added plugins

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

@@ -0,0 +1,57 @@
+const xlsx = require('xlsx');
+const stream = require('stream');
+
+const writingWorkbooks = {};
+
+async function saveExcelFiles() {
+  for (const file in writingWorkbooks) {
+    xlsx.writeFile(writingWorkbooks[file], file);
+  }
+}
+
+function createWorkbook(fileName) {
+  let workbook = writingWorkbooks[fileName];
+  if (workbook) return workbook;
+  workbook = xlsx.utils.book_new();
+  writingWorkbooks[fileName] = workbook;
+  return workbook;
+}
+
+class ExcelSheetWriterStream extends stream.Writable {
+  constructor({ fileName, sheetName }) {
+    super({ objectMode: true });
+    this.rows = [];
+    this.structure = null;
+    this.fileName = fileName;
+    this.sheetName = sheetName;
+  }
+  _write(chunk, enc, next) {
+    if (this.structure) {
+      this.rows.push(this.structure.columns.map((col) => chunk[col.columnName]));
+    } else {
+      this.structure = chunk;
+      this.rows.push(chunk.columns.map((x) => x.columnName));
+    }
+
+    next();
+  }
+
+  _final(callback) {
+    const workbook = createWorkbook(this.fileName);
+    xlsx.utils.book_append_sheet(workbook, xlsx.utils.aoa_to_sheet(this.rows), this.sheetName || 'Sheet 1');
+    callback();
+  }
+}
+
+async function writer({ fileName, sheetName }) {
+  return new ExcelSheetWriterStream({
+    fileName,
+    sheetName,
+  });
+}
+
+writer.initialize = ({ dbgateApi }) => {
+  dbgateApi.finalizer.register(saveExcelFiles);
+};
+
+module.exports = writer;