Advanced Solidity - Crowdsale of PupperCoin Token

A new start-up has decided to crowdsale their PupperCoin token in order to help fund the network development. This network will be used to track the dog breeding activity across the globe in a decentralized way, and allow humans to track the genetic trail of their pets. You have already worked with the necessary legal bodies and have the green light on creating a crowdsale open to the public. However, the start-up is required to enable refunds if the crowdsale is successful and the goal is met, and it is only allowed to raise a maximum of 300 Ether. The crowdsale will run for 24 weeks.

ERC20 token should be created and will be minted through a Crowdsale contract that can leverage the OpenZeppelin Solidity library.

This crowdsale contract will manage the entire process, allowing users to send ETH and get back PUP (PupperCoin). This contract will mint the tokens automatically and distribute them to buyers in one transaction.

It will need to inherit Crowdsale, CappedCrowdsale, TimedCrowdsale, RefundableCrowdsale, and MintedCrowdsale.

The crowdsale will be conducted on the Kovan testnet in order to get a real-world pre-production testing.

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Instructions

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Crowd-selling PupperCoin coded on Solidity to fund generic trailing project on PUPS. Two contracts will be written written and deployed on Remix.

Creating the project

Using Remix, create a file called PupperCoin.sol and create a standard ERC20Mintable token.

Create a new contract named PupperCoinCrowdSale.sol, and prepare it like a standard crowdsale.

Designing the contracts

1. ERC20 PupperCoin

Use a standard ERC20Mintable and ERC20Detailed contract, hardcoding 18 as the decimals parameter, and leaving the initial_supply parameter alone.

2. PupperCoincrowdsale

Leverage the Crowdsale starter code, saving the file in Remix as Crowdsale.sol.

Bootstrap the contract by inheriting the following OpenZeppelin contracts:

• Crowdsale

• MintedCrowdsale

• CappedCrowdsale

• TimedCrowdsale

• RefundablePostDeliveryCrowdsale

Provide parameters for all of the features of crowdsale, such as the name, symbol, wallet for fundraising and goal

Hardcode a rate of 1, to maintain parity with Ether units (1 TKN per Ether, or 1 TKNbit per wei). To customize crowdsale rate, follow the Crowdsale Rate calculator on OpenZeppelin's documentation. Essentially, a token (TKN) can be divided into TKNbits just like Ether can be divided into wei. When using a rate of 1, just like 1000000000000000000 wei is equal to 1 Ether, 1000000000000000000 TKNbits is equal to 1 TKN.

Since RefundablePostDeliveryCrowdsale inherits the RefundableCrowdsale contract, which requires a goal parameter, the RefundableCrowdsale constructor must be called from PupperCoinCrowdsale constructor as well as the others. RefundablePostDeliveryCrowdsale does not have its own constructor, so just use the RefundableCrowdsale constructor that it inherits.

If one forgets to call the RefundableCrowdsale constructor, the RefundablePostDeliveryCrowdsale will fail since it relies on it (it inherits from RefundableCrowdsale), and does not have its own constructor.

When passing the open and close times, use now and now + 24 weeks to set the times properly from PupperCoinCrowdsaleDeployer contract.

3. PupperCoinSaleDeployer Contract

Leverage the OpenZeppelin Crowdsale Documentation for an example of a contract deploying another, as well as the starter code provided.

Testing the Crowdsale

Test the crowdsale by sending Ether to the crowdsale from a different account (not the same account that is raising funds), then crowdsale works as expected is confirmed, try to add the token to MyCrypto and test a transaction. In order to test the time functionality, replace now with fakenow, and create a setter function to modify fakenow to whatever time want to simulate. Set the close time to be now + 5 minutes, or whatever timeline (eg. 5 minutes) to test for a shorter crowdsale.

When sending Ether to the contract, make sure to hit your goal that is set, and finalize the sale using the Crowdsale's finalize function. In order to finalize, isOpen must return false (isOpen comes from TimedCrowdsale which checks to see if the close time has passed yet). Since the goal is 300 Ether, it needs to be sent from multiple accounts. Create new workspace in Ganache, if prefunded accounts are exhausted.

Remember, the refund feature of RefundablePostDeliveryCrowdsale only allows for refunds once the crowdsale is closed and the goal is met. See the OpenZeppelin RefundableCrowdsale documentation for details as to why this is logic is used to prevent potential attacks on your token's value.

Deploying the Crowdsale

Deploy the crowdsale to the Kovan or Ropsten testnet, and store the deployed address for later. Switch MetaMask to your desired network, and use the Deploy tab in Remix to deploy your contracts. Take note of the total gas cost, and compare it to how costly it would be in reality.

Guide for Contract Deployment Process

• Deployment on Kovan testnet

In order for crowdsale contracts to function accurately, smart contracts should be executed in the following order.

1. Open Ganache and Metamask, change the network to Kovan. Pre-fund the address to ensure successful deployment of the contract as it would require some Gas.

2. Deployment of the first contract puppercoin (Solidity codes written in this contract should be imported to Crowdsale.sol). Paramaters required for deployment: name, symbol, initial_supply.

3. Deploy PupperCoinSaleDeployer Contract. Parameters required: name, symbol, wallet (Same as your Wallet Address) and goal

   • Note: Token_Address & Token_Sale_Address

4. Deploy PupperCoinSale Contract with Token_sale_address in the At_Address section

5. Deploy PupperCoin Contract with Token_Address in the At_Address section

6. Contract Deployed - Check the getter functions to see whether contract has been deployed properly.

• Features

1. Buy Tokens under PupperCoinSale on Remix

   • Validate the transaction on Etherscan

2. Add Custom Tokens (PUPCOIN) to Metamask
   (a) Under Assets, click on Add Tokens
   (b) Under Add Tokens, click on Custom Tokens
   (c) Parameters:
   

   • Token Address - Token_Sale_Address
     
   • Name - Token_Name
     
   • Decimal - 18
     

3. Metamask wallet gives an overview of tokens`

4. View Tokens on MyCrypto Wallet

Access wallet on MyCrypto via the private key in Ganache. Add Custom Token in MyCrypto Wallet. Balance will be be updated.

Resources

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• Remix
• Solidity_Docs
• Solidity_Example
• OpenZeppelin Crowdsale Documentation
• Kovan_Faucet