using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Timers;
using SafeMobileLib;

namespace MotoRepeater
{
    class SMSConfirm
    {
        private static Boolean debug = false;
        private static Boolean listFilled = false;
        private static Boolean timerInitialized = false;
        private static Dictionary<int, SeqAndTime> toBeConfirmed = new Dictionary<int, SeqAndTime>();
        private static List<int> availableIDs = new List<int>();
        private static int recycleInterval = 60; //seconds
        private static int noACKindex = 1;
        static Timer recycleTimer;
        
        private class SeqAndTime 
        {
            public String seq_id;
            public double timeStamp;

            public SeqAndTime(String seq, double tStamp)
            {
                seq_id = seq;
                timeStamp = tStamp;
            }
        }

        [MethodImpl(MethodImplOptions.Synchronized)]
        public static void initializeTimer()
        {
            if (!timerInitialized)
            {
                recycleTimer = new Timer(recycleInterval * 1000);
                recycleTimer.Elapsed += new ElapsedEventHandler(recycleTimer_Elapsed);
                recycleTimer.Enabled = true;
                timerInitialized = true;
            }
        }

        private static void recycleTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            recycleOldConfirmations();
        }

        [MethodImpl(MethodImplOptions.Synchronized)]
        public static void fillList()
        {
            if (!listFilled)
            {
                for (int i = 1; i < 128; i++)
                {
                    availableIDs.Add(i);
                }
                listFilled = true;
            }
        }

        [MethodImpl(MethodImplOptions.Synchronized)]
        public static void recycleOldConfirmations()
        {
            if (debug)
            {
                Utils.WriteLine("Recycling confirmations at " + DateTime.Now.ToString());
            }
            Dictionary<int, SeqAndTime> tempToBeConfirmed = new Dictionary<int, SeqAndTime>();
            double currentTime = (DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds;
            foreach (int index in toBeConfirmed.Keys)
            {
                if (toBeConfirmed[index].timeStamp < currentTime - recycleInterval)
                {
                    availableIDs.Add(index);
                    if (debug)
                    {
                        Utils.WriteLine("Removed " + toBeConfirmed[index].seq_id + " from the confirmation requests list");
                    }
                }
                else
                {
                    tempToBeConfirmed.Add(index, toBeConfirmed[index]);
                }
            }
            toBeConfirmed = tempToBeConfirmed;
            if (debug)
            {
                Utils.WriteLine("There are " + toBeConfirmed.Keys.Count + " messages waiting for confirmation,");
                Utils.WriteLine("and " + availableIDs.Count + " available confirmations left");
            }
        }

        [MethodImpl(MethodImplOptions.Synchronized)]
        public static int addToConfirmationQueue(String seq_idFromSD)
        {
            if (availableIDs.Count > 0)
            {
                double timeStamp = (DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds;
                SeqAndTime sT = new SeqAndTime(seq_idFromSD, timeStamp);
                int index = (int)availableIDs[0];
                availableIDs.RemoveAt(0);
                if (debug)
                {
                    Utils.WriteLine("Removed from availableIDs, remaining " + availableIDs.Count);
                }
                toBeConfirmed.Add(index, sT);
                return index;                
            }
            else
            {
                return -1;
            }
        }

        [MethodImpl(MethodImplOptions.Synchronized)]
        public static String getFromConfirmationQueue(int index)
        {
            String toReturn = "";
            if (toBeConfirmed.ContainsKey(index))
            {
                toReturn = toBeConfirmed[index].seq_id;
                toBeConfirmed.Remove(index);
                availableIDs.Add(index);                
                if (debug)
                {
                    Utils.WriteLine("Confirmed message with key " + index + ", removed from hashtable and added to availableIs");
                    Utils.WriteLine("There are " + availableIDs.Count + " available confirmations left");
                }
                return toReturn;
            }
            else
            {
                return "0.0";
            }
        }
    }
}