package backup

import (
	"archive/tar"
	"compress/gzip"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"

	"gitea.avt.data-center.id/othman.suseno/atlas/internal/models"
)

// Service handles configuration backup and restore operations
type Service struct {
	backupDir string
}

// BackupMetadata contains information about a backup
type BackupMetadata struct {
	ID          string    `json:"id"`
	CreatedAt   time.Time `json:"created_at"`
	Version     string    `json:"version"`
	Description string    `json:"description,omitempty"`
	Size        int64     `json:"size"`
	Checksum    string    `json:"checksum,omitempty"`
}

// BackupData contains all configuration data to be backed up
type BackupData struct {
	Metadata     BackupMetadata          `json:"metadata"`
	Users        []models.User           `json:"users,omitempty"`
	SMBShares    []models.SMBShare       `json:"smb_shares,omitempty"`
	NFSExports   []models.NFSExport      `json:"nfs_exports,omitempty"`
	ISCSITargets []models.ISCSITarget    `json:"iscsi_targets,omitempty"`
	Policies     []models.SnapshotPolicy `json:"policies,omitempty"`
	Config       map[string]interface{}  `json:"config,omitempty"`
}

// New creates a new backup service
func New(backupDir string) (*Service, error) {
	if err := os.MkdirAll(backupDir, 0755); err != nil {
		return nil, fmt.Errorf("create backup directory: %w", err)
	}

	return &Service{
		backupDir: backupDir,
	}, nil
}

// CreateBackup creates a backup of all system configurations
func (s *Service) CreateBackup(data BackupData, description string) (string, error) {
	// Generate backup ID
	backupID := fmt.Sprintf("backup-%d", time.Now().Unix())
	backupPath := filepath.Join(s.backupDir, backupID+".tar.gz")

	// Set metadata
	data.Metadata.ID = backupID
	data.Metadata.CreatedAt = time.Now()
	data.Metadata.Version = "1.0"
	data.Metadata.Description = description

	// Create backup file
	file, err := os.Create(backupPath)
	if err != nil {
		return "", fmt.Errorf("create backup file: %w", err)
	}
	defer file.Close()

	// Create gzip writer
	gzWriter := gzip.NewWriter(file)
	defer gzWriter.Close()

	// Create tar writer
	tarWriter := tar.NewWriter(gzWriter)
	defer tarWriter.Close()

	// Write metadata
	metadataJSON, err := json.MarshalIndent(data.Metadata, "", "  ")
	if err != nil {
		return "", fmt.Errorf("marshal metadata: %w", err)
	}

	if err := s.writeFileToTar(tarWriter, "metadata.json", metadataJSON); err != nil {
		return "", fmt.Errorf("write metadata: %w", err)
	}

	// Write configuration data
	configJSON, err := json.MarshalIndent(data, "", "  ")
	if err != nil {
		return "", fmt.Errorf("marshal config: %w", err)
	}

	if err := s.writeFileToTar(tarWriter, "config.json", configJSON); err != nil {
		return "", fmt.Errorf("write config: %w", err)
	}

	// Get file size
	stat, err := file.Stat()
	if err != nil {
		return "", fmt.Errorf("get file stat: %w", err)
	}

	data.Metadata.Size = stat.Size()

	// Update metadata with size
	metadataJSON, err = json.MarshalIndent(data.Metadata, "", "  ")
	if err != nil {
		return "", fmt.Errorf("marshal updated metadata: %w", err)
	}

	// Note: We can't update the tar file, so we'll store metadata separately
	metadataPath := filepath.Join(s.backupDir, backupID+".meta.json")
	if err := os.WriteFile(metadataPath, metadataJSON, 0644); err != nil {
		return "", fmt.Errorf("write metadata file: %w", err)
	}

	return backupID, nil
}

// writeFileToTar writes a file to a tar archive
func (s *Service) writeFileToTar(tw *tar.Writer, filename string, data []byte) error {
	header := &tar.Header{
		Name:    filename,
		Size:    int64(len(data)),
		Mode:    0644,
		ModTime: time.Now(),
	}

	if err := tw.WriteHeader(header); err != nil {
		return err
	}

	if _, err := tw.Write(data); err != nil {
		return err
	}

	return nil
}

// ListBackups returns a list of all available backups
func (s *Service) ListBackups() ([]BackupMetadata, error) {
	files, err := os.ReadDir(s.backupDir)
	if err != nil {
		return nil, fmt.Errorf("read backup directory: %w", err)
	}

	var backups []BackupMetadata
	for _, file := range files {
		if file.IsDir() {
			continue
		}

		if filepath.Ext(file.Name()) != ".json" || !strings.HasSuffix(file.Name(), ".meta.json") {
			continue
		}

		metadataPath := filepath.Join(s.backupDir, file.Name())
		data, err := os.ReadFile(metadataPath)
		if err != nil {
			continue // Skip corrupted metadata files
		}

		var metadata BackupMetadata
		if err := json.Unmarshal(data, &metadata); err != nil {
			continue // Skip invalid metadata files
		}

		// Get actual backup file size if it exists
		backupPath := filepath.Join(s.backupDir, metadata.ID+".tar.gz")
		if stat, err := os.Stat(backupPath); err == nil {
			metadata.Size = stat.Size()
		}

		backups = append(backups, metadata)
	}

	return backups, nil
}

// GetBackup returns metadata for a specific backup
func (s *Service) GetBackup(backupID string) (*BackupMetadata, error) {
	metadataPath := filepath.Join(s.backupDir, backupID+".meta.json")
	data, err := os.ReadFile(metadataPath)
	if err != nil {
		return nil, fmt.Errorf("read metadata: %w", err)
	}

	var metadata BackupMetadata
	if err := json.Unmarshal(data, &metadata); err != nil {
		return nil, fmt.Errorf("unmarshal metadata: %w", err)
	}

	// Get actual backup file size
	backupPath := filepath.Join(s.backupDir, backupID+".tar.gz")
	if stat, err := os.Stat(backupPath); err == nil {
		metadata.Size = stat.Size()
	}

	return &metadata, nil
}

// RestoreBackup restores configuration from a backup
func (s *Service) RestoreBackup(backupID string) (*BackupData, error) {
	backupPath := filepath.Join(s.backupDir, backupID+".tar.gz")

	file, err := os.Open(backupPath)
	if err != nil {
		return nil, fmt.Errorf("open backup file: %w", err)
	}
	defer file.Close()

	// Create gzip reader
	gzReader, err := gzip.NewReader(file)
	if err != nil {
		return nil, fmt.Errorf("create gzip reader: %w", err)
	}
	defer gzReader.Close()

	// Create tar reader
	tarReader := tar.NewReader(gzReader)

	var configData []byte
	var metadataData []byte

	// Extract files from tar
	for {
		header, err := tarReader.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, fmt.Errorf("read tar: %w", err)
		}

		switch header.Name {
		case "config.json":
			configData, err = io.ReadAll(tarReader)
			if err != nil {
				return nil, fmt.Errorf("read config: %w", err)
			}
		case "metadata.json":
			metadataData, err = io.ReadAll(tarReader)
			if err != nil {
				return nil, fmt.Errorf("read metadata: %w", err)
			}
		}
	}

	if configData == nil {
		return nil, fmt.Errorf("config.json not found in backup")
	}

	var backupData BackupData
	if err := json.Unmarshal(configData, &backupData); err != nil {
		return nil, fmt.Errorf("unmarshal config: %w", err)
	}

	// Update metadata if available
	if metadataData != nil {
		if err := json.Unmarshal(metadataData, &backupData.Metadata); err == nil {
			// Metadata loaded successfully
		}
	}

	return &backupData, nil
}

// DeleteBackup deletes a backup file and its metadata
func (s *Service) DeleteBackup(backupID string) error {
	backupPath := filepath.Join(s.backupDir, backupID+".tar.gz")
	metadataPath := filepath.Join(s.backupDir, backupID+".meta.json")

	var errors []error

	if err := os.Remove(backupPath); err != nil && !os.IsNotExist(err) {
		errors = append(errors, fmt.Errorf("remove backup file: %w", err))
	}

	if err := os.Remove(metadataPath); err != nil && !os.IsNotExist(err) {
		errors = append(errors, fmt.Errorf("remove metadata file: %w", err))
	}

	if len(errors) > 0 {
		return fmt.Errorf("delete backup: %v", errors)
	}

	return nil
}

// VerifyBackup verifies that a backup file is valid and can be restored
func (s *Service) VerifyBackup(backupID string) error {
	backupPath := filepath.Join(s.backupDir, backupID+".tar.gz")

	file, err := os.Open(backupPath)
	if err != nil {
		return fmt.Errorf("open backup file: %w", err)
	}
	defer file.Close()

	// Try to read the backup
	gzReader, err := gzip.NewReader(file)
	if err != nil {
		return fmt.Errorf("invalid gzip format: %w", err)
	}
	defer gzReader.Close()

	tarReader := tar.NewReader(gzReader)

	hasConfig := false

	for {
		header, err := tarReader.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			return fmt.Errorf("invalid tar format: %w", err)
		}

		switch header.Name {
		case "config.json":
			hasConfig = true
			// Try to read and parse config
			data, err := io.ReadAll(tarReader)
			if err != nil {
				return fmt.Errorf("read config: %w", err)
			}
			var backupData BackupData
			if err := json.Unmarshal(data, &backupData); err != nil {
				return fmt.Errorf("invalid config format: %w", err)
			}
		case "metadata.json":
			// Metadata is optional, just verify it can be read
			_, err := io.ReadAll(tarReader)
			if err != nil {
				return fmt.Errorf("read metadata: %w", err)
			}
		}
	}

	if !hasConfig {
		return fmt.Errorf("backup missing config.json")
	}

	return nil
}