// =============================================================================
// B28 English — RTD real-time-data server (MyRtdServer.cs)
// B28 英文版 — RTD 实时数据服务器（MyRtdServer.cs）
// =============================================================================
//
// Key points:
// 1. MUST inherit ExcelDna.Integration.Rtd.ExcelRtdServer
// 2. Must override (all mandatory):
//      - protected override bool ServerStart()       parameter-less
//      - protected override object ConnectData(Topic topic, IList<string> topicInfo, ref bool newValues)
//      - protected override void DisconnectData(Topic topic)
//    - GetActiveTopics() is a PROTECTED instance method (not override) — use it when pushing updates
// 3. ServerStart / ConnectData signatures are NOT frozen across versions; check the docs of your version.
// =============================================================================

using ExcelDna.Integration;
using ExcelDna.Integration.Rtd;   // RTD types (ExcelRtdServer, Topic)
using System.Timers;
using System.Collections.Generic;

namespace MyExcelAddIn
{
    /// <summary>
    /// Real-time data server: pushes a new random value to all subscribers every second.
    /// </summary>
    public class MyRtdServer : ExcelRtdServer
    {
        private Timer _timer;          // .NET built-in timer
        private double _lastValue = 0; // latest value

        // -------------------------------------------------------------------------
        // Server start: invoked by Excel-DNA when this RTD is loaded (parameter-less).
        // Return true to indicate success.
        // -------------------------------------------------------------------------
        protected override bool ServerStart()
        {
            _timer = new Timer(1000);   // Trigger every 1000 ms (1 second)

            _timer.Elapsed += (s, e) =>
            {
                // Mock data: random number in [0, 100) every second.
                _lastValue = new System.Random().NextDouble() * 100;

                // Push the latest value to all active topics.
                foreach (Topic topic in GetActiveTopics())
                {
                    topic.UpdateValue(_lastValue);   // Tell Excel: please refresh.
                }
            };

            _timer.Start();
            return true;
        }

        // -------------------------------------------------------------------------
        // Server terminate: invoked when Excel unloads; do cleanup.
        // -------------------------------------------------------------------------
        protected override void ServerTerminate()
        {
            _timer?.Stop();
            _timer?.Dispose();
            _timer = null;
        }

        // -------------------------------------------------------------------------
        // Excel calls this when a topic is first subscribed; return the initial value.
        // -------------------------------------------------------------------------
        protected override object ConnectData(Topic topic, IList<string> topicInfo, ref bool newValues)
        {
            newValues = true;
            return _lastValue;
        }

        // -------------------------------------------------------------------------
        // Excel calls this when a topic is unsubscribed; usually a no-op.
        // -------------------------------------------------------------------------
        protected override void DisconnectData(Topic topic)
        {
            // no-op
        }
    }
}