package mysql

import (
	"fmt"
	"strings"
	"sync"
	"time"

	log "github.com/sirupsen/logrus"
	"github.com/pingcap/tidb/util/hack"
	"github.com/zr-hebo/sniffer-agent/model"
)

type MysqlSession struct {
	connectionID             *string
	visitUser                *string
	visitDB                  *string
	clientHost               *string
	clientPort               int
	serverIP                 *string
	serverPort               int
	stmtBeginTime            int64
	beginSeqID               int64
	packageOffset            int64
	expectReceiveSize        int
	coverRanges              []*jigsaw
	expectSendSize           int
	prepareInfo              *prepareInfo
	cachedPrepareStmt        map[int][]byte
	cachedStmtBytes          []byte
	computeWindowSizeCounter int

	tcpPacketCache []*model.TCPPacket

	queryPieceReceiver chan model.QueryPiece
	lastSeq            int64
	closeConn          chan bool
	pkgCacheLock       sync.Mutex

	ignoreAckID int64
	sendSize    int64
}

type prepareInfo struct {
	prepareStmtID int
}

var (
	windowSizeCache = make(map[string]*packageWindowCounter, 16)
)

const (
	maxIPPackageSize = 1 << 16
)

func NewMysqlSession(
	sessionKey *string, clientIP *string, clientPort int, serverIP *string, serverPort int,
	receiver chan model.QueryPiece) (ms *MysqlSession) {
	ms = &MysqlSession{
		connectionID:       sessionKey,
		clientHost:         clientIP,
		clientPort:         clientPort,
		serverIP:           serverIP,
		serverPort:         serverPort,
		stmtBeginTime:      time.Now().UnixNano() / millSecondUnit,
		cachedPrepareStmt:  make(map[int][]byte, 8),
		coverRanges:        make([]*jigsaw, 0, 4),
		queryPieceReceiver: receiver,
		closeConn:          make(chan bool, 1),
		lastSeq:            -1,
		ignoreAckID:        -1,
		sendSize:           0,
		pkgCacheLock:       sync.Mutex{},
	}

	return
}

func (ms *MysqlSession) ReceiveTCPPacket(newPkt *model.TCPPacket) {
	if newPkt == nil {
		return
	}

	if !newPkt.ToServer && ms.ignoreAckID == newPkt.Seq {
		// ignore to response to client data
		ms.ignoreAckID = ms.ignoreAckID + int64(len(newPkt.Payload))
		return

	} else if !newPkt.ToServer {
		ms.ignoreAckID = newPkt.Seq + int64(len(newPkt.Payload))
	}

	if newPkt.ToServer {
		ms.resetBeginTime()
		ms.readFromClient(newPkt.Seq, newPkt.Payload)

	} else {
		ms.readFromServer(newPkt.Payload)
		qp := ms.GenerateQueryPiece()
		if qp != nil {
			ms.queryPieceReceiver <- qp
		}
	}
}

func (ms *MysqlSession) resetBeginTime() {
	ms.stmtBeginTime = time.Now().UnixNano() / millSecondUnit
}

func (ms *MysqlSession) readFromServer(bytes []byte) {
	if ms.expectSendSize < 1 {
		ms.expectSendSize = extractMysqlPayloadSize(bytes[:4])
		contents := bytes[4:]
		if ms.prepareInfo != nil && contents[0] == 0 {
			ms.prepareInfo.prepareStmtID = bytesToInt(contents[1:5])
		}
	}
}

func (ms *MysqlSession) mergeRanges() {
	if len(ms.coverRanges) > 1 {
		newRange, newPkgRanges := mergeRanges(ms.coverRanges[0], ms.coverRanges[1:])
		tmpRanges := make([]*jigsaw, len(newPkgRanges)+1)
		tmpRanges[0] = newRange
		if len(newPkgRanges) > 0 {
			copy(tmpRanges[1:], newPkgRanges)
		}
		ms.coverRanges = tmpRanges
	}
}

func mergeRanges(currRange *jigsaw, pkgRanges []*jigsaw) (mergedRange *jigsaw, newPkgRanges []*jigsaw) {
	var nextRange *jigsaw
	newPkgRanges = make([]*jigsaw, 0, 4)

	if len(pkgRanges) < 1 {
		return currRange, newPkgRanges

	} else if len(pkgRanges) == 1 {
		nextRange = pkgRanges[0]

	} else {
		nextRange, newPkgRanges = mergeRanges(pkgRanges[0], pkgRanges[1:])
	}

	if currRange.e >= nextRange.b {
		mergedRange = &jigsaw{b: currRange.b, e: nextRange.e}

	} else {
		tmpRanges := make([]*jigsaw, len(newPkgRanges)+1)
		tmpRanges[0] = nextRange
		if len(newPkgRanges) > 0 {
			copy(tmpRanges[1:], newPkgRanges)
		}
		newPkgRanges = tmpRanges
		mergedRange = currRange
	}

	return
}

func (ms *MysqlSession) oneMysqlPackageFinish() bool {
	if int64(len(ms.cachedStmtBytes))%MaxMysqlPacketLen == 0 {
		return true
	}

	return false
}

func (ms *MysqlSession) checkFinish() bool {
	if len(ms.coverRanges) != 1 {
		ranges := make([]string, 0, len(ms.coverRanges))
		for _, cr := range ms.coverRanges {
			ranges = append(ranges, fmt.Sprintf("[%d -- %d]", cr.b, cr.e))
		}

		log.Debugf("in session %s get invalid range: %s", *ms.connectionID, strings.Join(ranges, ", "))
		return false
	}

	firstRange := ms.coverRanges[0]
	if firstRange.e-firstRange.b != int64(len(ms.cachedStmtBytes)) {
		return false
	}

	return true
}

func (ms *MysqlSession) readFromClient(seqID int64, bytes []byte) {
	contentSize := int64(len(bytes))

	if ms.expectReceiveSize == 0 || ms.oneMysqlPackageFinish() {
		ms.expectReceiveSize = extractMysqlPayloadSize(bytes[:4])
		ms.packageOffset = int64(len(ms.cachedStmtBytes))

		contents := bytes[4:]
		if contents[0] == ComStmtPrepare {
			ms.prepareInfo = &prepareInfo{}
		}

		contentSize = int64(len(contents))
		seqID += 4
		ms.beginSeqID = seqID
		newCache := make([]byte, ms.expectReceiveSize+len(ms.cachedStmtBytes))
		if len(ms.cachedStmtBytes) > 0 {
			copy(newCache[:len(ms.cachedStmtBytes)], ms.cachedStmtBytes)
		}

		if int64(ms.expectReceiveSize+len(ms.cachedStmtBytes)) >= ms.packageOffset+int64(len(contents)) {
			copy(newCache[ms.packageOffset:ms.packageOffset+int64(len(contents))], contents)
			ms.cachedStmtBytes = newCache
		}

	} else {
		if seqID < ms.beginSeqID {
			log.Debugf("in session %s get outdate package with Seq:%d", *ms.connectionID, seqID)
			return
		}

		seqOffset := seqID - ms.beginSeqID
		if ms.packageOffset+seqOffset+int64(len(bytes)) <= int64(ms.expectReceiveSize) {
			copy(ms.cachedStmtBytes[ms.packageOffset+seqOffset:ms.packageOffset+seqOffset+int64(len(bytes))], bytes)
		}
	}

	insertIdx := len(ms.coverRanges)
	for idx, cr := range ms.coverRanges {
		if seqID < cr.b {
			insertIdx = idx
			break
		}
	}

	cr := &jigsaw{b: seqID, e: seqID + contentSize}
	if len(ms.coverRanges) < 1 || insertIdx == len(ms.coverRanges) {
		ms.coverRanges = append(ms.coverRanges, cr)

	} else {
		newCoverRanges := make([]*jigsaw, len(ms.coverRanges)+1)
		copy(newCoverRanges[:insertIdx], ms.coverRanges[:insertIdx])
		newCoverRanges[insertIdx] = cr
		copy(newCoverRanges[insertIdx+1:], ms.coverRanges[insertIdx:])
		ms.coverRanges = newCoverRanges
	}

	ms.mergeRanges()
}

func (ms *MysqlSession) GenerateQueryPiece() (qp model.QueryPiece) {
	defer func() {
		ms.cachedStmtBytes = nil
		ms.expectReceiveSize = 0
		ms.expectSendSize = 0
		ms.prepareInfo = nil
		ms.coverRanges = make([]*jigsaw, 0, 4)
		ms.lastSeq = -1
		ms.ignoreAckID = -1
		ms.sendSize = 0
	}()

	if len(ms.cachedStmtBytes) < 1 {
		return
	}

	if !ms.checkFinish() {
		log.Debugf("receive a not complete cover")
		return
	}

	var mqp *model.PooledMysqlQueryPiece
	var querySQLInBytes []byte
	if ms.cachedStmtBytes[0] > 32 {
		userName, dbName, err := parseAuthInfo(ms.cachedStmtBytes)
		if err != nil {
			log.Errorf("parse auth info failed <-- %s", err.Error())
			return
		}
		ms.visitUser = &userName
		ms.visitDB = &dbName

	} else {
		switch ms.cachedStmtBytes[0] {
		case ComInitDB:
			newDBName := string(ms.cachedStmtBytes[1:])
			useSQL := fmt.Sprintf("use %s", newDBName)
			querySQLInBytes = hack.Slice(useSQL)
			mqp = ms.composeQueryPiece()
			mqp.QuerySQL = &useSQL
			// update session database
			ms.visitDB = &newDBName

		case ComDropDB:
			dbName := string(ms.cachedStmtBytes[1:])
			dropSQL := fmt.Sprintf("drop database %s", dbName)
			mqp = ms.composeQueryPiece()
			mqp.QuerySQL = &dropSQL

		case ComCreateDB, ComQuery:
			mqp = ms.composeQueryPiece()
			querySQLInBytes = ms.cachedStmtBytes[1:]
			querySQL := hack.String(querySQLInBytes)
			mqp.QuerySQL = &querySQL

		case ComStmtPrepare:
			mqp = ms.composeQueryPiece()
			querySQLInBytes = ms.cachedStmtBytes[1:]
			querySQL := hack.String(querySQLInBytes)
			mqp.QuerySQL = &querySQL
			ms.cachedPrepareStmt[ms.prepareInfo.prepareStmtID] = querySQLInBytes
			log.Debugf("prepare statement %s, get id:%d", querySQL, ms.prepareInfo.prepareStmtID)

		case ComStmtExecute:
			prepareStmtID := bytesToInt(ms.cachedStmtBytes[1:5])
			mqp = ms.composeQueryPiece()
			querySQLInBytes = ms.cachedPrepareStmt[prepareStmtID]
			querySQL := hack.String(querySQLInBytes)
			mqp.QuerySQL = &querySQL
			log.Debugf("execute prepare statement:%d", prepareStmtID)

		case ComStmtClose:
			prepareStmtID := bytesToInt(ms.cachedStmtBytes[1:5])
			delete(ms.cachedPrepareStmt, prepareStmtID)
			log.Debugf("remove prepare statement:%d", prepareStmtID)

		default:
			return
		}
	}


	if strictMode && mqp != nil && mqp.VisitUser == nil {
		user, db, err := querySessionInfo(ms.serverPort, mqp.SessionID)
		if err != nil {
			log.Errorf("query user and db from mysql failed <-- %s", err.Error())
		} else {
			mqp.VisitUser = user
			mqp.VisitDB = db
		}
	}

	return filterQueryPieceBySQL(mqp, querySQLInBytes)
}

func filterQueryPieceBySQL(mqp *model.PooledMysqlQueryPiece, querySQL []byte) (model.QueryPiece) {
	if mqp == nil || querySQL == nil {
		return nil

	} else if (uselessSQLPattern.Match(querySQL)) {
		return nil
	}

	if ddlPatern.Match(querySQL) {
		mqp.SetNeedSyncSend(true)
	}

	return mqp
}

func (ms *MysqlSession) composeQueryPiece() (mqp *model.PooledMysqlQueryPiece) {
	return model.NewPooledMysqlQueryPiece(
		ms.connectionID, ms.clientHost, ms.visitUser, ms.visitDB, ms.clientHost, ms.serverIP,
		ms.clientPort, ms.serverPort, ms.stmtBeginTime)
}