// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor(address initialOwner) {
        _transferOwnership(initialOwner);
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}
/**
 * @dev Contract module which provides access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership} and {acceptOwnership}.
 *
 * This module is used through inheritance. It will make available all functions
 * from parent (Ownable).
 */
abstract contract Ownable2Step is Ownable {
    address private _pendingOwner;

    event OwnershipTransferStarted(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Returns the address of the pending owner.
     */
    function pendingOwner() public view virtual returns (address) {
        return _pendingOwner;
    }

    /**
     * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual override onlyOwner {
        _pendingOwner = newOwner;
        emit OwnershipTransferStarted(owner(), newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual override {
        delete _pendingOwner;
        super._transferOwnership(newOwner);
    }

    /**
     * @dev The new owner accepts the ownership transfer.
     */
    function acceptOwnership() public virtual {
        address sender = _msgSender();
        require(pendingOwner() == sender, "Ownable2Step: caller is not the new owner");
        _transferOwnership(sender);
    }
}
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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 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 `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, 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 `from` to `to` 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 from, address to, uint256 amount) external returns (bool);
}
/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * The default value of {decimals} is 18. To change this, you should override
 * this function so it returns a different value.
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the default value returned by this function, unless
     * it's overridden.
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(address from, address to, uint256 amount) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, allowance(owner, spender) + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        address owner = _msgSender();
        uint256 currentAllowance = allowance(owner, spender);
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `from` to `to`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * NOTE: This function is not virtual, {_update} should be overridden instead.
     */
    function _transfer(address from, address to, uint256 amount) internal {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");
        _update(from, to, amount);
    }

    /**
     * @dev Transfers `amount` of tokens from `from` to `to`, or alternatively mints (or burns) if `from` (or `to`) is
     * the zero address. All customizations to transfers, mints, and burns should be done by overriding this function.
     *
     * Emits a {Transfer} event.
     */
    function _update(address from, address to, uint256 amount) internal virtual {
        if (from == address(0)) {
            _totalSupply += amount;
        } else {
            uint256 fromBalance = _balances[from];
            require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
            unchecked {
                // Overflow not possible: amount <= fromBalance <= totalSupply.
                _balances[from] = fromBalance - amount;
            }
        }

        if (to == address(0)) {
            unchecked {
                // Overflow not possible: amount <= totalSupply or amount <= fromBalance <= totalSupply.
                _totalSupply -= amount;
            }
        } else {
            unchecked {
                // Overflow not possible: balance + amount is at most totalSupply, which we know fits into a uint256.
                _balances[to] += amount;
            }
        }

        emit Transfer(from, to, amount);
    }

    /**
     * @dev Creates `amount` tokens and assigns them to `account`, by transferring it from address(0).
     * Relies on the `_update` mechanism
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * NOTE: This function is not virtual, {_update} should be overridden instead.
     */
    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");
        _update(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, by transferring it to address(0).
     * Relies on the `_update` mechanism.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * NOTE: This function is not virtual, {_update} should be overridden instead
     */
    function _burn(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: burn from the zero address");
        _update(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(address owner, address spender, uint256 amount) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }
}

/// @title WLD token
/// @notice Contract for Worldcoin's ERC20 WLD token.
/// 
/// It updates from the previous token contract, which is now deprecated. At
/// deployment all existing balances are reinstated.
/// 
/// After deployment, the owner can do a one-time mint of new tokens up to the
/// `INITIAL_SUPPLY_CAP` of 10 billion.
/// 
/// After `inflationUnlockTime` the owner can set the minter address, which can
/// mint new tokens up to the inflation cap. The inflation cap is fixed
/// percentage per period. From this it follows a maximum inflation rate per
/// year. Whether or not to allow inflation can be goverened by the owner through
/// the minter address.
///
/// @author Worldcoin
contract WLD is ERC20, Ownable2Step {
    /////////////////////////////////////////////////////////////////////////
    ///                           PARAMETERS                              ///
    /////////////////////////////////////////////////////////////////////////

    uint256 constant public INITIAL_SUPPLY_CAP = 10_000_000_000 * (10**18);
    uint256 constant public WAD_ONE = 10**18;

    /// @notice Has the initial mint been done?
    bool public initialMintDone;

    /// @notice The address of the inflation minter
    address public minter;

    /// @notice Inflation parameters, formula in _mint @dev description
    uint256 immutable public inflationUnlockTime;
    uint256 immutable public inflationCapPeriod;
    uint256 immutable public inflationCapWad;

    /// @notice Inflation cap state variables
    uint256 public currentPeriodEnd;
    uint256 public currentPeriodSupplyCap;

    /////////////////////////////////////////////////////////////////////////
    ///                             EVENTS                                ///
    /////////////////////////////////////////////////////////////////////////

    /// @notice Emitted when constructing the contract
    event TokenUpdated(
        address newToken,
        string name,
        string symbol,
        address[] existingHolders,
        uint256[] existingsAmounts,
        uint256 inflationCapPeriod,
        uint256 inflationCapWad,
        uint256 inflationLockPeriod
    );

    /// @notice Emitted when minting tokens. Can be emited only once.
    event TokensMinted(
        address minter,
        address[] newHolders,
        uint256[] newAmounts
    );

    /// @notice Emitted when inflation tokens are minted, after the initial mint.
    event InflationTokensMinted(
        address minter,
        address to,
        uint256 amount
    );

    /////////////////////////////////////////////////////////////////////////
    ///                           CONSTRUCTOR                             ///
    /////////////////////////////////////////////////////////////////////////

    /// @notice Deploy a new token contract that replaces an existing one.
    constructor(
        address[] memory existingHolders,
        uint256[] memory existingAmounts,
        string memory name_,
        string memory symbol_,
        uint256 inflationCapPeriod_,
        uint256 inflationCapWad_,
        uint256 inflationLockPeriod_
    ) ERC20(name_, symbol_) Ownable(msg.sender) {
        // Validate input.
        require(existingAmounts.length == existingHolders.length);
        require(inflationCapPeriod_ != 0);

        // Allow one initial mint
        initialMintDone = false;

        // Set the inflation cap parameters
        minter = address(0);
        inflationCapPeriod = inflationCapPeriod_;
        inflationCapWad = inflationCapWad_;
        inflationUnlockTime = inflationLockPeriod_ + block.timestamp;

        // Make sure a new inflation period starts on first call to mint.
        currentPeriodEnd = 0;
        currentPeriodSupplyCap = 0;

        // Reinstate balances
        for (uint256 i = 0; i < existingHolders.length; i++) {
            _update(address(0), existingHolders[i], existingAmounts[i]);
        }

        // Make sure the initial supply cap is maintained.
        require(totalSupply() <= INITIAL_SUPPLY_CAP);

        // Emit event.
        emit TokenUpdated(
            address(this),
            name_,
            symbol_,
            existingHolders,
            existingAmounts,
            inflationCapPeriod_,
            inflationCapWad_,
            inflationLockPeriod_
        );
    }

    /////////////////////////////////////////////////////////////////////////
    ///                           OWNER ACTIONS                           ///
    /////////////////////////////////////////////////////////////////////////

    /// @notice Mint new tokens.
    function mintOnce(
        address[] memory newHolders,
        uint256[] memory newAmounts
    ) external onlyOwner {
        // This must be the only time we allow this.
        require(initialMintDone == false);

        // Validate input.
        require(newHolders.length == newAmounts.length);

        // Mark initial mint as done.
        initialMintDone = true;

        // Mint tokens.
        for (uint256 i = 0; i < newHolders.length; i++) {
            _mint(newHolders[i], newAmounts[i]);
        }

        // Make sure the initial supply cap is maintained.
        require(totalSupply() <= INITIAL_SUPPLY_CAP);

        emit TokensMinted(
            msg.sender,
            newHolders,
            newAmounts
        );
    }

    /// @notice Updates minter
    /// @dev onlyOwner
    /// @param minter_ new Minter address
    function setMinter(address minter_) external onlyOwner {
        minter = minter_;
    }

    /// @notice Prevents the owner from renouncing ownership
    /// @dev onlyOwner
    function renounceOwnership() public view override onlyOwner {
        revert();
    }

    ///////////////////////////////////////////////////////////////////
    ///                        MINTER ACTIONS                       ///
    ///////////////////////////////////////////////////////////////////

    /// @notice Mints new tokens and assigns them to the target address.
    /// @dev This function performs inflation checks. Their semantics is as follows:
    ///     * It is impossible to mint any tokens during the first `inflationLockPeriod_` seconds.
    //        The end of the lock period is stored in `inflationUnlockTime`.
    ///     * T inflation cap is in effect.
    ///       The inflation cap is enforced as follows:
    ///       1. If the current time is after the end of the current inflation period,
    ///          it is possible to raise the supply up to (current total supply) * (1 + inflation cap)
    ///          between now and (now + inflation period length), without any additional constraints;
    ///       2. If the current time is before the end of the current inflation period,
    ///          that period's supply is still controlled.
    /// NB: The logic outlined here means that it is possible for period over period inflation
    ///     to reach up to (1 + inflation cap)^2 - 1, for some choices of period boundaries.
    ///     The actual guarantees of this system are:
    ///     1. For any timestamp t0 and a natural number k, inflation measured between t0 and
    ///        t0 + k * inflation period does not exceed (1 + inflation cap)^(k + 1) - 1. In other words,
    ///        there is at most "one too many" inflation periods over any period of time.
    ///     2. For any timestamp t there exists a period tc < inflation period,
    ///        such that inflation measured between (t + tc) and (t + tc + inflation period)
    ///        does not exceed the inflation cap. In other words, period over period inflation is
    ///        bounded by the inflation cap at least for some amount of time during each period.
    function mintInflation(address to, uint256 amount) external {
        // Validate input
        require(to != address(0));
        require(amount != 0);

        // Must be minter
        require(msg.sender == minter);

        // Requires that the current time is after the mint lock-in period
        require(block.timestamp >= inflationUnlockTime);

        // Stars a new inflation period if the previous one ended
        if (block.timestamp > currentPeriodEnd) {
            // Update inflation period end
            currentPeriodEnd = block.timestamp + inflationCapPeriod;

            // Compute maximum supply for this period
            uint256 initialSupply = totalSupply();
            uint256 mintable = (initialSupply * inflationCapWad) / WAD_ONE;
            currentPeriodSupplyCap = initialSupply + mintable;
        }

        // Mint inflation tokens
        _mint(to, amount);

        // Check amount against inflation cap for this period
        require(totalSupply() <= currentPeriodSupplyCap);

        // Emit event
        emit InflationTokensMinted(msg.sender, to, amount);
    }
}