using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Xml.Linq;

namespace ChadSoft.Edificator
{
    internal class XmlWisdomHistory : WisdomHistoryBase
    {
        private const string HistoryFilename = "history.xml";

        private readonly XElement _historyElement;

        public XmlWisdomHistory()
        {
            _historyElement = XElement.Load(HistoryFilename);
            Debug.WriteLine("Loaded history file " + HistoryFilename);
        }

        public override bool HasBeenSentRecently(WisdomBit wisdom)
        {
            string url = GetUrl(wisdom);

            IEnumerable<string> sentHistoryTimeStamps =
                from history in _historyElement.Descendants("history")
                where url.Equals(history.Attribute("url").Value, StringComparison.OrdinalIgnoreCase)
                let timestamp = history.Attribute("timestamp")
                where timestamp != null
                orderby timestamp.Value descending
                select timestamp.Value;

            if(sentHistoryTimeStamps.Count() == 0)
            {
                Debug.WriteLine(string.Format("Wisdom Url {0} has never been sent before.", url));
                return false;
            }
            string lastDateString = sentHistoryTimeStamps.OrderByDescending(x => x).First();
            DateTime lastSentDate = DateTime.Parse(lastDateString);
            TimeSpan timeSinceLastSent = DateTime.Now - lastSentDate;

            bool hasBeenSentRecently = timeSinceLastSent < RecentlySentTimespan;

            Debug.WriteLine(string.Format("Wisdom Url {0} has been sent recently: [{1}]\tLast Sent: {2}\tTime Since Last Sent: {3}", 
                                          url, hasBeenSentRecently, lastSentDate, timeSinceLastSent));

            return hasBeenSentRecently;
        }

        public override void WisdomSent(WisdomBit wisdom)
        {
            string elementText = string.Format("<history url='{0}' timestamp='{1:s}' />", GetUrl(wisdom), DateTime.Now);
            XElement newHistoryElement = XElement.Parse(elementText);
            _historyElement.Add(newHistoryElement);
            _historyElement.Save(HistoryFilename);

            Debug.WriteLine("Wisdom saved to history: " + elementText);
        }

        private static string GetUrl(WisdomBit wisdom)
        {
            return wisdom.Uri.AbsoluteUri;
        }
    }
}