namespace ZB.MOM.WW.OtOpcUa.Driver.AbCip.Import;

/// <summary>
///     Converts a parsed <see cref="L5kDocument"/> into <see cref="AbCipTagDefinition"/> entries
///     ready to be merged into <see cref="AbCipDriverOptions.Tags"/>. UDT definitions become
///     <see cref="AbCipStructureMember"/> lists keyed by data-type name; tags whose
///     <see cref="L5kTag.DataType"/> matches a known UDT get those members attached so the
///     discovery code can fan out the structure.
/// </summary>
/// <remarks>
///     <para>
///         <strong>Alias tags are skipped</strong> — when <see cref="L5kTag.AliasFor"/> is
///         non-null the entry is dropped at ingest. Surfacing both the alias + its target
///         creates duplicate Variables in the OPC UA address space (Kepware's L5K importer
///         takes the same approach for this reason; the alias target is the single source of
///         truth for storage).
///     </para>
///     <para>
///         <strong>Tags with <c>ExternalAccess := None</c> are skipped</strong> — the controller
///         actively rejects external reads/writes, so emitting them as Variables would just
///         produce permanent BadCommunicationError. <c>Read Only</c> maps to <c>Writable=false</c>;
///         <c>Read/Write</c> (or absent) maps to <c>Writable=true</c>.
///     </para>
///     <para>
///         Unknown data-type names (not atomic + not a parsed UDT) fall through as
///         <see cref="AbCipDataType.Structure"/> with no member layout — discovery can still
///         expose them as black-box variables and the operator can pin them via dotted paths.
///     </para>
/// </remarks>
public sealed class L5kIngest
{
    /// <summary>Default device host address applied to every imported tag.</summary>
    public string DefaultDeviceHostAddress { get; init; } = string.Empty;

    /// <summary>
    ///     Optional prefix prepended to imported tag names — useful when ingesting multiple
    ///     L5K exports into one driver instance to avoid name collisions. Default empty.
    /// </summary>
    public string NamePrefix { get; init; } = string.Empty;

    public L5kIngestResult Ingest(L5kDocument document)
    {
        ArgumentNullException.ThrowIfNull(document);
        if (string.IsNullOrWhiteSpace(DefaultDeviceHostAddress))
            throw new InvalidOperationException(
                $"{nameof(L5kIngest)}.{nameof(DefaultDeviceHostAddress)} must be set before {nameof(Ingest)} is called — every imported tag needs a target device.");

        // Index UDT definitions by name so we can fan out structure tags inline.
        var udtIndex = new Dictionary<string, IReadOnlyList<AbCipStructureMember>>(StringComparer.OrdinalIgnoreCase);
        foreach (var dt in document.DataTypes)
        {
            var members = new List<AbCipStructureMember>(dt.Members.Count);
            foreach (var m in dt.Members)
            {
                var atomic = TryMapAtomic(m.DataType);
                var memberType = atomic ?? AbCipDataType.Structure;
                var writable = !IsReadOnly(m.ExternalAccess) && !IsAccessNone(m.ExternalAccess);
                members.Add(new AbCipStructureMember(m.Name, memberType, writable));
            }
            udtIndex[dt.Name] = members;
        }

        var tags = new List<AbCipTagDefinition>();
        var skippedAliases = 0;
        var skippedNoAccess = 0;
        foreach (var t in document.Tags)
        {
            if (!string.IsNullOrEmpty(t.AliasFor)) { skippedAliases++; continue; }
            if (IsAccessNone(t.ExternalAccess)) { skippedNoAccess++; continue; }

            var atomic = TryMapAtomic(t.DataType);
            AbCipDataType dataType;
            IReadOnlyList<AbCipStructureMember>? members = null;
            if (atomic is { } a)
            {
                dataType = a;
            }
            else
            {
                dataType = AbCipDataType.Structure;
                if (udtIndex.TryGetValue(t.DataType, out var udtMembers))
                    members = udtMembers;
            }

            var tagPath = t.ProgramScope is { Length: > 0 }
                ? $"Program:{t.ProgramScope}.{t.Name}"
                : t.Name;
            var name = string.IsNullOrEmpty(NamePrefix) ? t.Name : $"{NamePrefix}{t.Name}";
            // Make the OPC UA tag name unique when both controller-scope + program-scope tags
            // share the same simple Name.
            if (t.ProgramScope is { Length: > 0 })
                name = string.IsNullOrEmpty(NamePrefix)
                    ? $"{t.ProgramScope}.{t.Name}"
                    : $"{NamePrefix}{t.ProgramScope}.{t.Name}";

            var writable = !IsReadOnly(t.ExternalAccess);

            tags.Add(new AbCipTagDefinition(
                Name: name,
                DeviceHostAddress: DefaultDeviceHostAddress,
                TagPath: tagPath,
                DataType: dataType,
                Writable: writable,
                Members: members));
        }

        return new L5kIngestResult(tags, skippedAliases, skippedNoAccess);
    }

    private static bool IsReadOnly(string? externalAccess) =>
        externalAccess is not null
        && externalAccess.Trim().Replace(" ", string.Empty).Equals("ReadOnly", StringComparison.OrdinalIgnoreCase);

    private static bool IsAccessNone(string? externalAccess) =>
        externalAccess is not null && externalAccess.Trim().Equals("None", StringComparison.OrdinalIgnoreCase);

    /// <summary>Map a Logix atomic type name. Returns <c>null</c> for UDT/structure references.</summary>
    private static AbCipDataType? TryMapAtomic(string logixType) =>
        logixType?.Trim().ToUpperInvariant() switch
        {
            "BOOL" or "BIT" => AbCipDataType.Bool,
            "SINT" => AbCipDataType.SInt,
            "INT" => AbCipDataType.Int,
            "DINT" => AbCipDataType.DInt,
            "LINT" => AbCipDataType.LInt,
            "USINT" => AbCipDataType.USInt,
            "UINT" => AbCipDataType.UInt,
            "UDINT" => AbCipDataType.UDInt,
            "ULINT" => AbCipDataType.ULInt,
            "REAL" => AbCipDataType.Real,
            "LREAL" => AbCipDataType.LReal,
            "STRING" => AbCipDataType.String,
            "DT" or "DATETIME" => AbCipDataType.Dt,
            _ => null,
        };
}

/// <summary>Result of <see cref="L5kIngest.Ingest"/> — produced tags + per-skip-reason counts.</summary>
public sealed record L5kIngestResult(
    IReadOnlyList<AbCipTagDefinition> Tags,
    int SkippedAliasCount,
    int SkippedNoAccessCount);