package resource

import (
	"context"
	"encoding/json"
	"fmt"
	golog "log"
	"os"
	"strings"

	"github.com/blevesearch/bleve/v2"
	"github.com/blevesearch/bleve/v2/analysis/lang/en"
	"github.com/blevesearch/bleve/v2/mapping"
	"github.com/google/uuid"
	"github.com/grafana/grafana/pkg/infra/log"
	"golang.org/x/exp/slices"
)

type Shard struct {
	index bleve.Index
	path  string
	batch *bleve.Batch
}

type Index struct {
	shards map[string]Shard
	opts   Opts
	s      *server
	log    log.Logger
}

func NewIndex(s *server, opts Opts) *Index {
	idx := &Index{
		s:      s,
		opts:   opts,
		shards: make(map[string]Shard),
		log:    log.New("unifiedstorage.search.index"),
	}
	return idx
}

func (i *Index) IndexBatch(list *ListResponse, kind string) error {
	for _, obj := range list.Items {
		res, err := getResource(obj.Value)
		if err != nil {
			return err
		}

		shard, err := i.getShard(tenant(res))
		if err != nil {
			return err
		}
		i.log.Debug("initial indexing resources batch", "count", len(list.Items), "kind", kind, "tenant", tenant(res))

		var jsonDoc interface{}
		err = json.Unmarshal(obj.Value, &jsonDoc)
		if err != nil {
			return err
		}
		err = shard.batch.Index(res.Metadata.Uid, jsonDoc)
		if err != nil {
			return err
		}
	}

	for _, shard := range i.shards {
		err := shard.index.Batch(shard.batch)
		if err != nil {
			return err
		}
		shard.batch.Reset()
	}

	return nil
}

func (i *Index) Init(ctx context.Context) error {
	resourceTypes := fetchResourceTypes()
	for _, rt := range resourceTypes {
		i.log.Info("indexing resource", "kind", rt.Key.Resource)
		r := &ListRequest{Options: rt, Limit: 100}

		// Paginate through the list of resources and index each page
		for {
			list, err := i.s.List(ctx, r)
			if err != nil {
				return err
			}

			// Index current page
			err = i.IndexBatch(list, rt.Key.Resource)
			if err != nil {
				return err
			}

			if list.NextPageToken == "" {
				break
			}

			r.NextPageToken = list.NextPageToken
		}
	}

	return nil
}

func (i *Index) Index(ctx context.Context, data *Data) error {
	res, err := getResource(data.Value.Value)
	if err != nil {
		return err
	}
	tenant := tenant(res)
	i.log.Debug("indexing resource for tenant", "res", res, "tenant", tenant)
	shard, err := i.getShard(tenant)
	if err != nil {
		return err
	}
	var jsonDoc interface{}
	err = json.Unmarshal(data.Value.Value, &jsonDoc)
	if err != nil {
		return err
	}
	err = shard.index.Index(res.Metadata.Uid, jsonDoc)
	if err != nil {
		return err
	}
	return nil
}

func (i *Index) Delete(ctx context.Context, uid string, key *ResourceKey) error {
	shard, err := i.getShard(key.Namespace)
	if err != nil {
		return err
	}
	err = shard.index.Delete(uid)
	if err != nil {
		return err
	}
	return nil
}

func (i *Index) Search(ctx context.Context, tenant string, query string, limit int, offset int) ([]SearchSummary, error) {
	if tenant == "" {
		tenant = "default"
	}
	shard, err := i.getShard(tenant)
	if err != nil {
		return nil, err
	}
	docCount, err := shard.index.DocCount()
	if err != nil {
		return nil, err
	}
	i.log.Info("got index for tenant", "tenant", tenant, "docCount", docCount)

	// use 10 as a default limit for now
	if limit <= 0 {
		limit = 10
	}

	req := bleve.NewSearchRequest(bleve.NewQueryStringQuery(query))
	req.From = offset
	req.Size = limit

	req.Fields = []string{"*"} // return all indexed fields in search results

	i.log.Info("searching index", "query", query, "tenant", tenant)
	res, err := shard.index.Search(req)
	if err != nil {
		return nil, err
	}
	hits := res.Hits

	i.log.Info("got search results", "hits", hits)

	results := make([]SearchSummary, len(hits))
	for resKey, hit := range hits {
		searchSummary := SearchSummary{}

		// add common fields to search results
		searchSummary.Kind = hit.Fields["kind"].(string)
		searchSummary.Metadata.CreationTimestamp = hit.Fields["metadata.creationTimestamp"].(string)
		searchSummary.Metadata.Uid = hit.Fields["metadata.uid"].(string)

		// add allowed indexed spec fields to search results
		specResult := map[string]interface{}{}
		for k, v := range hit.Fields {
			if strings.HasPrefix(k, "spec.") {
				mappedFields := specFieldMappings(searchSummary.Kind)
				// should only include spec fields we care about in search results
				if slices.Contains(mappedFields, k) {
					specKey := strings.TrimPrefix(k, "spec.")
					specResult[specKey] = v
				}
			}
			searchSummary.Spec = specResult
		}

		results[resKey] = searchSummary
	}

	return results, nil
}

func tenant(res *Resource) string {
	return res.Metadata.Namespace
}

type SearchSummary struct {
	Kind     string `json:"kind"`
	Metadata `json:"metadata"`
	Spec     map[string]interface{} `json:"spec"`
}

type Metadata struct {
	Name              string
	Namespace         string
	Uid               string `json:"uid"`
	CreationTimestamp string `json:"creationTimestamp"`
	Labels            map[string]string
	Annotations       map[string]string
}

type Resource struct {
	Kind       string
	ApiVersion string
	Metadata   Metadata
}

type Opts struct {
	Workers    int // This controls how many goroutines are used to index objects
	BatchSize  int // This is the batch size for how many objects to add to the index at once
	Concurrent bool
}

func createFileIndex() (bleve.Index, string, error) {
	indexPath := fmt.Sprintf("%s%s.bleve", os.TempDir(), uuid.New().String())
	index, err := bleve.New(indexPath, createIndexMappings())
	if err != nil {
		golog.Fatalf("Failed to create index: %v", err)
	}
	return index, indexPath, err
}

func createIndexMappings() *mapping.IndexMappingImpl {
	//Create mapping for the creationTimestamp field in the metadata
	creationTimestampFieldMapping := bleve.NewDateTimeFieldMapping()
	uidMapping := bleve.NewTextFieldMapping()
	metaMapping := bleve.NewDocumentMapping()
	metaMapping.AddFieldMappingsAt("creationTimestamp", creationTimestampFieldMapping)
	metaMapping.AddFieldMappingsAt("uid", uidMapping)
	metaMapping.Dynamic = false
	metaMapping.Enabled = true

	// Spec is different for all resources, so we create a dynamic mapping for it to index all fields (for now)
	specMapping := bleve.NewDocumentMapping()
	specMapping.Dynamic = true
	specMapping.Enabled = true

	//Create a sub-document mapping for the metadata field
	objectMapping := bleve.NewDocumentMapping()
	objectMapping.AddSubDocumentMapping("metadata", metaMapping)
	objectMapping.AddSubDocumentMapping("spec", specMapping)
	objectMapping.Dynamic = true
	objectMapping.Enabled = true

	// a generic reusable mapping for english text
	englishTextFieldMapping := bleve.NewTextFieldMapping()
	englishTextFieldMapping.Analyzer = en.AnalyzerName

	// Map top level fields - just kind for now
	objectMapping.AddFieldMappingsAt("kind", englishTextFieldMapping)
	objectMapping.Dynamic = false

	// Create the index mapping
	indexMapping := bleve.NewIndexMapping()
	indexMapping.DefaultMapping = objectMapping

	return indexMapping
}

func getResource(data []byte) (*Resource, error) {
	res := &Resource{}
	err := json.Unmarshal(data, res)
	if err != nil {
		return nil, err
	}
	return res, nil
}

func (i *Index) getShard(tenant string) (Shard, error) {
	shard, ok := i.shards[tenant]
	if ok {
		return shard, nil
	}
	index, path, err := createFileIndex()
	if err != nil {
		return Shard{}, err
	}

	shard = Shard{
		index: index,
		path:  path,
		batch: index.NewBatch(),
	}
	// TODO: do we need to lock this?
	i.shards[tenant] = shard
	return shard, nil
}

// TODO - fetch from api
func fetchResourceTypes() []*ListOptions {
	items := []*ListOptions{}
	items = append(items, &ListOptions{
		Key: &ResourceKey{
			Group:    "playlist.grafana.app",
			Resource: "playlists",
		},
	})
	return items
}

func specFieldMappings(kind string) []string {
	mappedFields := map[string][]string{
		"Playlist": {
			"spec.title",
			"spec.interval",
		},
	}

	return mappedFields[kind]
}