On-chain Health-check for ERC-20 tokens without wasting gas.

WARNING: I provide no guarantee of even a single line of code in this repo. The code hasn't even been tested properly, it's merely an extract from my much larger project. Everything is extra here except contracts/TokenProvidence.sol. Reading that alone should be enough for a little experienced people. For the beginners, I present various js scripts and test scripts for help.

Alpha reveal: On-Chain token checks for:

1. Honeypots: You buy but can't sell.

2. Internal Fee Scams: You buy but there is a huge internal fee (very common during sniping, not particularly a scam but a feature you might want to combat)

3. Buy redirectors: You buy but tokens get redirected to some other address (similar to 2.)

4. Transaction Fee scams: A very high transaction fee (combat this by not setting a very high gasLimit)

5. Off-Chain: A simple check for "verified" tokens on bscscan. Very slow but useful for code-analysis. (Machine learning applications here)

All of the above, instead of sending a real transaction, simulate the run using the call method on the real-time chain update, thereby costing you 0 gas (but a little time before actual transaction, through usually always within blocktime for bsc, easily within blocktime for eth, no tests for other chains for now). Simulating transactions is a cool neat trick, have fun! (Much more advance methods exist for simulating dependencies between transactions, call can only simulate a single txn with no dependency whatsoever, this is not an ideal case in many MEVs).

tldr: Simulate a contract call that buys, approves and sells a token within a single transaction to detect if the token is a honeypot or if it has some very high internal fee.

[1] Don't want to hold bnb in your own wallet for tests? A neat little trick: You can simulate transactions from any address without private key! Just find an address with large bnb reserve and use it to simulate transactions.

Everything is in perspective of bsc but can be easily mimicked to eth. Following changes needs to be made between the testnet and mainnet:

1. Contract: TokenProvidence.sol: Line [42-43] (different keccak256) and line [107-114] different PCS router and factory addresses.

2. TokenProvidence_Mainnet.sol and TokenProvidence_Testnet.sol exist for easy switch.

3. Web3: config.js: Different chainId and node.

{
    "TESTWALLET": {   
        "walletaddress":"0x...",
        "privatekey":""
    },
    "Some other wallet": {
        "walletaddress":"0x...",
        "privatekey":"..."
    }    
}

{
    "tpContactAddress":"0x..."
}

• tests/run.js: Run tests, this is the entry point.
• scripts/driver.js: Web3js interactions with the contract.
• scripts/utils.js: Some simple utilities.
• config/config.js: Configuration for gas price, addresses and more.
• config/addresses.json: Contains the deployed contract address.
• config/private_key.json: Your private key(s)
• contracts/TokenProvidence.sol: The generic contract file.
• contracts/TokenProvidence_Mainnet.sol: The contract file for mainnet.
• contracts/TokenProvidence_Testnet.sol: The contract file for testnet.
• abi/tokenProvidence.json: abi for the contract, get this after contract compilation. I usually just use the Remix IDE.

There are various ways, but I usually use Remix IDE. Deploying on mainnet will cost gas, use testnet for learning and testing purposes. Use the faucet to get tokens on the testnet.

• Get BSCScan API here.

I provide none, feel free to raise pull requests or issues though, might be helpful.