using System;
using System.ComponentModel;
using System.Reflection;
using System.Web;
namespace Examples.WebParams
	[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple=false, Inherited=true)]
	public class WebParameterAttribute : Attribute
	{
		string _default;
		string _name;
		bool _isRequired;
		bool _isDefaultForInvalid;
		int _maxLength = -1;
		int _minLength = -1;
		public WebParameterAttribute()
		{
		}
		public WebParameterAttribute(string paramName)
		{
			_name = paramName;
		}
		public string ParameterName
		{
			get{	return _name;	}
			set{	_name=value;	}
		}
		public string DefaultValue
		{
			get{	return _default	;	}
			set{	_default=value	;	}
		}
		public bool IsRequired
		{
			get{	return _isRequired;	}
			set{	_isRequired=value;	}
		}
		public bool IsDefaultUsedForInvalid
		{
			get{	return _isDefaultForInvalid;	}
			set{	_isDefaultForInvalid=value;	}
		}
		public int MaxLength
		{
			get { return _maxLength; }
			set { _maxLength = value; }
		}
		protected virtual string GetValue(string paramName, System.Web.HttpRequest request)
		{
			if (request.HttpMethod.ToLower()=="post")
				return request.Form[paramName];
			else
				return request.QueryString[paramName];
		}
		public static void SetValues(object target, System.Web.HttpRequest request)
		{
			System.Type type = target.GetType();
			FieldInfo[] fields = type.GetFields(BindingFlags.Instance | BindingFlags.Public);
			PropertyInfo[] properties = type.GetProperties(BindingFlags.Instance | BindingFlags.Public);
			MemberInfo[] members = new MemberInfo[fields.Length + properties.Length];
			fields.CopyTo(members, 0);
			properties.CopyTo(members, fields.Length);
			for(int f=0;f0)
				{
					if (member.MemberType==MemberTypes.Property)
					{
						ParameterInfo[] ps = ((PropertyInfo)member).GetIndexParameters();
						if (ps!=null && ps.Length>0)
							throw new NotSupportedException("Cannot apply WebParameterAttribute to indexed property");
					}
					attrib = attribs[0];
					paramName = (attrib.ParameterName!=null) ? attrib.ParameterName : member.Name;
					paramValue = attrib.GetValue(paramName, request);
					usingDefault = false;
					if (paramValue == null)
					{
						if (attrib.DefaultValue!=null)
						{
							paramValue = attrib.DefaultValue;
							usingDefault = true;
						}
						else if (!attrib.IsRequired)
							return;	// Just skip the member
						else
							throw new Exception("Missing required parameter");
					}
					if(attrib.MaxLength >= 0 && paramValue.Length > attrib.MaxLength)
						throw new Exception(string.Format("parametr more then {0} symbols", attrib.MaxLength));
					
					converter=TypeDescriptor.GetConverter(GetMemberUnderlyingType(member));
					if (converter==null || !converter.CanConvertFrom(paramValue.GetType()))
						throw new Exception(String.Format("Could not convert from {0}", paramValue.GetType()));
					try
					{
						typedValue=converter.ConvertFrom(paramValue);
						SetMemberValue(member, target, typedValue);
					}
					catch
					{
						if (!usingDefault && attrib.IsDefaultUsedForInvalid && attrib.DefaultValue!=null)
						{
							typedValue=converter.ConvertFrom(attrib.DefaultValue);
							SetMemberValue(member, target, typedValue);
						}
						else
							throw;
					}
				}
			}
			catch(Exception err)
			{
				throw new ApplicationException("Property/field {0} could not be set from request - " + err.Message, err);
			}
		}
		private static void SetMemberValue(MemberInfo member, object target, object value)
		{
			switch(member.MemberType)
			{
				case MemberTypes.Field:
					((FieldInfo)member).SetValue(target, value);
					break;
				case MemberTypes.Property:
					((PropertyInfo)member).SetValue(target, value, new Object[0]);
					break;
			}
		}
		private static Type GetMemberUnderlyingType(MemberInfo member)
		{
			switch(member.MemberType)
			{
				case MemberTypes.Field:
					return ((FieldInfo)member).FieldType;
				case MemberTypes.Property:
					return ((PropertyInfo)member).PropertyType;
				default:
					throw new ArgumentException("Expected a FieldInfo or PropertyInfo", "member");
			}
		}
	}