const ZongJi = require('./zongji');
const mysql = require('mysql2/promise');
const amqp = require('amqplib');
require('colors');

const allEvents = new Set([
    'writerows',
    'updaterows',
    'deleterows'
  ]);

module.exports = class MyCDC {
  constructor(config) {
    this.config = config;
    this.running = false;
    this.filename = null;
    this.position = null;
    this.schemaMap = new Map();
    this.fks = new Set();

    const includeSchema = {};
    for (const schemaName in this.config.includeSchema) {
      const schema = this.config.includeSchema[schemaName];
      const tables = [];
      const tableMap = new Map();
  
      for (const tableName in schema) {
        const table = schema[tableName];
        tables.push(tableName);
  
        const tableInfo = {
          events: allEvents,
          columns: true,
          fk: 'id'
        };
        tableMap.set(tableName, tableInfo);
    
        if (typeof table === 'object') {
          if (Array.isArray(table.events))
            tableInfo.events = new Set(table.events);
          if (Array.isArray(table.columns))
            tableInfo.columns = new Set(table.columns);
          if (table.fk)
            tableInfo.fk = table.fk;
        }
      }
  
      includeSchema[schemaName] = tables;
      this.schemaMap.set(schemaName, tableMap);
    }
  
    this.opts = {
      includeEvents: this.config.includeEvents,
      includeSchema
    };
  }

  async start() {
    if (this.config.testMode)
      console.log('Test mode enabled, just logging queries to console.');

    console.log('Starting process.');
    await this.init();
    console.log('Process started.');
  }

  async stop() {
    console.log('Stopping process.');
    await this.end();
    console.log('Process stopped.');
  }

  async init() {
    this.debug('DbAsync', 'Initializing.');
    this.onErrorListener = err => this.onError(err);

    // DB connection

    this.db = await mysql.createConnection(this.config.db);
    this.db.on('error', this.onErrorListener);

    // RabbitMQ

    this.publisher = await amqp.connect(this.config.amqp);
    this.channel = await this.publisher.createChannel();
    this.channel.assertQueue(this.config.queue, {
      durable: true
    });

    // Zongji

    const zongji = new ZongJi(this.config.db);
    this.zongji = zongji;

    this.onBinlogListener = evt => this.onBinlog(evt);
    zongji.on('binlog', this.onBinlogListener);

    const [res] = await this.db.query(
      'SELECT `logName`, `position` FROM `binlogQueue` WHERE code = ?',
      [this.config.queue]
    );
    if (res.length) {
      const [row] = res;
      this.filename = row.logName;
      this.position = row.position;
      Object.assign(this.opts, {
        filename: this.filename,
        position: this.position
      });
    } else
      this.opts.startAtEnd = true;

    this.debug('Zongji', 'Starting.');
    await new Promise((resolve, reject) => {
      const onReady = () => {
        zongji.off('error', onError);
        resolve();
      };
      const onError = err => {
        this.zongji = null;
        zongji.off('ready', onReady);
        zongji.off('binlog', this.onBinlogListener);
        reject(err);
      }

      zongji.once('ready', onReady);
      zongji.once('error',  onError);
      zongji.start(this.opts);
    });
    this.debug('Zongji', 'Started.');

    this.zongji.on('error', this.onErrorListener);

    this.flushInterval = setInterval(
      () => this.flushQueue(), this.config.flushInterval);
    this.pingInterval = setInterval(
      () => this.connectionPing(), this.config.pingInterval * 1000);

    // Summary

    this.running = true;
    this.debug('DbAsync', 'Initialized.');
  }

  async end(silent) {
    const zongji = this.zongji;
    if (!zongji) return;

    this.debug('DbAsync', 'Ending.');

    // Zongji

    clearInterval(this.flushInterval);
    clearInterval(this.pingInterval);
    zongji.off('binlog', this.onBinlogListener);
    zongji.off('error', this.onErrorListener);
    this.zongji = null;
    this.running = false;

    this.debug('Zongji', 'Stopping.');
    // FIXME: Cannot call Zongji.stop(), it doesn't wait to end connection
    zongji.connection.destroy(() => {
      console.log('zongji.connection.destroy');
    });
    await new Promise(resolve => {
      zongji.ctrlConnection.query('KILL ' + zongji.connection.threadId,
      err => {
        if (err && !silent)
          console.error(err);
        resolve();
      });
    });
    zongji.ctrlConnection.destroy(() => {
      console.log('zongji.ctrlConnection.destroy');
    });
    zongji.emit('stopped');
    this.debug('Zongji', 'Stopped.');

    // RabbitMQ

    await this.publisher.close();

    // DB connection

    this.db.off('error', this.onErrorListener);
    // FIXME: mysql2/promise bug, db.end() ends process
    this.db.on('error', () => {});
    try {
      await this.db.end();
    } catch (err) {
      if (!silent)
        console.error(err);
    }

    // Summary

    this.debug('DbAsync', 'Ended.');
  }

  async tryRestart() {
    try {
      await this.init();
      console.log('Process restarted.');
    } catch(err) {
      setTimeout(() => this.tryRestart(), 30);
    }
  }

  async onError(err) {
    console.log(`Error: ${err.code}: ${err.message}`);
    try {
      await this.end(true);
    } catch(e) {}

    switch (err.code) {
      case 'PROTOCOL_CONNECTION_LOST':
      case 'ECONNRESET':
      console.log('Trying to restart process.');
      await this.tryRestart();
      break;
    default:
      process.exit();
    }
  }

  onBinlog(evt) {
    //evt.dump();
    const eventName = evt.getEventName();
    if (eventName === 'tablemap') return;

    if (eventName === 'rotate') {
      this.filename = evt.binlogName;
      this.position = evt.position;
      console.log(`[${eventName}] filename: ${this.filename}`, `position: ${this.position}`);
      return;
    }

    const table = evt.tableMap[evt.tableId];
    const tableMap = this.schemaMap.get(table.parentSchema);
    if (!tableMap) return;

    const tableInfo = tableMap.get(table.tableName);
    if (!tableInfo) return;

    if (!tableInfo.events.has(eventName)) return;

    let column;
    const rows = evt.rows;

    const fks = new Set();

    if (eventName === 'updaterows') {
      if (tableInfo.columns !== true) {
        let changes = false;
        for (const row of rows) {
          const after = row.after;
          for (const col in after) {
            if (tableInfo.columns.has(col) && !equals(after[col], row.before[col])) {
              fks.add(after[tableInfo.fk]);
              changes = true;
              if (!column) column = col;
              break;
            }
          }
        }
        if (!changes) return;
      } else {
        for (const row of rows)
          fks.add(row.after[tableInfo.fk]);
      }
    } else {
      for (const row of rows)
        fks.add(row[tableInfo.fk]);
    }

    if (fks.size) {
      const data = JSON.stringify(Array.from(fks));
      this.channel.sendToQueue(this.config.queue,
        Buffer.from(data));
      this.debug('Queued', data);
    }

    const row = eventName === 'updaterows'
      ? rows[0].after
      : rows[0];

    if (this.config.debug) {
      console.debug(`[${eventName}] ${table.tableName}: ${rows.length}`);
      console.debug(`  ${tableInfo.fk}: ${row[tableInfo.fk]}`);
      if (column) {
        let before = formatValue(rows[0].before[column]);
        let after = formatValue(rows[0].after[column]);
        console.debug(`  ${column}: ${before} <- ${after}`);
      }
    }

    this.position = evt.nextPosition;
    this.flushed = false;
  }

  async flushQueue() {
    if (this.flushed) return;
    this.debug('Flush', `filename: ${this.filename}, position: ${this.position}`);
  
    const replaceQuery =
      'REPLACE INTO `binlogQueue`  SET `code` = ?, `logName` = ?, `position` = ?';
    if (!this.config.testMode)
      await this.db.query(replaceQuery, [this.config.queue, this.filename, this.position]);

    this.flushed = true;
  }

  async connectionPing() {
    this.debug('Ping', 'Sending ping to database.');

    // FIXME: Should Zongji.connection be pinged?
    await new Promise((resolve, reject) => {
      this.zongji.ctrlConnection.ping(err => {
        if (err) return reject(err);
        resolve();
      });
    })
    await this.db.ping();
  }

  debug(namespace, message) {
    if (this.config.debug)
      console.debug(`${namespace}:`.blue, message.yellow);
  }
}

function equals(a, b) {
  if (a === b)
    return true;
  const type = typeof a;
  if (a == null || b == null || type !== typeof b)
    return false;
  if (type === 'object' && a.constructor === b.constructor) {
    if (a instanceof Date)
      return a.getTime() === b.getTime();
  }
  return false;
}

function formatValue(value) {
  if (value instanceof Date)
    return value.toJSON();
  return value;
}