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// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;

import {IDiscountedMKRSKYAdapter} from '../../interfaces/IDiscountedMKRSKYAdapter.sol';
import {IBasicFeed} from '../../interfaces/IBasicFeed.sol';
import {IMkrSky} from '../../interfaces/IMkrSky.sol';
import {IChainlinkAggregator} from '../../interfaces/IChainlinkAggregator.sol';

/**
 * @title DiscountedMKRSKYAdapter
 * @author BGD Labs
 * @notice Price adapter to calculate MKR price based on SKY price, a fixed exchange rate, and a dynamic discount.
 *         Designed for the Aave v3 protocol to be used during the active MKR to SKY migration.
 *
 * @dev Price Formula:
 *      MKR_price = SKY_price * EXCHANGE_RATE * (1 - discount)
 *
 *      Implementation:
 *      ((referenceFeedPrice * EXCHANGE_RATE) * (1e18 - discount())) / 1e18
 *
 *      Parameters:
 *      - REFERENCE_FEED: Chainlink SKY/USD price feed on Ethereum (constant)
 *      - EXCHANGE_RATE: MKR/SKY conversion rate (24000, meaning 1 MKR = 24000 SKY). This is a constant
 *        in the MkrSky contract, but cached here as immutable to avoid external calls on every price query.
 *      - discount(): Dynamically fetched from DISCOUNT_PROVIDER (MkrSky migration contract)
 *        Returns raw fee where 1e18 = 100%, 0.02e18 = 2%
 *
 *      Example:
 *      - SKY/USD price: $0.0665 (6650503 with 8 decimals)
 *      - Exchange rate: 24000
 *      - Discount: 2% (0.02e18)
 *      - Result: (6650503 * 24000) * (1e18 - 0.02e18) / 1e18 = ~$1564 (156489827040 with 8 decimals)
 *
 *      Constants/Immutables:
 *      - DISCOUNT_PROVIDER, REFERENCE_FEED, DESCRIPTION (constants)
 *      - EXCHANGE_RATE (cached from MkrSky.rate()), DECIMALS (immutable)
 *
 *      Assumptions:
 *      - If reference price <= 0 at query time, returns 0 (Aave handles that case)
 *      - DISCOUNT_PROVIDER returns fee (discount) in MkrSky format (1 ether = 100%)
 */
contract DiscountedMKRSKYAdapter is IDiscountedMKRSKYAdapter {
  /// @dev MkrSky migration contract on Ethereum that provides the dynamic fee/discount and exchange rate
  /// @inheritdoc IDiscountedMKRSKYAdapter
  address public constant DISCOUNT_PROVIDER = 0xA1Ea1bA18E88C381C724a75F23a130420C403f9a;

  /// @dev Chainlink SKY/USD price feed on Ethereum
  /// @inheritdoc IDiscountedMKRSKYAdapter
  IChainlinkAggregator public constant REFERENCE_FEED =
    IChainlinkAggregator(0xee10fE5E7aa92dd7b136597449c3d5813cFC5F18);

  string public constant DESCRIPTION = 'MKR/USD (calculated)';

  /// @inheritdoc IBasicFeed
  function description() external pure returns (string memory) {
    return DESCRIPTION;
  }

  /// @inheritdoc IBasicFeed
  uint8 public immutable DECIMALS;

  /// @dev MKR/SKY exchange rate cached from MkrSky.rate() (24000 = 1 MKR = 24000 SKY).
  ///      Constant in MkrSky, cached here to avoid external calls on every price query.
  /// @inheritdoc IDiscountedMKRSKYAdapter
  uint256 public immutable EXCHANGE_RATE;

  constructor() {
    DECIMALS = REFERENCE_FEED.decimals();
    EXCHANGE_RATE = IMkrSky(DISCOUNT_PROVIDER).rate();
  }

  /// @inheritdoc IBasicFeed
  function decimals() external view returns (uint8) {
    return DECIMALS;
  }

  /// @inheritdoc IBasicFeed
  /// @dev Returns 0 when:
  ///      - Reference feed price <= 0
  ///      - Due to integer division truncation when: referenceFeedPrice * 24000 * (1e18 - discount) < 1e18
  ///        For example, with referenceFeedPrice = 1 (smallest unit), zeroes when discount > ~99.996%
  ///        With current SKY/USD price (~$0.0665), zeroes when discount > ~99.9999999994%
  function latestAnswer() external view virtual returns (int256) {
    int256 rawPrice = REFERENCE_FEED.latestAnswer();

    // This should never happen, but as extra validation
    if (rawPrice <= 0) return 0;

    uint256 referenceFeedPrice = uint256(rawPrice);

    // e.g. (6650503 * 24000) * (1e18 - 0.02e18) / 1e18 = 156489827040 (~$1564 with 8 decimals)
    // Safe to cast as final price will always fit into int256
    return int256(((referenceFeedPrice * EXCHANGE_RATE) * (1e18 - discount())) / 1e18);
  }

  /// @inheritdoc IDiscountedMKRSKYAdapter
  function discount() public view returns (uint256) {
    /// @dev In the MkrSky migration contract, 1e18 = 100%, 0.1e18 = 10%, 0.01e18 = 1%
    /// The value is bounded to 100%
    return IMkrSky(DISCOUNT_PROVIDER).fee();
  }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import {IBasicFeed} from './IBasicFeed.sol';
import {IChainlinkAggregator} from './IChainlinkAggregator.sol';

/**
 * @title IDiscountedMKRSKYAdapter
 * @author BGD Labs
 * @notice Interface for the DiscountedMKRSKYAdapter price feed
 */
interface IDiscountedMKRSKYAdapter is IBasicFeed {
  /// @notice MKR/SKY exchange rate (24000, meaning 1 MKR = 24000 SKY). Cached from MkrSky.rate() at deployment.
  function EXCHANGE_RATE() external view returns (uint256);

  /// @notice MkrSky migration contract on Ethereum that provides the dynamic fee/discount
  function DISCOUNT_PROVIDER() external view returns (address);

  /// @notice Current discount applied to reduce the final MKR price
  /// @dev Dynamically fetched from DISCOUNT_PROVIDER. Returns raw fee where 1e18 = 100%
  function discount() external view returns (uint256);

  /// @notice Chainlink SKY/USD price feed on Ethereum (constant)
  function REFERENCE_FEED() external view returns (IChainlinkAggregator);
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface IBasicFeed {
  /**
   * @notice Returns the description of the feed
   * @return string description
   */
  function description() external view returns (string memory);

  /**
   * @notice Returns the feed decimals (for tooling compatibility)
   * @return uint8 decimals
   */
  function DECIMALS() external view returns (uint8);

  /**
   * @notice Returns the feed decimals
   * @return uint8 decimals
   */
  function decimals() external view returns (uint8);

  /**
   * @notice Returns the fixed hardcoded price of the feed
   * @return int256 latestAnswer
   */
  function latestAnswer() external view returns (int256);
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface IMkrSky {
  function fee() external view returns (uint256);
  function rate() external view returns (uint256);
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface IChainlinkAggregator {
  function decimals() external view returns (uint8);

  function latestAnswer() external view returns (int256);

  function latestTimestamp() external view returns (uint256);

  function latestRound() external view returns (uint256);

  function getAnswer(uint256 roundId) external view returns (int256);

  function getTimestamp(uint256 roundId) external view returns (uint256);

  event AnswerUpdated(int256 indexed current, uint256 indexed roundId, uint256 timestamp);
  event NewRound(uint256 indexed roundId, address indexed startedBy);
}

{
  "remappings": [
    "forge-std/=lib/forge-std/src/",
    "aave-address-book/=lib/aave-address-book/src/",
    "aave-helpers/=lib/aave-helpers/src/",
    "solidity-utils/=lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/src/",
    "aave-v3-origin/=lib/aave-address-book/lib/aave-v3-origin/src/",
    "@openzeppelin/contracts-upgradeable/=lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/lib/openzeppelin-contracts-upgradeable/contracts/",
    "@openzeppelin/contracts/=lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/lib/openzeppelin-contracts-upgradeable/lib/openzeppelin-contracts/contracts/",
    "aave-v3-origin-tests/=lib/aave-helpers/lib/aave-address-book/lib/aave-v3-origin/tests/",
    "cl-synchronicity-price-adapter/=lib/cl-synchronicity-price-adapter/",
    "ds-test/=lib/cl-synchronicity-price-adapter/lib/forge-std/lib/ds-test/src/",
    "erc4626-tests/=lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/lib/openzeppelin-contracts-upgradeable/lib/erc4626-tests/",
    "halmos-cheatcodes/=lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/lib/openzeppelin-contracts-upgradeable/lib/halmos-cheatcodes/src/",
    "openzeppelin-contracts-upgradeable/=lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/lib/openzeppelin-contracts-upgradeable/",
    "openzeppelin-contracts/=lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/lib/openzeppelin-contracts-upgradeable/lib/openzeppelin-contracts/"
  ],
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "metadata": {
    "useLiteralContent": false,
    "bytecodeHash": "ipfs",
    "appendCBOR": true
  },
  "outputSelection": {
    "*": {
      "*": [
        "evm.bytecode",
        "evm.deployedBytecode",
        "devdoc",
        "userdoc",
        "metadata",
        "abi"
      ]
    }
  },
  "evmVersion": "shanghai",
  "viaIR": false
}

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