Crate pallet_xyk

XYK pallet

Provides functions for token operations, swapping tokens, creating token pools, minting and burning liquidity and supporting public functions

Token operation functions:

• create_pool
• mint_liquidity
• burn_liquidity
• sell_asset
• buy_asset
• compound_rewards
• provide_liquidity_with_conversion

Supporting public functions:

• calculate_sell_price
• calculate_buy_price
• calculate_sell_price_id
• calculate_buy_price_id
• get_liquidity_token
• get_burn_amount
• account_id
• settle_treasury_buy_and_burn
• calculate_balanced_sell_amount
• get_liq_tokens_for_trading

fn create_pool

-Sets the initial ratio/price of both assets to each other depending on amounts of each assets when creating pool.

-Transfers assets from user to vault and makes appropriate entry to pools map, where are assets amounts kept.

-Issues new liquidity asset in amount corresponding to amounts creating the pool, marks them as liquidity assets corresponding to this pool and transfers them to user. first_token_amount

arguments

origin - sender of a fn, user creating the pool

first_token_id - id of first token which will be directly inter-tradeable in a pair of first_token_id-second_token_id

first_token_amount - amount of first token in which the pool will be initiated, which will set their initial ratio/price

second_token_id - id of second token which will be directly inter-tradeable in a pair of first_token_id-second_token_id

second_token_amount - amount of second token in which the pool will be initiated, which will set their initial ratio/price

Example

create_pool(
   Origin::signed(1),
   0,
   1000,
   1,
   2000,
)

Account_id 1 created pool with tokens 0 and 1, with amounts 1000, 2000. Initial ratio is 1:2. Liquidity token with new id created in an amount of 1500 and transfered to user 1.

Errors

ZeroAmount - creating pool with 0 amount of first or second token

PoolAlreadyExists - creating pool which already exists

NotEnoughTokens - creating pool with amounts higher then user owns

SameToken - creating pool with same token

fn sell_token

-Sells/exchanges set amount of sold token for corresponding amount by xyk formula of bought token

arguments

origin - sender of a fn, user creating the pool

sold_token_id - token which will be sold

bought_token_id - token which will be bought

sold_token_amount - amount of token to be sold

min_amount_out - minimal acceptable amount of bought token received after swap

Example

sell_token (
   Origin::signed(1),
   0,
   1,
   1000,
   800,
)

Account_id 1 sells/exchanges 1000 token 0 for corresponding amount of token 1, while requiring at least 800 token 1

Errors

ZeroAmount - buying 0 tokens

NoSuchPool - pool sold_token_id - bought_token_id does not exist

NotEnoughTokens - selling more tokens then user owns

InsufficientOutputAmount - bought tokens to receive amount is lower then required min_amount_out

fn buy_token

-Buys/exchanges set amount of bought token for corresponding amount by xyk formula of sold token

arguments

origin - sender of a fn, user creating the pool

sold_token_id - token which will be sold

bought_token_id - token which will be bought

bought_token_amount - amount of token to be bought

max_amount_in - maximal acceptable amount of sold token to pay for requested bought amount

Example

buy_token (
   Origin::signed(1),
   0,
   1,
   1000,
   800,
)

Account_id 1 buys/exchanges 1000 tokens 1 by paying corresponding amount by xyk formula of tokens 0

Errors

ZeroAmount - selling 0 tokens

NoSuchPool - pool sold_token_id - bought_token_id does not exist

NotEnoughTokens - selling more tokens then user owns

InsufficientInputAmount - sold tokens to pay is higher then maximum acceptable value of max_amount_in

fn mint_liquidity

-Adds liquidity to pool, providing both tokens in actual ratio -First token amount is provided by user, second token amount is calculated by function, depending on actual ratio -Mints and transfers corresponding amount of liquidity token to mintin user

arguments

origin - sender of a fn, user creating the pool

first_token_id - first token in pair

second_token_id - second token in pair

first_token_amount - amount of first_token_id, second token amount will be calculated

Example

mint_liquidity (
   Origin::signed(1),
   0,
   1,
   1000,
)

If pool token 0 - token 1 has tokens in amounts 9000:18000 (total liquidity tokens 27000)

Account_id 1 added liquidity to pool token 0 - token 1, by providing 1000 token 0 and corresponding amount of token 1. In this case 2000, as the ratio in pool is 1:2. Account_id 1 also receives corresponding liquidity tokens in corresponding amount. In this case he gets 10% of all corresponding liquidity tokens, as he is providing 10% of all provided liquidity in pool. 3000 out of total 30000 liquidity tokens is now owned by Account_id 1

Errors

ZeroAmount - minting with 0 tokens

NoSuchPool - pool first_token_id - second_token_id does not exist

NotEnoughTokens - minting with more tokens then user owns, either first_token_id or second_token_id

fn burn_liquidity

-Removes tokens from liquidity pool and transfers them to user, by burning user owned liquidity tokens -Amount of tokens is determined by their ratio in pool and amount of liq tokens burned

arguments

origin - sender of a fn, user creating the pool

first_token_id - first token in pair

second_token_id - second token in pair

liquidity_token_amount - amount of liquidity token amount to burn

Example

burn_liquidity (
   Origin::signed(1),
   0,
   1,
   3000,
)

If pool token 0 - token 1 has tokens in amounts 10000:20000 (total liquidity tokens 30000)

Account_id 1 is burning 3000 liquidity tokens of pool token 0 - token 1 As Account_id 1 is burning 10% of total liquidity tokens for this pool, user receives in this case 1000 token 0 and 2000 token 1

Errors

ZeroAmount - burning 0 liquidity tokens

NoSuchPool - pool first_token_id - second_token_id does not exist

NotEnoughTokens - burning more liquidity tokens than user owns

fn compound_rewards

• Claims a specified portion of rewards, and provides them back into the selected pool.
• Wraps claim_rewards, sell_asset and mint_liquidity, so that there is minimal surplus of reward asset left after operation.
• Current impl assumes a MGX-ASSET pool & rewards in MGX asset

arguments

origin - sender of a fn, user claiming rewards and providing liquidity to the pool

liquidity_asset_id - the pool where we provide the liquidity

amount_permille - portion of rewards to claim

Example

compound_rewards (
   Origin::signed(1),
   2,
   1_000,
)

Claim all of the rewards, currently in MGX, and use them to provide liquidity for the pool with asset id 2

Errors

• inherits all of the errors from claim_rewards, sell_asset and mint_liquidity

NoSuchLiquidityAsset - pool with given asset id does not exist

FunctionNotAvailableForThisToken - not available for this asset id

NotEnoughRewardsEarned - not enough rewards available

fn provide_liquidity_with_conversion

• Given one of the liquidity pool asset, computes balanced sell amount and provides liquidity into the pool
• Wraps sell_asset and mint_liquidity

arguments

origin - sender of a fn, user claiming rewards and providing liquidity to the pool

liquidity_asset_id - the pool where we provide the liquidity

provided_asset_id - which asset of the pool

provided_asset_amount - amount of the provided asset to use

Example

provide_liquidity_with_conversion (
   Origin::signed(1),
   2,
   1,
   1_000_000,
)

Given the liquidity pool with asset id 2, we assume that asset id 1 is one of the pool’s pair, compute balanced swap and provide liquidity into the pool

Errors

• inherits all of the errors from sell_asset and mint_liquidity

NoSuchLiquidityAsset - pool wiht given asset id does not exist

FunctionNotAvailableForThisToken - not available for this asset id

calculate_sell_price

• Supporting public function accessible through rpc call which calculates and returns bought_token_amount while providing sold_token_amount and respective reserves

calculate_buy_price

• Supporting public function accessible through rpc call which calculates and returns sold_token_amount while providing bought_token_amount and respective reserves

calculate_sell_price_id

• Same as calculate_sell_price, but providing token_id instead of reserves. Reserves are fetched by function.

calculate_buy_price_id

• Same as calculate_buy_price, but providing token_id instead of reserves. Reserves are fetched by function.

get_liquidity_token

• Supporting public function accessible through rpc call which returns liquidity_token_id while providing pair token ids

get_burn_amount

• Supporting public function accessible through rpc call which returns amounts of tokens received by burning provided liquidity_token_amount in pool of provided token ids

account_id

• Returns palled account_id

settle_treasury_buy_and_burn

• Supporting function which takes tokens to alocate to treasury and tokens to be used to burn mangata
• First step is deciding whether we are using sold or bought token id, depending which is closer to mangata token
• In second step, if tokens are mangata, they are placed to treasury and removed from corresponding pool. If tokens are not mangata, but are available in mangata pool, they are swapped to mangata and placed to treasury and removed from corresponding pool. If token is not connected to mangata, token is temporarily placed to treasury and burn treasury.

calculate_balanced_sell_amount

• Supporting public function accessible through rpc call which calculates how much amount x we need to swap from total_amount, so that after y = swap(x), the resulting balance equals (total_amount - x) / y = pool_x / pool_y
• the resulting amounts can then be used to mint_liquidity with minimal leftover after operation

get_liq_tokens_for_trading

• Supporting public function accessible through rpc call which lists all of the liquidity pool token ids that are available for trading

Re-exports

• pub use weights::WeightInfo;
• pub use pallet::*;

Modules

• pallet
  The pallet module in each FRAME pallet hosts the most important items needed to construct this pallet.
• weights
  Autogenerated weights for pallet_xyk

Macros

• log

Enums

• SwapKind

Traits

• AssetMetadataMutationTrait

Type Definitions

• BalanceOf
• CurrencyIdOf