# 新增Firebase Admin SDK到node server
利用後端伺服器去發送通知給裝置

## 大綱
- <a href="#安裝">安裝</a>
- <a href="#設定金鑰">設定金鑰</a>
- <a href="#初始化SDK">初始化SDK</a>
- <a href="#發送-單裝置">發送-單裝置</a>
- <a href="#發送-多裝置">發送-多裝置</a>
- <a href="#發送-特定主題">發送-特定主題</a>

## 安裝
> npm install firebase-admin –save

## 設定金鑰
點擊專案下的服務帳戶<br>
<br>
產生新的密鑰並放到對應的路徑

## 初始化SDK

var admin = require('firebase-admin');
var serviceAccount = require('path/to/serviceAccountKey.json');

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
  databaseURL: 'https://.firebaseio.com'
});

## 發送-單裝置

var registrationToken = 'YOUR_REGISTRATION_TOKEN';

admin.messaging().send(message)
  .then((response) => {
    // Response 是一個字串型別的 message ID.
    console.log('Successfully sent message:', response);
  })
  .catch((error) => {
    console.log('Error sending message:', error);
  });

## 發送-多裝置

// Create a list containing up to 500 registration tokens.
// These registration tokens come from the client FCM SDKs.

const registrationTokens = [
  'YOUR_REGISTRATION_TOKEN_1',
  // …
  'YOUR_REGISTRATION_TOKEN_N',
];

const message = {
  data: {score: '850', time: '2:45'},
  tokens: registrationTokens,
}

admin.messaging().sendMulticast(message)
  .then((response) => {
    console.log(`${response.successCount} messages were sent successfully`);
  }

## 發送-特定主題

const topic = 'highScores';

const message = {
  data: {
    score: '850',
    time: '2:45'
  },
  topic: topic
};

// Send a message to devices subscribed to the provided topic.
getMessaging().send(message)
  .then((response) => {
    // Response is a message ID string.
    console.log('Successfully sent message:', response);
  })
  .catch((error) => {
    console.log('Error sending message:', error);
  });

參考來源:
- https://firebase.google.com/docs/admin/setup

- https://firebase.google.com/docs/cloud-messaging/send-message