using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;

namespace ZB.MOM.WW.OtOpcUa.Commons.Tests.OpcUa;

/// <summary>
/// Covers the deferred-sink forwarding invariants documented in Commons-003.
/// The DeferredAddressSpaceSink is a production-critical seam: a new optional capability
/// interface MUST be forwarded through it or the optimization is inert on every driver-role
/// host (DeferredAddressSpaceSink is what actors inject, not the inner sink directly).
/// </summary>
public class DeferredAddressSpaceSinkTests
{
    // ---------- before SetSink — all calls are safe no-ops ----------

    [Fact]
    public void Before_SetSink_WriteValue_is_a_noop()
    {
        var sink = new DeferredAddressSpaceSink();
        // Must not throw.
        sink.WriteValue("ns=2;s=x", 42, OpcUaQuality.Good, DateTime.UtcNow);
    }

    [Fact]
    public void Before_SetSink_RebuildAddressSpace_is_a_noop()
    {
        var sink = new DeferredAddressSpaceSink();
        sink.RebuildAddressSpace(); // Must not throw.
    }

    [Fact]
    public void Before_SetSink_UpdateTagAttributes_returns_false()
    {
        var sink = new DeferredAddressSpaceSink();
        sink.UpdateTagAttributes("ns=2;s=x", writable: true, historianTagname: null,
            dataType: "Boolean", isArray: false, arrayLength: null).ShouldBeFalse();
    }

    // ---------- after SetSink — operations are forwarded ----------

    [Fact]
    public void After_SetSink_WriteValue_is_forwarded()
    {
        var inner = new SpySink();
        var sink = new DeferredAddressSpaceSink();
        sink.SetSink(inner);

        sink.WriteValue("ns=2;s=x", 99, OpcUaQuality.Good, DateTime.UtcNow);

        inner.WriteValueCalled.ShouldBeTrue();
    }

    [Fact]
    public void After_SetSink_RebuildAddressSpace_is_forwarded()
    {
        var inner = new SpySink();
        var sink = new DeferredAddressSpaceSink();
        sink.SetSink(inner);

        sink.RebuildAddressSpace();

        inner.RebuildCalled.ShouldBeTrue();
    }

    // ---------- ISurgicalAddressSpaceSink forwarding ----------

    [Fact]
    public void UpdateTagAttributes_returns_false_for_non_surgical_inner()
    {
        // SpySink does NOT implement ISurgicalAddressSpaceSink.
        var sink = new DeferredAddressSpaceSink();
        sink.SetSink(new SpySink());

        sink.UpdateTagAttributes("ns=2;s=x", writable: true, historianTagname: null,
            dataType: "Int32", isArray: false, arrayLength: null).ShouldBeFalse();
    }

    [Fact]
    public void UpdateTagAttributes_returns_true_for_surgical_inner()
    {
        var surgical = new SpySurgicalSink();
        var sink = new DeferredAddressSpaceSink();
        sink.SetSink(surgical);

        var result = sink.UpdateTagAttributes("ns=2;s=x", writable: true, historianTagname: null,
            dataType: "Float", isArray: false, arrayLength: null);

        result.ShouldBeTrue();
        surgical.UpdateCalled.ShouldBeTrue();
    }

    // ---------- SetSink(null) reverts to null sink ----------

    [Fact]
    public void SetSink_null_reverts_to_null_sink_and_UpdateTagAttributes_returns_false()
    {
        var surgical = new SpySurgicalSink();
        var sink = new DeferredAddressSpaceSink();
        sink.SetSink(surgical);
        sink.SetSink(null); // revert

        sink.UpdateTagAttributes("ns=2;s=x", writable: false, historianTagname: null,
            dataType: "Boolean", isArray: false, arrayLength: null).ShouldBeFalse();
    }

    [Fact]
    public void SetSink_null_reverts_to_null_sink_and_WriteValue_is_noop()
    {
        var inner = new SpySink();
        var sink = new DeferredAddressSpaceSink();
        sink.SetSink(inner);
        sink.SetSink(null); // revert

        sink.WriteValue("ns=2;s=x", 1, OpcUaQuality.Good, DateTime.UtcNow);

        inner.WriteValueCalled.ShouldBeFalse("write should be no-op after reverting to null sink");
    }

    // ---- test doubles ----

    private sealed class SpySink : IOpcUaAddressSpaceSink
    {
        public bool WriteValueCalled { get; private set; }
        public bool RebuildCalled { get; private set; }

        public void WriteValue(string nodeId, object? value, OpcUaQuality quality, DateTime sourceTimestampUtc)
            => WriteValueCalled = true;

        public void WriteAlarmCondition(string alarmNodeId, AlarmConditionSnapshot state, DateTime sourceTimestampUtc) { }
        public void MaterialiseAlarmCondition(string alarmNodeId, string equipmentNodeId, string displayName, string alarmType, int severity, bool isNative = false) { }
        public void EnsureFolder(string folderNodeId, string? parentNodeId, string displayName) { }
        public void EnsureVariable(string variableNodeId, string? parentFolderNodeId, string displayName, string dataType, bool writable, string? historianTagname = null, bool isArray = false, uint? arrayLength = null) { }
        public void RebuildAddressSpace() => RebuildCalled = true;
    }

    private sealed class SpySurgicalSink : IOpcUaAddressSpaceSink, ISurgicalAddressSpaceSink
    {
        public bool UpdateCalled { get; private set; }

        public void WriteValue(string nodeId, object? value, OpcUaQuality quality, DateTime sourceTimestampUtc) { }
        public void WriteAlarmCondition(string alarmNodeId, AlarmConditionSnapshot state, DateTime sourceTimestampUtc) { }
        public void MaterialiseAlarmCondition(string alarmNodeId, string equipmentNodeId, string displayName, string alarmType, int severity, bool isNative = false) { }
        public void EnsureFolder(string folderNodeId, string? parentNodeId, string displayName) { }
        public void EnsureVariable(string variableNodeId, string? parentFolderNodeId, string displayName, string dataType, bool writable, string? historianTagname = null, bool isArray = false, uint? arrayLength = null) { }
        public void RebuildAddressSpace() { }

        public bool UpdateTagAttributes(string variableNodeId, bool writable, string? historianTagname, string dataType, bool isArray, uint? arrayLength)
        {
            UpdateCalled = true;
            return true;
        }
    }
}