using System;
using System.Collections.Generic;
using ArchestrA.MxAccess;
using Serilog;
using ZB.MOM.WW.LmxProxy.Host.Domain;

namespace ZB.MOM.WW.LmxProxy.Host.MxAccess
{
    public sealed partial class MxAccessClient
    {
        /// <summary>
        ///     Callback invoked by the SubscriptionManager when it needs to deliver
        ///     data change events. Set by the SubscriptionManager during initialization.
        /// </summary>
        public Action<string, Vtq>? OnTagValueChanged { get; set; }

        /// <summary>
        ///     COM event handler for MxAccess OnDataChange events.
        ///     Called on the STA thread when a subscribed tag value changes.
        ///     Signature matches the ArchestrA.MxAccess ILMXProxyServerEvents interface.
        /// </summary>
        private void OnDataChange(
            int hLMXServerHandle,
            int phItemHandle,
            object pvItemValue,
            int pwItemQuality,
            object pftItemTimeStamp,
            ref MXSTATUS_PROXY[] ItemStatus)
        {
            try
            {
                var quality = MapQuality(pwItemQuality);
                var timestamp = ConvertTimestamp(pftItemTimeStamp);
                var vtq = new Vtq(pvItemValue, timestamp, quality);

                // We don't have the address from the COM callback — the reference code
                // looks it up from _subscriptionsByHandle. For the v2 design, the
                // SubscriptionManager's global handler receives (address, vtq) via
                // OnTagValueChanged. The actual address resolution will be implemented
                // when the full subscription tracking is wired up on windev.

                // Route to the SubscriptionManager's global handler
                OnTagValueChanged?.Invoke(phItemHandle.ToString(), vtq);
            }
            catch (Exception ex)
            {
                Log.Error(ex, "Error processing OnDataChange event for handle {Handle}", phItemHandle);
            }
        }

        /// <summary>
        ///     COM event handler for MxAccess OnWriteComplete events.
        ///     Signature matches the ArchestrA.MxAccess ILMXProxyServerEvents interface.
        /// </summary>
        private void OnWriteComplete(
            int hLMXServerHandle,
            int phItemHandle,
            ref MXSTATUS_PROXY[] ItemStatus)
        {
            // Write completion is currently fire-and-forget.
            // Log for diagnostics.
            try
            {
                Log.Debug("WriteCompleted: handle {Handle}", phItemHandle);
            }
            catch (Exception ex)
            {
                Log.Error(ex, "Error processing OnWriteComplete event for handle {Handle}", phItemHandle);
            }
        }

        /// <summary>
        ///     Converts a timestamp object to DateTime in UTC.
        /// </summary>
        private static DateTime ConvertTimestamp(object timestamp)
        {
            if (timestamp is DateTime dt)
            {
                return dt.Kind == DateTimeKind.Utc ? dt : dt.ToUniversalTime();
            }

            return DateTime.UtcNow;
        }
    }
}