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

namespace RhinoReminds
{
	public delegate void OnReminderListUpdateHandler(object sender, Reminder newReminder);

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

		public SortedList<DateTime, Reminder> Reminders = new SortedList<DateTime, Reminder>();

		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}");
			Reminders.Add(time, result);
			OnReminderListUpdate(this, result);
			return result;
		}

		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 teeny 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.Values)
					nextReminder.WriteToXml(xml);
				xml.WriteEndElement();

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

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

			return Reminders.Values[0];
		}

		public void DeleteReminder(Reminder nextReminder) {
			Reminders.Remove(nextReminder.Time);
		}

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

			ReminderList result = new ReminderList();
			result.nextId = int.Parse(xml.GetElementsByTagName("NextId")[0].InnerText);
			foreach (XmlNode reminderXML in xml.GetElementsByTagName("Reminders")[0].ChildNodes) {
				Reminder nextReminder = Reminder.FromXml(reminderXML);
				result.Reminders.Add(nextReminder.Time, nextReminder);
			}

			return result;
		}
	}
}