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

package replica

import (
	"sort"

	"github.com/go-openapi/strfmt"
	"github.com/weaviate/weaviate/entities/storobj"
	"github.com/weaviate/weaviate/usecases/objects"
)

// indexedBatch holds an indexed list of objects
type indexedBatch struct {
	Data []*storobj.Object
	// Index is z-index used to maintain object's order
	Index []int
}

// createBatch creates indexedBatch from xs
func createBatch(xs []*storobj.Object) indexedBatch {
	var bi indexedBatch
	bi.Data = xs
	bi.Index = make([]int, len(xs))
	for i := 0; i < len(xs); i++ {
		bi.Index[i] = i
	}
	return bi
}

// cluster data object by shard
func cluster(bi indexedBatch) []shardPart {
	index := bi.Index
	data := bi.Data
	sort.Slice(index, func(i, j int) bool {
		return data[index[i]].BelongsToShard < data[index[j]].BelongsToShard
	})
	clusters := make([]shardPart, 0, 16)
	// partition
	cur := data[index[0]]
	j := 0
	for i := 1; i < len(index); i++ {
		if data[index[i]].BelongsToShard == cur.BelongsToShard {
			continue
		}
		clusters = append(clusters, shardPart{
			Shard: cur.BelongsToShard,
			Node:  cur.BelongsToNode, Data: data,
			Index: index[j:i],
		})
		j = i
		cur = data[index[j]]

	}
	clusters = append(clusters, shardPart{
		Shard: cur.BelongsToShard,
		Node:  cur.BelongsToNode, Data: data,
		Index: index[j:],
	})
	return clusters
}

// shardPart represents a data partition belonging to a physical shard
type shardPart struct {
	Shard string // one-to-one mapping between Shard and Node
	Node  string

	Data  []*storobj.Object
	Index []int // index for data
}

func (b *shardPart) ObjectIDs() []strfmt.UUID {
	xs := make([]strfmt.UUID, len(b.Index))
	for i, idx := range b.Index {
		xs[i] = b.Data[idx].ID()
	}
	return xs
}

func (b *shardPart) Extract() ([]objects.Replica, []strfmt.UUID) {
	xs := make([]objects.Replica, len(b.Index))
	ys := make([]strfmt.UUID, len(b.Index))

	for i, idx := range b.Index {
		p := b.Data[idx]
		xs[i] = objects.Replica{ID: p.ID(), Deleted: false, Object: p}
		ys[i] = p.ID()
	}
	return xs, ys
}