using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
using ZB.MOM.WW.OtOpcUa.Configuration.Validation;

namespace ZB.MOM.WW.OtOpcUa.Configuration.Apply;

/// <summary>
///     Per-entity diff computed locally on the node. The enumerable order matches the dependency
///     order expected by <see cref="IGenerationApplier"/>: namespace → driver → device → equipment →
///     poll group → tag → ACL, with Removed processed before Added inside each bucket so cascades
///     settle before new rows appear.
/// </summary>
public sealed record GenerationDiff(
    IReadOnlyList<EntityChange<Namespace>> Namespaces,
    IReadOnlyList<EntityChange<DriverInstance>> Drivers,
    IReadOnlyList<EntityChange<Device>> Devices,
    IReadOnlyList<EntityChange<Equipment>> Equipment,
    IReadOnlyList<EntityChange<PollGroup>> PollGroups,
    IReadOnlyList<EntityChange<Tag>> Tags);

public sealed record EntityChange<T>(ChangeKind Kind, string LogicalId, T? From, T? To);

public static class GenerationDiffer
{
    public static GenerationDiff Compute(DraftSnapshot? from, DraftSnapshot to)
    {
        from ??= new DraftSnapshot { GenerationId = 0, ClusterId = to.ClusterId };

        return new GenerationDiff(
            Namespaces: DiffById(from.Namespaces, to.Namespaces, x => x.NamespaceId,
                (a, b) => (a.ClusterId, a.NamespaceUri, a.Kind, a.Enabled, a.Notes)
                      == (b.ClusterId, b.NamespaceUri, b.Kind, b.Enabled, b.Notes)),
            Drivers: DiffById(from.DriverInstances, to.DriverInstances, x => x.DriverInstanceId,
                (a, b) => (a.ClusterId, a.NamespaceId, a.Name, a.DriverType, a.Enabled, a.DriverConfig)
                      == (b.ClusterId, b.NamespaceId, b.Name, b.DriverType, b.Enabled, b.DriverConfig)),
            Devices: DiffById(from.Devices, to.Devices, x => x.DeviceId,
                (a, b) => (a.DriverInstanceId, a.Name, a.Enabled, a.DeviceConfig)
                      == (b.DriverInstanceId, b.Name, b.Enabled, b.DeviceConfig)),
            Equipment: DiffById(from.Equipment, to.Equipment, x => x.EquipmentId,
                (a, b) => (a.EquipmentUuid, a.DriverInstanceId, a.UnsLineId, a.Name, a.MachineCode, a.ZTag, a.SAPID, a.Enabled)
                      == (b.EquipmentUuid, b.DriverInstanceId, b.UnsLineId, b.Name, b.MachineCode, b.ZTag, b.SAPID, b.Enabled)),
            PollGroups: DiffById(from.PollGroups, to.PollGroups, x => x.PollGroupId,
                (a, b) => (a.DriverInstanceId, a.Name, a.IntervalMs)
                      == (b.DriverInstanceId, b.Name, b.IntervalMs)),
            Tags: DiffById(from.Tags, to.Tags, x => x.TagId,
                (a, b) => (a.DriverInstanceId, a.DeviceId, a.EquipmentId, a.PollGroupId, a.FolderPath, a.Name, a.DataType, a.AccessLevel, a.WriteIdempotent, a.TagConfig)
                      == (b.DriverInstanceId, b.DeviceId, b.EquipmentId, b.PollGroupId, b.FolderPath, b.Name, b.DataType, b.AccessLevel, b.WriteIdempotent, b.TagConfig)));
    }

    private static List<EntityChange<T>> DiffById<T>(
        IReadOnlyList<T> from, IReadOnlyList<T> to,
        Func<T, string> id, Func<T, T, bool> equal)
    {
        var fromById = from.ToDictionary(id);
        var toById = to.ToDictionary(id);
        var result = new List<EntityChange<T>>();

        foreach (var (logicalId, src) in fromById.Where(kv => !toById.ContainsKey(kv.Key)))
            result.Add(new(ChangeKind.Removed, logicalId, src, default));

        foreach (var (logicalId, dst) in toById)
        {
            if (!fromById.TryGetValue(logicalId, out var src))
                result.Add(new(ChangeKind.Added, logicalId, default, dst));
            else if (!equal(src, dst))
                result.Add(new(ChangeKind.Modified, logicalId, src, dst));
        }

        return result;
    }
}