// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.8.18;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "./tax/ITaxHandler.sol";
import "./treasury/ITreasuryHandler.sol";

contract MARU is IERC20, Ownable {
    /// @dev Registry of user token balances.
    mapping(address => uint256) private _balances;

    /// @dev Registry of addresses users have given allowances to.
    mapping(address => mapping(address => uint256)) private _allowances;

    /// @notice The contract implementing tax calculations.
    ITaxHandler public taxHandler;

    /// @notice The contract that performs treasury-related operations.
    ITreasuryHandler public treasuryHandler;

    /// @notice Emitted when the tax handler contract is changed.
    event TaxHandlerChanged(address oldAddress, address newAddress);

    /// @notice Emitted when the treasury handler contract is changed.
    event TreasuryHandlerChanged(address oldAddress, address newAddress);

    /// @dev Name of the token.
    string private _name;

    /// @dev Symbol of the token.
    string private _symbol;

    /**
     * @param name_ Name of the token.
     * @param symbol_ Symbol of the token.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;

        _balances[_msgSender()] = totalSupply();

        emit Transfer(address(0), _msgSender(), totalSupply());
    }

    /**
     * @notice Get token name.
     * @return Name of the token.
     */
    function name() public view returns (string memory) {
        return _name;
    }

    /**
     * @notice Get token symbol.
     * @return Symbol of the token.
     */
    function symbol() external view returns (string memory) {
        return _symbol;
    }

    /**
     * @notice Get number of decimals used by the token.
     * @return Number of decimals used by the token.
     */
    function decimals() external pure returns (uint8) {
        return 9;
    }

    /**
     * @notice Get the maximum number of tokens.
     * @return The maximum number of tokens that will ever be in existence.
     */
    function totalSupply() public pure override returns (uint256) {
        // six billion nine hundred sixty-nine million six hundred ninety-six thousand nine hundred sixty-nine, i.e., 6,969,696,969 tokens.
        return 6_969_696_969 * 1e9;
    }

    /**
     * @notice Get token balance of given given account.
     * @param account Address to retrieve balance for.
     * @return The number of tokens owned by `account`.
     */
    function balanceOf(address account)
        external
        view
        override
        returns (uint256)
    {
        return _balances[account];
    }

    /**
     * @notice Transfer tokens from caller's address to another.
     * @param recipient Address to send the caller's tokens to.
     * @param amount The number of tokens to transfer to recipient.
     * @return True if transfer succeeds, else an error is raised.
     */
    function transfer(address recipient, uint256 amount)
        external
        override
        returns (bool)
    {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @notice Get the allowance `owner` has given `spender`.
     * @param owner The address on behalf of whom tokens can be spent by `spender`.
     * @param spender The address authorized to spend tokens on behalf of `owner`.
     * @return The allowance `owner` has given `spender`.
     */
    function allowance(address owner, address spender)
        external
        view
        override
        returns (uint256)
    {
        return _allowances[owner][spender];
    }

    /**
     * @notice Approve address to spend caller's tokens.
     * @dev This method can be exploited by malicious spenders if their allowance is already non-zero. See the following
     * document for details: https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/edit.
     * Ensure the spender can be trusted before calling this method if they've already been approved before. Otherwise
     * use either the `increaseAllowance`/`decreaseAllowance` functions, or first set their allowance to zero, before
     * setting a new allowance.
     * @param spender Address to authorize for token expenditure.
     * @param amount The number of tokens `spender` is allowed to spend.
     * @return True if the approval succeeds, else an error is raised.
     */
    function approve(address spender, uint256 amount)
        external
        override
        returns (bool)
    {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @notice Transfer tokens from one address to another.
     * @param sender Address to move tokens from.
     * @param recipient Address to send the caller's tokens to.
     * @param amount The number of tokens to transfer to recipient.
     * @return True if the transfer succeeds, else an error is raised.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external override returns (bool) {
        _transfer(sender, recipient, amount);

        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(
            currentAllowance >= amount,
            "MARU:transferFrom:ALLOWANCE_EXCEEDED: Transfer amount exceeds allowance."
        );
        unchecked {
            _approve(sender, _msgSender(), currentAllowance - amount);
        }

        return true;
    }

    /**
     * @notice Increase spender's allowance.
     * @param spender Address of user authorized to spend caller's tokens.
     * @param addedValue The number of tokens to add to `spender`'s allowance.
     * @return True if the allowance is successfully increased, else an error is raised.
     */
    function increaseAllowance(address spender, uint256 addedValue)
        external
        returns (bool)
    {
        _approve(
            _msgSender(),
            spender,
            _allowances[_msgSender()][spender] + addedValue
        );

        return true;
    }

    /**
     * @notice Decrease spender's allowance.
     * @param spender Address of user authorized to spend caller's tokens.
     * @param subtractedValue The number of tokens to remove from `spender`'s allowance.
     * @return True if the allowance is successfully decreased, else an error is raised.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue)
        external
        returns (bool)
    {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(
            currentAllowance >= subtractedValue,
            "MARU:decreaseAllowance:ALLOWANCE_UNDERFLOW: Subtraction results in sub-zero allowance."
        );
        unchecked {
            _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @notice Set new tax handler contract.
     * @param taxHandlerAddress Address of new tax handler contract.
     */
    function setTaxHandler(address taxHandlerAddress) external onlyOwner {
        address oldTaxHandlerAddress = address(taxHandler);
        taxHandler = ITaxHandler(taxHandlerAddress);

        emit TaxHandlerChanged(oldTaxHandlerAddress, taxHandlerAddress);
    }

    /**
     * @notice Set new treasury handler contract.
     * @param treasuryHandlerAddress Address of new treasury handler contract.
     */
    function setTreasuryHandler(address treasuryHandlerAddress)
        external
        onlyOwner
    {
        address oldTreasuryHandlerAddress = address(treasuryHandler);
        treasuryHandler = ITreasuryHandler(treasuryHandlerAddress);

        emit TreasuryHandlerChanged(
            oldTreasuryHandlerAddress,
            treasuryHandlerAddress
        );
    }

    /**
     * @notice Approve spender on behalf of owner.
     * @param owner Address on behalf of whom tokens can be spent by `spender`.
     * @param spender Address to authorize for token expenditure.
     * @param amount The number of tokens `spender` is allowed to spend.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) private {
        require(
            owner != address(0),
            "MARU:_approve:OWNER_ZERO: Cannot approve for the zero address."
        );
        require(
            spender != address(0),
            "MARU:_approve:SPENDER_ZERO: Cannot approve to the zero address."
        );

        _allowances[owner][spender] = amount;

        emit Approval(owner, spender, amount);
    }

    /**
     * @notice Transfer `amount` tokens from account `from` to account `to`.
     * @param from Address the tokens are moved out of.
     * @param to Address the tokens are moved to.
     * @param amount The number of tokens to transfer.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) private {
        require(
            from != address(0),
            "MARU:_transfer:FROM_ZERO: Cannot transfer from the zero address."
        );
        require(
            to != address(0),
            "MARU:_transfer:TO_ZERO: Cannot transfer to the zero address."
        );
        require(
            amount > 0,
            "MARU:_transfer:ZERO_AMOUNT: Transfer amount must be greater than zero."
        );
        require(
            amount <= _balances[from],
            "MARU:_transfer:INSUFFICIENT_BALANCE: Transfer amount exceeds balance."
        );

        treasuryHandler.beforeTransferHandler(from, to, amount);

        uint256 tax = taxHandler.getTax(from, to, amount);
        uint256 taxedAmount = amount - tax;

        _balances[from] -= amount;
        _balances[to] += taxedAmount;

        if (tax > 0) {
            _balances[address(treasuryHandler)] += tax;

            emit Transfer(from, address(treasuryHandler), tax);
        }

        treasuryHandler.afterTransferHandler(from, to, amount);

        emit Transfer(from, to, taxedAmount);
    }
}
[{"inputs":[{"internalType":"string","name":"name_","type":"string"},{"internalType":"string","name":"symbol_","type":"string"}],"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"owner","type":"address"},{"indexed":true,"internalType":"address","name":"spender","type":"address"},{"indexed":false,"internalType":"uint256","name":"value","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"previousOwner","type":"address"},{"indexed":true,"internalType":"address","name":"newOwner","type":"address"}],"name":"OwnershipTransferred","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"oldAddress","type":"address"},{"indexed":false,"internalType":"address","name":"newAddress","type":"address"}],"name":"TaxHandlerChanged","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"from","type":"address"},{"indexed":true,"internalType":"address","name":"to","type":"address"},{"indexed":false,"internalType":"uint256","name":"value","type":"uint256"}],"name":"Transfer","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"oldAddress","type":"address"},{"indexed":false,"internalType":"address","name":"newAddress","type":"address"}],"name":"TreasuryHandlerChanged","type":"event"},{"inputs":[{"internalType":"address","name":"owner","type":"address"},{"internalType":"address","name":"spender","type":"address"}],"name":"allowance","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"approve","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"account","type":"address"}],"name":"balanceOf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"decimals","outputs":[{"internalType":"uint8","name":"","type":"uint8"}],"stateMutability":"pure","type":"function"},{"inputs":[{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"subtractedValue","type":"uint256"}],"name":"decreaseAllowance","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"addedValue","type":"uint256"}],"name":"increaseAllowance","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"owner","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"renounceOwnership","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"taxHandlerAddress","type":"address"}],"name":"setTaxHandler","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"treasuryHandlerAddress","type":"address"}],"name":"setTreasuryHandler","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"taxHandler","outputs":[{"internalType":"contract ITaxHandler","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"pure","type":"function"},{"inputs":[{"internalType":"address","name":"recipient","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transfer","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"sender","type":"address"},{"internalType":"address","name":"recipient","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transferFrom","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"newOwner","type":"address"}],"name":"transferOwnership","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"treasuryHandler","outputs":[{"internalType":"contract ITreasuryHandler","name":"","type":"address"}],"stateMutability":"view","type":"function"}]