using System.Reflection;
using Fleet.Rpc;
using Fleet.Server;
using Microsoft.Extensions.DependencyInjection;
using MoShiro.Probe;
using MoShiro.Protocol;

namespace MoShiro.Backend.Tests;

/// <summary>
/// 协议方向声明（<see cref="MoShiroMethodTable"/>）和实际代码的对账：每个方法常量都声明了，每一侧该处理的方法都注册了处理函数，
/// 二进制通道都有对应的收件箱，文档里写了每一个方法。新增方法绕不过声明，声明了没人处理也会被发现。
/// 注册处理函数时路由器本身还会核对方向、类型和角色，不符就在启动时失败。
/// </summary>
public sealed class ProtocolDeclarationTests : IClassFixture<BackendFixture>
{
    private static readonly MethodTable s_table = MoShiroMethodTable.Table;

    private readonly BackendFixture _backend;

    public ProtocolDeclarationTests(BackendFixture backend)
    {
        _backend = backend;
    }

    private static IEnumerable<string> ConstantsOf(Type type) =>
        type.GetFields(BindingFlags.Public | BindingFlags.Static).Where(f => f.IsLiteral && f.FieldType == typeof(string)).Select(f => (string)f.GetRawConstantValue()!);

    [Fact]
    public void EveryMethodConstant_IsDeclared()
    {
        HashSet<string> declared = [.. s_table.Methods.Select(m => m.Name)];
        string[] undeclared = [.. ConstantsOf(typeof(FleetMethods)).Concat(ConstantsOf(typeof(PeerMethods))).Concat(ConstantsOf(typeof(MoShiroMethods))).Where(n => !declared.Contains(n))];
        Assert.Empty(undeclared);
    }

    [Fact]
    public void EveryDeclaredMethod_IsDocumented()
    {
        string root = FindRoot();
        string docs = File.ReadAllText(Path.Combine(root, "docs", "design", "protocol.md")) + File.ReadAllText(Path.Combine(root, "backend", "fleet", "README.md"));
        string[] missing = [.. s_table.Methods.Select(m => m.Name).Distinct().Where(n => !docs.Contains($"`{n}`", StringComparison.Ordinal))];
        Assert.Empty(missing);
    }

    [Fact]
    public void Backend_HandlesEveryMethodNodesMayInitiate_AndHasAnInboxForEveryDeclaredChannel()
    {
        FleetRouter router = _backend.Services.GetRequiredService<FleetRouter>();
        Assert.Empty(router.Table.MissingHandlers(RpcSide.Server, null, router.Methods));

        byte[] inboxes = [.. _backend.Services.GetServices<IInbox>().Select(i => i.Channel).Order()];
        byte[] declared = [.. s_table.Channels.Where(c => c.Plane == RpcPlane.Node).Select(c => c.Channel).Order()];
        Assert.Equal(declared, inboxes);
    }

    [Fact]
    public async Task Agent_HandlesEveryMethodItShould_OnBothPlanes()
    {
        await using AgentHarness agent = await AgentHarness.StartAsync(_backend);
        Assert.Empty(s_table.MissingHandlers(RpcSide.Node, NodeRoles.Agent, agent.App.Link.Router.Methods));
        // 对等面：Agent 是监听方，要处理 Probe 发来的方法
        Assert.Empty(s_table.MissingHandlers(RpcSide.Listener, null, agent.App.PeerRouter.Methods));
    }

    [Fact]
    public async Task Probe_HandlesEveryMethodItShould_OnBothPlanes()
    {
        await using ProbeHarness probe = await ProbeHarness.StartAsync(_backend);
        Assert.Empty(s_table.MissingHandlers(RpcSide.Node, NodeRoles.Probe, probe.App.Link.Router.Methods));
        // 对等面：Probe 是拨号方，要处理 Agent 发来的方法
        Assert.Empty(s_table.MissingHandlers(RpcSide.Dialer, null, AgentConnection.Router.Methods));
    }

    [Fact]
    public void RolesOfNodeIds_FollowThePrefix()
    {
        Assert.Equal(NodeRoles.Agent, NodeRoles.Of(AgentIds.Prefix + "_01ABC"));
        Assert.Equal(NodeRoles.Probe, NodeRoles.Of(ProbeId.Prefix + "_01ABC"));
        Assert.Null(NodeRoles.Of("usr_01ABC"));
    }

    private static string FindRoot()
    {
        string? dir = AppContext.BaseDirectory;
        while (dir is not null && !File.Exists(Path.Combine(dir, "docs", "design", "protocol.md")))
        {
            dir = Path.GetDirectoryName(dir);
        }

        return dir ?? throw new InvalidOperationException("repository root not found");
    }
}