using System;
using System.Diagnostics;
using System.Linq;

namespace BizTalkCheckmkPulse
{
    internal sealed class EventLogProbe
    {
        private readonly MonitoringOptions _options;

        public EventLogProbe(MonitoringOptions options)
        {
            _options = options;
        }

        public void Query(ProbeResult result)
        {
            result.EventLog.Since = DateTime.Now.AddMinutes(-_options.EventLogLookbackMinutes);

            try
            {
                using (var log = new EventLog("Application", "."))
                {
                    var entries = log.Entries;
                    for (var i = entries.Count - 1; i >= 0; i--)
                    {
                        var entry = entries[i];
                        if (entry.TimeGenerated < result.EventLog.Since)
                        {
                            break;
                        }

                        if (!IsRelevantSource(entry.Source))
                        {
                            continue;
                        }

                        if (entry.EntryType == EventLogEntryType.Error)
                        {
                            result.EventLog.Errors++;
                        }
                        else if (entry.EntryType == EventLogEntryType.Warning)
                        {
                            result.EventLog.Warnings++;
                        }
                    }
                }

                result.EventLog.Available = true;
            }
            catch (Exception ex)
            {
                result.EventLog.Available = false;
                result.EventLog.Failure = ex.GetType().Name + ": " + ex.Message;
            }
        }

        private bool IsRelevantSource(string source)
        {
            if (string.IsNullOrWhiteSpace(source))
            {
                return false;
            }

            return _options.EventLogSources.Any(x => source.IndexOf(x, StringComparison.OrdinalIgnoreCase) >= 0);
        }
    }
}