package blobstor

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

	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
	tracingPkg "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/tracing"
	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"
	"go.uber.org/zap"
)

// Exists checks if the object is presented in BLOB storage.
//
// Returns any error encountered that did not allow
// to completely check object existence.
func (b *BlobStor) Exists(ctx context.Context, prm common.ExistsPrm) (common.ExistsRes, error) {
	var (
		exists    = false
		startedAt = time.Now()
	)
	defer func() {
		b.metrics.Exists(time.Since(startedAt), exists, prm.StorageID != nil)
	}()

	ctx, span := tracing.StartSpanFromContext(ctx, "BlobStor.Exists",
		trace.WithAttributes(
			attribute.String("address", prm.Address.EncodeToString()),
			attribute.String("storage_id", hex.EncodeToString(prm.StorageID)),
		))
	defer span.End()

	b.modeMtx.RLock()
	defer b.modeMtx.RUnlock()

	if prm.StorageID != nil {
		if len(prm.StorageID) == 0 {
			res, err := b.storage[len(b.storage)-1].Storage.Exists(ctx, prm)
			exists = err == nil && res.Exists
			return res, err
		}
		res, err := b.storage[0].Storage.Exists(ctx, prm)
		exists = err == nil && res.Exists
		return res, err
	}

	// If there was an error during existence check below,
	// it will be returned unless object was found in blobovnicza.
	// Otherwise, it is logged and the latest error is returned.
	// FSTree    | Blobovnicza | Behaviour
	// found     | (not tried) | return true, nil
	// not found | any result  | return the result
	// error     | found       | log the error, return true, nil
	// error     | not found   | return the error
	// error     | error       | log the first error, return the second
	var errors []error
	for i := range b.storage {
		res, err := b.storage[i].Storage.Exists(ctx, prm)
		if err == nil && res.Exists {
			exists = true
			return res, nil
		} else if err != nil {
			errors = append(errors, err)
		}
	}

	if len(errors) == 0 {
		return common.ExistsRes{}, nil
	}

	for _, err := range errors[:len(errors)-1] {
		b.log.Warn(ctx, logs.BlobstorErrorOccurredDuringObjectExistenceChecking,
			zap.Stringer("address", prm.Address),
			zap.Error(err),
			zap.String("trace_id", tracingPkg.GetTraceID(ctx)))
	}

	return common.ExistsRes{}, errors[len(errors)-1]
}