🎉 add ability to update gist only if changed

index.js

@@ -3,6 +3,49 @@ const http = require('https');
 
 try {
 
+  function updatingGist(data) {
+    // Perform the actual request. The user agent is required as defined in
+    // https://developer.github.com/v3/#user-agent-required
+    const updateGistOptions = {
+      host: 'api.github.com',
+      path: '/gists/' + core.getInput('gistID'),
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'Content-Length': data.length,
+        'User-Agent': 'Schneegans',
+        'Authorization': 'token ' + core.getInput('auth'),
+      }
+    };
+  
+    return doRequest(updateGistOptions, data)
+  }
+  
+  function doRequest(options, data) {
+    return new Promise((resolve, reject) => {
+      const req = http.request(options, (res) => {
+        res.setEncoding('utf8');
+        let responseBody = '';
+  
+        res.on('data', (chunk) => {
+          responseBody += chunk;
+        });
+  
+        res.on('end', () => {
+          const { statusCode, statusMessage } = res;
+          resolve({ statusCode, statusMessage, body: JSON.parse(responseBody) });
+        });
+      });
+  
+      req.on('error', (err) => {
+        reject(err);
+      });
+  
+      req.write(data)
+      req.end();
+    });
+  }
+
   // This object will be stringified and uploaded to the gist. The
   // schemaVersion, label and message attributes are always required. All others
   // are optional and added to the content object only if they are given to the
@@ -13,6 +56,8 @@ try {
     message: core.getInput('message')
   };
 
+  const updateIfChanged     = core.getInput('updateIfChanged');
+  
   // Compute the message color based on the given inputs.
   const color                = core.getInput('color');
   const valColorRange        = core.getInput('valColorRange');
@@ -64,6 +109,7 @@ try {
   const logoPosition = core.getInput('logoPosition');
   const style        = core.getInput('style');
   const cacheSeconds = core.getInput('cacheSeconds');
+  const filename     = core.getInput('filename');
 
   if (labelColor != '') {
     content.labelColor = labelColor;
@@ -101,39 +147,72 @@ try {
     content.cacheSeconds = parseInt(cacheSeconds);
   }
 
+  let shouldUpdate = true;
+
   // For the POST request, the above content is set as file contents for the
   // given filename.
   const request = JSON.stringify({
-    files: {[core.getInput('filename')]: {content: JSON.stringify(content)}}
+    files: {[filename]: {content: JSON.stringify(content)}}
   });
+  
+  if (updateIfChanged == 'true') {
+    const getGistOptions = {
+      host: 'api.github.com',
+      path: '/gists/' + core.getInput('gistID'),
+      method: 'GET',
+      headers: {
+        'Content-Type': 'application/json',
+        'User-Agent': 'Schneegans',
+        'Authorization': 'token ' + core.getInput('auth'),
+      }
+    };
+    
+    doRequest(getGistOptions, JSON.stringify({})).then(oldGist => {
+      if (oldGist.statusCode < 200 || oldGist.statusCode >= 400) {
+        // print the error, but don't fail the action
+        console.log(
+          'Failed to get gist, response status code: ' + oldGist.statusCode +
+          ', status message: ' + oldGist.statusMessage);
+      } 
+      
+      if (oldGist && oldGist.body && oldGist.body.files && oldGist.body.files[filename]) {
+        const oldContent = oldGist.body.files[filename].content;
 
-  // Perform the actual request. The user agent is required as defined in
-  // https://developer.github.com/v3/#user-agent-required
-  const req = http.request(
-      {
-        host: 'api.github.com',
-        path: '/gists/' + core.getInput('gistID'),
-        method: 'POST',
-        headers: {
-          'Content-Type': 'application/json',
-          'Content-Length': request.length,
-          'User-Agent': 'Schneegans',
-          'Authorization': 'token ' + core.getInput('auth'),
+        if (oldContent === JSON.stringify(content)) {
+          console.log(`Content did not change, not updating gist at ${filename}`);
+          shouldUpdate = false;
         }
-      },
-      res => {
-        if (res.statusCode < 200 || res.statusCode >= 400) {
-          core.setFailed(
+      }
+
+      if (shouldUpdate) {
+        if (oldGist.body.files[filename]) {
+          console.log(`Content changed, updating gist at ${filename}`);
+        } else {
+          console.log(`Content didn't exist, creating gist at ${filename}`);
+        }
+
+        updatingGist(request).then(res => {
+          if (res.statusCode < 200 || res.statusCode >= 400) {
+            core.setFailed(
               'Failed to create gist, response status code: ' + res.statusCode +
               ', status message: ' + res.statusMessage);
-        } else {
-          console.log('Success!');
-        }
-      });
-
-  req.write(request);
-  req.end();
-
+          } else {
+            console.log('Success!');
+          }
+        });
+      }
+    });
+  } else {
+    updatingGist(request).then(res => {
+      if (res.statusCode < 200 || res.statusCode >= 400) {
+        core.setFailed(
+          'Failed to create gist, response status code: ' + res.statusCode +
+          ', status message: ' + res.statusMessage);
+      } else {
+        console.log('Success!');
+      }
+    });
+  }
 } catch (error) {
   core.setFailed(error);
 }