EnVisageOnline/Main/Source/jQuery.DataTables.Mvc/JQueryDataTablesModelBinder.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Web.Mvc;

namespace jQuery.DataTables.Mvc
{
    public class JQueryDataTablesModelBinder : IModelBinder
    {
        #region Private Variables (Request Keys)

        private const string iDisplayStartKey = "iDisplayStart";
        private const string iDisplayLengthKey = "iDisplayLength";
        private const string iColumnsKey = "iColumns";
        private const string sSearchKey = "sSearch";
        private const string bEscapeRegexKey = "bRegex";
        private const string bSortable_Key = "bSortable_";
        private const string bSearchable_Key = "bSearchable_";
        private const string sSearch_Key = "sSearch_";
        private const string bEscapeRegex_Key = "bRegex_";
        private const string iSortingColsKey = "iSortingCols";
        private const string iSortCol_Key = "iSortCol_";
        private const string sSortDir_Key = "sSortDir_";
        private const string sEchoKey = "sEcho";
        private const string mDataProp_Key = "mDataProp_";

        private ModelBindingContext _bindingContext;

        #endregion

        #region IModelBinder Members

        public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            if (bindingContext == null)
            {
                throw new ArgumentNullException("bindingContext");
            }
            _bindingContext = bindingContext;

            //Bind Model
            var dataTablesRequest = new JQueryDataTablesModel();
            dataTablesRequest.sEcho = GetA<int>(sEchoKey);
            if (dataTablesRequest.sEcho <= 0)
            {
                throw new InvalidOperationException("Expected the request to have a sEcho value greater than 0");
            }

            dataTablesRequest.iColumns = GetA<int>(iColumnsKey);
            dataTablesRequest.bRegex = GetA<bool>(bEscapeRegexKey);
            dataTablesRequest.bRegex_ = GetAList<bool>(bEscapeRegex_Key);
            dataTablesRequest.bSearchable_ = GetAList<bool>(bSearchable_Key);
            dataTablesRequest.bSortable_ = GetAList<bool>(bSortable_Key);
            dataTablesRequest.iDisplayLength = GetA<int>(iDisplayLengthKey);
            dataTablesRequest.iDisplayStart = GetA<int>(iDisplayStartKey);
            dataTablesRequest.iSortingCols = GetANullableValue<int>(iSortingColsKey);

            if (dataTablesRequest.iSortingCols.HasValue)
            {
                dataTablesRequest.iSortCol_ = GetAList<int>(iSortCol_Key);
                dataTablesRequest.sSortDir_ = GetStringList(sSortDir_Key);

                if (dataTablesRequest.iSortingCols.Value 
                    != dataTablesRequest.iSortCol_.Count)
                {
                    throw new InvalidOperationException(string.Format("Amount of items contained in iSortCol_ {0} do not match the amount specified in iSortingCols which is {1}",
                        dataTablesRequest.iSortCol_.Count, dataTablesRequest.iSortingCols.Value));
                }

                if (dataTablesRequest.iSortingCols.Value
                    != dataTablesRequest.sSortDir_.Count)
                {
                    throw new InvalidOperationException(string.Format("Amount of items contained in sSortDir_ {0} do not match the amount specified in iSortingCols which is {1}",
                        dataTablesRequest.sSortDir_.Count, dataTablesRequest.iSortingCols.Value));
                }
            }
            dataTablesRequest.sSearch = GetString(sSearchKey);
            dataTablesRequest.sSearch_ = GetStringList(sSearch_Key);
            dataTablesRequest.mDataProp_ = GetStringList(mDataProp_Key);

            return dataTablesRequest;
        }

        #endregion

        #region Methods

        /// <summary>
        /// Retrieves an IList of strings from the ModelBindingContext based on the key provided.
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        private ReadOnlyCollection<string> GetStringList(string key)
        {
            var list = new List<string>();
            bool hasMore = true;
            int i = 0;
            while(hasMore)
            {
                var newKey = (key + i.ToString());

                // No need to use a prefix since data tables will not prefix the request names        
                var valueResult = _bindingContext.ValueProvider.GetValue(newKey);

                if (valueResult == null)
                {
                    // If valueResult is still null then we know the value is not in the ModelBindingContext
                    // cease execution of this forloop
                    hasMore = false;
                    continue;
                }

                list.Add((string)valueResult.ConvertTo(typeof(string)));

                i++;
            }

            return list.AsReadOnly();
        }

        private ReadOnlyCollection<T> GetAList<T>(string key) where T : struct
        {
            var list = new List<T>();
            bool hasMore = true;
            int i = 0;
            while (hasMore)
            {
                var newKey = (key + i.ToString());
       
                var valueResult = _bindingContext.ValueProvider.GetValue(newKey);

                if (valueResult == null)
                {
                    // If valueResult is still null then we know the value is not in the ModelBindingContext
                    // cease execution of this forloop
                    hasMore = false;
                    continue;
                }

                list.Add((T)valueResult.ConvertTo(typeof(T)));
                i++;
            }

            return list.AsReadOnly();
        }

        /// <summary>
        /// Retrieves a string from the ModelBindingContext based on the key provided.
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        private string GetString(string key)
        {       
            var valueResult = _bindingContext.ValueProvider.GetValue(key);

            if (valueResult == null)
            {
                return null;
            }

            return (string)valueResult.ConvertTo(typeof(string));
        }

        private T GetA<T>(string key) where T : struct
        {       
            var valueResult = _bindingContext.ValueProvider.GetValue(key);

            if (valueResult == null)
            {
                return new T();
            }

            return (T)valueResult.ConvertTo(typeof(T));
        }

        private T? GetANullableValue<T>(string key) where T : struct
        {        
            var valueResult = _bindingContext.ValueProvider.GetValue(key);

            if (valueResult == null)
            {
                return null;
            }

            return (T?)valueResult.ConvertTo(typeof(T));
        }

        #endregion
    }
}