Rename File.js to file.js and make changes to the parse method to read a file and return a stream

src/models/File.js → src/file.js

@@ -112,6 +112,61 @@ class File extends EventEmitter {
       });
     });
   }
+
+
+  // create a parse method which read the file and return a stream
+  async parse(columns) {
+    const stream = new PassThrough();
+
+    // check if columns is valid
+    if (!columns || columns.length) {
+      return Promise.reject(new Error('Invalid columns'));
+    }
+
+    // Create a variable to hold csv columns indexes
+    const indexes = [];
+
+    let i = 0;
+    fs.createReadStream(this.filepath)
+    .pipe(csvParser({ separator: ';' }))
+    .on('headers', (headers) => {
+      // Emit a parse.start event with the url and filepath
+      this.emit('parse.start', { url: this.url, filepath: this.filepath, headers });
+    })
+    .on('data', (data) => {
+      // Emit a parse.data event with the url, filepath and data
+      this.emit('parse.data', { url: this.url, filepath: this.filepath, data });
+
+      if ( i === 0 ) {
+        // Loop through columns and push the index of the column to indexes
+        columns.forEach((column) => {
+          indexes.push(headers.indexOf(column));
+        });
+      } else {
+        // Loop through indexes and push the value of the column to result
+        const result = this.processRow(data, columns, indexes);
+        stream.write(result.join(';'));
+      }
+      i++;
+    })
+    .on('error', (err) => {
+      // Emit a parse.error event with the error
+      this.emit('parse.error', { url: this.url, filepath: this.filepath, error: err.message });
+    })
+    .on('end', () => {
+      // Emit a parse.end event with the url and filepath
+      this.emit('parse.end', { url: this.url, filepath: this.filepath });
+      stream.end();
+    });
+
+    return stream;
+  }
+
+  processRow(data, columns, columnsIndex) {
+    const result = [];
+
+    return result;
+  }
 }
 
 module.exports = File;