package blobovniczatree

import (
	"context"
	"encoding/hex"
	"fmt"
	"strconv"
	"time"

	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobovnicza"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
	tracingPkg "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/tracing"
	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client"
	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"
	"go.uber.org/zap"
)

// GetRange reads range of object payload data from blobovnicza tree.
//
// If blobocvnicza ID is specified, only this blobovnicza is processed.
// Otherwise, all Blobovniczas are processed descending weight.
func (b *Blobovniczas) GetRange(ctx context.Context, prm common.GetRangePrm) (res common.GetRangeRes, err error) {
	var (
		startedAt = time.Now()
		success   = false
		size      = 0
	)
	defer func() {
		b.metrics.GetRange(time.Since(startedAt), size, success, prm.StorageID != nil)
	}()

	ctx, span := tracing.StartSpanFromContext(ctx, "Blobovniczas.GetRange",
		trace.WithAttributes(
			attribute.String("path", b.rootPath),
			attribute.String("address", prm.Address.EncodeToString()),
			attribute.String("storage_id", hex.EncodeToString(prm.StorageID)),
			attribute.String("offset", strconv.FormatUint(prm.Range.GetOffset(), 10)),
			attribute.String("length", strconv.FormatUint(prm.Range.GetLength(), 10)),
		))
	defer span.End()

	if prm.StorageID != nil {
		id := NewIDFromBytes(prm.StorageID)
		shBlz := b.getBlobovnicza(id.Path())
		blz, err := shBlz.Open()
		if err != nil {
			return common.GetRangeRes{}, err
		}
		defer shBlz.Close()

		res, err := b.getObjectRange(ctx, blz, prm)
		if err == nil {
			size = len(res.Data)
			success = true
		}
		return res, err
	}

	objectFound := false

	err = b.iterateSortedDBPaths(ctx, prm.Address, func(p string) (bool, error) {
		res, err = b.getRangeFromLevel(ctx, prm, p)
		if err != nil {
			outOfBounds := isErrOutOfRange(err)
			if !outOfBounds && !client.IsErrObjectNotFound(err) {
				b.log.Debug(logs.BlobovniczatreeCouldNotGetObjectFromLevel,
					zap.String("level", p),
					zap.String("error", err.Error()),
					zap.String("trace_id", tracingPkg.GetTraceID(ctx)))
			}
			if outOfBounds {
				return true, err
			}
		}

		objectFound = err == nil

		// abort iterator if found, otherwise process all Blobovniczas
		return err == nil, nil
	})

	if err == nil && !objectFound {
		// not found in any blobovnicza
		return common.GetRangeRes{}, logicerr.Wrap(new(apistatus.ObjectNotFound))
	}

	if err == nil {
		success = true
		size = len(res.Data)
	}

	return
}

// tries to read range of object payload data from particular blobovnicza.
//
// returns error if object could not be read from any blobovnicza of the same level.
func (b *Blobovniczas) getRangeFromLevel(ctx context.Context, prm common.GetRangePrm, blzPath string) (common.GetRangeRes, error) {
	// open blobovnicza (cached inside)
	shBlz := b.getBlobovnicza(blzPath)
	blz, err := shBlz.Open()
	if err != nil {
		return common.GetRangeRes{}, err
	}
	defer shBlz.Close()

	return b.getObjectRange(ctx, blz, prm)
}

// reads range of object payload data from blobovnicza and returns GetRangeSmallRes.
func (b *Blobovniczas) getObjectRange(ctx context.Context, blz *blobovnicza.Blobovnicza, prm common.GetRangePrm) (common.GetRangeRes, error) {
	var gPrm blobovnicza.GetPrm
	gPrm.SetAddress(prm.Address)

	// we don't use GetRange call for now since blobovnicza
	// stores data that is compressed on BlobStor side.
	// If blobovnicza learns to do the compression itself,
	// we can start using GetRange.
	res, err := blz.Get(ctx, gPrm)
	if err != nil {
		return common.GetRangeRes{}, err
	}

	// decompress the data
	data, err := b.compression.Decompress(res.Object())
	if err != nil {
		return common.GetRangeRes{}, fmt.Errorf("could not decompress object data: %w", err)
	}

	// unmarshal the object
	obj := objectSDK.New()
	if err := obj.Unmarshal(data); err != nil {
		return common.GetRangeRes{}, fmt.Errorf("could not unmarshal the object: %w", err)
	}

	from := prm.Range.GetOffset()
	to := from + prm.Range.GetLength()
	payload := obj.Payload()

	if pLen := uint64(len(payload)); to < from || pLen < from || pLen < to {
		return common.GetRangeRes{}, logicerr.Wrap(new(apistatus.ObjectOutOfRange))
	}

	return common.GetRangeRes{
		Data: payload[from:to],
	}, nil
}