const fs = require('fs');
const lineReader = require('line-reader');
const _ = require('lodash');
const DatastoreProxy = require('../utility/DatastoreProxy');
const { saveFreeTableData } = require('../utility/freeTableStorage');
const getJslFileName = require('../utility/getJslFileName');
const JsonLinesDatastore = require('../utility/JsonLinesDatastore');
const socket = require('../utility/socket');

function readFirstLine(file) {
  return new Promise((resolve, reject) => {
    lineReader.open(file, (err, reader) => {
      if (err) reject(err);
      if (reader.hasNextLine()) {
        reader.nextLine((err, line) => {
          if (err) reject(err);
          resolve(line);
        });
      } else {
        resolve(null);
      }
    });
  });
}

module.exports = {
  datastores: {},

  // closeReader(jslid) {
  //   // console.log('CLOSING READER');
  //   if (!this.openedReaders[jslid]) return Promise.resolve();
  //   return new Promise((resolve, reject) => {
  //     this.openedReaders[jslid].reader.close((err) => {
  //       if (err) reject(err);
  //       delete this.openedReaders[jslid];
  //       resolve();
  //     });
  //   });
  // },

  // readLine(readerInfo) {
  //   return new Promise((resolve, reject) => {
  //     const { reader } = readerInfo;
  //     if (!reader.hasNextLine()) {
  //       resolve(null);
  //       return;
  //     }
  //     reader.nextLine((err, line) => {
  //       if (readerInfo.readedSchemaRow) readerInfo.readedDataRowCount += 1;
  //       else readerInfo.readedSchemaRow = true;
  //       if (err) reject(err);
  //       resolve(line);
  //     });
  //   });
  // },

  // openReader(jslid) {
  //   // console.log('OPENING READER');
  //   // console.log(
  //   //   'OPENING READER, LINES=',
  //   //   fs.readFileSync(path.join(jsldir(), `${jslid}.jsonl`), 'utf-8').split('\n').length
  //   // );
  //   const file = getJslFileName(jslid);
  //   return new Promise((resolve, reject) =>
  //     lineReader.open(file, (err, reader) => {
  //       if (err) reject(err);
  //       const readerInfo = {
  //         reader,
  //         readedDataRowCount: 0,
  //         readedSchemaRow: false,
  //         isReading: true,
  //       };
  //       this.openedReaders[jslid] = readerInfo;
  //       resolve(readerInfo);
  //     })
  //   );
  // },

  // async ensureReader(jslid, offset) {
  //   if (this.openedReaders[jslid] && this.openedReaders[jslid].readedDataRowCount > offset) {
  //     await this.closeReader(jslid);
  //   }
  //   let readerInfo = this.openedReaders[jslid];
  //   if (!this.openedReaders[jslid]) {
  //     readerInfo = await this.openReader(jslid);
  //   }
  //   readerInfo.isReading = true;
  //   if (!readerInfo.readedSchemaRow) {
  //     await this.readLine(readerInfo); // skip structure
  //   }
  //   while (readerInfo.readedDataRowCount < offset) {
  //     await this.readLine(readerInfo);
  //   }
  //   return readerInfo;
  // },

  async ensureDatastore(jslid) {
    let datastore = this.datastores[jslid];
    if (!datastore) {
      datastore = new JsonLinesDatastore(getJslFileName(jslid));
      // datastore = new DatastoreProxy(getJslFileName(jslid));
      this.datastores[jslid] = datastore;
    }
    return datastore;
  },

  getInfo_meta: 'get',
  async getInfo({ jslid }) {
    const file = getJslFileName(jslid);
    const firstLine = await readFirstLine(file);
    if (firstLine) return JSON.parse(firstLine);
    return null;
  },

  getRows_meta: 'post',
  async getRows({ jslid, offset, limit, filters }) {
    const datastore = await this.ensureDatastore(jslid);
    return datastore.getRows(offset, limit, _.isEmpty(filters) ? null : filters);
  },

  getStats_meta: 'get',
  getStats({ jslid }) {
    const file = `${getJslFileName(jslid)}.stats`;
    if (fs.existsSync(file)) return JSON.parse(fs.readFileSync(file, 'utf-8'));
    return {};
  },

  async notifyChangedStats(stats) {
    console.log('SENDING STATS', JSON.stringify(stats));
    const datastore = this.datastores[stats.jslid];
    if (datastore) await datastore.notifyChanged();
    socket.emit(`jsldata-stats-${stats.jslid}`, stats);

    // const readerInfo = this.openedReaders[stats.jslid];
    // if (readerInfo && readerInfo.isReading) {
    //   readerInfo.closeAfterReadAndSendStats = stats;
    // } else {
    //   await this.closeReader(stats.jslid);
    //   socket.emit(`jsldata-stats-${stats.jslid}`, stats);
    // }
  },

  saveFreeTable_meta: 'post',
  async saveFreeTable({ jslid, data }) {
    saveFreeTableData(getJslFileName(jslid), data);
    return true;
  },
};