namespace Insights
{
    using System.Configuration;
    using System.Linq;
    using System.Reflection;
    using Microsoft.ApplicationInsights.Channel;
    using Microsoft.ApplicationInsights.Extensibility;

    /// <summary>
    /// Version TelemetryInitializer
    /// </summary>
    public class VersionTelemetryInitializer : ITelemetryInitializer
    {
        private static string version = string.Empty;
        private static string tags = ConfigurationManager.AppSettings["InstrumentationTags"];

        /// <summary>
        /// Initializes properties of the specified 
        /// <see cref="T:Microsoft.ApplicationInsights.Channel.ITelemetry" /> object.
        /// </summary>
        /// <param name="telemetry">the telemetry channel</param>
        public void Initialize(ITelemetry telemetry)
        {
            // Application Version 
            telemetry.Context.Component.Version = VersionTelemetryInitializer.version;
            // Environment Tags 
            telemetry.Context.Properties["tags"] = VersionTelemetryInitializer.tags;
        }

        /// <summary>
        /// Adds the VersionTelemetryInitializer to Microsoft.ApplicationInsights
        /// </summary>
        public static void Configure(Assembly assembly)
        {
            VersionTelemetryInitializer.version = assembly.GetName().Version.ToString();

            if (ConfigurationManager.AppSettings.AllKeys.Contains("InstrumentationKey") && !string.IsNullOrEmpty(ConfigurationManager.AppSettings["InstrumentationKey"]))
            {
                Microsoft.ApplicationInsights.Extensibility.TelemetryConfiguration.Active.TelemetryInitializers
                    .Add(new VersionTelemetryInitializer());

                Microsoft.ApplicationInsights.Extensibility.TelemetryConfiguration.Active.InstrumentationKey =
                    ConfigurationManager.AppSettings["InstrumentationKey"];
            }
            else
            {
                TelemetryConfiguration.Active.DisableTelemetry = true;
            }
        }
    }
}