361 lines
14 KiB
Solidity
361 lines
14 KiB
Solidity
pragma solidity > 0.6.11;
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// SPDX-License-Identifier: GPL-3.0-or-later
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// TODO: assign bitmask values to contants
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contract RedistributedDemurrageToken {
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address public owner;
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uint256 public decimals;
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string public name;
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string public symbol;
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uint256 public totalSupply;
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uint256 public periodStart;
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uint256 public periodDuration;
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uint256 public taxLevel; // PPM
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uint256 public demurrageModifier; // PPM
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bytes32[] public redistributions; // uint1(isFractional) | uint1(unused) | uint38(participants) | uint160(value) | uint56(period)
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mapping (address => bytes32) account; // uint20(unused) | uint56(period) | uint160(value)
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mapping (address => bool) minter;
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mapping (address => mapping (address => uint256 ) ) allowance; // holder -> spender -> amount (amount is subject to demurrage)
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address sinkAddress; // receives redistribuion remainders
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event Transfer(address indexed _from, address indexed _to, uint256 _value);
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event Approval(address indexed _owner, address indexed _spender, uint256 _value);
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event Mint(address indexed _minter, address indexed _beneficiary, uint256 _value);
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//event Debug(uint256 _foo);
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event Taxed(uint256 indexed _period, uint256 remainder);
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event Redistribution(address indexed _account, uint256 indexed _period, uint256 _value);
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constructor(string memory _name, string memory _symbol, uint8 _decimals, uint32 _taxLevel, uint256 _period, address _defaultSinkAddress) public {
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owner = msg.sender;
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minter[owner] = true;
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periodStart = block.number;
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periodDuration = _period;
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taxLevel = _taxLevel;
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name = _name;
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symbol = _symbol;
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decimals = _decimals;
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demurrageModifier = 1000000;
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sinkAddress = _defaultSinkAddress;
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bytes32 initialRedistribution = toRedistribution(0, 0, 1);
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redistributions.push(initialRedistribution);
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}
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// Given address will be allowed to call the mintTo() function
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function addMinter(address _minter) public returns (bool) {
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require(msg.sender == owner);
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minter[_minter] = true;
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return true;
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}
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/// ERC20
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function balanceOf(address _account) public view returns (uint256) {
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uint256 baseBalance = getBaseBalance(_account);
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uint256 inverseModifier = 1000000 - demurrageModifier;
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uint256 balanceModifier = (inverseModifier * baseBalance) / 1000000;
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return baseBalance - balanceModifier;
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}
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/// Balance unmodified by demurrage
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function getBaseBalance(address _account) private view returns (uint256) {
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return uint256(account[_account]) & 0x00ffffffffffffffffffffffffffffffffffffffff;
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}
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/// Increases base balance for a single account
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function increaseBaseBalance(address _account, uint256 _delta) private returns (bool) {
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uint256 oldBalance;
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uint256 newBalance;
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oldBalance = getBaseBalance(_account);
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newBalance = oldBalance + _delta;
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require(uint160(newBalance) > uint160(oldBalance), 'ERR_WOULDWRAP'); // revert if increase would result in a wrapped value
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account[_account] &= bytes32(0xffffffffffffffffffffffff0000000000000000000000000000000000000000);
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account[_account] |= bytes32(newBalance & 0x00ffffffffffffffffffffffffffffffffffffffff);
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return true;
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}
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/// Decreases base balance for a single account
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function decreaseBaseBalance(address _account, uint256 _delta) private returns (bool) {
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uint256 oldBalance;
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uint256 newBalance;
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oldBalance = getBaseBalance(_account);
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require(oldBalance >= _delta, 'ERR_OVERSPEND'); // overspend guard
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newBalance = oldBalance - _delta;
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account[_account] &= bytes32(0xffffffffffffffffffffffff0000000000000000000000000000000000000000);
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account[_account] |= bytes32(newBalance & 0x00ffffffffffffffffffffffffffffffffffffffff);
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return true;
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}
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// Creates new tokens out of thin air, and allocates them to the given address
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// Triggers tax
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function mintTo(address _beneficiary, uint256 _amount) external returns (bool) {
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require(minter[msg.sender]);
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// TODO: get base amount for minting
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applyTax();
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totalSupply += _amount;
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increaseBaseBalance(_beneficiary, _amount);
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emit Mint(msg.sender, _beneficiary, _amount);
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saveRedistributionSupply();
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return true;
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}
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// Deserializes the redistribution word
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function toRedistribution(uint256 _participants, uint256 _value, uint256 _period) private pure returns(bytes32) {
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bytes32 redistribution;
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redistribution |= bytes32((_participants & 0x7fffffffff) << 216);
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redistribution |= bytes32((_value & 0xffffffffffffffffffffffff) << 56);
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redistribution |= bytes32(_period & 0xffffffffffffff);
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return redistribution;
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}
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// Serializes the demurrage period part of the redistribution word
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function toRedistributionPeriod(bytes32 redistribution) public pure returns (uint256) {
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return uint256(redistribution & 0x00000000000000000000000000000000000000000000000000ffffffffffffff);
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}
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// Serializes the supply part of the redistribution word
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function toRedistributionSupply(bytes32 redistribution) public pure returns (uint256) {
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return uint256(redistribution & 0x0000000000ffffffffffffffffffffffffffffffffffffffff00000000000000) >> 56;
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}
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// Serializes the number of participants part of the redistribution word
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function toRedistributionParticipants(bytes32 redistribution) public pure returns (uint256) {
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return uint256(redistribution & 0x7fffffffff000000000000000000000000000000000000000000000000000000) >> 216;
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}
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// Client accessor to the redistributions array length
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function redistributionCount() public view returns (uint256) {
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return redistributions.length;
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}
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// Add number of participants for the current redistribution period by one
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function incrementRedistributionParticipants() private returns (bool) {
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uint256 currentRedistribution;
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uint256 participants;
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currentRedistribution = uint256(redistributions[redistributions.length-1]);
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participants = ((currentRedistribution & 0x7fffffffff000000000000000000000000000000000000000000000000000000) >> 216) + 1;
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currentRedistribution &= 0x8000000000ffffffffffffffffffffffffffffffffffffffffffffffffffffff;
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currentRedistribution |= participants << 216;
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//emit Debug(participants);
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redistributions[redistributions.length-1] = bytes32(currentRedistribution);
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}
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// Save the current total supply amount to the current redistribution period
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function saveRedistributionSupply() private returns (bool) {
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uint256 currentRedistribution;
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currentRedistribution = uint256(redistributions[redistributions.length-1]);
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currentRedistribution &= 0xffffffffff0000000000000000000000000000000000000000ffffffffffffff;
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currentRedistribution |= totalSupply << 56;
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redistributions[redistributions.length-1] = bytes32(currentRedistribution);
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}
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// Get the demurrage period of the current block number
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function actualPeriod() public view returns (uint256) {
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return (block.number - periodStart) / periodDuration + 1;
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}
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// Add an entered demurrage period to the redistribution array
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function checkPeriod() private view returns (bytes32) {
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bytes32 lastRedistribution;
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uint256 currentPeriod;
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lastRedistribution = redistributions[redistributions.length-1];
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currentPeriod = this.actualPeriod();
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if (currentPeriod <= toRedistributionPeriod(lastRedistribution)) {
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return bytes32(0x00);
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}
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return lastRedistribution;
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}
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// Deserialize the pemurrage period for the given account is participating in
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function accountPeriod(address _account) public view returns (uint256) {
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return (uint256(account[_account]) & 0xffffffffffffffffffffffff0000000000000000000000000000000000000000) >> 160;
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}
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// Save the given demurrage period as the currently participation period for the given address
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function registerAccountPeriod(address _account, uint256 _period) private returns (bool) {
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account[_account] &= 0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff;
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account[_account] |= bytes32(_period << 160);
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incrementRedistributionParticipants();
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}
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// Determine whether the unit number is rounded down, rounded up or evenly divides.
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// Returns 0 if evenly distributed, or the remainder as a positive number
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// A _numParts value 0 will be interpreted as the value 1
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function remainder(uint256 _numParts, uint256 _sumWhole) public pure returns (uint256) {
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uint256 unit;
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uint256 truncatedResult;
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if (_numParts == 0) { // no division by zero please
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return _sumWhole;
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}
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require(_numParts < _sumWhole); // At least you are never LESS than the sum of your parts. Think about that.
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unit = _sumWhole / _numParts;
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truncatedResult = unit * _numParts;
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return _sumWhole - truncatedResult;
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}
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// sets the remainder bit for the given period and books the remainder to the sink address balance
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// returns false if no change was made
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function applyRemainderOnPeriod(uint256 _remainder, uint256 _period) private returns (bool) {
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bytes32 redistribution;
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redistribution = redistributions[_period-1];
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if (_remainder == 0) {
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return false;
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}
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redistribution |= 0x8000000000000000000000000000000000000000000000000000000000000000;
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increaseBaseBalance(sinkAddress, _remainder);
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return true;
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}
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// Recalculate the demurrage modifier for the new period
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// After this, all REPORTED balances will have been reduced by the corresponding ratio (but the effecive totalsupply stays the same)
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function applyTax() public returns (uint256) {
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bytes32 currentRedistribution;
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bytes32 nextRedistribution;
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uint256 currentPeriod;
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uint256 currentParticipants;
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uint256 currentRemainder;
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currentRedistribution = checkPeriod();
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if (currentRedistribution == bytes32(0x00)) {
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return demurrageModifier;
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}
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demurrageModifier -= (demurrageModifier * taxLevel) / 1000000;
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currentPeriod = toRedistributionPeriod(currentRedistribution);
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nextRedistribution = toRedistribution(0, totalSupply, currentPeriod + 1);
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redistributions.push(nextRedistribution);
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currentParticipants = toRedistributionParticipants(currentRedistribution);
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currentRemainder = remainder(currentParticipants, totalSupply); // we can use totalSupply directly because it will always be the same as the recorded supply on the current redistribution
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applyRemainderOnPeriod(currentRemainder, currentPeriod);
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emit Taxed(currentPeriod, currentRemainder);
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return demurrageModifier;
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}
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// Calculate a value reduced by demurrage by the given period
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function toTaxPeriodAmount(uint256 _value, uint256 _period) public view returns (uint256) {
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uint256 valueFactor;
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// TODO: doesn't work for solidity as floats are missing and using ints linearly increases the order of magnitude
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// valueFactor = 1000000 * (((1000000-taxLevel)/1000000) ** _period);
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valueFactor = 1000000;
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for (uint256 i = 0; i < _period; i++) {
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valueFactor = (valueFactor * taxLevel) / 1000000;
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}
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return (valueFactor * _value) / 1000000;
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}
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// If the given account is participating in a period and that period has been crossed
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// THEN increase the base value of the account with its share of the value reduction of the period
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function applyRedistributionOnAccount(address _account) public returns (bool) {
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bytes32 periodRedistribution;
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uint256 supply;
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uint256 participants;
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uint256 baseValue;
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uint256 value;
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uint256 period;
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period = accountPeriod(_account);
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if (period == 0 || period >= actualPeriod()) {
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return false;
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}
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periodRedistribution = redistributions[period-1];
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participants = toRedistributionParticipants(periodRedistribution);
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if (participants == 0) {
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return false;
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}
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supply = toRedistributionSupply(periodRedistribution);
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// TODO: Make sure value for balance increases round down, and that we can do a single allocation to a sink account with the difference. We can use the highest bit in "participants" for that.
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baseValue = supply / participants;
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value = toTaxPeriodAmount(baseValue, period-1);
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account[_account] &= bytes32(0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff);
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increaseBaseBalance(_account, value);
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emit Redistribution(_account, period, value);
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return true;
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}
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// Inflates the given amount according to the current demurrage modifier
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function toBaseAmount(uint256 _value) public view returns (uint256) {
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return (_value * 1000000) / demurrageModifier;
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}
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// ERC20, triggers tax and/or redistribution
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function transfer(address _to, uint256 _value) public returns (bool) {
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uint256 baseValue;
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bool result;
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applyTax();
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applyRedistributionOnAccount(msg.sender);
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// TODO: Prefer to truncate the result, instead it seems to round to nearest :/
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baseValue = toBaseAmount(_value);
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result = transferBase(msg.sender, _to, baseValue);
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return result;
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}
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// ERC20 transfer backend for transfer, transferFrom
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function transferBase(address _from, address _to, uint256 _value) private returns (bool) {
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uint256 period;
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if (!decreaseBaseBalance(_from, _value)) {
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revert('ERR_TX_DECREASEBALANCE');
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}
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if (!increaseBaseBalance(_to, _value)) {
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revert('ERR_TX_INCREASEBALANCE');
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}
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period = actualPeriod();
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if (_value > 0 && accountPeriod(_from) != period) {
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registerAccountPeriod(_from, period);
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}
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return true;
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}
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// ERC20, triggers tax and/or redistribution
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function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
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uint256 baseValue;
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bool result;
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applyTax();
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applyRedistributionOnAccount(msg.sender);
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baseValue = toBaseAmount(_value);
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require(allowance[_from][msg.sender] >= baseValue);
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result = transferBase(_from, _to, baseValue);
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return result;
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}
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// ERC20, triggers tax and/or redistribution
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function approve(address _spender, uint256 _value) public returns (bool) {
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uint256 baseValue;
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applyTax();
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applyRedistributionOnAccount(msg.sender);
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baseValue = toBaseAmount(_value);
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allowance[msg.sender][_spender] += baseValue;
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emit Approval(msg.sender, _spender, _value);
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return true;
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}
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}
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