// File: src/contracts/BatchPayments.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import './lib/SafeERC20.sol';
import '@openzeppelin/contracts/access/Ownable.sol';
import './interfaces/ERC20FeeProxy.sol';
import './interfaces/EthereumFeeProxy.sol';
import '@openzeppelin/contracts/security/ReentrancyGuard.sol';

/**
 * @title BatchPayments
 * @notice This contract makes multiple payments with references, in one transaction:
 *          - on: ERC20 Payment Proxy and ETH Payment Proxy of the Request Network protocol
 *          - to: multiple addresses
 *          - fees: ERC20 and ETH proxies fees are paid to the same address.
 *                  An additional batch fee is paid to the same address.
 *         If one transaction of the batch fail, every transactions are reverted.
 */
contract BatchPayments is Ownable, ReentrancyGuard {
  using SafeERC20 for IERC20;

  IERC20FeeProxy public paymentErc20FeeProxy;
  IEthereumFeeProxy public paymentEthFeeProxy;

  // @dev: Between 0 and 1000, i.e: batchFee = 10 represent 1% of fee
  uint256 public batchFee;

  struct Token {
    address tokenAddress;
    uint256 amountAndFee;
    uint256 batchFeeAmount;
  }

  /**
   * @param _paymentErc20FeeProxy The address to the ERC20 payment proxy to use.
   * @param _paymentEthFeeProxy The address to the Ethereum payment proxy to use.
   * @param _owner Owner of the contract.
   */
  constructor(
    address _paymentErc20FeeProxy,
    address _paymentEthFeeProxy,
    address _owner
  ) {
    paymentErc20FeeProxy = IERC20FeeProxy(_paymentErc20FeeProxy);
    paymentEthFeeProxy = IEthereumFeeProxy(_paymentEthFeeProxy);
    transferOwnership(_owner);
    batchFee = 0;
  }

  // batch Eth requires batch contract to receive funds from ethFeeProxy
  receive() external payable {
    require(msg.value == 0, 'Non-payable');
  }

  /**
   * @notice Send a batch of Eth payments w/fees with paymentReferences to multiple accounts.
   *         If one payment failed, the whole batch is reverted
   * @param _recipients List of recipients accounts.
   * @param _amounts List of amounts, corresponding to recipients[].
   * @param _paymentReferences List of paymentRefs, corr. to the recipients[].
   * @param _feeAmounts List of amounts of the payment fee, corr. to the recipients[].
   * @param _feeAddress The fee recipient.
   * @dev It uses EthereumFeeProxy to pay an invoice and fees, with a payment reference.
   *      Make sure: msg.value >= sum(_amouts)+sum(_feeAmounts)+sumBatchFeeAmount
   */
  function batchEthPaymentsWithReference(
    address[] calldata _recipients,
    uint256[] calldata _amounts,
    bytes[] calldata _paymentReferences,
    uint256[] calldata _feeAmounts,
    address payable _feeAddress
  ) external payable nonReentrant {
    require(
      _recipients.length == _amounts.length &&
        _recipients.length == _paymentReferences.length &&
        _recipients.length == _feeAmounts.length,
      'the input arrays must have the same length'
    );

    // amount is used to get the total amount and then used as batch fee amount
    uint256 amount = 0;

    // Batch contract pays the requests thourgh EthFeeProxy
    for (uint256 i = 0; i < _recipients.length; i++) {
      require(address(this).balance >= _amounts[i] + _feeAmounts[i], 'not enough funds');
      amount += _amounts[i];

      paymentEthFeeProxy.transferWithReferenceAndFee{value: _amounts[i] + _feeAmounts[i]}(
        payable(_recipients[i]),
        _paymentReferences[i],
        _feeAmounts[i],
        payable(_feeAddress)
      );
    }

    // amount is updated into batch fee amount
    amount = (amount * batchFee) / 1000;
    // Check that batch contract has enough funds to pay batch fee
    require(address(this).balance >= amount, 'not enough funds for batch fee');
    // Batch pays batch fee
    _feeAddress.transfer(amount);

    // Batch contract transfers the remaining ethers to the payer
    if (address(this).balance > 0) {
      (bool sendBackSuccess, ) = payable(msg.sender).call{value: address(this).balance}('');
      require(sendBackSuccess, 'Could not send remaining funds to the payer');
    }
  }

  /**
   * @notice Send a batch of erc20 payments w/fees with paymentReferences to multiple accounts.
   * @param _tokenAddress Token to transact with.
   * @param _recipients List of recipients accounts.
   * @param _amounts List of amounts, corresponding to recipients[].
   * @param _paymentReferences List of paymentRefs, corr. to the recipients[] and .
   * @param _feeAmounts List of amounts of the payment fee, corr. to the recipients[].
   * @param _feeAddress The fee recipient.
   * @dev Uses ERC20FeeProxy to pay an invoice and fees, with a payment reference.
   *      Make sure the contract has allowance to spend the payer token.
   *      Make sure the payer has enough tokens to pay the amount, the fee, the batch fee
   */
  function batchERC20PaymentsWithReference(
    address _tokenAddress,
    address[] calldata _recipients,
    uint256[] calldata _amounts,
    bytes[] calldata _paymentReferences,
    uint256[] calldata _feeAmounts,
    address _feeAddress
  ) external {
    require(
      _recipients.length == _amounts.length &&
        _recipients.length == _paymentReferences.length &&
        _recipients.length == _feeAmounts.length,
      'the input arrays must have the same length'
    );

    // amount is used to get the total amount and fee, and then used as batch fee amount
    uint256 amount = 0;
    for (uint256 i = 0; i < _recipients.length; i++) {
      amount += _amounts[i] + _feeAmounts[i];
    }

    // Transfer the amount and fee from the payer to the batch contract
    IERC20 requestedToken = IERC20(_tokenAddress);
    require(
      requestedToken.allowance(msg.sender, address(this)) >= amount,
      'Not sufficient allowance for batch to pay'
    );
    require(requestedToken.balanceOf(msg.sender) >= amount, 'not enough funds');
    require(
      safeTransferFrom(_tokenAddress, address(this), amount),
      'payment transferFrom() failed'
    );

    // Batch contract approve Erc20FeeProxy to spend the token
    if (requestedToken.allowance(address(this), address(paymentErc20FeeProxy)) < amount) {
      approvePaymentProxyToSpend(address(requestedToken));
    }

    // Batch contract pays the requests using Erc20FeeProxy
    for (uint256 i = 0; i < _recipients.length; i++) {
      // amount is updated to become the sum of amounts, to calculate batch fee amount
      amount -= _feeAmounts[i];
      paymentErc20FeeProxy.transferFromWithReferenceAndFee(
        _tokenAddress,
        _recipients[i],
        _amounts[i],
        _paymentReferences[i],
        _feeAmounts[i],
        _feeAddress
      );
    }

    // amount is updated into batch fee amount
    amount = (amount * batchFee) / 1000;
    // Check if the payer has enough funds to pay batch fee
    require(requestedToken.balanceOf(msg.sender) >= amount, 'not enough funds for the batch fee');

    // Payer pays batch fee amount
    require(
      safeTransferFrom(_tokenAddress, _feeAddress, amount),
      'batch fee transferFrom() failed'
    );
  }

  /**
   * @notice Send a batch of erc20 payments on multiple tokens w/fees with paymentReferences to multiple accounts.
   * @param _tokenAddresses List of tokens to transact with.
   * @param _recipients List of recipients accounts.
   * @param _amounts List of amounts, corresponding to recipients[].
   * @param _paymentReferences List of paymentRefs, corr. to the recipients[].
   * @param _feeAmounts List of amounts of the payment fee, corr. to the recipients[].
   * @param _feeAddress The fee recipient.
   * @dev It uses ERC20FeeProxy to pay an invoice and fees, with a payment reference.
   *      Make sure the contract has allowance to spend the payer token.
   *      Make sure the payer has enough tokens to pay the amount, the fee, the batch fee
   */
  function batchERC20PaymentsMultiTokensWithReference(
    address[] calldata _tokenAddresses,
    address[] calldata _recipients,
    uint256[] calldata _amounts,
    bytes[] calldata _paymentReferences,
    uint256[] calldata _feeAmounts,
    address _feeAddress
  ) external {
    require(
      _tokenAddresses.length == _recipients.length &&
        _tokenAddresses.length == _amounts.length &&
        _tokenAddresses.length == _paymentReferences.length &&
        _tokenAddresses.length == _feeAmounts.length,
      'the input arrays must have the same length'
    );

    // Create a list of unique tokens used and the amounts associated
    // Only considere tokens having: amounts + feeAmounts > 0
    // batchFeeAmount is the amount's sum, and then, batch fee rate is applied
    Token[] memory uniqueTokens = new Token[](_tokenAddresses.length);
    for (uint256 i = 0; i < _tokenAddresses.length; i++) {
      for (uint256 j = 0; j < _tokenAddresses.length; j++) {
        // If the token is already in the existing uniqueTokens list
        if (uniqueTokens[j].tokenAddress == _tokenAddresses[i]) {
          uniqueTokens[j].amountAndFee += _amounts[i] + _feeAmounts[i];
          uniqueTokens[j].batchFeeAmount += _amounts[i];
          break;
        }
        // If the token is not in the list (amountAndFee = 0), and amount + fee > 0
        if (uniqueTokens[j].amountAndFee == 0 && (_amounts[i] + _feeAmounts[i]) > 0) {
          uniqueTokens[j].tokenAddress = _tokenAddresses[i];
          uniqueTokens[j].amountAndFee = _amounts[i] + _feeAmounts[i];
          uniqueTokens[j].batchFeeAmount = _amounts[i];
          break;
        }
      }
    }

    // The payer transfers tokens to the batch contract and pays batch fee
    for (uint256 i = 0; i < uniqueTokens.length && uniqueTokens[i].amountAndFee > 0; i++) {
      uniqueTokens[i].batchFeeAmount = (uniqueTokens[i].batchFeeAmount * batchFee) / 1000;
      IERC20 requestedToken = IERC20(uniqueTokens[i].tokenAddress);

      require(
        requestedToken.allowance(msg.sender, address(this)) >=
          uniqueTokens[i].amountAndFee + uniqueTokens[i].batchFeeAmount,
        'Not sufficient allowance for batch to pay'
      );
      // check if the payer can pay the amount, the fee, and the batchFee
      require(
        requestedToken.balanceOf(msg.sender) >=
          uniqueTokens[i].amountAndFee + uniqueTokens[i].batchFeeAmount,
        'not enough funds'
      );

      // Transfer only the amount and fee required for the token on the batch contract
      require(
        safeTransferFrom(uniqueTokens[i].tokenAddress, address(this), uniqueTokens[i].amountAndFee),
        'payment transferFrom() failed'
      );

      // Batch contract approves Erc20FeeProxy to spend the token
      if (
        requestedToken.allowance(address(this), address(paymentErc20FeeProxy)) <
        uniqueTokens[i].amountAndFee
      ) {
        approvePaymentProxyToSpend(address(requestedToken));
      }

      // Payer pays batch fee amount
      require(
        safeTransferFrom(uniqueTokens[i].tokenAddress, _feeAddress, uniqueTokens[i].batchFeeAmount),
        'batch fee transferFrom() failed'
      );
    }

    // Batch contract pays the requests using Erc20FeeProxy
    for (uint256 i = 0; i < _recipients.length; i++) {
      paymentErc20FeeProxy.transferFromWithReferenceAndFee(
        _tokenAddresses[i],
        _recipients[i],
        _amounts[i],
        _paymentReferences[i],
        _feeAmounts[i],
        _feeAddress
      );
    }
  }

  /**
   * @notice Authorizes the proxy to spend a new request currency (ERC20).
   * @param _erc20Address Address of an ERC20 used as the request currency.
   */
  function approvePaymentProxyToSpend(address _erc20Address) public {
    IERC20 erc20 = IERC20(_erc20Address);
    uint256 max = 2**256 - 1;
    erc20.safeApprove(address(paymentErc20FeeProxy), max);
  }

  /**
   * @notice Call transferFrom ERC20 function and validates the return data of a ERC20 contract call.
   * @dev This is necessary because of non-standard ERC20 tokens that don't have a return value.
   * @return result The return value of the ERC20 call, returning true for non-standard tokens
   */
  function safeTransferFrom(
    address _tokenAddress,
    address _to,
    uint256 _amount
  ) internal returns (bool result) {
    /* solium-disable security/no-inline-assembly */
    // check if the address is a contract
    assembly {
      if iszero(extcodesize(_tokenAddress)) {
        revert(0, 0)
      }
    }

    // solium-disable-next-line security/no-low-level-calls
    (bool success, ) = _tokenAddress.call(
      abi.encodeWithSignature('transferFrom(address,address,uint256)', msg.sender, _to, _amount)
    );

    assembly {
      switch returndatasize()
      case 0 {
        // Not a standard erc20
        result := 1
      }
      case 32 {
        // Standard erc20
        returndatacopy(0, 0, 32)
        result := mload(0)
      }
      default {
        // Anything else, should revert for safety
        revert(0, 0)
      }
    }

    require(success, 'transferFrom() has been reverted');

    /* solium-enable security/no-inline-assembly */
    return result;
  }

  /*
   * Admin functions to edit the proxies address
   */

  function setBatchFee(uint256 _batchFee) public onlyOwner {
    batchFee = _batchFee;
  }

  function setPaymentErc20FeeProxy(address _paymentErc20FeeProxy) public onlyOwner {
    paymentErc20FeeProxy = IERC20FeeProxy(_paymentErc20FeeProxy);
  }

  function setPaymentEthFeeProxy(address _paymentEthFeeProxy) public onlyOwner {
    paymentEthFeeProxy = IEthereumFeeProxy(_paymentEthFeeProxy);
  }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: src/contracts/lib/SafeERC20.sol



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

import '@openzeppelin/contracts/token/ERC20/ERC20.sol';

/**
 * @title SafeERC20
 * @notice Works around implementations of ERC20 with transferFrom not returning success status.
 */
library SafeERC20 {
  /**
   * @notice Call transferFrom ERC20 function and validates the return data of a ERC20 contract call.
   * @dev This is necessary because of non-standard ERC20 tokens that don't have a return value.
   * @return result The return value of the ERC20 call, returning true for non-standard tokens
   */
  function safeTransferFrom(
    IERC20 _token,
    address _from,
    address _to,
    uint256 _amount
  ) internal returns (bool result) {
    // solium-disable-next-line security/no-low-level-calls
    (bool success, bytes memory data) = address(_token).call(
      abi.encodeWithSignature('transferFrom(address,address,uint256)', _from, _to, _amount)
    );

    return success && (data.length == 0 || abi.decode(data, (bool)));
  }

  /**
   * @notice Call approve ERC20 function and validates the return data of a ERC20 contract call.
   * @dev This is necessary because of non-standard ERC20 tokens that don't have a return value.
   * @return result The return value of the ERC20 call, returning true for non-standard tokens
   */
  function safeApprove(
    IERC20 _token,
    address _spender,
    uint256 _amount
  ) internal returns (bool result) {
    // solium-disable-next-line security/no-low-level-calls
    (bool success, bytes memory data) = address(_token).call(
      abi.encodeWithSignature('approve(address,uint256)', _spender, _amount)
    );

    return success && (data.length == 0 || abi.decode(data, (bool)));
  }

  /**
   * @notice Call transfer ERC20 function and validates the return data of a ERC20 contract call.
   * @dev This is necessary because of non-standard ERC20 tokens that don't have a return value.
   * @return result The return value of the ERC20 call, returning true for non-standard tokens
   */
  function safeTransfer(
    IERC20 _token,
    address _to,
    uint256 _amount
  ) internal returns (bool result) {
    // solium-disable-next-line security/no-low-level-calls
    (bool success, bytes memory data) = address(_token).call(
      abi.encodeWithSignature('transfer(address,uint256)', _to, _amount)
    );

    return success && (data.length == 0 || abi.decode(data, (bool)));
  }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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 Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        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: src/contracts/interfaces/ERC20FeeProxy.sol



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

interface IERC20FeeProxy {
  event TransferWithReferenceAndFee(
    address tokenAddress,
    address to,
    uint256 amount,
    bytes indexed paymentReference,
    uint256 feeAmount,
    address feeAddress
  );

  function transferFromWithReferenceAndFee(
    address _tokenAddress,
    address _to,
    uint256 _amount,
    bytes calldata _paymentReference,
    uint256 _feeAmount,
    address _feeAddress
  ) external;
}

// File: src/contracts/interfaces/EthereumFeeProxy.sol



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

interface IEthereumFeeProxy {
  event TransferWithReferenceAndFee(
    address to,
    uint256 amount,
    bytes indexed paymentReference,
    uint256 feeAmount,
    address feeAddress
  );

  function transferWithReferenceAndFee(
    address payable _to,
    bytes calldata _paymentReference,
    uint256 _feeAmount,
    address payable _feeAddress
  ) external payable;
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

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

        _;

        // 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/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);

        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        unchecked {
            _approve(sender, _msgSender(), currentAllowance - amount);
        }

        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }
        _balances[recipient] += amount;

        emit Transfer(sender, recipient, amount);

        _afterTokenTransfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// 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;
    }
}