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79 lines
2.9 KiB
79 lines
2.9 KiB
pragma solidity ^0.5.0;
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import "../validation/TimedCrowdsale.sol";
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import "../../math/SafeMath.sol";
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/**
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* @title IncreasingPriceCrowdsale
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* @dev Extension of Crowdsale contract that increases the price of tokens linearly in time.
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* Note that what should be provided to the constructor is the initial and final _rates_, that is,
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* the amount of tokens per wei contributed. Thus, the initial rate must be greater than the final rate.
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*/
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contract IncreasingPriceCrowdsale is TimedCrowdsale {
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using SafeMath for uint256;
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uint256 private _initialRate;
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uint256 private _finalRate;
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/**
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* @dev Constructor, takes initial and final rates of tokens received per wei contributed.
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* @param initialRate Number of tokens a buyer gets per wei at the start of the crowdsale
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* @param finalRate Number of tokens a buyer gets per wei at the end of the crowdsale
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*/
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constructor (uint256 initialRate, uint256 finalRate) public {
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require(finalRate > 0, "IncreasingPriceCrowdsale: final rate is 0");
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// solhint-disable-next-line max-line-length
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require(initialRate > finalRate, "IncreasingPriceCrowdsale: initial rate is not greater than final rate");
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_initialRate = initialRate;
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_finalRate = finalRate;
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}
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/**
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* The base rate function is overridden to revert, since this crowdsale doesn't use it, and
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* all calls to it are a mistake.
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*/
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function rate() public view returns (uint256) {
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revert("IncreasingPriceCrowdsale: rate() called");
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}
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/**
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* @return the initial rate of the crowdsale.
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*/
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function initialRate() public view returns (uint256) {
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return _initialRate;
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}
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/**
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* @return the final rate of the crowdsale.
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*/
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function finalRate() public view returns (uint256) {
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return _finalRate;
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}
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/**
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* @dev Returns the rate of tokens per wei at the present time.
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* Note that, as price _increases_ with time, the rate _decreases_.
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* @return The number of tokens a buyer gets per wei at a given time
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*/
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function getCurrentRate() public view returns (uint256) {
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if (!isOpen()) {
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return 0;
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}
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// solhint-disable-next-line not-rely-on-time
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uint256 elapsedTime = block.timestamp.sub(openingTime());
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uint256 timeRange = closingTime().sub(openingTime());
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uint256 rateRange = _initialRate.sub(_finalRate);
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return _initialRate.sub(elapsedTime.mul(rateRange).div(timeRange));
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}
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/**
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* @dev Overrides parent method taking into account variable rate.
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* @param weiAmount The value in wei to be converted into tokens
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* @return The number of tokens _weiAmount wei will buy at present time
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*/
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function _getTokenAmount(uint256 weiAmount) internal view returns (uint256) {
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uint256 currentRate = getCurrentRate();
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return currentRate.mul(weiAmount);
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}
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}
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