'use strict';

// MySQL Runner
// ------
var _        = require('lodash')
var inherits = require('inherits')

var Promise  = require('../../promise')
var Runner   = require('../../runner')
var helpers  = require('../../helpers')

// Inherit from the `Runner` constructor's prototype,
// so we can add the correct `then` method.
function Runner_MySQL(client, connection) {
  Runner.call(this, client, connection)
}
inherits(Runner_MySQL, Runner)

// Grab a connection, run the query via the MySQL streaming interface,
// and pass that through to the stream we've sent back to the client.
Runner_MySQL.prototype._stream = function(sql, stream, options) {
  var runner = this
  return new Promise(function(resolver, rejecter) {
    stream.on('error', rejecter)
    stream.on('end', resolver)
    runner.connection.query(sql.sql, sql.bindings).stream(options).pipe(stream)
  })
}

// Runs the query on the specified connection, providing the bindings
// and any other necessary prep work.
Runner_MySQL.prototype._query = Promise.method(function(obj) {
  var sql = obj.sql
  if (obj.options) sql = _.extend({sql: sql}, obj.options)
  var connection = this.connection
  if (!sql) throw new Error('The query is empty')
  return new Promise(function(resolver, rejecter) {
    connection.query(sql, obj.bindings, function(err, rows, fields) {
      if (err) return rejecter(err)
      obj.response = [rows, fields]
      resolver(obj)
    })
  })
})

// Process the response as returned from the query.
Runner_MySQL.prototype.processResponse = function(obj) {
  var response = obj.response
  var method   = obj.method
  var rows     = response[0]
  var fields   = response[1]
  if (obj.output) return obj.output.call(this, rows, fields)
  switch (method) {
    case 'select':
    case 'pluck':
    case 'first':
      var resp = helpers.skim(rows)
      if (method === 'pluck') return _.pluck(resp, obj.pluck)
      return method === 'first' ? resp[0] : resp
    case 'insert':
      return [rows.insertId]
    case 'del':
    case 'update':
    case 'counter':
      return rows.affectedRows
    default:
      return response
  }
}

module.exports = Runner_MySQL