using System.Collections.Concurrent;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;

namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests;

public sealed class DeferredAddressSpaceSinkTests
{
    /// <summary>Verifies that the default inner is a null sink so calls before SetSink are safe.</summary>
    [Fact]
    public void Default_inner_is_null_sink_so_calls_before_SetSink_are_safe()
    {
        var deferred = new DeferredAddressSpaceSink();

        // No throw, no observable side effect.
        deferred.WriteValue("x", 1, OpcUaQuality.Good, DateTime.UtcNow);
        deferred.WriteAlarmCondition("a", Snapshot(active: true), DateTime.UtcNow);
        deferred.RebuildAddressSpace();
    }

    /// <summary>Verifies that calls after SetSink are forwarded to the inner sink.</summary>
    [Fact]
    public void Calls_after_SetSink_are_forwarded_to_the_inner()
    {
        var deferred = new DeferredAddressSpaceSink();
        var inner = new RecordingSink();
        deferred.SetSink(inner);

        deferred.WriteValue("x", 42, OpcUaQuality.Good, DateTime.UtcNow);
        deferred.WriteAlarmCondition("a-1", Snapshot(active: true), DateTime.UtcNow);
        deferred.RebuildAddressSpace();

        inner.Calls.ShouldBe(new[] { "WV:x", "WA:a-1", "RB" });
    }

    /// <summary>Verifies that setting sink to null reverts to null sink.</summary>
    [Fact]
    public void SetSink_to_null_reverts_to_null_sink()
    {
        var deferred = new DeferredAddressSpaceSink();
        var inner = new RecordingSink();
        deferred.SetSink(inner);
        deferred.WriteValue("x", 1, OpcUaQuality.Good, DateTime.UtcNow);
        inner.Calls.Count.ShouldBe(1);

        deferred.SetSink(null);
        deferred.WriteValue("y", 2, OpcUaQuality.Good, DateTime.UtcNow); // dropped
        inner.Calls.Count.ShouldBe(1);
    }

    /// <summary>Verifies that sink can be swapped between implementations.</summary>
    [Fact]
    public void SetSink_can_swap_between_implementations()
    {
        var deferred = new DeferredAddressSpaceSink();
        var first = new RecordingSink();
        var second = new RecordingSink();

        deferred.SetSink(first);
        deferred.WriteValue("a", 1, OpcUaQuality.Good, DateTime.UtcNow);

        deferred.SetSink(second);
        deferred.WriteValue("b", 2, OpcUaQuality.Good, DateTime.UtcNow);

        first.Calls.Single().ShouldBe("WV:a");
        second.Calls.Single().ShouldBe("WV:b");
    }

    /// <summary>Verifies that <see cref="DeferredAddressSpaceSink.EnsureVariable"/> forwards the
    /// <c>historianTagname</c> argument to the inner sink unchanged.</summary>
    [Fact]
    public void EnsureVariable_forwards_historianTagname_to_inner_sink()
    {
        var deferred = new DeferredAddressSpaceSink();
        var inner = new RecordingSink();
        deferred.SetSink(inner);

        deferred.EnsureVariable("v-1", null, "MyVar", "Float", writable: false, historianTagname: "MyTag.PV");

        var call = inner.HistorianCalls.ShouldHaveSingleItem();
        call.NodeId.ShouldBe("v-1");
        call.HistorianTagname.ShouldBe("MyTag.PV");
    }

    /// <summary>F10b regression: the deferred wrapper MUST forward the surgical capability to a
    /// surgical inner sink — otherwise <c>AddressSpaceApplier</c> (which injects THIS wrapper on every
    /// driver-role host, not the inner <c>SdkAddressSpaceSink</c>) never sees the capability and the
    /// in-place tag-attribute optimization is inert in production (it silently falls back to rebuild).</summary>
    [Fact]
    public void UpdateTagAttributes_forwards_to_a_surgical_inner_sink()
    {
        var deferred = new DeferredAddressSpaceSink();
        var inner = new SurgicalRecordingSink { Result = true };
        deferred.SetSink(inner);

        ((ISurgicalAddressSpaceSink)deferred).UpdateTagAttributes("v-1", writable: true, historianTagname: "MyTag.PV")
            .ShouldBeTrue();

        var call = inner.SurgicalCalls.ShouldHaveSingleItem();
        call.NodeId.ShouldBe("v-1");
        call.Writable.ShouldBeTrue();
        call.Historian.ShouldBe("MyTag.PV");
    }

    /// <summary>The surgical forward returns the inner's own result (false ⇒ node missing) so the caller
    /// falls back to a full rebuild.</summary>
    [Fact]
    public void UpdateTagAttributes_returns_inner_result_when_node_missing()
    {
        var deferred = new DeferredAddressSpaceSink();
        deferred.SetSink(new SurgicalRecordingSink { Result = false });

        ((ISurgicalAddressSpaceSink)deferred).UpdateTagAttributes("v-1", writable: false, historianTagname: null)
            .ShouldBeFalse();
    }

    /// <summary>When the inner sink does NOT implement <see cref="ISurgicalAddressSpaceSink"/> (e.g. the
    /// null sink before the real one is swapped in, or any non-surgical sink) the wrapper returns false
    /// so the caller rebuilds.</summary>
    [Fact]
    public void UpdateTagAttributes_returns_false_when_inner_is_not_surgical()
    {
        var deferred = new DeferredAddressSpaceSink();   // default inner = null sink (not surgical)
        ((ISurgicalAddressSpaceSink)deferred).UpdateTagAttributes("v-1", writable: true, historianTagname: null)
            .ShouldBeFalse();

        deferred.SetSink(new RecordingSink());           // a non-surgical inner
        ((ISurgicalAddressSpaceSink)deferred).UpdateTagAttributes("v-1", writable: true, historianTagname: null)
            .ShouldBeFalse();
    }

    /// <summary>Builds a minimal <see cref="AlarmConditionSnapshot"/> for the forwarding tests (the
    /// inner sink only records the node id, so the exact state values don't matter here).</summary>
    private static AlarmConditionSnapshot Snapshot(bool active = false) =>
        new(active, Acknowledged: true, Confirmed: true, Enabled: true,
            Shelving: AlarmShelvingKind.Unshelved, Severity: 500, Message: "test");

    private sealed class RecordingSink : IOpcUaAddressSpaceSink
    {
        /// <summary>Gets the queue of recorded calls.</summary>
        public ConcurrentQueue<string> CallQueue { get; } = new();
        /// <summary>Gets the list of recorded calls.</summary>
        public List<string> Calls => CallQueue.ToList();

        /// <summary>Gets the queue of (NodeId, HistorianTagname) pairs captured per
        /// <c>EnsureVariable</c> call, in call order.</summary>
        public ConcurrentQueue<(string NodeId, string? HistorianTagname)> HistorianQueue { get; } = new();
        /// <summary>Gets the list of (NodeId, HistorianTagname) pairs captured per EnsureVariable call.</summary>
        public List<(string NodeId, string? HistorianTagname)> HistorianCalls => HistorianQueue.ToList();

        /// <inheritdoc />
        public void WriteValue(string nodeId, object? value, OpcUaQuality quality, DateTime sourceTimestampUtc)
            => CallQueue.Enqueue($"WV:{nodeId}");
        /// <inheritdoc />
        public void WriteAlarmCondition(string alarmNodeId, AlarmConditionSnapshot state, DateTime sourceTimestampUtc)
            => CallQueue.Enqueue($"WA:{alarmNodeId}");
        /// <inheritdoc />
        public void MaterialiseAlarmCondition(string alarmNodeId, string equipmentNodeId, string displayName, string alarmType, int severity, bool isNative = false)
            => CallQueue.Enqueue($"MA:{alarmNodeId}");
        /// <inheritdoc />
        public void EnsureFolder(string folderNodeId, string? parentNodeId, string displayName)
            => CallQueue.Enqueue($"EF:{folderNodeId}");
        /// <inheritdoc />
        public void EnsureVariable(string variableNodeId, string? parentFolderNodeId, string displayName, string dataType, bool writable, string? historianTagname = null, bool isArray = false, uint? arrayLength = null)
        {
            CallQueue.Enqueue($"EV:{variableNodeId}");
            HistorianQueue.Enqueue((variableNodeId, historianTagname));
        }
        /// <inheritdoc />
        public void RebuildAddressSpace() => CallQueue.Enqueue("RB");
    }

    private sealed class SurgicalRecordingSink : IOpcUaAddressSpaceSink, ISurgicalAddressSpaceSink
    {
        /// <summary>Gets or sets the value <see cref="UpdateTagAttributes"/> returns.</summary>
        public bool Result { get; set; } = true;
        /// <summary>Gets the recorded surgical calls.</summary>
        public List<(string NodeId, bool Writable, string? Historian)> SurgicalCalls { get; } = new();

        /// <inheritdoc />
        public bool UpdateTagAttributes(string variableNodeId, bool writable, string? historianTagname)
        {
            SurgicalCalls.Add((variableNodeId, writable, historianTagname));
            return Result;
        }

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