package services

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"path/filepath"
	"strings"
	"time"

	"github.com/google/uuid"
	"go.uber.org/zap"
	"gorm.io/gorm"

	"veza-backend-api/internal/models"
)

var (
	ErrFolderNotEmpty = fmt.Errorf("folder is not empty")
)

const MaxCloudFileSize = 500 * 1024 * 1024 // 500MB

var AllowedMimeTypes = []string{
	"audio/mpeg", "audio/mp3", "audio/wav", "audio/x-wav",
	"audio/flac", "audio/x-flac", "audio/ogg", "audio/aac",
	"audio/mp4", "audio/x-m4a", "audio/midi", "audio/x-midi",
	"audio/aiff", "audio/x-aiff",
	"application/zip", "application/x-zip-compressed",
	"application/octet-stream",
}

type CloudService struct {
	db        *gorm.DB
	logger    *zap.Logger
	s3Service *S3StorageService
}

func NewCloudService(db *gorm.DB, logger *zap.Logger, s3Service *S3StorageService) *CloudService {
	return &CloudService{
		db:        db,
		logger:    logger,
		s3Service: s3Service,
	}
}

func (s *CloudService) ListFolders(ctx context.Context, userID uuid.UUID, parentID *uuid.UUID) ([]models.UserFolder, error) {
	var folders []models.UserFolder
	query := s.db.WithContext(ctx).Where("user_id = ?", userID)
	if parentID != nil {
		query = query.Where("parent_id = ?", *parentID)
	} else {
		query = query.Where("parent_id IS NULL")
	}
	if err := query.Order("name ASC").Find(&folders).Error; err != nil {
		return nil, fmt.Errorf("failed to list folders: %w", err)
	}
	return folders, nil
}

func (s *CloudService) CreateFolder(ctx context.Context, userID uuid.UUID, name string, parentID *uuid.UUID) (*models.UserFolder, error) {
	if parentID != nil {
		if err := s.verifyFolderOwnership(ctx, userID, *parentID); err != nil {
			return nil, err
		}
	}

	folder := &models.UserFolder{
		ID:       uuid.New(),
		UserID:   userID,
		Name:     name,
		ParentID: parentID,
	}

	if err := s.db.WithContext(ctx).Create(folder).Error; err != nil {
		return nil, fmt.Errorf("failed to create folder: %w", err)
	}

	return folder, nil
}

func (s *CloudService) RenameFolder(ctx context.Context, userID uuid.UUID, folderID uuid.UUID, newName string) error {
	if err := s.verifyFolderOwnership(ctx, userID, folderID); err != nil {
		return err
	}

	result := s.db.WithContext(ctx).Model(&models.UserFolder{}).
		Where("id = ? AND user_id = ?", folderID, userID).
		Update("name", newName)
	if result.Error != nil {
		return fmt.Errorf("failed to rename folder: %w", result.Error)
	}
	return nil
}

func (s *CloudService) DeleteFolder(ctx context.Context, userID uuid.UUID, folderID uuid.UUID) error {
	if err := s.verifyFolderOwnership(ctx, userID, folderID); err != nil {
		return err
	}

	return s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var files []models.UserFile
		if err := tx.Where("folder_id = ? AND user_id = ?", folderID, userID).Find(&files).Error; err != nil {
			return err
		}

		var totalSize int64
		for _, f := range files {
			if s.s3Service != nil {
				_ = s.s3Service.DeleteFile(ctx, f.S3Key)
			}
			totalSize += f.SizeBytes
		}

		if err := tx.Where("folder_id = ? AND user_id = ?", folderID, userID).Delete(&models.UserFile{}).Error; err != nil {
			return err
		}

		var childFolders []models.UserFolder
		if err := tx.Where("parent_id = ? AND user_id = ?", folderID, userID).Find(&childFolders).Error; err != nil {
			return err
		}
		for _, child := range childFolders {
			if err := s.deleteFolderRecursive(ctx, tx, userID, child.ID, &totalSize); err != nil {
				return err
			}
		}

		if err := tx.Where("id = ? AND user_id = ?", folderID, userID).Delete(&models.UserFolder{}).Error; err != nil {
			return err
		}

		if totalSize > 0 {
			if err := tx.Model(&models.StorageQuota{}).
				Where("user_id = ?", userID).
				Update("used_bytes", gorm.Expr("CASE WHEN used_bytes - ? > 0 THEN used_bytes - ? ELSE 0 END", totalSize, totalSize)).Error; err != nil {
				return err
			}
		}

		return nil
	})
}

func (s *CloudService) deleteFolderRecursive(ctx context.Context, tx *gorm.DB, userID uuid.UUID, folderID uuid.UUID, totalSize *int64) error {
	var files []models.UserFile
	if err := tx.Where("folder_id = ? AND user_id = ?", folderID, userID).Find(&files).Error; err != nil {
		return err
	}
	for _, f := range files {
		if s.s3Service != nil {
			_ = s.s3Service.DeleteFile(ctx, f.S3Key)
		}
		*totalSize += f.SizeBytes
	}
	if err := tx.Where("folder_id = ? AND user_id = ?", folderID, userID).Delete(&models.UserFile{}).Error; err != nil {
		return err
	}

	var children []models.UserFolder
	if err := tx.Where("parent_id = ? AND user_id = ?", folderID, userID).Find(&children).Error; err != nil {
		return err
	}
	for _, child := range children {
		if err := s.deleteFolderRecursive(ctx, tx, userID, child.ID, totalSize); err != nil {
			return err
		}
	}

	return tx.Where("id = ? AND user_id = ?", folderID, userID).Delete(&models.UserFolder{}).Error
}

func (s *CloudService) ListFiles(ctx context.Context, userID uuid.UUID, folderID *uuid.UUID) ([]models.UserFile, error) {
	var files []models.UserFile
	query := s.db.WithContext(ctx).Where("user_id = ?", userID)
	if folderID != nil {
		query = query.Where("folder_id = ?", *folderID)
	} else {
		query = query.Where("folder_id IS NULL")
	}
	if err := query.Order("created_at DESC").Find(&files).Error; err != nil {
		return nil, fmt.Errorf("failed to list files: %w", err)
	}
	return files, nil
}

func (s *CloudService) UploadFile(ctx context.Context, userID uuid.UUID, folderID *uuid.UUID, filename string, data []byte, mimeType string) (*models.UserFile, error) {
	if !s.isAllowedMimeType(mimeType) {
		return nil, ErrInvalidMimeType
	}

	fileSize := int64(len(data))
	if fileSize > MaxCloudFileSize {
		return nil, ErrFileTooLarge
	}

	if folderID != nil {
		if err := s.verifyFolderOwnership(ctx, userID, *folderID); err != nil {
			return nil, err
		}
	}

	if err := s.checkQuota(ctx, userID, fileSize); err != nil {
		return nil, err
	}

	fileID := uuid.New()
	s3Key := fmt.Sprintf("cloud/%s/%s/%s%s", userID, fileID, sanitizeFilename(filename), filepath.Ext(filename))

	var file *models.UserFile
	err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		result := tx.Model(&models.StorageQuota{}).
			Where("user_id = ? AND used_bytes + ? <= max_bytes", userID, fileSize).
			Update("used_bytes", gorm.Expr("used_bytes + ?", fileSize))
		if result.RowsAffected == 0 {
			return ErrQuotaExceeded
		}
		if result.Error != nil {
			return result.Error
		}

		if s.s3Service != nil {
			if _, err := s.s3Service.UploadFile(ctx, data, s3Key, mimeType); err != nil {
				tx.Model(&models.StorageQuota{}).
					Where("user_id = ?", userID).
					Update("used_bytes", gorm.Expr("CASE WHEN used_bytes - ? > 0 THEN used_bytes - ? ELSE 0 END", fileSize, fileSize))
				return fmt.Errorf("failed to upload to S3: %w", err)
			}
		}

		file = &models.UserFile{
			ID:        fileID,
			UserID:    userID,
			FolderID:  folderID,
			Filename:  filename,
			S3Key:     s3Key,
			SizeBytes: fileSize,
			MimeType:  mimeType,
		}

		if err := tx.Create(file).Error; err != nil {
			if s.s3Service != nil {
				_ = s.s3Service.DeleteFile(ctx, s3Key)
			}
			return fmt.Errorf("failed to create file record: %w", err)
		}

		return nil
	})

	if err != nil {
		return nil, err
	}

	return file, nil
}

func (s *CloudService) DeleteFile(ctx context.Context, userID uuid.UUID, fileID uuid.UUID) error {
	var file models.UserFile
	if err := s.db.WithContext(ctx).Where("id = ? AND user_id = ?", fileID, userID).First(&file).Error; err != nil {
		return ErrFileNotFound
	}

	return s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		if err := tx.Where("id = ? AND user_id = ?", fileID, userID).Delete(&models.UserFile{}).Error; err != nil {
			return err
		}

		if err := tx.Model(&models.StorageQuota{}).
			Where("user_id = ?", userID).
			Update("used_bytes", gorm.Expr("CASE WHEN used_bytes - ? > 0 THEN used_bytes - ? ELSE 0 END", file.SizeBytes, file.SizeBytes)).Error; err != nil {
			return err
		}

		if s.s3Service != nil {
			_ = s.s3Service.DeleteFile(ctx, file.S3Key)
		}

		return nil
	})
}

func (s *CloudService) GetFileByID(ctx context.Context, userID uuid.UUID, fileID uuid.UUID) (*models.UserFile, error) {
	var file models.UserFile
	if err := s.db.WithContext(ctx).Where("id = ? AND user_id = ?", fileID, userID).First(&file).Error; err != nil {
		return nil, ErrFileNotFound
	}
	return &file, nil
}

func (s *CloudService) GetQuota(ctx context.Context, userID uuid.UUID) (*models.StorageQuota, error) {
	quota := models.StorageQuota{
		UserID:    userID,
		MaxBytes:  5 * 1024 * 1024 * 1024, // 5GB default
		UsedBytes: 0,
	}
	if err := s.db.WithContext(ctx).Where("user_id = ?", userID).FirstOrCreate(&quota).Error; err != nil {
		return nil, fmt.Errorf("failed to get or create quota: %w", err)
	}
	return &quota, nil
}

func (s *CloudService) UpdateQuotaUsed(ctx context.Context, userID uuid.UUID, delta int64) error {
	result := s.db.WithContext(ctx).Model(&models.StorageQuota{}).
		Where("user_id = ?", userID).
		Update("used_bytes", gorm.Expr("CASE WHEN used_bytes + ? > 0 THEN used_bytes + ? ELSE 0 END", delta, delta))
	if result.Error != nil {
		return fmt.Errorf("failed to update quota: %w", result.Error)
	}
	return nil
}

func (s *CloudService) InitQuota(ctx context.Context, userID uuid.UUID) error {
	quota := &models.StorageQuota{
		UserID:    userID,
		MaxBytes:  5 * 1024 * 1024 * 1024, // 5GB
		UsedBytes: 0,
	}
	result := s.db.WithContext(ctx).
		Where("user_id = ?", userID).
		FirstOrCreate(quota)
	return result.Error
}

func (s *CloudService) StreamFile(ctx context.Context, userID uuid.UUID, fileID uuid.UUID) ([]byte, *models.UserFile, error) {
	file, err := s.GetFileByID(ctx, userID, fileID)
	if err != nil {
		return nil, nil, err
	}

	if s.s3Service == nil {
		return nil, nil, fmt.Errorf("S3 service not configured")
	}

	data, err := s.s3Service.DownloadFile(ctx, file.S3Key)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to download file: %w", err)
	}

	return data, file, nil
}

func (s *CloudService) verifyFolderOwnership(ctx context.Context, userID uuid.UUID, folderID uuid.UUID) error {
	var count int64
	s.db.WithContext(ctx).Model(&models.UserFolder{}).
		Where("id = ? AND user_id = ?", folderID, userID).
		Count(&count)
	if count == 0 {
		return ErrFolderNotFound
	}
	return nil
}

func (s *CloudService) checkQuota(ctx context.Context, userID uuid.UUID, additionalBytes int64) error {
	var quota models.StorageQuota
	if err := s.db.WithContext(ctx).Where("user_id = ?", userID).First(&quota).Error; err != nil {
		return fmt.Errorf("quota not found: %w", err)
	}
	if quota.UsedBytes+additionalBytes > quota.MaxBytes {
		return ErrQuotaExceeded
	}
	return nil
}

func (s *CloudService) isAllowedMimeType(mimeType string) bool {
	if strings.HasPrefix(mimeType, "audio/") {
		return true
	}
	for _, allowed := range AllowedMimeTypes {
		if mimeType == allowed {
			return true
		}
	}
	return false
}

func sanitizeFilename(name string) string {
	base := filepath.Base(name)
	ext := filepath.Ext(base)
	nameWithoutExt := strings.TrimSuffix(base, ext)
	safe := strings.Map(func(r rune) rune {
		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') || r == '-' || r == '_' {
			return r
		}
		return '_'
	}, nameWithoutExt)
	if safe == "" {
		safe = "file"
	}
	return safe
}

const maxVersionsPerFile = 10

// CreateVersion saves the current file state as a new version (copies S3 object to preserve it)
func (s *CloudService) CreateVersion(ctx context.Context, userID uuid.UUID, fileID uuid.UUID) (*models.CloudFileVersion, error) {
	file, err := s.GetFileByID(ctx, userID, fileID)
	if err != nil {
		return nil, err
	}

	var count int64
	var nextVersion int
	if err := s.db.WithContext(ctx).Model(&models.CloudFileVersion{}).Where("file_id = ?", fileID).Count(&count).Error; err != nil {
		return nil, fmt.Errorf("failed to count versions: %w", err)
	}
	if count >= maxVersionsPerFile {
		var oldest models.CloudFileVersion
		if err := s.db.WithContext(ctx).Where("file_id = ?", fileID).Order("version ASC").First(&oldest).Error; err == nil {
			if s.s3Service != nil {
				_ = s.s3Service.DeleteFile(ctx, oldest.StorageKey)
			}
			_ = s.db.WithContext(ctx).Delete(&oldest).Error
		}
	}
	if err := s.db.WithContext(ctx).Model(&models.CloudFileVersion{}).Where("file_id = ?", fileID).Select("COALESCE(MAX(version), 0)").Scan(&nextVersion).Error; err != nil {
		return nil, fmt.Errorf("failed to get max version: %w", err)
	}
	nextVersion++

	versionKey := fmt.Sprintf("cloud/%s/versions/%s/v%d", userID, fileID, nextVersion)
	if s.s3Service != nil {
		data, err := s.s3Service.DownloadFile(ctx, file.S3Key)
		if err != nil {
			return nil, fmt.Errorf("failed to copy file for version: %w", err)
		}
		if _, err := s.s3Service.UploadFile(ctx, data, versionKey, file.MimeType); err != nil {
			return nil, fmt.Errorf("failed to save version copy: %w", err)
		}
	} else {
		versionKey = file.S3Key
	}

	version := &models.CloudFileVersion{
		FileID:     fileID,
		Version:    nextVersion,
		StorageKey: versionKey,
		SizeBytes:  file.SizeBytes,
	}
	if err := s.db.WithContext(ctx).Create(version).Error; err != nil {
		if s.s3Service != nil {
			_ = s.s3Service.DeleteFile(ctx, versionKey)
		}
		return nil, fmt.Errorf("failed to create version: %w", err)
	}
	return version, nil
}

// ListVersions returns versions for a file, sorted by version DESC
func (s *CloudService) ListVersions(ctx context.Context, userID uuid.UUID, fileID uuid.UUID) ([]models.CloudFileVersion, error) {
	if _, err := s.GetFileByID(ctx, userID, fileID); err != nil {
		return nil, err
	}

	var versions []models.CloudFileVersion
	if err := s.db.WithContext(ctx).Where("file_id = ?", fileID).Order("version DESC").Limit(maxVersionsPerFile).Find(&versions).Error; err != nil {
		return nil, fmt.Errorf("failed to list versions: %w", err)
	}
	return versions, nil
}

// RestoreVersion swaps the file's s3_key with the selected version
func (s *CloudService) RestoreVersion(ctx context.Context, userID uuid.UUID, fileID uuid.UUID, version int) error {
	if _, err := s.GetFileByID(ctx, userID, fileID); err != nil {
		return err
	}

	var v models.CloudFileVersion
	if err := s.db.WithContext(ctx).Where("file_id = ? AND version = ?", fileID, version).First(&v).Error; err != nil {
		return fmt.Errorf("version not found: %w", err)
	}

	if err := s.db.WithContext(ctx).Model(&models.UserFile{}).Where("id = ? AND user_id = ?", fileID, userID).
		Updates(map[string]interface{}{
			"s3_key":     v.StorageKey,
			"size_bytes": v.SizeBytes,
		}).Error; err != nil {
		return fmt.Errorf("failed to restore: %w", err)
	}
	return nil
}

// ShareFile creates a share link with token
func (s *CloudService) ShareFile(ctx context.Context, userID uuid.UUID, fileID uuid.UUID, permissions string, expiresInHours int) (*models.CloudFileShare, error) {
	if _, err := s.GetFileByID(ctx, userID, fileID); err != nil {
		return nil, err
	}

	tokenBytes := make([]byte, 32)
	if _, err := rand.Read(tokenBytes); err != nil {
		return nil, fmt.Errorf("failed to generate token: %w", err)
	}
	token := hex.EncodeToString(tokenBytes)

	expiresAt := time.Now().Add(time.Duration(expiresInHours) * time.Hour)
	share := &models.CloudFileShare{
		FileID:      fileID,
		Token:       token,
		Permissions: permissions,
		ExpiresAt:   expiresAt,
	}
	if err := s.db.WithContext(ctx).Create(share).Error; err != nil {
		return nil, fmt.Errorf("failed to create share: %w", err)
	}
	return share, nil
}

// GetSharedFile returns file metadata if token is valid and not expired
func (s *CloudService) GetSharedFile(ctx context.Context, token string) (*models.UserFile, error) {
	var share models.CloudFileShare
	if err := s.db.WithContext(ctx).Where("token = ? AND expires_at > ?", token, time.Now()).First(&share).Error; err != nil {
		return nil, ErrShareExpired
	}

	var file models.UserFile
	if err := s.db.WithContext(ctx).Where("id = ?", share.FileID).First(&file).Error; err != nil {
		return nil, ErrFileNotFound
	}
	return &file, nil
}