package commands

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"time"

	"github.com/blevesearch/bleve/v2"
	"github.com/spf13/cobra"
	"tercul/internal/data/sql"
	"tercul/internal/domain"
	"tercul/internal/platform/config"
	"tercul/internal/platform/db"
	"tercul/internal/platform/log"
)

const (
	// Default batch size for processing translations
	defaultBatchSize = 50000
	// Checkpoint file to track progress
	checkpointFile = ".bleve_migration_checkpoint"
)

type checkpoint struct {
	LastProcessedID uint      `json:"last_processed_id"`
	TotalProcessed    int       `json:"total_processed"`
	LastUpdated    time.Time `json:"last_updated"`
}

// NewBleveMigrateCommand creates a new Cobra command for Bleve migration
func NewBleveMigrateCommand() *cobra.Command {
	var (
		indexPath string
		batchSize int
		resume    bool
		verify    bool
	)

	cmd := &cobra.Command{
		Use:   "bleve-migrate",
		Short: "Migrate translations from PostgreSQL to Bleve index",
		Long: `Migrate all translations from PostgreSQL database to a Bleve search index.

This command:
- Fetches all translations from the database
- Indexes them in batches for efficient processing
- Supports resuming from checkpoints
- Provides progress tracking
- Can verify indexed data after migration

Example:
  tercul bleve-migrate --index ./data/bleve_index --batch 50000 --verify`,
		RunE: func(cmd *cobra.Command, args []string) error {
			if indexPath == "" {
				return fmt.Errorf("index path is required (use --index flag)")
			}

			// Initialize logger
			log.Init("bleve-migrate", "development")
			logger := log.FromContext(context.Background())

			// Load configuration
			cfg, err := config.LoadConfig()
			if err != nil {
				return fmt.Errorf("failed to load config: %w", err)
			}

			// Initialize database
			database, err := db.InitDB(cfg, nil)
			if err != nil {
				return fmt.Errorf("failed to initialize database: %w", err)
			}
			defer func() {
				if err := db.Close(database); err != nil {
					logger.Error(err, "Error closing database")
				}
			}()

			// Create repositories
			repos := sql.NewRepositories(database, cfg)

			// Initialize or open Bleve index
			logger.Info(fmt.Sprintf("Initializing Bleve index at %s", indexPath))
			index, err := initBleveIndex(indexPath)
			if err != nil {
				return fmt.Errorf("failed to initialize Bleve index: %w", err)
			}
			defer func() {
				if err := index.Close(); err != nil {
					logger.Error(err, "Error closing Bleve index")
				}
			}()

			// Load checkpoint if resuming
			var cp *checkpoint
			if resume {
				cp = loadCheckpoint()
				if cp != nil {
					logger.Info(fmt.Sprintf("Resuming from checkpoint: last_id=%d, total_processed=%d", cp.LastProcessedID, cp.TotalProcessed))
				}
			}

			// Run migration
			ctx := context.Background()
			stats, err := migrateTranslations(ctx, repos.Translation, index, batchSize, cp, logger, ctx)
			if err != nil {
				return fmt.Errorf("migration failed: %w", err)
			}

			logger.Info(fmt.Sprintf("Migration completed: indexed=%d, errors=%d, duration=%v", stats.TotalIndexed, stats.TotalErrors, stats.Duration))

			// Verify if requested
			if verify {
				logger.Info("Verifying indexed translations")
				if err := verifyIndex(index, repos.Translation, logger, ctx); err != nil {
					return fmt.Errorf("verification failed: %w", err)
				}
				logger.Info("Verification completed successfully")
			}

			// Clean up checkpoint file
			if err := os.Remove(checkpointFile); err != nil && !os.IsNotExist(err) {
				logger.Warn(fmt.Sprintf("Failed to remove checkpoint file: %v", err))
			}

			return nil
		},
	}

	// Add flags
	cmd.Flags().StringVarP(&indexPath, "index", "i", "", "Path to Bleve index directory (required)")
	cmd.Flags().IntVarP(&batchSize, "batch", "b", defaultBatchSize, "Batch size for processing translations")
	cmd.Flags().BoolVarP(&resume, "resume", "r", false, "Resume from last checkpoint")
	cmd.Flags().BoolVarP(&verify, "verify", "v", false, "Verify indexed translations after migration")

	// Mark index as required
	_ = cmd.MarkFlagRequired("index")

	return cmd
}

// initBleveIndex creates or opens a Bleve index with the appropriate mapping for translations
func initBleveIndex(indexPath string) (bleve.Index, error) {
	// Check if index already exists
	index, err := bleve.Open(indexPath)
	if err == nil {
		return index, nil
	}

	// Index doesn't exist, create it
	mapping := bleve.NewIndexMapping()

	// Create document mapping for Translation
	translationMapping := bleve.NewDocumentMapping()

	// ID field (not analyzed, stored)
	idMapping := bleve.NewTextFieldMapping()
	idMapping.Store = true
	idMapping.Index = true
	idMapping.Analyzer = "keyword"
	translationMapping.AddFieldMappingsAt("id", idMapping)

	// Title field (analyzed, stored)
	titleMapping := bleve.NewTextFieldMapping()
	titleMapping.Store = true
	titleMapping.Index = true
	titleMapping.Analyzer = "standard"
	translationMapping.AddFieldMappingsAt("title", titleMapping)

	// Content field (analyzed, stored)
	contentMapping := bleve.NewTextFieldMapping()
	contentMapping.Store = true
	contentMapping.Index = true
	contentMapping.Analyzer = "standard"
	translationMapping.AddFieldMappingsAt("content", contentMapping)

	// Description field (analyzed, stored)
	descriptionMapping := bleve.NewTextFieldMapping()
	descriptionMapping.Store = true
	descriptionMapping.Index = true
	descriptionMapping.Analyzer = "standard"
	translationMapping.AddFieldMappingsAt("description", descriptionMapping)

	// Language field (not analyzed, stored, for filtering)
	languageMapping := bleve.NewTextFieldMapping()
	languageMapping.Store = true
	languageMapping.Index = true
	languageMapping.Analyzer = "keyword"
	translationMapping.AddFieldMappingsAt("language", languageMapping)

	// Status field (not analyzed, stored, for filtering)
	statusMapping := bleve.NewTextFieldMapping()
	statusMapping.Store = true
	statusMapping.Index = true
	statusMapping.Analyzer = "keyword"
	translationMapping.AddFieldMappingsAt("status", statusMapping)

	// TranslatableID field (not analyzed, stored)
	translatableIDMapping := bleve.NewNumericFieldMapping()
	translatableIDMapping.Store = true
	translatableIDMapping.Index = true
	translationMapping.AddFieldMappingsAt("translatable_id", translatableIDMapping)

	// TranslatableType field (not analyzed, stored, for filtering)
	translatableTypeMapping := bleve.NewTextFieldMapping()
	translatableTypeMapping.Store = true
	translatableTypeMapping.Index = true
	translatableTypeMapping.Analyzer = "keyword"
	translationMapping.AddFieldMappingsAt("translatable_type", translatableTypeMapping)

	// TranslatorID field (not analyzed, stored)
	translatorIDMapping := bleve.NewNumericFieldMapping()
	translatorIDMapping.Store = true
	translatorIDMapping.Index = true
	translationMapping.AddFieldMappingsAt("translator_id", translatorIDMapping)

	// Add translation mapping to index
	mapping.AddDocumentMapping("translation", translationMapping)

	// Create index directory if it doesn't exist
	if err := os.MkdirAll(filepath.Dir(indexPath), 0755); err != nil {
		return nil, fmt.Errorf("failed to create index directory: %w", err)
	}

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

	return index, nil
}

type migrationStats struct {
	TotalIndexed int
	TotalErrors  int
	Duration     time.Duration
}

// migrateTranslations migrates all translations from PostgreSQL to Bleve index
func migrateTranslations(
	ctx context.Context,
	repo domain.TranslationRepository,
	index bleve.Index,
	batchSize int,
	cp *checkpoint,
	logger *log.Logger,
	ctxForLog context.Context,
) (*migrationStats, error) {
	startTime := time.Now()
	stats := &migrationStats{}

	// Fetch all translations
	logger.Info("Fetching all translations from database")
	translations, err := repo.ListAll(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch translations: %w", err)
	}

	totalTranslations := len(translations)
	logger.Info(fmt.Sprintf("Found %d translations", totalTranslations))

	// Filter translations if resuming from checkpoint
	if cp != nil && cp.LastProcessedID > 0 {
		filtered := make([]domain.Translation, 0, len(translations))
		for _, t := range translations {
			if t.ID > cp.LastProcessedID {
				filtered = append(filtered, t)
			}
		}
		translations = filtered
		stats.TotalIndexed = cp.TotalProcessed
		logger.Info(fmt.Sprintf("Filtered translations: remaining=%d, already_processed=%d", len(translations), cp.TotalProcessed))
	}

	// Process translations in batches
	batch := make([]domain.Translation, 0, batchSize)
	lastProcessedID := uint(0)

	for i, translation := range translations {
		batch = append(batch, translation)
		lastProcessedID = translation.ID

		// Process batch when it reaches the batch size or at the end
		if len(batch) >= batchSize || i == len(translations)-1 {
			if err := indexBatch(index, batch, logger); err != nil {
				logger.Error(err, fmt.Sprintf("Failed to index batch of size %d", len(batch)))
				stats.TotalErrors += len(batch)
				// Continue with next batch instead of failing completely
			} else {
				stats.TotalIndexed += len(batch)
			}

			// Save checkpoint
			cpData := checkpoint{
				LastProcessedID: lastProcessedID,
				TotalProcessed:  stats.TotalIndexed,
				LastUpdated:     time.Now(),
			}
			if err := saveCheckpoint(&cpData); err != nil {
				logger.Warn(fmt.Sprintf("Failed to save checkpoint: %v", err))
			}

			// Log progress
			progress := float64(stats.TotalIndexed) / float64(totalTranslations) * 100
			logger.Info(fmt.Sprintf("Migration progress: %d/%d (%.2f%%)", stats.TotalIndexed, totalTranslations, progress))

			// Clear batch
			batch = batch[:0]
		}
	}

	stats.Duration = time.Since(startTime)
	return stats, nil
}

// indexBatch indexes a batch of translations
func indexBatch(index bleve.Index, translations []domain.Translation, logger *log.Logger) error {
	batch := index.NewBatch()
	for _, t := range translations {
		doc := map[string]interface{}{
			"id":                strconv.FormatUint(uint64(t.ID), 10),
			"title":             t.Title,
			"content":           t.Content,
			"description":       t.Description,
			"language":          t.Language,
			"status":            string(t.Status),
			"translatable_id":   t.TranslatableID,
			"translatable_type": t.TranslatableType,
		}

		if t.TranslatorID != nil {
			doc["translator_id"] = *t.TranslatorID
		}

		docID := fmt.Sprintf("translation_%d", t.ID)
		if err := batch.Index(docID, doc); err != nil {
			return fmt.Errorf("failed to add document to batch: %w", err)
		}
	}

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

	return nil
}

// verifyIndex verifies that all translations in the database are indexed in Bleve
func verifyIndex(index bleve.Index, repo domain.TranslationRepository, logger *log.Logger, ctx context.Context) error {
	// Fetch all translations
	translations, err := repo.ListAll(ctx)
	if err != nil {
		return fmt.Errorf("failed to fetch translations: %w", err)
	}

	logger.Info(fmt.Sprintf("Verifying %d indexed translations", len(translations)))

	missing := 0
	for _, t := range translations {
		docID := fmt.Sprintf("translation_%d", t.ID)
		doc, err := index.Document(docID)
		if err != nil {
			logger.Warn(fmt.Sprintf("Translation %d not found in index: %v", t.ID, err))
			missing++
			continue
		}
		if doc == nil {
			logger.Warn(fmt.Sprintf("Translation %d not found in index (nil document)", t.ID))
			missing++
			continue
		}
	}

	if missing > 0 {
		return fmt.Errorf("verification failed: %d translations missing from index", missing)
	}

	logger.Info("All translations verified in index")
	return nil
}

// saveCheckpoint saves the migration checkpoint to a file
func saveCheckpoint(cp *checkpoint) error {
	data, err := json.Marshal(cp)
	if err != nil {
		return fmt.Errorf("failed to marshal checkpoint: %w", err)
	}

	if err := os.WriteFile(checkpointFile, data, 0644); err != nil {
		return fmt.Errorf("failed to write checkpoint file: %w", err)
	}

	return nil
}

// loadCheckpoint loads the migration checkpoint from a file
func loadCheckpoint() *checkpoint {
	data, err := os.ReadFile(checkpointFile)
	if err != nil {
		return nil
	}

	var cp checkpoint
	if err := json.Unmarshal(data, &cp); err != nil {
		return nil
	}

	return &cp
}