发红包优化

src/main/java/com/tailbet/service/impl/RedPacketServiceImpl.java

@@ -176,7 +176,7 @@ public class RedPacketServiceImpl implements IRedPacketService {
         if (currentLucky == null || amount.compareTo(currentLucky) > 0) {
             rp.setLuckyAmount(amount);
             rp.setLuckyUserId(userId);
-            rp.setLuckyDigit(amount.remainder(BigDecimal.TEN).intValue());
+            rp.setLuckyDigit(digitOf(amount));
         }
         rp.setShareTakenIndex(takenIndex != null ? takenIndex + 1 : 1);
 
@@ -358,7 +358,31 @@ public class RedPacketServiceImpl implements IRedPacketService {
         }
 
         // 3. 其他人金额（带小随机波动）
+        // 计算 avgAmount 后，确保 luckyAmount ≥ avgAmount × 1.2（maxFactor）
+        // 这样循环里的 amount 自然 ≤ luckyAmount，无需钳制，金额严格守恒
+        double maxFactor = 1.2;
         BigDecimal avgAmount = remaining.divide(BigDecimal.valueOf(count - 1), 2, RoundingMode.HALF_UP);
+        BigDecimal needed = avgAmount.multiply(BigDecimal.valueOf(maxFactor))
+                .setScale(2, RoundingMode.HALF_UP);
+        if (luckyAmount.compareTo(needed) < 0) {
+            // 手气王不够大，抬高到 needed（满足"分位尾数"=targetDigit 优先）
+            BigDecimal lifted = needed;
+            if (targetDigit != null) {
+                lifted = adjustToTargetDigit(lifted, total, targetDigit);
+            }
+            // 若抬高后超过 luckyMax（total - minForOthers），回退取 luckyMax 并再调尾数
+            BigDecimal cap = total.subtract(minForOthers);
+            if (lifted.compareTo(cap) > 0) {
+                lifted = cap;
+                if (targetDigit != null) {
+                    lifted = adjustToTargetDigit(lifted, cap, targetDigit);
+                }
+            }
+            luckyAmount = lifted;
+            remaining = total.subtract(luckyAmount);
+            // 重新计算 avgAmount，确保循环里的金额仍 ≥ minUnit
+            avgAmount = remaining.divide(BigDecimal.valueOf(count - 1), 2, RoundingMode.HALF_UP);
+        }
         amounts.add(luckyAmount);
 
         BigDecimal remainingForOthers = remaining;
@@ -370,15 +394,19 @@ public class RedPacketServiceImpl implements IRedPacketService {
             if (amount.compareTo(minUnit) < 0) {
                 amount = minUnit;
             }
-            // 上限保护：不超过剩余
+            // 累加上限：不超过 remainingForOthers
             if (amount.compareTo(remainingForOthers) > 0) {
                 amount = remainingForOthers;
             }
             amounts.add(amount);
             remainingForOthers = remainingForOthers.subtract(amount);
         }
-        // 最后一个拿剩余（下限保护）
+        // 最后一个拿剩余
-        BigDecimal last = remainingForOthers.compareTo(minUnit) < 0 ? minUnit : remainingForOthers;
+        BigDecimal last = remainingForOthers;
+        // 下限保护：累减后可能 < minUnit
+        if (last.compareTo(minUnit) < 0) {
+            last = minUnit;
+        }
         amounts.add(last.setScale(2, RoundingMode.HALF_UP));
 
         // 打乱顺序（让领取顺序随机）
@@ -394,8 +422,9 @@ public class RedPacketServiceImpl implements IRedPacketService {
 
     /**
      * 计算手气王金额
-     * - 比例为总额的30%~50%
+     * - 比例为总额的 [1/count, 50%]，下限定为 1/count 以保证 luckyAmount ≥ avgAmount
-     * - 有目标尾数时确保尾数=targetDigit
+     *   （手气王必须 ≥ 其他人的平均金额，否则随机波动后有人会比手气王还大）
+     * - 有目标尾数时确保"分位尾数"=targetDigit
      * - 不超过 luckyMax（total - minUnit * (count-1)），留出最小份额给其他人
      */
     private BigDecimal calculateLuckyAmount(BigDecimal total, Integer targetDigit, int totalCount, Random random) {
@@ -403,8 +432,9 @@ public class RedPacketServiceImpl implements IRedPacketService {
         BigDecimal minForOthers = minUnit.multiply(BigDecimal.valueOf(totalCount - 1));
         BigDecimal luckyMax = total.subtract(minForOthers);
 
-        // 比例：总额的30%~50%
+        // 比例下限 1/count（保证 luckyAmount ≥ avgAmount），上限 50%
-        double ratio = 0.3 + random.nextDouble() * 0.2;
+        double minRatio = 1.0 / totalCount;
+        double ratio = minRatio + random.nextDouble() * (0.5 - minRatio);
         BigDecimal luckyAmount = total.multiply(BigDecimal.valueOf(ratio))
                 .setScale(2, RoundingMode.HALF_UP);
 
@@ -425,22 +455,24 @@ public class RedPacketServiceImpl implements IRedPacketService {
     }
 
     /**
-     * 调整金额让尾数=targetDigit，且不超过 maxAllowed
+     * 调整金额让"分位尾数"=targetDigit，且不超过 maxAllowed
      * 优先向上调整（保持金额更大），如会超出则向下调整
      */
     private BigDecimal adjustToTargetDigit(BigDecimal amount, BigDecimal maxAllowed, int targetDigit) {
         BigDecimal minUnit = new BigDecimal("0.01");
-        int lastDigit = amount.remainder(BigDecimal.TEN).intValue();
+        int lastDigit = digitOf(amount);
         if (lastDigit == targetDigit) {
             return amount;
         }
-        int upDiff = (targetDigit - lastDigit + 10) % 10;       // 向上调
+        int upDiff = (targetDigit - lastDigit + 10) % 10;       // 向上调（单位：分）
         int downDiff = (lastDigit - targetDigit + 10) % 10;     // 向下调
-        BigDecimal up = amount.add(BigDecimal.valueOf(upDiff)).setScale(2, RoundingMode.HALF_UP);
+        BigDecimal up = amount.add(BigDecimal.valueOf(upDiff).movePointLeft(2))
+                .setScale(2, RoundingMode.HALF_UP);
         if (up.compareTo(maxAllowed) <= 0 && up.compareTo(minUnit) >= 0) {
             return up;
         }
-        BigDecimal down = amount.subtract(BigDecimal.valueOf(downDiff)).setScale(2, RoundingMode.HALF_UP);
+        BigDecimal down = amount.subtract(BigDecimal.valueOf(downDiff).movePointLeft(2))
+                .setScale(2, RoundingMode.HALF_UP);
         if (down.compareTo(minUnit) >= 0) {
             return down;
         }
@@ -448,22 +480,30 @@ public class RedPacketServiceImpl implements IRedPacketService {
     }
 
     /**
-     * 确保份额列表中至少有1个金额的尾数=targetDigit
+     * 取金额的"分位尾数"：金额×100 后取个位（如 0.45→5，1.05→5，0.40→0）
-     * 若没有则从列表中找一个尾数匹配的金额,换到首位作为手气王
+     * BigDecimal.remainder(BigDecimal.TEN) 对小数返回自身+intValue 截断会丢精度，
+     * 这里按国内红包/微信红包标准按"分位"算尾数
      */
+    private static int digitOf(BigDecimal amount) {
+        if (amount == null) return 0;
+        return amount.movePointRight(2).remainder(BigDecimal.TEN).intValue();
+    }
+
+    /**
+ * 确保 amounts[0] 的"分位尾数"=targetDigit（手气王必须在首位）
+ * 如果首位已经命中则不操作；否则找一个命中项 swap 到首位；都没有则兜底不动
+ */
     private void ensureLuckyDigit(List<BigDecimal> amounts, int targetDigit) {
-        for (BigDecimal amt : amounts) {
+        if (digitOf(amounts.get(0)) == targetDigit) {
-            if (amt.remainder(BigDecimal.TEN).intValue() == targetDigit) {
+            return;
-                return;
-            }
         }
-        // 没有尾数匹配的,找一个换到首位
+        // 首位不命中，找一个命中项 swap 到首位
         for (int i = 1; i < amounts.size(); i++) {
-            BigDecimal amt = amounts.get(i);
+            if (digitOf(amounts.get(i)) == targetDigit) {
-            if (amt.remainder(BigDecimal.TEN).intValue() == targetDigit) {
+                Collections.swap(amounts, 0, i);
-                Collections.swap(amounts, i, 0);
                 return;
             }
         }
+        // 没有任何命中项，无法保证（这种情况很罕见：total/count 太小无空间调整）
     }
 }