// Package search provides full-text search functionality using Bleve.
//
// This package implements a local full-text search index for files and collections
// using the Bleve search library (https://blevesearch.com/). The search index is
// stored per-user in their local application data directory.
//
// Key features:
//   - Case-insensitive substring matching (e.g., "mesh" matches "meshtastic")
//   - Support for Bleve query syntax (+, -, "", *, ?)
//   - Deduplication of search results by document ID
//   - Batch indexing for efficient rebuilds
//   - User-isolated indexes (each user has their own search index)
//
// Location: monorepo/native/desktop/maplefile/internal/service/search/search.go
package search

import (
	"context"
	"fmt"
	"os"
	"strings"
	"time"

	"github.com/blevesearch/bleve/v2"
	"github.com/blevesearch/bleve/v2/mapping"
	"go.uber.org/zap"

	"codeberg.org/mapleopentech/monorepo/native/desktop/maplefile/internal/config"
)

// SearchService provides full-text search capabilities
type SearchService interface {
	// Initialize opens or creates the search index for the specified user email
	Initialize(ctx context.Context, userEmail string) error

	// Close closes the search index
	Close() error

	// IndexFile adds or updates a file in the search index
	IndexFile(file *FileDocument) error

	// IndexCollection adds or updates a collection in the search index
	IndexCollection(collection *CollectionDocument) error

	// DeleteFile removes a file from the search index
	DeleteFile(fileID string) error

	// DeleteCollection removes a collection from the search index
	DeleteCollection(collectionID string) error

	// Search performs a full-text search
	Search(query string, limit int) (*SearchResult, error)

	// RebuildIndex rebuilds the entire search index from scratch
	RebuildIndex(userEmail string, files []*FileDocument, collections []*CollectionDocument) error

	// GetIndexSize returns the size of the search index in bytes
	GetIndexSize() (int64, error)

	// GetDocumentCount returns the number of documents in the index
	GetDocumentCount() (uint64, error)
}

// FileDocument represents a file document in the search index
type FileDocument struct {
	ID             string    `json:"id"`
	Filename       string    `json:"filename"`
	Description    string    `json:"description"`
	CollectionID   string    `json:"collection_id"`
	CollectionName string    `json:"collection_name"` // Denormalized for search
	Tags           []string  `json:"tags"`
	Size           int64     `json:"size"`
	CreatedAt      time.Time `json:"created_at"`
	Type           string    `json:"type"` // "file"
}

// CollectionDocument represents a collection document in the search index
type CollectionDocument struct {
	ID          string    `json:"id"`
	Name        string    `json:"name"`
	Description string    `json:"description"`
	Tags        []string  `json:"tags"`
	FileCount   int       `json:"file_count"`
	CreatedAt   time.Time `json:"created_at"`
	Type        string    `json:"type"` // "collection"
}

// SearchResult contains the search results
type SearchResult struct {
	Files            []*FileDocument       `json:"files"`
	Collections      []*CollectionDocument `json:"collections"`
	TotalFiles       int                   `json:"total_files"`
	TotalCollections int                   `json:"total_collections"`
	TotalHits        uint64                `json:"total_hits"`
	MaxScore         float64               `json:"max_score"`
	Took             time.Duration         `json:"took"`
	Query            string                `json:"query"`
}

// searchService implements SearchService
type searchService struct {
	index         bleve.Index
	configService config.ConfigService
	logger        *zap.Logger
}

// New creates a new search service
func New(configService config.ConfigService, logger *zap.Logger) SearchService {
	return &searchService{
		configService: configService,
		logger:        logger,
	}
}

// Initialize opens or creates the search index for the specified user
func (s *searchService) Initialize(ctx context.Context, userEmail string) error {
	if userEmail == "" {
		return fmt.Errorf("user email is required")
	}

	// Get search index path
	indexPath, err := s.configService.GetUserSearchIndexDir(ctx, userEmail)
	if err != nil {
		return fmt.Errorf("failed to get search index path: %w", err)
	}

	if indexPath == "" {
		return fmt.Errorf("search index path is empty")
	}

	s.logger.Info("Initializing search index", zap.String("path", indexPath))

	// Try to open existing index
	index, err := bleve.Open(indexPath)
	if err == bleve.ErrorIndexPathDoesNotExist {
		// Create new index
		s.logger.Info("Creating new search index")
		indexMapping := buildIndexMapping()
		index, err = bleve.New(indexPath, indexMapping)
		if err != nil {
			return fmt.Errorf("failed to create search index: %w", err)
		}
	} else if err != nil {
		return fmt.Errorf("failed to open search index: %w", err)
	}

	s.index = index
	s.logger.Info("Search index initialized successfully")

	return nil
}

// Close closes the search index
func (s *searchService) Close() error {
	if s.index != nil {
		err := s.index.Close()
		s.index = nil
		return err
	}
	return nil
}

// IndexFile adds or updates a file in the search index
func (s *searchService) IndexFile(file *FileDocument) error {
	if s.index == nil {
		return fmt.Errorf("search index not initialized")
	}

	file.Type = "file"
	return s.index.Index(file.ID, file)
}

// IndexCollection adds or updates a collection in the search index
func (s *searchService) IndexCollection(collection *CollectionDocument) error {
	if s.index == nil {
		return fmt.Errorf("search index not initialized")
	}

	collection.Type = "collection"
	return s.index.Index(collection.ID, collection)
}

// DeleteFile removes a file from the search index
func (s *searchService) DeleteFile(fileID string) error {
	if s.index == nil {
		return fmt.Errorf("search index not initialized")
	}

	return s.index.Delete(fileID)
}

// DeleteCollection removes a collection from the search index
func (s *searchService) DeleteCollection(collectionID string) error {
	if s.index == nil {
		return fmt.Errorf("search index not initialized")
	}

	return s.index.Delete(collectionID)
}

// Search performs a full-text search across files and collections.
//
// The search supports:
//   - Simple queries: automatically wrapped with wildcards for substring matching
//   - Advanced queries: use Bleve query syntax directly (+, -, "", *, ?)
//
// Examples:
//   - "mesh" → matches "meshtastic", "mesh_config", etc.
//   - "\"exact phrase\"" → matches exact phrase only
//   - "+required -excluded" → must contain "required", must not contain "excluded"
func (s *searchService) Search(query string, limit int) (*SearchResult, error) {
	if s.index == nil {
		return nil, fmt.Errorf("search index not initialized")
	}

	if limit <= 0 || limit > 100 {
		limit = 50
	}

	// Convert to lowercase for case-insensitive search
	searchQueryStr := strings.ToLower(query)

	// For simple queries (no operators), wrap with wildcards to enable substring matching.
	// This allows "mesh" to match "meshtastic_antenna.png".
	// If the user provides operators or wildcards, use their query as-is.
	if !strings.Contains(searchQueryStr, "*") && !strings.Contains(searchQueryStr, "?") &&
		!strings.Contains(searchQueryStr, "+") && !strings.Contains(searchQueryStr, "-") &&
		!strings.Contains(searchQueryStr, "\"") {
		searchQueryStr = "*" + searchQueryStr + "*"
	}

	searchQuery := bleve.NewQueryStringQuery(searchQueryStr)
	searchRequest := bleve.NewSearchRequest(searchQuery)
	searchRequest.Size = limit
	searchRequest.Fields = []string{"*"}
	searchRequest.Highlight = bleve.NewHighlight()

	// Execute search
	searchResults, err := s.index.Search(searchRequest)
	if err != nil {
		return nil, fmt.Errorf("search failed: %w", err)
	}

	// Parse results with deduplication
	result := &SearchResult{
		Files:       make([]*FileDocument, 0),
		Collections: make([]*CollectionDocument, 0),
		TotalHits:   searchResults.Total,
		MaxScore:    searchResults.MaxScore,
		Took:        searchResults.Took,
		Query:       query,
	}

	// Use maps to deduplicate by ID
	seenFileIDs := make(map[string]bool)
	seenCollectionIDs := make(map[string]bool)

	for _, hit := range searchResults.Hits {
		docType, ok := hit.Fields["type"].(string)
		if !ok {
			continue
		}

		if docType == "file" {
			// Skip if we've already seen this file ID
			if seenFileIDs[hit.ID] {
				s.logger.Warn("Duplicate file in search results", zap.String("id", hit.ID))
				continue
			}
			seenFileIDs[hit.ID] = true

			file := &FileDocument{
				ID:             hit.ID,
				Filename:       getStringField(hit.Fields, "filename"),
				Description:    getStringField(hit.Fields, "description"),
				CollectionID:   getStringField(hit.Fields, "collection_id"),
				CollectionName: getStringField(hit.Fields, "collection_name"),
				Tags:           getStringArrayField(hit.Fields, "tags"),
				Size:           getInt64Field(hit.Fields, "size"),
			}
			if createdAt, ok := hit.Fields["created_at"].(string); ok {
				file.CreatedAt, _ = time.Parse(time.RFC3339, createdAt)
			}
			result.Files = append(result.Files, file)
		} else if docType == "collection" {
			// Skip if we've already seen this collection ID
			if seenCollectionIDs[hit.ID] {
				s.logger.Warn("Duplicate collection in search results", zap.String("id", hit.ID))
				continue
			}
			seenCollectionIDs[hit.ID] = true

			collection := &CollectionDocument{
				ID:          hit.ID,
				Name:        getStringField(hit.Fields, "name"),
				Description: getStringField(hit.Fields, "description"),
				Tags:        getStringArrayField(hit.Fields, "tags"),
				FileCount:   getIntField(hit.Fields, "file_count"),
			}
			if createdAt, ok := hit.Fields["created_at"].(string); ok {
				collection.CreatedAt, _ = time.Parse(time.RFC3339, createdAt)
			}
			result.Collections = append(result.Collections, collection)
		}
	}

	result.TotalFiles = len(result.Files)
	result.TotalCollections = len(result.Collections)

	return result, nil
}

// RebuildIndex rebuilds the entire search index from scratch.
//
// This method:
//  1. Closes the existing index (if any)
//  2. Deletes the index directory completely
//  3. Creates a fresh new index
//  4. Batch-indexes all provided files and collections
//
// This approach ensures no stale or duplicate documents remain in the index.
// The userEmail is required to locate the user-specific index directory.
func (s *searchService) RebuildIndex(userEmail string, files []*FileDocument, collections []*CollectionDocument) error {
	s.logger.Info("Rebuilding search index from scratch",
		zap.Int("files", len(files)),
		zap.Int("collections", len(collections)))

	if userEmail == "" {
		return fmt.Errorf("user email is required for rebuild")
	}

	// Close the current index
	if s.index != nil {
		s.logger.Info("Closing current index before rebuild")
		if err := s.index.Close(); err != nil {
			s.logger.Warn("Error closing index before rebuild", zap.Error(err))
		}
		s.index = nil
	}

	// Get the index path from config
	ctx := context.Background()
	indexPath, err := s.configService.GetUserSearchIndexDir(ctx, userEmail)
	if err != nil {
		return fmt.Errorf("failed to get search index path: %w", err)
	}

	// Delete the existing index directory
	s.logger.Info("Deleting existing index", zap.String("path", indexPath))
	// We don't check for error here because the directory might not exist
	// and that's okay - we're about to create it
	os.RemoveAll(indexPath)

	// Create a fresh index
	s.logger.Info("Creating fresh index", zap.String("path", indexPath))
	indexMapping := buildIndexMapping()
	index, err := bleve.New(indexPath, indexMapping)
	if err != nil {
		return fmt.Errorf("failed to create fresh index: %w", err)
	}

	s.index = index

	// Now index all files and collections in a batch
	batch := s.index.NewBatch()

	// Index all files
	for _, file := range files {
		file.Type = "file"
		if err := batch.Index(file.ID, file); err != nil {
			s.logger.Error("Failed to batch index file", zap.String("id", file.ID), zap.Error(err))
		}
	}

	// Index all collections
	for _, collection := range collections {
		collection.Type = "collection"
		if err := batch.Index(collection.ID, collection); err != nil {
			s.logger.Error("Failed to batch index collection", zap.String("id", collection.ID), zap.Error(err))
		}
	}

	// Execute batch
	if err := s.index.Batch(batch); err != nil {
		return fmt.Errorf("failed to execute batch index: %w", err)
	}

	finalCount, _ := s.index.DocCount()
	s.logger.Info("Search index rebuilt successfully",
		zap.Uint64("documents", finalCount),
		zap.Int("files_indexed", len(files)),
		zap.Int("collections_indexed", len(collections)))

	return nil
}

// GetIndexSize returns the size of the search index in bytes
func (s *searchService) GetIndexSize() (int64, error) {
	if s.index == nil {
		return 0, fmt.Errorf("search index not initialized")
	}

	// Note: Bleve doesn't provide a direct way to get index size
	// We return the document count as a proxy for size
	// For actual disk usage, you would need to walk the index directory
	count, err := s.index.DocCount()
	if err != nil {
		return 0, err
	}
	return int64(count), nil
}

// GetDocumentCount returns the number of documents in the index
func (s *searchService) GetDocumentCount() (uint64, error) {
	if s.index == nil {
		return 0, fmt.Errorf("search index not initialized")
	}

	count, err := s.index.DocCount()
	if err != nil {
		return 0, err
	}

	return count, nil
}

// buildIndexMapping creates the Bleve index mapping for files and collections.
//
// Field types:
//   - Text fields (filename, description, name, tags): Analyzed with "standard" analyzer
//     for good tokenization without stemming (better for substring matching)
//   - Keyword fields (collection_id, type): Exact match only, no analysis
//   - Numeric fields (size, file_count): Stored as numbers for range queries
//   - Date fields (created_at): Stored as datetime for date-based queries
func buildIndexMapping() mapping.IndexMapping {
	indexMapping := bleve.NewIndexMapping()

	// Use standard analyzer (not English) for better substring matching.
	// The English analyzer applies stemming which can interfere with partial matches.
	textFieldMapping := bleve.NewTextFieldMapping()
	textFieldMapping.Analyzer = "standard"

	// Create keyword field mapping (no analysis)
	keywordFieldMapping := bleve.NewKeywordFieldMapping()

	// Create numeric field mapping
	numericFieldMapping := bleve.NewNumericFieldMapping()

	// Create datetime field mapping
	dateFieldMapping := bleve.NewDateTimeFieldMapping()

	// File document mapping
	fileMapping := bleve.NewDocumentMapping()
	fileMapping.AddFieldMappingsAt("filename", textFieldMapping)
	fileMapping.AddFieldMappingsAt("description", textFieldMapping)
	fileMapping.AddFieldMappingsAt("collection_name", textFieldMapping)
	fileMapping.AddFieldMappingsAt("tags", textFieldMapping)
	fileMapping.AddFieldMappingsAt("collection_id", keywordFieldMapping)
	fileMapping.AddFieldMappingsAt("size", numericFieldMapping)
	fileMapping.AddFieldMappingsAt("created_at", dateFieldMapping)
	fileMapping.AddFieldMappingsAt("type", keywordFieldMapping)

	// Collection document mapping
	collectionMapping := bleve.NewDocumentMapping()
	collectionMapping.AddFieldMappingsAt("name", textFieldMapping)
	collectionMapping.AddFieldMappingsAt("description", textFieldMapping)
	collectionMapping.AddFieldMappingsAt("tags", textFieldMapping)
	collectionMapping.AddFieldMappingsAt("file_count", numericFieldMapping)
	collectionMapping.AddFieldMappingsAt("created_at", dateFieldMapping)
	collectionMapping.AddFieldMappingsAt("type", keywordFieldMapping)

	indexMapping.AddDocumentMapping("file", fileMapping)
	indexMapping.AddDocumentMapping("collection", collectionMapping)

	return indexMapping
}

// Helper functions to extract fields from search results

func getStringField(fields map[string]interface{}, key string) string {
	if val, ok := fields[key].(string); ok {
		return val
	}
	return ""
}

func getStringArrayField(fields map[string]interface{}, key string) []string {
	if val, ok := fields[key].([]interface{}); ok {
		result := make([]string, 0, len(val))
		for _, v := range val {
			if str, ok := v.(string); ok {
				result = append(result, str)
			}
		}
		return result
	}
	return []string{}
}

func getIntField(fields map[string]interface{}, key string) int {
	if val, ok := fields[key].(float64); ok {
		return int(val)
	}
	return 0
}

func getInt64Field(fields map[string]interface{}, key string) int64 {
	if val, ok := fields[key].(float64); ok {
		return int64(val)
	}
	return 0
}