package mysql

import (
	"bytes"
	"encoding/binary"
	"io"
	"strings"

	csm "git.loafle.net/commons/service_matcher-go"
)

type MySqlMatcher struct {
	csm.Matchers
	meta csm.Metadata
}

func (m *MySqlMatcher) Key() string {
	return "MYSQL"
}

func (m *MySqlMatcher) Name() string {
	name := "MySQL"
	if v, ok := m.meta["version"]; ok {
		if strings.Contains(v, "MariaDB") {
			name = "MariaDB"
		}
		name = name + " (" + v + ")"
	}
	return name
}

func (m *MySqlMatcher) Meta() csm.Metadata {
	return m.meta
}

func (m *MySqlMatcher) IsPrePacket() bool {
	return true
}

func (m *MySqlMatcher) HasResponse(index int) bool {
	return true
}

func (m *MySqlMatcher) IsError(info csm.MatchInfo, index int, packet *csm.Packet) bool {
	return false
}

type serverSettings struct {
	protocol     byte
	version      string
	flags        uint32
	charset      uint8
	scrambleBuff []byte
	threadID     uint32
	keepalive    int64
}

func (m *MySqlMatcher) Match(info csm.MatchInfo, index int, packet *csm.Packet) error {
	if packet == nil || packet.Buffer == nil || packet.Len == 0 {
		return csm.NoPacketReceivedError()
	}

	buf := bytes.NewBuffer(packet.Buffer[:3])
	packetLen, _ := binary.ReadUvarint(buf)
	if packetLen != uint64(packet.Len-4) {
		return csm.NotMatchedError()
	}
	pos := 4
	p := new(serverSettings)
	p.protocol = packet.Buffer[pos]
	if p.protocol != 9 && p.protocol != 10 {
		return csm.NotMatchedError()
	}
	pos++
	slice, err := readSlice(packet.Buffer[pos:], 0x00)
	if err != nil {
		return csm.NotMatchedError()
	}
	m.meta["version"] = string(slice)
	pos += len(slice) + 1

	p.threadID = bytesToUint32(packet.Buffer[pos : pos+4])
	pos += 4

	return nil
}

func readSlice(data []byte, delim byte) (slice []byte, e error) {
	pos := bytes.IndexByte(data, delim)
	if pos > -1 {
		slice = data[:pos]
	} else {
		slice = data
		e = io.EOF
	}
	return
}

func bytesToUint32(b []byte) (n uint32) {
	for i := uint8(0); i < 4; i++ {
		n |= uint32(b[i]) << (i * 8)
	}
	return
}

func NewMatcher() csm.Matcher {
	m := &MySqlMatcher{}
	m.meta = csm.NewMetadata()
	return m
}