added plugins

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

@@ -0,0 +1,67 @@
+const zipObject = require('lodash/zipObject');
+const csv = require('csv');
+const fs = require('fs');
+const stream = require('stream');
+
+let dbgateApi;
+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(
+        zipObject(
+          this.structure.columns.map((x) => x.columnName),
+          chunk
+        )
+      );
+      done();
+    } else {
+      if (this.header) {
+        this.structure = {
+          __isStreamHeader: true,
+          columns: chunk.map((columnName) => ({ columnName })),
+        };
+        this.push(this.structure);
+      } else {
+        this.structure = {
+          __isStreamHeader: true,
+          columns: chunk.map((value, index) => ({ columnName: `col${index + 1}` })),
+        };
+        this.push(this.structure);
+        this.push(
+          zipObject(
+            this.structure.columns.map((x) => x.columnName),
+            chunk
+          )
+        );
+      }
+      done();
+    }
+  }
+}
+
+async function reader({ fileName, encoding = 'utf-8', header = true, delimiter, limitRows = undefined }) {
+  console.log(`Reading file ${fileName}`);
+  const csvStream = csv.parse({
+    // @ts-ignore
+    delimiter,
+    skip_lines_with_error: true,
+    to_line: limitRows ? limitRows + 1 : undefined,
+  });
+  const downloadedFile = await dbgateApi.download(fileName);
+  const fileStream = fs.createReadStream(downloadedFile, encoding);
+  const csvPrepare = new CsvPrepareStream({ header });
+  fileStream.pipe(csvStream);
+  csvStream.pipe(csvPrepare);
+  return csvPrepare;
+}
+
+reader.initialize = (dbgateEnv) => {
+  dbgateApi = dbgateEnv.dbgateApi;
+};
+
+module.exports = reader;