package shard

import (
	"context"
	"strconv"

	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"
)

// RngPrm groups the parameters of GetRange operation.
type RngPrm struct {
	ln uint64

	off uint64

	addr oid.Address

	skipMeta bool
}

// RngRes groups the resulting values of GetRange operation.
type RngRes struct {
	obj     *object.Object
	hasMeta bool
}

// SetAddress is a Rng option to set the address of the requested object.
//
// Option is required.
func (p *RngPrm) SetAddress(addr oid.Address) {
	p.addr = addr
}

// SetRange is a GetRange option to set range of requested payload data.
func (p *RngPrm) SetRange(off uint64, ln uint64) {
	p.off, p.ln = off, ln
}

// SetIgnoreMeta is a Get option try to fetch object from blobstor directly,
// without accessing metabase.
func (p *RngPrm) SetIgnoreMeta(ignore bool) {
	p.skipMeta = ignore
}

// Object returns the requested object part.
//
// Instance payload contains the requested range of the original object.
func (r RngRes) Object() *object.Object {
	return r.obj
}

// HasMeta returns true if info about the object was found in the metabase.
func (r RngRes) HasMeta() bool {
	return r.hasMeta
}

// GetRange reads part of an object from shard.
//
// Returns any error encountered that
// did not allow to completely read the object part.
//
// Returns ErrRangeOutOfBounds if the requested object range is out of bounds.
// Returns an error of type apistatus.ObjectNotFound if the requested object is missing.
// Returns an error of type apistatus.ObjectAlreadyRemoved if the requested object has been marked as removed in shard.
// Returns the object.ErrObjectIsExpired if the object is presented but already expired.
// Returns the ErrShardDisabled if the shard is disabled.
func (s *Shard) GetRange(ctx context.Context, prm RngPrm) (RngRes, error) {
	ctx, span := tracing.StartSpanFromContext(ctx, "Shard.GetRange",
		trace.WithAttributes(
			attribute.String("shard_id", s.ID().String()),
			attribute.String("address", prm.addr.EncodeToString()),
			attribute.Bool("skip_meta", prm.skipMeta),
			attribute.String("offset", strconv.FormatUint(prm.off, 10)),
			attribute.String("length", strconv.FormatUint(prm.ln, 10)),
		))
	defer span.End()

	s.m.RLock()
	defer s.m.RUnlock()

	if s.info.Mode.Disabled() {
		return RngRes{}, ErrShardDisabled
	}

	cb := func(stor *blobstor.BlobStor, id []byte) (*object.Object, error) {
		var getRngPrm common.GetRangePrm
		getRngPrm.Address = prm.addr
		getRngPrm.Range.SetOffset(prm.off)
		getRngPrm.Range.SetLength(prm.ln)
		getRngPrm.StorageID = id

		res, err := stor.GetRange(ctx, getRngPrm)
		if err != nil {
			return nil, err
		}

		obj := object.New()
		obj.SetPayload(res.Data)

		return obj, nil
	}

	wc := func(c writecache.Cache) (*object.Object, error) {
		res, err := c.Get(ctx, prm.addr)
		if err != nil {
			return nil, err
		}

		payload := res.Payload()
		from := prm.off
		to := from + prm.ln
		if pLen := uint64(len(payload)); to < from || pLen < from || pLen < to {
			return nil, logicerr.Wrap(apistatus.ObjectOutOfRange{})
		}

		obj := object.New()
		obj.SetPayload(payload[from:to])
		return obj, nil
	}

	skipMeta := prm.skipMeta || s.info.Mode.NoMetabase()
	obj, hasMeta, err := s.fetchObjectData(ctx, prm.addr, skipMeta, cb, wc)

	return RngRes{
		obj:     obj,
		hasMeta: hasMeta,
	}, err
}