package themes_service

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"sync"

	"autolibrary.top/webserver/backend/models/themes_model"
	"autolibrary.top/webserver/backend/services/theme_files"

	"gorm.io/gorm"
)

// Service coordinates database changes and their corresponding theme archive.
type Service struct {
	DB    *gorm.DB
	Files *theme_files.Store
	locks sync.Map
}

func (s *Service) lock(id uint) func() {
	value, _ := s.locks.LoadOrStore(id, &sync.Mutex{})
	mutex := value.(*sync.Mutex)
	mutex.Lock()
	return mutex.Unlock
}

func (s *Service) ArchivePath(id uint) string {
	return filepath.Join(s.Files.Root(), fmt.Sprintf("%d.altheme", id))
}

func (s *Service) Create(theme *themes_model.Theme, qss []byte) error {
	var path string
	err := s.DB.Transaction(func(tx *gorm.DB) error {
		if err := tx.Create(theme).Error; err != nil {
			return err
		}
		path = s.ArchivePath(theme.ID)
		data, err := theme_files.CreateAlthemeArchive(qss, theme_files.BuildInfoJSON(*theme))
		if err != nil {
			return err
		}
		if err := s.Files.WriteFile(path, data, 0644); err != nil {
			return err
		}
		theme.FilePath = path
		theme.FileSize = fmt.Sprintf("%.1f KB", float64(len(data))/1024)
		return tx.Save(theme).Error
	})
	if err != nil && path != "" {
		_ = s.Files.Remove(path)
	}
	return err
}

func (s *Service) Save(theme *themes_model.Theme, qss []byte) error {
	unlock := s.lock(theme.ID)
	defer unlock()
	path := s.ArchivePath(theme.ID)
	previous, readErr := os.ReadFile(path)
	if qss == nil {
		var err error
		qss, err = theme_files.ExtractQSSFromAltheme(path)
		if err != nil {
			return fmt.Errorf("cannot read existing theme archive: %w", err)
		}
	}
	data, err := theme_files.CreateAlthemeArchive(qss, theme_files.BuildInfoJSON(*theme))
	if err != nil {
		return err
	}
	theme.FilePath = path
	theme.FileSize = fmt.Sprintf("%.1f KB", float64(len(data))/1024)
	wrote := false
	err = s.DB.Transaction(func(tx *gorm.DB) error {
		if err := tx.Save(theme).Error; err != nil {
			return err
		}
		if err := s.Files.WriteFile(path, data, 0644); err != nil {
			return err
		}
		wrote = true
		return nil
	})
	if err != nil && wrote {
		var restoreErr error
		if readErr == nil {
			restoreErr = s.Files.WriteFile(path, previous, 0644)
		} else {
			restoreErr = s.Files.Remove(path)
		}
		if restoreErr != nil {
			log.Printf("[E] archive rollback failed for theme %d: %v", theme.ID, restoreErr)
		}
	}
	return err
}

func (s *Service) Delete(theme *themes_model.Theme) error {
	unlock := s.lock(theme.ID)
	defer unlock()
	if err := s.DB.Delete(theme).Error; err != nil {
		return err
	}
	paths := []string{s.ArchivePath(theme.ID)}
	if theme.PreviewURL != "" {
		paths = append(paths, filepath.Join(s.Files.Root(), "previews", filepath.Base(theme.PreviewURL)))
	}
	for _, path := range paths {
		if err := s.Files.Remove(path); err != nil {
			log.Printf("[W] theme %d file cleanup: %v", theme.ID, err)
		}
	}
	return nil
}