using System;
using System.Collections.Generic;
using System.Collections.Concurrent;

namespace RoboidControl {

    /// <summary>
    /// A participant is a device which manages things.
    /// </summary>
    /// It can communicate with other participant to synchronise the state of things.
    /// This class is used to register the things the participant is managing.
    /// It also maintains the communcation information to contact the participant.
    /// It is used as a basis for the local participant, but also as a reference to remote participants.
    public class Participant {
        /// <summary>
        /// Create a new participant with the given communcation info
        /// </summary>
        /// <param name="ipAddress">The IP address of the participant</param>
        /// <param name="port">The UDP port of the participant</param>
        public Participant(string ipAddress, int port) {
            this.ipAddress = ipAddress;
            this.port = port;
        }

        /// <summary>
        /// The Ip Address of a participant. When the participant is local, this contains 0.0.0.0
        /// </summary>
        public string ipAddress = "0.0.0.0";
        /// <summary>
        /// The port number for UDP communication with the participant. This is 0 for isolated participants.
        /// </summary>
        public int port = 0;

        /// <summary>
        /// he network Id to identify the participant
        /// </summary>
        public byte networkId = 0;

        /// <summary>
        /// The things managed by this participant
        /// </summary>
        public readonly List<Thing> things = new();

        /// <summary>
        /// Get the thing with the given properties
        /// </summary>
        /// <param name="thingId">The ID of the thing</param>
        /// <returns>The thing when it is found, null in other cases.</returns>
        public Thing Get(byte thingId) {
            Thing thing = things.Find(aThing => aThing.id == thingId);
            //Thing thing = things.Find(aThing => Thing.IsThing(aThing, networkId, thingId));
            // if (thing == null)
            //     Console.WriteLine($"Could not find thing {ipAddress}:{port}[{networkId}/{thingId}]");
            return thing;
        }

        /// <summary>
        /// Add a new thing for this participant
        /// </summary>
        /// <param name="thing">The thing to add</param>
        /// <param name="checkId">If true, the thing.id is regenerated if it is zero
        public void Add(Thing thing, bool checkId = true) {
            if (checkId && thing.id == 0) {
                thing.id = (byte)(this.things.Count + 1);
                this.things.Add(thing);
            }
            else {
                Thing foundThing = Get(thing.id);
                if (foundThing == null)
                    this.things.Add(thing);
            }
        }

        /// <summary>
        /// Remove a thing for this participant
        /// </summary>
        /// <param name="thing">The thing to remove</param>
        public void Remove(Thing thing) {
            this.things.Remove(thing);
        }

#region Update

        /// <summary>
        /// Update all things for this participant
        /// </summary>
        /// <param name="currentTimeMS">The current time in milliseconds (optional)</param>
        public virtual void Update(ulong currentTimeMS = 0) {
            int n = this.things.Count;
            for (int ix = 0; ix < n; ix++) {
                Thing thing = this.things[ix];
                if (thing != null)
                    thing.Update(currentTimeMS, true);
            }
        }

        public class UpdateEvent {
            public int messageId; // see the communication messages
            public Thing thing;
            public Participant participant;
        }
        public ConcurrentQueue<UpdateEvent> updateQueue = new();

#endregion Update

        /// <summary>
        /// The collection of known participants.
        /// </summary>
        public readonly static List<Participant> participants = new();

        /// <summary>
        /// Retrieve a participant using ip address and port number
        /// </summary>
        /// <param name="ipAddress">The ip address of the participant</param>
        /// <param name="port">The port number used to send messages to the participant</param>
        /// <returns>The participant or null if it is not found.</returns>
        public static Participant GetParticipant(string ipAddress, int port) {
            //Console.WriteLine($"Get Participant {ipAddress}:{port}");
            foreach (Participant participant in Participant.participants) {
                if (participant.ipAddress == ipAddress && participant.port == port)
                    return participant;
            }
            return null;
        }
        /// <summary>
        /// Retrieve a participant using a network ID
        /// </summary>
        /// <param name="networkId">The network ID of the participant</param>
        /// <returns>The participant or null if it is not found.</returns>
        public static Participant GetParticipant(int networkId) {
            //Console.WriteLine($"Get Participant [networkId]");
            foreach (Participant participant in Participant.participants) {
                if (participant.networkId == networkId)
                    return participant;
            }
            return null;
        }

        /// <summary>
        /// Add a new participant to the collection of participants
        /// </summary>
        /// <param name="ipAddress">The IP address of the participant</param>
        /// <param name="port">The port used to send messages to this participant</param>
        /// <returns>The added participant</returns>
        public static Participant AddParticipant(string ipAddress, int port) {
            Console.WriteLine($"New Participant {ipAddress}:{port}");
            Participant participant = new(ipAddress, port) {
                networkId = (byte)(Participant.participants.Count + 1)
            };
            Participant.participants.Add(participant);
            return participant;
        }
        /// <summary>
        /// Add a new participant to the collection of participants
        /// </summary>
        /// <param name="participant">The participant to add</param>
        /// <note>This function only adds the participant if it is not yet in the collection</note>
        public static void AddParticipant(Participant participant) {
            Participant foundParticipant = Participant.GetParticipant(participant.networkId);
            if (foundParticipant == null)
                Participant.participants.Add(participant);
        }

    }

}