using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using MoShiro.Backend.Application;

namespace MoShiro.Backend.Api;

/// <summary>
/// 节点的展示信息：系统、架构、国家、运营商。<b>只有这几项，没有任何 IP 地址、城市、ASN、经纬度</b>——
/// 这些在 Backend 里只在查询的那一刻用到，存起来的记录里也没有，所以访客（和任何别的接口）都拿不到。
/// </summary>
public static class NodeEndpoints
{
    private const string Tag = "public-nodes";

    public static void Map(RouteGroupBuilder group)
    {
        group.MapGet("/nodes", ListAsync)
            .Api("nodes_list", "Display info of the visible agents and probes: system, architecture, country and ISP (never an address)", Tag)
            .Returns<PageDto<NodeInfoDto>>().ProducesProblems(403);
        group.MapGet("/about", AboutAsync)
            .Api("about_get", "The backend's version, tag and build time, if the site shows build info", Tag)
            .Returns<AboutDto>().ProducesProblems(403);
    }

    /// <summary>这个后端自己的构建信息；没有（本地构建）的字段是 <c>null</c>。</summary>
    internal static BuildDto Backend(bool withCommit) =>
        new(MoShiro.Protocol.BuildInfo.Version, Empty(MoShiro.Protocol.BuildInfo.Tag), withCommit ? Empty(MoShiro.Protocol.BuildInfo.Commit) : null, Empty(MoShiro.Protocol.BuildInfo.BuiltAt));

    private static string? Empty(string value) => value.Length == 0 ? null : value;

    private static async Task<IResult> AboutAsync(HttpContext http, SettingsService settings)
    {
        bool show = await settings.IsShowBuildAsync(http.RequestAborted);
        http.Response.Headers.CacheControl = "no-store";
        return TypedResults.Json(new AboutDto(show, show ? Backend(withCommit: false) : null), ApiJsonContext.Default.AboutDto);
    }

    private static async Task<IResult> ListAsync(HttpContext http, AgentService agents, ProbeService probes, NodeInfoService nodes, SettingsService settings, CancellationToken ct)
    {
        // 和别的公开接口一样：看得见的 Agent（隐藏的只有登录后才看得见）和没有被吊销的 Probe
        var visible = new HashSet<string>(StringComparer.Ordinal);
        foreach (AgentView view in await agents.ListAsync(ct))
        {
            if (view.Agent.Status == Fleet.Server.NodeStatus.Active && (view.Agent.PublicVisible || PublicGuard.CanSeeHidden(http)))
            {
                visible.Add(view.Agent.Id.Value);
            }
        }

        foreach (ProbeView probe in await probes.ListAsync(ct))
        {
            if (!probe.Revoked)
            {
                visible.Add(probe.Probe.Id);
            }
        }

        // 版本和 tag 只在站点打开「显示构建信息」时才给访客；关着就是 null
        bool showBuild = await settings.IsShowBuildAsync(ct);
        var items = (await nodes.ListAsync(ct))
            .Where(n => visible.Contains(n.NodeId))
            .OrderBy(n => n.NodeId, StringComparer.Ordinal)
            .Select(n => new NodeInfoDto(n.NodeId, n.Kind, n.Os, n.OsName, n.Arch, n.Country, n.IspKey, n.IspName, showBuild ? n.Version : null, showBuild ? n.Tag : null))
            .ToList();
        http.Response.Headers.CacheControl = "no-store";
        return TypedResults.Json(new PageDto<NodeInfoDto>(items, null), ApiJsonContext.Default.PageDtoNodeInfoDto);
    }
}