[WIP] add manage FCM tokens sample

fcm-manage-tokens/README.md

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+# Manage FCM registration tokens
+
+This sample demonstrates how FCM registration tokens should be
+managed on the server side.
+
+1. Clients should regularly send valid tokens to the server and
+the server updates their corresponding timestamp.
+2. The server should periodically prune stale tokens. Unsubscribing
+from topics then deleting them.
+
+
+## Functions Code
+
+See file [functions/index.js](functions/index.js) for the code.
+
+Storing and pruning the tokens is done using the [Firebase Admin SDK](https://www.npmjs.com/package/firebase-admin).
+
+The dependencies are listed in [functions/package.json](functions/package.json).
+
+
+## Trigger rules
+
+- updateToken is triggered...
+- pruneTokens is triggered...
+
+
+
+## Setup and test this sample section
+
+To deploy and test the sample:
+
+ - TODO(kroikie): describe usage of sample
+

fcm-manage-tokens/firebase.json

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+{}

fcm-manage-tokens/functions/.eslintrc.json

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+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 2017
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Requre the use of === and !==
+    "eqeqeq": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}

fcm-manage-tokens/functions/index.js

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+/**
+ * Copyright 2022 Google Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+const admin = require('firebase-admin');
+const functions = require('firebase-functions');
+const {write} = require("firebase-functions/logger");
+admin.initializeApp();
+
+const EXPIRATION_TIME = 1000 * 60 * 60 * 24 * 30; // 30 days
+
+/**
+ * Callable function that stores/updates the freshness timestamp associated with the
+ * submitted FCM registration token.
+ *
+ * Note: Most FCM registration tokens would be associated with a user. In that case
+ * there should be some mapping between the user and the token(s) when stored.
+ */
+exports.updateToken = functions.https.onCall(async (data, context) => {
+  const registrationToken = data['fcm_token'];
+  await admin.firestore().collection('tokens').doc(registrationToken).set(
+      {timestamp: Date.now()},
+      {merge: true}
+  );
+});
+
+/**
+ * Scheduled function that runs once a day. It retrieves all stale tokens then
+ * unsubscribes them from 'topic1' then deletes them.
+ *
+ * Note: topic1 is an example topic here. It is up to the developer to unsubscribe
+ * all topics the token is subscribed to.
+ */
+exports.pruneTokens = functions.pubsub.schedule('every 24 hours').onRun(async (context) => {
+  const staleTokensResult = await admin.firestore().collection('tokens')
+      .where("timestamp", "<", Date.now() - EXPIRATION_TIME)
+      .get();
+
+  const staleTokens = staleTokensResult.docs.map(staleTokenDoc => staleTokenDoc.id);
+
+  await admin.messaging().unsubscribeFromTopic(staleTokens, 'topic1');
+
+  const deletePromises = [];
+  for (const staleTokenDoc of staleTokensResult.docs) {
+      deletePromises.push(staleTokenDoc.ref.delete());
+  }
+  await Promise.all(deletePromises);
+});

fcm-manage-tokens/functions/package.json

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+{
+  "name": "developer-motivator-functions",
+  "description": "A simple developer motivator using Cloud Function and firebase analytics",
+  "dependencies": {
+    "firebase-admin": "^10.0.0",
+    "firebase-functions": "^3.16.0"
+  },
+  "devDependencies": {
+    "eslint": "^6.8.0",
+    "eslint-plugin-promise": "^4.2.1"
+  },
+  "scripts": {
+    "lint": "./node_modules/.bin/eslint --max-warnings=0 .",
+    "serve": "firebase emulators:start --only functions",
+    "shell": "firebase functions:shell",
+    "start": "npm run shell",
+    "deploy": "firebase deploy --only functions",
+    "logs": "firebase functions:log",
+    "compile": "cp ../../tsconfig.template.json ./tsconfig-compile.json && tsc --project tsconfig-compile.json"
+  },
+  "engines": {
+    "node": "14"
+  },
+  "private": true
+}