using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Implab.Diagnostics {
    public abstract class ListenerBase : ServiceLocator, ILogWriter<object>, ILogWriter<TraceEvent> {

        readonly Dictionary<object, Action> m_subscriptions = new Dictionary<object, Action>();

        protected ListenerBase() {
            Register(this);
        }

        public void Subscribe(Type eventType) {
            if (eventType == null)
                throw new ArgumentNullException("eventType");
            GetType().GetMethod("Subscribe", new Type[0]).MakeGenericMethod(eventType).Invoke(this, null);
        }

        public void Subscribe<TEvent>() {
            Subscribe<TEvent>(LogChannel<TEvent>.Default);
        }

        public void Subscribe<TEvent>(LogChannel<TEvent> channel) {
            if (channel == null)
                throw new ArgumentNullException("channel");

            lock (m_subscriptions) {
                AssertNotDisposed();
                if (m_subscriptions.ContainsKey(channel))
                    return;

                var writer = GetService<ILogWriter<TEvent>>();

                EventHandler<LogEventArgs<TEvent>> handler = (sender, args) => writer.Write(args,args.Value);

                channel.Events += handler;

                Action unsubscribe = () => {
                    channel.Events -= handler;
                };

                m_subscriptions.Add(channel, unsubscribe);
            }
        }

        public void Unsubscribe<TEvent>(LogChannel<TEvent> channel) {
            if (channel == null)
                throw new ArgumentNullException("channel");

            lock (m_subscriptions) {
                Action subscription;
                if (m_subscriptions.TryGetValue(channel, out subscription)) {
                    subscription();
                    m_subscriptions.Remove(channel);
                }
            }
        }

        public void UnsubscribeAll() {
            lock (m_subscriptions) {
                foreach (var subscription in m_subscriptions.Values)
                    subscription();
                m_subscriptions.Clear();
            }
        }

        #region ILogWriter implementation
        public abstract void Write(LogEventArgs args, object entry);
        #endregion

        #region ILogWriter implementation
        public virtual void Write(LogEventArgs args, TraceEvent entry) {
            Write(args, (object)entry);
        }
        #endregion


        protected override void Dispose(bool disposing) {
            base.Dispose(disposing);
            if (disposing) {
                UnsubscribeAll();
            }
        }
    }
}