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Minting BTCx
BTCx can only be minted in exchange for RBTC.
In this tutorial the method (or function) that is of interest to us is function mintBProxVendors(bytes32 bucket, uint256 btcToMint, address vendorAccount) public payable. As you can see this function is payable, this means that it is prepared to receive RBTCs.
NOTE: there is a retrocompatibility function called function mintBProx(bytes32 bucket, uint256 btcToMint) which is suitable for those who are already integrated to MoC platform and are not ready to use vendor functionality. In the future we are planning to deprecate this method.

Parameters of the operation

The bucket parameter

A bucket is a bag that stores the balances of the leveraged token holders. Currently, only the BTCx bucket called X2 exists. The X2 must be passed as a hex value.
There is also a bucket named C0 but it should not be used to mint and redeem BTCx.
In the following example you can see how to do it with javascript and the web3 library. For more detailed information about web3 you can read the From outside the blockchain section.
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const BUCKET_X2 = web3.utils.asciiToHex('X2', 32);
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The btcToMint parameter

It is the amount the contract will use to actually mint BTCx, i.e. it will not be used to pay commission, all of this funds will be transformed purely on BTCx. This parameter uses a precision of the type reservePrecision that contains 18 decimal places is defined in MoCLibConnection contract.

The vendorAccount parameter

It is the address of the vendor who will receive a markup from the current transaction.

The value sent

The amount sent in RBTCs to the contract can be considered as a parameter of the transaction, which is why it will be explained in this section. You have to take into consideration that it will be split in five.
  • The first part will be used to mint some BTCx, the size of this part depends directly on the btcToMint, and it may be smaller than btcToMint.
  • The second part will be used to compute and pay interests that can be queried with the calcMintInterestValues(bucket, finalBtcToMint) of the MocInrate contract.
  • The third part will be used to pay the commission, this part is a percentage of the previous part. The commission fees are explained in this section.
  • The fourth part corresponds to the vendor markup, which refers to the fee a vendor will receive from this transaction and is a percentage of the first part. The vendor markup is explained in this section.
  • The fifth part is always returned, so if you have doubts of how much you should send, keep in mind that if you send too much RBTCs we will return everything that it is not used for commissions or minting.
All the needed calculations for the third and fourth parts are explained in more detail here.

Gas limit and gas price

This two values are a parameter of the transaction, this is not used in the contract and it is usually managed by your wallet (you should read about them if you are developing and you don't know exactly what are they) but you should take them into account when trying to send all of your funds to mint some BTCx.

Possible failures

This operation may fail if one of the following scenarios occurs:

The MoC contract is liquidated:

In the extraneous case where a coverage that barely covers the stable tokens funds is reached, the contract will liquidate all of its assets. If this state occurs, no more BTCx will be available for minting. To know if the contract is liquidated you can ask the MocState for the state, this will return a 0 if liquidated (it is actually an enum).

The MoC contract is paused:

If the system suffers some type of attack, the contract can be paused so that operations cannot be done and the risk of the users losing their funds with the operation can be minimized. You can get more information about stoppable contracts here. In that state, the contract doesn't allow minting any type of token.
To know if this is the case you can ask to MoC if it's paused().

Settlement is not ready:

The function can only be invoked when the Settlement is finished executing. If called during execution, the transaction reverts with the error message: Function can only be called when settlement is ready.

Bucket is not available:

Currently, only the BTCx bucket called 'X2' exists. If it is called with another bucket, the transaction reverts with the error message: Bucket is not available.

Bucket is not a base bucket:

Currently, only the BTCx bucket called 'X2' exists. If you call the function with C0 bucket, the transaction reverts with the error message: Bucket should not be a base type bucket.

You sent too few funds:

If the funds you sent doesn't cover the amount you specified on btcToMint.
If this is the case the transaction will revert, all your funds will be returned (except the fee paid to the network). The error message will be "amount is not enough".

Not enough gas:

If the gas limit sent is not enough to run all the code needed to execute the transaction, the transaction will revert (again, returning all your funds except the fee paid to the network). This may return an "out of gas" error or simply a "revert" error because of the usage of the proxy pattern.

How-to

In the following sections we will give some code on how this can be done through a Smart Contract or directly, with a console or with an app. ​

Smart Contract​

To create a new Smart Contract that uses the Money On Chain platform, you can use any language and IDE you want. In this tutorial, we will show you how to do it using Solidity language, Truffle Framework and NPM. Truffle framework offers some template projects that you can use to develop applications that use smart contracts. You can get more information here. Assuming you already have your project up and running (if you don't, please follow this link) the only extra thing you need to do is to install our repo as a dependency in your NPM project. In order you need to do this you just need to run the following command. ​
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npm install --save -E git+https://[email protected]/money-on-chain/main-RBTC-contract.git
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Having done that lets you use our contract as a dependency to your contract. For this let's suppose you are doing some kind of contract that when executing a certain task charges a fixed commission. Now let's suppose that the commission is sent in RBTCs because it is easier for the user but actually you want some BTCx. The good news is that you can do this instantly just by minting them. The code necessary to do this is actually pretty simple. ​ You just have to import the contracts ​
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import 'money-on-chain/contracts/MoC.sol';
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import 'money-on-chain/contracts/MoCInrate.sol';
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import 'money-on-chain/contracts/MoCExchange.sol';
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Receive the addresses in the constructor in order to be able to interact with it later, and the vendorAccount address needed to do the operation
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constructor (MoC _mocContract, MoCInrate _mocInrateContract, MoCExchange _mocExchangeContract, address vendorAccount, rest of your params...) {
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//....rest of your constructor....
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}
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​and, finally, when you receive a commission, exchange it for some BTCX2 ​
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// Calculate operation fees
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CommissionParamsStruct memory params;
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params.account = address(this); // address of minter
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params.amount = btcAmount; // BTC amount you want to mint
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params.txTypeFeesMOC = mocInrate.MINT_BTCX_FEES_MOC();
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params.txTypeFeesRBTC = mocInrate.MINT_BTCX_FEES_RBTC();
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params.vendorAccount = vendorAccount;
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CommissionReturnStruct memory commission = mocExchange.calculateCommissionsWithPrices(params);
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// If commission is paid in RBTC, subtract it from value
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uint256 fees = commission.btcCommission - commission.btcMarkup;
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// Mint some new BTCX
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moc.mintBProxVendors.value(msg.value)(bucket, msg.value - fees, vendorAccount);
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You can send it immediately to you so you can start using it right away. In order to do this you should add a few more lines similar to the ones before, only that you will have to use the BUCKET_X2 bucket. ​ This will leave you with a contract similar to the following ​ ​
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pragma solidity ^0.5.8;
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import "money-on-chain/contracts/MoC.sol";
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import 'money-on-chain/contracts/MoCInrate.sol';
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import 'money-on-chain/contracts/MoCExchange.sol';
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// Here you will import your own dependencies
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contract YourMintingBtc2xContract {
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// Address of the MoC contract
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MoC public moc;
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// Address of the MoCInrate contract
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MoCInrate public mocInrate;
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// Address of the MoCExchange contract
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MoCExchange public moCExchange;
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// Define a constant to call bucket X2
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​ bytes32 constant public BUCKET_X2 = "X2";
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// Address that will receive the markup
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address public vendorAccount;
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// rest of your variables
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constructor (MoC _mocContract, MoCInrate _mocInrateContract, MoCExchange _mocExchangeContract, address _vendorAccount) public {
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moc = _mocContract;
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mocInrate = _mocInrateContract;
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moCExchange = _mocExchangeContract;
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vendorAccount = _vendorAccount;
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// You could have more variables to initialize here
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}
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function doTask(uint256 btcAmount) public payable {
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// Calculate operation fees
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CommissionParamsStruct memory params;
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params.account = address(this); // address of minter
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params.amount = btcAmount; // BTC amount you want to mint
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params.txTypeFeesMOC = mocInrate.MINT_BTCX_FEES_MOC();
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params.txTypeFeesRBTC = mocInrate.MINT_BTCX_FEES_RBTC();
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params.vendorAccount = vendorAccount;
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CommissionReturnStruct memory commission = mocExchange.calculateCommissionsWithPrices(params);
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// If commission is paid in RBTC, subtract it from value
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uint256 fees = commission.btcCommission - commission.btcMarkup;
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// Mint some new BTCX
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moc.mintBProxVendors.value(msg.value)(bucket, msg.value - fees, vendorAccount);
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// Rest of the function to actually perform the task
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}
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// rest of your contract
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}
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