/*
 * MinIO Cloud Storage, (C) 2016 MinIO, Inc.
 *
 * 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 cmd

import (
	"io"
)

// StorageAPI interface.
type StorageAPI interface {
	// Stringified version of disk.
	String() string

	// Storage operations.
	IsOnline() bool // Returns true if disk is online.
	LastError() error
	Close() error

	DiskInfo() (info DiskInfo, err error)

	// Volume operations.
	MakeVol(volume string) (err error)
	ListVols() (vols []VolInfo, err error)
	StatVol(volume string) (vol VolInfo, err error)
	DeleteVol(volume string) (err error)

	// File operations.
	ListDir(volume, dirPath string, count int, leafFile string) ([]string, error)
	ReadFile(volume string, path string, offset int64, buf []byte, verifier *BitrotVerifier) (n int64, err error)
	AppendFile(volume string, path string, buf []byte) (err error)
	CreateFile(volume, path string, size int64, reader io.Reader) error
	ReadFileStream(volume, path string, offset, length int64) (io.ReadCloser, error)
	RenameFile(srcVolume, srcPath, dstVolume, dstPath string) error
	StatFile(volume string, path string) (file FileInfo, err error)
	DeleteFile(volume string, path string) (err error)

	// Write all data, syncs the data to disk.
	WriteAll(volume string, path string, buf []byte) (err error)

	// Read all.
	ReadAll(volume string, path string) (buf []byte, err error)
}

// storageReader is an io.Reader view of a disk
type storageReader struct {
	storage      StorageAPI
	volume, path string
	offset       int64
}

func (r *storageReader) Read(p []byte) (n int, err error) {
	nn, err := r.storage.ReadFile(r.volume, r.path, r.offset, p, nil)
	r.offset += nn
	n = int(nn)

	if err == io.ErrUnexpectedEOF && nn > 0 {
		err = io.EOF
	}
	return
}

// storageWriter is a io.Writer view of a disk.
type storageWriter struct {
	storage      StorageAPI
	volume, path string
}

func (w *storageWriter) Write(p []byte) (n int, err error) {
	err = w.storage.AppendFile(w.volume, w.path, p)
	if err == nil {
		n = len(p)
	}
	return
}

// StorageWriter returns a new io.Writer which appends data to the file
// at the given disk, volume and path.
func StorageWriter(storage StorageAPI, volume, path string) io.Writer {
	return &storageWriter{storage, volume, path}
}

// StorageReader returns a new io.Reader which reads data to the file
// at the given disk, volume, path and offset.
func StorageReader(storage StorageAPI, volume, path string, offset int64) io.Reader {
	return &storageReader{storage, volume, path, offset}
}