// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/security/Pausable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (security/Pausable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        _requireNotPaused();
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        _requirePaused();
        _;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Throws if the contract is paused.
     */
    function _requireNotPaused() internal view virtual {
        require(!paused(), "Pausable: paused");
    }

    /**
     * @dev Throws if the contract is not paused.
     */
    function _requirePaused() internal view virtual {
        require(paused(), "Pausable: not paused");
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// File: @openzeppelin/contracts/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: contracts/interfaces/IERC20.sol



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

interface IERC20 {
    // transfer and tranferFrom have been removed, because they don't work on all tokens (some aren't ERC20 complaint).
    // By removing them you can't accidentally use them.
    // name, symbol and decimals have been removed, because they are optional and sometimes wrongly implemented (MKR).
    // Use BoringERC20 with `using BoringERC20 for IERC20` and call `safeTransfer`, `safeTransferFrom`, etc instead.
    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /// @notice EIP 2612
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;
}

interface IStrictERC20 {
    // This is the strict ERC20 interface. Don't use this, certainly not if you don't control the ERC20 token you're calling.
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);
    function totalSupply() external view returns (uint256);
    function balanceOf(address _owner) external view returns (uint256 balance);
    function transfer(address _to, uint256 _value) external returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) external returns (bool success);
    function approve(address _spender, uint256 _value) external returns (bool success);
    function allowance(address _owner, address _spender) external view returns (uint256 remaining);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /// @notice EIP 2612
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;
}

// File: contracts/libraries/BoringERC20.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "../interfaces/IERC20.sol";

// solhint-disable avoid-low-level-calls

library BoringERC20 {
    bytes4 private constant SIG_SYMBOL = 0x95d89b41; // symbol()
    bytes4 private constant SIG_NAME = 0x06fdde03; // name()
    bytes4 private constant SIG_DECIMALS = 0x313ce567; // decimals()
    bytes4 private constant SIG_BALANCE_OF = 0x70a08231; // balanceOf(address)
    bytes4 private constant SIG_TOTALSUPPLY = 0x18160ddd; // balanceOf(address)
    bytes4 private constant SIG_TRANSFER = 0xa9059cbb; // transfer(address,uint256)
    bytes4 private constant SIG_TRANSFER_FROM = 0x23b872dd; // transferFrom(address,address,uint256)

    function returnDataToString(bytes memory data) internal pure returns (string memory) {
        if (data.length >= 64) {
            return abi.decode(data, (string));
        } else if (data.length == 32) {
            uint8 i = 0;
            while (i < 32 && data[i] != 0) {
                i++;
            }
            bytes memory bytesArray = new bytes(i);
            for (i = 0; i < 32 && data[i] != 0; i++) {
                bytesArray[i] = data[i];
            }
            return string(bytesArray);
        } else {
            return "???";
        }
    }

    /// @notice Provides a safe ERC20.symbol version which returns '???' as fallback string.
    /// @param token The address of the ERC-20 token contract.
    /// @return (string) Token symbol.
    function safeSymbol(IERC20 token) internal view returns (string memory) {
        (bool success, bytes memory data) = address(token).staticcall(abi.encodeWithSelector(SIG_SYMBOL));
        return success ? returnDataToString(data) : "???";
    }

    /// @notice Provides a safe ERC20.name version which returns '???' as fallback string.
    /// @param token The address of the ERC-20 token contract.
    /// @return (string) Token name.
    function safeName(IERC20 token) internal view returns (string memory) {
        (bool success, bytes memory data) = address(token).staticcall(abi.encodeWithSelector(SIG_NAME));
        return success ? returnDataToString(data) : "???";
    }

    /// @notice Provides a safe ERC20.decimals version which returns '18' as fallback value.
    /// @param token The address of the ERC-20 token contract.
    /// @return (uint8) Token decimals.
    function safeDecimals(IERC20 token) internal view returns (uint8) {
        (bool success, bytes memory data) = address(token).staticcall(abi.encodeWithSelector(SIG_DECIMALS));
        return success && data.length == 32 ? abi.decode(data, (uint8)) : 18;
    }

    /// @notice Provides a gas-optimized balance check to avoid a redundant extcodesize check in addition to the returndatasize check.
    /// @param token The address of the ERC-20 token.
    /// @param to The address of the user to check.
    /// @return amount The token amount.
    function safeBalanceOf(IERC20 token, address to) internal view returns (uint256 amount) {
        (bool success, bytes memory data) = address(token).staticcall(abi.encodeWithSelector(SIG_BALANCE_OF, to));
        require(success && data.length >= 32, "BoringERC20: BalanceOf failed");
        amount = abi.decode(data, (uint256));
    }

    /// @notice Provides a gas-optimized totalSupply to avoid a redundant extcodesize check in addition to the returndatasize check.
    /// @param token The address of the ERC-20 token.
    /// @return totalSupply The token totalSupply.
    function safeTotalSupply(IERC20 token) internal view returns (uint256 totalSupply) {
        (bool success, bytes memory data) = address(token).staticcall(abi.encodeWithSelector(SIG_TOTALSUPPLY));
        require(success && data.length >= 32, "BoringERC20: totalSupply failed");
        totalSupply = abi.decode(data, (uint256));
    }

    /// @notice Provides a safe ERC20.transfer version for different ERC-20 implementations.
    /// Reverts on a failed transfer.
    /// @param token The address of the ERC-20 token.
    /// @param to Transfer tokens to.
    /// @param amount The token amount.
    function safeTransfer(
        IERC20 token,
        address to,
        uint256 amount
    ) internal {
        (bool success, bytes memory data) = address(token).call(abi.encodeWithSelector(SIG_TRANSFER, to, amount));
        require(success && (data.length == 0 || abi.decode(data, (bool))), "BoringERC20: Transfer failed");
    }

    /// @notice Provides a safe ERC20.transferFrom version for different ERC-20 implementations.
    /// Reverts on a failed transfer.
    /// @param token The address of the ERC-20 token.
    /// @param from Transfer tokens from.
    /// @param to Transfer tokens to.
    /// @param amount The token amount.
    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 amount
    ) internal {
        (bool success, bytes memory data) = address(token).call(abi.encodeWithSelector(SIG_TRANSFER_FROM, from, to, amount));
        require(success && (data.length == 0 || abi.decode(data, (bool))), "BoringERC20: TransferFrom failed");
    }
}

// File: contracts/Redemption.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.19;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/Pausable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "./libraries/BoringERC20.sol";

contract Redemption is Ownable, Pausable, ReentrancyGuard {
    using BoringERC20 for IERC20;
    IERC20 public fromToken;
    address[] public toTokens;
    uint256 public immutable fromDenominator;
    mapping(address => uint256) public exchangeRates;

    event Redeemed(
        address indexed user,
        address indexed toToken,
        uint256 amount
    );
    event TokenAdded(address indexed token, uint256 exchangeRate);
    event TokenRemoved(address indexed token);
    event ExchangeRateChanged(address indexed token, uint256 exchangeRate);

    constructor(
        IERC20 _fromToken
    ) {
        fromToken = _fromToken;
        fromDenominator = 10 ** fromToken.safeDecimals();
    }

    /**
     * @dev Function for redeeming fromToken for other ERC20 tokens.
     * @param amount The amount of fromToken to be redeemed.
     */
    function redeem(uint256 amount) public whenNotPaused nonReentrant {
        require(
            fromToken.safeBalanceOf(msg.sender) >= amount,
            "Insufficient balance"
        );

        fromToken.safeTransferFrom(msg.sender, address(this), amount);

        for (uint256 i = 0; i < toTokens.length; i++) {
            uint256 toAmount = (amount * exchangeRates[toTokens[i]]) /
                fromDenominator;
            require(toAmount > 0, "Amount not enough");
            require(
                IERC20(toTokens[i]).safeBalanceOf(address(this)) >= toAmount,
                "Insufficient balance of contract"
            );
            IERC20(toTokens[i]).safeTransfer(msg.sender, toAmount);
            emit Redeemed(msg.sender, toTokens[i], toAmount);
        }
    }

    /**
     * @dev Function that allows the owner to add a new supported token.
     * @param token The address of the token being added.
     * @param exchangeRate The exchange rate of the new token.
     * @dev When setting exchangeRate, use the decimals of the token to be added(exchangeRate = Coefficient * 10**decimals )
     */
    function addToken(address token, uint256 exchangeRate) public onlyOwner {
        require(token != address(0), "Token address cannot be zero");
        require(exchangeRate > 0, "ExchangeRate cannot be 0");
        require(exchangeRates[token] == 0, "Token already exists");

        toTokens.push(token);
        exchangeRates[token] = exchangeRate;
        emit TokenAdded(token, exchangeRate);
    }

    /**
     * @dev Function that allows the owner to remove a supported token.
     * @param index The index of the token being removed.
     */
    function removeToken(uint256 index) public onlyOwner {
        address _token = toTokens[index];
        delete exchangeRates[_token];
        toTokens[index] = toTokens[toTokens.length - 1];
        toTokens.pop();
        emit TokenRemoved(_token);
    }

    /**
     * @dev Function that allows the owner to set the exchange rate of a supported token.
     * @param token The address of the token for which the exchange rate is being set.
     * @param exchangeRate The new exchange rate of the token.
     * @dev When setting exchangeRate, use the decimals of the token to be seted(exchangeRate = Coefficient * 10**decimals )
     */
    function setExchangeRate(
        address token,
        uint256 exchangeRate
    ) public onlyOwner {
        require(exchangeRate > 0, "Token rate cannot be zero");
        require(exchangeRates[token] > 0, "Token does not exist");
        exchangeRates[token] = exchangeRate;
        emit ExchangeRateChanged(token, exchangeRate);
    }

    /**
     * @dev Function that set pause and unpause.
     */
    function pause() public onlyOwner {
        paused() ? _unpause() : _pause();
    }

    /**
     * @dev Function for emergency withdrawal of tokens.
     * @param token Token address for emergency withdrawal.
     */
    function emergencyWithdraw(IERC20 token) external onlyOwner {
        token.safeTransfer(owner(), token.safeBalanceOf(address(this)));
    }

    /**
     * @dev Function for calculating the exchange of fromToken for other ERC20 tokens.
     * @param amount The amount of fromToken to be redeemed.
     */
    function calculateRedeem(
        uint256 amount
    ) external view returns (address[] memory, uint256[] memory) {
        uint[] memory toAmount = new uint[](toTokens.length);
        for (uint256 i = 0; i < toTokens.length; i++) {
            toAmount[i] =
                (amount * exchangeRates[toTokens[i]]) /
                fromDenominator;
            require(toAmount[i] > 0, "Amount not enough");
        }

        return (toTokens, toAmount);
    }
}