using Shouldly;
using Xunit;
using ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxy;
using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browse;

namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests.Browse;

/// <summary>
///     Review 2026-10-21 G-5: <c>Repository.DiscoverPageSize</c> was authored and parsed but reached
///     nothing — the client's typed <c>DiscoverHierarchyAsync</c> hard-codes 5000. The source now pages
///     the raw RPC itself at the configured size.
/// </summary>
public sealed class GatewayGalaxyHierarchySourcePagingTests
{
    private static GalaxyObject Obj(int id) => new() { GobjectId = id, TagName = $"Obj{id}" };

    /// <summary>Every request carries the configured page size and the page tokens chain until the last page.</summary>
    [Fact]
    public async Task Pages_at_the_configured_size_and_chains_tokens()
    {
        var requests = new List<DiscoverHierarchyRequest>();
        Task<DiscoverHierarchyReply> Discover(DiscoverHierarchyRequest req, CancellationToken ct)
        {
            requests.Add(req);
            var reply = new DiscoverHierarchyReply();
            switch (req.PageToken)
            {
                case "":
                    reply.Objects.Add([Obj(1), Obj(2)]);
                    reply.NextPageToken = "p2";
                    break;
                case "p2":
                    reply.Objects.Add([Obj(3), Obj(4)]);
                    reply.NextPageToken = "p3";
                    break;
                default:
                    reply.Objects.Add(Obj(5));
                    reply.NextPageToken = "";
                    break;
            }
            return Task.FromResult(reply);
        }

        var objects = await GatewayGalaxyHierarchySource.PageAsync(Discover, pageSize: 2, CancellationToken.None);

        objects.Select(o => o.GobjectId).ShouldBe([1, 2, 3, 4, 5]);
        requests.Count.ShouldBe(3);
        requests.ShouldAllBe(r => r.PageSize == 2);
        requests.Select(r => r.PageToken).ShouldBe(["", "p2", "p3"]);
    }

    /// <summary>A different configured size is what goes on the wire (positive control for the knob).</summary>
    [Fact]
    public async Task A_different_page_size_is_sent_on_the_wire()
    {
        int? sent = null;
        Task<DiscoverHierarchyReply> Discover(DiscoverHierarchyRequest req, CancellationToken ct)
        {
            sent = req.PageSize;
            return Task.FromResult(new DiscoverHierarchyReply());
        }

        await GatewayGalaxyHierarchySource.PageAsync(Discover, pageSize: 250, CancellationToken.None);
        sent.ShouldBe(250);
    }

    /// <summary>A non-positive configured size falls back to the client library's 5000 default.</summary>
    [Theory]
    [InlineData(0)]
    [InlineData(-7)]
    public void Non_positive_page_size_falls_back_to_the_default(int configured)
        => GatewayGalaxyHierarchySource.EffectivePageSize(configured).ShouldBe(GatewayGalaxyHierarchySource.DefaultPageSize);

    /// <summary>A repeated page token is refused rather than walked forever.</summary>
    [Fact]
    public async Task A_repeated_page_token_is_refused()
    {
        var calls = 0;
        Task<DiscoverHierarchyReply> Discover(DiscoverHierarchyRequest req, CancellationToken ct)
        {
            calls++;
            var reply = new DiscoverHierarchyReply { NextPageToken = "same" };
            reply.Objects.Add(Obj(calls));
            return Task.FromResult(reply);
        }

        var ex = await Should.ThrowAsync<InvalidOperationException>(
            () => GatewayGalaxyHierarchySource.PageAsync(Discover, pageSize: 10, CancellationToken.None));
        ex.Message.ShouldContain("repeated page token");
        calls.ShouldBe(2);
    }
}