added plugins

plugins/dbgate-plugin-csv/src/backend/writer.js

@@ -0,0 +1,36 @@
+const csv = require('csv');
+const fs = require('fs');
+const stream = require('stream');
+
+class CsvPrepareStream extends stream.Transform {
+  constructor({ header }) {
+    super({ objectMode: true });
+    this.structure = null;
+    this.header = header;
+  }
+  _transform(chunk, encoding, done) {
+    if (this.structure) {
+      this.push(this.structure.columns.map((col) => chunk[col.columnName]));
+      done();
+    } else {
+      this.structure = chunk;
+      if (this.header) {
+        this.push(chunk.columns.map((x) => x.columnName));
+      }
+      done();
+    }
+  }
+}
+
+async function writer({ fileName, encoding = 'utf-8', header = true, delimiter, quoted }) {
+  console.log(`Writing file ${fileName}`);
+  const csvPrepare = new CsvPrepareStream({ header });
+  const csvStream = csv.stringify({ delimiter, quoted });
+  const fileStream = fs.createWriteStream(fileName, encoding);
+  csvPrepare.pipe(csvStream);
+  csvStream.pipe(fileStream);
+  csvPrepare['finisher'] = fileStream;
+  return csvPrepare;
+}
+
+module.exports = writer;