package database

import (
	"errors"
	"fmt"
	"io"
	"net"

	"gordenko.dev/dima/diploma"
	"gordenko.dev/dima/diploma/atree"
	"gordenko.dev/dima/diploma/bin"
	"gordenko.dev/dima/diploma/bufreader"
	"gordenko.dev/dima/diploma/chunkenc"
	"gordenko.dev/dima/diploma/conbuf"
	"gordenko.dev/dima/diploma/proto"
	"gordenko.dev/dima/diploma/transform"
	"gordenko.dev/dima/diploma/txlog"
)

var (
	ErrNoValueBug         = errors.New("has timestamp but no value")
	ErrWrongResultCodeBug = errors.New("bug: wrong result code")

	successMsg = []byte{
		proto.RespSuccess,
	}
)

func reply(conn io.Writer, errcode uint16) {
	var answer []byte
	if errcode == 0 {
		answer = successMsg
	} else {
		answer = []byte{
			proto.RespError,
			0, 0,
		}
		bin.PutUint16(answer[1:], errcode)
	}

	_, err := conn.Write(answer)
	if err != nil {
		return
	}
}

func (s *Database) handleTCPConn(conn net.Conn) {
	defer conn.Close()

	r := bufreader.New(conn, 128)

	for {
		err := s.processRequest(conn, r)
		if err != nil {
			if err != io.EOF {
				s.logger.Println(err)
			}
			return
		}
	}
}

func (s *Database) processRequest(conn net.Conn, r *bufreader.BufferedReader) (err error) {
	messageType, err := r.ReadByte()
	if err != nil {
		if err != io.EOF {
			return fmt.Errorf("read messageType: %s", err)
		} else {
			return err
		}
	}

	switch messageType {
	case proto.TypeGetMetric:
		req, err := proto.ReadGetMetricReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadGetMetricReq: %s", err)
		}
		if err = s.GetMetric(conn, req); err != nil {
			return fmt.Errorf("GetMetric: %s", err)
		}

	case proto.TypeAddMetric:
		req, err := proto.ReadAddMetricReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadAddMetricReq: %s", err)
		}
		reply(conn, s.AddMetric(req))

	case proto.TypeDeleteMetric:
		req, err := proto.ReadDeleteMetricReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadDeleteMetricReq: %s", err)
		}
		reply(conn, s.DeleteMetric(req))

	case proto.TypeAppendMeasure:
		req, err := proto.ReadAppendMeasureReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadAppendMeasureReq: %s", err)
		}
		//fmt.Println("append measure", req.MetricID, conn.RemoteAddr().String())
		reply(conn, s.AppendMeasure(req))

	case proto.TypeAppendMeasures:
		req, err := proto.ReadAppendMeasuresReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadAppendMeasuresReq: %s", err)
		}
		//fmt.Println("append measure", req.MetricID, conn.RemoteAddr().String())
		reply(conn, s.AppendMeasures(req))

	case proto.TypeListInstantMeasures:
		req, err := proto.ReadListInstantMeasuresReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadListInstantMeasuresReq: %s", err)
		}
		if err = s.ListInstantMeasures(conn, req); err != nil {
			return fmt.Errorf("ListInstantMeasures: %s", err)
		}

	case proto.TypeListCumulativeMeasures:
		req, err := proto.ReadListCumulativeMeasuresReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadListCumulativeMeasuresReq: %s", err)
		}
		if err = s.ListCumulativeMeasures(conn, req); err != nil {
			return fmt.Errorf("ListCumulativeMeasures: %s", err)
		}

	case proto.TypeListInstantPeriods:
		req, err := proto.ReadListInstantPeriodsReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadListInstantPeriodsReq: %s", err)
		}
		if err = s.ListInstantPeriods(conn, req); err != nil {
			return fmt.Errorf("ListInstantPeriods: %s", err)
		}

	case proto.TypeListCumulativePeriods:
		req, err := proto.ReadListCumulativePeriodsReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadListCumulativePeriodsReq: %s", err)
		}
		if err = s.ListCumulativePeriods(conn, req); err != nil {
			return fmt.Errorf("ListCumulativePeriods: %s", err)
		}

	case proto.TypeListCurrentValues:
		req, err := proto.ReadListCurrentValuesReq(r)
		if err != nil {
			return fmt.Errorf("proto.ListCurrentValuesReq: %s", err)
		}
		if err = s.ListCurrentValues(conn, req); err != nil {
			return fmt.Errorf("ListCurrentValues: %s", err)
		}

	case proto.TypeDeleteMeasures:
		req, err := proto.ReadDeleteMeasuresReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadDeleteMeasuresReq: %s", err)
		}
		reply(conn, s.DeleteMeasures(req))

	case proto.TypeListAllInstantMeasures:
		req, err := proto.ReadListAllInstantMeasuresReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadListAllInstantMeasuresReq: %s", err)
		}
		if err = s.ListAllInstantMeasures(conn, req); err != nil {
			return fmt.Errorf("ListAllInstantMeasures: %s", err)
		}

	case proto.TypeListAllCumulativeMeasures:
		req, err := proto.ReadListAllCumulativeMeasuresReq(r)
		if err != nil {
			return fmt.Errorf("proto.ReadListAllCumulativeMeasuresReq: %s", err)
		}

		if err = s.ListAllCumulativeMeasures(conn, req); err != nil {
			return fmt.Errorf("ListAllCumulativeMeasures: %s", err)
		}

	default:
		return fmt.Errorf("unknown messageType: %d", messageType)
	}
	return
}

// API

func (s *Database) AddMetric(req proto.AddMetricReq) uint16 {
	// Валидация
	if req.MetricID == 0 {
		return proto.ErrEmptyMetricID
	}
	if byte(req.FracDigits) > diploma.MaxFracDigits {
		return proto.ErrWrongFracDigits
	}
	switch req.MetricType {
	case diploma.Cumulative, diploma.Instant:
		// ok
	default:
		return proto.ErrWrongMetricType
	}

	resultCh := make(chan byte, 1)

	s.appendJobToWorkerQueue(tryAddMetricReq{
		MetricID: req.MetricID,
		ResultCh: resultCh,
	})

	resultCode := <-resultCh

	switch resultCode {
	case Succeed:
		waitCh := s.txlog.WriteAddedMetric(txlog.AddedMetric{
			MetricID:   req.MetricID,
			MetricType: req.MetricType,
			FracDigits: req.FracDigits,
		})
		<-waitCh

	case MetricDuplicate:
		return proto.ErrDuplicate

	default:
		diploma.Abort(diploma.WrongResultCodeBug, ErrWrongResultCodeBug)
	}
	return 0
}

type Metric struct {
	MetricType diploma.MetricType
	FracDigits byte
	ResultCode byte
}

func (s *Database) GetMetric(conn io.Writer, req proto.GetMetricReq) error {
	resultCh := make(chan Metric, 1)

	s.appendJobToWorkerQueue(tryGetMetricReq{
		MetricID: req.MetricID,
		ResultCh: resultCh,
	})

	result := <-resultCh

	switch result.ResultCode {
	case Succeed:
		answer := []byte{
			proto.RespValue,
			0, 0, 0, 0, // metricID
			byte(result.MetricType),
			result.FracDigits,
		}
		bin.PutUint32(answer[1:], req.MetricID)

		_, err := conn.Write(answer)
		if err != nil {
			return err
		}

	case NoMetric:
		reply(conn, proto.ErrNoMetric)

	default:
		diploma.Abort(diploma.WrongResultCodeBug, ErrWrongResultCodeBug)
	}
	return nil
}

type tryDeleteMetricResult struct {
	ResultCode byte
	RootPageNo uint32
}

func (s *Database) DeleteMetric(req proto.DeleteMetricReq) uint16 {
	resultCh := make(chan tryDeleteMetricResult, 1)

	s.appendJobToWorkerQueue(tryDeleteMetricReq{
		MetricID: req.MetricID,
		ResultCh: resultCh,
	})

	result := <-resultCh

	switch result.ResultCode {
	case Succeed:
		var (
			freeDataPages  []uint32
			freeIndexPages []uint32
		)
		if result.RootPageNo > 0 {
			pageLists, err := s.atree.GetAllPages(result.RootPageNo)
			if err != nil {
				diploma.Abort(diploma.FailedAtreeRequest, err)
			}
			freeDataPages = pageLists.DataPages
			freeIndexPages = pageLists.IndexPages
		}
		waitCh := s.txlog.WriteDeletedMetric(txlog.DeletedMetric{
			MetricID:       req.MetricID,
			FreeDataPages:  freeDataPages,
			FreeIndexPages: freeIndexPages,
		})
		<-waitCh

	case NoMetric:
		return proto.ErrNoMetric

	default:
		diploma.Abort(diploma.WrongResultCodeBug, ErrWrongResultCodeBug)
	}
	return 0
}

type FilledPage struct {
	Since            uint32
	RootPageNo       uint32
	PrevPageNo       uint32
	TimestampsChunks [][]byte
	TimestampsSize   uint16
	ValuesChunks     [][]byte
	ValuesSize       uint16
}

type tryAppendMeasureResult struct {
	MetricID   uint32
	Timestamp  uint32
	Value      float64
	FilledPage *FilledPage
	ResultCode byte
}

func (s *Database) AppendMeasure(req proto.AppendMeasureReq) uint16 {
	resultCh := make(chan tryAppendMeasureResult, 1)

	s.appendJobToWorkerQueue(tryAppendMeasureReq{
		MetricID:  req.MetricID,
		Timestamp: req.Timestamp,
		Value:     req.Value,
		ResultCh:  resultCh,
	})

	result := <-resultCh

	switch result.ResultCode {
	case CanAppend:
		waitCh := s.txlog.WriteAppendMeasure(txlog.AppendedMeasure{
			MetricID:  req.MetricID,
			Timestamp: req.Timestamp,
			Value:     req.Value,
		})
		<-waitCh

	case NewPage:
		filled := result.FilledPage
		report, err := s.atree.AppendDataPage(atree.AppendDataPageReq{
			MetricID:         req.MetricID,
			Timestamp:        req.Timestamp,
			Value:            req.Value,
			Since:            filled.Since,
			RootPageNo:       filled.RootPageNo,
			PrevPageNo:       filled.PrevPageNo,
			TimestampsChunks: filled.TimestampsChunks,
			TimestampsSize:   filled.TimestampsSize,
			ValuesChunks:     filled.ValuesChunks,
			ValuesSize:       filled.ValuesSize,
		})
		if err != nil {
			diploma.Abort(diploma.WriteToAtreeFailed, err)
		}
		waitCh := s.txlog.WriteAppendedMeasureWithOverflow(
			txlog.AppendedMeasureWithOverflow{
				MetricID:         req.MetricID,
				Timestamp:        req.Timestamp,
				Value:            req.Value,
				IsDataPageReused: report.IsDataPageReused,
				DataPageNo:       report.DataPageNo,
				IsRootChanged:    report.IsRootChanged,
				RootPageNo:       report.NewRootPageNo,
				ReusedIndexPages: report.ReusedIndexPages,
			},
			report.FileName,
			false,
		)
		<-waitCh

	case NoMetric:
		return proto.ErrNoMetric

	case ExpiredMeasure:
		return proto.ErrExpiredMeasure

	case NonMonotonicValue:
		return proto.ErrNonMonotonicValue

	default:
		diploma.Abort(diploma.WrongResultCodeBug, ErrWrongResultCodeBug)
	}
	return 0
}

type tryAppendMeasuresResult struct {
	ResultCode    byte
	MetricType    diploma.MetricType
	FracDigits    byte
	Since         uint32
	Until         uint32
	UntilValue    float64
	RootPageNo    uint32
	PrevPageNo    uint32
	TimestampsBuf *conbuf.ContinuousBuffer
	ValuesBuf     *conbuf.ContinuousBuffer
	Timestamps    diploma.TimestampCompressor
	Values        diploma.ValueCompressor
}

func (s *Database) AppendMeasures(req proto.AppendMeasuresReq) uint16 {
	resultCh := make(chan tryAppendMeasuresResult, 1)

	s.appendJobToWorkerQueue(tryAppendMeasuresReq{
		MetricID: req.MetricID,
		ResultCh: resultCh,
	})

	result := <-resultCh

	switch result.ResultCode {
	case CanAppend:
		var (
			rootPageNo    = result.RootPageNo
			prevPageNo    = result.PrevPageNo
			timestampsBuf = result.TimestampsBuf
			valuesBuf     = result.ValuesBuf
			timestamps    = result.Timestamps
			values        = result.Values
			since         = result.Since
			until         = result.Until
			untilValue    = result.UntilValue
			//
			toAppendMeasures []proto.Measure
		)

		for idx, measure := range req.Measures {
			if since == 0 {
				since = measure.Timestamp
			} else {
				if measure.Timestamp <= until {
					if len(toAppendMeasures) > 0 {
						waitCh := s.txlog.WriteAppendMeasures(
							txlog.AppendedMeasures{
								MetricID: req.MetricID,
								Measures: toAppendMeasures,
							},
							false,
						)
						<-waitCh
					}
					return proto.ErrExpiredMeasure
				}

				if result.MetricType == diploma.Cumulative && measure.Value < untilValue {
					if len(toAppendMeasures) > 0 {
						waitCh := s.txlog.WriteAppendMeasures(
							txlog.AppendedMeasures{
								MetricID: req.MetricID,
								Measures: toAppendMeasures,
							},
							false,
						)
						<-waitCh
					}
					return proto.ErrNonMonotonicValue
				}
			}

			extraSpace := timestamps.CalcRequiredSpace(measure.Timestamp) +
				values.CalcRequiredSpace(measure.Value)

			totalSpace := timestamps.Size() + values.Size() + extraSpace

			if totalSpace <= atree.DataPagePayloadSize {
				timestamps.Append(measure.Timestamp)
				values.Append(measure.Value)
				toAppendMeasures = append(toAppendMeasures, measure)
			} else {
				if len(toAppendMeasures) > 0 {
					waitCh := s.txlog.WriteAppendMeasures(
						txlog.AppendedMeasures{
							MetricID: req.MetricID,
							Measures: toAppendMeasures,
						},
						true,
					)
					<-waitCh

					toAppendMeasures = nil
				}
				//fmt.Printf("APPEND DATA PAGE %d, %v\n", measure.Timestamp, measure.Value)
				report, err := s.atree.AppendDataPage(atree.AppendDataPageReq{
					MetricID:         req.MetricID,
					Timestamp:        measure.Timestamp,
					Value:            measure.Value,
					Since:            since,
					RootPageNo:       rootPageNo,
					PrevPageNo:       prevPageNo,
					TimestampsChunks: timestampsBuf.Chunks(),
					TimestampsSize:   uint16(timestamps.Size()),
					ValuesChunks:     valuesBuf.Chunks(),
					ValuesSize:       uint16(values.Size()),
				})
				if err != nil {
					diploma.Abort(diploma.WriteToAtreeFailed, err)
				}

				prevPageNo = report.DataPageNo
				if report.IsRootChanged {
					rootPageNo = report.NewRootPageNo
				}
				waitCh := s.txlog.WriteAppendedMeasureWithOverflow(
					txlog.AppendedMeasureWithOverflow{
						MetricID:         req.MetricID,
						Timestamp:        measure.Timestamp,
						Value:            measure.Value,
						IsDataPageReused: report.IsDataPageReused,
						DataPageNo:       report.DataPageNo,
						IsRootChanged:    report.IsRootChanged,
						RootPageNo:       report.NewRootPageNo,
						ReusedIndexPages: report.ReusedIndexPages,
					},
					report.FileName,
					(idx+1) < len(req.Measures),
				)
				<-waitCh

				timestampsBuf = conbuf.New(nil)
				valuesBuf = conbuf.New(nil)

				timestamps = chunkenc.NewReverseTimeDeltaOfDeltaCompressor(
					timestampsBuf, 0)
				if result.MetricType == diploma.Cumulative {
					values = chunkenc.NewReverseCumulativeDeltaCompressor(
						valuesBuf, 0, result.FracDigits)
				} else {
					values = chunkenc.NewReverseInstantDeltaCompressor(
						valuesBuf, 0, result.FracDigits)
				}

				timestamps.Append(measure.Timestamp)
				values.Append(measure.Value)

				since = measure.Timestamp
			}

			until = measure.Timestamp
			untilValue = measure.Value
		}

		if len(toAppendMeasures) > 0 {
			waitCh := s.txlog.WriteAppendMeasures(
				txlog.AppendedMeasures{
					MetricID: req.MetricID,
					Measures: toAppendMeasures,
				},
				false,
			)
			<-waitCh
		}

	case NoMetric:
		return proto.ErrNoMetric

	default:
		diploma.Abort(diploma.WrongResultCodeBug, ErrWrongResultCodeBug)
	}
	return 0
}

type tryDeleteMeasuresResult struct {
	ResultCode byte
	RootPageNo uint32
}

func (s *Database) DeleteMeasures(req proto.DeleteMeasuresReq) uint16 {
	resultCh := make(chan tryDeleteMeasuresResult, 1)

	s.appendJobToWorkerQueue(tryDeleteMeasuresReq{
		MetricID: req.MetricID,
		Since:    req.Since,
		ResultCh: resultCh,
	})

	result := <-resultCh

	switch result.ResultCode {
	case NoMeasuresToDelete:
		// ok

	case DeleteFromAtreeNotNeeded:
		// регистрирую удаление в TransactionLog
		waitCh := s.txlog.WriteDeletedMeasures(txlog.DeletedMeasures{
			MetricID: req.MetricID,
		})
		<-waitCh

	case DeleteFromAtreeRequired:
		// собираю номера всех data и index страниц метрики (типа запись REDO лога).
		pageLists, err := s.atree.GetAllPages(result.RootPageNo)
		if err != nil {
			diploma.Abort(diploma.FailedAtreeRequest, err)
		}
		// регистрирую удаление в TransactionLog
		waitCh := s.txlog.WriteDeletedMeasures(txlog.DeletedMeasures{
			MetricID:       req.MetricID,
			FreeDataPages:  pageLists.DataPages,
			FreeIndexPages: pageLists.IndexPages,
		})
		<-waitCh

	case NoMetric:
		return proto.ErrNoMetric

	default:
		diploma.Abort(diploma.WrongResultCodeBug, ErrWrongResultCodeBug)
	}
	return 0
}

// SELECT

type fullScanResult struct {
	ResultCode byte
	FracDigits byte
	LastPageNo uint32
}

func (s *Database) ListAllInstantMeasures(conn net.Conn, req proto.ListAllInstantMetricMeasuresReq) error {
	responseWriter := transform.NewInstantMeasureWriter(conn, 0)

	return s.fullScan(fullScanReq{
		MetricID:       req.MetricID,
		MetricType:     diploma.Instant,
		Conn:           conn,
		ResponseWriter: responseWriter,
	})
}

func (s *Database) ListAllCumulativeMeasures(conn io.Writer, req proto.ListAllCumulativeMeasuresReq) error {
	responseWriter := transform.NewCumulativeMeasureWriter(conn, 0)

	return s.fullScan(fullScanReq{
		MetricID:       req.MetricID,
		MetricType:     diploma.Cumulative,
		Conn:           conn,
		ResponseWriter: responseWriter,
	})
}

func (s *Database) ListInstantMeasures(conn net.Conn, req proto.ListInstantMeasuresReq) error {
	if req.Since > req.Until {
		reply(conn, proto.ErrInvalidRange)
		return nil
	}

	responseWriter := transform.NewInstantMeasureWriter(conn, req.Since)

	return s.rangeScan(rangeScanReq{
		MetricID:       req.MetricID,
		MetricType:     diploma.Instant,
		Since:          req.Since,
		Until:          req.Until,
		Conn:           conn,
		ResponseWriter: responseWriter,
	})
}

func (s *Database) ListCumulativeMeasures(conn net.Conn, req proto.ListCumulativeMeasuresReq) error {
	if req.Since > req.Until {
		reply(conn, proto.ErrInvalidRange)
		return nil
	}

	responseWriter := transform.NewCumulativeMeasureWriter(conn, req.Since)

	return s.rangeScan(rangeScanReq{
		MetricID:       req.MetricID,
		MetricType:     diploma.Cumulative,
		Since:          req.Since,
		Until:          req.Until,
		Conn:           conn,
		ResponseWriter: responseWriter,
	})
}

type rangeScanResult struct {
	ResultCode byte
	FracDigits byte
	RootPageNo uint32
	LastPageNo uint32
}

func (s *Database) ListInstantPeriods(conn net.Conn, req proto.ListInstantPeriodsReq) error {
	since, until := timeBoundsOfAggregation(req.Since, req.Until, req.GroupBy, req.FirstHourOfDay)
	if since.After(until) {
		reply(conn, proto.ErrInvalidRange)
		return nil
	}

	responseWriter, err := transform.NewInstantPeriodsWriter(transform.InstantPeriodsWriterOptions{
		Dst:            conn,
		GroupBy:        req.GroupBy,
		AggregateFuncs: req.AggregateFuncs,
		FirstHourOfDay: req.FirstHourOfDay,
	})
	if err != nil {
		reply(conn, proto.ErrUnexpected)
		return nil
	}

	return s.rangeScan(rangeScanReq{
		MetricID:       req.MetricID,
		MetricType:     diploma.Instant,
		Since:          uint32(since.Unix()),
		Until:          uint32(until.Unix()),
		Conn:           conn,
		ResponseWriter: responseWriter,
	})
}

func (s *Database) ListCumulativePeriods(conn net.Conn, req proto.ListCumulativePeriodsReq) error {
	since, until := timeBoundsOfAggregation(req.Since, req.Until, req.GroupBy, req.FirstHourOfDay)
	if since.After(until) {
		reply(conn, proto.ErrInvalidRange)
		return nil
	}

	responseWriter, err := transform.NewCumulativePeriodsWriter(transform.CumulativePeriodsWriterOptions{
		Dst:            conn,
		GroupBy:        req.GroupBy,
		Since:          uint32(since.Unix()),
		FirstHourOfDay: req.FirstHourOfDay,
	})
	if err != nil {
		reply(conn, proto.ErrUnexpected)
		return nil
	}

	return s.rangeScan(rangeScanReq{
		MetricID:       req.MetricID,
		MetricType:     diploma.Cumulative,
		Since:          uint32(since.Unix()),
		Until:          uint32(until.Unix()),
		Conn:           conn,
		ResponseWriter: responseWriter,
	})
}

type rangeScanReq struct {
	MetricID       uint32
	MetricType     diploma.MetricType
	Since          uint32
	Until          uint32
	Conn           io.Writer
	ResponseWriter diploma.MeasureConsumer
}

func (s *Database) rangeScan(req rangeScanReq) error {
	resultCh := make(chan rangeScanResult, 1)

	s.appendJobToWorkerQueue(tryRangeScanReq{
		MetricID:       req.MetricID,
		Since:          req.Since,
		Until:          req.Until,
		MetricType:     req.MetricType,
		ResponseWriter: req.ResponseWriter,
		ResultCh:       resultCh,
	})

	result := <-resultCh

	switch result.ResultCode {
	case QueryDone:
		req.ResponseWriter.Close()

	case UntilFound:
		err := s.atree.ContinueRangeScan(atree.ContinueRangeScanReq{
			MetricType:     req.MetricType,
			FracDigits:     result.FracDigits,
			ResponseWriter: req.ResponseWriter,
			LastPageNo:     result.LastPageNo,
			Since:          req.Since,
		})
		s.metricRUnlock(req.MetricID)

		if err != nil {
			reply(req.Conn, proto.ErrUnexpected)
		} else {
			req.ResponseWriter.Close()
		}

	case UntilNotFound:
		err := s.atree.RangeScan(atree.RangeScanReq{
			MetricType:     req.MetricType,
			FracDigits:     result.FracDigits,
			ResponseWriter: req.ResponseWriter,
			RootPageNo:     result.RootPageNo,
			Since:          req.Since,
			Until:          req.Until,
		})
		s.metricRUnlock(req.MetricID)

		if err != nil {
			reply(req.Conn, proto.ErrUnexpected)
		} else {
			req.ResponseWriter.Close()
		}

	case NoMetric:
		reply(req.Conn, proto.ErrNoMetric)

	case WrongMetricType:
		reply(req.Conn, proto.ErrWrongMetricType)

	default:
		diploma.Abort(diploma.WrongResultCodeBug, ErrWrongResultCodeBug)
	}
	return nil
}

type fullScanReq struct {
	MetricID       uint32
	MetricType     diploma.MetricType
	Conn           io.Writer
	ResponseWriter diploma.MeasureConsumer
}

func (s *Database) fullScan(req fullScanReq) error {
	resultCh := make(chan fullScanResult, 1)

	s.appendJobToWorkerQueue(tryFullScanReq{
		MetricID:       req.MetricID,
		MetricType:     req.MetricType,
		ResponseWriter: req.ResponseWriter,
		ResultCh:       resultCh,
	})

	result := <-resultCh

	switch result.ResultCode {
	case QueryDone:
		req.ResponseWriter.Close()

	case UntilFound:
		err := s.atree.ContinueFullScan(atree.ContinueFullScanReq{
			MetricType:     req.MetricType,
			FracDigits:     result.FracDigits,
			ResponseWriter: req.ResponseWriter,
			LastPageNo:     result.LastPageNo,
		})
		s.metricRUnlock(req.MetricID)
		if err != nil {
			reply(req.Conn, proto.ErrUnexpected)
		} else {
			req.ResponseWriter.Close()
		}

	case NoMetric:
		reply(req.Conn, proto.ErrNoMetric)

	case WrongMetricType:
		reply(req.Conn, proto.ErrWrongMetricType)

	default:
		diploma.Abort(diploma.WrongResultCodeBug, ErrWrongResultCodeBug)
	}
	return nil
}

func (s *Database) ListCurrentValues(conn net.Conn, req proto.ListCurrentValuesReq) error {
	responseWriter := transform.NewCurrentValueWriter(conn)
	defer responseWriter.Close()

	resultCh := make(chan struct{})

	s.appendJobToWorkerQueue(tryListCurrentValuesReq{
		MetricIDs:      req.MetricIDs,
		ResponseWriter: responseWriter,
		ResultCh:       resultCh,
	})

	<-resultCh
	return nil
}