using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Runtime.CompilerServices;


namespace IOTContainer.MvvmBase
{
    /// <summary>
    /// ViewModel基础类
    /// </summary>
    public class ViewModelBase : INotifyPropertyChanged, IDataErrorInfo
    {
        #region 通知事件
        /// <summary>
        /// 特性改变事件
        /// </summary>
        public event PropertyChangedEventHandler PropertyChanged;

        /// <summary>
        /// 特性改变通知
        /// </summary>
        /// <param name="propertyName">属性名,若为空则自动获取字段名</param>
        protected virtual void RaisePropertyChanged([CallerMemberName] string propertyName = null)
        {
            this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        /// <summary>
        /// 更改属性 并通知特性改变
        /// </summary>
        /// <typeparam name="T">属性类型</typeparam>
        /// <param name="member">属性</param>
        /// <param name="value">改变值</param>
        /// <param name="propertyName">属性名,若为空则自动获取字段名</param>
        protected void SetProperty<T>(ref T member, T value, [CallerMemberName] string propertyName = null)
        {
            if (!object.Equals(member, value))
            {
                member = value;
                this.RaisePropertyChanged(propertyName);
            }
        }
        #endregion

        #region 数据验证
        /// <summary>
        /// 验证完整性错误
        /// </summary>
        public string Error
        {
            get
            {
                var resultes = new List<ValidationResult>();

                var context = new ValidationContext(this);

                if (!Validator.TryValidateObject(this, context, resultes, true) && resultes.Count > 0)
                {
                    return string.Join(Environment.NewLine, resultes.Select(r => r.ErrorMessage).ToArray());
                }

                return string.Empty;
            }
        }

        /// <summary>
        /// 验证具体字段错误
        /// </summary>
        /// <param name="columnName"></param>
        /// <returns></returns>
        public string this[string columnName]
        {
            get
            {
                var resultes = new List<ValidationResult>();

                var context = new ValidationContext(this);
                context.MemberName = columnName;
                var value = this.GetType().GetProperty(columnName).GetValue(this, null);

                if (!Validator.TryValidateProperty(value, context, resultes) && resultes.Count > 0)
                {
                    return string.Join(Environment.NewLine, resultes.Select(r => r.ErrorMessage).ToArray());
                }

                return string.Empty;
            }
        }
        #endregion
    }
}