//  Copyright (c) 2014 Couchbase, Inc.
//  Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
//  except in compliance with the License. You may obtain a copy of the License at
//    http://www.apache.org/licenses/LICENSE-2.0
//  Unless required by applicable law or agreed to in writing, software distributed under the
//  License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
//  either express or implied. See the License for the specific language governing permissions
//  and limitations under the License.

package bleve

import (
	"encoding/json"
	"fmt"
	"os"
	"sync"
	"sync/atomic"
	"time"

	"github.com/blevesearch/bleve/document"
	"github.com/blevesearch/bleve/index"
	"github.com/blevesearch/bleve/index/store"
	"github.com/blevesearch/bleve/index/store/gtreap"
	"github.com/blevesearch/bleve/index/upside_down"
	"github.com/blevesearch/bleve/registry"
	"github.com/blevesearch/bleve/search"
	"github.com/blevesearch/bleve/search/collectors"
	"github.com/blevesearch/bleve/search/facets"
)

type indexImpl struct {
	path  string
	name  string
	meta  *indexMeta
	s     store.KVStore
	i     index.Index
	m     *IndexMapping
	mutex sync.RWMutex
	open  bool
	stats *IndexStat
}

const storePath = "store"

var mappingInternalKey = []byte("_mapping")

func indexStorePath(path string) string {
	return path + string(os.PathSeparator) + storePath
}

func newMemIndex(indexType string, mapping *IndexMapping) (*indexImpl, error) {
	rv := indexImpl{
		path:  "",
		name:  "mem",
		m:     mapping,
		meta:  newIndexMeta(indexType, gtreap.Name, nil),
		stats: &IndexStat{},
	}

	// open the index
	indexTypeConstructor := registry.IndexTypeConstructorByName(rv.meta.IndexType)
	if indexTypeConstructor == nil {
		return nil, ErrorUnknownIndexType
	}

	var err error
	rv.i, err = indexTypeConstructor(rv.meta.Storage, nil, Config.analysisQueue)
	if err != nil {
		return nil, err
	}
	err = rv.i.Open()
	if err != nil {
		return nil, err
	}
	rv.stats.indexStat = rv.i.Stats()

	// now persist the mapping
	mappingBytes, err := json.Marshal(mapping)
	if err != nil {
		return nil, err
	}
	err = rv.i.SetInternal(mappingInternalKey, mappingBytes)
	if err != nil {
		return nil, err
	}

	// mark the index as open
	rv.mutex.Lock()
	defer rv.mutex.Unlock()
	rv.open = true
	indexStats.Register(&rv)
	return &rv, nil
}

func newIndexUsing(path string, mapping *IndexMapping, indexType string, kvstore string, kvconfig map[string]interface{}) (*indexImpl, error) {
	// first validate the mapping
	err := mapping.validate()
	if err != nil {
		return nil, err
	}

	if path == "" {
		return newMemIndex(indexType, mapping)
	}

	if kvconfig == nil {
		kvconfig = map[string]interface{}{}
	}

	rv := indexImpl{
		path:  path,
		name:  path,
		m:     mapping,
		meta:  newIndexMeta(indexType, kvstore, kvconfig),
		stats: &IndexStat{},
	}
	// at this point there is hope that we can be successful, so save index meta
	err = rv.meta.Save(path)
	if err != nil {
		return nil, err
	}
	kvconfig["create_if_missing"] = true
	kvconfig["error_if_exists"] = true
	kvconfig["path"] = indexStorePath(path)

	// open the index
	indexTypeConstructor := registry.IndexTypeConstructorByName(rv.meta.IndexType)
	if indexTypeConstructor == nil {
		return nil, ErrorUnknownIndexType
	}

	rv.i, err = indexTypeConstructor(rv.meta.Storage, kvconfig, Config.analysisQueue)
	if err != nil {
		return nil, err
	}
	err = rv.i.Open()
	if err != nil {
		if err == index.ErrorUnknownStorageType {
			return nil, ErrorUnknownStorageType
		}
		return nil, err
	}
	rv.stats.indexStat = rv.i.Stats()

	// now persist the mapping
	mappingBytes, err := json.Marshal(mapping)
	if err != nil {
		return nil, err
	}
	err = rv.i.SetInternal(mappingInternalKey, mappingBytes)
	if err != nil {
		return nil, err
	}

	// mark the index as open
	rv.mutex.Lock()
	defer rv.mutex.Unlock()
	rv.open = true
	indexStats.Register(&rv)
	return &rv, nil
}

func openIndexUsing(path string, runtimeConfig map[string]interface{}) (rv *indexImpl, err error) {
	rv = &indexImpl{
		path:  path,
		name:  path,
		stats: &IndexStat{},
	}

	rv.meta, err = openIndexMeta(path)
	if err != nil {
		return nil, err
	}

	// backwards compatibility if index type is missing
	if rv.meta.IndexType == "" {
		rv.meta.IndexType = upside_down.Name
	}

	storeConfig := rv.meta.Config
	if storeConfig == nil {
		storeConfig = map[string]interface{}{}
	}

	storeConfig["path"] = indexStorePath(path)
	storeConfig["create_if_missing"] = false
	storeConfig["error_if_exists"] = false
	for rck, rcv := range runtimeConfig {
		storeConfig[rck] = rcv
	}

	// open the index
	indexTypeConstructor := registry.IndexTypeConstructorByName(rv.meta.IndexType)
	if indexTypeConstructor == nil {
		return nil, ErrorUnknownIndexType
	}

	rv.i, err = indexTypeConstructor(rv.meta.Storage, storeConfig, Config.analysisQueue)
	if err != nil {
		return nil, err
	}
	err = rv.i.Open()
	if err != nil {
		if err == index.ErrorUnknownStorageType {
			return nil, ErrorUnknownStorageType
		}
		return nil, err
	}
	rv.stats.indexStat = rv.i.Stats()

	// now load the mapping
	indexReader, err := rv.i.Reader()
	if err != nil {
		return nil, err
	}
	defer func() {
		if cerr := indexReader.Close(); cerr != nil && err == nil {
			err = cerr
		}
	}()

	mappingBytes, err := indexReader.GetInternal(mappingInternalKey)
	if err != nil {
		return nil, err
	}

	var im IndexMapping
	err = json.Unmarshal(mappingBytes, &im)
	if err != nil {
		return nil, err
	}

	// mark the index as open
	rv.mutex.Lock()
	defer rv.mutex.Unlock()
	rv.open = true

	// validate the mapping
	err = im.validate()
	if err != nil {
		// note even if the mapping is invalid
		// we still return an open usable index
		return rv, err
	}

	rv.m = &im
	indexStats.Register(rv)
	return rv, err
}

// Advanced returns implementation internals
// necessary ONLY for advanced usage.
func (i *indexImpl) Advanced() (index.Index, store.KVStore, error) {
	return i.i, i.s, nil
}

// Mapping returns the IndexMapping in use by this
// Index.
func (i *indexImpl) Mapping() *IndexMapping {
	return i.m
}

// Index the object with the specified identifier.
// The IndexMapping for this index will determine
// how the object is indexed.
func (i *indexImpl) Index(id string, data interface{}) (err error) {
	if id == "" {
		return ErrorEmptyID
	}

	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return ErrorIndexClosed
	}

	doc := document.NewDocument(id)
	err = i.m.mapDocument(doc, data)
	if err != nil {
		return
	}
	err = i.i.Update(doc)
	return
}

// Delete entries for the specified identifier from
// the index.
func (i *indexImpl) Delete(id string) (err error) {
	if id == "" {
		return ErrorEmptyID
	}

	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return ErrorIndexClosed
	}

	err = i.i.Delete(id)
	return
}

// Batch executes multiple Index and Delete
// operations at the same time.  There are often
// significant performance benefits when performing
// operations in a batch.
func (i *indexImpl) Batch(b *Batch) error {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return ErrorIndexClosed
	}

	return i.i.Batch(b.internal)
}

// Document is used to find the values of all the
// stored fields for a document in the index.  These
// stored fields are put back into a Document object
// and returned.
func (i *indexImpl) Document(id string) (doc *document.Document, err error) {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return nil, ErrorIndexClosed
	}
	indexReader, err := i.i.Reader()
	if err != nil {
		return nil, err
	}
	defer func() {
		if cerr := indexReader.Close(); err == nil && cerr != nil {
			err = cerr
		}
	}()

	doc, err = indexReader.Document(id)
	if err != nil {
		return nil, err
	}
	return doc, nil
}

// DocCount returns the number of documents in the
// index.
func (i *indexImpl) DocCount() (uint64, error) {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return 0, ErrorIndexClosed
	}

	return i.i.DocCount()
}

// this error message is a temporary measure to avoid crashing when an
// inconsistent state of the index is encountered
var errMsg17298 = fmt.Errorf("Internal Error Detected - A known inconsistency has been detected, and this search cannot be completed.  The index is not corrupt and the search may succeed if you try again.  Please see the following bug for the latest information: https://issues.couchbase.com/browse/MB-17298")

// Search executes a search request operation.
// Returns a SearchResult object or an error.
func (i *indexImpl) Search(req *SearchRequest) (sr *SearchResult, err error) {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	searchStart := time.Now()

	if !i.open {
		return nil, ErrorIndexClosed
	}

	collector := collectors.NewTopScorerSkipCollector(req.Size, req.From)

	// open a reader for this search
	indexReader, err := i.i.Reader()
	if err != nil {
		return nil, fmt.Errorf("error opening index reader %v", err)
	}
	defer func() {
		if cerr := indexReader.Close(); err == nil && cerr != nil {
			err = cerr
		}
	}()

	searcher, err := req.Query.Searcher(indexReader, i.m, req.Explain)
	if err != nil {
		return nil, err
	}
	defer func() {
		if serr := searcher.Close(); err == nil && serr != nil {
			err = serr
		}
	}()

	if req.Facets != nil {
		facetsBuilder := search.NewFacetsBuilder(indexReader)
		for facetName, facetRequest := range req.Facets {
			if facetRequest.NumericRanges != nil {
				// build numeric range facet
				facetBuilder := facets.NewNumericFacetBuilder(facetRequest.Field, facetRequest.Size)
				for _, nr := range facetRequest.NumericRanges {
					facetBuilder.AddRange(nr.Name, nr.Min, nr.Max)
				}
				facetsBuilder.Add(facetName, facetBuilder)
			} else if facetRequest.DateTimeRanges != nil {
				// build date range facet
				facetBuilder := facets.NewDateTimeFacetBuilder(facetRequest.Field, facetRequest.Size)
				dateTimeParser := i.m.dateTimeParserNamed(i.m.DefaultDateTimeParser)
				for _, dr := range facetRequest.DateTimeRanges {
					dr.ParseDates(dateTimeParser)
					facetBuilder.AddRange(dr.Name, dr.Start, dr.End)
				}
				facetsBuilder.Add(facetName, facetBuilder)
			} else {
				// build terms facet
				facetBuilder := facets.NewTermsFacetBuilder(facetRequest.Field, facetRequest.Size)
				facetsBuilder.Add(facetName, facetBuilder)
			}
		}
		collector.SetFacetsBuilder(facetsBuilder)
	}

	err = collector.Collect(searcher)
	if err != nil {
		return nil, err
	}

	hits := collector.Results()

	if req.Highlight != nil {
		// get the right highlighter
		highlighter, err := Config.Cache.HighlighterNamed(Config.DefaultHighlighter)
		if err != nil {
			return nil, err
		}
		if req.Highlight.Style != nil {
			highlighter, err = Config.Cache.HighlighterNamed(*req.Highlight.Style)
			if err != nil {
				return nil, err
			}
		}
		if highlighter == nil {
			return nil, fmt.Errorf("no highlighter named `%s` registered", *req.Highlight.Style)
		}

		for _, hit := range hits {
			doc, err := indexReader.Document(hit.ID)
			if err == nil && doc != nil {
				highlightFields := req.Highlight.Fields
				if highlightFields == nil {
					// add all fields with matches
					highlightFields = make([]string, 0, len(hit.Locations))
					for k := range hit.Locations {
						highlightFields = append(highlightFields, k)
					}
				}

				for _, hf := range highlightFields {
					highlighter.BestFragmentsInField(hit, doc, hf, 1)
				}
			} else if err == nil {
				// unexpected case, a doc ID that was found as a search hit
				// was unable to be found during document lookup
				return nil, errMsg17298
			}
		}
	}

	if len(req.Fields) > 0 {
		for _, hit := range hits {
			// FIXME avoid loading doc second time
			// if we already loaded it for highlighting
			doc, err := indexReader.Document(hit.ID)
			if err == nil && doc != nil {
				for _, f := range req.Fields {
					for _, docF := range doc.Fields {
						if f == "*" || docF.Name() == f {
							var value interface{}
							switch docF := docF.(type) {
							case *document.TextField:
								value = string(docF.Value())
							case *document.NumericField:
								num, err := docF.Number()
								if err == nil {
									value = num
								}
							case *document.DateTimeField:
								datetime, err := docF.DateTime()
								if err == nil {
									value = datetime.Format(time.RFC3339)
								}
							case *document.BooleanField:
								boolean, err := docF.Boolean()
								if err == nil {
									value = boolean
								}
							}
							if value != nil {
								hit.AddFieldValue(docF.Name(), value)
							}
						}
					}
				}
			} else if doc == nil {
				// unexpected case, a doc ID that was found as a search hit
				// was unable to be found during document lookup
				return nil, errMsg17298
			}
		}
	}

	for _, hit := range hits {
		if i.name != "" {
			hit.Index = i.name
		}
	}

	atomic.AddUint64(&i.stats.searches, 1)
	searchDuration := time.Since(searchStart)
	atomic.AddUint64(&i.stats.searchTime, uint64(searchDuration))

	if searchDuration > Config.SlowSearchLogThreshold {
		logger.Printf("slow search took %s - %v", searchDuration, req)
	}

	return &SearchResult{
		Request:  req,
		Hits:     hits,
		Total:    collector.Total(),
		MaxScore: collector.MaxScore(),
		Took:     searchDuration,
		Facets:   collector.FacetResults(),
	}, nil
}

// Fields returns the name of all the fields this
// Index has operated on.
func (i *indexImpl) Fields() (fields []string, err error) {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return nil, ErrorIndexClosed
	}

	indexReader, err := i.i.Reader()
	if err != nil {
		return nil, err
	}
	defer func() {
		if cerr := indexReader.Close(); err == nil && cerr != nil {
			err = cerr
		}
	}()

	fields, err = indexReader.Fields()
	if err != nil {
		return nil, err
	}
	return fields, nil
}

func (i *indexImpl) FieldDict(field string) (index.FieldDict, error) {
	i.mutex.RLock()

	if !i.open {
		i.mutex.RUnlock()
		return nil, ErrorIndexClosed
	}

	indexReader, err := i.i.Reader()
	if err != nil {
		i.mutex.RUnlock()
		return nil, err
	}

	fieldDict, err := indexReader.FieldDict(field)
	if err != nil {
		i.mutex.RUnlock()
		return nil, err
	}

	return &indexImplFieldDict{
		index:       i,
		indexReader: indexReader,
		fieldDict:   fieldDict,
	}, nil
}

func (i *indexImpl) FieldDictRange(field string, startTerm []byte, endTerm []byte) (index.FieldDict, error) {
	i.mutex.RLock()

	if !i.open {
		i.mutex.RUnlock()
		return nil, ErrorIndexClosed
	}

	indexReader, err := i.i.Reader()
	if err != nil {
		i.mutex.RUnlock()
		return nil, err
	}

	fieldDict, err := indexReader.FieldDictRange(field, startTerm, endTerm)
	if err != nil {
		i.mutex.RUnlock()
		return nil, err
	}

	return &indexImplFieldDict{
		index:       i,
		indexReader: indexReader,
		fieldDict:   fieldDict,
	}, nil
}

func (i *indexImpl) FieldDictPrefix(field string, termPrefix []byte) (index.FieldDict, error) {
	i.mutex.RLock()

	if !i.open {
		i.mutex.RUnlock()
		return nil, ErrorIndexClosed
	}

	indexReader, err := i.i.Reader()
	if err != nil {
		i.mutex.RUnlock()
		return nil, err
	}

	fieldDict, err := indexReader.FieldDictPrefix(field, termPrefix)
	if err != nil {
		i.mutex.RUnlock()
		return nil, err
	}

	return &indexImplFieldDict{
		index:       i,
		indexReader: indexReader,
		fieldDict:   fieldDict,
	}, nil
}

// DumpAll writes all index rows to a channel.
// INTERNAL: do not rely on this function, it is
// only intended to be used by the debug utilities
func (i *indexImpl) DumpAll() chan interface{} {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return nil
	}

	return i.i.DumpAll()
}

// DumpFields writes all field rows in the index
// to a channel.
// INTERNAL: do not rely on this function, it is
// only intended to be used by the debug utilities
func (i *indexImpl) DumpFields() chan interface{} {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return nil
	}
	return i.i.DumpFields()
}

// DumpDoc writes all rows in the index associated
// with the specified identifier to a channel.
// INTERNAL: do not rely on this function, it is
// only intended to be used by the debug utilities
func (i *indexImpl) DumpDoc(id string) chan interface{} {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return nil
	}
	return i.i.DumpDoc(id)
}

func (i *indexImpl) Close() error {
	i.mutex.Lock()
	defer i.mutex.Unlock()

	i.open = false
	return i.i.Close()
}

func (i *indexImpl) Stats() *IndexStat {
	return i.stats
}

func (i *indexImpl) GetInternal(key []byte) (val []byte, err error) {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return nil, ErrorIndexClosed
	}

	reader, err := i.i.Reader()
	if err != nil {
		return nil, err
	}
	defer func() {
		if cerr := reader.Close(); err == nil && cerr != nil {
			err = cerr
		}
	}()

	val, err = reader.GetInternal(key)
	if err != nil {
		return nil, err
	}
	return val, nil
}

func (i *indexImpl) SetInternal(key, val []byte) error {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return ErrorIndexClosed
	}

	return i.i.SetInternal(key, val)
}

func (i *indexImpl) DeleteInternal(key []byte) error {
	i.mutex.RLock()
	defer i.mutex.RUnlock()

	if !i.open {
		return ErrorIndexClosed
	}

	return i.i.DeleteInternal(key)
}

// NewBatch creates a new empty batch.
func (i *indexImpl) NewBatch() *Batch {
	return &Batch{
		index:    i,
		internal: index.NewBatch(),
	}
}

func (i *indexImpl) Name() string {
	return i.name
}

func (i *indexImpl) SetName(name string) {
	indexStats.UnRegister(i)
	i.name = name
	indexStats.Register(i)
}

type indexImplFieldDict struct {
	index       *indexImpl
	indexReader index.IndexReader
	fieldDict   index.FieldDict
}

func (f *indexImplFieldDict) Next() (*index.DictEntry, error) {
	return f.fieldDict.Next()
}

func (f *indexImplFieldDict) Close() error {
	defer f.index.mutex.RUnlock()
	err := f.fieldDict.Close()
	if err != nil {
		return err
	}
	return f.indexReader.Close()
}