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

namespace ZB.MOM.WW.OtOpcUa.Driver.S7.Tests;

/// <summary>
///     Scaffold-level tests that don't need a live S7 PLC — exercise driver lifecycle shape,
///     default option values, and failure-mode transitions. PR 64 adds IReadable/IWritable
///     tests against a mock-server, PR 65 adds discovery + subscribe.
/// </summary>
[Trait("Category", "Unit")]
public sealed class S7DriverScaffoldTests
{
    [Fact]
    public void Default_options_target_S7_1500_slot_0_on_port_102()
    {
        var opts = new S7DriverOptions();
        opts.Port.ShouldBe(102, "ISO-on-TCP is always 102 for S7; documented in driver-specs.md §5");
        opts.CpuType.ShouldBe(global::S7.Net.CpuType.S71500);
        opts.Rack.ShouldBe((short)0);
        opts.Slot.ShouldBe((short)0, "S7-1200/1500 onboard PN ports are slot 0 by convention");
    }

    [Fact]
    public void Default_probe_interval_is_reasonable_for_S7_scan_cycle()
    {
        // S7 PLCs scan 2-10 ms but comms mailbox typically processed once per scan.
        // 5 s default probe is lightweight — ~0.001% of comms budget.
        new S7ProbeOptions().Interval.ShouldBe(TimeSpan.FromSeconds(5));
    }

    [Fact]
    public void Tag_definition_defaults_to_writable_with_S7_max_string_length()
    {
        var tag = new S7TagDefinition("T", "DB1.DBW0", S7DataType.Int16);
        tag.Writable.ShouldBeTrue();
        tag.StringLength.ShouldBe(254, "S7 STRING type max length is 254 chars");
    }

    [Fact]
    public void Driver_instance_reports_type_and_id_before_connect()
    {
        var opts = new S7DriverOptions { Host = "127.0.0.1" };
        using var drv = new S7Driver(opts, "s7-test");
        drv.DriverType.ShouldBe("S7");
        drv.DriverInstanceId.ShouldBe("s7-test");
        drv.GetHealth().State.ShouldBe(DriverState.Unknown, "health starts Unknown until InitializeAsync runs");
    }

    [Fact]
    public async Task Initialize_against_unreachable_host_transitions_to_Faulted_and_throws()
    {
        // Pick an RFC 5737 reserved-for-documentation IP so the connect attempt fails fast
        // (no DNS mismatch, no accidental traffic to a real PLC).
        var opts = new S7DriverOptions { Host = "192.0.2.1", Timeout = TimeSpan.FromMilliseconds(250) };
        using var drv = new S7Driver(opts, "s7-unreach");

        await Should.ThrowAsync<Exception>(async () =>
            await drv.InitializeAsync("{}", TestContext.Current.CancellationToken));

        var health = drv.GetHealth();
        health.State.ShouldBe(DriverState.Faulted, "unreachable host must flip the driver to Faulted so operators see it");
        health.LastError.ShouldNotBeNull();
    }
}