/*
 * Minio Cloud Storage, (C) 2016, 2017, 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"
	"encoding/hex"
	"encoding/json"
	"io"
	"io/ioutil"
	"os"
	pathutil "path"

	"github.com/minio/minio/cmd/logger"
	"github.com/minio/minio/pkg/lock"
	"github.com/minio/minio/pkg/mimedb"
	"github.com/tidwall/gjson"
)

// FS format, and object metadata.
const (
	// fs.json object metadata.
	fsMetaJSONFile = "fs.json"
)

// FS metadata constants.
const (
	// FS backend meta 1.0.0 version.
	fsMetaVersion100 = "1.0.0"

	// FS backend meta 1.0.1 version.
	fsMetaVersion101 = "1.0.1"

	// FS backend meta 1.0.2
	// Removed the fields "Format" and "Minio" from fsMetaV1 as they were unused. Added "Checksum" field - to be used in future for bit-rot protection.
	fsMetaVersion = "1.0.2"

	// Add more constants here.
)

// FSChecksumInfoV1 - carries checksums of individual blocks on disk.
type FSChecksumInfoV1 struct {
	Algorithm string
	Blocksize int64
	Hashes    [][]byte
}

// MarshalJSON marshals the FSChecksumInfoV1 struct
func (c FSChecksumInfoV1) MarshalJSON() ([]byte, error) {
	type checksuminfo struct {
		Algorithm string   `json:"algorithm"`
		Blocksize int64    `json:"blocksize"`
		Hashes    []string `json:"hashes"`
	}
	var hashes []string
	for _, h := range c.Hashes {
		hashes = append(hashes, hex.EncodeToString(h))
	}
	info := checksuminfo{
		Algorithm: c.Algorithm,
		Hashes:    hashes,
		Blocksize: c.Blocksize,
	}
	return json.Marshal(info)
}

// UnmarshalJSON unmarshals the the given data into the FSChecksumInfoV1 struct
func (c *FSChecksumInfoV1) UnmarshalJSON(data []byte) error {
	type checksuminfo struct {
		Algorithm string   `json:"algorithm"`
		Blocksize int64    `json:"blocksize"`
		Hashes    []string `json:"hashes"`
	}

	var info checksuminfo
	err := json.Unmarshal(data, &info)
	if err != nil {
		return err
	}
	c.Algorithm = info.Algorithm
	c.Blocksize = info.Blocksize
	var hashes [][]byte
	for _, hashStr := range info.Hashes {
		h, err := hex.DecodeString(hashStr)
		if err != nil {
			return err
		}
		hashes = append(hashes, h)
	}
	c.Hashes = hashes
	return nil
}

// A fsMetaV1 represents a metadata header mapping keys to sets of values.
type fsMetaV1 struct {
	Version string `json:"version"`
	// checksums of blocks on disk.
	Checksum FSChecksumInfoV1 `json:"checksum,omitempty"`
	// Metadata map for current object.
	Meta map[string]string `json:"meta,omitempty"`
	// parts info for current object - used in encryption.
	Parts []objectPartInfo `json:"parts,omitempty"`
}

// IsValid - tells if the format is sane by validating the version
// string and format style.
func (m fsMetaV1) IsValid() bool {
	return isFSMetaValid(m.Version)
}

// Verifies if the backend format metadata is same by validating
// the version string.
func isFSMetaValid(version string) bool {
	return (version == fsMetaVersion || version == fsMetaVersion100 || version == fsMetaVersion101)
}

// Converts metadata to object info.
func (m fsMetaV1) ToObjectInfo(bucket, object string, fi os.FileInfo) ObjectInfo {
	if len(m.Meta) == 0 {
		m.Meta = make(map[string]string)
	}

	// Guess content-type from the extension if possible.
	if m.Meta["content-type"] == "" {
		m.Meta["content-type"] = mimedb.TypeByExtension(pathutil.Ext(object))
	}

	if hasSuffix(object, slashSeparator) {
		m.Meta["etag"] = emptyETag // For directories etag is d41d8cd98f00b204e9800998ecf8427e
		m.Meta["content-type"] = "application/octet-stream"
	}

	objInfo := ObjectInfo{
		Bucket: bucket,
		Name:   object,
	}

	// We set file info only if its valid.
	objInfo.ModTime = timeSentinel
	if fi != nil {
		objInfo.ModTime = fi.ModTime()
		objInfo.Size = fi.Size()
		if fi.IsDir() {
			// Directory is always 0 bytes in S3 API, treat it as such.
			objInfo.Size = 0
			objInfo.IsDir = fi.IsDir()
		}
	}

	objInfo.ETag = extractETag(m.Meta)
	objInfo.ContentType = m.Meta["content-type"]
	objInfo.ContentEncoding = m.Meta["content-encoding"]
	if storageClass, ok := m.Meta[amzStorageClass]; ok {
		objInfo.StorageClass = storageClass
	} else {
		objInfo.StorageClass = globalMinioDefaultStorageClass
	}

	// etag/md5Sum has already been extracted. We need to
	// remove to avoid it from appearing as part of
	// response headers. e.g, X-Minio-* or X-Amz-*.
	objInfo.UserDefined = cleanMetadata(m.Meta)

	// All the parts per object.
	objInfo.Parts = m.Parts

	// Success..
	return objInfo
}

func (m *fsMetaV1) WriteTo(lk *lock.LockedFile) (n int64, err error) {
	if err = jsonSave(lk, m); err != nil {
		return 0, err
	}
	fi, err := lk.Stat()
	if err != nil {
		return 0, err
	}
	return fi.Size(), nil
}

func parseFSVersion(fsMetaBuf []byte) string {
	return gjson.GetBytes(fsMetaBuf, "version").String()
}

func parseFSMetaMap(fsMetaBuf []byte) map[string]string {
	// Get xlMetaV1.Meta map.
	metaMapResult := gjson.GetBytes(fsMetaBuf, "meta").Map()
	metaMap := make(map[string]string)
	for key, valResult := range metaMapResult {
		metaMap[key] = valResult.String()
	}
	return metaMap
}

func parseFSPartsArray(fsMetaBuf []byte) []objectPartInfo {
	// Get xlMetaV1.Parts array
	var partsArray []objectPartInfo

	partsArrayResult := gjson.GetBytes(fsMetaBuf, "parts")
	partsArrayResult.ForEach(func(key, part gjson.Result) bool {
		partJSON := part.String()
		number := gjson.Get(partJSON, "number").Int()
		name := gjson.Get(partJSON, "name").String()
		etag := gjson.Get(partJSON, "etag").String()
		size := gjson.Get(partJSON, "size").Int()
		actualSize := gjson.Get(partJSON, "actualSize").Int()
		partsArray = append(partsArray, objectPartInfo{
			Number:     int(number),
			Name:       name,
			ETag:       etag,
			Size:       size,
			ActualSize: int64(actualSize),
		})
		return true
	})
	return partsArray
}

func (m *fsMetaV1) ReadFrom(ctx context.Context, lk *lock.LockedFile) (n int64, err error) {
	var fsMetaBuf []byte
	fi, err := lk.Stat()
	if err != nil {
		logger.LogIf(ctx, err)
		return 0, err
	}

	fsMetaBuf, err = ioutil.ReadAll(io.NewSectionReader(lk, 0, fi.Size()))
	if err != nil {
		logger.LogIf(ctx, err)
		return 0, err
	}

	if len(fsMetaBuf) == 0 {
		logger.LogIf(ctx, io.EOF)
		return 0, io.EOF
	}

	// obtain version.
	m.Version = parseFSVersion(fsMetaBuf)

	// Verify if the format is valid, return corrupted format
	// for unrecognized formats.
	if !isFSMetaValid(m.Version) {
		logger.GetReqInfo(ctx).AppendTags("file", lk.Name())
		logger.LogIf(ctx, errCorruptedFormat)
		return 0, errCorruptedFormat
	}

	// obtain parts information
	m.Parts = parseFSPartsArray(fsMetaBuf)

	// obtain metadata.
	m.Meta = parseFSMetaMap(fsMetaBuf)

	// Success.
	return int64(len(fsMetaBuf)), nil
}

// newFSMetaV1 - initializes new fsMetaV1.
func newFSMetaV1() (fsMeta fsMetaV1) {
	fsMeta = fsMetaV1{}
	fsMeta.Version = fsMetaVersion
	return fsMeta
}