query - result tabs

packages/api/src/controllers/jsldata.js

@@ -0,0 +1,77 @@
+const _ = require('lodash');
+const path = require('path');
+const fs = require('fs');
+const lineReader = require('line-reader');
+const { jsldir } = require('../utility/directories');
+
+module.exports = {
+  openedReaders: {},
+
+  closeReader(jslid) {
+    if (!this.openedReaders[jslid]) return Promise.resolve();
+    return new Promise((resolve, reject) => {
+      this.openedReaders[jslid].reader.close((err) => {
+        if (err) reject(err);
+        resolve();
+        delete this.openedReaders[jslid];
+      });
+    });
+  },
+
+  readLine(jslid) {
+    if (!this.openedReaders[jslid]) return Promise.reject();
+    return new Promise((resolve, reject) => {
+      const { reader } = this.openedReaders[jslid];
+      if (!reader.hasNextLine()) return Promise.resolve(null);
+      reader.nextLine((err, line) => {
+        this.openedReaders[jslid].readedCount += 1;
+        if (err) reject(err);
+        resolve(line);
+      });
+    });
+  },
+
+  openReader(jslid) {
+    const file = path.join(jsldir(), `${jslid}.jsonl`);
+    return new Promise((resolve, reject) =>
+      lineReader.open(file, function (err, reader) {
+        if (err) reject(err);
+        resolve();
+        this.openedReaders[jslid] = {
+          reader,
+          readedCount: 0,
+        };
+      })
+    );
+  },
+
+  async ensureReader(jslid, offset) {
+    if (this.openedReaders[jslid] && this.openedReaders[jslid].readedCount > offset) {
+      await this.closeReader();
+    }
+    if (!this.openedReaders[jslid]) {
+      await this.openReader();
+    }
+    while (this.openedReaders[jslid].readedCount < offset) {
+      await this.readLine(jslid);
+    }
+  },
+
+  getInfo_meta: 'get',
+  getInfo(jslid) {
+    const file = path.join(jsldir(), `${jslid}.jsonl.info`);
+    return JSON.parse(fs.readFileSync(file, 'utf-8'));
+  },
+
+  getRows_meta: 'get',
+  async getRows(jslid, offset, limit) {
+    await this.ensureReader(jslid, offset);
+    const res = [];
+    for (let i = 0; i < limit; i += 1) {
+      const line = await this.readLine(jslid);
+      if (line == null) break;
+      res.push(JSON.parse(line));
+    }
+    return res;
+  },
+};