package storage

import (
	"context"
	"encoding/json"
	"fmt"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/blevesearch/bleve/v2"
	"github.com/blevesearch/bleve/v2/analysis/analyzer/standard"
	"github.com/blevesearch/bleve/v2/analysis/lang/en"
	"github.com/blevesearch/bleve/v2/mapping"
	"github.com/anthonyrawlins/bzzz/pkg/ucxl"
	slurpContext "github.com/anthonyrawlins/bzzz/pkg/slurp/context"
)

// IndexManagerImpl implements the IndexManager interface using Bleve
type IndexManagerImpl struct {
	mu         sync.RWMutex
	indexes    map[string]bleve.Index
	stats      map[string]*IndexStatistics
	basePath   string
	nodeID     string
	options    *IndexManagerOptions
}

// IndexManagerOptions configures index manager behavior
type IndexManagerOptions struct {
	DefaultAnalyzer    string        `json:"default_analyzer"`
	MaxDocumentSize    int64         `json:"max_document_size"`
	RefreshInterval    time.Duration `json:"refresh_interval"`
	OptimizeInterval   time.Duration `json:"optimize_interval"`
	EnableHighlighting bool          `json:"enable_highlighting"`
	EnableFaceting     bool          `json:"enable_faceting"`
	BatchSize          int           `json:"batch_size"`
	MaxResults         int           `json:"max_results"`
}

// DefaultIndexManagerOptions returns sensible defaults
func DefaultIndexManagerOptions() *IndexManagerOptions {
	return &IndexManagerOptions{
		DefaultAnalyzer:    "standard",
		MaxDocumentSize:    10 * 1024 * 1024, // 10MB
		RefreshInterval:    5 * time.Minute,
		OptimizeInterval:   1 * time.Hour,
		EnableHighlighting: true,
		EnableFaceting:     true,
		BatchSize:          100,
		MaxResults:         1000,
	}
}

// NewIndexManager creates a new index manager
func NewIndexManager(basePath, nodeID string, options *IndexManagerOptions) (*IndexManagerImpl, error) {
	if options == nil {
		options = DefaultIndexManagerOptions()
	}

	im := &IndexManagerImpl{
		indexes:   make(map[string]bleve.Index),
		stats:     make(map[string]*IndexStatistics),
		basePath:  basePath,
		nodeID:    nodeID,
		options:   options,
	}

	// Start background optimization if enabled
	if options.OptimizeInterval > 0 {
		go im.optimizationLoop()
	}

	return im, nil
}

// CreateIndex creates a search index for contexts
func (im *IndexManagerImpl) CreateIndex(
	ctx context.Context,
	indexName string,
	config *IndexConfig,
) error {
	im.mu.Lock()
	defer im.mu.Unlock()

	// Check if index already exists
	if _, exists := im.indexes[indexName]; exists {
		return fmt.Errorf("index %s already exists", indexName)
	}

	// Create index mapping
	mapping, err := im.createIndexMapping(config)
	if err != nil {
		return fmt.Errorf("failed to create index mapping: %w", err)
	}

	// Create the index
	indexPath := fmt.Sprintf("%s/%s.bleve", im.basePath, indexName)
	index, err := bleve.New(indexPath, mapping)
	if err != nil {
		return fmt.Errorf("failed to create index: %w", err)
	}

	// Store the index
	im.indexes[indexName] = index
	im.stats[indexName] = &IndexStatistics{
		Name:             indexName,
		LastUpdate:       time.Now(),
		LastOptimization: time.Now(),
	}

	return nil
}

// UpdateIndex updates search index with new data
func (im *IndexManagerImpl) UpdateIndex(
	ctx context.Context,
	indexName string,
	key string,
	data interface{},
) error {
	im.mu.RLock()
	index, exists := im.indexes[indexName]
	stats := im.stats[indexName]
	im.mu.RUnlock()

	if !exists {
		return fmt.Errorf("index %s does not exist", indexName)
	}

	// Create indexable document from context data
	doc, err := im.createIndexDocument(data)
	if err != nil {
		return fmt.Errorf("failed to create index document: %w", err)
	}

	// Check document size
	docSize := im.estimateDocumentSize(doc)
	if docSize > im.options.MaxDocumentSize {
		return fmt.Errorf("document too large: %d bytes exceeds limit of %d", docSize, im.options.MaxDocumentSize)
	}

	// Index the document
	start := time.Now()
	if err := index.Index(key, doc); err != nil {
		return fmt.Errorf("failed to index document: %w", err)
	}

	// Update statistics
	im.mu.Lock()
	stats.DocumentCount++
	stats.LastUpdate = time.Now()
	stats.IndexSize += docSize
	updateTime := time.Since(start)

	// Update average indexing time
	if stats.AverageQueryTime == 0 {
		stats.AverageQueryTime = updateTime
	} else {
		stats.AverageQueryTime = time.Duration(
			float64(stats.AverageQueryTime)*0.9 + float64(updateTime)*0.1,
		)
	}
	im.mu.Unlock()

	return nil
}

// DeleteFromIndex removes data from search index
func (im *IndexManagerImpl) DeleteFromIndex(
	ctx context.Context,
	indexName string,
	key string,
) error {
	im.mu.RLock()
	index, exists := im.indexes[indexName]
	stats := im.stats[indexName]
	im.mu.RUnlock()

	if !exists {
		return fmt.Errorf("index %s does not exist", indexName)
	}

	// Delete the document
	if err := index.Delete(key); err != nil {
		return fmt.Errorf("failed to delete document: %w", err)
	}

	// Update statistics
	im.mu.Lock()
	if stats.DocumentCount > 0 {
		stats.DocumentCount--
	}
	stats.LastUpdate = time.Now()
	im.mu.Unlock()

	return nil
}

// Search searches indexed data using query
func (im *IndexManagerImpl) Search(
	ctx context.Context,
	indexName string,
	query *SearchQuery,
) (*SearchResults, error) {
	start := time.Now()
	defer func() {
		im.updateSearchStats(indexName, time.Since(start))
	}()

	im.mu.RLock()
	index, exists := im.indexes[indexName]
	im.mu.RUnlock()

	if !exists {
		return nil, fmt.Errorf("index %s does not exist", indexName)
	}

	// Build search request
	searchRequest, err := im.buildSearchRequest(query)
	if err != nil {
		return nil, fmt.Errorf("failed to build search request: %w", err)
	}

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

	// Convert to our search results format
	results, err := im.convertSearchResults(searchResult, query)
	if err != nil {
		return nil, fmt.Errorf("failed to convert search results: %w", err)
	}

	return results, nil
}

// RebuildIndex rebuilds search index from stored data
func (im *IndexManagerImpl) RebuildIndex(
	ctx context.Context,
	indexName string,
) error {
	im.mu.Lock()
	defer im.mu.Unlock()

	index, exists := im.indexes[indexName]
	if !exists {
		return fmt.Errorf("index %s does not exist", indexName)
	}

	// Close current index
	if err := index.Close(); err != nil {
		return fmt.Errorf("failed to close index: %w", err)
	}

	// Delete index files
	indexPath := fmt.Sprintf("%s/%s.bleve", im.basePath, indexName)
	// Note: In production, you'd want to use proper file system operations
	// to delete the index directory

	// Recreate index with same configuration
	// This is a simplified implementation - in practice you'd need to
	// recreate with the original configuration and re-index all documents
	mapping := bleve.NewIndexMapping()
	newIndex, err := bleve.New(indexPath, mapping)
	if err != nil {
		return fmt.Errorf("failed to recreate index: %w", err)
	}

	// Replace in memory
	im.indexes[indexName] = newIndex
	im.stats[indexName].DocumentCount = 0
	im.stats[indexName].LastUpdate = time.Now()
	im.stats[indexName].LastOptimization = time.Now()

	return nil
}

// OptimizeIndex optimizes search index for performance
func (im *IndexManagerImpl) OptimizeIndex(
	ctx context.Context,
	indexName string,
) error {
	im.mu.RLock()
	index, exists := im.indexes[indexName]
	stats := im.stats[indexName]
	im.mu.RUnlock()

	if !exists {
		return fmt.Errorf("index %s does not exist", indexName)
	}

	// Bleve doesn't have explicit optimization, but we can force a merge
	// This is a no-op for Bleve, but we update stats
	im.mu.Lock()
	stats.LastOptimization = time.Now()
	stats.FragmentationRatio = im.calculateFragmentationRatio(index)
	im.mu.Unlock()

	return nil
}

// GetIndexStats returns index statistics
func (im *IndexManagerImpl) GetIndexStats(
	ctx context.Context,
	indexName string,
) (*IndexStatistics, error) {
	im.mu.RLock()
	stats, exists := im.stats[indexName]
	im.mu.RUnlock()

	if !exists {
		return nil, fmt.Errorf("index %s does not exist", indexName)
	}

	// Return a copy
	statsCopy := *stats
	return &statsCopy, nil
}

// ListIndexes lists all available indexes
func (im *IndexManagerImpl) ListIndexes(ctx context.Context) ([]string, error) {
	im.mu.RLock()
	defer im.mu.RUnlock()

	var indexNames []string
	for name := range im.indexes {
		indexNames = append(indexNames, name)
	}

	sort.Strings(indexNames)
	return indexNames, nil
}

// Helper methods

func (im *IndexManagerImpl) createIndexMapping(config *IndexConfig) (mapping.IndexMapping, error) {
	// Create a new index mapping
	indexMapping := bleve.NewIndexMapping()

	// Configure default analyzer
	analyzer := config.Analyzer
	if analyzer == "" {
		analyzer = im.options.DefaultAnalyzer
	}

	// Set document mapping
	docMapping := bleve.NewDocumentMapping()

	// Map context fields
	for _, field := range config.Fields {
		fieldMapping := bleve.NewTextFieldMapping()
		fieldMapping.Analyzer = analyzer
		fieldMapping.Store = true
		fieldMapping.Index = true
		
		if im.options.EnableHighlighting {
			fieldMapping.IncludeTermVectors = true
		}
		
		docMapping.AddFieldMappingsAt(field, fieldMapping)
	}

	// Add special fields for faceting if enabled
	if im.options.EnableFaceting {
		// Add tags as keyword field for faceting
		tagsMapping := bleve.NewKeywordFieldMapping()
		tagsMapping.Store = true
		tagsMapping.Index = true
		docMapping.AddFieldMappingsAt("tags_facet", tagsMapping)

		// Add technologies as keyword field for faceting
		techMapping := bleve.NewKeywordFieldMapping()
		techMapping.Store = true
		techMapping.Index = true
		docMapping.AddFieldMappingsAt("technologies_facet", techMapping)
	}

	// Set default document type
	indexMapping.DefaultMapping = docMapping

	// Configure analyzers
	if config.Language == "en" {
		indexMapping.DefaultAnalyzer = en.AnalyzerName
	} else {
		indexMapping.DefaultAnalyzer = standard.Name
	}

	return indexMapping, nil
}

func (im *IndexManagerImpl) createIndexDocument(data interface{}) (map[string]interface{}, error) {
	// Convert context node to indexable document
	contextNode, ok := data.(*slurpContext.ContextNode)
	if !ok {
		return nil, fmt.Errorf("unsupported data type for indexing")
	}

	doc := map[string]interface{}{
		"path":                contextNode.Path,
		"ucxl_address":        contextNode.UCXLAddress.String(),
		"summary":             contextNode.Summary,
		"purpose":             contextNode.Purpose,
		"technologies":        strings.Join(contextNode.Technologies, " "),
		"tags":                strings.Join(contextNode.Tags, " "),
		"insights":            strings.Join(contextNode.Insights, " "),
		"overrides_parent":    contextNode.OverridesParent,
		"context_specificity": contextNode.ContextSpecificity,
		"applies_to_children": contextNode.AppliesToChildren,
		"rag_confidence":      contextNode.RAGConfidence,
		"generated_at":        contextNode.GeneratedAt,
	}

	// Add faceting fields if enabled
	if im.options.EnableFaceting {
		doc["tags_facet"] = contextNode.Tags
		doc["technologies_facet"] = contextNode.Technologies
	}

	// Create searchable content by combining key fields
	combinedContent := fmt.Sprintf("%s %s %s %s",
		contextNode.Summary,
		contextNode.Purpose,
		strings.Join(contextNode.Technologies, " "),
		strings.Join(contextNode.Insights, " "),
	)
	doc["content"] = combinedContent

	return doc, nil
}

func (im *IndexManagerImpl) buildSearchRequest(query *SearchQuery) (*bleve.SearchRequest, error) {
	// Build Bleve search request from our search query
	var bleveQuery bleve.Query

	if query.Query == "" {
		// Match all query
		bleveQuery = bleve.NewMatchAllQuery()
	} else {
		// Text search query
		if query.FuzzyMatch {
			// Use fuzzy query
			bleveQuery = bleve.NewFuzzyQuery(query.Query)
		} else {
			// Use match query for better scoring
			bleveQuery = bleve.NewMatchQuery(query.Query)
		}
	}

	// Add filters
	var conjuncts []bleve.Query
	conjuncts = append(conjuncts, bleveQuery)

	// Technology filters
	if len(query.Technologies) > 0 {
		for _, tech := range query.Technologies {
			techQuery := bleve.NewTermQuery(tech)
			techQuery.SetField("technologies_facet")
			conjuncts = append(conjuncts, techQuery)
		}
	}

	// Tag filters
	if len(query.Tags) > 0 {
		for _, tag := range query.Tags {
			tagQuery := bleve.NewTermQuery(tag)
			tagQuery.SetField("tags_facet")
			conjuncts = append(conjuncts, tagQuery)
		}
	}

	// Combine all queries
	if len(conjuncts) > 1 {
		bleveQuery = bleve.NewConjunctionQuery(conjuncts...)
	}

	// Create search request
	searchRequest := bleve.NewSearchRequest(bleveQuery)
	
	// Set result options
	if query.Limit > 0 && query.Limit <= im.options.MaxResults {
		searchRequest.Size = query.Limit
	} else {
		searchRequest.Size = im.options.MaxResults
	}
	
	if query.Offset > 0 {
		searchRequest.From = query.Offset
	}

	// Enable highlighting if requested
	if query.HighlightTerms && im.options.EnableHighlighting {
		searchRequest.Highlight = bleve.NewHighlight()
		searchRequest.Highlight.AddField("content")
		searchRequest.Highlight.AddField("summary")
		searchRequest.Highlight.AddField("purpose")
	}

	// Add facets if requested
	if len(query.Facets) > 0 && im.options.EnableFaceting {
		searchRequest.Facets = make(bleve.FacetsRequest)
		for _, facet := range query.Facets {
			switch facet {
			case "technologies":
				searchRequest.Facets["technologies"] = bleve.NewFacetRequest("technologies_facet", 10)
			case "tags":
				searchRequest.Facets["tags"] = bleve.NewFacetRequest("tags_facet", 10)
			}
		}
	}

	// Set fields to return
	searchRequest.Fields = []string{"*"}

	return searchRequest, nil
}

func (im *IndexManagerImpl) convertSearchResults(
	searchResult *bleve.SearchResult,
	query *SearchQuery,
) (*SearchResults, error) {
	results := &SearchResults{
		Query:          query,
		Results:        make([]*SearchResult, 0, len(searchResult.Hits)),
		TotalResults:   int64(searchResult.Total),
		ProcessingTime: searchResult.Took,
		ProcessedAt:    time.Now(),
	}

	// Convert hits
	for i, hit := range searchResult.Hits {
		searchHit := &SearchResult{
			MatchScore:    hit.Score,
			MatchedFields: make([]string, 0),
			Highlights:   make(map[string][]string),
			Rank:          i + 1,
		}

		// Extract matched fields from hit
		for field := range hit.Fields {
			searchHit.MatchedFields = append(searchHit.MatchedFields, field)
		}

		// Extract highlights
		for field, fragments := range hit.Fragments {
			searchHit.Highlights[field] = fragments
		}

		// Create context node from hit data (simplified)
		contextNode := &slurpContext.ContextNode{
			Path:    hit.Fields["path"].(string),
			Summary: hit.Fields["summary"].(string),
			Purpose: hit.Fields["purpose"].(string),
		}

		// Parse UCXL address
		if ucxlStr, ok := hit.Fields["ucxl_address"].(string); ok {
			if addr, err := ucxl.ParseAddress(ucxlStr); err == nil {
				contextNode.UCXLAddress = addr
			}
		}

		searchHit.Context = contextNode
		results.Results = append(results.Results, searchHit)
	}

	// Convert facets
	if len(searchResult.Facets) > 0 {
		results.Facets = make(map[string]map[string]int)
		for facetName, facetResult := range searchResult.Facets {
			facetCounts := make(map[string]int)
			for _, term := range facetResult.Terms {
				facetCounts[term.Term] = term.Count
			}
			results.Facets[facetName] = facetCounts
		}
	}

	return results, nil
}

func (im *IndexManagerImpl) estimateDocumentSize(doc map[string]interface{}) int64 {
	// Rough estimation of document size
	docBytes, _ := json.Marshal(doc)
	return int64(len(docBytes))
}

func (im *IndexManagerImpl) calculateFragmentationRatio(index bleve.Index) float64 {
	// Simplified fragmentation calculation
	// In practice, this would analyze the index structure
	return 0.1 // Placeholder: 10% fragmentation
}

func (im *IndexManagerImpl) updateSearchStats(indexName string, duration time.Duration) {
	im.mu.Lock()
	defer im.mu.Unlock()

	stats, exists := im.stats[indexName]
	if !exists {
		return
	}

	stats.QueryCount++
	if stats.AverageQueryTime == 0 {
		stats.AverageQueryTime = duration
	} else {
		// Exponential moving average
		stats.AverageQueryTime = time.Duration(
			float64(stats.AverageQueryTime)*0.9 + float64(duration)*0.1,
		)
	}

	// Update success rate (simplified - assumes all queries succeed)
	stats.SuccessRate = 1.0
}

func (im *IndexManagerImpl) optimizationLoop() {
	ticker := time.NewTicker(im.options.OptimizeInterval)
	defer ticker.Stop()

	for range ticker.C {
		im.performOptimization()
	}
}

func (im *IndexManagerImpl) performOptimization() {
	im.mu.RLock()
	indexNames := make([]string, 0, len(im.indexes))
	for name := range im.indexes {
		indexNames = append(indexNames, name)
	}
	im.mu.RUnlock()

	// Optimize each index
	for _, indexName := range indexNames {
		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
		if err := im.OptimizeIndex(ctx, indexName); err != nil {
			// Log error but continue with other indexes
			fmt.Printf("Failed to optimize index %s: %v\n", indexName, err)
		}
		cancel()
	}
}

// Close closes all indexes and cleans up resources
func (im *IndexManagerImpl) Close() error {
	im.mu.Lock()
	defer im.mu.Unlock()

	for name, index := range im.indexes {
		if err := index.Close(); err != nil {
			fmt.Printf("Failed to close index %s: %v\n", name, err)
		}
	}

	im.indexes = make(map[string]bleve.Index)
	im.stats = make(map[string]*IndexStatistics)

	return nil
}