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Ethereum ERC20 Crowd-sale Contract

This is a basic example of a crowd-sale with a brand new ERC20 token. First deploy the Sale contract, and then the ERC20 token contract. The ERC20 contract will require the Sale Contract's ethereum address. See attribution.1

Contract Features

  • Creates/Mints 5+ million Tokens and holds them inside contract.
  • ERC20 and Sale Contract both reference each other
  • Converts payable ETH to TOKEN's directly to user
  • ETH payed to contract is forwarded to a different wallet (holds ICO funds)
  • Ability to turn on/off transfer of coins. (via sale contract)
  • Token contributions will be removed from the Mint and transferred to the purchaser.
  • Users that have tokens held can release them once time has passed without owner permission.

Contract Variables

  • Crowd-sale ending on a specific block number
  • Total token Supply
  • ETH/TOKEN exchange rate
  • Developers/Founders allocation, to be released at later date.

Deployed Instructions

See deploy-template_v0-sale and deploy-template_v0-token for specific deployment variables and deploy-template for step by step example using this repository including verifying the contract with Etherscan.

  1. Deploy the Sale contract first. Be sure to change the token details (TOTAL_SUPPLY, EXCHANGE_RATE, FOUNDER_GROUP_ONE, FOUNDER_GROUP_TWO) You will need a wallet address for ETH Sale proceeds (Example: 0x6FEFc3F6239F2A1aF8Fe093877BA2a1e81da4231) which will be funded after each contribution. Sale("0x7824773BFFA00f2b20b2db3B5fCC22C3713542E9"). The following will deploy the Sale's contract:
npx hardhat run --network alchemy ./scripts/deploy-template_v0-sale.ts

where ETH_PUBLIC_KEY is set to the owner's public key - creating contract 0xb92B3B34b5f5269407B7A24e1Cb98c553eFC41B4 Take note of the Sale contract and using the following to publish the contract on Etherscan.

npx hardhat verify --network ropsten 0xb92B3B34b5f5269407B7A24e1Cb98c553eFC41B4 '0x6FEFc3F6239F2A1aF8Fe093877BA2a1e81da4231'

  1. Once you have the Sale contract, deploy the Token contract. Be sure to change the token details (TOTAL_SUPPLY, EXCHANGE_RATE, FOUNDER_GROUP_ONE, FOUNDER_GROUP_TWO) and createTokens initial minted amount. When you deploy the Token contract, you must include the Sale contract address when you deploy the contract. Example: Token("0xb92B3B34b5f5269407B7A24e1Cb98c553eFC41B4"), and npx hardhat run --network alchemy ./scripts/deploy-template_v0-token.ts where SALE_CONTRACT is updated with the aforementioned contract - creating token contract 0x0F3CA246a7A3043FF92Ff46B63F93752688b385D

  2. Now you can finalize the process by running the setup function to the Sale contract. The setup function requires the aforementioned token contract address and an ending block number of when the ICO should end. The owner of the contract can also end the sale at any time. As of June 10, 2021 the average block time on Ethereum is 13.1 seconds or 5760 blocks per day. If ending block number is less than the current block the function fails, if ending block + current block is more than 10512000 blocks or the estimate for 5 years, then the function also fails. Edit the Setup function to change. Example: setup("0x7824773BFFA00f2b20b2db3B5fCC22C3713542E9", 200000) - 0x682392db4d184fc5e96c7dbf53b29c891d7158422ecd7935b484159ed633ca79

  3. Your ICO has begun! You can now send ETH to the Sale contract address to receive your new tokens! I sent 1 ETH with data: 0xd7bb99ba to my Sale contract address. The user must send ETH or the transaction will fail! Example: 1 ETH - Data: 0xd7bb99ba - Gas Limit: 80000 creating transaction 0xbf541f8b39d5b94670c909e85cec8035b7c30d178d2c6e5637e1ad395ca2d9b2 This transaction sent 1 ETH to the ETH wallet address and also sent me 600 Tokens.

  4. Once you received your $100 million for the ICO you can close it at anytime with the closeSale function. Example: closeSale() creating transaction . The ICO Sale is over!

This ICO-sale contract will allow you to change owners, change token rate per ETH, hold tokens for a specific amount of time, and allow users that have tokens held. The Sale contract locks the tokens, once the set block height has been passed, the user can run releaseHeldCoins() (``) to the sale contract to receive their tokens if the time has passed! Example:

Crowd-sale Contract

function contribute() external payable is the function for the purchaser to mint new tokens. (Data: 0xd7bb99ba)

ERC20 Additions

The ERC20 contract has a couple additions to be reviewed by you. When the token contract is deployed, it will require the Sale Contract address and will be set 1 and only 1 time. If you set an incorrect address when you deploy the ERC20 you'll have to re-deploy the sale and ERC20 again. This is done as a security precaution, 1 time set functions.

Minting Tokens

Minting Tokens call comes from the Sale contract, when the ERC20 is deployed it will force the Sale contract. function mintToken(address to, uint256 amount) external returns (bool success);

Change "transfer" method from the Sale Contract. function changeTransfer(bool allowed);

Hold Token Period

The Sale Contract will allow you to hold a specific amount of tokens for an amount of time before being released directly to address. The createHoldToken function requires an address and the amount of tokens given at end of period.

function createHeldCoins() internal {
  createHoldToken(FOUNDER_GROUP_ONE, 100000000000000000000000); // 100,000
  createHoldToken(FOUNDER_GROUP_TWO, 250000000000000000000000); // 250,000
}

You can change the amount of blocks in future to release.

function createHoldToken(address _to, uint256 amount) internal {
...
  heldTimeline[_to] = block.number + 200000;
...
}

Once a time period as passed, the wallet owner can do a contract call to receive the tokens. (Data: 0x6ce5b3cf)

function releaseHeldCoins()

Attribution

1The Sale contract was updated tp ^0.8.0 from HunterLong's ^0.4.21 Solidity contract.

2The project template was hacked from PaulRBerg's template.

3Super awesome and helpful patterns from PaulRBerg's repo and Task's Solidity by Example Hack section.