using System;
using System.Collections.Generic;
using System.ComponentModel;
using XCode.Cache;
using XCode.Configuration;
using XCode.DataAccessLayer;

namespace XCode
{
    partial class Entity<TEntity>
    {
        /// <summary>实体元数据</summary>
        public static class Meta
        {
            static Meta()
            {
                // 避免实际应用中，直接调用Entity.Meta的静态方法时，没有引发TEntity的静态构造函数。
                var entity = new TEntity();
            }

            #region 主要属性
            /// <summary>实体类型</summary>
            public static Type ThisType => typeof(TEntity);

            /// <summary>实体操作者</summary>
            public static IEntityOperate Factory
            {
                get
                {
                    var type = ThisType;
                    if (type.IsInterface) return null;

                    return EntityFactory.CreateOperate(type);
                }
            }

            [ThreadStatic]
            private static EntitySession<TEntity> _Session;
            /// <summary>实体会话。线程静态</summary>
            public static EntitySession<TEntity> Session => _Session ?? (_Session = EntitySession<TEntity>.Create(ConnName, TableName));
            #endregion

            #region 基本属性
            private static Lazy<TableItem> _Table = new Lazy<TableItem>(() => TableItem.Create(ThisType));
            /// <summary>表信息</summary>
            public static TableItem Table => _Table.Value;

            [ThreadStatic]
            private static String _ConnName;
            /// <summary>链接名。线程内允许修改，修改者负责还原。若要还原默认值，设为null即可</summary>
            public static String ConnName
            {
                get { if (_ConnName.IsNullOrEmpty()) _ConnName = Table.ConnName; return _ConnName; }
                set
                {
                    _Session = null;
                    _ConnName = value;
                }
            }

            [ThreadStatic]
            private static String _TableName;
            /// <summary>表名。线程内允许修改，修改者负责还原</summary>
            public static String TableName
            {
                get
                {
                    if (_TableName == null)
                    {
                        var name = Table.TableName;

                        //// 检查自动表前缀
                        //var dal = DAL.Create(ConnName);
                        //var pf = dal.Db.TablePrefix;
                        //if (!pf.IsNullOrEmpty() && !name.StartsWithIgnoreCase(pf)) name = pf + name;

                        _TableName = name;
                    }
                    return _TableName;
                }
                set
                {
                    _Session = null;
                    _TableName = value;
                }
            }

            /// <summary>所有数据属性</summary>
            public static FieldItem[] AllFields => Table.AllFields;

            /// <summary>所有绑定到数据表的属性</summary>
            public static FieldItem[] Fields => Table.Fields;

            /// <summary>字段名集合，不区分大小写的哈希表存储，外部不要修改元素数据</summary>
            public static ICollection<String> FieldNames => Table.FieldNames;

            /// <summary>唯一键，返回第一个标识列或者唯一的主键</summary>
            public static FieldItem Unique
            {
                get
                {
                    var dt = Table;
                    if (dt.Identity != null) return dt.Identity;
                    if (dt.PrimaryKeys.Length == 1) return dt.PrimaryKeys[0];
                    return null;
                }
            }

            /// <summary>主字段。主字段作为业务主要字段，代表当前数据行意义</summary>
            public static FieldItem Master => Table.Master ?? Unique;
            #endregion

            #region 事务保护
            /// <summary>开始事务</summary>
            /// <returns>剩下的事务计数</returns>
            //[Obsolete("=>Session")]
            [EditorBrowsable(EditorBrowsableState.Never)]
            public static Int32 BeginTrans() => Session.BeginTrans();

            /// <summary>提交事务</summary>
            /// <returns>剩下的事务计数</returns>
            //[Obsolete("=>Session")]
            [EditorBrowsable(EditorBrowsableState.Never)]
            public static Int32 Commit() => Session.Commit();

            /// <summary>回滚事务，忽略异常</summary>
            /// <returns>剩下的事务计数</returns>
            //[Obsolete("=>Session")]
            [EditorBrowsable(EditorBrowsableState.Never)]
            public static Int32 Rollback() => Session.Rollback();

            /// <summary>创建事务</summary>
            public static EntityTransaction CreateTrans() => new EntityTransaction<TEntity>();
            #endregion

            #region 辅助方法
            /// <summary>格式化关键字</summary>
            /// <param name="name">名称</param>
            /// <returns></returns>
            public static String FormatName(String name) => Session.Dal.Db.FormatName(name);

            /// <summary>格式化时间</summary>
            /// <param name="dateTime"></param>
            /// <returns></returns>
            public static String FormatDateTime(DateTime dateTime) => Session.Dal.Db.FormatDateTime(dateTime);

            /// <summary>格式化数据为SQL数据</summary>
            /// <param name="name">名称</param>
            /// <param name="value">数值</param>
            /// <returns></returns>
            public static String FormatValue(String name, Object value) => FormatValue(Table.FindByName(name), value);

            /// <summary>格式化数据为SQL数据</summary>
            /// <param name="field">字段</param>
            /// <param name="value">数值</param>
            /// <returns></returns>
            public static String FormatValue(FieldItem field, Object value) => Session.Dal.Db.FormatValue(field?.Field, value);
            #endregion

            #region 缓存
            /// <summary>实体缓存</summary>
            /// <returns></returns>
            //[Obsolete("=>Session")]
            //[EditorBrowsable(EditorBrowsableState.Never)]
            public static EntityCache<TEntity> Cache => Session.Cache;

            /// <summary>单对象实体缓存。</summary>
            //[Obsolete("=>Session")]
            //[EditorBrowsable(EditorBrowsableState.Never)]
            public static ISingleEntityCache<Object, TEntity> SingleCache => Session.SingleCache;

            /// <summary>总记录数，小于1000时是精确的，大于1000时缓存10分钟</summary>
            //[Obsolete("=>Session")]
            //[EditorBrowsable(EditorBrowsableState.Never)]
            public static Int32 Count => (Int32)Session.LongCount;
            #endregion

            #region 分表分库
            /// <summary>在分库上执行操作，自动还原</summary>
            /// <param name="connName"></param>
            /// <param name="tableName"></param>
            /// <param name="func"></param>
            /// <returns></returns>
            public static T ProcessWithSplit<T>(String connName, String tableName, Func<T> func)
            {
                using (var split = CreateSplit(connName, tableName))
                {
                    return func();
                }
            }

            /// <summary>创建分库会话，using结束时自动还原</summary>
            /// <param name="connName">连接名</param>
            /// <param name="tableName">表名</param>
            /// <returns></returns>
            public static IDisposable CreateSplit(String connName, String tableName) => new SplitPackge(connName, tableName);

            class SplitPackge : IDisposable
            {
                /// <summary>连接名</summary>
                public String ConnName { get; set; }

                /// <summary>表名</summary>
                public String TableName { get; set; }

                public SplitPackge(String connName, String tableName)
                {
                    ConnName = Meta.ConnName;
                    TableName = Meta.TableName;

                    Meta.ConnName = connName;
                    Meta.TableName = tableName;
                }

                public void Dispose()
                {
                    Meta.ConnName = ConnName;
                    Meta.TableName = TableName;
                }
            }
            #endregion

            #region 模块
            internal static EntityModules _Modules = new EntityModules(typeof(TEntity));
            /// <summary>实体模块集合</summary>
            public static EntityModules Modules => _Modules;
            #endregion
        }
    }
}