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"content": "//SPDX-License-Identifier: MIT\n\npragma solidity 0.8.19;\n\n/// @title IERC20 Token Standard\n/// @notice Interface for the ERC20 standard token contract\ninterface IERC20 {\n event Transfer(address indexed from, address indexed to, uint256 value);\n\n event Approval(\n address indexed owner,\n address indexed spender,\n uint256 value\n );\n\n function totalSupply() external view returns (uint256);\n\n function balanceOf(address account) external view returns (uint256);\n\n function transfer(address to, uint256 amount) external returns (bool);\n\n function allowance(address owner, address spender)\n external\n view\n returns (uint256);\n\n function approve(address spender, uint256 amount) external returns (bool);\n\n function transferFrom(\n address from,\n address to,\n uint256 amount\n ) external returns (bool);\n}\n\n/// @title Interface for UniswapV2Factory Contract\n/// @notice It is used to create new instances of pairs\ninterface IUniswapV2Factory {\n function createPair(address tokenA, address tokenB)\n external\n returns (address pair);\n}\n\n/// @title Interface for UniswapV2Router02 Contract\n/// @notice It is used to get information about liquidity reserves\ninterface IUniswapV2Router {\n function factory() external pure returns (address);\n\n function WETH() external pure returns (address);\n}\n\n/// @author Kenji Sato\n/// @title Hakkaido Token Contract\n/// @notice Hokkaido token is a utility token created for use on the Hokkaido platform,\n/// acting as an intermediary between the user's token and Uniswap pool.\n/// It implements the IERC20 token standard.\n/// @custom:website https://www.hokkaido.ai\n/// @custom:telegram https://t.me/hokk_token\n/// @custom:twitter https://twitter.com/hokk_token\ncontract Hokkaido is IERC20 {\n // Address of the owner of the contract\n address public owner;\n\n // Total supply of the token\n uint256 public totalSupply;\n\n // Mapping of account addresses to their respective balances\n mapping(address => uint256) public balances;\n // Mapping of holder addresses to a mapping of spender addresses to their respective allowances\n mapping(address => mapping(address => uint256)) public allowances;\n\n // The timestamp when the time lock for purchasing tokens ends\n // This is an anti-sniping bot measure to prevent purchases from the Uniswap during the specified time frame\n uint256 public purchaseTimeLockEnd;\n\n // The maximum number of tokens that a wallet can hold\n // This is a measure to prevent price manipulation\n // The maxWallet restriction will be removed after 24 hours from allowing trading\n uint256 public maxWallet;\n\n // The timestamp indicating the end time of the period during\n // which a maximum wallet size is enforced\n uint256 public maxWalletEndTime;\n\n // The Uniswap V2 router contract\n IUniswapV2Router public uniswapV2Router;\n // The address of the Uniswap V2 liquidity pool for the token\n address public uniswapV2Pair;\n\n // Constants for token name, symbol and decimals\n string private constant NAME = \"Hokkaido\";\n string private constant SYMBOL = \"HOKK\";\n uint8 private constant DECIMALS = 18;\n\n // Event for transferring ownership of the contract\n event OwnershipTransferred(\n address indexed previousOwner,\n address indexed newOwner\n );\n\n // Modifier to only allow the contract owner to execute a function\n modifier onlyOwner() {\n require(msg.sender == owner, \"Error: Caller is not the contract owner\");\n _;\n }\n\n // Contract constructor\n constructor(uint256 amount, uint256 timelock) {\n // Create a new instance of IUniswapV2Router\n IUniswapV2Router _uniswapV2Router = IUniswapV2Router(\n 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D\n );\n // Assign the new instance to the uniswapV2Router variable\n uniswapV2Router = _uniswapV2Router;\n // Create a new Uniswap pair for this new token\n uniswapV2Pair = IUniswapV2Factory(_uniswapV2Router.factory())\n .createPair(address(this), _uniswapV2Router.WETH());\n // Assign the time lock for purchasing tokens\n purchaseTimeLockEnd = timelock;\n\n // Assign the end time of the period during which a maximum wallet size is enforced\n maxWalletEndTime = purchaseTimeLockEnd + 24 hours;\n\n // Assign the totalSupply to the given amount\n totalSupply = amount;\n // Assign the maxWallet to 2% of the totalSupply\n maxWallet = (totalSupply * 2) / 100;\n // Assign the full amount to the balance of the contract creator\n balances[msg.sender] = totalSupply;\n\n // Emit a Transfer event from address 0 to the contract creator with the totalSupply as the value\n emit Transfer(address(0), msg.sender, totalSupply);\n // Set the owner to the contract creator\n owner = msg.sender;\n }\n\n /**\n * @dev Returns the balance of the specified address.\n * @param account The address to retrieve the balance of.\n * @return The balance of the specified address.\n */\n function balanceOf(address account)\n external\n view\n override\n returns (uint256)\n {\n return balances[account];\n }\n\n /**\n * @dev Returns the allowance of a spender for a given holder.\n * @param holder The address of the holder.\n * @param spender The address of the spender.\n * @return The allowance of the spender for the given holder.\n */\n function allowance(address holder, address spender)\n external\n view\n override\n returns (uint256)\n {\n return allowances[holder][spender];\n }\n\n /**\n * @dev Returns the name of the token.\n * @return string memory The name of the token.\n */\n function name() external pure returns (string memory) {\n return NAME;\n }\n\n /**\n * @dev Returns the symbol of the token.\n * @return string memory The symbol of the token.\n */\n function symbol() external pure returns (string memory) {\n return SYMBOL;\n }\n\n /**\n * @dev Returns the number of decimal places used to represent the token amount.\n * @return uint8 The number of decimal places used to represent the token amount.\n */\n function decimals() external pure returns (uint8) {\n return DECIMALS;\n }\n\n /**\n * @dev Approves the given spender to transfer the specified amount from the msg.sender's account.\n * @param spender The address of the spender to approve.\n * @param amount The amount of token to be approved for transfer.\n * @return bool True if the approval was successful.\n */\n function approve(address spender, uint256 amount)\n external\n virtual\n override\n returns (bool)\n {\n allowances[msg.sender][spender] = amount;\n emit Approval(msg.sender, spender, amount);\n return true;\n }\n\n /**\n * @dev Renounces ownership of the contract.\n */\n function renounceOwnership() external virtual onlyOwner {\n _transferOwnership(address(0));\n }\n\n /**\n * @dev Transfers the specified amount of tokens from the sender to the recipient on behalf of the sender.\n * @param sender The address of the token holder to transfer from.\n * @param recipient The address of the recipient to transfer to.\n * @param amount The amount of token to be transferred.\n * @return bool True if the transfer was successful.\n */\n function transferFrom(\n address sender,\n address recipient,\n uint256 amount\n ) external override returns (bool) {\n // Check if the allowance is sufficient\n require(\n allowances[sender][msg.sender] >= amount,\n \"Error: insufficient allowance.\"\n );\n\n // Decrease the allowance\n allowances[sender][msg.sender] -= amount;\n\n return _transfer(sender, recipient, amount);\n }\n\n /**\n * @dev Transfers the specified amount of tokens from the msg.sender's account to the recipient.\n * @param recipient The address of the recipient to transfer to.\n * @param amount The amount of token to be transferred.\n * @return bool True if the transfer was successful.\n */\n function transfer(address recipient, uint256 amount)\n external\n override\n returns (bool)\n {\n return _transfer(msg.sender, recipient, amount);\n }\n\n /**\n * @dev Transfers the ownership of the contract to the new owner.\n * @param newOwner The address of the new owner.\n */\n function _transferOwnership(address newOwner) internal virtual {\n address oldOwner = owner;\n owner = newOwner;\n emit OwnershipTransferred(oldOwner, newOwner);\n }\n\n /**\n * @dev Transfers `amount` tokens from `sender` to `recipient`.\n *\n * @param sender The address of the sender.\n * @param recipient The address of the recipient.\n * @param amount The amount of tokens to transfer.\n *\n * @return A boolean indicating whether the transfer was successful.\n */\n function _transfer(\n address sender,\n address recipient,\n uint256 amount\n ) internal virtual returns (bool) {\n // Ensure that the `sender` and `recipient` addresses are not the zero address\n require(\n sender != address(0) && recipient != address(0),\n \"Error: Transfer from/to the zero address is not allowed.\"\n );\n\n // Check the balance of the `sender` to make sure the transfer amount is valid\n uint256 senderBalance = balances[sender];\n require(\n senderBalance >= amount,\n \"Error: Transfer amount exceeds the sender's balance.\"\n );\n\n // Prevent purchases from the Uniswap during a specified time lock period\n // which serves as an anti-sniping bot measure.\n if (sender == uniswapV2Pair && block.timestamp < purchaseTimeLockEnd) {\n revert(\n \"Error: Purchase from Uniswap DEX not allowed during timelock period.\"\n );\n }\n\n // Check whether the maxWallet restriction is in effect\n // and the recipient is not the UniswapV2 pair since we need to add liquidity\n if (block.timestamp < maxWalletEndTime && recipient != uniswapV2Pair) {\n // Check whether the sum of the recipient's current balance\n // and the transferred amount exceeds the maxWallet limit\n require(\n balances[recipient] + amount <= maxWallet,\n \"Error: Recipient balance exceeds maximum wallet size.\"\n );\n } else if (\n block.timestamp >= maxWalletEndTime && maxWalletEndTime != 0\n ) {\n // Remove the maxWallet restriction after the specified time lock period\n maxWallet = totalSupply;\n maxWalletEndTime = 0;\n }\n\n // Perform the transfer\n balances[sender] -= amount;\n balances[recipient] += amount;\n\n // Emit the Transfer event\n emit Transfer(sender, recipient, amount);\n\n // Return true to indicate the transfer was successful\n return true;\n }\n}\n"
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