using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq.Expressions;
using System.Reflection;

namespace DataTable
{
    /// <summary>
    /// Ускоренный обработчик свойства
    /// </summary>
    class PropertyHelper
    {
        delegate void SetterDelegate(object instanse, object[] values);

        delegate object GetterDelegate(object instanse);

        public string PropertyName { get; }
        public string PropertyDesctiption { get; }
        public Type PropertyType { get; }
        public string Id { get; }

        SetterDelegate Setter { get; }
        GetterDelegate Getter { get; }
        public PropertyHelper(PropertyInfo property)
        {
            PropertyName = property.Name;
            PropertyType = property.PropertyType;
            Id = MakeIdentity(property.PropertyType.Name, property.Name);
            PropertyDesctiption = GetDescription(property);

            var setter = property.SetMethod;
            var getter = property.GetMethod;

            var instanceExpression = Expression.Parameter(typeof(object), "instance");
            var argumentsExpression = Expression.Parameter(typeof(object[]), "arguments");
            var argumentExpressions = new List<Expression> { Expression.Convert(Expression.ArrayIndex(argumentsExpression, Expression.Constant(0)), PropertyType) };
            var callExpression = Expression.Call(Expression.Convert(instanceExpression, setter.ReflectedType), setter, argumentExpressions);
            Setter = Expression.Lambda<SetterDelegate>(callExpression, instanceExpression, argumentsExpression).Compile();
            callExpression = Expression.Call(Expression.Convert(instanceExpression, getter.ReflectedType), getter);
            Getter = Expression.Lambda<GetterDelegate>(Expression.Convert(callExpression, typeof(object)), instanceExpression).Compile();
        }

        private string GetDescription(PropertyInfo property)
        {
            var descriptionAttr = property.GetCustomAttribute<DescriptionAttribute>();
            return descriptionAttr?.Description ?? string.Empty;
        }

        void SetValues(object instance, params object[] values)
            => Setter(instance, values);

        public void Set(object instance, object value)
            => SetValues(instance, value);

        public object Get(object instance)
            => Getter(instance);

        public static string MakeIdentity(string propertyTypeName, string propertyName)
            => $"{propertyTypeName}_{propertyName}".ToLower();
    }
}