using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;

namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests;

/// <summary>
///     PR 2.2 — handle-based access with caching. Verifies the cache state machine
///     mirrored on <see cref="FakeTwinCATClient"/>: cold-key resolves through
///     <see cref="ITwinCATClient"/> -> CreateVariableHandle, warm-key reuses the cached
///     handle, <see cref="TwinCAT.Ads.AdsErrorCode.DeviceSymbolVersionInvalid"/> evicts +
///     retries, and Dispose / reconnect / FlushOptionalCachesAsync wipe the cache.
/// </summary>
/// <remarks>
///     The fake's state machine is a high-fidelity mirror of <c>AdsTwinCATClient</c>:
///     the production class is exercised through the same code paths in the integration
///     tier (<c>TwinCATHandleCachePerfTests</c>) and through the fake at unit tier here —
///     consistent with how the rest of this driver tests its <c>AdsClient</c> wrapper.
/// </remarks>
[Trait("Category", "Unit")]
public sealed class TwinCATHandleCacheTests
{
    private const string DevA = "ads://5.23.91.23.1.1:851";

    private static (TwinCATDriver drv, FakeTwinCATClientFactory factory) NewDriver(params TwinCATTagDefinition[] tags)
    {
        var factory = new FakeTwinCATClientFactory();
        var hosts = tags.Select(t => t.DeviceHostAddress).Distinct().ToArray();
        if (hosts.Length == 0) hosts = [DevA];
        var drv = new TwinCATDriver(new TwinCATDriverOptions
        {
            Devices = [.. hosts.Select(h => new TwinCATDeviceOptions(h))],
            Tags = tags,
            Probe = new TwinCATProbeOptions { Enabled = false },
        }, "drv-handle", factory);
        return (drv, factory);
    }

    [Fact]
    public async Task Same_symbol_read_twice_creates_single_handle()
    {
        // Force the per-tag path (whole-array reads + bit-extracted BOOL skip the bulk
        // surface in PR 2.1; both still flow through the handle cache). Whole-array is
        // the simplest single-symbol read for this assertion — see TwinCATSumCommandTests
        // for the bulk-path's own handle-free path.
        var fake = new FakeTwinCATClient { Values = { ["MAIN.Speed"] = 42 } };
        await fake.ReadValueAsync("MAIN.Speed", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        await fake.ReadValueAsync("MAIN.Speed", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);

        fake.HandleCreateInvocations.ShouldBe(["MAIN.Speed"]);
        fake.ReadByHandleInvocations.Count.ShouldBe(2);
        fake.HandleCacheCount.ShouldBe(1);
    }

    [Fact]
    public async Task Two_distinct_symbols_create_two_handles()
    {
        var fake = new FakeTwinCATClient
        {
            Values = { ["MAIN.A"] = 1, ["MAIN.B"] = 2 },
        };
        await fake.ReadValueAsync("MAIN.A", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        await fake.ReadValueAsync("MAIN.B", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        await fake.ReadValueAsync("MAIN.A", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);

        fake.HandleCreateInvocations.ShouldBe(["MAIN.A", "MAIN.B"]);
        fake.HandleCacheCount.ShouldBe(2);
    }

    [Fact]
    public async Task SymbolVersionInvalid_evicts_and_retries_with_fresh_handle()
    {
        var fake = new FakeTwinCATClient { Values = { ["MAIN.Counter"] = 10 } };

        // First read populates the cache.
        await fake.ReadValueAsync("MAIN.Counter", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        fake.HandleCreateInvocations.Count.ShouldBe(1);

        // Arm SymbolVersionInvalid for the next read; the fake's state machine evicts
        // the cached handle + retries once, exactly as AdsTwinCATClient does on the real wire.
        fake.SymbolVersionInvalidOnNextRead.Add("MAIN.Counter");
        await fake.ReadValueAsync("MAIN.Counter", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);

        // Two creates total — original + retry — and one delete on eviction.
        fake.HandleCreateInvocations.ShouldBe(["MAIN.Counter", "MAIN.Counter"]);
        fake.HandleDeleteInvocations.Count.ShouldBe(1);
        // After the retry the cache is repopulated.
        fake.HandleCacheCount.ShouldBe(1);
    }

    [Fact]
    public async Task SymbolVersionInvalid_on_write_evicts_and_retries()
    {
        var fake = new FakeTwinCATClient();
        await fake.WriteValueAsync("MAIN.Setpoint", TwinCATDataType.DInt, null, null, 100, TestContext.Current.CancellationToken);
        fake.HandleCreateInvocations.Count.ShouldBe(1);

        fake.SymbolVersionInvalidOnNextWrite.Add("MAIN.Setpoint");
        await fake.WriteValueAsync("MAIN.Setpoint", TwinCATDataType.DInt, null, null, 200, TestContext.Current.CancellationToken);

        fake.HandleCreateInvocations.ShouldBe(["MAIN.Setpoint", "MAIN.Setpoint"]);
        fake.HandleDeleteInvocations.Count.ShouldBe(1);
        fake.HandleCacheCount.ShouldBe(1);
    }

    [Fact]
    public async Task Dispose_deletes_all_cached_handles()
    {
        var fake = new FakeTwinCATClient
        {
            Values = { ["A"] = 1, ["B"] = 2, ["C"] = 3 },
        };
        await fake.ReadValueAsync("A", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        await fake.ReadValueAsync("B", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        await fake.ReadValueAsync("C", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        fake.HandleCacheCount.ShouldBe(3);

        fake.Dispose();

        fake.HandleCacheCount.ShouldBe(0);
        fake.HandleDeleteInvocations.Count.ShouldBe(3);
    }

    [Fact]
    public async Task FlushOptionalCachesAsync_clears_cache_then_recreates_handle()
    {
        var fake = new FakeTwinCATClient { Values = { ["X"] = 1 } };
        await fake.ReadValueAsync("X", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        fake.HandleCreateInvocations.Count.ShouldBe(1);
        fake.HasCachedHandle("X").ShouldBeTrue();

        await fake.FlushOptionalCachesAsync();

        fake.FlushOptionalCachesCount.ShouldBe(1);
        fake.HasCachedHandle("X").ShouldBeFalse();
        fake.HandleDeleteInvocations.Count.ShouldBe(1);

        // Subsequent read recreates.
        await fake.ReadValueAsync("X", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        fake.HandleCreateInvocations.Count.ShouldBe(2);
    }

    [Fact]
    public async Task Reconnect_clears_handle_cache()
    {
        var fake = new FakeTwinCATClient { Values = { ["MAIN.Y"] = 9 } };
        await fake.ConnectAsync(new TwinCATAmsAddress("5.23.91.23.1.1", 851), TimeSpan.FromSeconds(5),
            TestContext.Current.CancellationToken);
        await fake.ReadValueAsync("MAIN.Y", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        fake.HandleCacheCount.ShouldBe(1);

        // Simulate a connection drop + reconnect — handles from the prior session are dead.
        fake.SimulateReconnect();

        fake.HandleCacheCount.ShouldBe(0);
        // Next read repopulates with a fresh handle.
        await fake.ReadValueAsync("MAIN.Y", TwinCATDataType.DInt, null, null, TestContext.Current.CancellationToken);
        fake.HandleCreateInvocations.Count.ShouldBe(2);
    }

    [Fact]
    public async Task Bulk_path_does_not_consume_handle_cache()
    {
        // PR 2.2 deviation note: bulk Sum-read / Sum-write stays on symbolic paths because
        // the perf win over the per-tag handle path is marginal vs the diff cost. This test
        // pins the contract — bulk does not create handles, the per-tag path does.
        var (drv, factory) = NewDriver(
            new TwinCATTagDefinition("X", DevA, "MAIN.X", TwinCATDataType.DInt),
            new TwinCATTagDefinition("Y", DevA, "MAIN.Y", TwinCATDataType.DInt));
        await drv.InitializeAsync("{}", TestContext.Current.CancellationToken);
        factory.Customise = () => new FakeTwinCATClient
        {
            Values = { ["MAIN.X"] = 1, ["MAIN.Y"] = 2 },
        };

        await drv.ReadAsync(["X", "Y"], TestContext.Current.CancellationToken);
        await drv.ReadAsync(["X", "Y"], TestContext.Current.CancellationToken);

        var client = factory.Clients[0];
        client.BulkReadInvocations.Count.ShouldBe(2);
        client.HandleCreateInvocations.Count.ShouldBe(0);
        client.HandleCacheCount.ShouldBe(0);
    }

    [Fact]
    public async Task Per_tag_path_through_driver_uses_handle_cache()
    {
        // Whole-array reads route through the per-tag ReadValueAsync path — perfect for
        // exercising the handle cache via the public driver surface.
        var (drv, factory) = NewDriver(
            new TwinCATTagDefinition("Recipe", DevA, "MAIN.Recipe", TwinCATDataType.DInt,
                ArrayDimensions: [4]));
        await drv.InitializeAsync("{}", TestContext.Current.CancellationToken);
        factory.Customise = () => new FakeTwinCATClient
        {
            Values = { ["MAIN.Recipe"] = new int[] { 1, 2, 3, 4 } },
        };

        await drv.ReadAsync(["Recipe"], TestContext.Current.CancellationToken);
        await drv.ReadAsync(["Recipe"], TestContext.Current.CancellationToken);
        await drv.ReadAsync(["Recipe"], TestContext.Current.CancellationToken);

        var client = factory.Clients[0];
        client.HandleCreateInvocations.ShouldBe(["MAIN.Recipe"]);
        client.ReadByHandleInvocations.Count.ShouldBe(3);
    }

    [Fact]
    public async Task Bit_RMW_routes_parent_word_through_handle_cache()
    {
        // BOOL-in-word writes do read + write of the parent UDINT — both hops should
        // share the same cached handle for the parent. After three writes there should
        // still be only one handle for "Flags".
        var (drv, factory) = NewDriver(
            new TwinCATTagDefinition("Bit3", DevA, "GVL.Flags.3", TwinCATDataType.Bool));
        await drv.InitializeAsync("{}", TestContext.Current.CancellationToken);
        factory.Customise = () => new FakeTwinCATClient { Values = { ["GVL.Flags"] = 0u } };

        await drv.WriteAsync([new WriteRequest("Bit3", true)], TestContext.Current.CancellationToken);
        await drv.WriteAsync([new WriteRequest("Bit3", false)], TestContext.Current.CancellationToken);
        await drv.WriteAsync([new WriteRequest("Bit3", true)], TestContext.Current.CancellationToken);

        var client = factory.Clients[0];
        client.HandleCreateInvocations.ShouldBe(["GVL.Flags"]);
        client.HandleCacheCount.ShouldBe(1);
        // Three RMWs = three reads + three writes by handle on the parent.
        client.ReadByHandleInvocations.Count(x => x == "GVL.Flags").ShouldBe(3);
        client.WriteByHandleInvocations.Count(x => x == "GVL.Flags").ShouldBe(3);
    }
}