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Extension contract

Extension Interface​

The following functions need to be implemented for a valid extension contract.

You can also check the interface here on Github.

singleton​

Returns the address of the singleton contract

Returns​
  • singleton - address of the singleton contract
fn singleton(
        self: @TContractState
    ) -> ContractAddress;

price​

Returns the price for a given asset in a given pool.

This hook can be used to fetch the current price of either a supply or debt asset. The implementation of this hook is vital to the operation of the market as failure to appropriately implement fail-safes can lead to dangerous outcomes for the users' funds.

Arguments​
  • pool_id - id of the pool
  • asset - address of the asset
Returns​
  • AssetPrice - latest price of the asset and its validity
fn price(
        self: @TContractState,
        pool_id: felt252,
        asset: ContractAddress
    ) -> AssetPrice;

interest_rate​

This hook can be used to calculate the accrued interest on a position. Vesu remains agnostic towards these, giving developers the freedom to innovate.

Arguments​
  • pool_id - id of the pool
  • asset - address of the asset
  • utilization - utilization of the asset
  • last_updated - last time the interest rate was updated
  • last_full_utilization_rate - The interest value when utilization is 100% [SCALE]
Returns​
  • interest_rate - current interest rate
fn interest_rate(
        self: @TContractState,
        pool_id: felt252,
        asset: ContractAddress,
        utilization: u256,
        last_updated: u64,
        last_full_utilization_rate: u256,
    ) -> u256;

rate_accumulator​

Called prior to every position change and effectively asks the extension to compute and collect interest on all positions.

Arguments​
  • pool_id - id of the pool
  • asset - address of the asset
  • utilization - utilization of the asset
  • last_updated - last time the interest rate was updated
  • last_rate_accumulator - last rate accumulator
  • last_full_utilization_rate - the interest value when utilization is 100% [SCALE]
Returns​
  • rate_accumulator - current rate accumulator
  • last_full_utilization_rate - the interest value when utilization is 100% [SCALE]
fn rate_accumulator(
        self: @TContractState,
        pool_id: felt252,
        asset: ContractAddress,
        utilization: u256,
        last_updated: u64,
        last_rate_accumulator: u256,
        last_full_utilization_rate: u256,
    ) -> (u256, u256);

Hooks​

before_modify_position​

Modify position callback. Called by the Singleton contract before updating the position.

See before_modify_position in position_hooks.cairo.

Arguments​
  • context - contextual state of the user (position owner)
  • collateral - amount of collateral to be set/added/removed
  • debt - amount of debt to be set/added/removed
  • data - modify position data
  • caller - address of the caller
Returns​
  • collateral - amount of collateral to be set/added/removed
  • debt - amount of debt to be set/added/removed
fn before_modify_position(
        ref self: TContractState,
        context: Context,
        collateral: Amount,
        debt: Amount,
        data: Span<felt252>,
        caller: ContractAddress
    ) -> (Amount, Amount);

after_modify_position​

Modify position callback. Called by the Singleton contract after updating the position. See after_modify_position in position_hooks.cairo.

Arguments​
  • context - contextual state of the user (position owner)
  • collateral_delta - collateral balance delta of the position
  • collateral_shares_delta - collateral shares balance delta of the position
  • debt_delta - debt balance delta of the position
  • nominal_debt_delta - nominal debt balance delta of the position
  • data - modify position data
  • caller - address of the caller
Returns​
  • bool - true if the callback was successful
fn after_modify_position(
        ref self: TContractState,
        context: Context,
        collateral_delta: i257,
        collateral_shares_delta: i257,
        debt_delta: i257,
        nominal_debt_delta: i257,
        data: Span<felt252>,
        caller: ContractAddress
    ) -> bool;

before_transfer_position​

Transfer position callback. Called by the Singleton contract before transferring collateral / debt between position. See before_transfer_position in position_hooks.cairo.

Arguments​

_ from_context - contextual state of the user (position owner) from which to transfer collateral / debt _ to_context - contextual state of the user (position owner) to which to transfer collateral / debt _ collateral - amount of collateral to be transferred _ debt - amount of debt to be transferred _ data - modify position data _ caller - address of the caller

Returns​

_ collateral - amount of collateral to be transferred _ debt - amount of debt to be transferred

fn before_transfer_position(
        ref self: TContractState,
        from_context: Context,
        to_context: Context,
        collateral: UnsignedAmount,
        debt: UnsignedAmount,
        data: Span<felt252>,
        caller: ContractAddress
    ) -> (UnsignedAmount, UnsignedAmount);

after_transfer_position​

Transfer position callback. Called by the Singleton contract after transferring collateral / debt See after_transfer_position in position_hooks.cairo.

Arguments​
  • from_context - contextual state of the user (position owner) from which to transfer collateral / debt
  • to_context - contextual state of the user (position owner) to which to transfer collateral / debt
  • collateral_delta - collateral balance delta that was transferred
  • collateral_shares_delta - collateral shares balance delta that was transferred
  • debt_delta - debt balance delta that was transferred
  • nominal_debt_delta - nominal debt balance delta that was transferred
  • data - modify position data
  • caller - address of the caller
Returns​
  • bool - true if the callback was successful
fn after_transfer_position(
        ref self: TContractState,
        from_context: Context,
        to_context: Context,
        collateral_delta: u256,
        collateral_shares_delta: u256,
        debt_delta: u256,
        nominal_debt_delta: u256,
        data: Span<felt252>,
        caller: ContractAddress
    ) -> bool;

before_liquidate_position​

Liquidate position callback. Called by the Singleton contract before liquidating the position. See before_liquidate_position in position_hooks.cairo.

Arguments​
  • context - contextual state of the user (position owner)
  • collateral - amount of collateral to be set/added/removed
  • debt - amount of debt to be set/added/removed
  • data - liquidation data
  • caller - address of the caller
Returns​
  • collateral - amount of collateral to be removed
  • debt - amount of debt to be removed
  • bad_debt - amount of bad debt accrued during the liquidation
fn before_liquidate_position(
        ref self: TContractState,
        context: Context,
        data: Span<felt252>,
        caller: ContractAddress
    ) -> (u256, u256, u256);

after_liquidate_position​

Liquidate position callback. Called by the Singleton contract after liquidating the position. See before_liquidate_position in position_hooks.cairo.

Arguments​
  • context - contextual state of the user (position owner)
  • collateral_delta - collateral balance delta of the position
  • collateral_shares_delta - collateral shares balance delta of the position
  • debt_delta - debt balance delta of the position
  • nominal_debt_delta - nominal debt balance delta of the position
  • bad_debt - accrued bad debt from the liquidation
  • data - liquidation data
  • caller - address of the caller
Returns​
  • bool - true if the callback was successful
fn after_liquidate_position(
        ref self: TContractState,
        context: Context,
        collateral_delta: i257,
        collateral_shares_delta: i257,
        debt_delta: i257,
        nominal_debt_delta: i257,
        bad_debt: u256,
        data: Span<felt252>,
        caller: ContractAddress
    ) -> bool;

Example Extension​

If you're interested to see the full implementation check here on Github.