/*
 * Mini Object Storage, (C) 2015 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 singledisk

import (
	"bytes"
	"errors"
	"github.com/minio-io/minio/pkg/encoding/erasure"
	"github.com/minio-io/minio/pkg/storage"
	"github.com/minio-io/minio/pkg/storage/donut/erasure/erasure1"
	"github.com/minio-io/minio/pkg/storage/donut/object/objectv1"
	"github.com/minio-io/minio/pkg/utils/split"
	"io"
	"os"
	"path"
)

// StorageDriver creates a new single disk storage driver using donut without encoding.
type StorageDriver struct {
	root     string
	donutBox DonutBox
}

// DonutBox is an interface specifying how the storage driver should interact with its underlying system.
type DonutBox interface {
	Store(objectv1.ObjectMetadata, erasure1.DataHeader, io.Reader)
}

// Start a single disk subsystem
func Start(root string, donutBox DonutBox) (chan<- string, <-chan error, storage.Storage) {
	ctrlChannel := make(chan string)
	errorChannel := make(chan error)
	s := new(StorageDriver)
	s.root = root
	s.donutBox = donutBox
	go start(ctrlChannel, errorChannel, s)
	return ctrlChannel, errorChannel, s
}

func start(ctrlChannel <-chan string, errorChannel chan<- error, s *StorageDriver) {
	err := os.MkdirAll(s.root, 0700)
	errorChannel <- err
	close(errorChannel)
}

// ListBuckets returns a list of buckets
func (diskStorage StorageDriver) ListBuckets() ([]storage.BucketMetadata, error) {
	return nil, errors.New("Not Implemented")
}

// CreateBucket creates a new bucket
func (diskStorage StorageDriver) CreateBucket(bucket string) error {
	bucketPath := path.Join(diskStorage.root, bucket)
	return os.MkdirAll(bucketPath, 0600)
}

// CreateBucketPolicy sets a bucket's access policy
func (diskStorage StorageDriver) CreateBucketPolicy(bucket string, p storage.BucketPolicy) error {
	return errors.New("Not Implemented")
}

// GetBucketPolicy returns a bucket's access policy
func (diskStorage StorageDriver) GetBucketPolicy(bucket string) (storage.BucketPolicy, error) {
	return storage.BucketPolicy{}, errors.New("Not Implemented")
}

// GetObject retrieves an object and writes it to a writer
func (diskStorage StorageDriver) GetObject(w io.Writer, bucket, object string) (int64, error) {
	return 0, errors.New("Not Implemented")
}

// GetPartialObject retrieves an object and writes it to a writer
func (diskStorage StorageDriver) GetPartialObject(w io.Writer, bucket, object string, start, length int64) (int64, error) {
	return 0, errors.New("Not Implemented")
}

// GetObjectMetadata retrieves an object's metadata
func (diskStorage StorageDriver) GetObjectMetadata(bucket, object string, prefix string) (storage.ObjectMetadata, error) {
	return storage.ObjectMetadata{}, errors.New("Not Implemented")
}

// ListObjects lists objects
func (diskStorage StorageDriver) ListObjects(bucket string, resources storage.BucketResourcesMetadata) ([]storage.ObjectMetadata, storage.BucketResourcesMetadata, error) {
	return nil, storage.BucketResourcesMetadata{}, errors.New("Not Implemented")
}

// CreateObject creates a new object
func (diskStorage StorageDriver) CreateObject(bucket string, key string, contentType string, data io.Reader) error {
	// test if object exists
	// split object into erasure parts
	erasureParts := split.Stream(data, 10*1024*1024)
	// set up encoder
	params, err := erasure.ParseEncoderParams(8, 8, erasure.Cauchy)
	if err != nil {
		return err
	}
	encoder := erasure.NewEncoder(params)
	// for each erasure part
	erasurePartIndex := 1
	for erasurePart := range erasureParts {
		if erasurePart.Err != nil {
			return erasurePart.Err
		}
		// encode each erasure part into encoded parts
		encodedParts, length := encoder.Encode(erasurePart.Data)
		// for each encoded part
		for encodedPartIndex, encodedPart := range encodedParts {
			objectMetadata := objectv1.ObjectMetadata{
				Bucket:      bucket,
				Key:         key,
				ErasurePart: uint16(erasurePartIndex),
				EncodedPart: uint8(encodedPartIndex),
				ContentType: contentType,
			}
			erasureMetadata := erasure1.DataHeader{
				OriginalLength:   uint32(length),
				EncoderK:         8,
				EncoderM:         8,
				EncoderTechnique: erasure1.Cauchy,
			}
			// store encoded part
			diskStorage.donutBox.Store(objectMetadata, erasureMetadata, bytes.NewBuffer(encodedPart))
			erasurePartIndex = erasurePartIndex + 1
		}
	}
	return errors.New("Not Implemented")
}