philips-software/cogito

import Foundation
import BigInt
import SwiftyJSON

struct UnsignedTransaction {
    let from: Address
    let to: Address
    let data: Data
    let nonce: BigInt
    let gasPrice: BigInt
    let gasLimit: BigInt
    let value: BigInt
    let chainId: BigInt

    init?(from txDict: [String: Any]) {
        guard
            let from = takeAddress(from: txDict, key: "from"),
            let to = takeAddress(from: txDict, key: "to"),
            let gasPrice = takeNumber(from: txDict, key: "gasPrice"),
            let gasLimit = takeNumber(from: txDict, key: "gasLimit") ?? takeNumber(from: txDict, key: "gas"),
            let value = takeNumber(from: txDict, key: "value"),
            let nonce = takeNumber(from: txDict, key: "nonce"),
            let data = takeData(from: txDict, key: "data"),
            let chainId = takeNumber(from: txDict, key: "chainId")
        else {
            return nil
        }
        self.init(
            from: from,
            to: to,
            data: data,
            nonce: nonce,
            gasPrice: gasPrice,
            gasLimit: gasLimit,
            value: value,
            chainId: chainId
        )
    }

    init(
        from: Address,
        to: Address,
        data: Data,
        nonce: BigInt,
        gasPrice: BigInt,
        gasLimit: BigInt,
        value: BigInt,
        chainId: BigInt
    ) {
        self.from = from
        self.to = to
        self.data = data
        self.nonce = nonce
        self.gasPrice = gasPrice
        self.gasLimit = gasLimit
        self.value = value
        self.chainId = chainId
    }
}

private func takeAddress(from txDict: [String: Any], key: String) -> Address? {
    guard let addressString = txDict[key] as? String,
          let address = Address(fromHex: addressString) else {
        return nil
    }
    return address
}

private func takeNumber(from txDict: [String: Any], key: String) -> BigInt? {
    if let numberString = txDict[key] as? String,
       let number = BigInt(fromHex: numberString) {
        return number
    } else if let number = txDict[key] as? Int {
        return BigInt(exactly: number)
    }
    return nil
}

private func takeData(from txDict: [String: Any], key: String) -> Data? {
    guard let dataString = txDict[key] as? String,
          let data = Data(fromHex: dataString) else {
        return nil
    }
    return data
}

extension BigInt {
    init?(fromHex: String) {
        let hex: String
        if fromHex.hasPrefix("0x") {
            let after0x = fromHex.index(fromHex.startIndex, offsetBy: 2)
            hex = String(fromHex[after0x...])
        } else {
            hex = fromHex
        }
        guard hex.count > 0 else { return nil }

        self.init(hex, radix: 16)
    }
}