# Truffle

[Truffle](https://www.trufflesuite.com/) is a powerful tool for contract development assistance.

## Environment installation <a href="#environment-installation" id="environment-installation"></a>

* Node

Refer to [Installing Node.js](https://nodejs.org/en/download/package-manager/)。

* Truffle

Install Truffle

```shell
npm install -g truffle
```

Execute the following commands after installation:

```shell
truffle version
```

Information displayed similar to the following indicates a successful installation.

```
Truffle v5.3.3 (core: 5.3.3)
Solidity v0.5.16 (solc-js)
Node v14.16.1
Web3.js v1.3.5
```

## Create Project <a href="#create-project" id="create-project"></a>

Create project directory

```shell
mkdir mydapp
cd mydapp/
```

Use truffle to initialize project

```shell
truffle init
```

After the project is initialized, the directory structure is as follows:

```
|-- contracts         //Folder, for contract file storage
|-- migrations        //Folder, for deployment script keeping
|-- test              //Folder, for test file keeping
|-- truffle-config.js //Truffle deployment file of this project
```

Edit configuration file

```
const HDWalletProvider = require('@truffle/hdwallet-provider');
const fs = require('fs');
const mnemonic = fs.readFileSync(".secret").toString().trim();

module.exports = {

  networks: {
    testnet: {
    mainnet: {
      provider: () => new HDWalletProvider(mnemonic, 'https://rpc.koisan-chain.com'),
      network_id: 312,
      gasPrice: 500000000000
    }
  },

  // Set default mocha options here, use special reporters etc.
  mocha: {
    // timeout: 100000
  },

  // Configure your compilers
  compilers: {
    solc: {
      // version: "^0.6.12",
    }
  }
};
```

Note: it requires private key to be passed in for `Provider`, this is the seed phrase for the account you'd like to deploy from. Create a new `.secret` file in root directory and enter your private key to get started. To export private key from metamask wallet you can go to `Account Details`, then click button `Export Private Key` and you will see the private key by enter your password of your account.

## Edit Contract <a href="#edit-contract" id="edit-contract"></a>

Put the customized contract in the `contracts` folder and modify the deployment script in the `migrations` folder

* Deploy Contract

Execute deployment commands

```shell
truffle migrate --network testnet
```

Taking the project MetaCoin for instance. Contract codes are as follows:

```
pragma solidity >=0.4.25 <0.7.0;

import "./ConvertLib.sol";

// This is just a simple example of a coin-like contract.
// It is not standards compatible and cannot be expected to talk to other
// coin/token contracts. If you want to create a standards-compliant
// token, see: https://github.com/ConsenSys/Tokens. Cheers!

contract MetaCoin {
    mapping (address => uint) balances;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);

    constructor() public {
        balances[tx.origin] = 10000;
    }

    function sendCoin(address receiver, uint amount) public returns(bool sufficient) {
        if (balances[msg.sender] < amount) return false;
        balances[msg.sender] -= amount;
        balances[receiver] += amount;
        emit Transfer(msg.sender, receiver, amount);
        return true;
    }

    function getBalanceInEth(address addr) public view returns(uint){
        return ConvertLib.convert(getBalance(addr),2);
    }

    function getBalance(address addr) public view returns(uint) {
        return balances[addr];
    }
}
```

Output results are as follows:

```
Compiling your contracts...
===========================
> Everything is up to date, there is nothing to compile.



Starting migrations...
======================
> Network name:    'testnet'
> Network id:      53
> Block gas limit: 6721975 (0x6691b7)


1_initial_migration.js
======================

   Deploying 'Migrations'
   ----------------------
   > transaction hash:    0xc92b16882582cab42a92ed0272133cdb36291b02561b192fef609110549ca8ae
   > Blocks: 0            Seconds: 0
   > contract address:    0xF73901C6560B5fb487FAbF391C1Ce6b1E1B6B8F6
   > block number:        1
   > block timestamp:     1620896663
   > account:             0x3845970B03eDD143295Ae2B1EaE73Beb1ddFd6f3
   > balance:             99.9967165
   > gas used:            164175 (0x2814f)
   > gas price:           500 gwei
   > value sent:          0 ETH
   > total cost:          0.0032835 ETH


   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:           0.0032835 ETH


2_deploy_contracts.js
=====================

   Deploying 'ConvertLib'
   ----------------------
   > transaction hash:    0xa94c9b9ecd732990ae7d2a69a20061f2ab6f23c6ac8caa1e0380204d32a831d3
   > Blocks: 0            Seconds: 0
   > contract address:    0x2f32569cD13C389D430384654092275DcD4691E3
   > block number:        3
   > block timestamp:     1620896664
   > account:             0x3845970B03eDD143295Ae2B1EaE73Beb1ddFd6f3
   > balance:             99.99396028
   > gas used:            95470 (0x174ee)
   > gas price:           500 gwei
   > value sent:          0 ETH
   > total cost:          0.0019094 ETH


   Linking
   -------
   * Contract: MetaCoin <--> Library: ConvertLib (at address: 0x2f32569cD13C389D430384654092275DcD4691E3)

   Deploying 'MetaCoin'
   --------------------
   > transaction hash:    0x8079e79c2055b1fcfcaee0f6c9147805b5d3c0046466f695a862e8692ec9ece2
   > Blocks: 0            Seconds: 0
   > contract address:    0xA271b814E956AcE4b5c8d68613B44C245dbfA9a8
   > block number:        4
   > block timestamp:     1620896664
   > account:             0x3845970B03eDD143295Ae2B1EaE73Beb1ddFd6f3
   > balance:             99.98822898
   > gas used:            286565 (0x45f65)
   > gas price:           500 gwei
   > value sent:          0 ETH
   > total cost:          0.0057313 ETH


   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:           0.0076407 ETH


Summary
=======
> Total deployments:   3
> Final cost:          0.0109242 ETH
```

## Interaction <a href="#interaction" id="interaction"></a>

Enter interactive console

```shell
truffle console --network testnet
truffle(testnet)> 
```

Obtain contract abstraction

```
truffle(testnet)> let instance = await MetaCoin.deployed()
undefined
truffle(testnet)> instance
```

Initiate a transaction on console

```
truffle(testnet)> let accounts = await web3.eth.getAccounts()
truffle(testnet)> instance.sendCoin(accounts[1], 10, {from: accounts[0]})
```

Initiate a call on console

Take the method of calling contract `getBalance` as an example:

```
truffle(testnet)> let balance = await instance.getBalance(accounts[0])
truffle(testnet)> balance.toNumber()
```


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