using System.Collections.Concurrent;

namespace MES.Service.util;

public static class LinqThreadSafeExtensions
{
    // 线程安全版本（基于ConcurrentDictionary）
    public static Func<T, bool> DistinctByKey<T, TKey>(
        Func<T, TKey> keySelector)
    {
        var seen = new ConcurrentDictionary<TKey, bool>();
        return item => seen.TryAdd(keySelector(item), true);
    }

    // 扩展方法版本（推荐）
    public static IEnumerable<T> DistinctByConcurrent<T, TKey>(
        this IEnumerable<T> source,
        Func<T, TKey> keySelector)
    {
        var seen = new ConcurrentDictionary<TKey, bool>();
        return source.Where(item => seen.TryAdd(keySelector(item), true));
    }
}