package database

import (
	"errors"
	"fmt"
	"hash/crc32"
	"io"
	"log"
	"net"
	"os"
	"path/filepath"
	"sync"
	"time"

	"gordenko.dev/dima/qb/atree"
	"gordenko.dev/dima/qb/bin"
	"gordenko.dev/dima/qb/freelist"
	"gordenko.dev/dima/qb/txlog"
)

func JoinSnapshotFileName(dir string, logNumber int) string {
	return filepath.Join(dir, fmt.Sprintf("%d.snapshot", logNumber))
}

// type metricLockEntry struct {
// 	XLock     bool
// 	RLocks    int
// 	WaitQueue []any
// }

type Database struct {
	mutex           sync.Mutex
	workerSignalCh  chan struct{}
	workerQueue     []any
	rLocksToRelease []uint32
	metrics         map[uint32]*_metric
	//metricLockEntries map[uint32]*metricLockEntry
	dataFreeList  *freelist.FreeList
	indexFreeList *freelist.FreeList
	dir           string
	databaseName  string
	txlog         *txlog.Writer
	atree         *atree.Atree
	tcpPort       int
	logfile       *os.File
	logger        *log.Logger
	exitCh        chan struct{}
	waitGroup     *sync.WaitGroup
}

type Options struct {
	TCPPort      int
	Dir          string
	DatabaseName string
	RedoDir      string
	Logfile      *os.File
	ExitCh       chan struct{}
	WaitGroup    *sync.WaitGroup
}

func New(opt Options) (_ *Database, err error) {
	if opt.TCPPort <= 0 {
		return nil, errors.New("TCPPort option is required")
	}
	if opt.Dir == "" {
		return nil, errors.New("Dir option is required")
	}
	if opt.DatabaseName == "" {
		return nil, errors.New("DatabaseName option is required")
	}
	if opt.RedoDir == "" {
		return nil, errors.New("RedoDir option is required")
	}
	if opt.Logfile == nil {
		return nil, errors.New("Logfile option is required")
	}
	if opt.ExitCh == nil {
		return nil, errors.New("ExitCh option is required")
	}
	if opt.WaitGroup == nil {
		return nil, errors.New("WaitGroup option is required")
	}

	// deltaFreeListFile, err := os.OpenFile(
	// 	filepath.Join(opt.Dir, opt.DatabaseName+".deltafree"),
	// 	os.O_RDWR|os.O_CREATE,
	// 	0666,
	// )
	// if err != nil {
	// 	return nil, err
	// }

	dataFreeList, err := freelist.New(freelist.Options{
		PageSize:      2048,
		BaseFilePath:  filepath.Join(opt.Dir, opt.DatabaseName+".free_data_base"),
		DeltaFilePath: filepath.Join(opt.Dir, opt.DatabaseName+".free_data_delta"),
	})

	indexFreeList, err := freelist.New(freelist.Options{
		PageSize:      2048,
		BaseFilePath:  filepath.Join(opt.Dir, opt.DatabaseName+".free_index_base"),
		DeltaFilePath: filepath.Join(opt.Dir, opt.DatabaseName+".free_index_delta"),
	})

	s := &Database{
		workerSignalCh: make(chan struct{}, 1),
		dir:            opt.Dir,
		databaseName:   opt.DatabaseName,
		metrics:        make(map[uint32]*_metric),
		//metricLockEntries: make(map[uint32]*metricLockEntry),
		dataFreeList:  dataFreeList,
		indexFreeList: indexFreeList,
		tcpPort:       opt.TCPPort,
		logfile:       opt.Logfile,
		logger:        log.New(opt.Logfile, "", log.LstdFlags),
		exitCh:        opt.ExitCh,
		waitGroup:     opt.WaitGroup,
	}
	return s, nil
}

func (s *Database) ListenAndServe() (err error) {
	listener, err := net.Listen("tcp", fmt.Sprintf(":%d", s.tcpPort))
	if err != nil {
		return fmt.Errorf("net.Listen: %s; port=%d", err, s.tcpPort)
	}

	s.atree, err = atree.New(atree.Options{
		Dir:          s.dir,
		DatabaseName: s.databaseName,
	})
	if err != nil {
		return fmt.Errorf("atree.New: %s", err)
	}
	s.atree.Run()

	go s.worker()

	s.recovery()

	s.logger.Println("database started")
	for {
		// Listen for an incoming connection.
		conn, err := listener.Accept()
		if err != nil {
			s.logger.Printf("listener.Accept: %s\n", err)
			time.Sleep(time.Second)
		} else {
			go s.handleTCPConn(conn)
		}
	}
}

func (s *Database) recovery() {
	// FIX
	// advisor, err := recovery.NewRecoveryAdvisor(recovery.RecoveryAdvisorOptions{
	// 	Dir:            s.dir,
	// 	VerifySnapshot: s.verifySnapshot,
	// })
	// if err != nil {
	// 	panic(err)
	// }

	// recipe, err := advisor.GetRecipe()
	// if err != nil {
	// 	qb.Abort(qb.GetRecoveryRecipeFailed, err)
	// }

	// var logNumber int

	// if recipe != nil {
	// 	if recipe.Snapshot != "" {
	// 		err = s.loadSnapshot(recipe.Snapshot)
	// 		if err != nil {
	// 			qb.Abort(qb.LoadSnapshotFailed, err)
	// 		}
	// 	}
	// 	for _, changesFileName := range recipe.Changes {
	// 		err = s.replayChanges(changesFileName)
	// 		if err != nil {
	// 			qb.Abort(qb.ReplayChangesFailed, err)
	// 		}
	// 	}
	// 	logNumber = recipe.LogNumber
	// }

	// s.txlog, err = txlog.NewWriter(txlog.WriterOptions{
	// 	Dir:                 s.dir,
	// 	LogNumber:           logNumber,
	// 	AppendToWorkerQueue: s.appendJobToWorkerQueue,
	// 	FreeList:            s.freeList,
	// 	Atree:               s.atree,
	// 	ExitCh:              s.exitCh,
	// 	WaitGroup:           s.waitGroup,
	// })
	// if err != nil {
	// 	qb.Abort(qb.CreateChangesWriterFailed, err)

	// }
	// go s.txlog.Run()

	// // fileNames, err := s.searchREDOFiles()
	// // if err != nil {
	// // 	qb.Abort(qb.SearchREDOFilesFailed, err)
	// // }

	// // if len(fileNames) > 0 {
	// // 	for _, fileName := range fileNames {
	// // 		err = s.replayREDOFile(fileName)
	// // 		if err != nil {
	// // 			qb.Abort(qb.ReplayREDOFileFailed, err)
	// // 		}
	// // 	}

	// // 	for _, fileName := range fileNames {
	// // 		err = os.Remove(fileName)
	// // 		if err != nil {
	// // 			qb.Abort(qb.RemoveREDOFileFailed, err)
	// // 		}
	// // 	}
	// // }

	// if recipe != nil {
	// 	if recipe.CompleteSnapshot {
	// 		err = s.dumpSnapshot(logNumber)
	// 		if err != nil {
	// 			qb.Abort(qb.DumpSnapshotFailed, err)
	// 		}
	// 	}

	// 	for _, fileName := range recipe.ToDelete {
	// 		err = os.Remove(fileName)
	// 		if err != nil {
	// 			qb.Abort(qb.RemoveRecipeFileFailed, err)
	// 		}
	// 	}
	// }
}

// func (s *Database) searchREDOFiles() ([]string, error) {
// 	var (
// 		reREDO    = regexp.MustCompile(`a\d+\.redo`)
// 		fileNames []string
// 	)

// 	entries, err := os.ReadDir(s.redoDir)
// 	if err != nil {
// 		return nil, err
// 	}

// 	for _, entry := range entries {
// 		if entry.Type().IsRegular() {
// 			baseName := entry.Name()
// 			if reREDO.MatchString(baseName) {
// 				fileNames = append(fileNames, filepath.Join(s.redoDir, baseName))
// 			}
// 		}
// 	}
// 	return fileNames, nil
// }

// func (s *Database) replayREDOFile(fileName string) error {
// 	redoFile, err := redo.ReadREDOFile(redo.ReadREDOFileReq{
// 		FileName:      fileName,
// 		DataPageSize:  atree.DataPageSize,
// 		IndexPageSize: atree.IndexPageSize,
// 	})
// 	if err != nil {
// 		return fmt.Errorf("can't read REDO file %s: %s", fileName, err)
// 	}

// 	metric, ok := s.metrics[redoFile.MetricID]
// 	if !ok {
// 		return fmt.Errorf("has REDOFile, metric %d not found", redoFile.MetricID)
// 	}

// 	if metric.Until < redoFile.Timestamp {
// 		waitCh := make(chan struct{})
// 		s.atree.ApplyREDO(atree.WriteTask{
// 			DataPage:   redoFile.DataPage,
// 			IndexPages: redoFile.IndexPages,
// 		})
// 		<-waitCh

// 		waitCh = s.txlog.WriteAppendedMeasureWithOverflow(
// 			txlog.AppendedMeasureWithOverflow{
// 				MetricID:         redoFile.MetricID,
// 				Timestamp:        redoFile.Timestamp,
// 				Value:            redoFile.Value,
// 				IsDataPageReused: redoFile.IsDataPageReused,
// 				DataPageNo:       redoFile.DataPage.PageNo,
// 				IsRootChanged:    redoFile.IsRootChanged,
// 				RootPageNo:       redoFile.RootPageNo,
// 				ReusedIndexPages: redoFile.ReusedIndexPages,
// 			},
// 			fileName,
// 			false,
// 		)
// 		<-waitCh
// 	}
// 	return nil
// }

func (s *Database) verifySnapshot(fileName string) (_ bool, err error) {
	file, err := os.Open(fileName)
	if err != nil {
		return
	}
	defer file.Close()

	stat, err := file.Stat()
	if err != nil {
		return
	}

	if stat.Size() <= 4 {
		return false, nil
	}

	var (
		payloadSize = stat.Size() - 4
		hash        = crc32.NewIEEE()
	)

	_, err = io.CopyN(hash, file, payloadSize)
	if err != nil {
		return
	}
	calculatedCRC := hash.Sum32()

	storedCRC, err := bin.ReadUint32(file)
	if err != nil {
		return
	}
	if storedCRC != calculatedCRC {
		return false, fmt.Errorf("strored CRC %d not equal calculated CRC %d",
			storedCRC, calculatedCRC)
	}
	return true, nil
}

func (s *Database) replayChanges(fileName string) error {
	walReader, err := txlog.NewReader(txlog.ReaderOptions{
		FileName:   fileName,
		BufferSize: 1024 * 1024,
	})
	if err != nil {
		return err
	}

	for {
		lsn, records, done, err := walReader.ReadPacket()
		if err != nil {
			return err
		}
		_ = lsn

		if done {
			return nil
		}

		for _, record := range records {
			if err = s.replayChangesRecord(record); err != nil {
				return err
			}
		}
	}
}

func (s *Database) replayChangesRecord(untyped any) error {
	// 	switch rec := untyped.(type) {
	// 	case txlog.AddedMetric:
	// 		var (
	// 			values        qb.ValueCompressor
	// 			timestampsBuf = conbuf.New(nil)
	// 			valuesBuf     = conbuf.New(nil)
	// 		)

	// 		if rec.MetricType == qb.Cumulative {
	// 			values = chunkenc.NewReverseCumulativeDeltaCompressor(
	// 				valuesBuf, 0, byte(rec.FracDigits))
	// 		} else {
	// 			values = chunkenc.NewReverseInstantDeltaCompressor(
	// 				valuesBuf, 0, byte(rec.FracDigits))
	// 		}

	// 		s.metrics[rec.MetricID] = &_metric{
	// 			MetricType:    rec.MetricType,
	// 			FracDigits:    byte(rec.FracDigits),
	// 			TimestampsBuf: timestampsBuf,
	// 			ValuesBuf:     valuesBuf,
	// 			Timestamps:    chunkenc.NewReverseTimeDeltaCompressor(timestampsBuf, 0),
	// 			Values:        values,
	// 		}

	// 	case txlog.DeletedMetric:
	// 		delete(s.metrics, rec.MetricID)
	// 		if len(rec.FreePageNumbers) > 0 {
	// 			s.freeList.AddPages(rec.FreePageNumbers)
	// 		}

	// 	case txlog.AppendedMeasure:
	// 		metric, ok := s.metrics[rec.MetricID]
	// 		if ok {
	// 			metric.Timestamps.Append(rec.Timestamp)
	// 			metric.Values.Append(rec.Value)

	// 			if metric.Since == 0 {
	// 				metric.Since = rec.Timestamp
	// 				metric.SinceValue = rec.Value
	// 			}

	// 			metric.Until = rec.Timestamp
	// 			metric.UntilValue = rec.Value
	// 		}

	// 	case txlog.AppendedMeasures:
	// 		metric, ok := s.metrics[rec.MetricID]
	// 		if ok {
	// 			for _, measure := range rec.Measures {
	// 				metric.Timestamps.Append(measure.Timestamp)
	// 				metric.Values.Append(measure.Value)

	// 				if metric.Since == 0 {
	// 					metric.Since = measure.Timestamp
	// 					metric.SinceValue = measure.Value
	// 				}

	// 				metric.Until = measure.Timestamp
	// 				metric.UntilValue = measure.Value
	// 			}
	// 		}

	// 	// case txlog.AppendedMeasureWithOverflow:
	// 	// 	metric, ok := s.metrics[rec.MetricID]
	// 	// 	if ok {
	// 	// 		metric.ReinitBy(rec.Timestamp, rec.Value)
	// 	// 		if rec.IsRootChanged {
	// 	// 			metric.RootPageNo = rec.RootPageNo
	// 	// 		}
	// 	// 		metric.LastPageNo = rec.DataPageNo
	// 	// 		// delete free pages
	// 	// 		if rec.IsDataPageReused {
	// 	// 			s.freeList.DeleteReservedPages([]uint32{
	// 	// 				rec.DataPageNo,
	// 	// 			})
	// 	// 		}
	// 	// 		if len(rec.ReusedIndexPages) > 0 {
	// 	// 			s.freeList.DeleteReservedPages(rec.ReusedIndexPages)
	// 	// 		}
	// 	// 	}

	// 	case txlog.DeletedMeasures:
	// 		metric, ok := s.metrics[rec.MetricID]
	// 		if ok {
	// 			metric.DeleteMeasures()
	// 			if len(rec.FreePageNumbers) > 0 {
	// 				s.freeList.AddPages(rec.FreePageNumbers)
	// 			}
	// 		}

	// 	default:
	// 		qb.Abort(qb.UnknownTxLogRecordTypeBug,
	// 			fmt.Errorf("bug: unknown record type %T in TransactionLog", rec))
	// 	}
	return nil
}