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pragma solidity ^0.4.24;
import "../token/ERC20/IERC20.sol";
import "../math/SafeMath.sol";
import "../token/ERC20/SafeERC20.sol";
import "../utils/ReentrancyGuard.sol";
/**
* @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 / overridden.
* 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 is ReentrancyGuard {
using SafeMath for uint256;
using SafeERC20 for IERC20;
// The token being sold
IERC20 private _token;
// Address where funds are collected
address private _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 ERC20Detailed token with 3 decimals called TOK
// 1 wei will give you 1 unit, or 0.001 TOK.
uint256 private _rate;
// Amount of wei raised
uint256 private _weiRaised;
/**
* 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 TokensPurchased(
address indexed purchaser,
address indexed beneficiary,
uint256 value,
uint256 amount
);
/**
* @param rate Number of token units a buyer gets per wei
* @dev 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 ERC20Detailed token
* with 3 decimals called TOK, 1 wei will give you 1 unit, or 0.001 TOK.
* @param wallet Address where collected funds will be forwarded to
* @param token Address of the token being sold
*/
constructor(uint256 rate, address wallet, IERC20 token) internal {
require(rate > 0);
require(wallet != address(0));
require(token != address(0));
_rate = rate;
_wallet = wallet;
_token = token;
}
// -----------------------------------------
// Crowdsale external interface
// -----------------------------------------
/**
* @dev fallback function ***DO NOT OVERRIDE***
* Note that other contracts will transfer fund with a base gas stipend
* of 2300, which is not enough to call buyTokens. Consider calling
* buyTokens directly when purchasing tokens from a contract.
*/
function () external payable {
buyTokens(msg.sender);
}
/**
* @return the token being sold.
*/
function token() public view returns(IERC20) {
return _token;
}
/**
* @return the address where funds are collected.
*/
function wallet() public view returns(address) {
return _wallet;
}
/**
* @return the number of token units a buyer gets per wei.
*/
function rate() public view returns(uint256) {
return _rate;
}
/**
* @return the amount of wei raised.
*/
function weiRaised() public view returns (uint256) {
return _weiRaised;
}
/**
* @dev low level token purchase ***DO NOT OVERRIDE***
* This function has a non-reentrancy guard, so it shouldn't be called by
* another `nonReentrant` function.
* @param beneficiary Recipient of the token purchase
*/
function buyTokens(address beneficiary) public nonReentrant payable {
uint256 weiAmount = msg.value;
_preValidatePurchase(beneficiary, weiAmount);
// calculate token amount to be created
uint256 tokens = _getTokenAmount(weiAmount);
// update state
_weiRaised = _weiRaised.add(weiAmount);
_processPurchase(beneficiary, tokens);
emit TokensPurchased(
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` in contracts that inherit from Crowdsale to extend their validations.
* Example from CappedCrowdsale.sol's _preValidatePurchase method:
* super._preValidatePurchase(beneficiary, weiAmount);
* require(weiRaised().add(weiAmount) <= cap);
* @param beneficiary Address performing the token purchase
* @param weiAmount Value in wei involved in the purchase
*/
function _preValidatePurchase(
address beneficiary,
uint256 weiAmount
)
internal
view
{
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
view
{
// 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
{
_token.safeTransfer(beneficiary, tokenAmount);
}
/**
* @dev Executed when a purchase has been validated and is ready to be executed. Doesn't necessarily emit/send 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.mul(_rate);
}
/**
* @dev Determines how ETH is stored/forwarded on purchases.
*/
function _forwardFunds() internal {
_wallet.transfer(msg.value);
}
}