using System;
using System.Runtime.InteropServices;

namespace MxGateway.Worker.MxAccess;

/// <summary>Thrown when the worker fails to instantiate the MXAccess COM object.</summary>
public sealed class MxAccessCreationException : Exception
{
    /// <summary>Initializes a new instance with diagnostic info from the inner exception.</summary>
    /// <param name="innerException">The exception that caused the creation failure.</param>
    public MxAccessCreationException(Exception innerException)
        : base(
            $"Failed to create MXAccess COM object {MxAccessInteropInfo.ComClassName} ({MxAccessInteropInfo.ProgId}).",
            innerException)
    {
        AttemptedProgId = MxAccessInteropInfo.ProgId;
        AttemptedClsid = MxAccessInteropInfo.Clsid;
        AttemptedComClassName = MxAccessInteropInfo.ComClassName;
        HResult = innerException.HResult;
    }

    /// <summary>The ProgID that was attempted during COM instantiation.</summary>
    public string AttemptedProgId { get; }

    /// <summary>The CLSID that was attempted during COM instantiation.</summary>
    public string AttemptedClsid { get; }

    /// <summary>The COM class name that was attempted during instantiation.</summary>
    public string AttemptedComClassName { get; }

    /// <summary>The captured HResult from the instantiation failure, or null if zero.</summary>
    public int? CapturedHResult => HResult == 0 ? null : HResult;

    /// <summary>Wraps an exception in MxAccessCreationException if it is not already.</summary>
    /// <param name="exception">The exception to wrap.</param>
    /// <returns>An MxAccessCreationException wrapping the input exception.</returns>
    public static MxAccessCreationException From(Exception exception)
    {
        return exception is MxAccessCreationException creationException
            ? creationException
            : new MxAccessCreationException(exception);
    }

    /// <summary>Extracts the HResult from an exception, handling MXAccess and COM exceptions specially.</summary>
    /// <param name="exception">The exception to extract the HResult from.</param>
    /// <returns>The HResult value, or null if zero.</returns>
    public static int? ExtractHResult(Exception exception)
    {
        if (exception is MxAccessCreationException creationException)
        {
            return creationException.CapturedHResult;
        }

        if (exception is COMException comException)
        {
            return comException.HResult;
        }

        return exception.HResult == 0 ? null : exception.HResult;
    }
}