// SPDX-License-Identifier: MIT

pragma solidity 0.8.6;

/**
* @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);
}

/**
* @dev Collection of functions related to the address type
*/
library Address {
/**
* @dev Returns true if `account` is a contract.
*
* [IMPORTANT]
* ====
* It is unsafe to assume that an address for which this function returns
* false is an externally-owned account (EOA) and not a contract.
*
* Among others, `isContract` will return false for the following
* types of addresses:
*
* - an externally-owned account
* - a contract in construction
* - an address where a contract will be created
* - an address where a contract lived, but was destroyed
* ====
*/
function isContract(address account) internal view returns (bool) {
// This method relies on extcodesize, which returns 0 for contracts in
// construction, since the code is only stored at the end of the
// constructor execution.

uint256 size;
assembly {
size := extcodesize(account)
}
return size > 0;
}

/**
* @dev Replacement for Solidity's `transfer`: sends `amount` wei to
* `recipient`, forwarding all available gas and reverting on errors.
*
* https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
* of certain opcodes, possibly making contracts go over the 2300 gas limit
* imposed by `transfer`, making them unable to receive funds via
* `transfer`. {sendValue} removes this limitation.
*
* https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
*
* IMPORTANT: because control is transferred to `recipient`, care must be
* taken to not create reentrancy vulnerabilities. Consider using
* {ReentrancyGuard} or the
* https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
*/
function sendValue(address payable recipient, uint256 amount) internal {
require(address(this).balance >= amount, "Address: insufficient balance");

(bool success, ) = recipient.call{value: amount}("");
require(success, "Address: unable to send value, recipient may have reverted");
}

/**
* @dev Performs a Solidity function call using a low level `call`. A
* plain `call` is an unsafe replacement for a function call: use this
* function instead.
*
* If `target` reverts with a revert reason, it is bubbled up by this
* function (like regular Solidity function calls).
*
* Returns the raw returned data. To convert to the expected return value,
* use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
*
* Requirements:
*
* - `target` must be a contract.
* - calling `target` with `data` must not revert.
*
* _Available since v3.1._
*/
function functionCall(address target, bytes memory data) internal returns (bytes memory) {
return functionCall(target, data, "Address: low-level call failed");
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
* `errorMessage` as a fallback revert reason when `target` reverts.
*
* _Available since v3.1._
*/
function functionCall(
address target,
bytes memory data,
string memory errorMessage
) internal returns (bytes memory) {
return functionCallWithValue(target, data, 0, errorMessage);
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
* but also transferring `value` wei to `target`.
*
* Requirements:
*
* - the calling contract must have an ETH balance of at least `value`.
* - the called Solidity function must be `payable`.
*
* _Available since v3.1._
*/
function functionCallWithValue(
address target,
bytes memory data,
uint256 value
) internal returns (bytes memory) {
return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
}

/**
* @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
* with `errorMessage` as a fallback revert reason when `target` reverts.
*
* _Available since v3.1._
*/
function functionCallWithValue(
address target,
bytes memory data,
uint256 value,
string memory errorMessage
) internal returns (bytes memory) {
require(address(this).balance >= value, "Address: insufficient balance for call");
require(isContract(target), "Address: call to non-contract");

(bool success, bytes memory returndata) = target.call{value: value}(data);
return _verifyCallResult(success, returndata, errorMessage);
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
* but performing a static call.
*
* _Available since v3.3._
*/
function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
return functionStaticCall(target, data, "Address: low-level static call failed");
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
* but performing a static call.
*
* _Available since v3.3._
*/
function functionStaticCall(
address target,
bytes memory data,
string memory errorMessage
) internal view returns (bytes memory) {
require(isContract(target), "Address: static call to non-contract");

(bool success, bytes memory returndata) = target.staticcall(data);
return _verifyCallResult(success, returndata, errorMessage);
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
* but performing a delegate call.
*
* _Available since v3.4._
*/
function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
return functionDelegateCall(target, data, "Address: low-level delegate call failed");
}

/**
* @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
* but performing a delegate call.
*
* _Available since v3.4._
*/
function functionDelegateCall(
address target,
bytes memory data,
string memory errorMessage
) internal returns (bytes memory) {
require(isContract(target), "Address: delegate call to non-contract");

(bool success, bytes memory returndata) = target.delegatecall(data);
return _verifyCallResult(success, returndata, errorMessage);
}

function _verifyCallResult(
bool success,
bytes memory returndata,
string memory errorMessage
) private pure returns (bytes memory) {
if (success) {
return returndata;
} else {
// Look for revert reason and bubble it up if present
if (returndata.length > 0) {
// The easiest way to bubble the revert reason is using memory via assembly

assembly {
let returndata_size := mload(returndata)
revert(add(32, returndata), returndata_size)
}
} else {
revert(errorMessage);
}
}
}
}

/**
* @title SafeERC20
* @dev Wrappers around ERC20 operations that throw on failure (when the token
* contract returns false). Tokens that return no value (and instead revert or
* throw on failure) are also supported, non-reverting calls are assumed to be
* successful.
* To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
* which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
*/
library SafeERC20 {
using Address for address;

function safeTransfer(
IERC20 token,
address to,
uint256 value
) internal {
_callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
}

function safeTransferFrom(
IERC20 token,
address from,
address to,
uint256 value
) internal {
_callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
}

/**
* @dev Deprecated. This function has issues similar to the ones found in
* {IERC20-approve}, and its usage is discouraged.
*
* Whenever possible, use {safeIncreaseAllowance} and
* {safeDecreaseAllowance} instead.
*/
function safeApprove(
IERC20 token,
address spender,
uint256 value
) internal {
// safeApprove should only be called when setting an initial allowance,
// or when resetting it to zero. To increase and decrease it, use
// 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
require((value == 0) || (token.allowance(address(this), spender) == 0), "SafeERC20: approve from non-zero to non-zero allowance");
_callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
}

function safeIncreaseAllowance(
IERC20 token,
address spender,
uint256 value
) internal {
uint256 newAllowance = token.allowance(address(this), spender) value;
_callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
}

function safeDecreaseAllowance(
IERC20 token,
address spender,
uint256 value
) internal {
unchecked {
uint256 oldAllowance = token.allowance(address(this), spender);
require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
uint256 newAllowance = oldAllowance - value;
_callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
}
}

/**
* @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
* on the return value: the return value is optional (but if data is returned, it must not be false).
* @param token The token targeted by the call.
* @param data The call data (encoded using abi.encode or one of its variants).
*/
function _callOptionalReturn(IERC20 token, bytes memory data) private {
// We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
// we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
// the target address contains contract code and also asserts for success in the low-level call.

bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
if (returndata.length > 0) {
// Return data is optional
require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
}
}
}

/**
* @title Crowdsale
* @dev Crowdsale is a base contract for managing a token crowdsale,
* allowing investors to purchase tokens with ether. This contract implements
* such functionality in its most fundamental form and can be extended to provide additional
* functionality and/or custom behavior.
* The external interface represents the basic interface for purchasing tokens, and conform
* the base architecture for crowdsales. They are *not* intended to be modified / overriden.
* The internal interface conforms the extensible and modifiable surface of crowdsales. Override
* the methods to add functionality. Consider using 'super' where appropriate to concatenate
* behavior.
*/
contract Crowdsale {
using SafeERC20 for IERC20;

// The token being sold
address public token;

// Address where funds are collected
address payable public wallet;

// How many token units a buyer gets per wei.
// The rate is the conversion between wei and the smallest and indivisible token unit.
// So, if you are using a rate of 1 with a DetailedERC20 token with 3 decimals called TOK
// 1 wei will give you 1 unit, or 0.001 TOK.
uint256 public rate;

// Amount of wei raised
uint256 public weiRaised;

uint256 public minWeiAmount;

/**
* Event for token purchase logging
* @param purchaser who paid for the tokens
* @param beneficiary who got the tokens
* @param value weis paid for purchase
* @param amount amount of tokens purchased
*/
event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);

/**
* @param _rate Number of token units a buyer gets per wei
* @param _wallet Address where collected funds will be forwarded to
* @param _token Address of the token being sold
*/
constructor(
uint256 _rate,
uint256 _minWeiAmount,
address payable _wallet,
address _token
) {
require(_rate > 0);
require(_minWeiAmount > 0);
require(_wallet != address(0));

rate = _rate;
minWeiAmount = _minWeiAmount;
wallet = _wallet;
token = _token;
}

// -----------------------------------------
// Crowdsale external interface
// -----------------------------------------

/**
* @dev low level token purchase ***DO NOT OVERRIDE***
* @param _beneficiary Address performing the token purchase
*/
function buyTokens(address _beneficiary) public payable {
uint256 weiAmount = msg.value;
require(weiAmount >= minWeiAmount, "BNB amount is too small");

_preValidatePurchase(_beneficiary, weiAmount);

// calculate token amount to be created
uint256 tokens = _getTokenAmount(weiAmount);

// update state
weiRaised = weiAmount;

_processPurchase(_beneficiary, tokens);
emit TokenPurchase(msg.sender, _beneficiary, weiAmount, tokens);

_updatePurchasingState(_beneficiary, weiAmount);

_forwardFunds();
_postValidatePurchase(_beneficiary, weiAmount);
}

// -----------------------------------------
// Internal interface (extensible)
// -----------------------------------------

/**
* @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met. Use super to concatenate validations.
* @param _beneficiary Address performing the token purchase
* @param _weiAmount Value in wei involved in the purchase
*/
function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal pure {
require(_beneficiary != address(0));
require(_weiAmount > 0);
}

/**
* @dev Validation of an executed purchase. Observe state and use revert statements to undo rollback when valid conditions are not met.
* @param _beneficiary Address performing the token purchase
* @param _weiAmount Value in wei involved in the purchase
*/
function _postValidatePurchase(address _beneficiary, uint256 _weiAmount) internal pure {
// optional override
}

/**
* @dev Source of tokens. Override this method to modify the way in which the crowdsale ultimately gets and sends its tokens.
* @param _beneficiary Address performing the token purchase
* @param _tokenAmount Number of tokens to be emitted
*/
function _deliverTokens(address _beneficiary, uint256 _tokenAmount) internal virtual {
IERC20(token).safeTransfer(_beneficiary, _tokenAmount);
}

/**
* @dev Executed when a purchase has been validated and is ready to be executed. Not necessarily emits/sends tokens.
* @param _beneficiary Address receiving the tokens
* @param _tokenAmount Number of tokens to be purchased
*/
function _processPurchase(address _beneficiary, uint256 _tokenAmount) internal {
_deliverTokens(_beneficiary, _tokenAmount);
}

/**
* @dev Override for extensions that require an internal state to check for validity (current user contributions, etc.)
* @param _beneficiary Address receiving the tokens
* @param _weiAmount Value in wei involved in the purchase
*/
function _updatePurchasingState(address _beneficiary, uint256 _weiAmount) internal {
// optional override
}

/**
* @dev Override to extend the way in which ether is converted to tokens.
* @param _weiAmount Value in wei to be converted into tokens
* @return Number of tokens that can be purchased with the specified _weiAmount
*/
function _getTokenAmount(uint256 _weiAmount) internal view returns (uint256) {
return _weiAmount * rate;
}

/**
* @dev Determines how ETH is stored/forwarded on purchases.
*/
function _forwardFunds() internal {
wallet.transfer(msg.value);
}

function getTokenAmountAvailable() public view virtual returns (uint256) {
return IERC20(token).balanceOf(address(this));
}

function getMaxReceivingTokenToPurchase() public view returns (uint256) {
return getTokenAmountAvailable() / rate;
}

/**
* @dev fallback function ***DO NOT OVERRIDE***
*/
receive() external payable {
buyTokens(msg.sender);
}
}

contract MeebSaleByBNB is Crowdsale {
using SafeERC20 for IERC20;

address public governance;
mapping(address => bool) public admin;

mapping(address => uint256) public balanceOf;

uint256 public cap;

constructor(
uint256 _cap,
uint256 _rate,
uint256 _minWeiAmount,
address payable _wallet
) Crowdsale(_rate, _minWeiAmount, _wallet, address(0)) {
cap = _cap;
governance = msg.sender;
}

modifier onlyGovernance() {
require(msg.sender == governance, "!governance");
_;
}

modifier onlyAdmin() {
require(admin[msg.sender] || msg.sender == governance, "!admin");
_;
}

function setGovernance(address _governance) external onlyGovernance {
governance = _governance;
}

function setAdmin(address _account, bool _isAdmin) external onlyGovernance {
admin[_account] = _isAdmin;
}

function setRate(uint256 _rate) external onlyAdmin {
require(_rate > 0);
rate = _rate;
}

function setCap(uint256 _cap) public onlyAdmin {
cap = _cap;
}

function stopSale() external onlyAdmin {
setCap(0);
}

function buyTokensSelf() external payable {
buyTokens(msg.sender);
}

function setMinWeiAmount(uint256 _minWeiAmount) external onlyAdmin {
require(_minWeiAmount > 0);
minWeiAmount = _minWeiAmount;
}

function getTokenAmountAvailable() public view override returns (uint256) {
return cap;
}

function getMaxBnbToPurchase() external view returns (uint256) {
return getTokenAmountAvailable() / rate;
}

function _deliverTokens(address _beneficiary, uint256 _tokenAmount) internal override {
balanceOf[_beneficiary] = _tokenAmount;
cap -= _tokenAmount;
}

function governanceRecoverUnsupported(
IERC20 _token,
address _to,
uint256 _amount
) external onlyGovernance {
_token.transfer(_to, _amount);
}
}