//                           _       _
// __      _____  __ ___   ___  __ _| |_ ___
// \ \ /\ / / _ \/ _` \ \ / / |/ _` | __/ _ \
//  \ V  V /  __/ (_| |\ V /| | (_| | ||  __/
//   \_/\_/ \___|\__,_| \_/ |_|\__,_|\__\___|
//
//  Copyright © 2016 - 2024 Weaviate B.V. All rights reserved.
//
//  CONTACT: hello@weaviate.io
//

package db

import (
	"context"
	"fmt"

	"github.com/go-openapi/strfmt"
	"github.com/pkg/errors"
	"github.com/weaviate/weaviate/entities/additional"
	"github.com/weaviate/weaviate/entities/schema"
	"github.com/weaviate/weaviate/entities/storobj"
	"github.com/weaviate/weaviate/usecases/objects"
)

type batchQueue struct {
	objects       []*storobj.Object
	originalIndex []int
}

func (db *DB) BatchPutObjects(ctx context.Context, objs objects.BatchObjects,
	repl *additional.ReplicationProperties,
) (objects.BatchObjects, error) {
	objectByClass := make(map[string]batchQueue)
	indexByClass := make(map[string]*Index)

	if err := db.memMonitor.CheckAlloc(estimateBatchMemory(objs)); err != nil {
		return nil, fmt.Errorf("cannot process batch: %w", err)
	}

	for _, item := range objs {
		if item.Err != nil {
			// item has a validation error or another reason to ignore
			continue
		}
		queue := objectByClass[item.Object.Class]
		queue.objects = append(queue.objects, storobj.FromObject(item.Object, item.Vector))
		queue.originalIndex = append(queue.originalIndex, item.OriginalIndex)
		objectByClass[item.Object.Class] = queue
	}

	// wrapped by func to acquire and safely release indexLock only for duration of loop
	func() {
		db.indexLock.RLock()
		defer db.indexLock.RUnlock()

		for class, queue := range objectByClass {
			index, ok := db.indices[indexID(schema.ClassName(class))]
			if !ok {
				msg := fmt.Sprintf("could not find index for class %v. It might have been deleted in the meantime", class)
				db.logger.Warn(msg)
				for _, origIdx := range queue.originalIndex {
					if origIdx >= len(objs) {
						db.logger.Errorf(
							"batch add queue index out of bounds. len(objs) == %d, queue.originalIndex == %d",
							len(objs), origIdx)
						break
					}
					objs[origIdx].Err = fmt.Errorf(msg)
				}
				continue
			}
			index.dropIndex.RLock()
			indexByClass[class] = index
		}
	}()

	// safely release remaining locks (in case of panic)
	defer func() {
		for _, index := range indexByClass {
			if index != nil {
				index.dropIndex.RUnlock()
			}
		}
	}()

	for class, index := range indexByClass {
		queue := objectByClass[class]
		errs := index.putObjectBatch(ctx, queue.objects, repl)
		// remove index from map to skip releasing its lock in defer
		indexByClass[class] = nil
		index.dropIndex.RUnlock()
		for i, err := range errs {
			if err != nil {
				objs[queue.originalIndex[i]].Err = err
			}
		}
	}

	return objs, nil
}

func (db *DB) AddBatchReferences(ctx context.Context, references objects.BatchReferences,
	repl *additional.ReplicationProperties,
) (objects.BatchReferences, error) {
	refByClass := make(map[schema.ClassName]objects.BatchReferences)
	indexByClass := make(map[schema.ClassName]*Index)

	for _, item := range references {
		if item.Err != nil {
			// item has a validation error or another reason to ignore
			continue
		}
		refByClass[item.From.Class] = append(refByClass[item.From.Class], item)
	}

	// wrapped by func to acquire and safely release indexLock only for duration of loop
	func() {
		db.indexLock.RLock()
		defer db.indexLock.RUnlock()

		for class, queue := range refByClass {
			index, ok := db.indices[indexID(class)]
			if !ok {
				for _, item := range queue {
					references[item.OriginalIndex].Err = fmt.Errorf("could not find index for class %v. It might have been deleted in the meantime", class)
				}
				continue
			}
			index.dropIndex.RLock()
			indexByClass[class] = index
		}
	}()

	// safely release remaining locks (in case of panic)
	defer func() {
		for _, index := range indexByClass {
			if index != nil {
				index.dropIndex.RUnlock()
			}
		}
	}()

	for class, index := range indexByClass {
		queue := refByClass[class]
		errs := index.AddReferencesBatch(ctx, queue, repl)
		// remove index from map to skip releasing its lock in defer
		indexByClass[class] = nil
		index.dropIndex.RUnlock()
		for i, err := range errs {
			if err != nil {
				references[queue[i].OriginalIndex].Err = err
			}
		}
	}

	return references, nil
}

func (db *DB) BatchDeleteObjects(ctx context.Context, params objects.BatchDeleteParams,
	repl *additional.ReplicationProperties, tenant string,
) (objects.BatchDeleteResult, error) {
	// get index for a given class
	className := params.ClassName
	idx := db.GetIndex(className)
	if idx == nil {
		return objects.BatchDeleteResult{}, errors.Errorf("cannot find index for class %v", className)
	}

	// find all DocIDs in all shards that match the filter
	shardDocIDs, err := idx.findUUIDs(ctx, params.Filters, tenant)
	if err != nil {
		return objects.BatchDeleteResult{}, errors.Wrapf(err, "cannot find objects")
	}
	// prepare to be deleted list of DocIDs from all shards
	toDelete := map[string][]strfmt.UUID{}
	limit := db.config.QueryMaximumResults

	matches := int64(0)
	for shardName, docIDs := range shardDocIDs {
		docIDsLength := int64(len(docIDs))
		if matches <= limit {
			if matches+docIDsLength <= limit {
				toDelete[shardName] = docIDs
			} else {
				toDelete[shardName] = docIDs[:limit-matches]
			}
		}
		matches += docIDsLength
	}
	// delete the DocIDs in given shards
	deletedObjects, err := idx.batchDeleteObjects(ctx, toDelete, params.DryRun, repl)
	if err != nil {
		return objects.BatchDeleteResult{}, errors.Wrapf(err, "cannot delete objects")
	}

	result := objects.BatchDeleteResult{
		Matches: matches,
		Limit:   db.config.QueryMaximumResults,
		DryRun:  params.DryRun,
		Objects: deletedObjects,
	}
	return result, nil
}

func estimateBatchMemory(objs objects.BatchObjects) int64 {
	var sum int64
	for _, item := range objs {
		// Note: This is very much oversimplified. It assumes that we always need
		// the footprint of the full vector and it assumes a fixed overhead of 30B
		// per vector. In reality this depends on the HNSW settings - and possibly
		// in the future we might have completely different index types.
		//
		// However, in the meantime this should be a fairly reasonable estimate, as
		// it's not meant to fail exactly on the last available byte, but rather
		// prevent OOM crashes. Given the fuzziness and async style of the
		// memtrackinga somewhat decent estimate should be go good enough.
		sum += int64(len(item.Vector)*4 + 30)
	}

	return sum
}