feat: set up function

based on https://github.com/Herohtar/netlify-cms-oauth-firebase/tree/master

firebase.json

@@ -27,5 +27,21 @@
     "auth": {
       "port": 9099
     }
-  }
+  },
+  "functions": [
+    {
+      "source": "functions",
+      "codebase": "default",
+      "ignore": [
+        "node_modules",
+        ".git",
+        "firebase-debug.log",
+        "firebase-debug.*.log",
+        "*.local"
+      ],
+      "predeploy": [
+        "npm --prefix \"$RESOURCE_DIR\" run lint"
+      ]
+    }
+  ]
 }

functions/.eslintrc.js

@@ -0,0 +1,28 @@
+module.exports = {
+  env: {
+    es6: true,
+    node: true,
+  },
+  parserOptions: {
+    "ecmaVersion": 2018,
+  },
+  extends: [
+    "eslint:recommended",
+    "google",
+  ],
+  rules: {
+    "no-restricted-globals": ["error", "name", "length"],
+    "prefer-arrow-callback": "error",
+    "quotes": ["error", "double", {"allowTemplateLiterals": true}],
+  },
+  overrides: [
+    {
+      files: ["**/*.spec.*"],
+      env: {
+        mocha: true,
+      },
+      rules: {},
+    },
+  ],
+  globals: {},
+};

functions/.eslintrc.json

@@ -0,0 +1,87 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "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,
+    // Require 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.
+    // Forces developers to return console logs and http calls in promises. 
+    "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
+  }
+}

functions/.gitignore

@@ -0,0 +1,2 @@
+node_modules/
+*.local

functions/index.js

@@ -0,0 +1,97 @@
+/*
+Based on implementation from https://github.com/Herohtar/netlify-cms-oauth-firebase/tree/master
+ */
+
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+const functions = require("firebase-functions");
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+const express = require("express");
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+const simpleOauth = require("simple-oauth2");
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+const randomstring = require("randomstring");
+
+const oauth = functions.config().oauth;
+const oauthProvider = oauth.provider || "github";
+
+// eslint-disable-next-line require-jsdoc
+function getScript(mess, content) {
+  return `<!doctype html><html><body><script>
+  (function() {
+    function receiveMessage(e) {
+      console.log("receiveMessage %o", e)
+      window.opener.postMessage(
+        'authorization:github:${mess}:${JSON.stringify(content)}',
+        e.origin
+      )
+      window.removeEventListener("message",receiveMessage,false);
+    }
+    window.addEventListener("message", receiveMessage, false)
+    console.log("Sending message: %o", "github")
+    window.opener.postMessage("authorizing:github", "*")
+    })()
+  </script></body></html>`;
+}
+
+const oauth2 = simpleOauth.create({
+  client: {
+    id: oauth.client_id,
+    secret: oauth.client_secret,
+  },
+  auth: {
+    tokenHost: oauth.git_hostname || "https://github.com",
+    tokenPath: oauth.token_path || "/login/oauth/access_token",
+    authorizePath: oauth.authorize_path || "/login/oauth/authorize",
+  },
+});
+
+const oauthApp = express();
+
+oauthApp.get("/auth", (req, res) => {
+  const authorizationUri = oauth2.authorizationCode.authorizeURL({
+    redirect_uri: oauth.redirect_url,
+    scope: oauth.scopes || "repo,user",
+    state: randomstring.generate(32),
+  });
+
+  res.redirect(authorizationUri);
+});
+
+// eslint-disable-next-line consistent-return
+oauthApp.get("/callback", async (req, res) => {
+  const options = {
+    code: req.query.code,
+  };
+
+  if (oauthProvider === "gitlab") {
+    options.client_id = oauth.client_id;
+    options.client_secret = oauth.client_secret;
+    options.grant_type = "authorization_code";
+    options.redirect_uri = oauth.redirect_url;
+  }
+
+  try {
+    const result = await oauth2.authorizationCode.getToken(options);
+    const token = oauth2.accessToken.create(result);
+
+    return res.send(
+        getScript("success", {
+          token: token.token.access_token,
+          provider: oauthProvider,
+        }),
+    );
+  } catch (error) {
+    console.error("Access Token Error", error.message);
+    res.send(getScript("error", error));
+  }
+});
+
+oauthApp.get("/success", (req, res) => {
+  res.send("");
+});
+
+oauthApp.get("/", (req, res) => {
+  res.redirect(301, `/oauth/auth`);
+});
+
+exports.oauth = functions.https.onRequest(oauthApp);