Refactor _wiki.js and add helper comments

_wiki.js

@@ -1,54 +1,104 @@
-const fs = require('fs-extra');
+const fs = require('fs-extra'); // Reading README.md
-const path = require('path');
+const path = require('path'); // Get the correct path for README.md
-const fetch = require('node-fetch');
+const fetch = require('node-fetch'); // Make calls to Reddit from Node.js
-const qs = require('qs');
+const qs = require('qs'); // Properly build a query for node-fetch POST
 
+// REDDIT_: For authentication with Reddit API. Oauth MUST be used. ID and Secret come from a "script" app type.
 const REDDIT_USER = process.env.REDDIT_USER || 'username';
 const REDDIT_PASS = process.env.REDDIT_PASS || 'password';
 const REDDIT_CLIENT_ID = process.env.REDDIT_CLIENT_ID || 'clientid';
 const REDDIT_CLIENT_SECRET = process.env.REDDIT_CLIENT_SECRET || 'clientsecret';
+
+// WIKI_: For the Reddit Wiki
 const WIKI_SUBREDDIT = 'privacy';
 const WIKI_PAGE = 'de-go-git';
-const WIKI_REASON = 'Automated edit from [GitHub repo](https://github.com/tycrek/degoogle)';
+const WIKI_REASON = 'Automated edit from GitHub repo: https://github.com/tycrek/degoogle';
+
+// Helps POST data be submitted properly
 const CONTENT_TYPE = 'application/x-www-form-urlencoded';
 
-updateWiki()
+updateWiki();
 
+/**
+ * Update the Reddit wiki
+ */
 function updateWiki() {
+    // Endpoints for each of our fetches to Reddit
     let endpoints = {
         revisions: `https://old.reddit.com/r/${WIKI_SUBREDDIT}/wiki/revisions/${WIKI_PAGE}.json`,
         token: 'https://www.reddit.com/api/v1/access_token',
         edit: `https://oauth.reddit.com/r/${WIKI_SUBREDDIT}/api/wiki/edit`
     };
+
+    // Initial basic authorization for getting the Oauth token
     let basicAuth = `Basic ${Buffer.from(REDDIT_CLIENT_ID + ':' + REDDIT_CLIENT_SECRET).toString('base64')}`;
 
-    let lastId;
+    let lastId, token;
     
-    fetch(endpoints.revisions)
+    getLastRevision(endpoints.revisions)
+        .then((mLastId) => lastId = mLastId)
+        .then(() => getToken(endpoints.token, basicAuth))
+        .then((mToken) => token = mToken)
+        .then(() => putWiki(endpoints.edit, lastId, token))
+        .catch((err) => (console.error(err), process.exit(1)));
+}
+
+/**
+ * Get the last revision ID on the Wiki. Required otherwise editing the wiki fails
+ * @param {String} endpoint Endpoint of where to get the ID's
+ */
+function getLastRevision(endpoint) {
+    return new Promise((resolve, reject) => {
+        fetch(endpoint)
             .then((response) => response.json())
-    .then((json) => json.data.children[0].id)
+            .then((json) => json.data.children[0].id) // children[0] is the most recent edit
-    .then((mLastId) => {
+            .then((lastId) => resolve(lastId))
-        lastId = mLastId;
+            .catch((err) => reject(err));
-        return fetch(endpoints.token, {
-            method: 'POST',
-            headers: { 'Authorization': basicAuth, 'Content-Type': CONTENT_TYPE },
-            body: qs.stringify({ grant_type: 'password', username: REDDIT_USER, password: REDDIT_PASS })
     });
+}
+
+/**
+ * Gets an Oauth token used to edit the Wiki
+ * @param {String} endpoint Endpoint of where to get the token
+ * @param {String} auth Initial authorization data to get the better Oauth data
+ */
+function getToken(endpoint, auth) {
+    return new Promise((resolve, reject) => {
+        fetch(endpoint, {
+            method: 'POST',
+            headers: { 'Authorization': auth, 'Content-Type': CONTENT_TYPE },
+            body: qs.stringify({ grant_type: 'password', username: REDDIT_USER, password: REDDIT_PASS })
         })
             .then((response) => response.json())
-    .then((json) => {
+            .then((json) => json.access_token)
-        return fetch(endpoints.edit, {
+            .then((token) => resolve(token))
+            .catch((err) => reject(err));
+    });
+}
+
+/**
+ * Post the contents from the README into the wiki
+ * @param {String} endpoint Endpoint for editing the wiki
+ * @param {String} lastId Revision ID for the Wiki
+ * @param {String} token Oauth token for authenticating with the Reddit API
+ */
+function putWiki(endpoint, lastId, token) {
+    return new Promise((resolve, reject) => {
+        fetch(endpoint, {
             method: 'POST',
-            headers: { 'Authorization': `bearer ${json.access_token}`, 'Content-Type': CONTENT_TYPE },
+            headers: { 'Authorization': `bearer ${token}`, 'Content-Type': CONTENT_TYPE },
             body: qs.stringify({
                 content: fs.readFileSync(path.join(__dirname, 'README.md')).toString(),
                 page: WIKI_PAGE,
                 reason: WIKI_REASON,
                 previous: lastId
             })
-        });
         })
             .then((response) => response.json())
-    .then((json) => console.log(json))
+            .then((json) => {
-    .catch((err) => console.error(err));
+                if (Object.keys(json).length == 0) resolve();
+                else throw Error(json);
+            })
+            .catch((err) => reject(err));
+    });
 }