// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "./Authorizable.sol";

// The GovernanceToken
contract GovernanceToken is ERC20, Ownable, Authorizable {    
    uint256 private _cap;
    uint256 private _totalLock;
    uint256 public lockFromBlock;
    uint256 public lockToBlock;
    uint256 public manualMintLimit;
    uint256 public manualMinted = 0;

    mapping(address => uint256) private _locks;
    mapping(address => uint256) private _lastUnlockBlock;

    event Lock(address indexed to, uint256 value);

    constructor(
      string memory _name,
      string memory _symbol,
      uint256 cap_,
      uint256 _manualMintLimit,
      uint256 _lockFromBlock,
      uint256 _lockToBlock
    ) public ERC20(_name, _symbol) {
        _cap = cap_;
        manualMintLimit = _manualMintLimit;
        lockFromBlock = _lockFromBlock;
        lockToBlock = _lockToBlock;
    }

    /**
     * @dev Returns the cap on the token's total supply.
     */
    function cap() public view returns (uint256) {
        return _cap;
    }

    // Update the total cap - can go up or down but wont destroy previous tokens.
    function capUpdate(uint256 _newCap) public onlyAuthorized {
        _cap = _newCap;
    }

    // Update the lockFromBlock
    function lockFromUpdate(uint256 _newLockFrom) public onlyAuthorized {
        lockFromBlock = _newLockFrom;
    }

    // Update the lockToBlock
    function lockToUpdate(uint256 _newLockTo) public onlyAuthorized {
        lockToBlock = _newLockTo;
    }

    function unlockedSupply() public view returns (uint256) {
        return totalSupply().sub(_totalLock);
    }

    function lockedSupply() public view returns (uint256) {
        return totalLock();
    }

    function circulatingSupply() public view returns (uint256) {
        return totalSupply();
    }

    function totalLock() public view returns (uint256) {
        return _totalLock;
    }

    /**
     * @dev See {ERC20-_beforeTokenTransfer}.
     *
     * Requirements:
     *
     * - minted tokens must not cause the total supply to go over the cap.
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual override {
        super._beforeTokenTransfer(from, to, amount);

        if (from == address(0)) {
            // When minting tokens
            require(
                totalSupply().add(amount) <= _cap,
                "ERC20Capped: cap exceeded"
            );
        }
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is 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 override {
        super._transfer(sender, recipient, amount);
        _moveDelegates(_delegates[sender], _delegates[recipient], amount);
    }

    /// @notice Creates `_amount` token to `_to`. Must only be called by the owner (MasterSupplier).
    function mint(address _to, uint256 _amount) public onlyOwner {
        _mint(_to, _amount);
        _moveDelegates(address(0), _delegates[_to], _amount);
    }

    function manualMint(address _to, uint256 _amount) public onlyAuthorized {
        require(manualMinted < manualMintLimit, "ERC20: manualMinted greater than manualMintLimit");
        _mint(_to, _amount);
        _moveDelegates(address(0), _delegates[_to], _amount);
        manualMinted = manualMinted.add(_amount);
    }

    function totalBalanceOf(address _holder) public view returns (uint256) {
        return _locks[_holder].add(balanceOf(_holder));
    }

    function lockOf(address _holder) public view returns (uint256) {
        return _locks[_holder];
    }

    function lastUnlockBlock(address _holder) public view returns (uint256) {
        return _lastUnlockBlock[_holder];
    }

    function lock(address _holder, uint256 _amount) public onlyOwner {
        require(_holder != address(0), "ERC20: lock to the zero address");
        require(
            _amount <= balanceOf(_holder),
            "ERC20: lock amount over balance"
        );

        _transfer(_holder, address(this), _amount);

        _locks[_holder] = _locks[_holder].add(_amount);
        _totalLock = _totalLock.add(_amount);
        if (_lastUnlockBlock[_holder] < lockFromBlock) {
            _lastUnlockBlock[_holder] = lockFromBlock;
        }
        emit Lock(_holder, _amount);
    }

    function canUnlockAmount(address _holder) public view returns (uint256) {
        if (block.number < lockFromBlock) {
            return 0;
        } else if (block.number >= lockToBlock) {
            return _locks[_holder];
        } else {
            uint256 releaseBlock = block.number.sub(_lastUnlockBlock[_holder]);
            uint256 numberLockBlock =
                lockToBlock.sub(_lastUnlockBlock[_holder]);
            return _locks[_holder].mul(releaseBlock).div(numberLockBlock);
        }
    }

    function unlock() public {
        require(_locks[msg.sender] > 0, "ERC20: cannot unlock");

        uint256 amount = canUnlockAmount(msg.sender);
        // just for sure
        if (amount > balanceOf(address(this))) {
            amount = balanceOf(address(this));
        }
        _transfer(address(this), msg.sender, amount);
        _locks[msg.sender] = _locks[msg.sender].sub(amount);
        _lastUnlockBlock[msg.sender] = block.number;
        _totalLock = _totalLock.sub(amount);
    }

    // This function is for dev address migrate all balance to a multi sig address
    function transferAll(address _to) public {
        _locks[_to] = _locks[_to].add(_locks[msg.sender]);

        if (_lastUnlockBlock[_to] < lockFromBlock) {
            _lastUnlockBlock[_to] = lockFromBlock;
        }

        if (_lastUnlockBlock[_to] < _lastUnlockBlock[msg.sender]) {
            _lastUnlockBlock[_to] = _lastUnlockBlock[msg.sender];
        }

        _locks[msg.sender] = 0;
        _lastUnlockBlock[msg.sender] = 0;

        _transfer(msg.sender, _to, balanceOf(msg.sender));
    }

    // Copied and modified from YAM code:
    // https://github.com/yam-finance/yam-protocol/blob/master/contracts/token/YAMGovernanceStorage.sol
    // https://github.com/yam-finance/yam-protocol/blob/master/contracts/token/YAMGovernance.sol
    // Which is copied and modified from COMPOUND:
    // https://github.com/compound-finance/compound-protocol/blob/master/contracts/Governance/Comp.sol

    /// @dev A record of each accounts delegate
    mapping(address => address) internal _delegates;

    /// @notice A checkpoint for marking number of votes from a given block
    struct Checkpoint {
        uint32 fromBlock;
        uint256 votes;
    }

    /// @notice A record of votes checkpoints for each account, by index
    mapping(address => mapping(uint32 => Checkpoint)) public checkpoints;

    /// @notice The number of checkpoints for each account
    mapping(address => uint32) public numCheckpoints;

    /// @notice The EIP-712 typehash for the contract's domain
    bytes32 public constant DOMAIN_TYPEHASH =
        keccak256(
            "EIP712Domain(string name,uint256 chainId,address verifyingContract)"
        );

    /// @notice The EIP-712 typehash for the delegation struct used by the contract
    bytes32 public constant DELEGATION_TYPEHASH =
        keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");

    /// @notice A record of states for signing / validating signatures
    mapping(address => uint256) public nonces;

    /// @notice An event thats emitted when an account changes its delegate
    event DelegateChanged(
        address indexed delegator,
        address indexed fromDelegate,
        address indexed toDelegate
    );

    /// @notice An event thats emitted when a delegate account's vote balance changes
    event DelegateVotesChanged(
        address indexed delegate,
        uint256 previousBalance,
        uint256 newBalance
    );

    /**
     * @notice Delegate votes from `msg.sender` to `delegatee`
     * @param delegator The address to get delegatee for
     */
    function delegates(address delegator) external view returns (address) {
        return _delegates[delegator];
    }

    /**
     * @notice Delegate votes from `msg.sender` to `delegatee`
     * @param delegatee The address to delegate votes to
     */
    function delegate(address delegatee) external {
        return _delegate(msg.sender, delegatee);
    }

    /**
     * @notice Delegates votes from signatory to `delegatee`
     * @param delegatee The address to delegate votes to
     * @param nonce The contract state required to match the signature
     * @param expiry The time at which to expire the signature
     * @param v The recovery byte of the signature
     * @param r Half of the ECDSA signature pair
     * @param s Half of the ECDSA signature pair
     */
    function delegateBySig(
        address delegatee,
        uint256 nonce,
        uint256 expiry,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external {
        bytes32 domainSeparator =
            keccak256(
                abi.encode(
                    DOMAIN_TYPEHASH,
                    keccak256(bytes(name())),
                    getChainId(),
                    address(this)
                )
            );

        bytes32 structHash =
            keccak256(
                abi.encode(DELEGATION_TYPEHASH, delegatee, nonce, expiry)
            );

        bytes32 digest =
            keccak256(
                abi.encodePacked("\x19\x01", domainSeparator, structHash)
            );

        address signatory = ecrecover(digest, v, r, s);
        require(
            signatory != address(0),
            "GovernanceToken::delegateBySig: invalid signature"
        );
        require(
            nonce == nonces[signatory]++,
            "GovernanceToken::delegateBySig: invalid nonce"
        );
        require(now <= expiry, "GovernanceToken::delegateBySig: signature expired");
        return _delegate(signatory, delegatee);
    }

    /**
     * @notice Gets the current votes balance for `account`
     * @param account The address to get votes balance
     * @return The number of current votes for `account`
     */
    function getCurrentVotes(address account) external view returns (uint256) {
        uint32 nCheckpoints = numCheckpoints[account];
        return
            nCheckpoints > 0 ? checkpoints[account][nCheckpoints - 1].votes : 0;
    }

    /**
     * @notice Determine the prior number of votes for an account as of a block number
     * @dev Block number must be a finalized block or else this function will revert to prevent misinformation.
     * @param account The address of the account to check
     * @param blockNumber The block number to get the vote balance at
     * @return The number of votes the account had as of the given block
     */
    function getPriorVotes(address account, uint256 blockNumber)
        external
        view
        returns (uint256)
    {
        require(
            blockNumber < block.number,
            "GovernanceToken::getPriorVotes: not yet determined"
        );

        uint32 nCheckpoints = numCheckpoints[account];
        if (nCheckpoints == 0) {
            return 0;
        }

        // First check most recent balance
        if (checkpoints[account][nCheckpoints - 1].fromBlock <= blockNumber) {
            return checkpoints[account][nCheckpoints - 1].votes;
        }

        // Next check implicit zero balance
        if (checkpoints[account][0].fromBlock > blockNumber) {
            return 0;
        }

        uint32 lower = 0;
        uint32 upper = nCheckpoints - 1;
        while (upper > lower) {
            uint32 center = upper - (upper - lower) / 2; // ceil, avoiding overflow
            Checkpoint memory cp = checkpoints[account][center];
            if (cp.fromBlock == blockNumber) {
                return cp.votes;
            } else if (cp.fromBlock < blockNumber) {
                lower = center;
            } else {
                upper = center - 1;
            }
        }
        return checkpoints[account][lower].votes;
    }

    function _delegate(address delegator, address delegatee) internal {
        address currentDelegate = _delegates[delegator];
        uint256 delegatorBalance = balanceOf(delegator);
        _delegates[delegator] = delegatee;

        emit DelegateChanged(delegator, currentDelegate, delegatee);

        _moveDelegates(currentDelegate, delegatee, delegatorBalance);
    }

    function _moveDelegates(
        address srcRep,
        address dstRep,
        uint256 amount
    ) internal {
        if (srcRep != dstRep && amount > 0) {
            if (srcRep != address(0)) {
                // decrease old representative
                uint32 srcRepNum = numCheckpoints[srcRep];
                uint256 srcRepOld =
                    srcRepNum > 0
                        ? checkpoints[srcRep][srcRepNum - 1].votes
                        : 0;
                uint256 srcRepNew = srcRepOld.sub(amount);
                _writeCheckpoint(srcRep, srcRepNum, srcRepOld, srcRepNew);
            }

            if (dstRep != address(0)) {
                // increase new representative
                uint32 dstRepNum = numCheckpoints[dstRep];
                uint256 dstRepOld =
                    dstRepNum > 0
                        ? checkpoints[dstRep][dstRepNum - 1].votes
                        : 0;
                uint256 dstRepNew = dstRepOld.add(amount);
                _writeCheckpoint(dstRep, dstRepNum, dstRepOld, dstRepNew);
            }
        }
    }

    function _writeCheckpoint(
        address delegatee,
        uint32 nCheckpoints,
        uint256 oldVotes,
        uint256 newVotes
    ) internal {
        uint32 blockNumber =
            safe32(
                block.number,
                "GovernanceToken::_writeCheckpoint: block number exceeds 32 bits"
            );

        if (
            nCheckpoints > 0 &&
            checkpoints[delegatee][nCheckpoints - 1].fromBlock == blockNumber
        ) {
            checkpoints[delegatee][nCheckpoints - 1].votes = newVotes;
        } else {
            checkpoints[delegatee][nCheckpoints] = Checkpoint(
                blockNumber,
                newVotes
            );
            numCheckpoints[delegatee] = nCheckpoints + 1;
        }

        emit DelegateVotesChanged(delegatee, oldVotes, newVotes);
    }

    function safe32(uint256 n, string memory errorMessage)
        internal
        pure
        returns (uint32)
    {
        require(n < 2**32, errorMessage);
        return uint32(n);
    }

    function getChainId() internal pure returns (uint256) {
        uint256 chainId;
        assembly {
            chainId := chainid()
        }
        return chainId;
    }
}
