Learning-Bitcoin-from-the-Command-Line/src/17_6_sendtx.playground

import Foundation

func makeCommand(method: String, param: Any, completionHandler: @escaping (Any?) -> Void) -> Void {
    
// 1. Build a URL
    
    let testnetRpcPort = "18332"
    let nodeIp = "127.0.0.1:\(testnetRpcPort)"
    let rpcusername = "oIjA53JC2u"
    let rpcpassword = "ebVCeSyyM0LurvgQyi0exWTqm4oU0rZU"
    let walletName = ""
    let walletUrl = "http://\(rpcusername):\(rpcpassword)@\(nodeIp)/\(walletName)"

    let url = URL(string: walletUrl)

// 2. Build a Request
    
    var request = URLRequest(url: url!)
    request.httpMethod = "POST"
    request.setValue("text/plain", forHTTPHeaderField: "Content-Type")
    request.httpBody = "{\"jsonrpc\":\"1.0\",\"id\":\"curltest\",\"method\":\"\(method)\",\"params\":[\(param)]}".data(using: .utf8)

// 3. Build a Session
    
    let session = URLSession(configuration: .default)
    let task = session.dataTask(with: request as URLRequest) { data, response, error in

        do {


            if error != nil {

                    //Handle the error
                    
            } else {
                    
                if let urlContent = data {
                        
                    do {
                            
                        let json = try JSONSerialization.jsonObject(with: urlContent, options: JSONSerialization.ReadingOptions.mutableLeaves) as! NSDictionary
                        if let errorCheck = json["error"] as? NSDictionary {
                                                                
                            if let errorMessage = errorCheck["message"] as? String {

                                print("FAILED")
                                print(errorMessage)

                            }
                                
                        } else {
                                
                            let result = json["result"]
                            completionHandler(result)
                            
                        }
                            
                    } catch {
                            
                            //Handle error here
                            
                    }
                        
                }
                    
            }
                
        }
            
    }

//    return response
    task.resume()
    
}

// 0. Generate a Receiving Address

var method = "getnewaddress"
var param = "\"learning-bitcoin\", \"legacy\""

makeCommand(method: method,param: param) { result in

    let address = result as! NSString

// 1. Find an Unspent UTXO

    method = "listunspent"
    param = ""
    
    makeCommand(method: method,param: param) { result in

        let unspent = result! as! NSArray
        let utxo = unspent[0] as! NSDictionary
        
        let txid = utxo["txid"] as! NSString
        let vout = utxo["vout"] as! NSInteger
        let amount = utxo["amount"] as! NSNumber
        let new_amount = amount.floatValue - 0.0001

// 2. Create a Raw Transaction

        method = "createrawtransaction"
        param="[ { \"txid\": \"\(txid)\", \"vout\": \(vout) } ], { \"\(address)\": \(new_amount)}"
        makeCommand(method: method,param: param) { result in

            let hex = result as! NSString

// 3. Sign the Raw Transaction

            method = "signrawtransactionwithwallet"
            param = "\"\(hex)\""
            
            makeCommand(method: method,param: param) { result in

                let signedhexinfo = result as! NSDictionary
                let signedhex = signedhexinfo["hex"] as! NSString
                
// 4. Send the Raw Transaction

                method = "sendrawtransaction"
                param = "\"\(signedhex)\""

                makeCommand(method: method,param: param) { result in

                    let new_txid = result as! NSString
                    print("TXID: \(new_txid)")
                    
                }
            }
        }
    }
}