using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Configuration;
using System.Globalization;
using System.IO;
using System.Web.Mvc;
using System.Web.Script.Serialization;

namespace EnVisage.Code
{
    // this code was taken from https://aspnetwebstack.codeplex.com/SourceControl/latest#src/System.Web.Mvc/JsonValueProviderFactory.cs
    public class AdvancedJsonValueProviderFactory : ValueProviderFactory
    {
        private static void AddToBackingStore(EntryLimitedDictionary backingStore, string prefix, object value)
        {
            IDictionary<string, object> d = value as IDictionary<string, object>;
            if (d != null)
            {
                foreach (KeyValuePair<string, object> entry in d)
                {
                    AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
                }
                return;
            }

            IList l = value as IList;
            if (l != null)
            {
                for (int i = 0; i < l.Count; i++)
                {
                    AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
                }
                return;
            }

            // primitive
            backingStore.Add(prefix, value);
        }

        private static object GetDeserializedObject(ControllerContext controllerContext)
        {
            if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
            {
                // not JSON request
                return null;
            }

            StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
            string bodyText = reader.ReadToEnd();
            if (String.IsNullOrEmpty(bodyText))
            {
                // no JSON data
                return null;
            }

            // original code starts
            // JavaScriptSerializer serializer = new JavaScriptSerializer();
            // original code ends

            // modified code starts
            JavaScriptSerializer serializer = new JavaScriptSerializer()
            {
                // added by EN to extend original JsonValueProviderFactory class
                MaxJsonLength = GetMaxJsonLength()
            };
            // modified code ends
            object jsonData = serializer.DeserializeObject(bodyText);
            return jsonData;
        }

        public override IValueProvider GetValueProvider(ControllerContext controllerContext)
        {
            if (controllerContext == null)
            {
                throw new ArgumentNullException("controllerContext");
            }

            object jsonData = GetDeserializedObject(controllerContext);
            if (jsonData == null)
            {
                return null;
            }

            Dictionary<string, object> backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
            EntryLimitedDictionary backingStoreWrapper = new EntryLimitedDictionary(backingStore);
            AddToBackingStore(backingStoreWrapper, String.Empty, jsonData);
            return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
        }

        private static string MakeArrayKey(string prefix, int index)
        {
            return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
        }

        private static string MakePropertyKey(string prefix, string propertyName)
        {
            return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
        }

        // added by EN to extend original JsonValueProviderFactory class code starts
        private static int GetMaxJsonLength()
        {
            var maxJsonLengthDefault = (new JavaScriptSerializer()).MaxJsonLength;
            if (ConfigurationManager.AppSettings == null)
                return maxJsonLengthDefault;

            var values = ConfigurationManager.AppSettings.GetValues("MaxJsonLength");
            if (values == null || values.Length <= 0)
                return maxJsonLengthDefault;

            var maxJsonLength = 0;
            if (int.TryParse(values[0], out maxJsonLength) && maxJsonLength > 0)
                return maxJsonLength;

            return maxJsonLengthDefault;
        }
        // added by EN to extend original JsonValueProviderFactory class code ends

        private class EntryLimitedDictionary
        {
            private static int _maximumDepth = GetMaximumDepth();
            private readonly IDictionary<string, object> _innerDictionary;
            private int _itemCount = 0;

            public EntryLimitedDictionary(IDictionary<string, object> innerDictionary)
            {
                _innerDictionary = innerDictionary;
            }

            public void Add(string key, object value)
            {
                if (++_itemCount > _maximumDepth)
                {
                    throw new InvalidOperationException("Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property.");
                }

                _innerDictionary.Add(key, value);
            }

            private static int GetMaximumDepth()
            {
                NameValueCollection appSettings = ConfigurationManager.AppSettings;
                if (appSettings != null)
                {
                    string[] valueArray = appSettings.GetValues("aspnet:MaxJsonDeserializerMembers");
                    if (valueArray != null && valueArray.Length > 0)
                    {
                        int result;
                        if (Int32.TryParse(valueArray[0], out result))
                        {
                            return result;
                        }
                    }
                }

                return 1000; // Fallback default
            }
        }
    }
}