namespace MoShiro.Backend.Application;

/// <summary>某一时刻的「线路」开关：自动连接的总开关，加上每一对（拨号方，监听方）的手动设置。</summary>
public sealed class LinkSnapshot
{
    private readonly Dictionary<(string Dialer, string Listener), bool> _overrides;

    public LinkSnapshot(bool auto, Dictionary<(string Dialer, string Listener), bool> overrides)
    {
        Auto = auto;
        _overrides = overrides;
    }

    /// <summary>自动连接：开着时，所有节点自动拨其他监听节点；关着时，只有手动开启的才连。两个监听节点默认双向互连。</summary>
    public bool Auto { get; }

    /// <summary>手动设置：<c>true</c> 强制连、<c>false</c> 强制不连、<c>null</c> 没设置（跟随自动连接）。</summary>
    public bool? OverrideOf(string dialerId, string listenerId) => _overrides.TryGetValue((dialerId, listenerId), out bool value) ? value : null;

    /// <summary>这一对最终连不连：手动设置优先，没有就看自动连接。</summary>
    public bool IsLinked(AgentRecord dialer, AgentRecord listener) =>
        dialer.Id != listener.Id && (OverrideOf(dialer.Id.Value, listener.Id.Value) ?? Auto);
}

/// <summary>
/// 哪些（拨号方，监听方）要连成线路。由面板决定、拨号方主动拨出：自动连接开着时，所有节点拨其他监听节点（默认），
/// 关着时只连手动选中的；每一对还可以手动强制开或关，每个方向的线路独立设置。手动设置存在设置表里（<c>link.&lt;拨号方&gt;.&lt;监听方&gt;</c>，值 1 或 0，空表示没设置）。
/// 判断结果分别用在拨号方的拨号目标、监听方允许的拨号方（<c>peers</c>）和线路目录里；改动之后要调用 <see cref="AgentService.AfterAgentSetChangedAsync"/> 重新下发。
/// </summary>
public sealed class LinkService
{
    private const string Prefix = "link.";

    private readonly ISettingsStore _settings;

    public LinkService(ISettingsStore settings)
    {
        _settings = settings;
    }

    public async ValueTask<LinkSnapshot> SnapshotAsync(CancellationToken ct)
    {
        IReadOnlyDictionary<string, string> all = await _settings.GetAllAsync(ct);
        var overrides = new Dictionary<(string, string), bool>();
        foreach ((string key, string value) in all)
        {
            string[] parts = key.Split('.');
            if (parts.Length == 3 && parts[0] + "." == Prefix && value is "1" or "0")
            {
                overrides[(parts[1], parts[2])] = value == "1";
            }
        }

        return new LinkSnapshot(all.GetValueOrDefault(SettingsService.AutoLink) != "false", overrides);
    }

    /// <summary>手动设置一对线路：<c>true</c> 强制连、<c>false</c> 强制不连、<c>null</c> 取消手动设置。</summary>
    public ValueTask SetAsync(string dialerId, string listenerId, bool? enabled, CancellationToken ct) =>
        _settings.SetAsync($"{Prefix}{dialerId}.{listenerId}", enabled is null ? "" : enabled.Value ? "1" : "0", ct);

    /// <summary>节点被删除：清掉所有涉及它的手动设置。</summary>
    public async ValueTask ForgetNodeAsync(string nodeId, CancellationToken ct)
    {
        foreach (string key in (await _settings.GetAllAsync(ct)).Keys.Where(k => k.StartsWith(Prefix, StringComparison.Ordinal) && k.Split('.').Skip(1).Contains(nodeId)))
        {
            await _settings.SetAsync(key, "", ct);
        }
    }
}