typedef struct zskiplistNode {
    robj *member;          // 成員對(duì)象（如字符串）
    double score;          // 分?jǐn)?shù)（用于排序）
    struct zskiplistNode *backward; // 后退指針（雙向鏈表）
    struct zskiplistLevel {
        struct zskiplistNode *forward; // 前進(jìn)指針
        unsigned int span;  // 跨度（用于計(jì)算排名）
    } level[];             // 柔性數(shù)組，表示節(jié)點(diǎn)的層級(jí)
} zskiplistNode;
 
typedef struct zskiplist {
    struct zskiplistNode *header, *tail;
    unsigned long length;  // 節(jié)點(diǎn)數(shù)量
    int level;            // 當(dāng)前最大層數(shù)
} zskiplist;

int zslRandomLevel(void) {
    int level = 1;
    while ((random()&0xFFFF) < (ZSKIPLIST_P * 0xFFFF))
        level += 1;
    return (level<ZSKIPLIST_MAXLEVEL) ? level : ZSKIPLIST_MAXLEVEL;
}

import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.stereotype.Component;
 
import java.util.Collections;
import java.util.UUID;
 
@Component
public class SlidingWindowLimiter {
    
    private final RedisTemplate<String, String> redisTemplate;
    
    // Lua腳本（原子操作）
    private static final String LUA_SCRIPT = 
        "local key = KEYS[1]\n" +
        "local now = tonumber(ARGV[1])\n" +
        "local window = tonumber(ARGV[2])\n" +
        "local maxRequests = tonumber(ARGV[3])\n" +
        "local requestId = ARGV[4]\n" +
        "\n" +
        "-- 1. 移除窗口外的舊數(shù)據(jù)\n" +
        "redis.call('ZREMRANGEBYSCORE', key, 0, now - window)\n" +
        "\n" +
        "-- 2. 獲取當(dāng)前請(qǐng)求數(shù)\n" +
        "local count = redis.call('ZCARD', key)\n" +
        "\n" +
        "-- 3. 檢查是否超限\n" +
        "if count >= maxRequests then\n" +
        "    return 0\n" +
        "end\n" +
        "\n" +
        "-- 4. 記錄本次請(qǐng)求\n" +
        "redis.call('ZADD', key, now, requestId)\n" +
        "\n" +
        "-- 5. 刷新過(guò)期時(shí)間\n" +
        "redis.call('EXPIRE', key, window/1000 + 10)\n" +
        "return 1";
 
    public SlidingWindowLimiter(RedisTemplate<String, String> redisTemplate) {
        this.redisTemplate = redisTemplate;
    }
 
    /**
     * 檢查請(qǐng)求是否允許通過(guò)
     * @param key 限流鍵（如 user_123:api_pay）
     * @param windowMillis 窗口大小（毫秒）
     * @param maxRequests 窗口內(nèi)允許的最大請(qǐng)求數(shù)
     * @return true=允許, false=限流
     */
    public boolean allowRequest(String key, long windowMillis, int maxRequests) {
        // 構(gòu)造Redis Key
        String redisKey = "rate_limit:" + key;
        
        // 準(zhǔn)備腳本參數(shù)
        long currentTime = System.currentTimeMillis();
        String requestId = UUID.randomUUID().toString();
        
        // 執(zhí)行Lua腳本
        DefaultRedisScript<Long> script = new DefaultRedisScript<>(LUA_SCRIPT, Long.class);
        Long result = redisTemplate.execute(
            script,
            Collections.singletonList(redisKey),
            currentTime, windowMillis, maxRequests, requestId
        );
        
        return result != null && result == 1;
    }
}

@RestController
public class PaymentController {
    
    @Autowired
    private SlidingWindowLimiter limiter;
    
    @PostMapping("/pay")
    public ResponseEntity<?> createPayment(@RequestBody PaymentRequest request) {
        // 構(gòu)造限流鍵: 用戶ID + 接口名
        String key = "user_" + request.getUserId() + ":payment";
        
        // 檢查限流: 每用戶每分鐘最多10次支付
        if (!limiter.allowRequest(key, 60000, 10)) {
            return ResponseEntity.status(429).body("請(qǐng)求過(guò)于頻繁");
        }
        
        // 執(zhí)行業(yè)務(wù)邏輯
        paymentService.process(request);
        return ResponseEntity.ok("支付成功");
    }
}