using System;
using System.Collections.Generic;
using NewLife;
using NewLife.Log;
using XCode.DataAccessLayer;

namespace XCode.Transform
{
    /// <summary>实体转换</summary>
    public class EntityTransform
    {
        #region 属性
        /// <summary>源</summary>
        public String SrcConn { get; set; }

        /// <summary>目的</summary>
        public String DesConn { get; set; }

        private ICollection<String> _TableNames;
        /// <summary>要导数据的表，为空表示全部</summary>
        public ICollection<String> TableNames
        {
            get
            {
                if (_TableNames == null)
                {
                    var list = new HashSet<String>(StringComparer.OrdinalIgnoreCase);
                    if (!String.IsNullOrEmpty(SrcConn))
                    {
                        foreach (var item in DAL.Create(SrcConn).Tables)
                        {
                            if (!String.IsNullOrEmpty(item.TableName)) list.Add(item.TableName);
                        }
                    }
                    _TableNames = list;
                }
                return _TableNames;
            }
            set { _TableNames = value; }
        }

        /// <summary>每批处理多少行数据，默认1000</summary>
        public Int32 BatchSize { get; set; } = 1000;

        /// <summary>是否允许插入自增列</summary>
        public Boolean AllowInsertIdentity { get; set; }

        /// <summary>仅迁移到空表。对于已有数据的表，不执行迁移。</summary>
        public Boolean OnlyTransformToEmptyTable { get; set; }

        /// <summary>是否显示SQL</summary>
        public Boolean ShowSQL { get; set; }
        #endregion

        #region 局部迁移
        /// <summary>需要局部迁移的表。局部迁移就是只迁移一部分数据。</summary>
        public ICollection<String> PartialTableNames { get; } = new HashSet<String>(StringComparer.OrdinalIgnoreCase);

        /// <summary>局部迁移记录数。默认1000</summary>
        public Int32 PartialCount { get; set; } = 1000;

        /// <summary>局部迁移降序。默认为true，也就是只迁移最后的一批数据。</summary>
        public Boolean PartialDesc { get; set; } = true;
        #endregion

        #region 方法
        /// <summary>把一个链接的数据全部导入到另一个链接</summary>
        /// <returns></returns>
        public Int32 Transform()
        {
            var dal = DAL.Create(SrcConn);

            // 取得实际数据库所有表，把视图过滤掉
            var tables = dal.Tables;
            if (tables == null || tables.Count < 1) return 0;

            tables.RemoveAll(t => t.IsView);
            if (tables == null || tables.Count < 1) return 0;

            // 取所有需要迁移的表，过滤得出最后需要迁移的表
            var tns = _TableNames;
            if (tns != null && tns.Count > 0) tables.RemoveAll(t => !tns.Contains(t.TableName) && !tns.Contains(t.Name));

            var total = 0;
            foreach (var item in tables)
            {
                if (OnTransformTable != null)
                {
                    var e = new EventArgs<IDataTable>(item);
                    OnTransformTable(this, e);
                    if (e.Arg == null) continue;
                }

                if (!PartialTableNames.Contains(item.TableName) && !PartialTableNames.Contains(item.Name))
                    total += TransformTable(dal.CreateOperate(item.TableName));
                else
                    total += TransformTable(dal.CreateOperate(item.TableName), PartialCount, PartialDesc);
            }

            return total;
        }

        /// <summary>把一个表的数据全部导入到另一个表</summary>
        /// <param name="eop">实体操作者。</param>
        /// <param name="count">要迁移的记录数，默认0表示全部</param>
        /// <param name="isDesc">是否降序。默认升序</param>
        /// <param name="getData">用于获取数据的委托</param>
        /// <returns></returns>
        public Int32 TransformTable(IEntityOperate eop, Int32 count = 0, Boolean? isDesc = null, Func<Int32, Int32, IEntityList> getData = null)
        {
            var set = Setting.Current;
            var oldInitData = set.InitData;
            set.InitData = false;

            var name = eop.TableName;
            eop.ConnName = SrcConn;
            if (count <= 0) count = eop.Count;
            if (getData == null)
            {
                var order = "";
                if (isDesc != null)
                {
                    var fi = eop.Unique;
                    if (fi != null) order = isDesc.Value ? fi.Desc() : fi.Asc();
                }
                getData = (start, max) => eop.FindAll("", order, null, start, max);
            }

            // 在目标链接上启用事务保护
            eop.ConnName = DesConn;
            // 提取实体会话，避免事务保护作用在错误的连接上
            var session = eop.Session;
            session.BeginTrans();
            try
            {
                XTrace.WriteLine("{0} 共 {1}", name, count);
                if (OnlyTransformToEmptyTable && session.LongCount > 0)
                {
                    XTrace.WriteLine("{0} 非空，跳过", name);
                    session.Rollback();
                    return 0;
                }

                // 允许插入自增
                var oldII = eop.AllowInsertIdentity;
                if (AllowInsertIdentity) eop.AllowInsertIdentity = true;

                // 关闭SQL日志
                var ss = session.Dal.Session;
                var oldShowSql = ss.ShowSQL;
                ss.ShowSQL = ShowSQL;

                var total = 0;
                var index = 0;
                while (true)
                {
                    var size = Math.Min(BatchSize, count - index);
                    if (size <= 0) break;

                    eop.ConnName = SrcConn;
                    var list = getData(index, size);
                    if (list == null || list.Count < 1) break;
                    index += list.Count;

                    // 处理事件，外部可以修改实体数据
                    if (OnTransformEntity != null)
                    {
                        var e = new EventArgs<IEntity>(null);
                        foreach (var entity in list)
                        {
                            e.Arg = entity;
                            OnTransformEntity(this, e);
                        }
                    }

                    eop.ConnName = DesConn;
                    //var rs = list.Insert(true);
                    // 为了避免干扰，必须越过Valid
                    var rs = 0;
                    foreach (var item in list)
                    {
                        rs += session.Insert(item);
                    }
                    XTrace.WriteLine("{0} 导入 {1}/{2} {3:p}", name, index, count, (Double)index / count);

                    total += rs;
                }
                ss.ShowSQL = oldShowSql;

                // 关闭插入自增
                if (AllowInsertIdentity) eop.AllowInsertIdentity = oldII;

                // 在目标链接上启用事务保护
                eop.ConnName = DesConn;
                session.Commit();

                set.InitData = oldInitData;

                return total;
            }
            catch (Exception ex)
            {
                XTrace.WriteLine("{0} 错误 {1}", name, ex.ToString());
                // 在目标链接上启用事务保护
                eop.ConnName = DesConn;
                session.Rollback();
                throw;
            }
        }
        #endregion

        #region 事件
        /// <summary>转换表时触发。如果参数被置空，表示不转换该表</summary>
        public event EventHandler<EventArgs<IDataTable>> OnTransformTable;

        /// <summary>转换实体时触发</summary>
        public event EventHandler<EventArgs<IEntity>> OnTransformEntity;
        #endregion
    }
}