package services

import (
	"bookmann/internal/database"
	"context"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"

	epub "github.com/ArcadiaLin/go-epub"
	"github.com/fsnotify/fsnotify"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgtype"
)

type EbookMetadata struct {
	Title        string
	Author       string
	Description  string
	Series       string
	SeriesNumber int32
	Publisher    string
	PublishDate  time.Time
	Contributors string
	CoverPath    string
	ISBN         string
	Tags         string
}

type EbookScanner struct {
	db      *database.Queries
	watcher *fsnotify.Watcher
	folders []string
	adminID pgtype.UUID
}

func NewEbookScanner(db *database.Queries) *EbookScanner {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		panic(fmt.Sprintf("Failed to create file watcher: %v", err))
	}

	return &EbookScanner{
		db:      db,
		watcher: watcher,
	}
}

func (s *EbookScanner) SetAdminID(adminID pgtype.UUID) {
	s.adminID = adminID
}

func (s *EbookScanner) SetFolders(folders []string) error {
	s.folders = folders

	// Remove old watch if exists
	if s.watcher != nil {
		s.watcher.Close()
	}

	// Create new watcher
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return fmt.Errorf("failed to create watcher: %v", err)
	}
	s.watcher = watcher

	// Add all folders to watch
	for _, folder := range folders {
		if err := s.watcher.Add(folder); err != nil {
			fmt.Printf("Warning: failed to watch folder %s: %v\n", folder, err)
		}
	}

	return nil
}

func (s *EbookScanner) ScanFolders(ctx context.Context) error {
	if len(s.folders) == 0 {
		return fmt.Errorf("no folders set")
	}

	fmt.Printf("Starting scan of %d folders: %v\n", len(s.folders), s.folders)

	totalFiles := 0
	ebookFiles := 0

	for _, folder := range s.folders {
		fmt.Printf("Scanning folder: %s\n", folder)

		// Check if folder exists
		if _, err := os.Stat(folder); os.IsNotExist(err) {
			fmt.Printf("Folder does not exist: %s\n", folder)
			continue
		}

		err := filepath.WalkDir(folder, func(path string, d fs.DirEntry, err error) error {
			if err != nil {
				fmt.Printf("Error accessing path %s: %v\n", path, err)
				return err
			}

			totalFiles++

			if d.IsDir() {
				// Also watch subdirectories
				if err := s.watcher.Add(path); err != nil {
					fmt.Printf("Warning: failed to watch subdirectory %s: %v\n", path, err)
				}
				return nil
			}

			// Check if it's an ebook file
			if s.isEbookFile(path) {
				ebookFiles++
				fmt.Printf("Found ebook file: %s\n", path)
				if err := s.processEbookFile(ctx, path); err != nil {
					fmt.Printf("Error processing ebook %s: %v\n", path, err)
				} else {
					fmt.Printf("Successfully processed ebook: %s\n", path)
				}
			}

			return nil
		})
		if err != nil {
			return fmt.Errorf("failed to scan folder %s: %v", folder, err)
		}
	}

	fmt.Printf("Scan completed: %d total files scanned, %d ebook files found\n", totalFiles, ebookFiles)
	return nil
}

func (s *EbookScanner) isEbookFile(path string) bool {
	ext := strings.ToLower(filepath.Ext(path))
	switch ext {
	case ".epub", ".pdf", ".mobi", ".azw3", ".fb2", ".txt":
		return true
	default:
		return false
	}
}

// extractFolderStructureMetadata extracts metadata from folder paths, prioritizing Calibre structure
func (s *EbookScanner) extractFolderStructureMetadata(path, rootFolder string) *EbookMetadata {
	metadata := &EbookMetadata{}

	// Get the relative path from root folder
	relPath, err := filepath.Rel(rootFolder, path)
	if err != nil {
		return metadata
	}

	// Split into directory components
	dir := filepath.Dir(relPath)
	components := strings.Split(dir, string(filepath.Separator))

	if len(components) < 2 {
		return metadata // Not enough structure to extract
	}

	// Calibre structure detection
	// Pattern 1: Author Name/Book Title/
	// Pattern 2: Author Name/Series Name/Book Title/
	// Pattern 3: Author Name/Series Name, Book #1 - Book Title/

	author := strings.TrimSuffix(components[0], "_") // Remove trailing underscore if present
	metadata.Author = strings.ReplaceAll(author, "_", " ")

	if len(components) >= 3 {
		// This might be a series structure
		possibleSeries := components[1]
		possibleTitle := components[2]

		// Check for Calibre series format: "Series Name, Book #1 - Title"
		seriesMatch := regexp.MustCompile(`^(.*),\s+Book\s+#(\d+)\s*-\s*(.*)$`).FindStringSubmatch(possibleSeries)
		if len(seriesMatch) == 4 {
			metadata.Series = strings.ReplaceAll(seriesMatch[1], "_", " ")
			if seriesNum, err := strconv.ParseInt(seriesMatch[2], 10, 32); err == nil {
				metadata.SeriesNumber = int32(seriesNum)
			}
			metadata.Title = strings.ReplaceAll(possibleTitle, "_", " ")
		} else {
			// Simple series structure: Author/Series/Title
			metadata.Series = strings.ReplaceAll(possibleSeries, "_", " ")
			metadata.Title = strings.ReplaceAll(possibleTitle, "_", " ")

			// Try to extract series number from title
			titleNumMatch := regexp.MustCompile(`^(.*)\s+(\d+)$`).FindStringSubmatch(metadata.Title)
			if len(titleNumMatch) == 3 {
				metadata.Title = titleNumMatch[1]
				if seriesNum, err := strconv.ParseInt(titleNumMatch[2], 10, 32); err == nil {
					metadata.SeriesNumber = int32(seriesNum)
				}
			}
		}
	} else {
		// Simple structure: Author/Title
		metadata.Title = strings.ReplaceAll(components[1], "_", " ")
	}

	return metadata
}

func (s *EbookScanner) processEbookFile(ctx context.Context, path string) error {
	fmt.Printf("Processing ebook file: %s\n", path)

	// Get file info
	info, err := os.Stat(path)
	if err != nil {
		fmt.Printf("Failed to get file info for %s: %v\n", path, err)
		return fmt.Errorf("failed to get file info: %v", err)
	}

	fmt.Printf("File info for %s: size=%d\n", path, info.Size())

	// Check if ebook already exists in database
	existingEbook, err := s.getEbookByFilePath(ctx, path)
	if err == nil {
		fmt.Printf("Ebook already exists in database: %s (size: %d vs %d)\n", path, existingEbook.FileSize.Int64, info.Size())
		// Ebook exists, check if file has changed (by size)
		if existingEbook.FileSize.Int64 != info.Size() {
			fmt.Printf("File size changed, updating ebook: %s\n", path)
			return s.updateEbook(ctx, existingEbook.ID, path, info)
		}
		fmt.Printf("Ebook already exists with same size, skipping: %s\n", path)
		return nil // Skip if already exists and size matches
	} else if err != pgx.ErrNoRows {
		fmt.Printf("Database error checking ebook existence: %v\n", err)
		// Some other error occurred
		return fmt.Errorf("failed to check if ebook exists: %v", err)
	}
	fmt.Printf("Ebook does not exist in database, creating new entry: %s\n", path)

	// Extract metadata from file first
	metadata, err := s.extractMetadata(path)
	if err != nil {
		fmt.Printf("Warning: failed to extract metadata from %s: %v\n", path, err)
		metadata = &EbookMetadata{}
	}

	// Try to get metadata from folder structure as fallback/enhancement
	// Use the root folder that contains this file
	var rootFolder string
	for _, folder := range s.folders {
		if strings.HasPrefix(path, folder) {
			rootFolder = folder
			break
		}
	}

	if rootFolder != "" {
		folderMetadata := s.extractFolderStructureMetadata(path, rootFolder)

		// Use folder metadata as fallback for missing information
		if metadata.Title == "" && folderMetadata.Title != "" {
			metadata.Title = folderMetadata.Title
		}
		if metadata.Author == "" && folderMetadata.Author != "" {
			metadata.Author = folderMetadata.Author
		}
		if metadata.Series == "" && folderMetadata.Series != "" {
			metadata.Series = folderMetadata.Series
		}
		if metadata.SeriesNumber == 0 && folderMetadata.SeriesNumber > 0 {
			metadata.SeriesNumber = folderMetadata.SeriesNumber
		}
	}

	// Final fallback if still missing essential metadata
	if metadata.Title == "" {
		metadata.Title = strings.TrimSuffix(filepath.Base(path), filepath.Ext(path))
	}
	if metadata.Author == "" {
		metadata.Author = "Unknown"
	}

	// Create ebook in database
	_, err = s.db.CreateEbook(ctx, database.CreateEbookParams{
		Title:          metadata.Title,
		Author:         pgtype.Text{String: metadata.Author, Valid: metadata.Author != ""},
		Description:    pgtype.Text{String: metadata.Description, Valid: metadata.Description != ""},
		FilePath:       path,
		FileSize:       pgtype.Int8{Int64: info.Size(), Valid: true},
		MimeType:       pgtype.Text{String: s.getMimeType(path), Valid: true},
		CoverImagePath: pgtype.Text{String: metadata.CoverPath, Valid: metadata.CoverPath != ""},
		Series:         pgtype.Text{String: metadata.Series, Valid: metadata.Series != ""},
		SeriesNumber:   pgtype.Int4{Int32: metadata.SeriesNumber, Valid: metadata.SeriesNumber > 0},
		Publisher:      pgtype.Text{String: metadata.Publisher, Valid: metadata.Publisher != ""},
		DatePublished:  pgtype.Date{Time: metadata.PublishDate, Valid: !metadata.PublishDate.IsZero()},
		Contributors:   pgtype.Text{String: metadata.Contributors, Valid: metadata.Contributors != ""},
		Tags:           pgtype.Text{String: metadata.Tags, Valid: metadata.Tags != ""},
		AddedByAdminID: s.adminID,
	})

	return err
}

func (s *EbookScanner) extractMetadata(path string) (*EbookMetadata, error) {
	ext := strings.ToLower(filepath.Ext(path))

	switch ext {
	case ".epub":
		return s.extractEPUBMetadata(path)
	case ".pdf":
		return s.extractPDFMetadata(path)
	default:
		// For other formats, return basic metadata
		return &EbookMetadata{
			Title: strings.TrimSuffix(filepath.Base(path), ext),
		}, nil
	}
}

func (s *EbookScanner) extractEPUBMetadata(path string) (*EbookMetadata, error) {
	book, err := epub.ReadBook(path)
	if err != nil {
		return nil, fmt.Errorf("failed to open EPUB: %v", err)
	}

	metadata := &EbookMetadata{}

	// Title
	if title, err := book.Title(); err == nil && title != "" {
		metadata.Title = title
	}

	// Author
	if authors, err := book.MetadataByKey("creator"); err == nil && len(authors) > 0 {
		metadata.Author = authors[0]
	}

	// Description
	if descriptions, err := book.MetadataByKey("description"); err == nil && len(descriptions) > 0 {
		metadata.Description = descriptions[0]
	}

	// Publisher
	if publishers, err := book.MetadataByKey("publisher"); err == nil && len(publishers) > 0 {
		metadata.Publisher = publishers[0]
	}

	// Series and series number (Calibre specific metadata)
	if series, err := book.MetadataByKey("calibre:series"); err == nil && len(series) > 0 {
		metadata.Series = series[0]
	}
	if seriesIndex, err := book.MetadataByKey("calibre:series_index"); err == nil && len(seriesIndex) > 0 {
		if index, err := strconv.ParseFloat(seriesIndex[0], 32); err == nil {
			metadata.SeriesNumber = int32(index)
		}
	}

	// Publish date
	if dates, err := book.MetadataByKey("date"); err == nil && len(dates) > 0 {
		if date, err := time.Parse("2006-01-02", dates[0]); err == nil {
			metadata.PublishDate = date
		} else {
			// Try alternative date formats
			if date, err := time.Parse("2006", dates[0]); err == nil {
				metadata.PublishDate = date
			}
		}
	}

	// Contributors
	if contributors, err := book.MetadataByKey("contributor"); err == nil && len(contributors) > 0 {
		metadata.Contributors = strings.Join(contributors, ", ")
	}

	// ISBN
	if isbns, err := book.MetadataByKey("identifier"); err == nil && len(isbns) > 0 {
		for _, isbn := range isbns {
			if strings.Contains(strings.ToLower(isbn), "isbn") {
				// Extract ISBN number from identifier like "isbn:978-3-16-148410-0"
				isbnParts := strings.SplitN(isbn, ":", 2)
				if len(isbnParts) == 2 {
					metadata.ISBN = isbnParts[1]
					break
				}
			}
		}
	}

	// Tags
	if tags, err := book.MetadataByKey("subject"); err == nil && len(tags) > 0 {
		metadata.Tags = strings.Join(tags, ", ")
	}

	return metadata, nil
}

func (s *EbookScanner) extractPDFMetadata(path string) (*EbookMetadata, error) {
	// For now, return basic metadata since PDF extraction requires additional libraries
	// In a future enhancement, you could use libraries like github.com/ledongthuc/pdf
	filename := strings.TrimSuffix(filepath.Base(path), ".pdf")

	return &EbookMetadata{
		Title: filename,
	}, nil
}

func (s *EbookScanner) updateEbook(ctx context.Context, ebookID pgtype.UUID, filePath string, info os.FileInfo) error {
	metadata, err := s.extractMetadata(filePath)
	if err != nil {
		fmt.Printf("Warning: failed to extract metadata from %s: %v\n", filePath, err)
		metadata = &EbookMetadata{
			Title: filepath.Base(filePath),
		}
	}

	_, err = s.db.UpdateEbook(ctx, database.UpdateEbookParams{
		ID:             ebookID,
		Title:          metadata.Title,
		Author:         pgtype.Text{String: metadata.Author, Valid: metadata.Author != ""},
		Isbn:           metadata.ISBN,
		Description:    pgtype.Text{String: metadata.Description, Valid: metadata.Description != ""},
		CoverImagePath: pgtype.Text{String: metadata.CoverPath, Valid: metadata.CoverPath != ""},
		Series:         pgtype.Text{String: metadata.Series, Valid: metadata.Series != ""},
		SeriesNumber:   pgtype.Int4{Int32: metadata.SeriesNumber, Valid: metadata.SeriesNumber > 0},
		Tags:           pgtype.Text{String: metadata.Tags, Valid: metadata.Tags != ""},
		Asin:           pgtype.Text{}, // Keep existing ASIN
		DatePublished:  pgtype.Date{Time: metadata.PublishDate, Valid: !metadata.PublishDate.IsZero()},
		Publisher:      pgtype.Text{String: metadata.Publisher, Valid: metadata.Publisher != ""},
		Contributors:   pgtype.Text{String: metadata.Contributors, Valid: metadata.Contributors != ""},
	})

	return err
}

func (s *EbookScanner) getEbookByFilePath(ctx context.Context, filePath string) (database.Ebooks, error) {
	return s.db.GetEbookByFilePath(ctx, filePath)
}

func (s *EbookScanner) getMimeType(path string) string {
	ext := strings.ToLower(filepath.Ext(path))
	switch ext {
	case ".epub":
		return "application/epub+zip"
	case ".pdf":
		return "application/pdf"
	case ".mobi":
		return "application/x-mobipocket-ebook"
	case ".azw3":
		return "application/vnd.amazon.ebook"
	case ".fb2":
		return "application/x-fictionbook+xml"
	case ".txt":
		return "text/plain"
	default:
		return "application/octet-stream"
	}
}

func (s *EbookScanner) WatchChanges(ctx context.Context) {
	go func() {
		for {
			select {
			case event, ok := <-s.watcher.Events:
				if !ok {
					return
				}

				// Handle new directories - add them to the watcher
				if event.Has(fsnotify.Create) {
					info, err := os.Stat(event.Name)
					if err == nil && info.IsDir() {
						// Add the new directory to the watcher
						if err := s.watcher.Add(event.Name); err != nil {
							fmt.Printf("Warning: failed to watch new directory %s: %v\n", event.Name, err)
						} else {
							fmt.Printf("Now watching new directory: %s\n", event.Name)
						}
					}
				}

				// Handle file modifications and creations
				if (event.Has(fsnotify.Create) || event.Has(fsnotify.Write)) && s.isEbookFile(event.Name) {
					fmt.Printf("New/modified ebook detected: %s\n", event.Name)
					if err := s.processEbookFile(ctx, event.Name); err != nil {
						fmt.Printf("Error processing modified ebook %s: %v\n", event.Name, err)
					}
				}

			case err, ok := <-s.watcher.Errors:
				if !ok {
					return
				}
				fmt.Printf("Watcher error: %v\n", err)
			case <-ctx.Done():
				return
			}
		}
	}()
}

func (s *EbookScanner) Close() error {
	if s.watcher != nil {
		return s.watcher.Close()
	}
	return nil
}