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Summary

We've met all the objectives set out in 300 lines of easy to read and understand Javascript and now have a form of primitive automation.

  • Use zilliqa-js to deploy a contract.
  • Use zilliqa-js to interact with and press the button.
  • Use zilliqa-js to get the mutable state of our contract.
  • Use zilliqa-js to listen for events in our contract.
const { BN, Long, bytes, units } = require('@zilliqa-js/util');const { Zilliqa } = require('@zilliqa-js/zilliqa');const { StatusType, MessageType } = require('@zilliqa-js/subscriptions');const { fromBech32Address, toBech32Address, getAddressFromPrivateKey} = require('@zilliqa-js/crypto');
// these values can change depending on what network you are connecting onconst zilliqa = new Zilliqa('https://dev-api.zilliqa.com');// webhook to listen to events emited back to clientsconst websocket = "wss://dev-ws.zilliqa.com"const chainId = 333;const msgVersion = 1; const VERSION = bytes.pack(chainId, msgVersion);
// use a dotenv file for storing private keys, do not commit this directly to your repoconst privateKey ='';// mutable state field name to monitorconst state_field_to_monitor = "total_count_clicks"
zilliqa.wallet.addByPrivateKey(privateKey);const address_from_pk = getAddressFromPrivateKey(privateKey);
// Application Definition// DEPLOY a contract, // SEND a transaction// LISTEN to events emitted// MONITOR mutable state async function DeploySendListenMonitor(){    deployed_contract_base_16 = await DeployButtonContract();    bech_32_bystr = toBech32Address(deployed_contract_base_16);    console.log(`got ${bech_32_bystr} from ${deployed_contract_base_16}`)
    await Promise.all([        ListenForEvents(deployed_contract_base_16),        PressTheButton(bech_32_bystr)    ]);}
// Runs ApplicationDeploySendListenMonitor();
// Deploys a contract using a private key, returns the deployed_contract_base_16 of the contract deployedasync function DeployButtonContract() {    try {      // Get Balance      const balance = await zilliqa.blockchain.getBalance(address_from_pk);      // Get Minimum Gas Price from blockchain      const minGasPrice = await zilliqa.blockchain.getMinimumGasPrice();        // Account balance (See note 1)      console.log(`Your account balance is:`);      console.log(balance.result);      console.log(`Current Minimum Gas Price: ${minGasPrice.result}`);      const myGasPrice = units.toQa('2000', units.Units.Li); // Gas Price that will be used by all transactions      console.log(`My Gas Price ${myGasPrice.toString()}`);      const isGasSufficient = myGasPrice.gte(new BN(minGasPrice.result)); // Checks if your gas price is less than the minimum gas price      console.log(`Is the gas price sufficient? ${isGasSufficient}`);        // Deploy a contract      console.log(`Deploying a new contract....`);      const code = `scilla_version 0library MyFirstButton
let uint128_zero = Uint128 0let uint128_one  = Uint128 1let empty_bystr = 0x1111111111111111111111111111111111111111
(* Error exception *)type Error =| NotContractOwner| NotUniqueClicker
let make_error =fun (result : Error) =>    let result_code =     match result with    | NotContractOwner             => Int32 -1    | NotUniqueClicker             => Int32 -2    end    in    { _exception : "Error"; code : result_code }      (** Create a scilla contract which models a button that can be pressed by anyone. * If you are the recent button presser you may not press the button again.* When the button is pressed: Increment a counter and set the caller of the button press to be the most recent address.  * The owner of the button has the ability to reset the counter to zero *)contract MyFirstButton(contract_owner: ByStr20)
field current_clicker    : ByStr20 = empty_bystrfield total_count_clicks : Uint128 = uint128_zero
(* @Dev: Emit Errors *)procedure ThrowError(err : Error)e = make_error err;throw eend
(*@Dev : Throws an error if '_sender' is not 'contract_owner'*)procedure IsContractOwner()is_contract_owner = builtin eq contract_owner _sender;match is_contract_owner with| True =>     (* No Operation - Continue contract execution *)| False =>    err = NotContractOwner;    ThrowError errendend
(*  Dev: Increments 'current_clicker' by 'uint128_one'*)procedure IncrementCounter()previous_click_count <- total_count_clicks;new_click_count = builtin add previous_click_count uint128_one;total_count_clicks := new_click_count;
e = {_eventname : "IncrementCounterSuccess"; pcc:previous_click_count; ncc: new_click_count  };event eend 

(*  Dev: Throws an error if the current '_sender' is the previous 'current_clicker'*)procedure IsPreviousClicker(new_clicker: ByStr20)previous_clicker <- current_clicker;is_previous_clicker = builtin eq previous_clicker _sender;match is_previous_clicker with| True =>     err = NotUniqueClicker;    ThrowError err| False =>    (* No Operation - Continue contract execution *)endend
(*  Dev: Sets 'new_clicker' as 'current_clicker'*)procedure SetNewClicker(new_clicker: ByStr20)current_clicker := new_clicker;
e = {_eventname : "NewClickerState"; nc:new_clicker};event eend
(*  Dev: Resets 'current_clicker' to 'uint128_zero'*)procedure ContractOwnerResetButton()total_count_clicks  := uint128_zeroend
(*  Dev: Sets 'new_clicker' as current_clicker*)transition PressTheButton()IsPreviousClicker _sender;SetNewClicker _sender;IncrementCounter;
e = {_eventname : "PressTheButtonSuccess"; button_presser : _sender };event eend
(*  Dev: Sets 'new_clicker' as current_clicker*)transition OwnerResetButton()IsContractOwner;ContractOwnerResetButtonend`;        const init = [        // this parameter is mandatory for all init arrays        {          vname: '_scilla_version',          type: 'Uint32',          value: '0',        },        {          vname: 'contract_owner',          type: 'ByStr20',          value: `${address_from_pk}`,        },      ];        const contract = zilliqa.contracts.new(code, init);        // Deploy the contract.      // Also notice here we have a default function parameter named toDs as mentioned above.      // A contract can be deployed at either the shard or at the DS. Always set this value to false.      const [deployTx, deployedContract] = await contract.deployWithoutConfirm(        {          version: VERSION,          gasPrice: myGasPrice,          gasLimit: Long.fromNumber(10000),        },        false,      );        // process confirm      console.log(`The transaction id is:`, deployTx.id);      console.log(`Waiting transaction be confirmed`);      const confirmedTxn = await deployTx.confirm(deployTx.id);        console.log(`The transaction status is:`);      console.log(confirmedTxn.receipt);      if (confirmedTxn.receipt.success === true) {        console.log(`Contract address is: 0x${deployedContract.address}`);        return "0x" + deployedContract.address;      }    } catch (err) {      console.log(err);    }}
// Listen for events from a contract - errors aren't caughtasync function ListenForEvents(deployed_contract_base_16) {    const subscriber = zilliqa.subscriptionBuilder.buildEventLogSubscriptions(      websocket,      {        addresses: [            deployed_contract_base_16        ],      },    );
    console.log("Listener started");      subscriber.emitter.on(MessageType.EVENT_LOG, async (event) => {        console.log('get new event log: ', JSON.stringify(event)); // this will emit 2/3 times before event emitted
        const current_button_click_count = await zilliqa.blockchain.getSmartContractSubState(            deployed_contract_base_16,            state_field_to_monitor          );        console.log(current_button_click_count.result);        console.log("")    });      await subscriber.start();}
// Calls the previously deployed contract transitionasync function PressTheButton(bech_32_bystr) {  try {    const balance = await zilliqa.blockchain.getBalance(address_from_pk);    const minGasPrice = await zilliqa.blockchain.getMinimumGasPrice();    const myGasPrice = units.toQa('2000', units.Units.Li);     const isGasSufficient = myGasPrice.gte(new BN(minGasPrice.result));     const deployedContract = zilliqa.contracts.at(bech_32_bystr,);
    console.log(`Pressing the button...`);    const callTx = await deployedContract.callWithoutConfirm(        'PressTheButton', // transition name        [], // no vnames        {        version: VERSION,        amount: new BN(0),         gasPrice: myGasPrice,         gasLimit: Long.fromNumber(8000),         },        false,    );
    console.log(`Waiting transaction be confirmed`);    const confirmedTxn = await callTx.confirm(callTx.id);
    //console.log(`The transaction status is:`);    //console.log(confirmedTxn.receipt);    if (confirmedTxn.receipt.success === true)     {      console.log(`Button pressed by : ${address_from_pk}`);    }  }   catch (err)   {    console.log(err);  }}

Your account balance is:{ balance: '1990534999999850', nonce: 307 }Current Minimum Gas Price: 2000000000My Gas Price 2000000000Is the gas price sufficient? trueDeploying a new contract....The transaction id is: 1548964c7d852fdb5c2b606a62aba83a5e89ce3ec047c3eac8986b0943e10da7Waiting transaction be confirmedThe transaction status is:{ cumulative_gas: 401, epoch_num: '3726858', success: true }Contract address is: 0x60d5edfe4bcff11bde238c153853bcf358654b41got zil1vr27mljtelc3hh3r3s2ns5au7dvx2j6pa6p9k0 from 0x60d5edfe4bcff11bde238c153853bcf358654b41Listener startedPressing the button...Waiting transaction be confirmed
get new event log:  {"query":"EventLog"}{ total_count_clicks: '0' }
get new event log:  {"query":"EventLog","value":[{"address":"60d5edfe4bcff11bde238c153853bcf358654b41","event_logs":[{"_eventname":"PressTheButtonSuccess","params":[{"type":"ByStr20","value":"0x428a2aa43456fe7fd2de66e48c1fbf372ec10eae","vname":"button_presser"}]},{"_eventname":"IncrementCounterSuccess","params":[{"type":"Uint128","value":"0","vname":"pcc"},{"type":"Uint128","value":"1","vname":"ncc"}]},{"_eventname":"NewClickerState","params":[{"type":"ByStr20","value":"0x428a2aa43456fe7fd2de66e48c1fbf372ec10eae","vname":"nc"}]}]}]}{ total_count_clicks: '1' }
Button pressed by : 0x428A2aA43456FE7fd2De66E48C1fBf372eC10eAEget new event log:  {"query":"EventLog"}{ total_count_clicks: '1' }