aave-protocol-v2/contracts/configuration/LendingPoolAddressesProviderRegistry.sol

// SPDX-License-Identifier: agpl-3.0
pragma solidity ^0.6.8;

import {Ownable} from '@openzeppelin/contracts/access/Ownable.sol';
import {
  ILendingPoolAddressesProviderRegistry
} from '../interfaces/ILendingPoolAddressesProviderRegistry.sol';

/**
 * @title LendingPoolAddressesProviderRegistry contract
 * @notice contains the list of active addresses providers
 * @author Aave
 **/

contract LendingPoolAddressesProviderRegistry is Ownable, ILendingPoolAddressesProviderRegistry {
  mapping(address => uint256) addressesProviders;
  address[] addressesProvidersList;

  //require error messages
  string private constant PROVIDER_NOT_REGISTERED = '1'; // 'Provider is not registered'

  /**
   * @dev returns if an addressesProvider is registered or not
   * @param provider the addresses provider
   * @return true if the addressesProvider is registered, false otherwise
   **/
  function isAddressesProviderRegistered(address provider)
    external
    override
    view
    returns (uint256)
  {
    return addressesProviders[provider];
  }

  /**
   * @dev returns the list of active addressesProviders
   * @return the list of addressesProviders
   **/
  function getAddressesProvidersList() external override view returns (address[] memory) {
    uint256 maxLength = addressesProvidersList.length;

    address[] memory activeProviders = new address[](maxLength);

    for (uint256 i = 0; i < addressesProvidersList.length; i++) {
      if (addressesProviders[addressesProvidersList[i]] > 0) {
        activeProviders[i] = addressesProvidersList[i];
      }
    }

    return activeProviders;
  }

  /**
   * @dev adds a lending pool to the list of registered lending pools
   * @param provider the pool address to be registered
   **/
  function registerAddressesProvider(address provider, uint256 id) external override onlyOwner {
    addressesProviders[provider] = id;
    _addToAddressesProvidersList(provider);
    emit AddressesProviderRegistered(provider);
  }

  /**
   * @dev removes a lending pool from the list of registered lending pools
   * @param provider the pool address to be unregistered
   **/
  function unregisterAddressesProvider(address provider) external override onlyOwner {
    require(addressesProviders[provider] > 0, PROVIDER_NOT_REGISTERED);
    addressesProviders[provider] = 0;
    emit AddressesProviderUnregistered(provider);
  }

  /**
   * @dev adds to the list of the addresses providers, if it wasn't already added before
   * @param provider the pool address to be added
   **/
  function _addToAddressesProvidersList(address provider) internal {
    for (uint256 i = 0; i < addressesProvidersList.length; i++) {
      if (addressesProvidersList[i] == provider) {
        return;
      }
    }

    addressesProvidersList.push(provider);
  }
}