// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity 0.6.12;

// Interface declarations

/* solhint-disable func-order */

interface IERC20 {
    // 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, uint value);

    // 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, uint value);

    // Returns the amount of tokens in existence
    function totalSupply() external view returns (uint);

    // Returns the amount of tokens owned by account
    function balanceOf(address account) external view returns (uint);

    // 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 (uint);

    // Sets amount as the allowance of spender over the caller’s tokens
    // Returns a boolean value indicating whether the operation succeeded
    // Emits an Approval event.
    function approve(address spender, uint amount) external returns (bool);

    // Moves amount tokens from the caller’s account to recipient
    // Returns a boolean value indicating whether the operation succeeded
    // Emits a Transfer event.
    function transfer(address recipient, uint amount) external returns (bool);

    // Moves amount tokens from sender to recipient 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 sender, address recipient, uint amount) external returns (bool);
}