# Solidity-101 Basics 初階語法教學程式碼

## 註解、Natspace format

// SPDX-License-Identifier: GPL-3.0

pragma solidity >= 0.8.4;

// 單行註解

/**
   多行註解
 */

/**
   @dev 說明
   @param 參數
 */
function age(uint256 rings) external virtual pure returns (uint256) {
    return rings + 1;
}

## Booleans

// SPDX-License-Identifier: GPL-3.0
// solidity內1, 0不能對應true, false
pragma solidity >= 0.8.4;

contract Booleans {
    bool public isActive = true;
    
    constructor() {}
}

## INTEGER

// SPDX-License-Identifier: GPL-3.0
// 在真正撰寫solidity時，較少出現負數的情形，故通常都用uint即可

pragma solidity >= 0.8.4;

contract Integer {
    uint256 public totalSupply = 250;
    int256 public minuseSupply = -250;
    
    constructor() {}
}

## String

// SPDX-License-Identifier: GPL-3.0

pragma solidity >= 0.8.4;

contract String {
    string public Message = "Hello World";
    
    constructor() {}
}

## Bytes

// SPDX-License-Identifier: GPL-3.0
// 通常使用16進制 hex

pragma solidity >= 0.8.4;

contract Bytes {
    bytes1 public hex1 = 0x01;
    bytes32 public hex32 = 0x0102030405060708091011121314151617181920212223242526272829303132;
    
    constructor() {}
}

## Address

// SPDX-License-Identifier: GPL-3.0
// 以太坊的address共160bits = 20bytes 也就是0x後面40個字元
pragma solidity >= 0.8.4;

contract Storage {
    address public owner = 0x5B38Da6a701c568545dCfcB03FcB875f56beddC4;
    address public other = 0xAb8483F64d9C6d1EcF9b849Ae677dD3315835cb2;
    
    function getOwnerBalance() public view returns (uint256) {
        return owner.balance;
    }

    // (2300 gas, throws error)
    // 現在的標準中盡量都沒有在使用transfer了
    // payable()是防呆用，若沒加上就不可.transfer() & .send()
    function sendValueByTransfer(address to) public {
        payable(to).transfer(15 ether);
    }

    // (2300 gas, returns bool)
    // 2300 gas 是因為轉帳只是改數字，不用改變數狀態等，不用耗費這麼多gas
    function sendValueTo(address to) public {
        bool sent = payable(to).send(15 ether);
        require(sent, "Failed to send Ether");
    }

    // call (forward all gas or set gas, returns bool)
    // 用call可以傳value or data給目標地址
    // 但EOA沒有合約的data，故可以轉錢給他且不給data
    function sendValueByCallTo(address to) public {
        (bool sent, bytes memory data) = to.call{value: 15 ether}("");
        require(sent, "Failed to send Ether");
    }

    receive() external payable {}
    fallback() external payable {}
}

## Variables

// SPDX-License-Identifier: GPL-3.0

pragma solidity >= 0.8.4;

contract Variables {
    uint number;
}

# 補充內容

## bit

計算機世界中最小單位，一個 byte 是 8 個 bits 組成，每個 bit 都是由最小單位 0, 1 組成。

一個 bit 可以表示為 0 或 1，也可以等於「開或關」，也能等於數字的「零」或「一」。



### 加解密演算法

#### ed25519 加解密訊息

const {
  generateKeyPairSync,
  createCipheriv,
  createDecipheriv,
  randomBytes,
  createHash
} = require('crypto')
const { publicKey, privateKey } = generateKeyPairSync('ed25519', {
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem',
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem',
  },
})
const iv = randomBytes(16).toString('hex').slice(0, 16)
const key = createHash('sha256').update(publicKey).digest('base64')

const message = new Buffer.from('Hello World!')

const cipher = createCipheriv('aes-256-gcm', key.substr(0, 32), iv)
const encrypted = cipher.update(message, 'utf8', 'hex')
const encryptedFinal = cipher.final('hex')

const msgCipher = encrypted + encryptedFinal

const decipher = createDecipheriv('aes-256-gcm', key.substr(0, 32), iv)
const msgDecipher = decipher.update(msgCipher, 'hex', 'utf8')
console.log(msgDecipher.toString())

#### 訊息簽章

const {
  generateKeyPairSync,
  sign,
  verify,
  publicEncrypt,
  privateDecrypt
} = require('crypto');
const data = require('./data.json');
const boyKeys = generateKeyPairSync('rsa', {
  modulusLength: 4096,
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem'
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem'
  }
});
const girlKeys = generateKeyPairSync('rsa', {
  modulusLength: 4096,
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem'
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem'
  }
});
const message = new Buffer.from(JSON.stringify(data));
const enc = publicEncrypt(girlKeys.publicKey, message);
const signature = sign('sha256', enc, boyKeys.privateKey);
const isValid = verify('sha256', enc, boyKeys.publicKey, signature);
if (isValid) {
  console.log('valid success!', isValid)
  const dec = privateDecrypt(girlKeys.privateKey, enc);
  console.log(dec.toString());
}