using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml;
using S22.Xmpp;

namespace RhinoReminds
{
	public class ReminderListUpdateEventArgs : EventArgs {  }
	public delegate void OnReminderListUpdateHandler(object sender, ReminderListUpdateEventArgs newReminder);

	public class ReminderList
	{
		private int nextId = 0;
		private readonly object saveLock = new object();

		public SortedSet<Reminder> Reminders = new SortedSet<Reminder>(new CompareReminders());

		public event OnReminderListUpdateHandler OnReminderListUpdate;


		public ReminderList()
		{

		}


		public Reminder CreateReminder(Jid inJid, DateTime time, string message)
		{
			Reminder result = new Reminder(nextId++, $"{inJid.Node}@{inJid.Domain}", time, message);
			Console.WriteLine($"[Rhino/ReminderList] Created reminder {result}");
			while (Reminders.Contains(result))
				result.TweakTime();

			Reminders.Add(result);
			OnReminderListUpdate(this, new ReminderListUpdateEventArgs());
			return result;
		}

		public Reminder GetNextReminder() {
			if (Reminders.Count == 0)
				return null;

			return Reminders.Min;
		}

		public Reminder GetById(int targetId) {
			return Reminders.First((Reminder nextReminder) => nextReminder.Id == targetId);
		}

		public void DeleteReminder(Reminder nextReminder) {
			if (!Reminders.Remove(nextReminder))
				throw new ApplicationException($"Error: Failed to remove the reminder {nextReminder} from the list!");

			OnReminderListUpdate(this, new ReminderListUpdateEventArgs());
		}


		#region Persistence

		public void Save(string filename)
		{
			// Make sure that the reminder thread doesn't try to save the reminders at the exact same time
			// we receive a request for a new reminder
			lock (saveLock)
			{ // FUTURE: We could go lockless here with some work, but it's not worth it for the teensy chance & low overhead 
				XmlWriter xml = XmlWriter.Create(
					filename,
					new XmlWriterSettings() { Indent = true }
				);

				xml.WriteStartDocument();
				xml.WriteStartElement("ReminderList");

				xml.WriteElementString("NextId", nextId.ToString());

				xml.WriteStartElement("Reminders");
				foreach (Reminder nextReminder in Reminders)
					nextReminder.WriteToXml(xml);
				xml.WriteEndElement();

				xml.WriteEndElement();
				xml.WriteEndDocument();
				xml.Close();
			}
		}

		public static ReminderList FromXmlFile(string filepath)
		{
			XmlDocument xml = new XmlDocument();
			xml.Load(filepath);

			ReminderList result = new ReminderList() {
				nextId = int.Parse(xml.GetElementsByTagName("NextId")[0].InnerText)
			};

			foreach (XmlNode reminderXML in xml.GetElementsByTagName("Reminders")[0].ChildNodes) {
				Reminder nextReminder = Reminder.FromXml(reminderXML);
				while (result.Reminders.Contains(nextReminder))
					nextReminder.TweakTime();
				result.Reminders.Add(nextReminder);
			}

			return result;
		}

		#endregion
	}
}