Merge pull request #108 from dangershony/fee-policy-observer

Light wallet fee estimator to use hard coded values

Breeze/src/Breeze.Wallet/WalletFeePolicy.cs

@@ -9,36 +9,28 @@ namespace Breeze.Wallet
 
     public class LightWalletFeePolicy : IWalletFeePolicy
     {
-        private readonly BlockPolicyEstimator blockPolicyEstimator;
-
-        private readonly Money maxTxFee;
-
-        /// <summary>
-        ///  Fees smaller than this (in satoshi) are considered zero fee (for transaction creation)
-        ///  Override with -mintxfee
-        /// </summary>
         private readonly FeeRate minTxFee;
+        private readonly Money maxTxFee;
+        private readonly FeeRate highxFeePerKb;
+        private readonly FeeRate mediumTxFeePerKb;
+        private readonly FeeRate lowTxFeePerKb;
 
-        /// <summary>
-        ///  If fee estimation does not have enough data to provide estimates, use this fee instead.
-        ///  Has no effect if not using fee estimation
-        ///  Override with -fallbackfee
-        /// </summary>
-        private readonly FeeRate fallbackFee;
-
-        /// <summary>
-        /// Transaction fee set by the user
-        /// </summary>
-        private readonly FeeRate payTxFee;
-
-        public LightWalletFeePolicy(BlockPolicyEstimator blockPolicyEstimator)
+        public LightWalletFeePolicy()
         {
-            this.blockPolicyEstimator = blockPolicyEstimator;
-
-            this.minTxFee = new FeeRate(1000);
-            this.fallbackFee = new FeeRate(20000);
-            this.payTxFee = new FeeRate(0);
+            // when estimating the fee, the fee of each transactions needs to be knowen
+            // as this is an estimator on a light wallet we dont have the UTXO set
+            // that leaves with few options:
+            // - an external service, 
+            // - hard code fee per kb
+            // - we may even be able to monitor the size of the mempool (mini mempool)
+            // (not the entire trx) and try to estimate based on pending count
+            // TODO: make fee values confugurable on startup
+
+            this.highxFeePerKb = new FeeRate(385939);
+            this.mediumTxFeePerKb = new FeeRate(245347);
+            this.lowTxFeePerKb = new FeeRate(171274);
             this.maxTxFee = new Money(0.1M, MoneyUnit.BTC);
+            this.minTxFee = new FeeRate(1000);
         }
 
         public Money GetRequiredFee(int txBytes)
@@ -49,27 +41,23 @@ namespace Breeze.Wallet
         public Money GetMinimumFee(int txBytes, int confirmTarget)
         {
             // payTxFee is the user-set global for desired feerate
-            return this.GetMinimumFee(txBytes, confirmTarget, this.payTxFee.GetFee(txBytes));
+            return this.GetMinimumFee(txBytes, confirmTarget, this.lowTxFeePerKb.GetFee(txBytes));
         }
 
         public Money GetMinimumFee(int txBytes, int confirmTarget, Money targetFee)
         {
-            Money nFeeNeeded = targetFee;
-            // User didn't set: use -txconfirmtarget to estimate...
-            if (nFeeNeeded == 0)
-            {
-                int estimateFoundTarget = confirmTarget;
-                nFeeNeeded = this.blockPolicyEstimator.EstimateSmartFee(confirmTarget, null, out estimateFoundTarget).GetFee(txBytes);
-                // ... unless we don't have enough mempool data for estimatefee, then use fallbackFee
-                if (nFeeNeeded == 0)
-                    nFeeNeeded = this.fallbackFee.GetFee(txBytes);
-            }
+            Money feeNeeded = targetFee;
+            
+            feeNeeded = this.lowTxFeePerKb.GetFee(txBytes);
+            if (confirmTarget < 50) feeNeeded = this.mediumTxFeePerKb.GetFee(txBytes);
+            if (confirmTarget < 20) feeNeeded = this.highxFeePerKb.GetFee(txBytes);
+
             // prevent user from paying a fee below minRelayTxFee or minTxFee
-            nFeeNeeded = Math.Max(nFeeNeeded, this.GetRequiredFee(txBytes));
+            feeNeeded = Math.Max(feeNeeded, this.GetRequiredFee(txBytes));
             // But always obey the maximum
-            if (nFeeNeeded > this.maxTxFee)
-                nFeeNeeded = this.maxTxFee;
-            return nFeeNeeded;
+            if (feeNeeded > this.maxTxFee)
+                feeNeeded = this.maxTxFee;
+            return feeNeeded;
         }
     }
 }