/*
 * Minio Cloud Storage, (C) 2017 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 (
	"context"
	"crypto/sha1"
	"fmt"
	"hash"
	"io"
	"io/ioutil"
	"net/http"
	"strings"
	"sync"
	"time"

	b2 "github.com/minio/blazer/base"
	"github.com/minio/minio-go/pkg/policy"
)

// Supported bucket types by B2 backend.
const (
	bucketTypePrivate  = "allPrivate"
	bucketTypeReadOnly = "allPublic"
)

// b2Object implements gateway for Minio and BackBlaze B2 compatible object storage servers.
type b2Objects struct {
	gatewayUnsupported
	mu         sync.Mutex
	creds      credential
	b2Client   *b2.B2
	anonClient *http.Client
	ctx        context.Context
}

// newB2Gateway returns b2 gateway layer, implements GatewayLayer interface to
// talk to B2 remote backend.
func newB2Gateway() (GatewayLayer, error) {
	ctx := context.Background()
	creds := serverConfig.GetCredential()

	client, err := b2.AuthorizeAccount(ctx, creds.AccessKey, creds.SecretKey, b2.Transport(newCustomHTTPTransport()))
	if err != nil {
		return nil, err
	}

	return &b2Objects{
		creds:    creds,
		b2Client: client,
		anonClient: &http.Client{
			Transport: newCustomHTTPTransport(),
		},
		ctx: ctx,
	}, nil
}

// Convert B2 errors to minio object layer errors.
func b2ToObjectError(err error, params ...string) error {
	if err == nil {
		return nil
	}

	e, ok := err.(*Error)
	if !ok {
		// Code should be fixed if this function is called without doing traceError()
		// Else handling different situations in this function makes this function complicated.
		errorIf(err, "Expected type *Error")
		return err
	}

	err = e.e
	bucket := ""
	object := ""
	uploadID := ""
	if len(params) >= 1 {
		bucket = params[0]
	}
	if len(params) == 2 {
		object = params[1]
	}
	if len(params) == 3 {
		uploadID = params[2]
	}

	// Following code is a non-exhaustive check to convert
	// B2 errors into S3 compatible errors.
	//
	// For a more complete information - https://www.backblaze.com/b2/docs/
	statusCode, code, msg := b2.Code(err)
	if statusCode == 0 {
		// We don't interpret non B2 errors. B2 errors have statusCode
		// to help us convert them to S3 object errors.
		return e
	}

	switch code {
	case "duplicate_bucket_name":
		err = BucketAlreadyOwnedByYou{Bucket: bucket}
	case "bad_request":
		if object != "" {
			err = ObjectNameInvalid{bucket, object}
		} else if bucket != "" {
			err = BucketNotFound{Bucket: bucket}
		}
	case "bad_bucket_id":
		err = BucketNotFound{Bucket: bucket}
	case "file_not_present", "not_found":
		err = ObjectNotFound{bucket, object}
	case "cannot_delete_non_empty_bucket":
		err = BucketNotEmpty{bucket, ""}
	}

	// Special interpretation like this is required for Multipart sessions.
	if strings.Contains(msg, "No active upload for") && uploadID != "" {
		err = InvalidUploadID{uploadID}
	}

	e.e = err
	return e
}

// Shutdown saves any gateway metadata to disk
// if necessary and reload upon next restart.
func (l *b2Objects) Shutdown() error {
	// TODO
	return nil
}

// StorageInfo is not relevant to B2 backend.
func (l *b2Objects) StorageInfo() (si StorageInfo) {
	return si
}

// MakeBucket creates a new container on B2 backend.
func (l *b2Objects) MakeBucketWithLocation(bucket, location string) error {
	// location is ignored for B2 backend.

	// All buckets are set to private by default.
	_, err := l.b2Client.CreateBucket(l.ctx, bucket, bucketTypePrivate, nil, nil)
	return b2ToObjectError(traceError(err), bucket)
}

func (l *b2Objects) reAuthorizeAccount() error {
	client, err := b2.AuthorizeAccount(l.ctx, l.creds.AccessKey, l.creds.SecretKey, b2.Transport(newCustomHTTPTransport()))
	if err != nil {
		return err
	}
	l.mu.Lock()
	l.b2Client.Update(client)
	l.mu.Unlock()
	return nil
}

// listBuckets is a wrapper similar to ListBuckets, which re-authorizes
// the account and updates the B2 client safely. Once successfully
// authorized performs the call again and returns list of buckets.
// For any errors which are not actionable we return an error.
func (l *b2Objects) listBuckets(err error) ([]*b2.Bucket, error) {
	if err != nil {
		if b2.Action(err) != b2.ReAuthenticate {
			return nil, err
		}
		if rerr := l.reAuthorizeAccount(); rerr != nil {
			return nil, rerr
		}
	}
	bktList, lerr := l.b2Client.ListBuckets(l.ctx)
	if lerr != nil {
		return l.listBuckets(lerr)
	}
	return bktList, nil
}

// Bucket - is a helper which provides a *Bucket instance
// for performing an API operation. B2 API doesn't
// provide a direct way to access the bucket so we need
// to employ following technique.
func (l *b2Objects) Bucket(bucket string) (*b2.Bucket, error) {
	bktList, err := l.listBuckets(nil)
	if err != nil {
		return nil, b2ToObjectError(traceError(err), bucket)
	}
	for _, bkt := range bktList {
		if bkt.Name == bucket {
			return bkt, nil
		}
	}
	return nil, traceError(BucketNotFound{Bucket: bucket})
}

// GetBucketInfo gets bucket metadata..
func (l *b2Objects) GetBucketInfo(bucket string) (bi BucketInfo, err error) {
	if _, err = l.Bucket(bucket); err != nil {
		return bi, err
	}
	return BucketInfo{
		Name:    bucket,
		Created: time.Unix(0, 0),
	}, nil
}

// ListBuckets lists all B2 buckets
func (l *b2Objects) ListBuckets() ([]BucketInfo, error) {
	bktList, err := l.listBuckets(nil)
	if err != nil {
		return nil, err
	}
	var bktInfo []BucketInfo
	for _, bkt := range bktList {
		bktInfo = append(bktInfo, BucketInfo{
			Name:    bkt.Name,
			Created: time.Unix(0, 0),
		})
	}
	return bktInfo, nil
}

// DeleteBucket deletes a bucket on B2
func (l *b2Objects) DeleteBucket(bucket string) error {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return err
	}
	err = bkt.DeleteBucket(l.ctx)
	return b2ToObjectError(traceError(err), bucket)
}

// ListObjects lists all objects in B2 bucket filtered by prefix, returns upto at max 1000 entries at a time.
func (l *b2Objects) ListObjects(bucket string, prefix string, marker string, delimiter string, maxKeys int) (loi ListObjectsInfo, err error) {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return loi, err
	}
	loi = ListObjectsInfo{}
	files, next, lerr := bkt.ListFileNames(l.ctx, maxKeys, marker, prefix, delimiter)
	if lerr != nil {
		return loi, b2ToObjectError(traceError(lerr), bucket)
	}
	loi.IsTruncated = next != ""
	loi.NextMarker = next
	for _, file := range files {
		switch file.Status {
		case "folder":
			loi.Prefixes = append(loi.Prefixes, file.Name)
		case "upload":
			loi.Objects = append(loi.Objects, ObjectInfo{
				Bucket:      bucket,
				Name:        file.Name,
				ModTime:     file.Timestamp,
				Size:        file.Size,
				ETag:        file.Info.ID,
				ContentType: file.Info.ContentType,
				UserDefined: file.Info.Info,
			})
		}
	}
	return loi, nil
}

// ListObjectsV2 lists all objects in B2 bucket filtered by prefix, returns upto max 1000 entries at a time.
func (l *b2Objects) ListObjectsV2(bucket, prefix, continuationToken, delimiter string, maxKeys int,
	fetchOwner bool, startAfter string) (loi ListObjectsV2Info, err error) {
	// fetchOwner, startAfter are not supported and unused.
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return loi, err
	}
	loi = ListObjectsV2Info{}
	files, next, lerr := bkt.ListFileNames(l.ctx, maxKeys, continuationToken, prefix, delimiter)
	if lerr != nil {
		return loi, b2ToObjectError(traceError(lerr), bucket)
	}
	loi.IsTruncated = next != ""
	loi.ContinuationToken = continuationToken
	loi.NextContinuationToken = next
	for _, file := range files {
		switch file.Status {
		case "folder":
			loi.Prefixes = append(loi.Prefixes, file.Name)
		case "upload":
			loi.Objects = append(loi.Objects, ObjectInfo{
				Bucket:      bucket,
				Name:        file.Name,
				ModTime:     file.Timestamp,
				Size:        file.Size,
				ETag:        file.Info.ID,
				ContentType: file.Info.ContentType,
				UserDefined: file.Info.Info,
			})
		}
	}
	return loi, nil
}

// GetObject reads an object from B2. Supports additional
// parameters like offset and length which are synonymous with
// HTTP Range requests.
//
// startOffset indicates the starting read location of the object.
// length indicates the total length of the object.
func (l *b2Objects) GetObject(bucket string, object string, startOffset int64, length int64, writer io.Writer) error {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return err
	}
	reader, err := bkt.DownloadFileByName(l.ctx, object, startOffset, length)
	if err != nil {
		return b2ToObjectError(traceError(err), bucket, object)
	}
	defer reader.Close()
	_, err = io.Copy(writer, reader)
	return b2ToObjectError(traceError(err), bucket, object)
}

// GetObjectInfo reads object info and replies back ObjectInfo
func (l *b2Objects) GetObjectInfo(bucket string, object string) (objInfo ObjectInfo, err error) {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return objInfo, err
	}
	f, err := bkt.DownloadFileByName(l.ctx, object, 0, 1)
	if err != nil {
		return objInfo, b2ToObjectError(traceError(err), bucket, object)
	}
	f.Close()
	fi, err := bkt.File(f.ID, object).GetFileInfo(l.ctx)
	if err != nil {
		return objInfo, b2ToObjectError(traceError(err), bucket, object)
	}
	objInfo = ObjectInfo{
		Bucket:      bucket,
		Name:        object,
		ETag:        fi.ID,
		Size:        fi.Size,
		ModTime:     fi.Timestamp,
		ContentType: fi.ContentType,
		UserDefined: fi.Info,
	}
	return objInfo, nil
}

// In B2 - You must always include the X-Bz-Content-Sha1 header with
// your upload request. The value you provide can be:
// (1) the 40-character hex checksum of the file,
// (2) the string hex_digits_at_end, or
// (3) the string do_not_verify.
// For more reference - https://www.backblaze.com/b2/docs/uploading.html
//
const (
	sha1NoVerify = "do_not_verify"
	sha1AtEOF    = "hex_digits_at_end"
)

// With the second option mentioned above, you append the 40-character hex sha1
// to the end of the request body, immediately after the contents of the file
// being uploaded. Note that the content length is the size of the file plus 40
// of the original size of the reader.
//
// newB2Reader implements a B2 compatible reader by wrapping the HashReader into
// a new io.Reader which will emit out the sha1 hex digits at io.EOF.
// It also means that your overall content size is now original size + 40 bytes.
// Additionally this reader also verifies Hash encapsulated inside HashReader
// at io.EOF if the verification failed we return an error and do not send
// the content to server.
func newB2Reader(r *HashReader, size int64) *B2Reader {
	return &B2Reader{
		r:        r,
		size:     size,
		sha1Hash: sha1.New(),
	}
}

// B2Reader - is a Reader wraps the HashReader which will emit out the sha1
// hex digits at io.EOF. It also means that your overall content size is
// now original size + 40 bytes. Additionally this reader also verifies
// Hash encapsulated inside HashReader at io.EOF if the verification
// failed we return an error and do not send the content to server.
type B2Reader struct {
	r        *HashReader
	size     int64
	sha1Hash hash.Hash

	isEOF bool
	buf   *strings.Reader
}

// Size - Returns the total size of Reader.
func (nb *B2Reader) Size() int64 { return nb.size + 40 }
func (nb *B2Reader) Read(p []byte) (int, error) {
	if nb.isEOF {
		return nb.buf.Read(p)
	}
	// Read into hash to update the on going checksum.
	n, err := io.TeeReader(nb.r, nb.sha1Hash).Read(p)
	if err == io.EOF {
		// Verify checksum at io.EOF
		if err = nb.r.Verify(); err != nil {
			return n, err
		}
		// Stream is not corrupted on this end
		// now fill in the last 40 bytes of sha1 hex
		// so that the server can verify the stream on
		// their end.
		err = nil
		nb.isEOF = true
		nb.buf = strings.NewReader(fmt.Sprintf("%x", nb.sha1Hash.Sum(nil)))
	}
	return n, err
}

// PutObject uploads the single upload to B2 backend by using *b2_upload_file* API, uploads upto 5GiB.
func (l *b2Objects) PutObject(bucket string, object string, data *HashReader, metadata map[string]string) (ObjectInfo, error) {
	var objInfo ObjectInfo
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return objInfo, err
	}
	contentType := metadata["content-type"]
	delete(metadata, "content-type")
	delete(metadata, "etag")

	var u *b2.URL
	u, err = bkt.GetUploadURL(l.ctx)
	if err != nil {
		return objInfo, b2ToObjectError(traceError(err), bucket, object)
	}

	hr := newB2Reader(data, data.Size())
	var f *b2.File
	f, err = u.UploadFile(l.ctx, hr, int(hr.Size()), object, contentType, sha1AtEOF, metadata)
	if err != nil {
		return objInfo, b2ToObjectError(traceError(err), bucket, object)
	}

	var fi *b2.FileInfo
	fi, err = f.GetFileInfo(l.ctx)
	if err != nil {
		return objInfo, b2ToObjectError(traceError(err), bucket, object)
	}

	return ObjectInfo{
		Bucket:      bucket,
		Name:        object,
		ETag:        fi.ID,
		Size:        fi.Size,
		ModTime:     fi.Timestamp,
		ContentType: fi.ContentType,
		UserDefined: fi.Info,
	}, nil
}

// CopyObject copies a blob from source container to destination container.
func (l *b2Objects) CopyObject(srcBucket string, srcObject string, dstBucket string,
	dstObject string, metadata map[string]string) (objInfo ObjectInfo, err error) {
	return objInfo, traceError(NotImplemented{})
}

// DeleteObject deletes a blob in bucket
func (l *b2Objects) DeleteObject(bucket string, object string) error {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return err
	}
	reader, err := bkt.DownloadFileByName(l.ctx, object, 0, 1)
	if err != nil {
		return b2ToObjectError(traceError(err), bucket, object)
	}
	io.Copy(ioutil.Discard, reader)
	reader.Close()
	err = bkt.File(reader.ID, object).DeleteFileVersion(l.ctx)
	return b2ToObjectError(traceError(err), bucket, object)
}

// ListMultipartUploads lists all multipart uploads.
func (l *b2Objects) ListMultipartUploads(bucket string, prefix string, keyMarker string, uploadIDMarker string,
	delimiter string, maxUploads int) (lmi ListMultipartsInfo, err error) {
	// keyMarker, prefix, delimiter are all ignored, Backblaze B2 doesn't support any
	// of these parameters only equivalent parameter is uploadIDMarker.
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return lmi, err
	}
	// The maximum number of files to return from this call.
	// The default value is 100, and the maximum allowed is 100.
	if maxUploads > 100 {
		maxUploads = 100
	}
	largeFiles, nextMarker, err := bkt.ListUnfinishedLargeFiles(l.ctx, uploadIDMarker, maxUploads)
	if err != nil {
		return lmi, b2ToObjectError(traceError(err), bucket)
	}
	lmi = ListMultipartsInfo{
		MaxUploads: maxUploads,
	}
	if nextMarker != "" {
		lmi.IsTruncated = true
		lmi.NextUploadIDMarker = nextMarker
	}
	for _, largeFile := range largeFiles {
		lmi.Uploads = append(lmi.Uploads, uploadMetadata{
			Object:    largeFile.Name,
			UploadID:  largeFile.ID,
			Initiated: largeFile.Timestamp,
		})
	}
	return lmi, nil
}

// NewMultipartUpload upload object in multiple parts, uses B2's LargeFile upload API.
// Large files can range in size from 5MB to 10TB.
// Each large file must consist of at least 2 parts, and all of the parts except the
// last one must be at least 5MB in size. The last part must contain at least one byte.
// For more information - https://www.backblaze.com/b2/docs/large_files.html
func (l *b2Objects) NewMultipartUpload(bucket string, object string, metadata map[string]string) (string, error) {
	var uploadID string
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return uploadID, err
	}

	contentType := metadata["content-type"]
	delete(metadata, "content-type")
	lf, err := bkt.StartLargeFile(l.ctx, object, contentType, metadata)
	if err != nil {
		return uploadID, b2ToObjectError(traceError(err), bucket, object)
	}

	return lf.ID, nil
}

// CopyObjectPart copy part of object to other bucket and object.
func (l *b2Objects) CopyObjectPart(srcBucket string, srcObject string, destBucket string, destObject string,
	uploadID string, partID int, startOffset int64, length int64) (info PartInfo, err error) {
	return PartInfo{}, traceError(NotImplemented{})
}

// PutObjectPart puts a part of object in bucket, uses B2's LargeFile upload API.
func (l *b2Objects) PutObjectPart(bucket string, object string, uploadID string, partID int, data *HashReader) (pi PartInfo, err error) {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return pi, err
	}

	fc, err := bkt.File(uploadID, object).CompileParts(0, nil).GetUploadPartURL(l.ctx)
	if err != nil {
		return pi, b2ToObjectError(traceError(err), bucket, object, uploadID)
	}

	hr := newB2Reader(data, data.Size())
	sha1, err := fc.UploadPart(l.ctx, hr, sha1AtEOF, int(hr.Size()), partID)
	if err != nil {
		return pi, b2ToObjectError(traceError(err), bucket, object, uploadID)
	}

	return PartInfo{
		PartNumber:   partID,
		LastModified: UTCNow(),
		ETag:         sha1,
		Size:         data.Size(),
	}, nil
}

// ListObjectParts returns all object parts for specified object in specified bucket, uses B2's LargeFile upload API.
func (l *b2Objects) ListObjectParts(bucket string, object string, uploadID string, partNumberMarker int, maxParts int) (lpi ListPartsInfo, err error) {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return lpi, err
	}
	lpi = ListPartsInfo{
		Bucket:           bucket,
		Object:           object,
		UploadID:         uploadID,
		MaxParts:         maxParts,
		PartNumberMarker: partNumberMarker,
	}
	// startPartNumber must be in the range 1 - 10000 for B2.
	partNumberMarker++
	partsList, next, err := bkt.File(uploadID, object).ListParts(l.ctx, partNumberMarker, maxParts)
	if err != nil {
		return lpi, b2ToObjectError(traceError(err), bucket, object, uploadID)
	}
	if next != 0 {
		lpi.IsTruncated = true
		lpi.NextPartNumberMarker = next
	}
	for _, part := range partsList {
		lpi.Parts = append(lpi.Parts, PartInfo{
			PartNumber: part.Number,
			ETag:       part.SHA1,
			Size:       part.Size,
		})
	}
	return lpi, nil
}

// AbortMultipartUpload aborts a on going multipart upload, uses B2's LargeFile upload API.
func (l *b2Objects) AbortMultipartUpload(bucket string, object string, uploadID string) error {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return err
	}
	err = bkt.File(uploadID, object).CompileParts(0, nil).CancelLargeFile(l.ctx)
	return b2ToObjectError(traceError(err), bucket, object, uploadID)
}

// CompleteMultipartUpload completes ongoing multipart upload and finalizes object, uses B2's LargeFile upload API.
func (l *b2Objects) CompleteMultipartUpload(bucket string, object string, uploadID string, uploadedParts []completePart) (oi ObjectInfo, err error) {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return oi, err
	}
	hashes := make(map[int]string)
	for i, uploadedPart := range uploadedParts {
		// B2 requires contigous part numbers starting with 1, they do not support
		// hand picking part numbers, we return an S3 compatible error instead.
		if i+1 != uploadedPart.PartNumber {
			return oi, b2ToObjectError(traceError(InvalidPart{}), bucket, object, uploadID)
		}
		hashes[uploadedPart.PartNumber] = uploadedPart.ETag
	}

	if _, err = bkt.File(uploadID, object).CompileParts(0, hashes).FinishLargeFile(l.ctx); err != nil {
		return oi, b2ToObjectError(traceError(err), bucket, object, uploadID)
	}

	return l.GetObjectInfo(bucket, object)
}

// SetBucketPolicies - B2 supports 2 types of bucket policies:
// bucketType.AllPublic - bucketTypeReadOnly means that anybody can download the files is the bucket;
// bucketType.AllPrivate - bucketTypePrivate means that you need an authorization token to download them.
// Default is AllPrivate for all buckets.
func (l *b2Objects) SetBucketPolicies(bucket string, policyInfo policy.BucketAccessPolicy) error {
	var policies []BucketAccessPolicy

	for prefix, policy := range policy.GetPolicies(policyInfo.Statements, bucket) {
		policies = append(policies, BucketAccessPolicy{
			Prefix: prefix,
			Policy: policy,
		})
	}
	prefix := bucket + "/*" // For all objects inside the bucket.
	if len(policies) != 1 {
		return traceError(NotImplemented{})
	}
	if policies[0].Prefix != prefix {
		return traceError(NotImplemented{})
	}
	if policies[0].Policy != policy.BucketPolicyReadOnly {
		return traceError(NotImplemented{})
	}
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return err
	}
	bkt.Type = bucketTypeReadOnly
	_, err = bkt.Update(l.ctx)
	return b2ToObjectError(traceError(err))
}

// GetBucketPolicies, returns the current bucketType from B2 backend and convert
// it into S3 compatible bucket policy info.
func (l *b2Objects) GetBucketPolicies(bucket string) (policy.BucketAccessPolicy, error) {
	policyInfo := policy.BucketAccessPolicy{Version: "2012-10-17"}
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return policyInfo, err
	}
	if bkt.Type == bucketTypeReadOnly {
		policyInfo.Statements = policy.SetPolicy(policyInfo.Statements, policy.BucketPolicyReadOnly, bucket, "")
		return policyInfo, nil
	}
	// bkt.Type can also be snapshot, but it is only allowed through B2 browser console,
	// just return back as policy not found for all cases.
	// CreateBucket always sets the value to allPrivate by default.
	return policy.BucketAccessPolicy{}, traceError(PolicyNotFound{Bucket: bucket})
}

// DeleteBucketPolicies - resets the bucketType of bucket on B2 to 'allPrivate'.
func (l *b2Objects) DeleteBucketPolicies(bucket string) error {
	bkt, err := l.Bucket(bucket)
	if err != nil {
		return err
	}
	bkt.Type = bucketTypePrivate
	_, err = bkt.Update(l.ctx)
	return b2ToObjectError(traceError(err))
}