package database

import (
	"fmt"

	qb "gordenko.dev/dima/qb"
	"gordenko.dev/dima/qb/atree"
	"gordenko.dev/dima/qb/chunkenc"
	"gordenko.dev/dima/qb/conbuf"
	"gordenko.dev/dima/qb/proto"
	"gordenko.dev/dima/qb/transform"
	"gordenko.dev/dima/qb/txlog"
)

// AddMetric - create metric in map and set Xlock, rwad - append to queue
// DeleteMetric - set Xlock
// DeleteSince - xLock (тупо редкая операция)
// Якийсь прапор поставити для pendingDelete, щоб read операції вставали в чергу

const (
	QueryDone                = 1
	UntilFound               = 2
	UntilNotFound            = 3
	RangeFound               = 15
	NoMeasures               = 16
	NoMetric                 = 4
	MetricDuplicate          = 5
	Succeed                  = 6
	NewPage                  = 7
	ExpiredMeasure           = 8
	NonMonotonicValue        = 9
	CanAppend                = 10
	WrongMetricType          = 11
	NoMeasuresToDelete       = 12
	DeleteFromAtreeNotNeeded = 13
	DeleteFromAtreeRequired  = 14
)

func (s *Database) worker() {
	for {
		select {
		case <-s.workerSignalCh:
			s.DoWork()
		}
	}
}

func (s *Database) DoWork() {
	s.mutex.Lock()
	rLocksToRelease := s.rLocksToRelease
	workerQueue := s.workerQueue
	s.rLocksToRelease = nil
	s.workerQueue = nil
	s.mutex.Unlock()

	for _, metricID := range rLocksToRelease {
		metric, ok := s.metrics[metricID]
		if !ok {
			qb.Abort(qb.NoMetricBug,
				fmt.Errorf("drainQueues: metric %d not found", metricID))
		}

		if metric.XLock {
			qb.Abort(qb.XLockBug,
				fmt.Errorf("drainQueues: xlock is set for the metric %d",
					metricID))
		}

		if metric.RLocks <= 0 {
			qb.Abort(qb.NoRLockBug,
				fmt.Errorf("drainQueues: rlock not set for the metric %d",
					metricID))
		}

		metric.RLocks--

		if len(metric.WaitQueue) > 0 {
			s.processMetricQueue(metricID, metric)
		}
	}

	for _, untyped := range workerQueue {
		switch req := untyped.(type) {
		case tryAppendMeasuresReq:
			s.tryAppendMeasures(req)

		case txlog.Changes:
			s.applyChanges(req) // all metrics only

		case tryListCurrentValuesReq:
			s.tryListCurrentValues(req) // all metrics only

		case tryRangeScanReq:
			s.tryRangeScan(req)

		case tryFullScanReq:
			s.tryFullScan(req)

		case tryAddMetricReq:
			s.tryAddMetric(req)

		case tryDeleteMetricReq:
			s.tryDeleteMetric(req)

		case tryDeleteMeasuresReq:
			s.tryDeleteMeasures(req)

		case tryGetMetricReq:
			s.tryGetMetric(req)

		default:
			qb.Abort(qb.UnknownWorkerQueueItemBug,
				fmt.Errorf("bug: unknown worker queue item type %T", req))
		}
	}
}

// суть у тому що треба запускати запити, пока не зустріну XLock
func (s *Database) processMetricQueue(metricID uint32, metric *_metric) {
	if len(metric.WaitQueue) == 0 {
		return
	}

	for _, untyped := range metric.WaitQueue {
		switch req := untyped.(type) {
		case tryRangeScanReq:
			metric.StartRangeScan(req)

		case tryFullScanReq:
			metric.StartFullScan(req)

		case tryGetMetricReq:
			s.tryGetMetric(req)

		case tryAppendMeasuresReq:
			metric.StartAppendMeasures(req, s.txlog.Append)

		case tryDeleteMetricReq:
			s.startDeleteMetric(metric, req)

		case tryDeleteMeasuresReq:
			s.startDeleteMeasures(metric, req)

		default:
			qb.Abort(qb.UnknownMetricWaitQueueItemBug,
				fmt.Errorf("bug: unknown metric wait queue item type %T", req))
		}
	}
}

type tryAddMetricReq struct {
	MetricID uint32
	ResultCh chan byte
}

func (s *Database) tryAddMetric(req tryAddMetricReq) {
	_, ok := s.metrics[req.MetricID]
	if ok {
		req.ResultCh <- MetricDuplicate
		return
	}
	req.ResultCh <- Succeed // new

	// lockEntry, ok := s.metricLockEntries[req.MetricID]
	// if ok {
	// 	lockEntry.WaitQueue = append(lockEntry.WaitQueue, req)
	// } else {
	// 	s.metricLockEntries[req.MetricID] = &metricLockEntry{
	// 		XLock: true,
	// 	}
	// 	req.ResultCh <- Succeed
	// }
}

func (s *Database) processTryAddMetricReqsImmediatelyAfterDelete(reqs []tryAddMetricReq) {
	if len(reqs) == 0 {
		return
	}
	var (
		req       = reqs[0]
		waitQueue []any
	)
	if len(reqs) > 1 {
		for _, req := range reqs[1:] {
			waitQueue = append(waitQueue, req)
		}
	}
	// FIX
	// s.metricLockEntries[req.MetricID] = &metricLockEntry{
	// 	XLock:     true,
	// 	WaitQueue: waitQueue,
	// }
	req.ResultCh <- Succeed
}

type tryGetMetricReq struct {
	MetricID uint32
	ResultCh chan Metric
}

func (s *Database) tryGetMetric(req tryGetMetricReq) {
	metric, ok := s.metrics[req.MetricID]
	if ok {
		req.ResultCh <- Metric{
			ResultCode: Succeed,
			MetricType: metric.MetricType,
			FracDigits: metric.FracDigits,
		}
	} else {
		req.ResultCh <- Metric{
			ResultCode: NoMetric,
		}
	}
}

type tryDeleteMetricReq struct {
	MetricID uint32
	ResultCh chan tryDeleteMetricResult
}

func (s *Database) tryDeleteMetric(req tryDeleteMetricReq) {
	// FIX
	// metric, ok := s.metrics[req.MetricID]
	// if !ok {
	// 	req.ResultCh <- tryDeleteMetricResult{
	// 		ResultCode: NoMetric,
	// 	}
	// 	return
	// }

	// lockEntry, ok := s.metricLockEntries[req.MetricID]
	// if ok {
	// 	lockEntry.WaitQueue = append(lockEntry.WaitQueue, req)
	// } else {
	// 	s.startDeleteMetric(metric, req)
	// }
}

func (s *Database) startDeleteMetric(metric *_metric, req tryDeleteMetricReq) {
	// FIX
	// s.metricLockEntries[req.MetricID] = &metricLockEntry{
	// 	XLock: true,
	// }
	// req.ResultCh <- tryDeleteMetricResult{
	// 	ResultCode: Succeed,
	// 	RootPageNo: metric.RootPageNo,
	// }
}

type tryDeleteMeasuresReq struct {
	MetricID uint32
	Since    uint32
	ResultCh chan tryDeleteMeasuresResult
}

func (s *Database) tryDeleteMeasures(req tryDeleteMeasuresReq) {
	// FIX
	// metric, ok := s.metrics[req.MetricID]
	// if !ok {
	// 	req.ResultCh <- tryDeleteMeasuresResult{
	// 		ResultCode: NoMetric,
	// 	}
	// 	return
	// }

	// if metric.Since == 0 || (req.Since > 0 && metric.Until < req.Since) {
	// 	req.ResultCh <- tryDeleteMeasuresResult{
	// 		ResultCode: NoMeasuresToDelete,
	// 	}
	// }

	// lockEntry, ok := s.metricLockEntries[req.MetricID]
	// if ok {
	// 	lockEntry.WaitQueue = append(lockEntry.WaitQueue, req)
	// } else {
	// 	s.startDeleteMeasures(metric, req)
	// }
}

func (s *Database) startDeleteMeasures(metric *_metric, req tryDeleteMeasuresReq) {
	// FIX
	// s.metricLockEntries[req.MetricID] = &metricLockEntry{
	// 	XLock: true,
	// }

	// if metric.RootPageNo > 0 {
	// 	req.ResultCh <- tryDeleteMeasuresResult{
	// 		ResultCode: DeleteFromAtreeRequired,
	// 		RootPageNo: metric.RootPageNo,
	// 	}
	// } else {
	// 	req.ResultCh <- tryDeleteMeasuresResult{
	// 		ResultCode: DeleteFromAtreeNotNeeded,
	// 	}
	// }
}

func (s *Database) finAppendMeasures(rec txlog.AppendMeasuresSummary) {
	metric, ok := s.metrics[rec.MetricID]
	if !ok {
		qb.Abort(qb.NoMetricBug,
			fmt.Errorf("finAppendMeasures: metric %d not found",
				rec.MetricID))
	}
	metric.FinAppendMeasures(rec)
}

type tryAppendMeasuresReq struct {
	MetricID uint32
	Measures []proto.Measure
	ResultCh chan tryAppendMeasuresResult
}

func (s *Database) tryAppendMeasures(req tryAppendMeasuresReq) {
	metric, ok := s.metrics[req.MetricID]
	if !ok {
		req.ResultCh <- tryAppendMeasuresResult{
			ResultCode: NoMetric,
		}
		return
	}
	if metric.XLock {
		metric.WaitQueue = append(metric.WaitQueue, req)
		return
	}
	metric.StartAppendMeasures(req, s.txlog.Append)
}

type tryRangeScanReq struct {
	MetricID       uint32
	Since          uint32
	Until          uint32
	MetricType     qb.MetricType
	ResponseWriter atree.WorkerMeasureConsumer
	ResultCh       chan rangeScanResult
}

func (s *Database) tryRangeScan(req tryRangeScanReq) {
	metric, ok := s.metrics[req.MetricID]
	if !ok {
		req.ResultCh <- rangeScanResult{
			ResultCode: NoMetric,
		}
		return
	}
	if metric.MetricType != req.MetricType {
		req.ResultCh <- rangeScanResult{
			ResultCode: WrongMetricType,
		}
		return
	}

	if metric.XLock {
		metric.WaitQueue = append(metric.WaitQueue, req)
		return
	}

	metric.StartRangeScan(req)
}

type tryFullScanReq struct {
	MetricID       uint32
	MetricType     qb.MetricType
	ResponseWriter atree.WorkerMeasureConsumer
	ResultCh       chan fullScanResult
}

func (s *Database) tryFullScan(req tryFullScanReq) {
	metric, ok := s.metrics[req.MetricID]
	if !ok {
		req.ResultCh <- fullScanResult{
			ResultCode: NoMetric,
		}
		return
	}
	if metric.MetricType != req.MetricType {
		req.ResultCh <- fullScanResult{
			ResultCode: WrongMetricType,
		}
		return
	}

	if metric.XLock {
		metric.WaitQueue = append(metric.WaitQueue, req)
		return
	}
	metric.StartFullScan(req)
}

type tryListCurrentValuesReq struct {
	MetricIDs      []uint32
	ResponseWriter *transform.CurrentValueWriter
	ResultCh       chan struct{}
}

func (s *Database) tryListCurrentValues(req tryListCurrentValuesReq) {
	for _, metricID := range req.MetricIDs {
		metric, ok := s.metrics[metricID]
		if ok {
			req.ResponseWriter.BufferValue(transform.CurrentValue{
				MetricID:  metricID,
				Timestamp: metric.Until,
				Value:     metric.UntilValue,
			})
		}
	}
	req.ResultCh <- struct{}{}
}

///////////////////////////////////////////////////////

func (s *Database) applyChanges(req txlog.Changes) {
	for _, untyped := range req.Records {
		switch rec := untyped.(type) {
		case txlog.AddedMetric:
			s.addMetric(rec)

		case txlog.DeletedMetric:
			s.deleteMetric(rec)

		// case txlog.AppendedMeasure:
		// 	s.appendMeasure(rec)

		case txlog.AppendMeasuresSummary:
			s.finAppendMeasures(rec)

		// case txlog.AppendedMeasureWithOverflowExtended:
		// 	s.appendMeasureAfterOverflow(rec)

		case txlog.DeletedMeasures:
			s.deleteMeasures(rec)
		}
	}

	if req.MetricsCh != nil {
		waitCh := make(chan struct{})
		req.MetricsCh <- txlog.MetricsState{
			Metrics: s.createMetricsState(),
			WaitCh:  waitCh,
		}
		// чекаю поки txlog запише снапшот, а отже можна змінювати буфери
		<-waitCh
	}
}

func (s *Database) createMetricsState() (metrics []txlog.Metric) {
	for metricID, metric := range s.metrics {
		x := txlog.Metric{
			MetricID:   metricID,
			MetricType: metric.MetricType,
			FracDigits: metric.FracDigits,
			LastPageNo: metric.LastPageNo,
			Since:      metric.Since,
			SinceValue: metric.SinceValue,
			Until:      metric.Until,      // ?
			UntilValue: metric.UntilValue, // ?
		}
		x.Timestamps, x.TimestampsSize = metric.Timestamps.Snapshot()
		x.Values, x.ValuesSize = metric.Values.Snapshot()
		metrics = append(metrics, x)
	}
	return
}

func (s *Database) addMetric(rec txlog.AddedMetric) {
	// fix lock
	_, ok := s.metrics[rec.MetricID]
	if ok {
		qb.Abort(qb.MetricAddedBug,
			fmt.Errorf("addMetric: metric %d already added",
				rec.MetricID))
	}

	// if !lockEntry.XLock {
	// 	qb.Abort(qb.NoXLockBug,
	// 		fmt.Errorf("addMetric: xlock not set for the metric %d",
	// 			rec.MetricID))
	// }

	var (
		values        qb.ValueCompressor
		timestampsBuf = conbuf.New(nil)
		valuesBuf     = conbuf.New(nil)
	)

	if rec.MetricType == qb.Cumulative {
		values = chunkenc.NewCumulativeDeltaCompressor(
			valuesBuf, 0, byte(rec.FracDigits))
	} else {
		values = chunkenc.NewInstantDeltaCompressor(
			valuesBuf, 0, byte(rec.FracDigits))
	}

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

	lockEntry.XLock = false
	delete(s.metricLockEntries, rec.MetricID)
}

func (s *Database) deleteMetric(rec txlog.DeletedMetric) {
	metric, ok := s.metrics[rec.MetricID]
	if !ok {
		qb.Abort(qb.NoMetricBug,
			fmt.Errorf("deleteMetric: metric %d not found",
				rec.MetricID))
	}

	if !metric.XLock {
		qb.Abort(qb.NoXLockBug,
			fmt.Errorf("deleteMetric: xlock not set for the metric %d",
				rec.MetricID))
	}

	var addMetricReqs []tryAddMetricReq

	if len(metric.WaitQueue) > 0 {
		for _, untyped := range metric.WaitQueue {
			switch req := untyped.(type) {
			// case tryAppendMeasureReq:
			// 	req.ResultCh <- tryAppendMeasureResult{
			// 		MetricID:   req.MetricID,
			// 		ResultCode: NoMetric,
			// 	}

			case tryRangeScanReq:
				req.ResultCh <- rangeScanResult{
					ResultCode: NoMetric,
				}

			case tryFullScanReq:
				req.ResultCh <- fullScanResult{
					ResultCode: NoMetric,
				}

			case tryAddMetricReq:
				addMetricReqs = append(addMetricReqs, req)

			case tryDeleteMetricReq:
				req.ResultCh <- tryDeleteMetricResult{
					ResultCode: NoMetric,
				}

			case tryDeleteMeasuresReq:
				req.ResultCh <- tryDeleteMeasuresResult{
					ResultCode: NoMetric,
				}

			case tryGetMetricReq:
				req.ResultCh <- Metric{
					ResultCode: NoMetric,
				}

			default:
				qb.Abort(qb.UnknownMetricWaitQueueItemBug,
					fmt.Errorf("bug: unknown metric wait queue item type %T", req))
			}
		}
	}
	delete(s.metrics, rec.MetricID)

	// ADD in txlog
	// if len(rec.FreePageNumbers) > 0 {
	// 	s.freeList.AddPages(rec.FreePageNumbers)
	// }

	if len(addMetricReqs) > 0 {
		s.processTryAddMetricReqsImmediatelyAfterDelete(addMetricReqs)
	}
}

func (s *Database) deleteMeasures(rec txlog.DeletedMeasures) {
	metric, ok := s.metrics[rec.MetricID]
	if !ok {
		qb.Abort(qb.NoMetricBug,
			fmt.Errorf("deleteMeasures: metric %d not found",
				rec.MetricID))
	}

	if !metric.XLock {
		qb.Abort(qb.NoXLockBug,
			fmt.Errorf("deleteMeasures: xlock not set for the metric %d",
				rec.MetricID))
	}
	metric.DeleteMeasures()
	metric.XLock = false
	// FIX add in txlog
	// if len(rec.FreePageNumbers) > 0 {
	// 	s.freeList.AddPages(rec.FreePageNumbers)
	// }
	s.doAfterReleaseXLock(rec.MetricID, metric)
}

func (s *Database) doAfterReleaseXLock(metricID uint32, metric *_metric) {
	if len(metric.WaitQueue) > 0 {
		s.processMetricQueue(metricID, metric)
	}
}