FullObjectGraphTraversalStrategy.cs

//  This file is part of YamlDotNet - A .NET library for YAML.
//  Copyright (c) Antoine Aubry and contributors

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//  this software and associated documentation files (the "Software"), to deal in
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using System;
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using YamlDotNet.Core;
using YamlDotNet.Helpers;
using YamlDotNet.Serialization.Utilities;

namespace YamlDotNet.Serialization.ObjectGraphTraversalStrategies
{
    /// <summary>
    /// An implementation of <see cref="IObjectGraphTraversalStrategy"/> that traverses
    /// readable properties, collections and dictionaries.
    /// </summary>
    public class FullObjectGraphTraversalStrategy : IObjectGraphTraversalStrategy
    {
        private readonly int maxRecursion;
        private readonly ITypeInspector typeDescriptor;
        private readonly ITypeResolver typeResolver;
        private INamingConvention namingConvention;

        public FullObjectGraphTraversalStrategy(ITypeInspector typeDescriptor, ITypeResolver typeResolver, int maxRecursion, INamingConvention namingConvention)
        {
            if (maxRecursion <= 0)
            {
                throw new ArgumentOutOfRangeException("maxRecursion", maxRecursion, "maxRecursion must be greater than 1");
            }

            if (typeDescriptor == null)
            {
                throw new ArgumentNullException("typeDescriptor");
            }

            this.typeDescriptor = typeDescriptor;

            if (typeResolver == null)
            {
                throw new ArgumentNullException("typeResolver");
            }

            this.typeResolver = typeResolver;

            this.maxRecursion = maxRecursion;
            this.namingConvention = namingConvention;
        }

        void IObjectGraphTraversalStrategy.Traverse<TContext>(IObjectDescriptor graph, IObjectGraphVisitor<TContext> visitor, TContext context)
        {
            Traverse("<root>", graph, visitor, context, new Stack<ObjectPathSegment>(maxRecursion));
        }

        protected struct ObjectPathSegment
        {
            public object name;
            public IObjectDescriptor value;

            public ObjectPathSegment(object name, IObjectDescriptor value)
            {
                this.name = name;
                this.value = value;
            }
        }

        protected virtual void Traverse<TContext>(object name, IObjectDescriptor value, IObjectGraphVisitor<TContext> visitor, TContext context, Stack<ObjectPathSegment> path)
        {
            if (path.Count >= maxRecursion)
            {
                var message = new StringBuilder();
                message.AppendLine("Too much recursion when traversing the object graph.");
                message.AppendLine("The path to reach this recursion was:");

                var lines = new Stack<KeyValuePair<string, string>>(path.Count);
                var maxNameLength = 0;
                foreach (var segment in path)
                {
                    var segmentName = TypeConverter.ChangeType<string>(segment.name);
                    maxNameLength = Math.Max(maxNameLength, segmentName.Length);
                    lines.Push(new KeyValuePair<string, string>(segmentName, segment.value.Type.FullName));
                }

                foreach (var line in lines)
                {
                    message
                        .Append(" -> ")
                        .Append(line.Key.PadRight(maxNameLength))
                        .Append("  [")
                        .Append(line.Value)
                        .AppendLine("]");
                }

                throw new MaximumRecursionLevelReachedException(message.ToString());
            }

            if (!visitor.Enter(value, context))
            {
                return;
            }

            path.Push(new ObjectPathSegment(name, value));
            try
            {
                var typeCode = value.Type.GetTypeCode();
                switch (typeCode)
                {
                    case TypeCode.Boolean:
                    case TypeCode.Byte:
                    case TypeCode.Int16:
                    case TypeCode.Int32:
                    case TypeCode.Int64:
                    case TypeCode.SByte:
                    case TypeCode.UInt16:
                    case TypeCode.UInt32:
                    case TypeCode.UInt64:
                    case TypeCode.Single:
                    case TypeCode.Double:
                    case TypeCode.Decimal:
                    case TypeCode.String:
                    case TypeCode.Char:
                    case TypeCode.DateTime:
                        visitor.VisitScalar(value, context);
                        break;

                    case TypeCode.Empty:
                        throw new NotSupportedException(string.Format(CultureInfo.InvariantCulture, "TypeCode.{0} is not supported.", typeCode));

                    default:
                        if (value.IsDbNull())
                        {
                            visitor.VisitScalar(new ObjectDescriptor(null, typeof(object), typeof(object)), context);
                        }

                        if (value.Value == null || value.Type == typeof(TimeSpan))
                        {
                            visitor.VisitScalar(value, context);
                            break;
                        }

                        var underlyingType = Nullable.GetUnderlyingType(value.Type);
                        if (underlyingType != null)
                        {
                            // This is a nullable type, recursively handle it with its underlying type.
                            // Note that if it contains null, the condition above already took care of it
                            Traverse("Value", new ObjectDescriptor(value.Value, underlyingType, value.Type, value.ScalarStyle), visitor, context, path);
                        }
                        else
                        {
                            TraverseObject(value, visitor, context, path);
                        }
                        break;
                }
            }
            finally
            {
                path.Pop();
            }
        }

        protected virtual void TraverseObject<TContext>(IObjectDescriptor value, IObjectGraphVisitor<TContext> visitor, TContext context, Stack<ObjectPathSegment> path)
        {
            if (typeof(IDictionary).IsAssignableFrom(value.Type))
            {
                TraverseDictionary(value, visitor, typeof(object), typeof(object), context, path);
                return;
            }

            var genericDictionaryType = ReflectionUtility.GetImplementedGenericInterface(value.Type, typeof(IDictionary<,>));
            if (genericDictionaryType != null)
            {
                var adaptedDictionary = new GenericDictionaryToNonGenericAdapter(value.Value, genericDictionaryType);
                var genericArguments = genericDictionaryType.GetGenericArguments();
                TraverseDictionary(new ObjectDescriptor(adaptedDictionary, value.Type, value.StaticType, value.ScalarStyle), visitor, genericArguments[0], genericArguments[1], context, path);
                return;
            }

            if (typeof(IEnumerable).IsAssignableFrom(value.Type))
            {
                TraverseList(value, visitor, context, path);
                return;
            }

            TraverseProperties(value, visitor, context, path);
        }

        protected virtual void TraverseDictionary<TContext>(IObjectDescriptor dictionary, IObjectGraphVisitor<TContext> visitor, Type keyType, Type valueType, TContext context, Stack<ObjectPathSegment> path)
        {
            visitor.VisitMappingStart(dictionary, keyType, valueType, context);

            var isDynamic = dictionary.Type.FullName.Equals("System.Dynamic.ExpandoObject");
            foreach (DictionaryEntry entry in (IDictionary)dictionary.Value)
            {
                var keyValue = isDynamic ? namingConvention.Apply(entry.Key.ToString()) : entry.Key;
                var key = GetObjectDescriptor(keyValue, keyType);
                var value = GetObjectDescriptor(entry.Value, valueType);

                if (visitor.EnterMapping(key, value, context))
                {
                    var keyAsString = TypeConverter.ChangeType<string>(key);
                    Traverse(keyValue, key, visitor, context, path);
                    Traverse(keyValue, value, visitor, context, path);
                }
            }

            visitor.VisitMappingEnd(dictionary, context);
        }

        private void TraverseList<TContext>(IObjectDescriptor value, IObjectGraphVisitor<TContext> visitor, TContext context, Stack<ObjectPathSegment> path)
        {
            var enumerableType = ReflectionUtility.GetImplementedGenericInterface(value.Type, typeof(IEnumerable<>));
            var itemType = enumerableType != null ? enumerableType.GetGenericArguments()[0] : typeof(object);

            visitor.VisitSequenceStart(value, itemType, context);

            var index = 0;
            foreach (var item in (IEnumerable)value.Value)
            {
                Traverse(index, GetObjectDescriptor(item, itemType), visitor, context, path);
                ++index;
            }

            visitor.VisitSequenceEnd(value, context);
        }

        protected virtual void TraverseProperties<TContext>(IObjectDescriptor value, IObjectGraphVisitor<TContext> visitor, TContext context, Stack<ObjectPathSegment> path)
        {
            visitor.VisitMappingStart(value, typeof(string), typeof(object), context);

            foreach (var propertyDescriptor in typeDescriptor.GetProperties(value.Type, value.Value))
            {
                var propertyValue = propertyDescriptor.Read(value.Value);

                if (visitor.EnterMapping(propertyDescriptor, propertyValue, context))
                {
                    Traverse(propertyDescriptor.Name, new ObjectDescriptor(propertyDescriptor.Name, typeof(string), typeof(string)), visitor, context, path);
                    Traverse(propertyDescriptor.Name, propertyValue, visitor, context, path);
                }
            }

            visitor.VisitMappingEnd(value, context);
        }

        private IObjectDescriptor GetObjectDescriptor(object value, Type staticType)
        {
            return new ObjectDescriptor(value, typeResolver.Resolve(staticType, value), staticType);
        }
    }
}