Remix error The transaction has been reverted to the initial state - cryptography

Question

I am testing my smart contract on remix. While testing Start Airdrop function is running successfully but as I approach getAirrop function I receive error :
transact to getAirdrop errored: VM error: revert. revert The transaction has been reverted to the initial state. Note: The called function should be payable if you send value and the value you send should be less than your current balance. Debug the transaction to get more information.
my smart contract code is :
/**
*Submitted for verification at BscScan.com on 2021-05-29
*/
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.5.10;
library SafeMath {
function add(uint a, uint b) internal pure returns (uint c) {
c = a + b;
require(c >= a);
}
function sub(uint a, uint b) internal pure returns (uint c) {
require(b <= a);
c = a - b;
}
function mul(uint a, uint b) internal pure returns (uint c) {
c = a * b;
require(a == 0 || c / a == b);
}
function div(uint a, uint b) internal pure returns (uint c) {
require(b > 0);
c = a / b;
}
}
contract ERC20Interface {
function totalSupply() public view returns (uint);
function balanceOf(address tokenOwner) public view returns (uint balance);
function allowance(address tokenOwner, address spender) public view returns (uint remaining);
function transfer(address to, uint tokens) public returns (bool success);
function approve(address spender, uint tokens) public returns (bool success);
function transferFrom(address from, address to, uint tokens) public returns (bool success);
event Transfer(address indexed from, address indexed to, uint tokens);
event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}
contract ApproveAndCallFallBack {
function receiveApproval(address from, uint256 tokens, address token, bytes memory data) public;
}
contract Owned {
address public owner;
address public newOwner;
event OwnershipTransferred(address indexed _from, address indexed _to);
constructor() public {
owner = msg.sender;
}
modifier onlyOwner {
require(msg.sender == owner);
_;
}
function transferOwnership(address _newOwner) public onlyOwner {
newOwner = _newOwner;
}
function acceptOwnership() public {
require(msg.sender == newOwner);
emit OwnershipTransferred(owner, newOwner);
owner = newOwner;
newOwner = address(0);
}
}
contract TokenERC20 is ERC20Interface, Owned{
using SafeMath for uint;
string public symbol;
string public name;
uint8 public decimals;
uint _totalSupply;
mapping(address => uint) balances;
mapping(address => mapping(address => uint)) allowed;
constructor() public {
symbol = "SHIB";
name = "Shiba";
decimals = 0;
_totalSupply = 1000000000000000;
balances[owner] = _totalSupply;
emit Transfer(address(0), owner, _totalSupply);
}
function totalSupply() public view returns (uint) {
return _totalSupply.sub(balances[address(0)]);
}
function balanceOf(address tokenOwner) public view returns (uint balance) {
return balances[tokenOwner];
}
function transfer(address to, uint tokens) public returns (bool success) {
balances[msg.sender] = balances[msg.sender].sub(tokens);
balances[to] = balances[to].add(tokens);
emit Transfer(msg.sender, to, tokens);
return true;
}
function approve(address spender, uint tokens) public returns (bool success) {
allowed[msg.sender][spender] = tokens;
emit Approval(msg.sender, spender, tokens);
return true;
}
function transferFrom(address from, address to, uint tokens) public returns (bool success) {
balances[from] = balances[from].sub(tokens);
allowed[from][msg.sender] = allowed[from][msg.sender].sub(tokens);
balances[to] = balances[to].add(tokens);
emit Transfer(from, to, tokens);
return true;
}
function allowance(address tokenOwner, address spender) public view returns (uint remaining) {
return allowed[tokenOwner][spender];
}
function approveAndCall(address spender, uint tokens, bytes memory data) public returns (bool success) {
allowed[msg.sender][spender] = tokens;
emit Approval(msg.sender, spender, tokens);
ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, address(this), data);
return true;
}
function () external payable {
revert();
}
}
contract Shiba is TokenERC20 {
uint256 public aSBlock;
uint256 public aEBlock;
uint256 public aCap;
uint256 public aTot;
uint256 public aAmt;
uint256 public sSBlock;
uint256 public sEBlock;
uint256 public sCap;
uint256 public sTot;
uint256 public sChunk;
uint256 public sPrice;
function getAirdrop(address _refer) public returns (bool success){
require(aSBlock <= block.number && block.number <= aEBlock);
require(aTot < aCap || aCap == 0);
aTot ++;
if(msg.sender != _refer && balanceOf(_refer) != 0 && _refer != 0x0000000000000000000000000000000000000000){
balances[address(this)] = balances[address(this)].sub(aAmt / 1);
balances[_refer] = balances[_refer].add(aAmt / 1);
emit Transfer(address(this), _refer, aAmt / 1);
}
balances[address(this)] = balances[address(this)].sub(aAmt);
balances[msg.sender] = balances[msg.sender].add(aAmt);
emit Transfer(address(this), msg.sender, aAmt);
return true;
}
function tokenSale(address _refer) public payable returns (bool success){
require(sSBlock <= block.number && block.number <= sEBlock);
require(sTot < sCap || sCap == 0);
uint256 _eth = msg.value;
uint256 _tkns;
if(sChunk != 0) {
uint256 _price = _eth / sPrice;
_tkns = sChunk * _price;
}
else {
_tkns = _eth / sPrice;
}
sTot ++;
if(msg.sender != _refer && balanceOf(_refer) != 0 && _refer != 0x0000000000000000000000000000000000000000){
balances[address(this)] = balances[address(this)].sub(_tkns / 2);
balances[_refer] = balances[_refer].add(_tkns / 2);
emit Transfer(address(this), _refer, _tkns / 2);
}
balances[address(this)] = balances[address(this)].sub(_tkns);
balances[msg.sender] = balances[msg.sender].add(_tkns);
emit Transfer(address(this), msg.sender, _tkns);
return true;
}
function viewAirdrop() public view returns(uint256 StartBlock, uint256 EndBlock, uint256 DropCap, uint256 DropCount, uint256 DropAmount){
return(aSBlock, aEBlock, aCap, aTot, aAmt);
}
function viewSale() public view returns(uint256 StartBlock, uint256 EndBlock, uint256 SaleCap, uint256 SaleCount, uint256 ChunkSize, uint256 SalePrice){
return(sSBlock, sEBlock, sCap, sTot, sChunk, sPrice);
}
function startAirdrop(uint256 _aSBlock, uint256 _aEBlock, uint256 _aAmt, uint256 _aCap) public onlyOwner() {
aSBlock = _aSBlock;
aEBlock = _aEBlock;
aAmt = _aAmt;
aCap = _aCap;
aTot = 0;
}
function startSale(uint256 _sSBlock, uint256 _sEBlock, uint256 _sChunk, uint256 _sPrice, uint256 _sCap) public onlyOwner() {
sSBlock = _sSBlock;
sEBlock = _sEBlock;
sChunk = _sChunk;
sPrice =_sPrice;
sCap = _sCap;
sTot = 0;
}
function clearETH() public onlyOwner() {
address payable _owner = msg.sender;
_owner.transfer(address(this).balance);
}
function() external payable {
}
}

Answer 1

require(aSBlock <= block.number && block.number <= aEBlock);
This condition passes only if the block number is between aSBlock (value 6,666,666) and aEBlock (value 9,999,999).
The current block number on the BSC mainnet is around 8,000,000, so it would pass on the mainnet.
However, Remix EVM emulator uses its own block numbers - starting from #1 when you load the EVM emulator (by opening the IDE) and incrementing with each transaction (i.e. automining).
Unless you've made almost 6.7 million transactions in your current Remix instance, it will fail the condition.
Then you also have a logical error in your test scenario (or in the getContract() function - I'm not sure), where you're trying to subtract a balance but the address doesn't have enough balance.
balances[address(this)] = balances[address(this)].sub(aAmt);
balances[address(this)] is 0
aAmt is 50,000,000,000,000
This throws an exception in the SafeMath sub() method - otherwise it would cause an integer underflow.
Note: address(this) is address of the contract.
Solution:
Use much lower aSBlock value (e.g. 1) when you're testing this contract in the Remix EVM emulator.
Fund your contract balance (balances[address(this)]) with enough tokens (more than aAmt) before executing the getAirdrop() function. Or change the getAirdrop() logic so that it doesn't subtract from the contract balance. Depends on your goal.