using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Runtime.Drivers;

namespace ZB.MOM.WW.OtOpcUa.Runtime.Tests.Drivers;

public sealed class DriverSpawnPlannerTests
{
    private static DriverInstanceSpec Spec(string id, string type = "Modbus", string config = "{\"host\":\"127.0.0.1\"}", bool enabled = true, string? resilience = null) =>
        new(Guid.NewGuid(), id, id, type, enabled, config, ClusterId: null, ResilienceConfig: resilience);

    /// <summary>Verifies that all new drivers are placed in ToSpawn when current is empty.</summary>
    [Fact]
    public void All_new_drivers_go_into_ToSpawn_when_current_is_empty()
    {
        var current = new Dictionary<string, DriverChildSnapshot>();
        var target = new[] { Spec("a"), Spec("b") };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToSpawn.Count.ShouldBe(2);
        plan.ToApplyDelta.ShouldBeEmpty();
        plan.ToStop.ShouldBeEmpty();
    }

    /// <summary>Verifies that the same configuration yields an empty plan.</summary>
    [Fact]
    public void Same_config_yields_empty_plan()
    {
        var current = new Dictionary<string, DriverChildSnapshot>
        {
            ["a"] = new("Modbus", "{\"host\":\"127.0.0.1\"}"),
        };
        var target = new[] { Spec("a") };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToSpawn.ShouldBeEmpty();
        plan.ToApplyDelta.ShouldBeEmpty();
        plan.ToStop.ShouldBeEmpty();
    }

    /// <summary>
    ///     A changed <c>DriverConfig</c> forces a stop + respawn (#516), NOT an in-place delta.
    ///     <para>This test previously asserted the opposite. The in-place path silently discarded the edit
    ///     on five drivers whose <c>InitializeAsync</c> served constructor-captured options and never read
    ///     the <c>driverConfigJson</c> they were handed — and the deployment still sealed green. Routing
    ///     through the factory makes it the single parse authority, which matters most for the drivers that
    ///     build MORE than options from config (Sql's dialect + connection string, FOCAS's client-factory
    ///     backend) where re-parsing options alone would apply a new tag set against an old connection.</para>
    ///     <para>The accepted cost is a reconnect on every config edit.</para>
    /// </summary>
    [Fact]
    public void Different_config_routes_to_stop_and_respawn()
    {
        var current = new Dictionary<string, DriverChildSnapshot>
        {
            ["a"] = new("Modbus", "{\"host\":\"old\"}"),
        };
        var target = new[] { Spec("a", config: "{\"host\":\"new\"}") };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToStop.Single().ShouldBe("a");
        plan.ToSpawn.Single().DriverInstanceId.ShouldBe("a");
        plan.ToSpawn.Single().DriverConfig.ShouldBe("{\"host\":\"new\"}");
        // The whole point: nothing is left on the in-place path that could discard the edit.
        plan.ToApplyDelta.ShouldBeEmpty();
    }

    /// <summary>Verifies that removed drivers are routed to ToStop.</summary>
    [Fact]
    public void Removed_driver_routes_to_ToStop()
    {
        var current = new Dictionary<string, DriverChildSnapshot>
        {
            ["a"] = new("Modbus", "{\"host\":\"127.0.0.1\"}"),
            ["b"] = new("Modbus", "{}"),
        };
        var target = new[] { Spec("a") };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToStop.ShouldBe(new[] { "b" });
        plan.ToSpawn.ShouldBeEmpty();
        plan.ToApplyDelta.ShouldBeEmpty();
    }

    /// <summary>Verifies that disabled drivers with running children are routed to ToStop.</summary>
    [Fact]
    public void Disabled_driver_with_running_child_routes_to_ToStop()
    {
        var current = new Dictionary<string, DriverChildSnapshot>
        {
            ["a"] = new("Modbus", "{}"),
        };
        var target = new[] { Spec("a", enabled: false) };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToStop.Single().ShouldBe("a");
        plan.ToSpawn.ShouldBeEmpty();
        plan.ToApplyDelta.ShouldBeEmpty();
    }

    /// <summary>Verifies that disabled new drivers are not spawned.</summary>
    [Fact]
    public void Disabled_new_driver_is_not_spawned()
    {
        var current = new Dictionary<string, DriverChildSnapshot>();
        var target = new[] { Spec("a", enabled: false) };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToSpawn.ShouldBeEmpty();
        plan.ToApplyDelta.ShouldBeEmpty();
        plan.ToStop.ShouldBeEmpty();
    }

    /// <summary>Verifies that driver type changes trigger stop followed by respawn.</summary>
    [Fact]
    public void Driver_type_change_triggers_stop_plus_respawn()
    {
        var current = new Dictionary<string, DriverChildSnapshot>
        {
            ["a"] = new("Modbus", "{}"),
        };
        var target = new[] { Spec("a", type: "AbCip") };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToStop.Single().ShouldBe("a");
        plan.ToSpawn.Single().DriverType.ShouldBe("AbCip");
        plan.ToApplyDelta.ShouldBeEmpty();
    }

    /// <summary>
    ///     A ResilienceConfig change forces a stop+respawn (NOT an in-place delta): the CapabilityInvoker
    ///     and its resolved options are bound to the child at spawn, so the only way a changed config takes
    ///     effect is to rebuild the child (the respawn's Create call invalidates the stale cached pipelines).
    /// </summary>
    [Fact]
    public void ResilienceConfig_change_triggers_stop_plus_respawn()
    {
        var current = new Dictionary<string, DriverChildSnapshot>
        {
            // Same DriverType + same DriverConfig; only ResilienceConfig differs.
            ["a"] = new("Modbus", "{\"host\":\"127.0.0.1\"}", ResilienceConfig: "{\"bulkheadMaxConcurrent\":8}"),
        };
        var target = new[] { Spec("a", resilience: "{\"bulkheadMaxConcurrent\":32}") };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToStop.Single().ShouldBe("a");
        plan.ToSpawn.Single().DriverInstanceId.ShouldBe("a");
        plan.ToApplyDelta.ShouldBeEmpty();
    }

    /// <summary>
    ///     Adding a ResilienceConfig where there was none (null → JSON) is also a respawn — the invoker
    ///     was built with tier defaults and must be rebuilt to pick up the overrides.
    /// </summary>
    [Fact]
    public void Adding_ResilienceConfig_from_null_triggers_respawn()
    {
        var current = new Dictionary<string, DriverChildSnapshot>
        {
            ["a"] = new("Modbus", "{\"host\":\"127.0.0.1\"}", ResilienceConfig: null),
        };
        var target = new[] { Spec("a", resilience: "{\"bulkheadMaxConcurrent\":16}") };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToStop.Single().ShouldBe("a");
        plan.ToSpawn.Single().DriverInstanceId.ShouldBe("a");
        plan.ToApplyDelta.ShouldBeEmpty();
    }

    /// <summary>
    ///     A pure DriverConfig change respawns even when the ResilienceConfig is UNCHANGED.
    ///     <para>This asserted the opposite until #516. The reasoning then was "the resilience pipeline is
    ///     untouched, so there's no reason to respawn" — correct about resilience, wrong about the driver:
    ///     five drivers ignored the config the in-place delta handed them, and the deployment sealed green
    ///     anyway. The reconnect is the accepted price of the edit actually taking effect.</para>
    /// </summary>
    [Fact]
    public void DriverConfig_change_respawns_even_when_ResilienceConfig_is_unchanged()
    {
        var current = new Dictionary<string, DriverChildSnapshot>
        {
            ["a"] = new("Modbus", "{\"host\":\"old\"}", ResilienceConfig: "{\"bulkheadMaxConcurrent\":16}"),
        };
        var target = new[] { Spec("a", config: "{\"host\":\"new\"}", resilience: "{\"bulkheadMaxConcurrent\":16}") };

        var plan = DriverSpawnPlanner.Compute(current, target);

        plan.ToStop.Single().ShouldBe("a");
        plan.ToSpawn.Single().DriverInstanceId.ShouldBe("a");
        plan.ToApplyDelta.ShouldBeEmpty();
    }
}
