// Go MySQL Driver - A MySQL-Driver for Go's database/sql package
//
// Copyright 2012 The Go-MySQL-Driver Authors. All rights reserved.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.

package driver

import (
	"context"
	"database/sql/driver"
	"net"
	"strconv"
	"strings"
	"time"
)

type mysqlConn struct {
	buf              buffer
	netConn          net.Conn
	affectedRows     uint64
	insertID         uint64
	cfg              *Config
	maxAllowedPacket int
	maxWriteSize     int
	writeTimeout     time.Duration
	flags            clientFlag
	status           statusFlag
	sequence         uint8
	parseTime        bool

	// for context support (Go 1.8+)
	watching bool
	watcher  chan<- context.Context
	closech  chan struct{}
	finished chan<- struct{}
	canceled atomicError // set non-nil if conn is canceled
	closed   atomicBool  // set when conn is closed, before closech is closed
}

func newConnection(dsn string) (*mysqlConn, error) {
	var err error

	// New mysqlConn
	mc := &mysqlConn{
		maxAllowedPacket: maxPacketSize,
		maxWriteSize:     maxPacketSize - 1,
		closech:          make(chan struct{}),
	}
	mc.cfg, err = ParseDSN(dsn)
	if err != nil {
		return nil, err
	}
	mc.parseTime = mc.cfg.ParseTime

	// Connect to Server
	nd := net.Dialer{Timeout: mc.cfg.Timeout}
	mc.netConn, err = nd.Dial(mc.cfg.Net, mc.cfg.Addr)
	if err != nil {
		return nil, err
	}

	// Enable TCP Keepalives on TCP connections
	if tc, ok := mc.netConn.(*net.TCPConn); ok {
		if err := tc.SetKeepAlive(true); err != nil {
			// Don't send COM_QUIT before handshake.
			mc.netConn.Close()
			mc.netConn = nil
			return nil, err
		}
	}

	// Call startWatcher for context support (From Go 1.8)
	mc.startWatcher()

	mc.buf = newBuffer(mc.netConn)

	// Set I/O timeouts
	mc.buf.timeout = mc.cfg.ReadTimeout
	mc.writeTimeout = mc.cfg.WriteTimeout

	// Reading Handshake Initialization Packet
	authData, plugin, err := mc.readHandshakePacket()
	if err != nil {
		mc.cleanup()
		return nil, err
	}

	// Send Client Authentication Packet
	authResp, addNUL, err := mc.auth(authData, plugin)
	if err != nil {
		// try the default auth plugin, if using the requested plugin failed
		errLog.Print("could not use requested auth plugin '"+plugin+"': ", err.Error())
		plugin = defaultAuthPlugin
		authResp, addNUL, err = mc.auth(authData, plugin)
		if err != nil {
			mc.cleanup()
			return nil, err
		}
	}
	if err = mc.writeHandshakeResponsePacket(authResp, addNUL, plugin); err != nil {
		mc.cleanup()
		return nil, err
	}

	// Handle response to auth packet, switch methods if possible
	if err = mc.handleAuthResult(authData, plugin); err != nil {
		// Authentication failed and MySQL has already closed the connection
		// (https://dev.mysql.com/doc/internals/en/authentication-fails.html).
		// Do not send COM_QUIT, just cleanup and return the error.
		mc.cleanup()
		return nil, err
	}

	if mc.cfg.MaxAllowedPacket > 0 {
		mc.maxAllowedPacket = mc.cfg.MaxAllowedPacket
	} else {
		// Get max allowed packet size
		maxap, err := mc.getSystemVar("max_allowed_packet")
		if err != nil {
			mc.Close()
			return nil, err
		}
		mc.maxAllowedPacket = stringToInt(maxap) - 1
	}
	if mc.maxAllowedPacket < maxPacketSize {
		mc.maxWriteSize = mc.maxAllowedPacket
	}

	// Handle DSN Params
	err = mc.handleParams()
	if err != nil {
		mc.Close()
		return nil, err
	}

	return mc, nil
}

// Handles parameters set in DSN after the connection is established
func (mc *mysqlConn) handleParams() (err error) {
	for param, val := range mc.cfg.Params {
		switch param {
		// Charset
		case "charset":
			charsets := strings.Split(val, ",")
			for i := range charsets {
				// ignore errors here - a charset may not exist
				err = mc.exec("SET NAMES " + charsets[i])
				if err == nil {
					break
				}
			}
			if err != nil {
				return
			}

		// System Vars
		default:
			err = mc.exec("SET " + param + "=" + val)
			if err != nil {
				return
			}
		}
	}

	return
}

func (mc *mysqlConn) markBadConn(err error) error {
	if mc == nil {
		return err
	}
	if err != errBadConnNoWrite {
		return err
	}
	return driver.ErrBadConn
}

func (mc *mysqlConn) Close() (err error) {
	// Makes Close idempotent
	if !mc.closed.IsSet() {
		err = mc.writeCommandPacket(comQuit)
	}

	mc.cleanup()

	return
}

// Closes the network connection and unsets internal variables. Do not call this
// function after successfully authentication, call Close instead. This function
// is called before auth or on auth failure because MySQL will have already
// closed the network connection.
func (mc *mysqlConn) cleanup() {
	if !mc.closed.TrySet(true) {
		return
	}

	// Makes cleanup idempotent
	close(mc.closech)
	if mc.netConn == nil {
		return
	}
	if err := mc.netConn.Close(); err != nil {
		errLog.Print(err)
	}
}

func (mc *mysqlConn) error() error {
	if mc.closed.IsSet() {
		if err := mc.canceled.Value(); err != nil {
			return err
		}
		return ErrInvalidConn
	}
	return nil
}

func (mc *mysqlConn) interpolateParams(query string, args []driver.Value) (string, error) {
	// Number of ? should be same to len(args)
	if strings.Count(query, "?") != len(args) {
		return "", driver.ErrSkip
	}

	buf := mc.buf.takeCompleteBuffer()
	if buf == nil {
		// can not take the buffer. Something must be wrong with the connection
		errLog.Print(ErrBusyBuffer)
		return "", ErrInvalidConn
	}
	buf = buf[:0]
	argPos := 0

	for i := 0; i < len(query); i++ {
		q := strings.IndexByte(query[i:], '?')
		if q == -1 {
			buf = append(buf, query[i:]...)
			break
		}
		buf = append(buf, query[i:i+q]...)
		i += q

		arg := args[argPos]
		argPos++

		if arg == nil {
			buf = append(buf, "NULL"...)
			continue
		}

		switch v := arg.(type) {
		case int64:
			buf = strconv.AppendInt(buf, v, 10)
		case float64:
			buf = strconv.AppendFloat(buf, v, 'g', -1, 64)
		case bool:
			if v {
				buf = append(buf, '1')
			} else {
				buf = append(buf, '0')
			}
		case time.Time:
			if v.IsZero() {
				buf = append(buf, "'0000-00-00'"...)
			} else {
				v := v.In(mc.cfg.Loc)
				v = v.Add(time.Nanosecond * 500) // To round under microsecond
				year := v.Year()
				year100 := year / 100
				year1 := year % 100
				month := v.Month()
				day := v.Day()
				hour := v.Hour()
				minute := v.Minute()
				second := v.Second()
				micro := v.Nanosecond() / 1000

				buf = append(buf, []byte{
					'\'',
					digits10[year100], digits01[year100],
					digits10[year1], digits01[year1],
					'-',
					digits10[month], digits01[month],
					'-',
					digits10[day], digits01[day],
					' ',
					digits10[hour], digits01[hour],
					':',
					digits10[minute], digits01[minute],
					':',
					digits10[second], digits01[second],
				}...)

				if micro != 0 {
					micro10000 := micro / 10000
					micro100 := micro / 100 % 100
					micro1 := micro % 100
					buf = append(buf, []byte{
						'.',
						digits10[micro10000], digits01[micro10000],
						digits10[micro100], digits01[micro100],
						digits10[micro1], digits01[micro1],
					}...)
				}
				buf = append(buf, '\'')
			}
		case []byte:
			if v == nil {
				buf = append(buf, "NULL"...)
			} else {
				buf = append(buf, "_binary'"...)
				if mc.status&statusNoBackslashEscapes == 0 {
					buf = escapeBytesBackslash(buf, v)
				} else {
					buf = escapeBytesQuotes(buf, v)
				}
				buf = append(buf, '\'')
			}
		case string:
			buf = append(buf, '\'')
			if mc.status&statusNoBackslashEscapes == 0 {
				buf = escapeStringBackslash(buf, v)
			} else {
				buf = escapeStringQuotes(buf, v)
			}
			buf = append(buf, '\'')
		default:
			return "", driver.ErrSkip
		}

		if len(buf)+4 > mc.maxAllowedPacket {
			return "", driver.ErrSkip
		}
	}
	if argPos != len(args) {
		return "", driver.ErrSkip
	}
	return string(buf), nil
}

func (mc *mysqlConn) Exec(query string, args []driver.Value) (driver.Result, error) {
	if mc.closed.IsSet() {
		errLog.Print(ErrInvalidConn)
		return nil, driver.ErrBadConn
	}
	if len(args) != 0 {
		if !mc.cfg.InterpolateParams {
			return nil, driver.ErrSkip
		}
		// try to interpolate the parameters to save extra roundtrips for preparing and closing a statement
		prepared, err := mc.interpolateParams(query, args)
		if err != nil {
			return nil, err
		}
		query = prepared
	}
	mc.affectedRows = 0
	mc.insertID = 0

	err := mc.exec(query)
	if err == nil {
		return &mysqlResult{
			affectedRows: int64(mc.affectedRows),
			insertID:     int64(mc.insertID),
		}, err
	}
	return nil, mc.markBadConn(err)
}

// Internal function to execute commands
func (mc *mysqlConn) exec(query string) error {
	// Send command
	if err := mc.writeCommandPacketStr(comQuery, query); err != nil {
		return mc.markBadConn(err)
	}

	// Read Result
	resLen, err := mc.readResultSetHeaderPacket()
	if err != nil {
		return err
	}

	if resLen > 0 {
		// columns
		if err := mc.readUntilEOF(); err != nil {
			return err
		}

		// rows
		if err := mc.readUntilEOF(); err != nil {
			return err
		}
	}

	return mc.discardResults()
}

// Gets the value of the given MySQL System Variable
// The returned byte slice is only valid until the next read
func (mc *mysqlConn) getSystemVar(name string) ([]byte, error) {
	// Send command
	if err := mc.writeCommandPacketStr(comQuery, "SELECT @@"+name); err != nil {
		return nil, err
	}

	// Read Result
	resLen, err := mc.readResultSetHeaderPacket()
	if err == nil {
		rows := new(textRows)
		rows.mc = mc
		rows.rs.columns = []mysqlField{{fieldType: fieldTypeVarChar}}

		if resLen > 0 {
			// Columns
			if err := mc.readUntilEOF(); err != nil {
				return nil, err
			}
		}

		dest := make([]driver.Value, resLen)
		if err = rows.readRow(dest); err == nil {
			return dest[0].([]byte), mc.readUntilEOF()
		}
	}
	return nil, err
}

// finish is called when the query has canceled.
func (mc *mysqlConn) cancel(err error) {
	mc.canceled.Set(err)
	mc.cleanup()
}

// finish is called when the query has succeeded.
func (mc *mysqlConn) finish() {
	if !mc.watching || mc.finished == nil {
		return
	}
	select {
	case mc.finished <- struct{}{}:
		mc.watching = false
	case <-mc.closech:
	}
}

// Ping implements driver.Pinger interface
func (mc *mysqlConn) Ping(ctx context.Context) (err error) {
	if mc.closed.IsSet() {
		errLog.Print(ErrInvalidConn)
		return driver.ErrBadConn
	}

	if err = mc.watchCancel(ctx); err != nil {
		return
	}
	defer mc.finish()

	if err = mc.writeCommandPacket(comPing); err != nil {
		return
	}

	return mc.readResultOK()
}

func (mc *mysqlConn) watchCancel(ctx context.Context) error {
	if mc.watching {
		// Reach here if canceled,
		// so the connection is already invalid
		mc.cleanup()
		return nil
	}
	if ctx.Done() == nil {
		return nil
	}

	mc.watching = true
	select {
	default:
	case <-ctx.Done():
		return ctx.Err()
	}
	if mc.watcher == nil {
		return nil
	}

	mc.watcher <- ctx

	return nil
}

func (mc *mysqlConn) startWatcher() {
	watcher := make(chan context.Context, 1)
	mc.watcher = watcher
	finished := make(chan struct{})
	mc.finished = finished
	go func() {
		for {
			var ctx context.Context
			select {
			case ctx = <-watcher:
			case <-mc.closech:
				return
			}

			select {
			case <-ctx.Done():
				mc.cancel(ctx.Err())
			case <-finished:
			case <-mc.closech:
				return
			}
		}
	}()
}

// ResetSession implements driver.SessionResetter.
// (From Go 1.10)
func (mc *mysqlConn) ResetSession(ctx context.Context) error {
	if mc.closed.IsSet() {
		return driver.ErrBadConn
	}
	return nil
}