package database

import (
	"errors"
	"fmt"

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

type WALReplayer struct {
	walReader      *txlog.Reader
	metrics        map[uint32]*ReplayMetric
	freeIndexPages []uint32
	freeDataPages  []uint32
	indexPages     []txlog.PageToWrite
	dataPages      []txlog.PageToWrite
}

type WALReplayerOptions struct {
	WALReader      *txlog.Reader
	Metrics        map[uint32]*ReplayMetric // from snapshot
	FreeIndexPages []uint32                 // from snapshot
	FreeDataPages  []uint32                 // from snapshot
}

func NewWALReplayer(opt WALReplayerOptions) (*WALReplayer, error) {
	if opt.WALReader == nil {
		return nil, errors.New("required option: WALReader")
	}
	if opt.Metrics == nil {
		return nil, errors.New("required option: Metrics")
	}
	return &WALReplayer{
		walReader:      opt.WALReader,
		metrics:        opt.Metrics,
		freeIndexPages: opt.FreeIndexPages,
		freeDataPages:  opt.FreeDataPages,
	}, nil
}

func (s *WALReplayer) Replay() error {
	for {
		records, isLast, err := s.walReader.NextPacket()
		if err != nil {
			return err
		}

		if isLast {
			if len(records) > 0 {
				var appendRecords []txlog.WALRecordAppendMeasures
				for _, untyped := range records {
					rec, ok := untyped.(txlog.WALRecordAppendMeasures)
					if ok {
						appendRecords = append(appendRecords, rec)
					}
				}
				// prepare pages and rewrite
				indexPages, dataPages := pagesToWriteFromWALRecords(metrics, appendRecords)

				err = s.txlog.WritePagesToAtree(indexPages, dataPages)
				if err != nil {
					return err
				}
			}
			// для останнього rec - повторюємо запис сторінок
			// rewrite write pages
			//s.txlog.
			//return nil
		}

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

// func (s *WALReplayer) replayPacket(records []any, isLastPacket bool) {
// 	for _, untyped := range records {
// 		switch rec := untyped.(type) {
// 		case txlog.WALRecordAppendMeasures:
// 			s.onWALRecordAppendMeasures(rec, isLastPacket)
// 		}
// 	}
// 	return
// }

func (s *WALReplayer) replayWALRecord(untyped any) (err error) {
	switch rec := untyped.(type) {
	case txlog.AddedMetric:
		if err = s.onAddedMetric(rec); err != nil {
			return
		}

	case txlog.DeletedMetric:
		if err = s.onDeletedMetric(rec); err != nil {
			return
		}

	// 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.WALRecordAppendMeasures:
		// metric, ok := s.metrics[rec.MetricID]
		// if !ok {
		// 	qb.Abort(qb.MetricNotFoundDuringReplay, nil)
		// }
		//metric.ReplayAppendedMeasures(rec) FIX

	// 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
}

func (s *WALReplayer) onAddedMetric(rec txlog.AddedMetric) (err error) {
	_, ok := s.metrics[rec.MetricID]
	if ok {
		return fmt.Errorf("metric %d add failed: already added", rec.MetricID)
	}
	var (
		buf = make([]byte, atree.DataPageSize)
	)
	s.metrics[rec.MetricID] = &ReplayMetric{
		metricType: rec.MetricType,
		fracDigits: byte(rec.FracDigits),
		buf:        buf,
		databuf:    buf[:atree.DataPagePayloadSize],
	}
	return
}

func (s *WALReplayer) onDeletedMetric(rec txlog.DeletedMetric) error {
	_, ok := s.metrics[rec.MetricID]
	if !ok {
		return fmt.Errorf("metric %d deletion failed: not found", rec.MetricID)
	}
	delete(s.metrics, rec.MetricID)
	s.freeIndexPages = append(s.freeIndexPages, rec.FreeIndexPages...)
	s.freeDataPages = append(s.freeDataPages, rec.FreeDataPages...)
	return nil
}

func (s *WALReplayer) onAppendMeasures(rec txlog.WALRecordAppendMeasures, isLastPacket bool) {
	metric, ok := s.metrics[rec.MetricID]
	if !ok {
		qb.Abort(qb.MetricNotFoundDuringReplay, nil)
	}
	if isLastPacket {
		s.collectPagesToWrite(metric, rec)
	}
	result := metric.AppendedMeasures(rec, isLastPacket)
	//
	if isLastPacket {
		s.indexPages = append(s.indexPages, result.IndexPages...)
		s.dataPages = append(s.dataPages, result.DataPages...)
	}
	//
	s.freeIndexPages = s.freeIndexPages[:len(s.freeIndexPages)-result.ReusedIndexPagesCount]
	s.freeDataPages = s.freeDataPages[:len(s.freeDataPages)-result.ReusedDataPagesCount]
}

func (s *WALReplayer) collectPagesToWrite(metric *ReplayMetric, rec txlog.WALRecordAppendMeasures) {
	metric.ApplyHeadDataPage(rec.CompletedDataPage)

	s.dataPages = append(s.dataPages, txlog.PageToWrite{
		PageNo:  p.PageNo,
		Content: metric.buf,
	})

	for _, x := range rec.DataPages {
		s.dataPages = append(s.dataPages, txlog.PageToWrite{
			PageNo:  x.PageNo,
			Content: x.Content,
		})
	}
	//metric.ApplyHeadIndexPages(rec.ChangedIndexLevels)

}