alanyeung-s3/aws/internal/storage/filesystem.go

package storage

import (
	"io"
	"os"
	"path/filepath"
)

// Storage defines the interface for object storage operations
type Storage interface {
	// Bucket operations
	CreateBucket(name string) error
	DeleteBucket(name string) error
	BucketExists(name string) (bool, error)
	ListBuckets() ([]BucketInfo, error)

	// Object operations
	PutObject(bucket, key string, reader io.Reader) error
	GetObject(bucket, key string) (io.ReadCloser, *ObjectInfo, error)
	DeleteObject(bucket, key string) error
	ObjectExists(bucket, key string) (bool, error)
	GetObjectInfo(bucket, key string) (*ObjectInfo, error)
	ListObjects(bucket string) ([]ObjectInfo, error)
}

// FileSystemStorage implements Storage using the local file system
type FileSystemStorage struct {
	baseDir string
}

// NewFileSystemStorage creates a new file system storage instance
func NewFileSystemStorage(baseDir string) (*FileSystemStorage, error) {
	if err := os.MkdirAll(baseDir, 0755); err != nil {
		return nil, err
	}

	return &FileSystemStorage{
		baseDir: baseDir,
	}, nil
}

// CreateBucket creates a new bucket directory
func (fs *FileSystemStorage) CreateBucket(name string) error {
	bucketPath := filepath.Join(fs.baseDir, name)

	// Check if bucket already exists
	if _, err := os.Stat(bucketPath); err == nil {
		return ErrBucketAlreadyExists
	}

	return os.MkdirAll(bucketPath, 0755)
}

// DeleteBucket removes a bucket directory
func (fs *FileSystemStorage) DeleteBucket(name string) error {
	bucketPath := filepath.Join(fs.baseDir, name)
	return os.RemoveAll(bucketPath)
}

// BucketExists checks if a bucket exists
func (fs *FileSystemStorage) BucketExists(name string) (bool, error) {
	bucketPath := filepath.Join(fs.baseDir, name)
	_, err := os.Stat(bucketPath)
	if os.IsNotExist(err) {
		return false, nil
	}
	if err != nil {
		return false, err
	}
	return true, nil
}

// ListBuckets lists all buckets
func (fs *FileSystemStorage) ListBuckets() ([]BucketInfo, error) {
	entries, err := os.ReadDir(fs.baseDir)
	if err != nil {
		return nil, err
	}

	var buckets []BucketInfo
	for _, entry := range entries {
		if entry.IsDir() {
			info, err := entry.Info()
			if err != nil {
				continue
			}
			buckets = append(buckets, BucketInfo{
				Name:         entry.Name(),
				CreationDate: info.ModTime(),
			})
		}
	}

	return buckets, nil
}

// PutObject stores an object
func (fs *FileSystemStorage) PutObject(bucket, key string, reader io.Reader) error {
	bucketPath := filepath.Join(fs.baseDir, bucket)

	// Check if bucket exists
	if _, err := os.Stat(bucketPath); os.IsNotExist(err) {
		return ErrBucketNotFound
	}

	objectPath := filepath.Join(bucketPath, key)

	// Create parent directories if needed
	objectDir := filepath.Dir(objectPath)
	if err := os.MkdirAll(objectDir, 0755); err != nil {
		return err
	}

	// Create the file
	file, err := os.Create(objectPath)
	if err != nil {
		return err
	}
	defer file.Close()

	// Copy data to file
	_, err = io.Copy(file, reader)
	return err
}

// GetObject retrieves an object
func (fs *FileSystemStorage) GetObject(bucket, key string) (io.ReadCloser, *ObjectInfo, error) {
	objectPath := filepath.Join(fs.baseDir, bucket, key)

	fileInfo, err := os.Stat(objectPath)
	if os.IsNotExist(err) {
		return nil, nil, ErrObjectNotFound
	}
	if err != nil {
		return nil, nil, err
	}

	file, err := os.Open(objectPath)
	if err != nil {
		return nil, nil, err
	}

	info := &ObjectInfo{
		Key:          key,
		Size:         fileInfo.Size(),
		LastModified: fileInfo.ModTime(),
		ETag:         generateETag(fileInfo),
	}

	return file, info, nil
}

// DeleteObject removes an object
func (fs *FileSystemStorage) DeleteObject(bucket, key string) error {
	objectPath := filepath.Join(fs.baseDir, bucket, key)
	err := os.Remove(objectPath)
	if os.IsNotExist(err) {
		return nil // S3 returns success even if object doesn't exist
	}
	return err
}

// ObjectExists checks if an object exists
func (fs *FileSystemStorage) ObjectExists(bucket, key string) (bool, error) {
	objectPath := filepath.Join(fs.baseDir, bucket, key)
	_, err := os.Stat(objectPath)
	if os.IsNotExist(err) {
		return false, nil
	}
	if err != nil {
		return false, err
	}
	return true, nil
}

// GetObjectInfo retrieves object metadata
func (fs *FileSystemStorage) GetObjectInfo(bucket, key string) (*ObjectInfo, error) {
	objectPath := filepath.Join(fs.baseDir, bucket, key)

	fileInfo, err := os.Stat(objectPath)
	if os.IsNotExist(err) {
		return nil, ErrObjectNotFound
	}
	if err != nil {
		return nil, err
	}

	return &ObjectInfo{
		Key:          key,
		Size:         fileInfo.Size(),
		LastModified: fileInfo.ModTime(),
		ETag:         generateETag(fileInfo),
	}, nil
}

// ListObjects lists all objects in a bucket
func (fs *FileSystemStorage) ListObjects(bucket string) ([]ObjectInfo, error) {
	bucketPath := filepath.Join(fs.baseDir, bucket)

	if _, err := os.Stat(bucketPath); os.IsNotExist(err) {
		return nil, ErrBucketNotFound
	}

	entries, err := os.ReadDir(bucketPath)
	if err != nil {
		return nil, err
	}

	var objects []ObjectInfo
	for _, entry := range entries {
		if !entry.IsDir() {
			info, err := entry.Info()
			if err != nil {
				continue
			}
			objects = append(objects, ObjectInfo{
				Key:          entry.Name(),
				Size:         info.Size(),
				LastModified: info.ModTime(),
				ETag:         generateETag(info),
			})
		}
	}

	return objects, nil
}