using System.Text.Json;
using Fleet.Core;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using MoShiro.Backend.Application;
using MoShiro.Protocol;

namespace MoShiro.Backend.Api;

/// <summary>构建信息与更新：后端和每个节点的版本、tag、构建时间，CI 签名的发布清单，以及「更新这个节点」的请求。更新本身由节点宿主机上的更新器验签并执行。</summary>
public static class BuildEndpoints
{
    private const string Tag = "admin-build";

    public static void Map(RouteGroupBuilder group)
    {
        group.MapGet("/build-info", GetAsync)
            .Api("build_info_get", "Version, tag, commit, build time and update state of the backend and every agent and probe", Tag)
            .Returns<BuildInfoDto>().ProducesProblems(401, 403)
            .Requires(Capability.UpdateRead);
        group.MapGet("/releases", ListReleasesAsync)
            .Api("releases_list", "The latest signed release manifest of each component", Tag).Returns<PageDto<ReleaseDto>>().ProducesProblems(401, 403)
            .Requires(Capability.UpdateRead);
        group.MapPost("/nodes/{id}/update", RequestUpdateAsync)
            .Api("nodes_update", "Ask an online agent or probe to install the release it has been offered", Tag).Returns<object>(StatusCodes.Status204NoContent).ProducesProblems(401, 403, 409)
            .Requires(Capability.UpdateConfirm);
        group.MapGet("/backend/update", BackendUpdateAsync)
            .Api("backend_update_get", "Current channel and host-verified backend update", Tag).Returns<BackendUpdateDto>().ProducesProblems(401, 403)
            .Requires(Capability.UpdateRead);
        group.MapPost("/backend/update", ConfirmBackendUpdateAsync)
            .Api("backend_update_confirm", "Confirm one verified backend release before the host restarts it", Tag).Returns<object>(StatusCodes.Status204NoContent).ProducesProblems(400, 401, 403, 412)
            .Requires(Capability.UpdateConfirm);
        group.MapGet("/backend/update/live", LiveBackendUpdateAsync)
            .Api("backend_update_live", "Server-sent backend update notifications", Tag).Produces(StatusCodes.Status200OK, contentType: "text/event-stream").ProducesProblems(401, 403)
            .Requires(Capability.UpdateRead);
    }

    /// <summary>
    /// CI 登记清单的入口，<b>不需要令牌</b>：请求里的清单必须带有效的 CI 发布签名（用 Backend 内嵌的发布公钥验）才收下。
    /// 这样登记不依赖面板里的任何凭证（清库、重装、还没有 passkey 的时候照常工作），也没有一把能被偷的长期令牌；
    /// 旧清单重放由 <c>seq</c> 递增挡住，节点的更新器还会用本机公钥再验一次。
    /// </summary>
    public static void MapOffer(IEndpointRouteBuilder app)
    {
        app.MapPost("/api/release/offer", OfferReleaseAsync)
            .Api("release_offer", "Register a release manifest that carries a valid CI signature (no token needed)", "release")
            .Returns<ReleaseDto>(StatusCodes.Status201Created).ProducesProblems(400, 403, 409);
    }

    private static async Task<IResult> OfferReleaseAsync(HttpContext http, ReleaseService releases, ReleaseKeyService keys, PublishReleaseRequest request)
    {
        string manifest = request.Manifest ?? "";
        string signature = request.Signature ?? "";
        if (manifest.Length is 0 or > ReleaseService.MaxManifestBytes || signature.Length is 0 or > ReleaseService.MaxSignatureBytes
            || !await keys.VerifyAsync(manifest, signature, http.RequestAborted))
        {
            return Problems.Create(http, MoShiroErrors.Forbidden, "the manifest does not carry a valid release signature");
        }

        return await PublishReleaseAsync(http, releases, request);
    }

    private static async Task<IResult> GetAsync(HttpContext http, NodeInfoService nodes, ReleaseService releases, BackendUpdates backendUpdates, NodeOwnerService owners, CancellationToken ct)
    {
        IReadOnlyDictionary<string, IReadOnlyList<NodeOwner>> ownerOf = await owners.ListAsync(ct);
        var items = (await nodes.ListAsync(ct))
            .OrderBy(n => n.Kind, StringComparer.Ordinal)
            .ThenBy(n => n.NodeId, StringComparer.Ordinal)
            .Select(n => new NodeBuildDto(n.NodeId, n.Kind, n.Os, n.OsName, n.Arch, n.Version, n.Tag, n.Commit, n.BuiltAt, ToDto(releases.StatusOf(new NodeId(n.NodeId))), ownerOf.TryGetValue(n.NodeId, out IReadOnlyList<NodeOwner>? list) ? [.. list.Select(o => new NodeOwnerDto(o.CredentialId, o.PasskeyName, o.Username))] : null))
            .ToList();
        http.Response.Headers.CacheControl = "no-store";
        return TypedResults.Json(new BuildInfoDto(NodeEndpoints.Backend(withCommit: true), items, ToDto(await backendUpdates.GetAsync(ct))), ApiJsonContext.Default.BuildInfoDto);
    }

    private static async Task<IResult> ListReleasesAsync(ReleaseService releases, CancellationToken ct) =>
        TypedResults.Json(new PageDto<ReleaseDto>([.. (await releases.ListAsync(ct)).Select(ToDto)], null), ApiJsonContext.Default.PageDtoReleaseDto);

    private static async Task<IResult> PublishReleaseAsync(HttpContext http, ReleaseService releases, PublishReleaseRequest request)
    {
        Result<ReleaseOffer> result = await releases.PublishAsync(request.Manifest ?? "", request.Signature ?? "", http.RequestAborted);
        return result.TryGet(out ReleaseOffer? offer, out FleetError? error)
            ? TypedResults.Json(ToDto(offer), ApiJsonContext.Default.ReleaseDto, statusCode: StatusCodes.Status201Created)
            : Problems.From(http, error);
    }

    private static async Task<IResult> RequestUpdateAsync(HttpContext http, ReleaseService releases, string id, CancellationToken ct) =>
        await releases.RequestUpdateAsync(new NodeId(id), ct) ? TypedResults.NoContent() : Problems.Create(http, MoShiroErrors.AgentOffline, "the node is not connected");

    private static ReleaseDto ToDto(ReleaseOffer offer) => new(offer.Component, offer.Seq, offer.Tag, offer.Version, offer.Digest, offer.Channel);

    private static BackendUpdateDto ToDto(BackendUpdateView view) =>
        new(view.Channel, view.Enabled, view.State, view.CurrentTag, view.CurrentDigest, view.Available is { } release ? ToDto(release) : null, view.Error);

    private static async Task<IResult> BackendUpdateAsync(BackendUpdates updates, CancellationToken ct) =>
        TypedResults.Json(ToDto(await updates.GetAsync(ct)), ApiJsonContext.Default.BackendUpdateDto);

    private static async Task<IResult> ConfirmBackendUpdateAsync(HttpContext http, BackendUpdates updates, ConfirmBackendUpdateRequest request, CancellationToken ct)
    {
        Result<bool> result = await updates.ConfirmAsync(request.Seq, ct);
        return result.IsSuccess ? TypedResults.NoContent() : Problems.From(http, result.Error);
    }

    private static async Task LiveBackendUpdateAsync(HttpContext http, BackendUpdates updates, TimeProvider time, CancellationToken ct)
    {
        http.Response.ContentType = "text/event-stream";
        http.Response.Headers.CacheControl = "no-store";
        http.Response.Headers["X-Accel-Buffering"] = "no";
        using var timer = new PeriodicTimer(TimeSpan.FromSeconds(2), time);
        string? previous = null;
        try
        {
            do
            {
                string json = JsonSerializer.Serialize(ToDto(await updates.GetAsync(ct)), ApiJsonContext.Default.BackendUpdateDto);
                await http.Response.WriteAsync(json != previous ? "event: backend_update\ndata: " + json + "\n\n" : ": heartbeat\n\n", ct);
                await http.Response.Body.FlushAsync(ct);
                previous = json;
            }
            while (await timer.WaitForNextTickAsync(ct));
        }
        catch (OperationCanceledException) when (ct.IsCancellationRequested)
        {
            // 浏览器断开或后端正在升级重启
        }
    }

    private static NodeUpdateDto? ToDto(UpdateStatus? status) =>
        status is null ? null : new NodeUpdateDto(status.State, status.Current, status.Available?.Tag, status.Available?.Version, status.Error, status.At > 0 ? DateTimeOffset.FromUnixTimeSeconds(status.At) : null);
}