using S7NetErrorCode = global::S7.Net.ErrorCode;
using S7NetPlcException = global::S7.Net.PlcException;

namespace ZB.MOM.WW.OtOpcUa.Driver.S7;

/// <summary>
///     Thrown by <see cref="S7Driver.InitializeAsync"/> when the post-<c>OpenAsync</c>
///     pre-flight probe receives a response that the driver classifies as
///     "PUT/GET communication disabled on the PLC". Surfaces a typed exception so
///     operators see the configuration-fix instructions immediately at init time
///     instead of waiting for the first per-tag read to fail with
///     <c>BadDeviceFailure</c>. See <c>docs/v2/s7.md</c> "Pre-flight PUT/GET enablement"
///     section for the full rationale.
/// </summary>
public sealed class S7PutGetDisabledException : Exception
{
    /// <summary>The probe address that triggered the typed classification (e.g. <c>MW0</c>).</summary>
    public string ProbeAddress { get; }

    /// <summary>
    ///     Construct a typed exception. <paramref name="inner"/> is the raw
    ///     <see cref="S7NetPlcException"/> from S7netplus that
    ///     <see cref="S7PreflightClassifier.IsPutGetDisabled"/> classified positive.
    /// </summary>
    public S7PutGetDisabledException(string probeAddress, Exception? inner = null)
        : base(BuildMessage(probeAddress), inner)
    {
        ProbeAddress = probeAddress;
    }

    internal static string BuildMessage(string probeAddress) =>
        "S7 pre-flight probe to '" + probeAddress + "' was rejected by the PLC. " +
        "PUT/GET communication is disabled on the PLC. " +
        "Enable it in TIA Portal: Device → Properties → Protection & Security → " +
        "Connection mechanisms → 'Permit access with PUT/GET communication from " +
        "remote partner'. Re-deploy the hardware config and restart the S7 driver. " +
        "Alternatively set 'Probe.SkipPreflight = true' to defer the check to runtime " +
        "(driver will still surface BadDeviceFailure on every read until PUT/GET is enabled).";
}

/// <summary>
///     Classifies an <see cref="S7NetPlcException"/> coming back from the pre-flight
///     probe read into "PUT/GET disabled" vs "everything else". Pulled out as a static
///     helper so unit tests can drive every branch (matching ErrorCode, non-matching
///     ErrorCode, null exception) without spinning up an S7 server. Mirrors the
///     <c>ModbusPreflight</c> pattern from the Modbus driver.
/// </summary>
public static class S7PreflightClassifier
{
    /// <summary>
    ///     Returns <c>true</c> when the exception's <c>ErrorCode</c> matches the
    ///     S7.Net surface for "PLC refused the read" — which on hardened S7-1200 /
    ///     S7-1500 firmware is the wire-level signal for PUT/GET disabled. We match
    ///     <see cref="S7NetErrorCode.WrongCPU_Type"/> (S7.Net's primary classification
    ///     when the response framing isn't a valid PDU because the CPU rejected the
    ///     request) and <see cref="S7NetErrorCode.ReadData"/> (the generic
    ///     "couldn't read" code S7.Net falls back to when the PLC sends an S7-level
    ///     error byte instead of a normal response).
    /// </summary>
    /// <remarks>
    ///     <para>
    ///         The S7-1200 / S7-1500 wire response when PUT/GET is disabled is an S7
    ///         "Function not allowed in current protection level" header byte
    ///         (0xD605 / 0x8500 family). S7netplus surfaces that as PlcException with
    ///         <see cref="S7NetErrorCode.ReadData"/> on the response path or
    ///         <see cref="S7NetErrorCode.WrongCPU_Type"/> when the CPU drops the
    ///         connection before sending a valid response. Matching both ensures the
    ///         driver flags the config bug regardless of which path the firmware takes.
    ///     </para>
    ///     <para>
    ///         A non-matching <see cref="S7NetErrorCode"/> (e.g.
    ///         <see cref="S7NetErrorCode.ConnectionError"/>,
    ///         <see cref="S7NetErrorCode.IPAddressNotAvailable"/>) means "transport
    ///         broke" — let the caller rethrow as-is so other failure shapes don't
    ///         get silently masked as "PUT/GET disabled".
    ///     </para>
    /// </remarks>
    public static bool IsPutGetDisabled(S7NetPlcException? exception)
    {
        if (exception is null) return false;
        return exception.ErrorCode is S7NetErrorCode.WrongCPU_Type
            or S7NetErrorCode.ReadData;
    }
}