// Copyright 2024 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package bleve

import (
	"context"

	"code.gitea.io/gitea/modules/indexer/conversations/internal"
	indexer_internal "code.gitea.io/gitea/modules/indexer/internal"
	inner_bleve "code.gitea.io/gitea/modules/indexer/internal/bleve"

	"github.com/blevesearch/bleve/v2"
	"github.com/blevesearch/bleve/v2/analysis/analyzer/custom"
	"github.com/blevesearch/bleve/v2/analysis/token/camelcase"
	"github.com/blevesearch/bleve/v2/analysis/token/lowercase"
	"github.com/blevesearch/bleve/v2/analysis/token/unicodenorm"
	"github.com/blevesearch/bleve/v2/analysis/tokenizer/unicode"
	"github.com/blevesearch/bleve/v2/mapping"
	"github.com/blevesearch/bleve/v2/search/query"
)

const (
	conversationIndexerAnalyzer      = "conversationIndexer"
	conversationIndexerDocType       = "conversationIndexerDocType"
	conversationIndexerLatestVersion = 4
)

const unicodeNormalizeName = "unicodeNormalize"

func addUnicodeNormalizeTokenFilter(m *mapping.IndexMappingImpl) error {
	return m.AddCustomTokenFilter(unicodeNormalizeName, map[string]any{
		"type": unicodenorm.Name,
		"form": unicodenorm.NFC,
	})
}

const maxBatchSize = 16

// IndexerData an update to the conversation indexer
type IndexerData internal.IndexerData

// Type returns the document type, for bleve's mapping.Classifier interface.
func (i *IndexerData) Type() string {
	return conversationIndexerDocType
}

// generateConversationIndexMapping generates the bleve index mapping for conversations
func generateConversationIndexMapping() (mapping.IndexMapping, error) {
	mapping := bleve.NewIndexMapping()
	docMapping := bleve.NewDocumentMapping()

	numericFieldMapping := bleve.NewNumericFieldMapping()
	numericFieldMapping.Store = false
	numericFieldMapping.IncludeInAll = false
	docMapping.AddFieldMappingsAt("repo_id", numericFieldMapping)

	textFieldMapping := bleve.NewTextFieldMapping()
	textFieldMapping.Store = false
	textFieldMapping.IncludeInAll = false

	boolFieldMapping := bleve.NewBooleanFieldMapping()
	boolFieldMapping.Store = false
	boolFieldMapping.IncludeInAll = false

	numberFieldMapping := bleve.NewNumericFieldMapping()
	numberFieldMapping.Store = false
	numberFieldMapping.IncludeInAll = false

	docMapping.AddFieldMappingsAt("is_public", boolFieldMapping)

	docMapping.AddFieldMappingsAt("title", textFieldMapping)
	docMapping.AddFieldMappingsAt("content", textFieldMapping)
	docMapping.AddFieldMappingsAt("comments", textFieldMapping)

	docMapping.AddFieldMappingsAt("is_pull", boolFieldMapping)
	docMapping.AddFieldMappingsAt("is_closed", boolFieldMapping)
	docMapping.AddFieldMappingsAt("label_ids", numberFieldMapping)
	docMapping.AddFieldMappingsAt("no_label", boolFieldMapping)
	docMapping.AddFieldMappingsAt("milestone_id", numberFieldMapping)
	docMapping.AddFieldMappingsAt("project_id", numberFieldMapping)
	docMapping.AddFieldMappingsAt("project_board_id", numberFieldMapping)
	docMapping.AddFieldMappingsAt("poster_id", numberFieldMapping)
	docMapping.AddFieldMappingsAt("assignee_id", numberFieldMapping)
	docMapping.AddFieldMappingsAt("mention_ids", numberFieldMapping)
	docMapping.AddFieldMappingsAt("reviewed_ids", numberFieldMapping)
	docMapping.AddFieldMappingsAt("review_requested_ids", numberFieldMapping)
	docMapping.AddFieldMappingsAt("subscriber_ids", numberFieldMapping)
	docMapping.AddFieldMappingsAt("updated_unix", numberFieldMapping)

	docMapping.AddFieldMappingsAt("created_unix", numberFieldMapping)
	docMapping.AddFieldMappingsAt("deadline_unix", numberFieldMapping)
	docMapping.AddFieldMappingsAt("comment_count", numberFieldMapping)

	if err := addUnicodeNormalizeTokenFilter(mapping); err != nil {
		return nil, err
	} else if err = mapping.AddCustomAnalyzer(conversationIndexerAnalyzer, map[string]any{
		"type":          custom.Name,
		"char_filters":  []string{},
		"tokenizer":     unicode.Name,
		"token_filters": []string{unicodeNormalizeName, camelcase.Name, lowercase.Name},
	}); err != nil {
		return nil, err
	}

	mapping.DefaultAnalyzer = conversationIndexerAnalyzer
	mapping.AddDocumentMapping(conversationIndexerDocType, docMapping)
	mapping.AddDocumentMapping("_all", bleve.NewDocumentDisabledMapping())
	mapping.DefaultMapping = bleve.NewDocumentDisabledMapping() // disable default mapping, avoid indexing unexpected structs

	return mapping, nil
}

var _ internal.Indexer = &Indexer{}

// Indexer implements Indexer interface
type Indexer struct {
	inner                    *inner_bleve.Indexer
	indexer_internal.Indexer // do not composite inner_bleve.Indexer directly to avoid exposing too much
}

// NewIndexer creates a new bleve local indexer
func NewIndexer(indexDir string) *Indexer {
	inner := inner_bleve.NewIndexer(indexDir, conversationIndexerLatestVersion, generateConversationIndexMapping)
	return &Indexer{
		Indexer: inner,
		inner:   inner,
	}
}

// Index will save the index data
func (b *Indexer) Index(_ context.Context, conversations ...*internal.IndexerData) error {
	batch := inner_bleve.NewFlushingBatch(b.inner.Indexer, maxBatchSize)
	for _, conversation := range conversations {
		if err := batch.Index(indexer_internal.Base36(conversation.ID), (*IndexerData)(conversation)); err != nil {
			return err
		}
	}
	return batch.Flush()
}

// Delete deletes indexes by ids
func (b *Indexer) Delete(_ context.Context, ids ...int64) error {
	batch := inner_bleve.NewFlushingBatch(b.inner.Indexer, maxBatchSize)
	for _, id := range ids {
		if err := batch.Delete(indexer_internal.Base36(id)); err != nil {
			return err
		}
	}
	return batch.Flush()
}

// Search searches for conversations by given conditions.
// Returns the matching conversation IDs
func (b *Indexer) Search(ctx context.Context, options *internal.SearchOptions) (*internal.SearchResult, error) {
	var queries []query.Query

	if options.Keyword != "" {
		fuzziness := 0
		if options.IsFuzzyKeyword {
			fuzziness = inner_bleve.GuessFuzzinessByKeyword(options.Keyword)
		}

		queries = append(queries, bleve.NewDisjunctionQuery([]query.Query{
			inner_bleve.MatchPhraseQuery(options.Keyword, "title", conversationIndexerAnalyzer, fuzziness),
			inner_bleve.MatchPhraseQuery(options.Keyword, "content", conversationIndexerAnalyzer, fuzziness),
			inner_bleve.MatchPhraseQuery(options.Keyword, "comments", conversationIndexerAnalyzer, fuzziness),
		}...))
	}

	if len(options.RepoIDs) > 0 || options.AllPublic {
		var repoQueries []query.Query
		for _, repoID := range options.RepoIDs {
			repoQueries = append(repoQueries, inner_bleve.NumericEqualityQuery(repoID, "repo_id"))
		}
		if options.AllPublic {
			repoQueries = append(repoQueries, inner_bleve.BoolFieldQuery(true, "is_public"))
		}
		queries = append(queries, bleve.NewDisjunctionQuery(repoQueries...))
	}

	if options.UpdatedAfterUnix.Has() || options.UpdatedBeforeUnix.Has() {
		queries = append(queries, inner_bleve.NumericRangeInclusiveQuery(
			options.UpdatedAfterUnix,
			options.UpdatedBeforeUnix,
			"updated_unix"))
	}

	var indexerQuery query.Query = bleve.NewConjunctionQuery(queries...)
	if len(queries) == 0 {
		indexerQuery = bleve.NewMatchAllQuery()
	}

	skip, limit := indexer_internal.ParsePaginator(options.Paginator)
	search := bleve.NewSearchRequestOptions(indexerQuery, limit, skip, false)

	if options.SortBy == "" {
		options.SortBy = internal.SortByCreatedAsc
	}

	search.SortBy([]string{string(options.SortBy), "-_id"})

	result, err := b.inner.Indexer.SearchInContext(ctx, search)
	if err != nil {
		return nil, err
	}

	ret := &internal.SearchResult{
		Total: int64(result.Total),
		Hits:  make([]internal.Match, 0, len(result.Hits)),
	}
	for _, hit := range result.Hits {
		id, err := indexer_internal.ParseBase36(hit.ID)
		if err != nil {
			return nil, err
		}
		ret.Hits = append(ret.Hits, internal.Match{
			ID: id,
		})
	}
	return ret, nil
}