Switch to google cloud vision for OCR

Also separate text recognition code into a function

@@ -17,8 +17,9 @@ const languagedetect_api_url = 'https://openapi.naver.com/v1/papago/detectLangs'
 const db = require('./db');
 db.init();
 
-// Tesseract module for image recognition
-const tesseract = require('node-tesseract-ocr');
+// Import Google Cloud client library and create a client
+const vision = require('@google-cloud/vision');
+const visionClient = new vision.ImageAnnotatorClient(config.gcloud);
 
 // fs module for saving/removing image file upon/after recognition
 const fs = require('fs');
@@ -136,6 +137,50 @@ function translate(user, message) {
   });
 }
 
+/**
+ * Detect and read text from an image file using Google Cloud Vision API.
+ *
+ * @param {*} fileId Telegram-provided file id of image to read text from
+ */
+function detectText(fileId) {
+  return new Promise(function (resolve, reject) {
+    // Download the image, which will later be deleted to avoid git detection
+    bot.downloadFile(fileId, '.').then(function (filePath) {
+      console.log('Image downloaded: ', filePath);
+
+      visionClient.documentTextDetection(filePath)
+        .then(function (result) {
+          const fullTextAnnotation = result[0].fullTextAnnotation;
+          const text = fullTextAnnotation.text;
+
+          console.log('Text detection result: ', text);
+
+          resolve(text);
+          // Delete the image
+          fs.unlink(filePath, function (error) {
+            if (error) {
+              console.log('Error deleting image: ', error);
+            } else {
+              console.log('Successfully deleted file ', filePath);
+            }
+          });
+        }).catch(function (error) {
+          console.log(error);
+
+          reject(error);
+          // Delete the image
+          fs.unlink(filePath, function (error) {
+            if (error) {
+              console.log('Error deleting image: ', error);
+            } else {
+              console.log('Successfully deleted file ', filePath);
+            }
+          });
+        });
+    });
+  });
+}
+
 // [Any normal message which is not a command (not starting with '/')]
 bot.onText(/^(?!\/)((.|\n)+)/, (msg, match) => {
   const user = msg.from;
@@ -199,43 +244,16 @@ bot.on('photo', (msg) => {
   const photo = msg.photo[msg.photo.length - 1]; // Choose largest image possible
   const photoId = photo.file_id;
 
-  // Download the image, which will later be deleted to avoid git detection
-  bot.downloadFile(photoId, '.').then(function (filePath) {
-    console.log('Image downloaded: ', filePath);
-
-    // Begin tesseract OCR
-    tesseract.recognize(filePath).then(function (text) {
-      console.log('OCR result: ', text);
-
+  // Detect text from given image
+  detectText(photoId).then(function (text) {
     // Translate the result
     translate(user, text).then(function (result) {
       // Send recognized text to user
       bot.sendMessage(chatId, result);
-        // Delete the image
-        fs.unlink(filePath, function (error) {
-          if (error) {
-            console.log('Error deleting image: ', error);
-          } else {
-            console.log('Successfully deleted file ', filePath);
-          }
-        });
-      });
-    }).catch(function (error) {
-      // OCR failed
-      console.log('OCR error: ', error);
-
-      // Delete the image
-      fs.unlink(filePath, function (error) {
-        if (error) {
-          console.log('Error deleting image: ', error);
-        } else {
-          console.log('Successfully deleted file ', filePath);
-        }
-      });
     });
   }).catch(function (error) {
-    // Image download failed
-    console.log('Image download error: ', error);
+    // Text detection failed
+    console.log('Text detection error: ', error);
   });
 });
 

@@ -10,5 +10,9 @@ module.exports = {
         // https://developers.naver.com/apps/#/register
         client_id: 'XXXXXXXXXXXXXXXXXXXX',
         client_secret: 'XXXXXXXXXX'
+    },
+    gcloud: {
+        projectId: 'your_project_name',
+        keyFilename: '/path/to/your/keyfile.json'
     }
 }

@@ -10,9 +10,9 @@
   "author": "강수인",
   "license": "MIT",
   "dependencies": {
+    "@google-cloud/vision": "^1.0.0",
     "mongodb": "^3.2.6",
     "node-telegram-bot-api": "^0.30.0",
-    "node-tesseract-ocr": "^0.1.0",
     "request": "^2.88.0"
   }
 }