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| 1 | +// |
| 2 | +// Web3+GasOracle.swift |
| 3 | +// web3swift |
| 4 | +// |
| 5 | +// Created by Yaroslav on 31.03.2022. |
| 6 | +// Copyright © 2022 web3swift. All rights reserved. |
| 7 | +// |
| 8 | + |
| 9 | +import Foundation |
| 10 | +import BigInt |
| 11 | + |
| 12 | +extension Web3 { |
| 13 | + /// Oracle is the class to of a transaction fee suggestion |
| 14 | + /// |
| 15 | + /// It designed for EIP-1559 transactions only. |
| 16 | + final public class Oracle { |
| 17 | + private var latestBlock: Block? |
| 18 | + |
| 19 | + /// Web3 provider by wich accessing to the blockchain |
| 20 | + private let web3Provider: web3 |
| 21 | + |
| 22 | + /// Ethereum scope shortcut |
| 23 | + private var eth: web3.Eth { web3Provider.eth } |
| 24 | + |
| 25 | + /// Number of block to caltulate statistics |
| 26 | + public private(set) var blocksNumber: BigUInt |
| 27 | + |
| 28 | + /// Number of transacrtions to filter block for tip calculation |
| 29 | + public private(set) var transactionsNumber: BigUInt |
| 30 | + |
| 31 | + /// Oracle initializer |
| 32 | + /// - Parameters: |
| 33 | + /// - provider: Web3 Ethereum provider |
| 34 | + /// - blocksNumber: Number of block to caltulate statistics |
| 35 | + public init(_ provider: web3, blocksNumber: BigUInt = 20, transactionsNumber: BigUInt = 50) { |
| 36 | + web3Provider = provider |
| 37 | + self.blocksNumber = blocksNumber |
| 38 | + self.transactionsNumber = transactionsNumber |
| 39 | + } |
| 40 | + |
| 41 | + private func calcBaseFee(for block: Block?) -> BigUInt { |
| 42 | + guard let block = block else { return 0 } |
| 43 | + return Web3.calcBaseFee(block) |
| 44 | + } |
| 45 | + |
| 46 | + private func calculateStatistic(_ data: [BigUInt], _ statistic: Statistic) throws -> BigUInt { |
| 47 | + let sortedData = data.sorted() |
| 48 | + let noAnomalyArray = sortedData.cropAnomalyValues() |
| 49 | + |
| 50 | + guard !noAnomalyArray.isEmpty else { throw Web3Error.unknownError } |
| 51 | + |
| 52 | + switch statistic { |
| 53 | + // Force unwrapping is ok, since array checked for epmtiness above |
| 54 | + case .minimum: return noAnomalyArray.min()! |
| 55 | + case .mean: return noAnomalyArray.mean()! |
| 56 | + case .median: return noAnomalyArray.median()! |
| 57 | + case .maximum: |
| 58 | + // Checking that suggestedBaseFee are not lower than next |
| 59 | + // because in tne maximum statistic we should guarantee that transaction would pass in the next block |
| 60 | + return max(calcBaseFee(for: latestBlock), noAnomalyArray.max()!) |
| 61 | + } |
| 62 | + } |
| 63 | + |
| 64 | + private func suggestTipValue(_ statistic: Statistic) throws -> BigUInt { |
| 65 | + let latestBlockNumber = try eth.getBlockNumber() |
| 66 | + |
| 67 | + // TODO: Make me work with cache |
| 68 | + var block: Block |
| 69 | + |
| 70 | + repeat { |
| 71 | + block = try eth.getBlockByNumber(latestBlockNumber, fullTransactions: true) |
| 72 | + } while block.transactions.count < transactionsNumber |
| 73 | + |
| 74 | + // Storing last block to calculate baseFee of the next block |
| 75 | + latestBlock = block |
| 76 | + |
| 77 | + let transactionsTips = block.transactions |
| 78 | + .compactMap { t -> EthereumTransaction? in |
| 79 | + guard case let .transaction(transaction) = t else { return nil } |
| 80 | + return transaction |
| 81 | + } |
| 82 | + // TODO: Add filter for transaction types |
| 83 | + .map { $0.maxPriorityFeePerGas } |
| 84 | + |
| 85 | + return try calculateStatistic(transactionsTips, statistic) |
| 86 | + } |
| 87 | + |
| 88 | + private func suggestBaseFee(_ statistic: Statistic) throws -> BigUInt { |
| 89 | + let latestBlockNumber = try eth.getBlockNumber() |
| 90 | + |
| 91 | + // Assigning last block to object var to predict baseFee of the next block |
| 92 | + latestBlock = try eth.getBlockByNumber(latestBlockNumber) |
| 93 | + // TODO: Make me work with cache |
| 94 | + let lastNthBlocksBaseFees = try (latestBlockNumber - blocksNumber ... latestBlockNumber) |
| 95 | + .map { try eth.getBlockByNumber($0) } |
| 96 | + .filter { !$0.transactions.isEmpty } |
| 97 | + .map { $0.baseFeePerGas } |
| 98 | + |
| 99 | + return try calculateStatistic(lastNthBlocksBaseFees, statistic) |
| 100 | + } |
| 101 | + } |
| 102 | +} |
| 103 | + |
| 104 | +public extension Web3.Oracle { |
| 105 | + // MARK: - Base Fee |
| 106 | + /// Base fee amount based on last Nth blocks |
| 107 | + /// |
| 108 | + /// Normalized means that most high and most low value were droped from calculation. |
| 109 | + /// |
| 110 | + /// Nth block may include empty ones. |
| 111 | + /// |
| 112 | + /// - Parameter statistic: Statistic to apply for base fee calculation |
| 113 | + /// - Returns: Suggested base fee amount according to statistic, nil if failed to perdict |
| 114 | + func predictBaseFee(_ statistic: Statistic) -> BigUInt? { |
| 115 | + guard let value = try? suggestBaseFee(statistic) else { return nil } |
| 116 | + return value |
| 117 | + } |
| 118 | + |
| 119 | + // MARK: - Tip |
| 120 | + /// Maximum tip amount based on last block tips |
| 121 | + /// |
| 122 | + /// Normalized means that most high and most low value were droped from calculation. |
| 123 | + /// |
| 124 | + /// Account first of the latest block that have more than `transactionsNumber` value. |
| 125 | + /// |
| 126 | + /// - Parameter statistic: Statistic to apply for tip calculation |
| 127 | + /// - Returns: Suggested tip amount according to statistic, nil if failed to perdict |
| 128 | + func predictTip(_ statistic: Statistic) -> BigUInt? { |
| 129 | + guard let value = try? suggestTipValue(statistic) else { return nil } |
| 130 | + return value |
| 131 | + } |
| 132 | + |
| 133 | + // MARK: - Summary fees |
| 134 | + /// Method to get summary fees |
| 135 | + /// - Parameters: |
| 136 | + /// - baseFee: Statistic to apply for baseFee |
| 137 | + /// - tip: Statistic to apply for tip |
| 138 | + /// - Returns: Touple where [0] — base fee, [1] — tip, nil if failed to predict |
| 139 | + func predictBothFees(baseFee: Statistic, tip: Statistic) -> (BigUInt, BigUInt)? { |
| 140 | + guard let baseFee = try? suggestBaseFee(baseFee) else { return nil } |
| 141 | + guard let tip = try? suggestTipValue(tip) else { return nil } |
| 142 | + |
| 143 | + return (baseFee, tip) |
| 144 | + } |
| 145 | +} |
| 146 | + |
| 147 | +public extension Web3.Oracle { |
| 148 | + // TODO: Make me struct and incapsulate math within to make me extendable |
| 149 | + enum Statistic { |
| 150 | + /// Mininum statistic |
| 151 | + case minimum |
| 152 | + /// Mean statistic |
| 153 | + case mean |
| 154 | + /// Median statistic |
| 155 | + case median |
| 156 | + /// Maximum statistic |
| 157 | + case maximum |
| 158 | + } |
| 159 | +} |
| 160 | + |
| 161 | +extension Array { |
| 162 | + func cropAnomalyValues() -> Self { |
| 163 | + var tmpArr = self.dropFirst() |
| 164 | + tmpArr = self.dropLast() |
| 165 | + return Array(tmpArr) |
| 166 | + } |
| 167 | +} |
| 168 | + |
| 169 | +extension Array where Element: BinaryInteger { |
| 170 | + func mean() -> BigUInt? { |
| 171 | + guard !self.isEmpty else { return nil } |
| 172 | + return BigUInt(self.reduce(0, +)) / BigUInt(self.count) |
| 173 | + } |
| 174 | + |
| 175 | + func median() -> BigUInt? { |
| 176 | + guard !self.isEmpty else { return nil } |
| 177 | + |
| 178 | + let sorted_data = self.sorted() |
| 179 | + if self.count % 2 == 1 { |
| 180 | + return BigUInt(sorted_data[Int(floor(Double(self.count) / 2))]) |
| 181 | + } else { |
| 182 | + return BigUInt(sorted_data[self.count / 2] + sorted_data[(self.count / 2) - 1] / 2) |
| 183 | + } |
| 184 | + } |
| 185 | +} |
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