namespace System.Web.Mvc {
    using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.Globalization;
    using System.IO;
    using System.Web.Script.Serialization;

    public sealed class JsonValueProviderFactory : ValueProviderFactory {

        private static void AddToBackingStore(Dictionary<string, object> 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[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;
            }

            JavaScriptSerializer serializer = new JavaScriptSerializer();
            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);
            AddToBackingStore(backingStore, 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;
        }
    }
}