namespace MonoRail.ContactForm.Controllers
{
    using System;
    using System.Reflection;
    using Castle.MonoRail.Framework;

    [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
    public class DefaultValueAttribute : Attribute, IParameterBinder
    {
        private readonly object value;
        public DefaultValueAttribute(object value)
        {
            this.value = value;
        }

        public int CalculateParamPoints(IEngineContext context, IController controller, IControllerContext controllerContext, ParameterInfo parameterInfo)
        {
            var token = context.Request[parameterInfo.Name];
            if (CanConvert(parameterInfo.ParameterType, token))
                return 10;
            return 0;
        }
        
        private static bool CanConvert(Type targetType, string token)
        {
            if (token == null)
                return false;

            try
            {
                Convert.ChangeType(token, targetType);
                return true;
            }
            catch (FormatException)
            {
                return false;
            }
        }

        public object Bind(IEngineContext context, IController controller, IControllerContext controllerContext, ParameterInfo parameterInfo)
        {
            string token = context.Request[parameterInfo.Name];
            Type type = parameterInfo.ParameterType;
            if (CanConvert(type, token))
                return Convert.ChangeType(token, type);
            return value;
        }
    }
}