// MySQL Client
// -------
var inherits       = require('inherits')
var assign         = require('lodash/object/assign')

var Client         = require('../../client')
var Promise        = require('../../promise')
var helpers        = require('../../helpers')

var Transaction    = require('./transaction')
var QueryCompiler  = require('./query/compiler')
var SchemaCompiler = require('./schema/compiler')
var TableCompiler  = require('./schema/tablecompiler')
var ColumnCompiler = require('./schema/columncompiler')
var pluck          = require('lodash/collection/pluck')

// Always initialize with the "QueryBuilder" and "QueryCompiler"
// objects, which extend the base 'lib/query/builder' and
// 'lib/query/compiler', respectively.
function Client_MySQL(config) {
  Client.call(this, config);
}
inherits(Client_MySQL, Client);

assign(Client_MySQL.prototype, {

  dialect: 'mysql',

  driverName: 'mysql',

  _driver: function() {
    return require('mysql')
  },

  QueryCompiler: QueryCompiler,

  SchemaCompiler: SchemaCompiler,

  TableCompiler: TableCompiler,

  ColumnCompiler: ColumnCompiler,

  Transaction: Transaction,

  wrapIdentifier: function(value) {
    return (value !== '*' ? '`' + value.replace(/`/g, '``') + '`' : '*')
  },

  // Get a raw connection, called by the `pool` whenever a new
  // connection needs to be added to the pool.
  acquireRawConnection: function() {
    var client     = this
    var connection = this.driver.createConnection(this.connectionSettings)
    return new Promise(function(resolver, rejecter) {
      connection.connect(function(err) {
        if (err) return rejecter(err)
        connection.on('error', connectionErrorHandler.bind(null, client, connection))
        connection.on('end', connectionErrorHandler.bind(null, client, connection))
        resolver(connection)
      });
    });
  },

  // Used to explicitly close a connection, called internally by the pool
  // when a connection times out or the pool is shutdown.
  destroyRawConnection: function(connection, cb) {
    connection.end(cb);
  },

  // 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.
  _stream: function(connection, obj, stream, options) {
    options = options || {}
    return new Promise(function(resolver, rejecter) {
      stream.on('error', rejecter)
      stream.on('end', resolver)
      connection.query(obj.sql, obj.bindings).stream(options).pipe(stream)
    })
  },

  // Runs the query on the specified connection, providing the bindings
  // and any other necessary prep work.
  _query: function(connection, obj) {
    if (!obj || typeof obj === 'string') obj = {sql: obj}
    return new Promise(function(resolver, rejecter) {
      var sql = obj.sql
      if (!sql) return resolver()
      if (obj.options) sql = assign({sql: sql}, obj.options)
      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.
  processResponse: function(obj, runner) {
    if (obj == null) return;
    var response = obj.response
    var method   = obj.method
    var rows     = response[0]
    var fields   = response[1]
    if (obj.output) return obj.output.call(runner, 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
    }
  }

})

// MySQL Specific error handler
function connectionErrorHandler(client, connection, err) {
  if (connection && err && err.fatal) {
    if (connection.__knex__disposed) return
    connection.__knex__disposed = true
    client.pool.destroy(connection)
  }
}

module.exports = Client_MySQL