Gas price index on a 7-day cycle

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/Decentralized.Domain/Tuning.cs

@@ -144,6 +144,9 @@ namespace Decentralized.Domain
 
         /// <summary>转账手续费（信用点等值，按转出的币扣）：慢 / 普通 / 快；拥堵时乘以倍数。</summary>
         public const double TxFeeSlow = 0.5, TxFeeNormal = 1.5, TxFeeFast = 4, TxCongestedFeeMult = 4;
+        /// <summary>Gas 价格指数：以 GasPeriod 天为周期正弦涨跌，振幅 GasAmp（0.5×–1.5×），每天再乘 1 ± GasNoise 的随机波动。</summary>
+        public const int TxGasPeriod = 7;
+        public const double TxGasAmp = 0.5, TxGasNoise = 0.15;
         /// <summary>网络拥堵：每晚开始拥堵的概率、持续天数上限；拥堵时普通档、慢档的确认间隔倍数，慢档被挤出内存池的概率。</summary>
         public const double TxCongestionChance = 0.12, TxCongestedNormalSlow = 2, TxCongestedSlowSlow = 3.5, TxSlowDrop = 0.3;
         public const int TxCongestionDaysMax = 2;

src/Decentralized.Domain/TxRules.cs

@@ -18,8 +18,14 @@ namespace Decentralized.Domain
     public static class TxRules
     {
         /// <summary>手续费（信用点等值，按转出的币扣）：档位基础价 × 拥堵倍数。</summary>
-        public static double FeeCredits(FeeTier t, bool congested) =>
-            (t == FeeTier.Slow ? Tuning.TxFeeSlow : t == FeeTier.Normal ? Tuning.TxFeeNormal : Tuning.TxFeeFast) * (congested ? Tuning.TxCongestedFeeMult : 1);
+        public static double FeeCredits(FeeTier t, bool congested, double gas = 1) =>
+            (t == FeeTier.Slow ? Tuning.TxFeeSlow : t == FeeTier.Normal ? Tuning.TxFeeNormal : Tuning.TxFeeFast) * gas * (congested ? Tuning.TxCongestedFeeMult : 1);
+
+        /// <summary>Gas 周期部分：phase 是这一局的起始相位（0..周期-1）。</summary>
+        public static double GasCycle(int day, int phase) => 1 + Tuning.TxGasAmp * System.Math.Sin(2 * System.Math.PI * (day + phase) / Tuning.TxGasPeriod);
+
+        /// <summary>某天的 gas 指数：周期 × (1 ± 随机波动)。</summary>
+        public static double Gas(int day, int phase, Rng rng) => GasCycle(day, phase) * (1 + Tuning.TxGasNoise * (rng.NextDouble() * 2 - 1));
 
         /// <summary>需要的确认数：金额越大越多。</summary>
         public static int Confirmations(double valueCredits) =>