package com.example.redissetrandomget.lottery;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("/api/lottery")
public class LotteryController {

    private final LotteryService lotteryService;

    public LotteryController(LotteryService lotteryService) {
        this.lotteryService = lotteryService;
    }

    // 加入抽獎者（支持批量）
    @RequestMapping(path = "/add", method = {RequestMethod.GET, RequestMethod.POST})
    public String add(@RequestParam String activityId, @RequestParam String[] userIds) {
        lotteryService.addParticipants(activityId, userIds);
        long remainCount = lotteryService.getRemainCount(activityId);
        return "成功加入獎池！當前獎池總?cè)藬?shù)：" + remainCount;
    }

    // 抽核心大獎（抽完即踢出獎池，絕對不重復中獎）
    @GetMapping("/drawGrand")
    public List<String> drawGrand(@RequestParam String activityId, @RequestParam long count) {
        return lotteryService.drawGrandPrize(activityId, count);
    }
    
    // 抽幸運參與獎（抽完保留在獎池，下次還有機會）
    @GetMapping("/drawSunshine")
    public List<String> drawSunshine(@RequestParam String activityId, @RequestParam long count) {
        return lotteryService.drawSunshinePrize(activityId, count);
    }
    
    // 查詢獎池剩余人數(shù)
    @GetMapping("/remain")
    public long remain(@RequestParam String activityId) {
        return lotteryService.getRemainCount(activityId);
    }
}

package com.example.redissetrandomget.lottery;

import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

import java.util.Arrays;
import java.util.List;

@Service
public class LotteryService {

    private static final String LOTTERY_KEY_PREFIX = "lottery:activity:";
    private final StringRedisTemplate redisTemplate;

    public LotteryService(StringRedisTemplate redisTemplate) {
        this.redisTemplate = redisTemplate;
    }

    public void addParticipants(String activityId, String... userIds) {
        redisTemplate.opsForSet().add(buildKey(activityId), normalizeUserIds(userIds));
    }

    // 使用 pop：隨機抽取并移除（適用于大獎）
    public List<String> drawGrandPrize(String activityId, long count) {
        validateCount(count);
        List<String> winners = redisTemplate.opsForSet().pop(buildKey(activityId), count);
        return winners != null ? winners : List.of();
    }

    // 使用 randomMembers：隨機抽取但不移除（適用于陽光普照獎）
    public List<String> drawSunshinePrize(String activityId, long count) {
        validateCount(count);
        List<String> winners = redisTemplate.opsForSet().randomMembers(buildKey(activityId), count);
        return winners != null ? winners : List.of();
    }

    public long getRemainCount(String activityId) {
        Long size = redisTemplate.opsForSet().size(buildKey(activityId));
        return size != null ? size : 0L;
    }

    public void joinLottery(String activityId, String... userIds) {
        addParticipants(activityId, userIds);
    }

    public List<String> drawWithoutRepeat(String activityId, long count) {
        return drawGrandPrize(activityId, count);
    }

    public List<String> drawWithRepeat(String activityId, long count) {
        return drawSunshinePrize(activityId, count);
    }

    public long participantCount(String activityId) {
        return getRemainCount(activityId);
    }

    // --- 私有輔助方法 ---

    private void validateCount(long count) {
        Assert.isTrue(count > 0, "抽獎人數(shù)必須大于 0");
    }

    private String buildKey(String activityId) {
        Assert.hasText(activityId, "活動 ID 不能為空");
        return LOTTERY_KEY_PREFIX + activityId.trim();
    }

    private String[] normalizeUserIds(String[] userIds) {
        Assert.notEmpty(userIds, "用戶列表不能為空");

        String[] normalizedUserIds = Arrays.stream(userIds)
                .filter(StringUtils::hasText)
                .map(String::trim)
                .distinct()
                .toArray(String[]::new);

        Assert.notEmpty(normalizedUserIds, "過濾后沒有合法的用戶 ID");
        return normalizedUserIds;
    }
}

GET http://localhost:8080/api/lottery/drawGrand?activityId=2026&count=2

HTTP/1.1 200 
Content-Type: application/json
Date: Fri, 13 Mar 2026 08:54:20 GMT

[
  "3",
  "5"
]

GET http://localhost:8080/api/lottery/drawSunshine?activityId=2026&count=2

HTTP/1.1 200 
Content-Type: application/json
Date: Fri, 13 Mar 2026 08:56:28 GMT

[
  "2",
  "2"
]