namespace MoShiro.Backend.Application;

/// <summary>
/// 能力（capability）：一项具体的权限。端点声明自己需要哪一项，<see cref="Principal.Has"/> 是唯一的判断入口，
/// 会话、API key 都走它。设计见 docs/security/access.md 第 3 节。
/// </summary>
public static class Capability
{
    /// <summary>任何已认证的主体（会话或 API key）；只有登出、查看自己这类端点用它。</summary>
    public const string Authenticated = "authenticated";

    public const string PublicRead = "public.read";

    public const string FleetRead = "fleet.read";
    public const string FleetWrite = "fleet.write";
    public const string FleetEnroll = "fleet.enroll";
    public const string FleetRevoke = "fleet.revoke";

    public const string TasksRead = "tasks.read";
    public const string TasksWrite = "tasks.write";

    public const string DataRead = "data.read";
    public const string DataWrite = "data.write";

    public const string SettingsRead = "settings.read";
    public const string SettingsWrite = "settings.write";

    public const string UpdateRead = "update.read";
    public const string UpdateConfirm = "update.confirm";

    public const string KeysRead = "keys.read";
    public const string KeysManage = "keys.manage";

    public const string AccountsRead = "accounts.read";
    public const string AccountsManage = "accounts.manage";

    public const string AuditRead = "audit.read";
    public const string EventsRead = "events.read";
    public const string OpsMetrics = "ops.metrics";

    // 预留：外部 webhook 回调和数据拉取（docs/security/access.md 6.3），目录里先存在，实现放后面
    public const string DataExport = "data.export";
    public const string WebhooksRead = "webhooks.read";
    public const string WebhooksManage = "webhooks.manage";
}

/// <summary>一项能力的元数据。<c>Trust</c>：改变信任或有破坏性的能力（吊销、账户），界面上特别标出，授权与其他能力一样靠 API key 或登录会话；真正由 passkey 签名保护的是操作员集合，那是节点自己验证的；<c>Reserved</c>：还没有对应的功能。</summary>
public sealed record CapabilityInfo(string Id, string Group, bool Trust = false, bool Reserved = false, params string[] Implies);

public sealed record CapabilityPreset(string Id, IReadOnlyList<string> Capabilities);

/// <summary>能力目录：分组、依赖（写蕴含读）、预设，以及创建 API key 时的校验。</summary>
public static class CapabilityCatalog
{
    public static IReadOnlyList<CapabilityInfo> All { get; } =
    [
        new(Capability.PublicRead, "public"),

        new(Capability.FleetRead, "fleet"),
        new(Capability.FleetWrite, "fleet", false, false, Capability.FleetRead),
        new(Capability.FleetEnroll, "fleet", false, false, Capability.FleetRead),
        new(Capability.FleetRevoke, "fleet", true, false, Capability.FleetRead),

        new(Capability.TasksRead, "tasks"),
        new(Capability.TasksWrite, "tasks", false, false, Capability.TasksRead),

        new(Capability.DataRead, "data"),
        new(Capability.DataWrite, "data", false, false, Capability.DataRead),
        new(Capability.DataExport, "data", false, true, Capability.DataRead),

        new(Capability.SettingsRead, "settings"),
        new(Capability.SettingsWrite, "settings", false, false, Capability.SettingsRead),

        new(Capability.UpdateRead, "update"),
        new(Capability.UpdateConfirm, "update", false, false, Capability.UpdateRead),

        new(Capability.KeysRead, "keys"),
        new(Capability.KeysManage, "keys", false, false, Capability.KeysRead),

        new(Capability.AccountsRead, "accounts"),
        new(Capability.AccountsManage, "accounts", true, false, Capability.AccountsRead),

        new(Capability.EventsRead, "ops"),
        new(Capability.AuditRead, "ops"),
        new(Capability.OpsMetrics, "ops"),

        new(Capability.WebhooksRead, "integrations", false, true),
        new(Capability.WebhooksManage, "integrations", false, true, Capability.WebhooksRead),
    ];

    private static readonly Dictionary<string, CapabilityInfo> s_byId = All.ToDictionary(c => c.Id, StringComparer.Ordinal);

    public static IReadOnlyList<string> Groups { get; } = [.. All.Select(c => c.Group).Distinct()];

    public static IReadOnlyList<CapabilityPreset> Presets { get; } =
    [
        new("read-only", [.. All.Where(c => !c.Reserved && c.Id.EndsWith(".read", StringComparison.Ordinal)).Select(c => c.Id)]),
        new("operations", Expand([Capability.PublicRead, Capability.FleetWrite, Capability.TasksWrite, Capability.DataWrite, Capability.SettingsWrite, Capability.UpdateConfirm, Capability.EventsRead, Capability.AuditRead])),
        new("enroll", Expand([Capability.FleetEnroll])),
        new("all", [.. All.Select(c => c.Id)]),
    ];

    public static bool IsKnown(string id) => s_byId.ContainsKey(id);

    /// <summary>补上蕴含的能力（写蕴含读），去重并排序，结果稳定。</summary>
    public static IReadOnlyList<string> Expand(IEnumerable<string> ids)
    {
        var result = new SortedSet<string>(StringComparer.Ordinal);
        foreach (string id in ids)
        {
            Add(result, id);
        }

        return [.. result];
    }

    private static void Add(SortedSet<string> set, string id)
    {
        if (id is Capability.Authenticated || !set.Add(id) || !s_byId.TryGetValue(id, out CapabilityInfo? info))
        {
            return;
        }

        foreach (string implied in info.Implies)
        {
            Add(set, implied);
        }
    }

    /// <summary>
    /// 登录会话的能力：全部，包括信任类，密码登录和 passkey 登录一样。区别在于敏感操作：信任类的操作还要有效的提权窗口（<see cref="ElevationService"/>），
    /// 窗口要当场触碰 passkey 才能开，所以密码泄露的人做不了这些，日常管理却不需要每次触碰。
    /// </summary>
    public static IReadOnlyList<string> ForSession() => [.. All.Select(c => c.Id)];

}