using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data.SqlTypes;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Xml;
using System.Xml.Schema;
using System.Xml.Serialization;

namespace 唯一码
{
    /// <summary>COMB 类型 GUID，要存储在数据库中或要从数据库中检索的 GUID。</summary>
    /// <remarks>COMB 类型 GUID 是由Jimmy Nilsson在他的“The Cost of GUIDs as Primary Keys”一文中设计出来的。
    /// <para>基本设计思路是这样的：既然GUID数据因毫无规律可言造成索引效率低下，影响了系统的性能，那么能不能通过组合的方式，
    /// 保留GUID的前10个字节，用后6个字节表示GUID生成的时间（DateTime），这样我们将时间信息与GUID组合起来，
    /// 在保留GUID的唯一性的同时增加了有序性，以此来提高索引效率。</para>
    /// <para>也许有人会担心GUID减少到10字节会造成数据出现重复，其实不用担心，
    /// 后6字节的时间精度可以达到 1/10000 秒，两个COMB类型数据完全相同的可能性是在这 1/10000 秒内生成的两个GUID前10个字节完全相同，这几乎是不可能的！</para>
    /// <para>理论上一天之内允许生成 864000000 个不重复的CombGuid；如果当天生成的个数大于 864000000 ，会一直累加 1 直到 2147483647 ，
    /// 也就是说实际一天之内能生成 2147483647 个不重复的CombGuid。</para>
    /// </remarks>
    public struct CombGuid : INullable, IComparable, IComparable<CombGuid>, IEquatable<CombGuid>, IXmlSerializable
    {
        #region -- Fields --

        private static readonly String _NullString = "nil";

        private static readonly Int32 _SizeOfGuid = 16;

        // Comparison orders.
        private static readonly Int32[] _GuidComparisonOrders = new Int32[16] { 10, 11, 12, 13, 14, 15, 8, 9, 6, 7, 4, 5, 0, 1, 2, 3 };

        // Parse orders.
        private static readonly Int32[] _GuidParseOrders32 = new Int32[32]
        {
            30, 31, 28, 29, 26, 27, 24, 25,
            22, 23, 20, 21,
            18, 19, 16, 17,
            12, 13, 14, 15,
            0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
        };
        private static readonly Int32[] _GuidParseOrders36 = new Int32[36]
        {
            34, 35, 32, 33, 30, 31, 28, 29,
            27,
            25, 26, 23, 24,
            22,
            20, 21, 18, 19,
            17,
            13, 14, 15, 16,
            12,
            0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
        };

        // the CombGuid is null if m_value is null
        private Byte[] m_value;

        #endregion

        #region -- 属性 --

        /// <summary>CombGuid 结构的只读实例，其值空。</summary>
        public static readonly CombGuid Null = new CombGuid(true);

        /// <summary>获取 CombGuid 结构的值。 此属性为只读。</summary>
        public Guid Value
        {
            get
            {
                if (IsNull)
                {
                    throw new SqlNullValueException();
                }
                else
                {
                    return new Guid(m_value);
                }
            }
        }

        /// <summary>获取 CombGuid 结构的日期时间属性。
        /// <para>如果同一时间批量生成了大量的 CombGuid 时，返回的日期时间是不准确的！</para>
        /// </summary>
        public DateTime DateTime
        {
            get
            {
                if (IsNull)
                {
                    throw new SqlNullValueException();
                }
                else
                {
                    var daysArray = new Byte[4];
                    var msecsArray = new Byte[4];

                    // Copy the date parts of the guid to the respective Byte arrays.
                    Array.Copy(m_value, m_value.Length - 6, daysArray, 2, 2);
                    Array.Copy(m_value, m_value.Length - 4, msecsArray, 0, 4);

                    // Reverse the arrays to put them into the appropriate order
                    Array.Reverse(daysArray);
                    Array.Reverse(msecsArray);

                    // Convert the bytes to ints
                    var days = BitConverter.ToInt32(daysArray, 0);
                    var msecs = BitConverter.ToInt32(msecsArray, 0);

                    var date = _CombBaseDate.AddDays(days);
                    if (msecs > _MaxTenthMilliseconds) { msecs = _MaxTenthMilliseconds; }
                    msecs /= 10;
                    return date.AddMilliseconds(msecs);
                }
            }
        }

        #endregion

        #region -- 构造 --

        /// <summary>实例化一个空 CombGuid 结构</summary>
        private CombGuid(Boolean isNull)
        {
            m_value = null;
        }

        /// <summary>使用指定的字节数组初始化 CombGuid 结构的新实例。</summary>
        /// <param name="value">包含初始化 CombGuid 的值的 16 元素字节数组。</param>
        public CombGuid(Byte[] value)
            : this(value, false) { }

        /// <summary>使用指定的字节数组初始化 CombGuid 结构的新实例。</summary>
        /// <param name="value">包含初始化 CombGuid 的值的 16 元素字节数组。</param>
        /// <param name="isOwner">是否 CombGuid 结构直接使用</param>
        private CombGuid(Byte[] value, Boolean isOwner)
        {
            if (value == null || value.Length != _SizeOfGuid)
            {
                throw new ArgumentException("value 的长度不是 16 个字节。");
            }
            if (isOwner)
            {
                m_value = value;
            }
            else
            {
                m_value = new Byte[_SizeOfGuid];
                value.CopyTo(m_value, 0);
            }
        }

        /// <summary>使用指定字符串所表示的值初始化 CombGuid 结构的新实例。</summary>
        /// <param name="comb">包含下面任一格式的 CombGuid 的字符串（“d”表示忽略大小写的十六进制数字）：
        /// <para>32 个连续的数字 dddddddddddddddddddddddddddddddd </para>
        /// <para>- 或 - </para>
        /// <para>12 和 4、4、4、8 位数字的分组，各组之间有连线符，dddddddddddd-dddd-dddd-dddd-dddddddd</para>
        /// </param>
        public CombGuid(String comb)
        {
            if (string.IsNullOrEmpty(comb))
                throw new ArgumentNullException(nameof(comb));

            Int32 a; Int16 b, c; Byte[] d;
            if (new GuidParser(comb).TryParse(out a, out b, out c, out d))
            {
                m_value = new Byte[_SizeOfGuid];
                Init(a, b, c, d);
            }
            else
            {
                throw CreateFormatException(comb);
            }
        }

        private static Exception CreateFormatException(String s)
        {
            return new FormatException(String.Format("Invalid CombGuid format: {0}", s));
        }

        /// <summary>使用指定的 Guid 参数初始化 CombGuid 结构的新实例。</summary>
        /// <param name="g">一个 Guid</param>
        public CombGuid(Guid g)
        {
            m_value = g.ToByteArray();
        }

        /// <summary>使用指定的整数和字节数组初始化 CombGuid 类的新实例。</summary>
        /// <param name="a">CombGuid 的开头四个字节。</param>
        /// <param name="b">CombGuid 的下两个字节。</param>
        /// <param name="c">CombGuid 的下两个字节。</param>
        /// <param name="d">CombGuid 的其余 8 个字节</param>
        public CombGuid(Int32 a, Int16 b, Int16 c, Byte[] d)
        {
            if (d == null || d.Length != 8)
                throw new ArgumentException(nameof(d) + "必须是8个字节的Bute数据");

          
            // Check that array is not too big
            if (d.Length != 8) { throw new ArgumentException("d 的长度不是 8 个字节。"); }

            m_value = new Byte[_SizeOfGuid];
            Init(a, b, c, d);
        }

        private void Init(Int32 a, Int16 b, Int16 c, Byte[] d)
        {
            m_value[0] = (Byte)(a);
            m_value[1] = (Byte)(a >> 8);
            m_value[2] = (Byte)(a >> 16);
            m_value[3] = (Byte)(a >> 24);
            m_value[4] = (Byte)(b);
            m_value[5] = (Byte)(b >> 8);
            m_value[6] = (Byte)(c);
            m_value[7] = (Byte)(c >> 8);
            m_value[8] = d[0];
            m_value[9] = d[1];
            m_value[10] = d[2];
            m_value[11] = d[3];
            m_value[12] = d[4];
            m_value[13] = d[5];
            m_value[14] = d[6];
            m_value[15] = d[7];
        }

        /// <summary>使用指定的值初始化 CombGuid 结构的新实例。</summary>
        /// <param name="a">CombGuid 的开头四个字节。</param>
        /// <param name="b">CombGuid 的下两个字节。</param>
        /// <param name="c">CombGuid 的下两个字节。</param>
        /// <param name="d">CombGuid 的下一个字节。</param>
        /// <param name="e">CombGuid 的下一个字节。</param>
        /// <param name="f">CombGuid 的下一个字节。</param>
        /// <param name="g">CombGuid 的下一个字节。</param>
        /// <param name="h">CombGuid 的下一个字节。</param>
        /// <param name="i">CombGuid 的下一个字节。</param>
        /// <param name="j">CombGuid 的下一个字节。</param>
        /// <param name="k">CombGuid 的下一个字节。</param>
        public CombGuid(Int32 a, Int16 b, Int16 c, Byte d, Byte e, Byte f, Byte g, Byte h, Byte i, Byte j, Byte k)
        {
            m_value = new Byte[_SizeOfGuid];

            m_value[0] = (Byte)(a);
            m_value[1] = (Byte)(a >> 8);
            m_value[2] = (Byte)(a >> 16);
            m_value[3] = (Byte)(a >> 24);
            m_value[4] = (Byte)(b);
            m_value[5] = (Byte)(b >> 8);
            m_value[6] = (Byte)(c);
            m_value[7] = (Byte)(c >> 8);
            m_value[8] = d;
            m_value[9] = e;
            m_value[10] = f;
            m_value[11] = g;
            m_value[12] = h;
            m_value[13] = i;
            m_value[14] = j;
            m_value[15] = k;
        }

        #endregion

        #region -- 方法 --

        #region - ToByteArray -

        /// <summary>将此 CombGuid 结构转换为字节数组</summary>
        /// <returns>16 元素字节数组。</returns>
        public Byte[] ToByteArray()
        {
            var ret = new Byte[_SizeOfGuid];
            m_value.CopyTo(ret, 0);
            return ret;
        }

        #endregion

        #region - GetByteArray -

        /// <summary>直接获取此 CombGuid 结构内部的字节数组，如果此 CombGuid 为空，返回空值。
        /// <para>调用此方法后，不要对获取的字节数组做任何改变！！！</para>
        /// </summary>
        /// <returns>16 元素字节数组 或 null。</returns>
        [EditorBrowsable(EditorBrowsableState.Advanced)]
        public Byte[] GetByteArray()
        {
            return m_value;
        }

        #endregion

        #region - ToString -

        /// <summary>已重载，将此 CombGuid 结构转换为字符串。</summary>
        /// <returns>返回该 CombGuid 结构的字符串表示形式。</returns>
        public override String ToString()
        {
            return ToString(CombGuidFormatStringType.Comb);
        }

        /// <summary>根据所提供的格式方式，返回此 CombGuid 实例值的字符串表示形式。</summary>
        /// <param name="formatType">格式化方式，它指示如何格式化此 CombGuid 的值。</param>
        /// <returns>此 CombGuid 的值，用一系列指定格式的小写十六进制位表示</returns>
        public String ToString(CombGuidFormatStringType formatType)
        {
            if (IsNull) { return _NullString; }

            var offset = 0;
            var strLength = 36;
            var dash = true;
            if (formatType == CombGuidFormatStringType.Guid32Digits || formatType == CombGuidFormatStringType.Comb32Digits)
            {
                strLength = 32;
                dash = false;
            }
            var guidChars = new Char[strLength];
            var isComb = formatType == CombGuidFormatStringType.Comb || formatType == CombGuidFormatStringType.Comb32Digits;

            #region MS GUID类内部代码

            //g[0] = (Byte)(_a);
            //g[1] = (Byte)(_a >> 8);
            //g[2] = (Byte)(_a >> 16);
            //g[3] = (Byte)(_a >> 24);
            //g[4] = (Byte)(_b);
            //g[5] = (Byte)(_b >> 8);
            //g[6] = (Byte)(_c);
            //g[7] = (Byte)(_c >> 8);
            //g[8] = _d;
            //g[9] = _e;
            //g[10] = _f;
            //g[11] = _g;
            //g[12] = _h;
            //g[13] = _i;
            //g[14] = _j;
            //g[15] = _k;
            //// [{|(]dddddddd[-]dddd[-]dddd[-]dddd[-]dddddddddddd[}|)]
            //offset = HexsToChars(guidChars, offset, _a >> 24, _a >> 16);
            //offset = HexsToChars(guidChars, offset, _a >> 8, _a);
            //if (dash) guidChars[offset++] = '-';
            //offset = HexsToChars(guidChars, offset, _b >> 8, _b);
            //if (dash) guidChars[offset++] = '-';
            //offset = HexsToChars(guidChars, offset, _c >> 8, _c);
            //if (dash) guidChars[offset++] = '-';
            //offset = HexsToChars(guidChars, offset, _d, _e);
            //if (dash) guidChars[offset++] = '-';
            //offset = HexsToChars(guidChars, offset, _f, _g);
            //offset = HexsToChars(guidChars, offset, _h, _i);
            //offset = HexsToChars(guidChars, offset, _j, _k);

            #endregion

            if (isComb)
            {
                offset = HexsToChars(guidChars, offset, m_value[10], m_value[11]);
                offset = HexsToChars(guidChars, offset, m_value[12], m_value[13]);
                offset = HexsToChars(guidChars, offset, m_value[14], m_value[15]);
                if (dash) { guidChars[offset++] = '-'; }
                offset = HexsToChars(guidChars, offset, m_value[8], m_value[9]);
                if (dash) { guidChars[offset++] = '-'; }
                offset = HexsToChars(guidChars, offset, m_value[6], m_value[7]);
                if (dash) { guidChars[offset++] = '-'; }
                offset = HexsToChars(guidChars, offset, m_value[4], m_value[5]);
                if (dash) { guidChars[offset++] = '-'; }
                offset = HexsToChars(guidChars, offset, m_value[0], m_value[1]);
                offset = HexsToChars(guidChars, offset, m_value[2], m_value[3]);
            }
            else
            {
                offset = HexsToChars(guidChars, offset, m_value[3], m_value[2]);
                offset = HexsToChars(guidChars, offset, m_value[1], m_value[0]);
                if (dash) { guidChars[offset++] = '-'; }
                offset = HexsToChars(guidChars, offset, m_value[5], m_value[4]);
                if (dash) { guidChars[offset++] = '-'; }
                offset = HexsToChars(guidChars, offset, m_value[7], m_value[6]);
                if (dash) { guidChars[offset++] = '-'; }
                offset = HexsToChars(guidChars, offset, m_value[8], m_value[9]);
                if (dash) { guidChars[offset++] = '-'; }
                offset = HexsToChars(guidChars, offset, m_value[10], m_value[11]);
                offset = HexsToChars(guidChars, offset, m_value[12], m_value[13]);
                offset = HexsToChars(guidChars, offset, m_value[14], m_value[15]);
            }

            return new String(guidChars, 0, strLength);
        }

        private static Int32 HexsToChars(Char[] guidChars, Int32 offset, Int32 a, Int32 b)
        {
            guidChars[offset++] = HexToChar(a >> 4);
            guidChars[offset++] = HexToChar(a);
            guidChars[offset++] = HexToChar(b >> 4);
            guidChars[offset++] = HexToChar(b);
            return offset;
        }

        private static Char HexToChar(Int32 a)
        {
            a = a & 0xf;
            return (Char)((a > 9) ? a - 10 + 0x61 : a + 0x30);
        }

        #endregion

        #endregion

        #region -- 静态方法 --

        private static readonly DateTime _CombBaseDate = new DateTime(1900, 1, 1);
        private static Int32 _LastDays; // 天数
        private static Int32 _LastTenthMilliseconds; // 单位：1/10 毫秒
        private static readonly Int32 _MaxTenthMilliseconds = 863999999;

        #region - NewComb -

        /// <summary>初始化 CombGuid 结构的新实例。</summary>
        /// <returns>一个新的 CombGuid 对象。</returns>
        public static CombGuid NewComb()
        {
            var guidArray = Guid.NewGuid().ToByteArray();

            var now = DateTime.Now;

            // Get the days and milliseconds which will be used to build the Byte String
            var days = new TimeSpan(now.Ticks - _CombBaseDate.Ticks).Days;
            var tenthMilliseconds = (Int32)(now.TimeOfDay.TotalMilliseconds * 10D);
            var lastDays = _LastDays;
            var lastTenthMilliseconds = _LastTenthMilliseconds;
            if (days > lastDays)
            {
                Interlocked.CompareExchange(ref _LastDays, days, lastDays);
                Interlocked.CompareExchange(ref _LastTenthMilliseconds, tenthMilliseconds, lastTenthMilliseconds);
            }
            else
            {
                if (tenthMilliseconds > lastTenthMilliseconds)
                {
                    Interlocked.CompareExchange(ref _LastTenthMilliseconds, tenthMilliseconds, lastTenthMilliseconds);
                }
                else
                {
                    if (_LastTenthMilliseconds < Int32.MaxValue) { Interlocked.Increment(ref _LastTenthMilliseconds); }
                    tenthMilliseconds = _LastTenthMilliseconds;
                }
            }
            // Convert to a Byte array
            var daysArray = BitConverter.GetBytes(days);
            var msecsArray = BitConverter.GetBytes(tenthMilliseconds);

            // Reverse the bytes to match SQL Servers ordering
            Array.Reverse(daysArray);
            Array.Reverse(msecsArray);

            // Copy the bytes into the guid
            Array.Copy(daysArray, daysArray.Length - 2, guidArray, guidArray.Length - 6, 2);
            //Array.Copy(msecsArray, msecsArray.Length - 4, guidArray, guidArray.Length - 4, 4);
            Array.Copy(msecsArray, 0, guidArray, guidArray.Length - 4, 4);

            return new CombGuid(guidArray, true);
        }

        #endregion

        #region - Parse -

        /// <summary>将 CombGuid 的字符串表示形式转换为等效的 CombGuid 结构。</summary>
        ///