Acala Stablecoin

To interact with Acala or Karura from Javascript you can use @polkadot/api along with @acala-network/api. You can learn more about @polkadot/api [here]. (https://polkadot.js.org/docs/api).

We do also provide a Stablecoin SDK which provides more some automation around stablecoins.

Source Code of Karura Stablecoin

https://github.com/AcalaNetwork/Acala/tree/master/modules/honzon

Read-Only Functions (State queries)

These functions only read information from the chain, and thus don't require signing transactions with a private key. Read more about state queries here: State queries docs

Get Vault for specific Account for given Collateral Type

Returns amount of collateral and amount of minted stablecoin as debit for specific collateral type and account.

Note ⚠️ debit reflects the only amount of minted kUSD. The amount of debt is higher as it includes accumulated interest. To calculate the total amount to payback you need to use debitExchangeRate parameter (the example for fetching debitExchangeRate is shown below).

positions(currencyId: CurrencyId, accountId: AccountId):
    Promise<{collateral: number, debit: number}>

Arguments

Name	Type
currencyId	CurrencyId	collateral currency Id
accountId	AccountId	account to fetch vaults for, can be passed as string

Example:

    const result = await api.query.loans.positions(
        { TOKEN: "KSM" },
        "<ACCOUNT>"
    );
  console.log(result.toHuman());

Full code snippet:

loan-examples/get-positions.js

Get total amount of collateral and borrowed kUSD for Collateral Type

Returns total amount of collateral and amount of borrowed stablecoin as debit for specific collateral type.

totalPositions(currencyId: CurrencyId):
    Promise<{collateral: number, debit: number}>

Arguments

Name	Type
currencyId	CurrencyId	identificator for currency used as collateral

Example:

    const result = await api.query.loans.totalPositions(
        { TOKEN: "KSM" }
    );
  console.log(result.toHuman());

Full code snippet:

loan-examples/total-positions.ts

Get Risk Parameters for given Collateral type.

Each accepted by Karura Collateral Type can have different risk parameters. These values are controlled by Karura Governance.

collateralParams(currencyId: CurrencyId):
    Promise<{
    maximumTotalDebitValue: number,
    interestRatePerSec: number, 
    liquidationRatio: number,
    liquidationPenalty: number,
    requiredCollateralRatio: number,

    }>

Arguments

Name	Type
currencyId	CurrencyId	identificator for currency used as collateral

Return values

Name	Type
maximumTotalDebitValue	Number	maximum amount of KUSD that can be borrowed for one vault
interestRatePerSec	Percent	the percentage of borrowed kUSD to be paid each next block. This amount should be added to globalInterestRatePerSec to calculate the debt
liquidationRatio	Percent	collateral ratio (collateral value / debt value) reaching which the vault gets liquidated
liquidationPenalty	Percent	penalty that is charged from the vault if the vault gets liquidated
requiredCollateralRatio	Percent	Minimum collateral ratio till which user can borrow kUSD

Example:

    const result = await api.query.cdpEngine.collateralParams({ 
      TOKEN: "KSM" 
    });
    console.log(result.toHuman());

Full code snippet:

loan-examples/collateral-params.ts

Get Debt Exchange Rate for given collateral type

This parameter is used to calculate the debt. The amount of minted kUSD should be multiplied by this parameter. As the Interest rate is accumulated depends on block number, it makes sense to fetch this parameter for a certain block.

debitExchangeRate(currencyId: CurrencyId):
    Promise<number}>

Arguments

Name	Type
currencyId	CurrencyId	identificator for currency used as collateral

Example:

  const result = await api.query.cdpEngine.debitExchangeRate.at(
      '<BLOCK_HASH'
      { TOKEN: "KSM" }
  );
  console.log(result.toHuman());

Full code snippet:

loan-examples/debit-exchange-rate.ts

State-Changing Functions

These transactions write data on-chain and require a private key to sign the transaction. To perform run test code snippets ensure that you have SEED_PHRASE environment variable defined in your .env file.

Create and manage the Vault

All operations: creating a vault, adding/removing collateral, borrowing, paying back kUSD can be done using a single method: honzon.adjustLoan

adjustLoan(currency_id: CurrencyId, collateral_adjustment: Number, debit_adjustment: Number): Extrinsic

Arguments

Name	Type
currencyId	CurrencyId	collateral CurrencyId
collateral_adjustment	Signed Amount	positive means to deposit collateral currency into Vault, negative means withdraw collateral currency from the Vault
debit_adjustment	Signed Amount	positive means to mint some amount of stablecoin to the caller; negative means that caller will pay back stablecoin to the Vault

Example

  const currencyId = { TOKEN: "KSM" };
  const collateralAdjustment = <DESIRED_ADJUSTMENT>;
  const debitAdjustment = <DESIRED_ADJUSTMENT>;

  const extrinsic = api.tx.honzon.adjustLoan(
    currencyId,
    collateralAdjustment,
    debitAdjustment
  );
  const hash = await extrinsic.signAndSend(signer);
  console.log('hash', hash.toHuman());

Note ⚠️ the supply amount should be denormalised with KAR decimals for this example

Full code snippet:

loan-examples/adjustLoan.ts

Grants permission for transferring loan

Sets permission to transfer caller's loan to another Account (to).

authorize(curencyId: CurrencyId, to: AccountId): Extrinsic

Returns Extrinsic type that should be signed with a private key.

Arguments

Name	Type
currencyId	CurrencyId	collateral CurrencyId
to	AccountId	sets permission to transfer loan for this accountId

Example:

  const accountId = "<ACCOUNT_ID>";
  const extrinsic = api.tx.honzon.authorize(
    { TOKEN: "KSM" }, 
    accountId
  );
  const hash = await extrinsic.signAndSend(signer);
  console.log("hash", hash.toHuman());

Full code snippet:

loan-examples/authorize.ts

Removes permission for transferring loan

Removes permission to transfer caller's loan to another Account (to). This method can be used to decline previously given permission.

unauthorize(curencyId: CurrencyId, to: AccountId): Extrinsic

Returns Extrinsic type that should be signed with a private key.

Arguments

Name	Type
currencyId	CurrencyId	collateral CurrencyId
to	AccountId	removes permission to transfer loan for this accountId

Example:

  const accountId = "<ACCOUNT_ID>";
  const extrinsic = api.tx.honzon.unauthorize(
    { TOKEN: "KSM" }, 
    accountId
  );
  const hash = await extrinsic.signAndSend(signer);
  console.log("hash", hash.toHuman());

Removes permissions for ALL accounts to transfer the vault

Removes permission to transfer caller's vault to ALL accounts for all Collateral types. This method can be used to decline previously given permission.

unauthorizeAll(): Extrinsic

Returns Extrinsic type that should be signed with a private key.

Example:

  const extrinsic = api.tx.honzon.unauthorizeAll();
  const hash = await extrinsic.signAndSend(signer);
  console.log("hash", hash.toHuman());

Transfering Vault to another account

Transfers Vault to the caller's account if it has permissions (if authorize was called previously by from account).

transferLoanFrom(currency_id, from): Extrinsic

Returns Extrinsic type that should be signed with a private key.

Arguments

Name	Type
currencyId	CurrencyId	collateral CurrencyId
from	AccountId	transfers collateral from this account to the caller

Example:

    const fromAccountId = "<ACCOUNT_ID>";
    const extrinsic = api.tx.honzon.transferLoanFrom(
      { TOKEN: "KSM" },
      fromAccountId
    );
    const hash = await extrinsic.signAndSend(signer);
    console.log("hash", hash.toHuman());

Closing caller's Vault by swapping collateral in DeX

This action can be done with adjustLoan, but there is a shortcut created for this purpose which is applied only to safe vaults (where the collateral ratio is above liquidation level) and where the debt amount is positive.

This method closes the caller's Vault by selling a sufficient amount of collateral on Karura Dex.

closeLoanHasDebitByDex(
    currency_id: CurrencyId, 
    max_collateral_amount: number, 
    maybe_path?: CurrencyId[]
): Extrinsic

Returns Extrinsic type that should be signed with a private key.

Arguments

Name	Type
currencyId	CurrencyId	collateral CurrencyId
max_collateral_amount	number	the maximum collateral that's allowed to be swapped in DeX to pay back the Vault
maybe_path	CurrencyId[]	swap path that can be used for swapping collateral for kUSD in DeX

Example:

    const extrinsic = api.tx.honzon.closeLoanHasDebitByDex(
      { TOKEN: "KSM" },
      // large number, allows swapping almost any amount
      1 * 10 ** 30,
      [{ TOKEN: "KSM" }, { TOKEN: "KUSD" }]
    );
    const hash = await extrinsic.signAndSend(signer);
    console.log("hash", hash.toHuman());

Full code snippet:

loan-examples/close-vault-with-dex.ts