package com.zy.core.thread.support;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.LongSupplier;

public class RecentStationArrivalTracker {

    static final long DEFAULT_RETAIN_MS = 10_000L;

    private final long retainMs;
    private final LongSupplier nowSupplier;
    private final Map<Long, Long> arrivalTimeMap = new ConcurrentHashMap<>();
    private final AtomicLong lastCleanupAt = new AtomicLong(0L);

    public RecentStationArrivalTracker() {
        this(DEFAULT_RETAIN_MS, System::currentTimeMillis);
    }

    public RecentStationArrivalTracker(long retainMs, LongSupplier nowSupplier) {
        this.retainMs = retainMs <= 0L ? DEFAULT_RETAIN_MS : retainMs;
        this.nowSupplier = nowSupplier == null ? System::currentTimeMillis : nowSupplier;
    }

    public void observe(Integer stationId, Integer taskNo, boolean loading) {
        if (!loading) {
            return;
        }
        record(stationId, taskNo);
    }

    public void record(Integer stationId, Integer taskNo) {
        Long key = buildKey(stationId, taskNo);
        if (key == null) {
            return;
        }
        long now = nowSupplier.getAsLong();
        arrivalTimeMap.put(key, now);
        cleanupIfNeeded(now);
    }

    public boolean hasRecentArrival(Integer stationId, Integer taskNo) {
        Long key = buildKey(stationId, taskNo);
        if (key == null) {
            return false;
        }
        long now = nowSupplier.getAsLong();
        Long arrivalAt = arrivalTimeMap.get(key);
        if (arrivalAt == null) {
            cleanupIfNeeded(now);
            return false;
        }
        if (now - arrivalAt > retainMs) {
            arrivalTimeMap.remove(key, arrivalAt);
            cleanupIfNeeded(now);
            return false;
        }
        cleanupIfNeeded(now);
        return true;
    }

    private void cleanupIfNeeded(long now) {
        long lastCleanup = lastCleanupAt.get();
        if (now - lastCleanup < retainMs || !lastCleanupAt.compareAndSet(lastCleanup, now)) {
            return;
        }
        for (Map.Entry<Long, Long> entry : arrivalTimeMap.entrySet()) {
            if (entry == null || now - entry.getValue() <= retainMs) {
                continue;
            }
            arrivalTimeMap.remove(entry.getKey(), entry.getValue());
        }
    }

    private Long buildKey(Integer stationId, Integer taskNo) {
        if (stationId == null || stationId <= 0 || taskNo == null || taskNo <= 0) {
            return null;
        }
        return (((long) stationId) << 32) | (taskNo.longValue() & 0xffffffffL);
    }
}