package storage

import (
	"fmt"

	bin "gordenko.dev/dima/bin/little"
	"gordenko.dev/dima/qb"
	"gordenko.dev/dima/qb/enc"
)

// func (s *BackwardCursor) makeDecompressors() error {
// 	timestampsSize, _ := bin.GetUint16(s.pageData[timestampsSizeIdx:])
// 	valuesSize, _ := bin.GetUint16(s.pageData[valuesSizeIdx:])

// 	payloadSize := timestampsSize + valuesSize

// 	if payloadSize > dataFooterIdx {
// 		return fmt.Errorf("corrupted data page %d: timestamps + values size %d gt payload size",
// 			s.pageNo, payloadSize)
// 	}

// 	s.timestampDecompressor = enc.NewTimeDeltaDecompressor(
// 		s.pageData[:timestampsSize],
// 	)

// 	vbuf := s.pageData[timestampsSize : timestampsSize+valuesSize]

// 	switch s.metricType {
// 	case qb.Instant:
// 		s.valueDecompressor = enc.NewInstantDeltaDecompressor(
// 			vbuf, s.fracDigits)

// 	case qb.Cumulative:
// 		s.valueDecompressor = enc.NewCumulativeDeltaDecompressor(
// 			vbuf, s.fracDigits)

// 	default:
// 		return fmt.Errorf("bug: wrong metricType %d", s.metricType)
// 	}
// 	return nil
// }

func makeDecompressors(pageData []byte, metricType qb.MetricType, fracDigits byte) (
	qb.TimestampDecompressor, qb.ValueDecompressor, error,
) {

	valuesSize, _ := bin.GetUint16(pageData[valuesSizeIdx:])

	payloadSize := timestampsSize + valuesSize

	if payloadSize > dataFooterIdx {
		return nil, nil, fmt.Errorf("corrupted: timestamps + values size %d > payload size",
			payloadSize)
	}

	timestampDecompressor := enc.NewTimeDeltaDecompressor(
		pageData[:timestampsSize],
	)

	vbuf := pageData[timestampsSize : timestampsSize+valuesSize]

	var valueDecompressor qb.ValueDecompressor
	switch metricType {
	case qb.Instant:
		valueDecompressor = enc.NewInstantDeltaDecompressor(
			vbuf, fracDigits)

	case qb.Cumulative:
		valueDecompressor = enc.NewCumulativeDeltaDecompressor(
			vbuf, fracDigits)

	default:
		return nil, nil, fmt.Errorf("bug: wrong metricType %d", metricType)
	}
	return timestampDecompressor, valueDecompressor, nil
	return nil, nil, nil
}

func CreateTimeDeltaDecompressor(page []byte) qb.TimestampDecompressor {
	size, _ := bin.GetUint16(page[timestampsSizeIdx:])
	pos := DataPagePayloadSize - int(size)
	d := enc.NewTimeDeltaDecompressor()
	d.RestoreFromEnd(page[pos:DataPagePayloadSize])
	return d
}

func CreateValueDeltaDecompressor(page []byte, metricType qb.MetricType, fracDigits byte) qb.ValueDecompressor {
	size, _ := bin.GetUint16(page[valuesSizeIdx:])
	d := enc.NewValueDeltaDecompressor(metricType, fracDigits)
	d.RestoreFromEnd(page[:size])
	return d
}