namespace NewLife.Data;

/// <summary>数据过滤器</summary>
public interface IFilter
{
    /// <summary>下一个过滤器</summary>
    IFilter? Next { get; }

    /// <summary>对封包执行过滤器</summary>
    /// <param name="context"></param>
    void Execute(FilterContext context);
}

/// <summary>过滤器上下文</summary>
public class FilterContext
{
    /// <summary>封包</summary>
    public virtual Packet? Packet { get; set; }
}

/// <summary>过滤器助手</summary>
public static class FilterHelper
{
    /// <summary>在链条里面查找指定类型的过滤器</summary>
    /// <param name="filter"></param>
    /// <param name="filterType"></param>
    /// <returns></returns>
    public static IFilter? Find(this IFilter filter, Type filterType)
    {
        if (filter == null || filterType == null) return null;

        if (filter.GetType() == filterType) return filter;

        return filter.Next?.Find(filterType);
    }

    ///// <summary>在开头插入过滤器</summary>
    ///// <param name="filter"></param>
    ///// <param name="newFilter"></param>
    ///// <returns></returns>
    //public static IFilter Add(this IFilter filter, IFilter newFilter)
    //{
    //    if (filter == null || newFilter == null) return filter;

    //    newFilter.Next = filter;

    //    return newFilter;
    //}
}

/// <summary>数据过滤器基类</summary>
public abstract class FilterBase : IFilter
{
    /// <summary>下一个过滤器</summary>
    public IFilter? Next { get; set; }

    ///// <summary>实例化过滤器</summary>
    ///// <param name="next"></param>
    //public FilterBase(IFilter next) { Next = next; }

    /// <summary>对封包执行过滤器</summary>
    /// <param name="context"></param>
    public virtual void Execute(FilterContext context)
    {
        if (!OnExecute(context) || context.Packet == null) return;

        Next?.Execute(context);
    }

    /// <summary>执行过滤</summary>
    /// <param name="context"></param>
    /// <returns>返回是否执行下一个过滤器</returns>
    protected abstract Boolean OnExecute(FilterContext context);
}