using System;
using System.Linq.Expressions;

namespace DynamicExpresso
{
	/// <summary>
	/// An expression parameter. This class is thread safe.
	/// </summary>
	public class Parameter
	{
		public Parameter(string name, object value)
		{
			if (value == null)
				throw new ArgumentNullException("value");

			Name = name;
			Type = value.GetType();
			Value = value;

			Expression = System.Linq.Expressions.Expression.Parameter(Type, name);
		}

		public Parameter(ParameterExpression parameterExpression)
		{
			Name = parameterExpression.Name;
			Type = parameterExpression.Type;
			Value = null;

			Expression = parameterExpression;
		}

		public Parameter(string name, Type type, object value = null)
		{
			Name = name;
			Type = type;
			Value = value;

			Expression = System.Linq.Expressions.Expression.Parameter(type, name);
		}

		public static Parameter Create<T>(string name, T value)
		{
			return new Parameter(name, typeof(T), value);
		}

		public string Name { get; private set; }
		public Type Type { get; private set; }
		public object Value { get; private set; }

		public ParameterExpression Expression { get; private set; }
	}

	/// <summary>
	/// Parameter with its position in the expression.
	/// </summary>
	internal class ParameterWithPosition : Parameter
	{
		public ParameterWithPosition(int pos, string name, Type type)
			: base(name, type)
		{
			Position = pos;
		}

		public int Position { get; }
	}
}