using System;
using System.Threading.Tasks;

namespace ZB.MOM.WW.OtOpcUa.Host.Utilities
{
    /// <summary>
    ///     Bounded safety wrappers for blocking on async tasks from synchronous OPC UA stack
    ///     callbacks (Read, Write, HistoryRead*, BuildAddressSpace). These are backstops: the
    ///     underlying MxAccess / Historian clients already enforce inner timeouts on the async
    ///     path, but an outer bound is still required so the stack thread cannot be parked
    ///     indefinitely by a hung scheduler, a slow reconnect, or any other non-returning
    ///     async path.
    /// </summary>
    /// <remarks>
    ///     On timeout, the underlying task is NOT cancelled — it runs to completion on the
    ///     thread pool and is abandoned. Callers must be comfortable with the fire-forget
    ///     semantics of the background continuation. This is acceptable for the current call
    ///     sites because MxAccess and Historian clients are shared singletons whose background
    ///     work does not capture request-scoped state.
    /// </remarks>
    internal static class SyncOverAsync
    {
        public static void WaitSync(Task task, TimeSpan timeout, string operation)
        {
            if (task == null) throw new ArgumentNullException(nameof(task));
            try
            {
                if (!task.Wait(timeout))
                    throw new TimeoutException($"{operation} exceeded {timeout.TotalSeconds:0.#}s");
            }
            catch (AggregateException ae) when (ae.InnerExceptions.Count == 1)
            {
                // Unwrap the single inner exception so callers can write natural catch blocks.
                throw ae.InnerExceptions[0];
            }
        }

        public static T WaitSync<T>(Task<T> task, TimeSpan timeout, string operation)
        {
            if (task == null) throw new ArgumentNullException(nameof(task));
            try
            {
                if (!task.Wait(timeout))
                    throw new TimeoutException($"{operation} exceeded {timeout.TotalSeconds:0.#}s");
                return task.Result;
            }
            catch (AggregateException ae) when (ae.InnerExceptions.Count == 1)
            {
                throw ae.InnerExceptions[0];
            }
        }
    }
}