// GET BULK message handler class.
// Copyright (C) 2009-2010 Lex Li
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Generic;
using GSF.Net.Snmp.Messaging;

namespace GSF.Net.Snmp.Pipeline
{
    /// <summary>
    /// GET BULK message handler.
    /// </summary>    
    public sealed class GetBulkMessageHandler : IMessageHandler
    {
        /// <summary>
        /// Handles the specified message.
        /// </summary>
        /// <param name="context">The context.</param>
        /// <param name="store">The object store.</param>
        /// <returns></returns>
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes")]
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes")]
        public void Handle(ISnmpContext context, ObjectStore store)
        {    
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }
            
            if (store == null)
            {
                throw new ArgumentNullException(nameof(store));
            }    
            
            ISnmpPdu pdu = context.Request.Pdu();
            IList<Variable> result = new List<Variable>();
            int index = 0;
            int nonrepeaters = pdu.ErrorStatus.ToInt32();
            IList<Variable> variables = pdu.Variables;
            for (int i = 0; i < nonrepeaters; i++)
            {
                Variable v = variables[i];
                index++;
                try
                {
                    ScalarObject next = store.GetNextObject(v.Id);
                    result.Add(next == null ? new Variable(v.Id, new EndOfMibView()) : next.Variable);
                }
                catch (Exception)
                {
                    context.CopyRequest(ErrorCode.GenError, index);
                    return;
                }
            }

            for (int j = nonrepeaters; j < variables.Count; j++)
            {
                Variable v = variables[j];
                index++;
                Variable temp = v;
                int repetition = pdu.ErrorIndex.ToInt32();
                while (repetition-- > 0)
                {
                    try
                    {
                        ScalarObject next = store.GetNextObject(temp.Id);
                        if (next == null)
                        {
                            temp = new Variable(temp.Id, new EndOfMibView());
                            result.Add(temp);
                            break;
                        }

                        // TODO: how to handle write only object here?
                        result.Add(next.Variable);
                        temp = next.Variable;
                    }
                    catch (Exception)
                    {
                        context.CopyRequest(ErrorCode.GenError, index);
                        return;
                    }
                }
            }

            context.GenerateResponse(result);
        }
    }
}