/*
   Copyright 2017-2021 Norman Breau

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

import {Database} from './Database';
import {MySQLConnection} from './MySQLConnection';
import * as MySQL from 'mysql2';
import {getInstance} from './instance';
import { IDatabasePosition } from './IDatabasePosition';
import { ConnectionReplicationWaiter } from './private/ConnectionReplicationWaiter';
import { ILogger } from '@arashi/interfaces';
import { MetricStore } from './MetricStore';

const TAG: string = 'MySQLDatabase';

export class MySQLDatabase extends Database<MySQL.PoolOptions, MySQL.PoolConnection> {
    private $cluster: MySQL.PoolCluster;

    constructor() {
        super();
        // TODO: Maybe one day this may be exposed via a bt config setting.
        this.$cluster = MySQL.createPoolCluster({
            removeNodeErrorCount: Infinity,
            restoreNodeTimeout: 1000
        });
        this.$cluster.on('enqueue', () => {
            getInstance().getLogger().warn(TAG, 'Waiting for available connection...');
        });
    }

    public escape(value: any): string {
        return MySQLDatabase.escape(value);
    }

    public static escape(value: any): string {
        return MySQL.escape(value);
    }

    protected _addNode(nodeID: string, config: MySQL.PoolOptions): void {
        getInstance().getLogger().trace(TAG, `Adding node to connection pool: "${nodeID}"`);
        this.$cluster.add(nodeID, config);
    }

    protected _removeNode(nodeID: string): void {
        getInstance().getLogger().trace(TAG, `Removing node to connection pool: "${nodeID}"`);
        this.$cluster.remove(nodeID);
    }

    protected async _destroy(): Promise<void> {
        this.$cluster.end();
    }

    private $getConnectionFromPool(query: string, requireWriteAccess: boolean, instantationStack: string): Promise<MySQLConnection> {
        return new Promise<MySQLConnection>((resolve, reject) => {
            this.$cluster.getConnection(query, (error: MySQL.QueryError, connection: MySQL.PoolConnection) => {
                if (error) {
                    reject(error);
                    return;
                }
    
                MetricStore.getInstance().increment('mysql.active_connections');
                resolve(new MySQLConnection(connection, instantationStack, !requireWriteAccess));
            });
        });
    }

    protected override async _getConnection(query: string, requireWriteAccess: boolean, position?: IDatabasePosition): Promise<MySQLConnection> {
        let logger: ILogger = getInstance().getLogger();
        logger.trace(TAG, `Querying connection pool for "${query}".`);
        let instantationStack: string = new Error().stack;

        let conn: MySQLConnection = await this.$getConnectionFromPool(query, requireWriteAccess, instantationStack);
        await conn.__internal_init();

        logger.trace(TAG, `Replication Enabled: ${conn.hasReplicationEnabled() ? 'true' : 'false'}`);
        logger.trace(TAG, `Connection Replicating: ${conn.isReplication() ? 'true' : 'false'}`);

        if (conn.hasReplicationEnabled() && conn.isReplication() && position && position.page && position.position) {
            logger.trace(TAG, 'Connection is waiting on Replication');
            // master connections will not wait on database positions
            // they are guarenteed to be at the tip.
            // readonly, or otherwise known as replication connections
            // may have replication lag. If we have a desired position target,
            // then await for the connection to catch up to that target.
            let waiter: ConnectionReplicationWaiter = new ConnectionReplicationWaiter(conn);
            try {
                await waiter.wait(position);
            }
            catch (ex) {
                void conn.close(true);
                throw ex;
            }
        }

        return conn;
    }
}