// 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 mysql

import (
	"crypto/tls"
	"database/sql/driver"
	"errors"
	"net"
	"strconv"
	"strings"
	"time"
)

type mysqlConn struct {
	buf              buffer
	netConn          net.Conn
	affectedRows     uint64
	insertId         uint64
	cfg              *config
	maxPacketAllowed int
	maxWriteSize     int
	flags            clientFlag
	status           statusFlag
	sequence         uint8
	parseTime        bool
	strict           bool
}

type config struct {
	user              string
	passwd            string
	net               string
	addr              string
	dbname            string
	params            map[string]string
	loc               *time.Location
	tls               *tls.Config
	timeout           time.Duration
	collation         uint8
	allowAllFiles     bool
	allowOldPasswords bool
	clientFoundRows   bool
	columnsWithAlias  bool
	interpolateParams bool
}

// 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
			}

		// time.Time parsing
		case "parseTime":
			var isBool bool
			mc.parseTime, isBool = readBool(val)
			if !isBool {
				return errors.New("Invalid Bool value: " + val)
			}

		// Strict mode
		case "strict":
			var isBool bool
			mc.strict, isBool = readBool(val)
			if !isBool {
				return errors.New("Invalid Bool value: " + val)
			}

		// Compression
		case "compress":
			err = errors.New("Compression not implemented yet")
			return

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

	return
}

func (mc *mysqlConn) Begin() (driver.Tx, error) {
	if mc.netConn == nil {
		errLog.Print(ErrInvalidConn)
		return nil, driver.ErrBadConn
	}
	err := mc.exec("START TRANSACTION")
	if err == nil {
		return &mysqlTx{mc}, err
	}

	return nil, err
}

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

	mc.cfg = nil
	mc.buf.rd = nil

	return
}

func (mc *mysqlConn) Prepare(query string) (driver.Stmt, error) {
	if mc.netConn == nil {
		errLog.Print(ErrInvalidConn)
		return nil, driver.ErrBadConn
	}
	// Send command
	err := mc.writeCommandPacketStr(comStmtPrepare, query)
	if err != nil {
		return nil, err
	}

	stmt := &mysqlStmt{
		mc: mc,
	}

	// Read Result
	columnCount, err := stmt.readPrepareResultPacket()
	if err == nil {
		if stmt.paramCount > 0 {
			if err = mc.readUntilEOF(); err != nil {
				return nil, err
			}
		}

		if columnCount > 0 {
			err = mc.readUntilEOF()
		}
	}

	return stmt, err
}

// https://github.com/mysql/mysql-server/blob/mysql-5.7.5/libmysql/libmysql.c#L1150-L1156
func (mc *mysqlConn) escapeBytes(buf, v []byte) []byte {
	buf = append(buf, '\'')
	if mc.status&statusNoBackslashEscapes == 0 {
		buf = escapeBackslash(buf, v)
	} else {
		buf = escapeQuotes(buf, v)
	}
	return append(buf, '\'')
}

// estimateParamLength calculates upper bound of string length from types.
func estimateParamLength(args []driver.Value) (int, bool) {
	l := 0
	for _, a := range args {
		switch v := a.(type) {
		case int64, float64:
			// 24 (-1.7976931348623157e+308) may be upper bound. But I'm not sure.
			l += 25
		case bool:
			l += 1 // 0 or 1
		case time.Time:
			l += 30 // '1234-12-23 12:34:56.777777'
		case string:
			l += len(v)*2 + 2
		case []byte:
			l += len(v)*2 + 2
		default:
			return 0, false
		}
	}
	return l, true
}

func (mc *mysqlConn) interpolateParams(query string, args []driver.Value) (string, error) {
	estimated, ok := estimateParamLength(args)
	if !ok {
		return "", driver.ErrSkip
	}
	estimated += len(query)

	buf := make([]byte, 0, estimated)
	argPos := 0

	for i := 0; i < len(query); i++ {
		c := query[i]
		if c != '?' {
			buf = append(buf, c)
			continue
		}

		arg := args[argPos]
		argPos++

		if arg == nil {
			buf = append(buf, []byte("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, []byte("'0000-00-00'")...)
			} else {
				v := v.In(mc.cfg.loc)
				year := v.Year()
				month := v.Month()
				day := v.Day()
				hour := v.Hour()
				minute := v.Minute()
				second := v.Second()
				micro := v.Nanosecond() / 1000

				buf = append(buf, []byte{
					byte('\''),
					byte('0' + year/1000),
					byte('0' + year/100%10),
					byte('0' + year/10%10),
					byte('0' + year%10),
					byte('-'),
					byte('0' + month/10),
					byte('0' + month%10),
					byte('-'),
					byte('0' + day/10),
					byte('0' + day%10),
					byte(' '),
					byte('0' + hour/10),
					byte('0' + hour%10),
					byte(':'),
					byte('0' + minute/10),
					byte('0' + minute%10),
					byte(':'),
					byte('0' + second/10),
					byte('0' + second%10),
				}...)

				if micro != 0 {
					buf = append(buf, []byte{
						byte('.'),
						byte('0' + micro/100000),
						byte('0' + micro/10000%10),
						byte('0' + micro/1000%10),
						byte('0' + micro/100%10),
						byte('0' + micro/10%10),
						byte('0' + micro%10),
					}...)
				}
				buf = append(buf, '\'')
			}
		case []byte:
			if v == nil {
				buf = append(buf, []byte("NULL")...)
			} else {
				buf = mc.escapeBytes(buf, v)
			}
		case string:
			buf = mc.escapeBytes(buf, []byte(v))
		default:
			return "", driver.ErrSkip
		}

		if len(buf)+4 > mc.maxPacketAllowed {
			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.netConn == nil {
		errLog.Print(ErrInvalidConn)
		return nil, driver.ErrBadConn
	}
	if len(args) != 0 {
		if !mc.cfg.interpolateParams {
			return nil, driver.ErrSkip
		}
		// try client-side prepare to reduce roundtrip
		prepared, err := mc.interpolateParams(query, args)
		if err != nil {
			return nil, err
		}
		query = prepared
		args = nil
	}
	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, err
}

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

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

		err = mc.readUntilEOF()
	}

	return err
}

func (mc *mysqlConn) Query(query string, args []driver.Value) (driver.Rows, error) {
	if mc.netConn == nil {
		errLog.Print(ErrInvalidConn)
		return nil, driver.ErrBadConn
	}
	if len(args) != 0 {
		if !mc.cfg.interpolateParams {
			return nil, driver.ErrSkip
		}
		// try client-side prepare to reduce roundtrip
		prepared, err := mc.interpolateParams(query, args)
		if err != nil {
			return nil, err
		}
		query = prepared
		args = nil
	}
	// Send command
	err := mc.writeCommandPacketStr(comQuery, query)
	if err == nil {
		// Read Result
		var resLen int
		resLen, err = mc.readResultSetHeaderPacket()
		if err == nil {
			rows := new(textRows)
			rows.mc = mc

			if resLen == 0 {
				// no columns, no more data
				return emptyRows{}, nil
			}
			// Columns
			rows.columns, err = mc.readColumns(resLen)
			return rows, err
		}
	}
	return nil, err
}

// 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

		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
}