feat: add local file system storage provider (#224)

Signed-off-by: sh1luo <690898835@qq.com>

storage/local_file_system.go

@@ -0,0 +1,129 @@
+// Copyright 2021 The casbin Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package storage
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/qor/oss"
+)
+
+var baseFolder = "files"
+
+// FileSystem file system storage
+type FileSystem struct {
+	Base string
+}
+
+// NewFileSystem initialize the local file system storage
+func NewFileSystem(base string) *FileSystem {
+	absBase, err := filepath.Abs(base)
+	if err != nil {
+		panic("local file system storage's base folder is not initialized")
+	}
+
+	return &FileSystem{Base: absBase}
+}
+
+// GetFullPath get full path from absolute/relative path
+func (fileSystem FileSystem) GetFullPath(path string) string {
+	fullPath := path
+	if !strings.HasPrefix(path, fileSystem.Base) {
+		fullPath, _ = filepath.Abs(filepath.Join(fileSystem.Base, path))
+	}
+	return fullPath
+}
+
+// Get receive file with given path
+func (fileSystem FileSystem) Get(path string) (*os.File, error) {
+	return os.Open(fileSystem.GetFullPath(path))
+}
+
+// GetStream get file as stream
+func (fileSystem FileSystem) GetStream(path string) (io.ReadCloser, error) {
+	return os.Open(fileSystem.GetFullPath(path))
+}
+
+// Put store a reader into given path
+func (fileSystem FileSystem) Put(path string, reader io.Reader) (*oss.Object, error) {
+	var (
+		fullPath = fileSystem.GetFullPath(path)
+		err      = os.MkdirAll(filepath.Dir(fullPath), os.ModePerm)
+	)
+
+	if err != nil {
+		return nil, err
+	}
+
+	dst, err := os.Create(fullPath)
+
+	if err == nil {
+		if seeker, ok := reader.(io.ReadSeeker); ok {
+			seeker.Seek(0, 0)
+		}
+		_, err = io.Copy(dst, reader)
+	}
+
+	return &oss.Object{Path: path, Name: filepath.Base(path), StorageInterface: fileSystem}, err
+}
+
+// Delete delete file
+func (fileSystem FileSystem) Delete(path string) error {
+	return os.Remove(fileSystem.GetFullPath(path))
+}
+
+// List list all objects under current path
+func (fileSystem FileSystem) List(path string) ([]*oss.Object, error) {
+	var (
+		objects  []*oss.Object
+		fullPath = fileSystem.GetFullPath(path)
+	)
+
+	filepath.Walk(fullPath, func(path string, info os.FileInfo, err error) error {
+		if path == fullPath {
+			return nil
+		}
+
+		if err == nil && !info.IsDir() {
+			modTime := info.ModTime()
+			objects = append(objects, &oss.Object{
+				Path:             strings.TrimPrefix(path, fileSystem.Base),
+				Name:             info.Name(),
+				LastModified:     &modTime,
+				StorageInterface: fileSystem,
+			})
+		}
+		return nil
+	})
+
+	return objects, nil
+}
+
+// GetEndpoint get endpoint, FileSystem's endpoint is /
+func (fileSystem FileSystem) GetEndpoint() string {
+	return "/"
+}
+
+// GetURL get public accessible URL
+func (fileSystem FileSystem) GetURL(path string) (url string, err error) {
+	return path, nil
+}
+
+func NewLocalFileSystemStorageProvider(clientId string, clientSecret string, region string, bucket string, endpoint string) oss.StorageInterface {
+	return NewFileSystem(baseFolder)
+}