// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.Diagnostics.CodeAnalysis;
namespace System.Xaml
{
    [SuppressMessage(
        "Microsoft.Design",
        "CA1063:ImplementIDisposableCorrectly",
        Justification = @"This API has already shipped and in order to ensure compat for the
        initial .NET Core 3 release, this won't be fixed. It could be addressed at a later time.")]
    public abstract class XamlReader: IDisposable
    {
        public abstract bool Read();
        public abstract XamlNodeType NodeType { get; }
        public abstract bool IsEof { get; }
 
        public abstract NamespaceDeclaration Namespace { get; }
        public abstract XamlType Type { get; }
        public abstract object Value { get; }
        public abstract XamlMember Member { get; }
 
        public abstract XamlSchemaContext SchemaContext { get; }
 
        public virtual void Skip()
        {
            switch(NodeType)
            {
            case XamlNodeType.NamespaceDeclaration:
            case XamlNodeType.Value:
            case XamlNodeType.EndObject:
            case XamlNodeType.EndMember:
            case XamlNodeType.None:
                break;
 
            case XamlNodeType.StartObject:
                SkipFromTo(XamlNodeType.StartObject, XamlNodeType.EndObject);
                break;
 
            case XamlNodeType.StartMember:
                SkipFromTo(XamlNodeType.StartMember, XamlNodeType.EndMember);
                break;
            }
            Read();
        }
 
        #region IDisposable
 
        // See Framework Design Guidelines, pp. 248-260.
        
        void IDisposable.Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
 
        protected bool IsDisposed { get; private set; }
 
        protected virtual void Dispose(bool disposing)
        {
            IsDisposed = true;  // must call the base class to get IsDisposed == true;
        }
 
        public void Close()
        {
            ((IDisposable)this).Dispose();
        }
 
        #endregion
 
        public virtual XamlReader ReadSubtree()
        {
            return new XamlSubreader(this);
        }
 
        // ------ Private methods -------
 
        private void SkipFromTo(XamlNodeType startNodeType, XamlNodeType endNodeType)
        {
#if DEBUG
            if(NodeType != startNodeType)
            {
                throw new XamlInternalException("SkipFromTo() called incorrectly");
            }
#endif
            int depth = 1;
            while (depth > 0)
            {
                Read();
                XamlNodeType nodeType = NodeType;
                if (nodeType == startNodeType)
                {
                    depth += 1;
                }
                else if (nodeType == endNodeType)
                {
                    depth -= 1;
                }
            }
        }
    }
}