//-----------------------------------------------------------------------
// <copyright file="RequestMatcher.cs" company="bedug.com">
//     Copyright © 2012 Nils Hammar. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------
/*
 * Software to access vehicle information via the OBD-II connector.
 * 
 * Copyright © 2012 Nils Hammar
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 * 
 * Alternative licensing is possible, see the licensing document.
 * 
 * The above text may not be removed or modified.
 */

namespace Protocol.OBD
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using global::SharedObjects;
    using global::SharedObjects.Misc;

    /// <summary>
    /// Request matching engine where responses
    /// are matched to an earlier request in order to improve
    /// parsing.
    /// </summary>
    public class RequestMatcher : IRequestMatcher
    {
        /// <summary>
        /// Gets the number of requests that we wait for answer on.
        /// </summary>
        public int openRequests
        {
            get
            {
                return this.requestDataList.Count;
            }
        }

        /// <summary>
        /// Request data to help with parsing.
        /// </summary>
        private IDictionary<uint, IRequestData> requestDataList = new Dictionary<uint, IRequestData>();

        /// <summary>
        /// Event logging instance.
        /// </summary>
        private ILogging iLogging;

        /// <summary>
        /// Initializes a new instance of the <see cref="RequestMatcher" /> class.
        /// </summary>
        /// <param name="iLogging">Event logging instance.</param>
        public RequestMatcher(ILogging iLogging)
        {
            this.iLogging = iLogging;
        }

        /// <summary>
        /// Set request data to help with parsing the received data in some cases.
        /// </summary>
        /// <param name="requestData">Request data to set.</param>
        /// <returns>'true' on success.</returns>
        public bool addRequestData(IRequestData requestData)
        {
            bool success = false;
            if (requestData != null)
            {
                long t1 = DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond;

                lock (this.requestDataList)
                {
                    requestData.timestamp = t1;
                    uint destAddr = 0;

                    if (requestData.destinationAddress != null)
                    {
                        destAddr = (uint)requestData.destinationAddress;
                    }

                    /*
                     * Delete old request if it exists.
                     * Shall normally only impact functional address requests.
                     */
                    if (this.requestDataList.ContainsKey(destAddr))
                    {
                        this.requestDataList.Remove(destAddr);
                    }

                    this.requestDataList.Add(destAddr, requestData);

                    success = true;
                }
            }

            return success;
        }

        /// <summary>
        /// Check if address already is listed.
        /// <para>
        /// This method will also set 'false' if the time waiting for answer exceeds 2 seconds.
        /// </para>
        /// </summary>
        /// <param name="address">Address to check.</param>
        /// <returns>'true' if waiting for answer from ECU.</returns>
        public bool hasListedAddress(uint address)
        {
            bool match = false;

            lock (this.requestDataList)
            {
                match = this.requestDataList.ContainsKey(address);
                if (match)
                {
                    IRequestData msg = this.requestDataList[address];
                    if (((DateTime.Now.Ticks - msg.txTimestamp) / TimeSpan.TicksPerMillisecond) > 2000)
                    {
                        this.requestDataList.Remove(address);
                        match = false;
                    }
                }
            }

            return match;
        }

        /// <summary>
        /// Find a matching request for the data we got.
        /// </summary>
        /// <param name="destinationAddress">Destination address to send to.</param>
        /// <param name="mode">Current mode.</param>
        /// <param name="payload">Payload data.</param>
        /// <returns>Matched request data.</returns>
        public IRequestData getMatchingRequest(uint? destinationAddress, byte mode, byte[] payload)
        {
            IRequestData rqd = null;
            int expectedPid = 0;
            uint destAddr = (destinationAddress != null) ? (uint)destinationAddress : 0;

            /*
             * Look up a matching request, requests with address 0 are functional requests
             * that can return multiple answers so we never delete those but assume it's the
             * last functional request that got answered. It's also a last resort, even if it
             * may be wrong in some hopefully rare cases.
             */
            lock (this.requestDataList)
            {
                if (this.requestDataList.Count > 0)
                {
                    if (this.requestDataList.ContainsKey(destAddr))
                    {
                        rqd = this.requestDataList[destAddr];

                        if (destAddr != 0)
                        {
                            this.requestDataList.Remove(destAddr);
                        }
                    }
                    else
                    {
                        if (this.requestDataList.ContainsKey(0))
                        {
                            rqd = this.requestDataList[0];
                        }
                    }
                }
            }

            if (rqd == null)
            {
                string str = string.Empty;
                if (payload != null)
                {
                    foreach (byte b1 in payload)
                    {
                        if (!string.IsNullOrEmpty(str))
                        {
                            str += " ";
                        }

                        str += b1.ToString("x2");
                    }
                }

                this.iLogging.appendText("No matching request for mode_int=0x" + mode.ToString("x2") + ", expectedPid=0x" + expectedPid.ToString("x2") + ", data=[" + str + "]\r\n");
            }

            return rqd;
        }
    }
}