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

namespace TypeUtil {
  public static class TypeExtensions {
    public static FastPropertyInfo<T> GetProperty<T>(this Type type, string name) {
      return type.GetProperty<T>(name, BindingFlags.Default);
    }

    public static FastPropertyInfo<T> GetProperty<T>(this Type type, string name, BindingFlags flags) {
      var property = type.GetProperty(name, flags);

      if(property == null) {
        return null;
      }

      return new FastPropertyInfo<T>(property);
    }
  }

  public class FastPropertyInfo<T> {
    private PropertyInfo info;
    private Func<T, object[], object> getter;
    private Action<T, object, object[]> setter;

    public bool CanRead { get { return info.CanRead; } }
    public bool CanWrite { get { return info.CanWrite; } }

    public FastPropertyInfo(PropertyInfo info) {
      this.info = info;
      getter = CreateGetValue(info);
      setter = CreateSetValue(info);
    }

    public object GetValue(T instance, object[] index) {
      if(getter == null) {
        throw new ArgumentException("The property's get accessor is not found.");
      }

      return getter(instance, index);
    }

    public void SetValue(T instance, object value, object[] index) {
      if(setter == null) {
        throw new ArgumentException("The property's set accessor is not found.");
      }

      setter(instance, value, index);
    }

    private static Func<T, object[], object> CreateGetValue(PropertyInfo info) {
      if(!info.CanRead) {
        return null;
      }

      // info.GetValue(instance, null);
      var instanceExpression = Expression.Parameter(typeof(T), "instance");
      var indexExpression = Expression.Parameter(typeof(object[]), "index");
      var getExpression = Expression.Call(instanceExpression, info.GetGetMethod());
      var lambdaExpression = Expression.Lambda<Func<T, object[], object>>(Expression.Convert(getExpression, typeof(object)), instanceExpression, indexExpression);

      return lambdaExpression.Compile();
    }

    private static Action<T, object, object[]> CreateSetValue(PropertyInfo info) {
      if(!info.CanWrite) {
        return null;
      }

      // info.SetValue(instance, value, null);
      var valueType = info.GetSetMethod().GetParameters()[0].ParameterType;
      var instanceExpression = Expression.Parameter(typeof(T), "instance");
      var valueExpression = Expression.Parameter(valueType, "value");
      var indexExpression = Expression.Parameter(typeof(object[]), "index");
      var setExpression = Expression.Call(instanceExpression, info.GetSetMethod(), valueExpression, indexExpression);
      var lambdaExpression = Expression.Lambda<Action<T, object, object[]>>(setExpression, instanceExpression, valueExpression, indexExpression);

      return lambdaExpression.Compile();
    }
  }
}