package agate

import (
	"context"
	"errors"
	"fmt"
	"gitea.unprism.ru/KRBL/Agate/archive"
	"gitea.unprism.ru/KRBL/Agate/grpc"
	"gitea.unprism.ru/KRBL/Agate/interfaces"
	"io"
	"log"
	"os"
	"path/filepath"
	"sync"

	"gitea.unprism.ru/KRBL/Agate/store"
	"gitea.unprism.ru/KRBL/Agate/stores"
)

// AgateOptions defines configuration options for the Agate library.
type AgateOptions struct {
	// WorkDir is the directory where snapshots will be stored and managed.
	WorkDir string

	// OpenFunc is called after a snapshot is restored to initialize resources.
	// The parameter is the directory where the snapshot was extracted.
	OpenFunc func(dir string) error

	// CloseFunc is called before a snapshot is created or restored to clean up resources.
	CloseFunc func() error

	// MetadataStore is the implementation of the metadata store to use.
	// If nil, a default SQLite-based metadata store will be created automatically.
	// Use the stores package to initialize a custom implementation:
	//   metadataStore, err := stores.NewDefaultMetadataStore(metadataDir)
	MetadataStore store.MetadataStore

	// BlobStore is the implementation of the blob store to use.
	// If nil, a default filesystem-based blob store will be created automatically.
	// Use the stores package to initialize a custom implementation:
	//   blobStore, err := stores.NewDefaultBlobStore(blobsDir)
	BlobStore store.BlobStore

	// CleanOnRestore specifies whether the target directory should be cleaned before restoring a snapshot.
	CleanOnRestore bool

	// Logger is the logger to use for output. If nil, logging is disabled.
	Logger *log.Logger
}

// Agate is the main entry point for the snapshot library.
type Agate struct {
	mutex             sync.Mutex
	manager           interfaces.SnapshotManager
	options           AgateOptions
	metadataDir       string
	blobsDir          string
	currentSnapshotID string
	currentIDFile     string
}

// New initializes a new instance of the Agate library with the given options.
func New(options AgateOptions) (*Agate, error) {
	if options.WorkDir == "" {
		return nil, errors.New("work directory cannot be empty")
	}

	// Initialize logger if not provided
	if options.Logger == nil {
		options.Logger = log.New(io.Discard, "", 0)
	}

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

	// Create subdirectories for metadata and blobs
	metadataDir := filepath.Join(options.WorkDir, "metadata")
	blobsDir := filepath.Join(options.WorkDir, "blobs")

	if err := os.MkdirAll(metadataDir, 0755); err != nil {
		return nil, fmt.Errorf("failed to create metadata directory: %w", err)
	}

	if err := os.MkdirAll(blobsDir, 0755); err != nil {
		return nil, fmt.Errorf("failed to create blobs directory: %w", err)
	}

	var metadataStore store.MetadataStore
	var blobStore store.BlobStore
	var err error

	// Use provided stores or initialize default ones
	if options.MetadataStore != nil && options.BlobStore != nil {
		// Use the provided stores
		metadataStore = options.MetadataStore
		blobStore = options.BlobStore
	} else if options.MetadataStore == nil && options.BlobStore == nil {
		// Initialize both stores with default implementations
		metadataStore, blobStore, err = stores.InitDefaultStores(options.WorkDir)
		if err != nil {
			return nil, fmt.Errorf("failed to initialize default stores: %w", err)
		}
		// Update options with the created stores
		options.MetadataStore = metadataStore
		options.BlobStore = blobStore
	} else if options.MetadataStore == nil {
		// Initialize only the metadata store
		metadataStore, err = stores.NewDefaultMetadataStore(metadataDir)
		if err != nil {
			return nil, fmt.Errorf("failed to initialize default metadata store: %w", err)
		}
		blobStore = options.BlobStore
		// Update options with the created metadata store
		options.MetadataStore = metadataStore
	} else {
		// Initialize only the blob store
		blobStore, err = stores.NewDefaultBlobStore(blobsDir)
		if err != nil {
			return nil, fmt.Errorf("failed to initialize default blob store: %w", err)
		}
		metadataStore = options.MetadataStore
		// Update options with the created blob store
		options.BlobStore = blobStore
	}

	// Create the snapshot manager
	manager, err := CreateSnapshotManager(metadataStore, blobStore, options.Logger)
	if err != nil {
		return nil, fmt.Errorf("failed to create snapshot manager: %w", err)
	}

	// Create a file path for storing the current snapshot ID
	currentIDFile := filepath.Join(options.WorkDir, "current_snapshot_id")

	agate := &Agate{
		manager:       manager,
		options:       options,
		metadataDir:   metadataDir,
		blobsDir:      blobsDir,
		currentIDFile: currentIDFile,
	}

	// Load the current snapshot ID if it exists
	if _, err := os.Stat(currentIDFile); err == nil {
		data, err := os.ReadFile(currentIDFile)
		if err == nil && len(data) > 0 {
			agate.currentSnapshotID = string(data)
		}
	}

	// Call OpenFunc if provided to initialize resources in the active directory
	if options.OpenFunc != nil {
		if err := options.OpenFunc(blobStore.GetActiveDir()); err != nil {
			return nil, fmt.Errorf("failed to open resources during initialization: %w", err)
		}
	}

	return agate, nil
}

func (a *Agate) GetActiveDir() string {
	return a.options.BlobStore.GetActiveDir()
}

func (a *Agate) GetMetadataDir() string {
	return a.metadataDir
}

func (a *Agate) GetBlobsDir() string {
	return a.blobsDir
}

// SaveSnapshot creates a new snapshot from the current state of the active directory.
// If parentID is provided, it will be set as the parent of the new snapshot.
// If parentID is empty, it will use the ID of the snapshot currently loaded in the active directory.
// Returns the ID of the created snapshot.
func (a *Agate) SaveSnapshot(ctx context.Context, name string, parentID string) (string, error) {
	a.mutex.Lock()
	defer a.mutex.Unlock()

	a.options.Logger.Printf("Creating new snapshot with name: %s", name)

	// Call CloseFunc if provided
	if a.options.CloseFunc != nil {
		if err := a.options.CloseFunc(); err != nil {
			return "", fmt.Errorf("failed to close resources before snapshot: %w", err)
		}
	}

	defer func() {
		if a.options.OpenFunc != nil {
			if err := a.options.OpenFunc(a.options.BlobStore.GetActiveDir()); err != nil {
				a.options.Logger.Printf("ERROR: failed to open resources after snapshot creation: %v", err)
			}
		}
	}()

	// If parentID is not provided, use the current snapshot ID
	if parentID == "" {
		parentID = a.currentSnapshotID
	}

	effectiveParentID := parentID

	// Create the snapshot
	snapshot, err := a.manager.CreateSnapshot(ctx, a.options.BlobStore.GetActiveDir(), name, effectiveParentID)
	if err != nil {
		a.options.Logger.Printf("ERROR: failed to create snapshot: %v", err)
		return "", fmt.Errorf("failed to create snapshot: %w", err)
	}

	a.options.Logger.Printf("Successfully created snapshot with ID: %s", snapshot.ID)

	// Update the current snapshot ID to the newly created snapshot
	a.currentSnapshotID = snapshot.ID

	// Save the current snapshot ID to a file
	if err := a.saveCurrentSnapshotID(); err != nil {
		return "", fmt.Errorf("failed to save current snapshot ID: %w", err)
	}

	return snapshot.ID, nil
}

// RestoreSnapshot extracts a snapshot to the active directory.
func (a *Agate) RestoreSnapshot(ctx context.Context, snapshotID string) error {
	a.mutex.Lock()
	defer a.mutex.Unlock()

	a.options.Logger.Printf("Restoring snapshot with ID: %s", snapshotID)

	// Call CloseFunc if provided
	if a.options.CloseFunc != nil {
		if err := a.options.CloseFunc(); err != nil {
			return fmt.Errorf("failed to close resources before restore: %w", err)
		}
	}

	// Extract the snapshot
	if err := a.manager.ExtractSnapshot(ctx, snapshotID, a.options.BlobStore.GetActiveDir(), a.options.CleanOnRestore); err != nil {
		a.options.Logger.Printf("ERROR: failed to extract snapshot: %v", err)
		return fmt.Errorf("failed to extract snapshot: %w", err)
	}

	a.options.Logger.Printf("Successfully restored snapshot with ID: %s", snapshotID)

	// Save the ID of the snapshot that was restored
	a.currentSnapshotID = snapshotID

	// Save the current snapshot ID to a file
	if err := a.saveCurrentSnapshotID(); err != nil {
		return fmt.Errorf("failed to save current snapshot ID: %w", err)
	}

	// Call OpenFunc if provided
	if a.options.OpenFunc != nil {
		if err := a.options.OpenFunc(a.options.BlobStore.GetActiveDir()); err != nil {
			a.options.Logger.Printf("ERROR: failed to open resources after restore: %v", err)
			return fmt.Errorf("failed to open resources after restore: %w", err)
		}
	}

	return nil
}

// RestoreSnapshot extracts a snapshot to the directory.
func (a *Agate) RestoreSnapshotToDir(ctx context.Context, snapshotID string, dir string) error {
	a.mutex.Lock()
	defer a.mutex.Unlock()

	// Call CloseFunc if provided
	if a.options.CloseFunc != nil {
		if err := a.options.CloseFunc(); err != nil {
			return fmt.Errorf("failed to close resources before restore: %w", err)
		}
	}

	defer func() {
		if a.options.OpenFunc != nil {
			if err := a.options.OpenFunc(dir); err != nil {
				a.options.Logger.Printf("ERROR: failed to open resources after snapshot restore: %v", err)
			}
		}
	}()

	// Extract the snapshot
	if err := a.manager.ExtractSnapshot(ctx, snapshotID, dir, a.options.CleanOnRestore); err != nil {
		return fmt.Errorf("failed to extract snapshot: %w", err)
	}

	// If restoring to the active directory, save the snapshot ID
	if dir == a.options.BlobStore.GetActiveDir() {
		a.currentSnapshotID = snapshotID

		// Save the current snapshot ID to a file
		if err := a.saveCurrentSnapshotID(); err != nil {
			return fmt.Errorf("failed to save current snapshot ID: %w", err)
		}
	}

	return nil
}

// ListSnapshots returns a list of all available snapshots.
func (a *Agate) ListSnapshots(ctx context.Context) ([]store.SnapshotInfo, error) {
	// Create empty ListOptions since we don't have filtering/pagination in this API yet
	opts := store.ListOptions{}
	return a.manager.ListSnapshots(ctx, opts)
}

// GetSnapshotDetails returns detailed information about a specific snapshot.
func (a *Agate) GetSnapshotDetails(ctx context.Context, snapshotID string) (*store.Snapshot, error) {
	return a.manager.GetSnapshotDetails(ctx, snapshotID)
}

// DeleteSnapshot removes a snapshot.
func (a *Agate) DeleteSnapshot(ctx context.Context, snapshotID string) error {
	return a.manager.DeleteSnapshot(ctx, snapshotID)
}

// saveCurrentSnapshotID saves the current snapshot ID to a file in the WorkDir
func (a *Agate) saveCurrentSnapshotID() error {
	if a.currentSnapshotID == "" {
		// If there's no current snapshot ID, remove the file if it exists
		if _, err := os.Stat(a.currentIDFile); err == nil {
			return os.Remove(a.currentIDFile)
		}
		return nil
	}

	// Write the current snapshot ID to the file
	return os.WriteFile(a.currentIDFile, []byte(a.currentSnapshotID), 0644)
}

func (a *Agate) Open() error {
	return a.options.OpenFunc(a.GetActiveDir())
}

// Close releases all resources used by the Agate instance.
func (a *Agate) Close() error {
	if a.options.CloseFunc != nil {
		return a.options.CloseFunc()
	}
	return nil
}

// StartServer starts a gRPC server to share snapshots.
func (a *Agate) StartServer(ctx context.Context, address string) error {
	_, err := grpc.RunServer(ctx, a.manager, address)
	if err != nil {
		return fmt.Errorf("failed to start server: %w", err)
	}

	// We don't store the server reference because we don't have a way to stop it yet
	// In a future version, we could add a StopServer method

	return nil
}

// ConnectRemote connects to a remote snapshot server.
// Returns a client that can be used to interact with the remote server.
func (a *Agate) ConnectRemote(address string) (*grpc.SnapshotClient, error) {
	client, err := grpc.ConnectToServer(address)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to remote server: %w", err)
	}

	return client, nil
}

// GetRemoteSnapshotList retrieves a list of snapshots from a remote server.
func (a *Agate) GetRemoteSnapshotList(ctx context.Context, address string) ([]store.SnapshotInfo, error) {
	client, err := a.ConnectRemote(address)
	if err != nil {
		return nil, err
	}
	defer client.Close()

	return client.ListSnapshots(ctx)
}

// GetRemoteSnapshot downloads a snapshot from a remote server.
// If localParentID is provided, it will be used to optimize the download by skipping files that already exist locally.
func (a *Agate) GetRemoteSnapshot(ctx context.Context, address string, snapshotID string, localParentID string) error {
	client, err := a.ConnectRemote(address)
	if err != nil {
		return err
	}
	defer client.Close()

	// Get the remote snapshot details
	remoteSnapshot, err := client.FetchSnapshotDetails(ctx, snapshotID)
	if err != nil {
		return fmt.Errorf("failed to get snapshot details: %w", err)
	}

	// Create a temporary directory for downloading files
	tempDownloadDir := filepath.Join(a.options.WorkDir, "temp_download", snapshotID)
	if err := os.MkdirAll(tempDownloadDir, 0755); err != nil {
		return fmt.Errorf("failed to create temporary download directory: %w", err)
	}
	defer os.RemoveAll(tempDownloadDir) // Clean up when done

	a.options.Logger.Printf("Downloading snapshot %s from %s", snapshotID, address)

	// If localParentID is provided, try to reuse files from the local parent snapshot
	if localParentID != "" {
		a.options.Logger.Printf("Using local parent snapshot %s for incremental download", localParentID)

		// Get the local parent snapshot details
		localParent, err := a.GetSnapshotDetails(ctx, localParentID)
		if err != nil {
			a.options.Logger.Printf("Warning: Failed to get local parent snapshot details: %v", err)
		} else {
			// Extract the local parent snapshot to a temporary directory
			localParentDir := filepath.Join(a.options.WorkDir, "temp_download", localParentID)
			if err := os.MkdirAll(localParentDir, 0755); err != nil {
				a.options.Logger.Printf("Warning: Failed to create temporary directory for local parent: %v", err)
			} else {
				defer os.RemoveAll(localParentDir) // Clean up when done

				if err := a.manager.ExtractSnapshot(ctx, localParentID, localParentDir, true); err != nil {
					a.options.Logger.Printf("Warning: Failed to extract local parent snapshot: %v", err)
				} else {
					// Copy unchanged files from the local parent to the download directory
					for _, file := range remoteSnapshot.Files {
						// Skip directories, they'll be created as needed
						if file.IsDir {
							continue
						}

						// Check if the file exists in the local parent with the same hash
						var localFile *store.FileInfo
						for _, lf := range localParent.Files {
							if lf.Path == file.Path && lf.SHA256 == file.SHA256 {
								localFile = &lf
								break
							}
						}

						if localFile != nil {
							// File exists in local parent with the same hash, copy it
							srcPath := filepath.Join(localParentDir, localFile.Path)
							dstPath := filepath.Join(tempDownloadDir, file.Path)

							// Ensure the destination directory exists
							if err := os.MkdirAll(filepath.Dir(dstPath), 0755); err != nil {
								a.options.Logger.Printf("Failed to create directory for %s: %v", dstPath, err)
								continue
							}

							// Copy the file
							srcFile, err := os.Open(srcPath)
							if err != nil {
								a.options.Logger.Printf("Failed to copy file %s, will download instead: %v", file.Path, err)
								continue
							}
							defer srcFile.Close()

							dstFile, err := os.Create(dstPath)
							if err != nil {
								a.options.Logger.Printf("Failed to create destination file %s: %v", dstPath, err)
								continue
							}

							_, err = io.Copy(dstFile, srcFile)
							dstFile.Close()

							if err != nil {
								a.options.Logger.Printf("Failed to copy file data for %s: %v", file.Path, err)
								// If copy fails, the file will be downloaded
							} else {
								a.options.Logger.Printf("Reusing file %s from local parent", file.Path)
							}
						}
					}
				}
			}
		}
	}

	// Download the snapshot files
	a.options.Logger.Printf("Downloading files for snapshot %s", snapshotID)

	// Get snapshot details to know what files we need to download
	remoteDetails, err := client.FetchSnapshotDetails(ctx, snapshotID)
	if err != nil {
		return fmt.Errorf("failed to get remote snapshot details: %w", err)
	}

	// Check which files we already have and which we need to download
	for _, file := range remoteDetails.Files {
		if file.IsDir {
			continue // Skip directories
		}

		filePath := filepath.Join(tempDownloadDir, file.Path)
		if _, err := os.Stat(filePath); os.IsNotExist(err) {
			// File doesn't exist yet, we'll need to download it
			a.options.Logger.Printf("Downloading file %s", file.Path)
		}
	}

	if err := client.DownloadSnapshot(ctx, snapshotID, tempDownloadDir, localParentID); err != nil {
		return fmt.Errorf("failed to download snapshot: %w", err)
	}

	a.options.Logger.Printf("Creating archive from downloaded files")

	// Create a zip archive from the downloaded files
	zipPath := filepath.Join(a.options.WorkDir, "temp_download", snapshotID+".zip")
	if err := archive.CreateArchive(tempDownloadDir, zipPath); err != nil {
		return fmt.Errorf("failed to create zip archive: %w", err)
	}

	// Store the blob with the remote snapshot ID
	zipFile, err := os.Open(zipPath)
	if err != nil {
		return fmt.Errorf("failed to open zip file: %w", err)
	}
	defer zipFile.Close()
	defer os.Remove(zipPath) // Clean up the zip file when done

	a.options.Logger.Printf("Storing blob with ID %s", remoteSnapshot.ID)

	// Store the blob with the remote snapshot ID
	_, err = a.options.BlobStore.StoreBlob(ctx, remoteSnapshot.ID, zipFile)
	if err != nil {
		return fmt.Errorf("failed to store blob: %w", err)
	}

	a.options.Logger.Printf("Saving snapshot metadata")

	// Save the remote snapshot metadata
	err = a.options.MetadataStore.SaveSnapshotMetadata(ctx, *remoteSnapshot)
	if err != nil {
		return fmt.Errorf("failed to save snapshot metadata: %w", err)
	}

	a.options.Logger.Printf("Successfully imported remote snapshot %s", snapshotID)
	return nil
}