using WebDrop.FileProtocol;

namespace WebDrop.Core;

/// <summary>给客户端的文件服务入口:地址 + 一张短期票据</summary>
public sealed record FileGrant(string Url, string Ticket, long ExpiresAt);

/// <summary>
/// 主后端和文件服务之间的接口。关闭时(默认)所有帧仍然存在主后端自己的存储里,行为和以前完全一样;
/// 打开后,文件的内容(文件域的对象,不分大小)由客户端直接传给文件服务,主后端只登记元数据和摘要;聊天、头像、目录仍在主后端。
/// </summary>
public interface IFileGateway
{
    bool Enabled { get; }
    /// <summary>客户端拿到的文件服务根地址(经反向隧道对外的那个)</summary>
    string PublicUrl { get; }
    FileGrant Issue(FileOp op, Id16 channel, Id16 item, uint from, long nowMs);
    bool TryVerifyReceipt(string? token, long nowMs, out FileReceipt receipt);
}

public sealed class NoFileGateway : IFileGateway
{
    public static readonly NoFileGateway Instance = new();
    public bool Enabled => false;
    public string PublicUrl => "";
    public FileGrant Issue(FileOp op, Id16 channel, Id16 item, uint from, long nowMs) => throw new WebDropException(ErrorCode.NotFound);
    public bool TryVerifyReceipt(string? token, long nowMs, out FileReceipt receipt) { receipt = null!; return false; }
}