail) {
                this.head = null;
                this.tail = null;
            } else {
                this.head = this.head.next;
                this.head.prev = null;
            }
            this.size = this.size - 1;
        }
        return rtval;
    }

    deleteAtTail() {
        let rtval = null;

        if (this.tail != null) {
            rtval = this.head.data;
            
            if (this.head == this.tail) {
                this.head = null;
                this.tail = null;
            } else {
                this.tail = this.tail.prev;
                this.tail.next = null;
            }
            this.size = this.size - 1;
        }
        return rtval;
    }

    find(item) {
        let rtFlag = false;
        let nodeCurrent = this.head;
        for (let idx = 0; idx < this.size; idx++) {
            if (nodeCurrent.data == item) {
                rtFlag = true;
                break;
            }
            nodeCurrent = nodeCurrent.next;
        }
        return rtFlag;
    }
}

module.exports = LinkedList;