using System;
using System.Xml;
using Chernobyl.Collections.Generic.Event;

namespace Chernobyl.Reflection.Template.Xml
{
    /// <summary>
    /// An <see cref="IMember"/> in the form of a constructor that is generated 
    /// from or can be written to an XML stream.
    /// </summary>
    public class XmlConstructor : Member
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="XmlMember"/> class.
        /// </summary>
        /// <param name="services">The <see cref="IEventCollection{T}"/> instance that 
        /// takes and sets service.</param>
        /// <param name="instance">The <see cref="IInstance"/> this constructor 
        /// belongs to.</param>
        /// <param name="xmlr">The <see cref="XmlReader"/> to read the members 
        /// from.</param>
        /// <exception cref="ArgumentException">Thrown if the 
        /// <paramref name="xmlr"/> is not positioned on an
        /// <see cref="XmlNodeType"/> (see <see cref="XmlReader.NodeType"/>) of
        /// <see cref="XmlNodeType.Element"/>.</exception>
        public XmlConstructor(IEventCollection<object> services, IInstance instance, XmlReader xmlr)
            : base(services, string.Empty, instance)
        {
            if (xmlr.NodeType != XmlNodeType.Element && xmlr.NodeType != XmlNodeType.Text)
                throw new ArgumentException("Unable to extract the XML member data because " +
                "The XmlReader passed into this constructor is not positioned on " +
                "XML text or an element (i.e., xmlr.NodeType != XmlNodeType.Element || " +
                "XmlReader.NodeType != XmlNodeType.Text). Please ensure the " +
                "XmlReader is positioned correctly.");

            // if this is the Fallout Arguments element then we need to process
            // this element before we can move onto the instances defined within
            // it.
            if (xmlr.LocalName == ArgumentsName && xmlr.NamespaceURI == Fallout.NamepaceUri)
            {
                // grab all of the attributes off of the member.
                XmlAttribute.Create(services, xmlr);

                // Make sure we go past the attributes, if they exist, and drop back 
                // down on the element. After that, we'll want to move to the elements 
                // content or the next node. If the element is not empty we'll process
                // the elements content
                xmlr.MoveToElement();
                
                if (xmlr.IsEmptyElement == true)
                {
                    throw new Exception("Explicitly calling a parameterless " + 
                        "constructor is not allowed. This is done for you if " + 
                        "you do not specify a constructor.");
                }

                xmlr.Read();
            }

            Name = DefaultName;

            // read in the arguments
            foreach (IInstance component in XmlInstance.Create(services, xmlr))
                ComponentChildren.Add(component);
        }

        /// <summary>
        /// The name of this component which can be used to generate code for 
        /// this component.
        /// </summary>
        public override string CodeName
        {
            get
            {
                if (string.IsNullOrEmpty(_CodeName) == true)
                    _CodeName = "ctor";
                return _CodeName;
            }
        }

        /// <summary>
        /// The local name of the constructor arguments element.
        /// </summary>
        public const string ArgumentsName = "Arguments";

        /// <summary>
        /// The default value of the <see cref="Component.Name"/> property for
        /// <see cref="XmlConstructor"/>s.
        /// </summary>
        public const string DefaultName = ".ctor";
    }
}