refactor!: rename the project from Monitor to MoShiro [CI]

Namespaces, assemblies, solution, binaries, images, systemd units, config paths, environment variables, protocol methods and the Linux user are all renamed. Breaking: existing databases, node identities and installed units must be recreated.

backend/src/MoShiro.Backend.Api/Common/QueryHelpers.cs

@@ -0,0 +1,95 @@
+using System.Security.Cryptography;
+using System.Text;
+using Fleet.Core;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using MoShiro.Backend.Application;
+using MoShiro.Protocol;
+
+namespace MoShiro.Backend.Api;
+
+internal static class QueryHelpers
+{
+    /// <summary>查询的统一超时（默认 10 s）：超时返回 503，而不是让请求一直挂着。</summary>
+    public static async Task<IResult> GuardedAsync(HttpContext http, Func<CancellationToken, Task<IResult>> work)
+    {
+        BackendOptions options = http.RequestServices.GetRequiredService<BackendOptions>();
+        using var timeout = CancellationTokenSource.CreateLinkedTokenSource(http.RequestAborted);
+        timeout.CancelAfter(options.QueryTimeout);
+        try
+        {
+            return await work(timeout.Token);
+        }
+        catch (OperationCanceledException) when (!http.RequestAborted.IsCancellationRequested)
+        {
+            return Problems.Create(http, MoShiroErrors.StorageUnavailable, null);
+        }
+    }
+
+    /// <summary>
+    /// 缓存策略：已经结束的绝对区间（<c>to</c> 早于当前时间 − 2 分钟）可以永久缓存，并带 ETag；相对时间段不缓存。
+    /// 返回非空时表示命中 If-None-Match，直接返回 304。
+    /// </summary>
+    public static IResult? ApplyCaching(HttpContext http, QueryRange range, long nowMs, string material)
+    {
+        bool closed = !range.IsRelative && range.RequestedToMs < nowMs - (2 * Steps.Minute);
+        if (!closed)
+        {
+            http.Response.Headers.CacheControl = "no-store";
+            return null;
+        }
+
+        string etag = ETagOf(http.Request.Path + http.Request.QueryString.Value + material);
+        http.Response.Headers.CacheControl = "public, max-age=31536000, immutable";
+        http.Response.Headers.ETag = etag;
+        return MatchesIfNoneMatch(http, etag) ? TypedResults.StatusCode(StatusCodes.Status304NotModified) : null;
+    }
+
+    /// <summary>目录：<c>max-age=300</c>，并带 ETag。</summary>
+    public static IResult? ApplyCatalogCaching(HttpContext http, string material)
+    {
+        string etag = ETagOf(http.Request.Path + material);
+        http.Response.Headers.CacheControl = "public, max-age=300";
+        http.Response.Headers.ETag = etag;
+        return MatchesIfNoneMatch(http, etag) ? TypedResults.StatusCode(StatusCodes.Status304NotModified) : null;
+    }
+
+    public static string ETagOf(string material) =>
+        "\"" + Convert.ToHexStringLower(SHA256.HashData(Encoding.UTF8.GetBytes(material)))[..32] + "\"";
+
+    private static bool MatchesIfNoneMatch(HttpContext http, string etag)
+    {
+        foreach (string? candidate in http.Request.Headers.IfNoneMatch)
+        {
+            if (candidate is not null && candidate.Split(',', StringSplitOptions.TrimEntries).Contains(etag))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /// <summary>线路 id（<c>agent~probe</c>，或只有一个 Probe 时的 Agent id）→ 可以展示的线路。否则 404 / 422（不暴露被隐藏的线路存在与否）。</summary>
+    public static async ValueTask<Result<LineView>> FindVisibleLineAsync(HttpContext http, LineService lines, string id, CancellationToken ct)
+    {
+        Result<LineView> found = await lines.ResolveAsync(id, ct);
+        if (!found.TryGet(out LineView? line, out FleetError? error))
+        {
+            return Result<LineView>.Fail(error);
+        }
+
+        return line.Agent.Agent.Status == Fleet.Server.NodeStatus.Active && (line.Agent.Agent.PublicVisible || PublicGuard.CanSeeHidden(http)) && line.Probe.RevokedAtMs is null
+            ? found
+            : Result<LineView>.Fail(MoShiroErrors.AgentNotFound, "line not found");
+    }
+
+    /// <summary>找到可以展示的线路：已激活，并且（对外可见，或者访问者已认证）。否则 404（不暴露被隐藏的线路存在与否）。</summary>
+    public static async ValueTask<Result<AgentView>> FindVisibleAgentAsync(HttpContext http, AgentService agents, string id, CancellationToken ct)
+    {
+        AgentView? view = await agents.GetAsync(new NodeId(id), ct);
+        return view is { Agent.Status: Fleet.Server.NodeStatus.Active } && (view.Agent.PublicVisible || PublicGuard.CanSeeHidden(http))
+            ? Result<AgentView>.Ok(view)
+            : Result<AgentView>.Fail(MoShiroErrors.AgentNotFound, "agent not found");
+    }
+}