refactored automatic gas pricing algorithm to utilize the new Oracle, implement the new gas parameters, and take transaction type into account

fixes web3swift-team#546 by preserving the transaction type across the transaction rewrite

Author: mloit

Sources/web3swift/Web3/Web3+MutatingTransaction.swift

@@ -73,6 +73,9 @@ public class WriteTransaction: ReadTransaction {
             optionsForGasEstimation.value = mergedOptions.value
             optionsForGasEstimation.gasLimit = mergedOptions.gasLimit
             optionsForGasEstimation.callOnBlock = mergedOptions.callOnBlock
+            optionsForGasEstimation.type = mergedOptions.type
+            optionsForGasEstimation.accessList = mergedOptions.accessList
+
 
             // assemble promise for gasLimit
             var gasEstimatePromise: Promise<BigUInt>? = nil
@@ -102,20 +105,75 @@ public class WriteTransaction: ReadTransaction {
                 getNoncePromise = Promise<BigUInt>.value(nonce)
             }
 
-            // assemble promise for gasPrice
-            var gasPricePromise: Promise<BigUInt>? = nil
-            guard let gasPricePolicy = mergedOptions.gasPrice else {
-                seal.reject(Web3Error.inputError(desc: "No gasPrice policy provided"))
-                return
-            }
-            switch gasPricePolicy {
-            case .automatic, .withMargin:
-                gasPricePromise = self.web3.eth.getGasPricePromise()
-            case .manual(let gasPrice):
-                gasPricePromise = Promise<BigUInt>.value(gasPrice)
+            // determine gas costing, taking transaction type into account
+            let oracle = Web3.Oracle(self.web3, percentiles: [75])
+            let finalGasPrice: BigUInt? // legacy gas model
+            let finalGasFee: BigUInt? // EIP-1559 gas model
+            let finalTipFee: BigUInt? // EIP-1559 gas model
+
+            if mergedOptions.type == nil || mergedOptions.type != .eip1559 { // legacy Gas
+                // set unused gas parameters to nil
+                finalGasFee = nil
+                finalTipFee = nil
+
+                // determine the (legacy) gas price
+                guard let gasPricePolicy = mergedOptions.gasPrice else {
+                    seal.reject(Web3Error.inputError(desc: "No gasPrice policy provided"))
+                    return
+                }
+                switch gasPricePolicy {
+                case .automatic, .withMargin:
+                    let percentiles = oracle.gasPriceLegacyPercentiles
+                    guard !percentiles.isEmpty else {
+                        throw Web3Error.processingError(desc: "Failed to fetch gas price")
+                    }
+                    finalGasPrice = percentiles[0]
+                case .manual(let gasPrice):
+                    finalGasPrice = gasPrice
+                }
+            } else { // else new gas fees (EIP-1559)
+                // set unused gas parametes to nil
+                finalGasPrice = nil
+
+                // determine the tip
+                guard let maxPriorityFeePerGasPolicy = mergedOptions.maxPriorityFeePerGas else {
+                    seal.reject(Web3Error.inputError(desc: "No maxPriorityFeePerGas policy provided"))
+                    return
+                }
+                switch maxPriorityFeePerGasPolicy {
+                case .automatic:
+                    let percentiles = oracle.tipFeePercentiles
+                    guard !percentiles.isEmpty else {
+                        throw Web3Error.processingError(desc: "Failed to fetch maxPriorityFeePerGas data")
+                    }
+                    finalTipFee = percentiles[0]
+                case .manual(let maxPriorityFeePerGas):
+                    finalTipFee = maxPriorityFeePerGas
+                }
+
+                // determine the baseFee, and calculate the maxFeePerGas
+                guard let maxFeePerGasPolicy = mergedOptions.maxFeePerGas else {
+                    seal.reject(Web3Error.inputError(desc: "No maxFeePerGas policy provided"))
+                    return
+                }
+                switch maxFeePerGasPolicy {
+                case .automatic:
+                    let percentiles = oracle.baseFeePercentiles
+                    guard !percentiles.isEmpty else {
+                        throw Web3Error.processingError(desc: "Failed to fetch baseFee data")
+                    }
+                    guard let tipFee = finalTipFee else {
+                        throw Web3Error.processingError(desc: "Missing tip value")
+                    }
+                    finalGasFee = percentiles[0] + tipFee
+                case .manual(let maxFeePerGas):
+                    finalGasFee = maxFeePerGas
+                }
             }
-            var promisesToFulfill: [Promise<BigUInt>] = [getNoncePromise!, gasPricePromise!, gasEstimatePromise!]
-            when(resolved: getNoncePromise!, gasEstimatePromise!, gasPricePromise!).map(on: queue, { (results: [PromiseResult<BigUInt>]) throws -> EthereumTransaction in
+
+            // wait for promises to resolve
+            var promisesToFulfill: [Promise<BigUInt>] = [getNoncePromise!, gasEstimatePromise!]
+            when(resolved: getNoncePromise!, gasEstimatePromise!).map(on: queue, { (results: [PromiseResult<BigUInt>]) throws -> EthereumTransaction in
 
                 promisesToFulfill.removeAll()
                 guard case .fulfilled(let nonce) = results[0] else {
@@ -124,17 +182,25 @@ public class WriteTransaction: ReadTransaction {
                 guard case .fulfilled(let gasEstimate) = results[1] else {
                     throw Web3Error.processingError(desc: "Failed to fetch gas estimate")
                 }
-                guard case .fulfilled(let gasPrice) = results[2] else {
-                    throw Web3Error.processingError(desc: "Failed to fetch gas price")
-                }
-
-                let estimate = mergedOptions.resolveGasLimit(gasEstimate)
-                let finalGasPrice = mergedOptions.resolveGasPrice(gasPrice)
 
                 var finalOptions = TransactionOptions()
+                finalOptions.type = mergedOptions.type
                 finalOptions.nonce = .manual(nonce)
-                finalOptions.gasLimit = .manual(estimate)
-                finalOptions.gasPrice = .manual(finalGasPrice)
+                finalOptions.gasLimit = .manual(mergedOptions.resolveGasLimit(gasEstimate))
+                finalOptions.accessList = mergedOptions.accessList
+
+                // set the finalized gas parameters
+                if let gasPrice = finalGasPrice {
+                    finalOptions.gasPrice = .manual(mergedOptions.resolveGasPrice(gasPrice))
+                }
+
+                if let tipFee = finalTipFee {
+                    finalOptions.maxPriorityFeePerGas = .manual(mergedOptions.resolveMaxPriorityFeePerGas(tipFee))
+                }
+
+                if let gasFee = finalGasFee {
+                    finalOptions.maxFeePerGas = .manual(mergedOptions.resolveMaxFeePerGas(gasFee))
+                }
 
                 assembledTransaction.applyOptions(finalOptions)