/***********************************************************************************

    Abstractor | MySQL module | MIT License | ©2016 Hexagon <github.com/hexagon>

    Query can be set with <node options>.query OR msg.query OR msg.topic, 
    prioritized in that order.

    Parameters can be set with <node options>.parameters OR msg.parameters.

    {
        topic: "SELECT :mystring as greeting, * FROM table WHERE id = :id",
        parameters: {
            id: 1531512,
            mystring: "Hellu"
        }
    }

    ----------------------------------------------------------------------------


    Dependencies

    mysql


    ----------------------------------------------------------------------------


    Options

    ---------------------+-----------------+----------------------+-----------------
    Option               |  Type           |  Default             |  Mandatory
    ---------------------+-----------------+----------------------+-----------------
    credentials.server   |  string         |  undefined           |  yes
    credentials.database |  string         |  undefined           |  yes
    credentials.user     |  string         |  undefined           |  yes
    credentials.password |  string         |  undefined           |  yes
    query                |  string         |  undefined           |  no
    parameters           |  string         |  undefined           |  no
    ----------------------------------------------------------------------------


    I/O

    -------------------------------+----------------------+---------------------
    Incoming property              |  Possible triggers   |  Sets property
    -------------------------------+----------------------+---------------------
    <any message>                  |  success             |  payload
                                   |                      |  fields
          OR                       +----------------------+---------------------
    topic: <sql string>            |  error               |  error
    -------------------------------+----------------------+---------------------


***********************************************************************************/

"use strict";

const
    Node = require("../node.js"),
    mysql = require("mysql");

class MySQL extends Node {

    invoke(msg) {
        
        let self = this,
            connection; 

        // Sanity checks
        if ( !msg ) { self.trigger( "error", { error: "No message provided." } ); return; }
        if ( !msg.topic && !this.config.query && !msg.query ) { msg.error = "No SQL Query provided, msg.topic should contain query."; self.trigger( "error", msg ); return; }
        if ( !self.config.credentials )  { self.trigger( "error", { error: "No credentials provided, mysql-node config should contain a credentials object." } ); return;   }
        if ( !self.config.credentials.host )  { self.trigger( "error", { error: "No host provided, mysql-node config should contain host." } ); return; }
        if ( !self.config.credentials.user )  { self.trigger( "error", { error: "No user provided, mysql-node config should contain user." } ); return; }
        if ( !self.config.credentials.password )  { self.trigger( "error", { error: "No password provided, mysql-node config should contain password." } ); return; }
        if ( !self.config.credentials.database )  { self.trigger( "error", { error: "No database provided, mysql-node config should contain database." } ); return; }
            
        connection = mysql.createConnection( self.config.credentials );
        
        // Explicitly handle connection, to be able to handle errors
        connection.connect(function(err) {

            if (err) {
                return this.error( msg, "MySQL connection failed, " + err.stack);
            }

            var query = self.config.query || msg.query || msg.topic,
                parameters = self.config.parameters || msg.parameters;

            // So far, so good. Run the query.
            connection.query(query, parameters, function(err, rows, fields) {

                // Instantly request a termination of connection
                connection.end();

                if (err) {
                    return self.error( msg, "MySQL query failed, " + err.stack );
                }

                msg.payload = rows;
                msg.fields = fields;

                self.trigger( "success", msg );

            });

        });


    }

}

module.exports = MySQL;