JSON array export file format, quick exports JSON, JSONL

packages/api/src/shell/jsonArrayWriter.js

@@ -0,0 +1,51 @@
+const fs = require('fs');
+const stream = require('stream');
+
+class StringifyStream extends stream.Transform {
+  constructor() {
+    super({ objectMode: true });
+    this.wasHeader = false;
+    this.wasRecord = false;
+  }
+  _transform(chunk, encoding, done) {
+    let skip = false;
+
+    if (!this.wasHeader) {
+      skip =
+        chunk.__isStreamHeader ||
+        // TODO remove isArray test
+        Array.isArray(chunk.columns);
+      this.wasHeader = true;
+    }
+    if (!skip) {
+      if (!this.wasRecord) {
+        this.push('[\n');
+      } else {
+        this.push(',\n');
+      }
+      this.wasRecord = true;
+
+      this.push(JSON.stringify(chunk));
+    }
+    done();
+  }
+
+  _flush() {
+    if (!this.wasRecord) {
+      this.push('[]\n');
+    } else {
+      this.push('\n]\n');
+    }
+  }
+}
+
+async function jsonArrayWriter({ fileName, encoding = 'utf-8' }) {
+  console.log(`Writing file ${fileName}`);
+  const stringify = new StringifyStream();
+  const fileStream = fs.createWriteStream(fileName, encoding);
+  stringify.pipe(fileStream);
+  stringify['finisher'] = fileStream;
+  return stringify;
+}
+
+module.exports = jsonArrayWriter;