# TwapRelayer Upgrades: Multihop Support (coming soon)

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Changes are not live yet, and no changes to TwapRelayer integration should be made until further notice.
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The upcoming `TwapRelayer` upgrade adds support for trades between `tokens`along whitelisted `paths` that involve one or more `pairs`. For example, `usdc-wbtc` is a new `path` that has been whitelisted in the system that allows trades between `usdc` and `wbtc` (bidirectionally) via the existing `weth-usdc` and `weth-wbtc` pairs. 

As a result of this upgrade, aggregators and solvers who have integrated the `TwapRelayer` using the following events or functions, please make the recommended changes below. No changes needed if the current integration does not directly use any of the following events or functions.

* `function isPairEnabled`
* `event TokenLimitMinSet`
* `event TokenLimitMaxMultiplierSet`
* `function tokenLimitMin`
* `function tokenLimitMaxMultiplier`
* `function getTokenLimitMin`
* `function getTokenLimitMaxMultiplier`

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Link to Smart Contracts upgrade PR: <https://github.com/IntegralHQ/Integral-SIZE-Smart-Contracts/pull/1>
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## How to Upgrade

Common functions have been automatically updated to take advantage of paths without the need for developers to make any changes:

* `sell`, `buy`, `quoteBuy`, `quoteSell`, `getPoolState` still take the parameters:`tokenIn` and `tokenOut` and now automatically route using `paths` under the hood when available.

If you rely on any of the events or functions below, please make the recommended changes. If your current integration does not directly use any of the following events or functions, you should not have to make any changes:

* Replace calls to `function isPairEnabled(bool pairAddress) returns (bool isEnabled)` with `function isPathEnabled(address tokenIn, address tokenOut) returns (bool isEnabled)`
* Replace event listeners `event TokenLimitMinSet(address token, uint256 limit)`and `event TokenLimitMaxMultiplierSet(address token, uint256 limit)`with `event TokenLimitsSet(address token, uint256 min, uint256 max)`
* Replace calls to `function tokenLimitMin(address token) returns (uint256)`,`function tokenLimitMaxMultiplier(address token) returns (uint256)`, `function getTokenLimitMin(address token) returns (uint256)`, and `function getTokenLimitMaxMultiplier(address token) returns (uint256)`with `function getTokenLimits(address token) returns (uint256 min, uint256 max)`
  * Note:
    * `tokenLimitMin` now applies to the input token amount
    * `tokenLimitMax` now applies to the input token amount
* We will provide an updated list of tradable `paths` based on the network
  * Existing `pairs` will still be tradable and unchanged
  * New `paths`, which involve trading across multiple `pairs` atomically will be added

## Summary

### Adds Multihop Support

The `TwapRelayer` update adds support for trades between `tokens`along whitelisted `paths` that involve one or more `pairs`. For example, `usdc-wbtc` is a new `path` that has been whitelisted in our system that allows trades between `usdc` and `wbtc` (bidirectionally) via the existing `weth-usdc` and `weth-wbtc` pairs.

* The original set of tradable tokens has been expanded by the addition of new `paths`; original `pairs` are still tradable.
  * `paths` are composed of one or more `pairs`
  * all original `pairs` are still tradable via a `path` that only contains one `pair`
* Functions for trading and quoting have not changed and are 100% backwards compatible.
* Common functions have been automatically updated to take advantage of paths without the need for developers to make any changes:
  * `sell`, `buy`, `quoteBuy`, `quoteSell`, `getPoolState` still take the parameters:`tokenIn` and `tokenOut` and now automatically route using `paths` under the hood when available.
* `isPairEnabled` is still available but is now deprecated in favor of `isPathEnabled`, which tells developers if any `path`or any `pair` is available while the former only tells users if a `pair` is enabled.

### Refactors Token Limits

In addition, `token limits` have been refactored to take on new meaning and use:

* `TokenLimitMin` remains but now only applies to the input token, instead of the output token.
* `TokenLimitMaxMultiplier` has been removed and replaced by `TokenLimitMax`, which checks the input token amount does not exceed a certain limit.

## Smart Contract Changes

### Removed from SCs or Deprecated

**Deprecated:**

* `mapping(address => bool) public override isPairEnabled;`

**Removed:**

* `event TokenLimitMinSet(address token, uint256 limit);`
* `event TokenLimitMaxMultiplierSet(address token, uint256 limit);`
* `function tokenLimitMin(address token) external pure returns (uint256);`
* `function tokenLimitMaxMultiplier(address token) external pure returns (uint256);`
* `function getTokenLimitMin(address token) external pure returns (uint256);`
* `function getTokenLimitMaxMultiplier(address token) external pure returns (uint256);`

**Moved:**

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These events have been refactored to the `RelayerMacros` library but will still be emitted from `TwapRelayer`, so no developer changes should need to be made
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* `event EthTransferGasCostSet(uint256 gasCost);`
* `event TwapIntervalSet(address pair, uint32 interval);`
* `event ToleranceSet(address pair, uint16 tolerance);`

### Added to SCs

* `event TokenLimitsSet(address token, uint256 min, uint256 max);`
* `function getTokenLimits(address token) external pure returns (uint256 min, uint256 max);`
* `function isPathEnabled(address tokenIn, address tokenOut) external view returns (bool);`