using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Web;

namespace VueWebApi.Util
{
    /// <summary>
    /// 值转换器
    /// </summary>
    /// <typeparam name="T">指定值的类型</typeparam>
    /// <param name="obj">取值来源</param>
    /// <returns>返回指定类型的值</returns>
    [Serializable]
    public delegate T ObjectValueParser<out T>(object obj);
    /// <summary>
    /// 尝试将值转换成指定类型 返回转换结果
    /// </summary>
    /// <typeparam name="T">指定值的类型</typeparam>
    /// <param name="obj">取值来源</param>
    /// <param name="valueOutput">若转换成功 则out转换结果 否则 out默认T类型值</param>
    /// <returns></returns>
    public delegate bool ObjectValueTryParser<T>(object obj, out T valueOutput);
    /// <summary>
    /// 尝试将值转换成指定类型 返回转换结果
    /// </summary>
    /// <typeparam name="T">指定值的类型</typeparam>
    /// <param name="str">取值来源字符串</param>
    /// <returns>返回指定类型的值</returns>
    [Serializable]
    public delegate T StringValueParser<out T>(string str);
    /// <summary>
    /// 尝试将值转换成指定类型 返回转换成功与否
    /// </summary>
    /// <typeparam name="T">指定值的类型</typeparam>
    /// <param name="str">取值来源字符串</param>
    /// <param name="valueOutput">若转换成功 则out转换结果 否则 out默认T类型值</param>
    /// <returns></returns>
    [Serializable]
    public delegate bool StringValueTryParser<T>(string str, out T valueOutput);
    /// <summary>
    /// 实体帮助类
    /// </summary>
    public class EntityHelper
    {
        /// <summary>
        /// 从一行数据中尝试获取指定列名的值
        /// </summary>
        /// <param name="dr">源数据行</param>
        /// <param name="columnName">指定列名</param>
        /// <returns>若指定的列名存在并有效则返回取到的对象，若指定列名不存在或者为无效数据则返回null</returns>
        public static object GetObject(DataRow dr, string columnName)
        {
            if (dr != null && dr.Table.Columns.Contains(columnName) && dr[columnName] != null && dr[columnName] != DBNull.Value)
                return dr[columnName];
            return null;
        }
        /// <summary>
        /// 从一行数据中尝试获取指定引用类型的值
        /// </summary>
        /// <typeparam name="T">指定类型的值</typeparam>
        /// <param name="dr">源数据行</param>
        /// <param name="columnName">列名</param>
        /// <param name="defVal">列无效时返回的默认值</param>
        /// <param name="parser">值转换器 若给定的值转换器为null，则使用as强制转换，若as转换为null 则返回默认值</param>
        /// <returns></returns>
        public static T GetT<T>(DataRow dr, string columnName, T defVal, ObjectValueParser<T> parser = null) where T : class
        {
            var obj = GetObject(dr, columnName);
            return Get(obj, defVal, parser);
        }
        /// <summary>
        /// 将对象转换为指定类型数据 转换失败返回设置的默认值
        /// </summary>
        /// <typeparam name="T">指定的类型</typeparam>
        /// <param name="source">数据源</param>
        /// <param name="defVal">列无效时返回的默认值</param>
        /// <param name="parser">值转换器 若给定的值转换器为null，则使用as强制转换，若as转换为null 则返回默认值</param>
        /// <returns></returns>
        public static T Get<T>(object source, T defVal, ObjectValueParser<T> parser = null) where T : class
        {
            if (source == null) return defVal;
            if (parser != null)
            {
                return parser(source);
            }
            return source as T ?? defVal;
        }
        /// <summary>
        /// 从一行数据中尝试获取指定引用类型的值
        /// </summary>
        /// <typeparam name="T">指定的类型</typeparam>
        /// <param name="dr">源数据行</param>
        /// <param name="columnName">列名</param>
        /// <param name="defVal">列无效时返回的默认值</param>
        /// <param name="parser">值转换器 若给定的值转换器为null，则使用as强制转换，若as转换为null 则返回默认值</param>
        /// <returns></returns>
        public static T TryGetT<T>(DataRow dr, string columnName, T defVal, ObjectValueTryParser<T> parser = null) where T : class
        {
            var obj = GetObject(dr, columnName);
            return TryGetT(obj, defVal, parser);
        }
        /// <summary>
        /// 将对象尝试转换为指定类型的数据 转换失败返回指定的默认值
        /// </summary>
        /// <typeparam name="T">指定的类型</typeparam>
        /// <param name="source">数据源</param>
        /// <param name="defVal">默认值</param>
        /// <param name="parser">值转换器 若给定的值转换器为null，则使用as强制转换，若as转换为null 则返回默认值</param>
        /// <returns></returns>
        public static T TryGetT<T>(object source, T defVal, ObjectValueTryParser<T> parser = null) where T : class
        {
            if (source == null) return defVal;
            if (parser == null) return source as T ?? defVal;
            T temp;
            if (parser(source, out temp))
            {
                return temp;
            }
            return source as T ?? defVal;
        }

        /// <summary>
        /// 从一行数据中尝试获取指定值类型的值
        /// </summary>
        /// <typeparam name="T">指定类型的值</typeparam>
        /// <param name="dr">源数据行</param>
        /// <param name="columnName">列名</param>
        /// <param name="defVal">列无效时返回的默认值</param>
        /// <param name="parser">值转换器</param>
        /// <returns></returns>
        public static T GetT<T>(DataRow dr, string columnName, T defVal, StringValueParser<T> parser) where T : struct
        {
            var obj = GetObject(dr, columnName);
            return GetT(obj, defVal, parser);
        }
        /// <summary>
        /// 将对象转换为指定类型数据 转换失败返回设置的默认值
        /// </summary>
        /// <typeparam name="T">指定的类型</typeparam>
        /// <param name="source">数据源</param>
        /// <param name="defVal">列无效时返回的默认值</param>
        /// <param name="parser">值转换器</param>
        /// <returns></returns>
        public static T GetT<T>(object source, T defVal, StringValueParser<T> parser) where T : struct
        {
            return source != null ? parser(source.ToString()) : defVal;
        }

        /// <summary>
        /// 从一行数据中尝试获取指定值类型的值
        /// </summary>
        /// <typeparam name="T">指定类型的值</typeparam>
        /// <param name="dr">源数据行</param>
        /// <param name="columnName">列名</param>
        /// <param name="defVal">列无效时返回的默认值</param>
        /// <param name="parser">值转换器</param>
        /// <returns></returns>
        public static T TryGetT<T>(DataRow dr, string columnName, T defVal, StringValueTryParser<T> parser) where T : struct
        {
            var obj = GetObject(dr, columnName);
            return TryGetT(obj, defVal, parser);
        }

        /// <summary>
        /// 将对象尝试转换为指定类型的数据 转换失败返回指定的默认值
        /// </summary>
        /// <typeparam name="T">指定的类型</typeparam>
        /// <param name="obj">数据源</param>
        /// <param name="defVal">默认值</param>
        /// <param name="parser">值转换器</param>
        /// <returns></returns>
        public static T TryGetT<T>(object obj, T defVal, StringValueTryParser<T> parser) where T : struct
        {
            if (obj != null)
            {
                T val;
                if (parser(obj.ToString(), out val))
                {
                    return val;
                }
            }
            return defVal;
        }
        /// <summary>
        /// 从一行数据中尝试获取字符串
        /// </summary>
        /// <param name="dr">源数据行</param>
        /// <param name="columnName">列名</param>
        /// <param name="defVal">列无效时返回的默认值</param>
        /// <returns></returns>
        public static string GetString(DataRow dr, string columnName, string defVal)
        {
            var obj = GetObject(dr, columnName);
            return obj != null ? obj.ToString() : defVal;
        }
        /// <summary>
        /// 获取字符串 检测  数据源为空时返回默认值
        /// </summary>
        /// <param name="source">数据源</param>
        /// <param name="defVal">默认值</param>
        /// <returns></returns>
        public static string GetString(object source, string defVal)
        {
            if (source != null)
            {
                return source as string ?? source.ToString();
            }
            return defVal;
        }
        /// <summary>
        /// 从一行数据中尝试获取整数
        /// </summary>
        /// <param name="dr">源数据行</param>
        /// <param name="columnName">列名</param>
        /// <param name="defVal">列无效时返回的默认值</param>
        /// <returns></returns>
        public static int GetInt(DataRow dr, string columnName, int defVal)
        {
            return TryGetT(dr, columnName, defVal, int.TryParse);
        }
        /// <summary>
        /// 从数据员获取整数
        /// </summary>
        /// <param name="source">数据源</param>
        /// <param name="defVal">获取失败时的默认值</param>
        /// <returns></returns>
        public static int GetInt(object source, int defVal)
        {
            return TryGetT(source, defVal, int.TryParse);
        }
        /// <summary>
        /// 从一行数据中尝试获取日期
        /// </summary>
        /// <param name="dr">源数据行</param>
        /// <param name="columnName">列名</param>
        /// <param name="defVal">列无效时返回的默认值</param>
        /// <returns></returns>
        public static DateTime GetDateTime(DataRow dr, string columnName, DateTime defVal)
        {
            return TryGetT(dr, columnName, defVal, DateTime.TryParse);
        }
        /// <summary>
        /// 从数据源中 获取日期
        /// </summary>
        /// <param name="source">数据源</param>
        /// <param name="defVal">获取失败时的默认值</param>
        /// <returns></returns>
        public static DateTime GetDateTime(object source, DateTime defVal)
        {
            return TryGetT(source, defVal, DateTime.TryParse);
        }
    }
}