# Simulation
To enable simulations for a newly added protocol, it must first be integrated into the Tycho monorepo. Please submit a pull request to the [repository](https://github.com/propeller-heads/tycho-indexer) targeting `crates/tycho-simulation`.
## Native Integration
In order to add a new native protocol, you will need to complete the following high-level steps:
1. Create a protocol state struct that contains the state of the protocol, and implements the `ProtocolSim` trait (see [here](https://github.com/propeller-heads/tycho-indexer/blob/main/crates/tycho-simulation/src/protocol/state.rs)).
2. Create a tycho decoder for the protocol state: i.e. implement `TryFromWithBlock` for `ComponentWithState` to your new protocol state.
Each native protocol should have its own module under `crates/tycho-simulation/src/evm/protocol`.
## VM Integration
To create a VM integration, provide a manifest file and an implementation of the corresponding adapter interface. The [Tycho monorepo](https://github.com/propeller-heads/tycho-indexer) contains the tools to integrate DEXs and other onchain liquidity protocols into Tycho.
### Example Implementations
The following exchanges are integrated with the VM approach:
* Balancer V2 (see code [here](https://github.com/propeller-heads/tycho-indexer/blob/main/protocols/adapter-integration/evm/src/balancer-v2/BalancerV2SwapAdapter.sol))
### Install prerequisites
1. Install [Foundry](https://book.getfoundry.sh/getting-started/installation#using-foundryup), start by downloading and installing the Foundry installer:
```bash
curl -L https://foundry.paradigm.xyz | bash
```
then start a new terminal session and run
```bash
foundryup
```
2. Clone the Tycho monorepo:
```bash
git clone https://github.com/propeller-heads/tycho-indexer
```
3. Install dependencies:
```bash
cd ./tycho-indexer/protocols/adapter-integration/evm/
forge install
```
### Understanding the ISwapAdapter
Read the documentation of the [Ethereum Solidity](https://docs.propellerheads.xyz/tycho/for-dexs/protocol-integration/simulation/ethereum-solidity) interface. It describes the functions that need to be implemented and the manifest file.
Additionally, read through the docstring of the [ISwapAdapter.sol](https://github.com/propeller-heads/tycho-indexer/blob/main/protocols/adapter-integration/evm/interfaces/ISwapAdapter.sol) interface and the [ISwapAdapterTypes.sol](https://github.com/propeller-heads/tycho-indexer/blob/main/protocols/adapter-integration/evm/interfaces/ISwapAdapterTypes.sol) interface, which defines the data types and errors the adapter interface uses. You can also generate the documentation locally and look at the generated documentation in the `./docs` folder:
```bash
cd ./evm/
forge doc
```
### Implementing the ISwapAdapter interface
Your integration should be in a separate directory in the `protocols/adapter-integration/evm/src` folder. Start by copying the template directory:
```bash
cp ./protocols/adapter-integration/evm/src/template ./protocols/adapter-integration/evm/src/
```
Implement the `ISwapAdapter` interface in the `./protocols/adapter-integration/evm/src/.sol` file. See Balancer V2 implementation for reference.
### Testing your implementation
1. Set up test files:
* Copy `evm/test/TemplateSwapAdapter.t.sol`
* Rename to `.t.sol`
2. Write comprehensive tests:
* Test all implemented functions.
* Use fuzz testing (see [Foundry test guide](https://book.getfoundry.sh/forge/tests), especially the chapter for [Fuzz testing](https://book.getfoundry.sh/forge/fuzz-testing))
* Reference existing test files: `BalancerV2SwapAdapter.t.sol`
3. Configure fork testing (run a local mainnet fork against actual contracts and data):
* Set `ETH_RPC_URL` environment variable
* Use your own Ethereum node or services like [Infura](https://infura.io/)
4. Run the tests with
```bash
cd ./evm
forge test
```
### Add implementation to Tycho simulation
Once you have the swap adapter implemented for the new protocol, you will need to:
1. Generate the adapter runtime file by running the [`protocols/adapter-integration/evm/scripts/buildRuntime.sh`](https://github.com/propeller-heads/tycho-indexer/blob/main/protocols/adapter-integration/evm/scripts/buildRuntime.sh) script with the proper input parameters.\
\
For example, in order to build the `Balancer V2` runtime, the following command can be run:\\
```
>>> cd protocols/adapter-integration/evm
>>> ./scripts/buildRuntime.sh -c “BalancerV2SwapAdapter” -s “constructor(address)” -a “0xBA12222222228d8Ba445958a75a0704d566BF2C8”
```
2. Add the associated adapter runtime file to `crates/tycho-simulation/src/protocol/vm/assets`. Make sure to name the file according to the protocol name used by Tycho Indexer in the following format: `Adapter.evm.runtime`. For example: `vm:balancer_v2` will be `BalancerV2Adapter.evm.runtime`. Following this naming format is important as we use an automated name resolution for these files.
### Filtering
If your implementation does not support all pools indexed for a protocol, you can create a filter function to handle this. This filter can then be used when registering an exchange in the `ProtocolStreamBuilder`. See [here](https://github.com/propeller-heads/tycho-indexer/blob/main/crates/tycho-simulation/src/evm/protocol/filters.rs) for example implementations.
---
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