package filesystem

import (
	"bytes"
	"crypto/md5"
	"crypto/sha512"
	"encoding/base64"
	"encoding/gob"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"math/rand"
	"os"
	"path"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/minio/minio/pkg/iodine"
	"github.com/minio/minio/pkg/storage/drivers"
)

// MultipartSession holds active session information
type MultipartSession struct {
	TotalParts int
	UploadID   string
	Initiated  time.Time
	Parts      []*drivers.PartMetadata
}

// Multiparts collection of many parts
type Multiparts struct {
	ActiveSession map[string]*MultipartSession
}

// byKey is a sortable interface for UploadMetadata slice
type byKey []*drivers.UploadMetadata

func (a byKey) Len() int           { return len(a) }
func (a byKey) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a byKey) Less(i, j int) bool { return a[i].Key < a[j].Key }

func (fs *fsDriver) ListMultipartUploads(bucket string, resources drivers.BucketMultipartResourcesMetadata) (drivers.BucketMultipartResourcesMetadata, error) {
	fs.lock.Lock()
	defer fs.lock.Unlock()
	if !drivers.IsValidBucket(bucket) {
		return drivers.BucketMultipartResourcesMetadata{}, iodine.New(drivers.BucketNameInvalid{Bucket: bucket}, nil)
	}
	bucketPath := path.Join(fs.root, bucket)
	_, err := os.Stat(bucketPath)

	// check bucket exists
	if os.IsNotExist(err) {
		return drivers.BucketMultipartResourcesMetadata{}, iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
	}
	if err != nil {
		return drivers.BucketMultipartResourcesMetadata{}, iodine.New(drivers.InternalError{}, nil)
	}

	if _, err := os.Stat(bucketPath + "$activeSession"); os.IsNotExist(err) {
		return drivers.BucketMultipartResourcesMetadata{}, nil
	}
	if err != nil {
		return drivers.BucketMultipartResourcesMetadata{}, iodine.New(err, nil)
	}
	activeSessionFile, err := os.OpenFile(bucketPath+"$activeSession", os.O_RDONLY, 0600)
	if err != nil {
		return drivers.BucketMultipartResourcesMetadata{}, iodine.New(err, nil)
	}
	defer activeSessionFile.Close()

	var deserializedActiveSession map[string]*MultipartSession
	decoder := gob.NewDecoder(activeSessionFile)
	err = decoder.Decode(&deserializedActiveSession)
	if err != nil {
		return drivers.BucketMultipartResourcesMetadata{}, iodine.New(err, nil)
	}
	var uploads []*drivers.UploadMetadata
	for key, session := range deserializedActiveSession {
		if strings.HasPrefix(key, resources.Prefix) {
			if len(uploads) > resources.MaxUploads {
				sort.Sort(byKey(uploads))
				resources.Upload = uploads
				resources.NextKeyMarker = key
				resources.NextUploadIDMarker = session.UploadID
				resources.IsTruncated = true
				return resources, nil
			}
			// uploadIDMarker is ignored if KeyMarker is empty
			switch {
			case resources.KeyMarker != "" && resources.UploadIDMarker == "":
				if key > resources.KeyMarker {
					upload := new(drivers.UploadMetadata)
					upload.Key = key
					upload.UploadID = session.UploadID
					upload.Initiated = session.Initiated
					uploads = append(uploads, upload)
				}
			case resources.KeyMarker != "" && resources.UploadIDMarker != "":
				if session.UploadID > resources.UploadIDMarker {
					if key >= resources.KeyMarker {
						upload := new(drivers.UploadMetadata)
						upload.Key = key
						upload.UploadID = session.UploadID
						upload.Initiated = session.Initiated
						uploads = append(uploads, upload)
					}
				}
			default:
				upload := new(drivers.UploadMetadata)
				upload.Key = key
				upload.UploadID = session.UploadID
				upload.Initiated = session.Initiated
				uploads = append(uploads, upload)
			}
		}
	}
	sort.Sort(byKey(uploads))
	resources.Upload = uploads
	return resources, nil
}

func (fs *fsDriver) NewMultipartUpload(bucket, key, contentType string) (string, error) {
	fs.lock.Lock()
	defer fs.lock.Unlock()
	if !drivers.IsValidBucket(bucket) {
		return "", iodine.New(drivers.BucketNameInvalid{Bucket: bucket}, nil)
	}
	if !drivers.IsValidObjectName(key) {
		return "", iodine.New(drivers.ObjectNameInvalid{Object: key}, nil)
	}

	bucketPath := path.Join(fs.root, bucket)
	_, err := os.Stat(bucketPath)
	// check bucket exists
	if os.IsNotExist(err) {
		return "", iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
	}
	if err != nil {
		return "", iodine.New(drivers.InternalError{}, nil)
	}

	var activeSessionFile *os.File
	if _, err := os.Stat(bucketPath + "$activeSession"); os.IsNotExist(err) {
		activeSessionFile, err = os.OpenFile(bucketPath+"$activeSession", os.O_WRONLY|os.O_CREATE, 0600)
		if err != nil {
			return "", iodine.New(err, nil)
		}
	} else {
		activeSessionFile, err = os.OpenFile(bucketPath+"$activeSession", os.O_WRONLY, 0600)
		if err != nil {
			return "", iodine.New(err, nil)
		}
	}
	defer activeSessionFile.Close()

	objectPath := path.Join(bucketPath, key)
	objectDir := path.Dir(objectPath)
	if _, err := os.Stat(objectDir); os.IsNotExist(err) {
		err = os.MkdirAll(objectDir, 0700)
		if err != nil {
			return "", iodine.New(err, nil)
		}
	}

	// check if object exists
	if _, err := os.Stat(objectPath); !os.IsNotExist(err) {
		return "", iodine.New(drivers.ObjectExists{
			Bucket: bucket,
			Object: key,
		}, nil)
	}

	id := []byte(strconv.FormatInt(rand.Int63(), 10) + bucket + key + time.Now().String())
	uploadIDSum := sha512.Sum512(id)
	uploadID := base64.URLEncoding.EncodeToString(uploadIDSum[:])[:47]

	file, err := os.OpenFile(objectPath+"$multiparts", os.O_WRONLY|os.O_CREATE, 0600)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	defer file.Close()

	mpartSession := new(MultipartSession)
	mpartSession.TotalParts = 0
	mpartSession.UploadID = uploadID
	mpartSession.Initiated = time.Now().UTC()
	var parts []*drivers.PartMetadata
	mpartSession.Parts = parts
	fs.multiparts.ActiveSession[key] = mpartSession

	encoder := gob.NewEncoder(file)
	err = encoder.Encode(mpartSession)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	encoder = gob.NewEncoder(activeSessionFile)
	err = encoder.Encode(fs.multiparts.ActiveSession)
	if err != nil {
		return "", iodine.New(err, nil)
	}

	return uploadID, nil
}

func (fs *fsDriver) isValidUploadID(key, uploadID string) bool {
	s, ok := fs.multiparts.ActiveSession[key]
	if !ok {
		return false
	}
	if uploadID == s.UploadID {
		return true
	}
	return false
}

func (fs *fsDriver) writePart(objectPath string, partID int, size int64, data io.Reader) (drivers.PartMetadata, error) {
	partPath := objectPath + fmt.Sprintf("$%d", partID)
	// write part
	partFile, err := os.OpenFile(partPath, os.O_WRONLY|os.O_CREATE, 0600)
	if err != nil {
		return drivers.PartMetadata{}, iodine.New(err, nil)
	}
	defer partFile.Close()

	h := md5.New()
	mw := io.MultiWriter(partFile, h)

	_, err = io.CopyN(mw, data, size)
	if err != nil {
		return drivers.PartMetadata{}, iodine.New(err, nil)
	}

	fi, err := os.Stat(partPath)
	if err != nil {
		return drivers.PartMetadata{}, iodine.New(err, nil)
	}
	partMetadata := drivers.PartMetadata{}
	partMetadata.ETag = hex.EncodeToString(h.Sum(nil))
	partMetadata.PartNumber = partID
	partMetadata.Size = fi.Size()
	partMetadata.LastModified = fi.ModTime()
	return partMetadata, nil
}

// partNumber is a sortable interface for Part slice
type partNumber []*drivers.PartMetadata

func (a partNumber) Len() int           { return len(a) }
func (a partNumber) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a partNumber) Less(i, j int) bool { return a[i].PartNumber < a[j].PartNumber }

func (fs *fsDriver) CreateObjectPart(bucket, key, uploadID string, partID int, contentType, expectedMD5Sum string, size int64, data io.Reader) (string, error) {
	fs.lock.Lock()
	defer fs.lock.Unlock()

	if partID <= 0 {
		return "", iodine.New(errors.New("invalid part id, cannot be zero or less than zero"), nil)
	}
	// check bucket name valid
	if drivers.IsValidBucket(bucket) == false {
		return "", iodine.New(drivers.BucketNameInvalid{Bucket: bucket}, nil)
	}

	// verify object path legal
	if drivers.IsValidObjectName(key) == false {
		return "", iodine.New(drivers.ObjectNameInvalid{Bucket: bucket, Object: key}, nil)
	}

	if !fs.isValidUploadID(key, uploadID) {
		return "", iodine.New(drivers.InvalidUploadID{UploadID: uploadID}, nil)
	}

	if strings.TrimSpace(expectedMD5Sum) != "" {
		expectedMD5SumBytes, err := base64.StdEncoding.DecodeString(strings.TrimSpace(expectedMD5Sum))
		if err != nil {
			// pro-actively close the connection
			return "", iodine.New(drivers.InvalidDigest{Md5: expectedMD5Sum}, nil)
		}
		expectedMD5Sum = hex.EncodeToString(expectedMD5SumBytes)
	}

	bucketPath := path.Join(fs.root, bucket)
	_, err := os.Stat(bucketPath)

	// check bucket exists
	if os.IsNotExist(err) {
		return "", iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
	}
	if err != nil {
		return "", iodine.New(drivers.InternalError{}, nil)
	}

	objectPath := path.Join(bucketPath, key)
	objectDir := path.Dir(objectPath)
	if _, err := os.Stat(objectDir); os.IsNotExist(err) {
		err = os.MkdirAll(objectDir, 0700)
		if err != nil {
			return "", iodine.New(err, nil)
		}
	}

	// check if object exists
	if _, err := os.Stat(objectPath); !os.IsNotExist(err) {
		return "", iodine.New(drivers.ObjectExists{
			Bucket: bucket,
			Object: key,
		}, nil)
	}
	partMetadata, err := fs.writePart(objectPath, partID, size, data)
	if err != nil {
		return "", iodine.New(err, nil)
	}

	// Verify if the written object is equal to what is expected, only if it is requested as such
	if strings.TrimSpace(expectedMD5Sum) != "" {
		if err := isMD5SumEqual(strings.TrimSpace(expectedMD5Sum), partMetadata.ETag); err != nil {
			return "", iodine.New(drivers.BadDigest{Md5: expectedMD5Sum, Bucket: bucket, Key: key}, nil)
		}
	}

	multiPartfile, err := os.OpenFile(objectPath+"$multiparts", os.O_RDWR, 0600)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	defer multiPartfile.Close()

	var deserializedMultipartSession MultipartSession
	decoder := gob.NewDecoder(multiPartfile)
	err = decoder.Decode(&deserializedMultipartSession)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	deserializedMultipartSession.Parts = append(deserializedMultipartSession.Parts, &partMetadata)
	deserializedMultipartSession.TotalParts++
	fs.multiparts.ActiveSession[uploadID] = &deserializedMultipartSession

	sort.Sort(partNumber(deserializedMultipartSession.Parts))
	encoder := gob.NewEncoder(multiPartfile)
	err = encoder.Encode(&deserializedMultipartSession)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	return partMetadata.ETag, nil
}

func (fs *fsDriver) concatParts(parts map[int]string, objectPath string, mw io.Writer) error {
	for i := 1; i <= len(parts); i++ {
		recvMD5 := parts[i]
		partFile, err := os.OpenFile(objectPath+fmt.Sprintf("$%d", i), os.O_RDONLY, 0600)
		if err != nil {
			return iodine.New(err, nil)
		}
		obj, err := ioutil.ReadAll(partFile)
		if err != nil {
			return iodine.New(err, nil)
		}
		calcMD5Bytes := md5.Sum(obj)
		// complete multi part request header md5sum per part is hex encoded
		recvMD5Bytes, err := hex.DecodeString(strings.Trim(recvMD5, "\""))
		if err != nil {
			return iodine.New(drivers.InvalidDigest{Md5: recvMD5}, nil)
		}
		if !bytes.Equal(recvMD5Bytes, calcMD5Bytes[:]) {
			return iodine.New(drivers.BadDigest{Md5: recvMD5}, nil)
		}
		_, err = io.Copy(mw, bytes.NewBuffer(obj))
		if err != nil {
			return iodine.New(err, nil)
		}
	}
	return nil
}

func (fs *fsDriver) CompleteMultipartUpload(bucket, key, uploadID string, parts map[int]string) (string, error) {
	fs.lock.Lock()
	defer fs.lock.Unlock()

	// check bucket name valid
	if drivers.IsValidBucket(bucket) == false {
		return "", iodine.New(drivers.BucketNameInvalid{Bucket: bucket}, nil)
	}

	// verify object path legal
	if drivers.IsValidObjectName(key) == false {
		return "", iodine.New(drivers.ObjectNameInvalid{Bucket: bucket, Object: key}, nil)
	}

	if !fs.isValidUploadID(key, uploadID) {
		return "", iodine.New(drivers.InvalidUploadID{UploadID: uploadID}, nil)
	}

	bucketPath := path.Join(fs.root, bucket)
	_, err := os.Stat(bucketPath)
	// check bucket exists
	if os.IsNotExist(err) {
		return "", iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
	}
	if err != nil {
		return "", iodine.New(drivers.InternalError{}, nil)
	}

	objectPath := path.Join(bucketPath, key)
	// check if object exists
	if _, err := os.Stat(objectPath); !os.IsNotExist(err) {
		return "", iodine.New(drivers.ObjectExists{
			Bucket: bucket,
			Object: key,
		}, nil)
	}

	file, err := os.OpenFile(objectPath, os.O_WRONLY|os.O_CREATE, 0600)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	defer file.Close()
	h := md5.New()
	mw := io.MultiWriter(file, h)
	err = fs.concatParts(parts, objectPath, mw)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	md5sum := hex.EncodeToString(h.Sum(nil))

	delete(fs.multiparts.ActiveSession, uploadID)
	for partNumber := range parts {
		err = os.Remove(objectPath + fmt.Sprintf("$%d", partNumber))
		if err != nil {
			return "", iodine.New(err, nil)
		}
	}
	err = os.Remove(objectPath + "$multiparts")
	if err != nil {
		return "", iodine.New(err, nil)
	}

	file, err = os.OpenFile(objectPath+"$metadata", os.O_WRONLY|os.O_CREATE, 0600)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	defer file.Close()

	metadata := &Metadata{
		ContentType: "application/octet-stream",
		Md5sum:      h.Sum(nil),
	}
	// serialize metadata to gob
	encoder := gob.NewEncoder(file)
	err = encoder.Encode(metadata)
	if err != nil {
		return "", iodine.New(err, nil)
	}

	activeSessionFile, err := os.OpenFile(bucketPath+"$activeSession", os.O_WRONLY, 0600)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	defer activeSessionFile.Close()
	encoder = gob.NewEncoder(activeSessionFile)
	err = encoder.Encode(fs.multiparts.ActiveSession)
	if err != nil {
		return "", iodine.New(err, nil)
	}
	return md5sum, nil
}

func (fs *fsDriver) ListObjectParts(bucket, key string, resources drivers.ObjectResourcesMetadata) (drivers.ObjectResourcesMetadata, error) {
	fs.lock.Lock()
	defer fs.lock.Unlock()

	// check bucket name valid
	if drivers.IsValidBucket(bucket) == false {
		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.BucketNameInvalid{Bucket: bucket}, nil)
	}

	// verify object path legal
	if drivers.IsValidObjectName(key) == false {
		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.ObjectNameInvalid{Bucket: bucket, Object: key}, nil)
	}

	if !fs.isValidUploadID(key, resources.UploadID) {
		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.InvalidUploadID{UploadID: resources.UploadID}, nil)
	}

	objectResourcesMetadata := resources
	objectResourcesMetadata.Bucket = bucket
	objectResourcesMetadata.Key = key
	var startPartNumber int
	switch {
	case objectResourcesMetadata.PartNumberMarker == 0:
		startPartNumber = 1
	default:
		startPartNumber = objectResourcesMetadata.PartNumberMarker
	}

	bucketPath := path.Join(fs.root, bucket)
	_, err := os.Stat(bucketPath)
	// check bucket exists
	if os.IsNotExist(err) {
		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
	}
	if err != nil {
		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.InternalError{}, nil)
	}

	objectPath := path.Join(bucketPath, key)
	multiPartfile, err := os.OpenFile(objectPath+"$multiparts", os.O_RDWR, 0600)
	if err != nil {
		return drivers.ObjectResourcesMetadata{}, iodine.New(err, nil)
	}
	defer multiPartfile.Close()

	var deserializedMultipartSession MultipartSession
	decoder := gob.NewDecoder(multiPartfile)
	err = decoder.Decode(&deserializedMultipartSession)
	if err != nil {
		return drivers.ObjectResourcesMetadata{}, iodine.New(err, nil)
	}
	var parts []*drivers.PartMetadata
	for i := startPartNumber; i <= deserializedMultipartSession.TotalParts; i++ {
		if len(parts) > objectResourcesMetadata.MaxParts {
			sort.Sort(partNumber(parts))
			objectResourcesMetadata.IsTruncated = true
			objectResourcesMetadata.Part = parts
			objectResourcesMetadata.NextPartNumberMarker = i
			return objectResourcesMetadata, nil
		}
		parts = append(parts, deserializedMultipartSession.Parts[i-1])
	}
	sort.Sort(partNumber(parts))
	objectResourcesMetadata.Part = parts
	return objectResourcesMetadata, nil
}

func (fs *fsDriver) AbortMultipartUpload(bucket, key, uploadID string) error {
	fs.lock.Lock()
	defer fs.lock.Unlock()

	// check bucket name valid
	if drivers.IsValidBucket(bucket) == false {
		return iodine.New(drivers.BucketNameInvalid{Bucket: bucket}, nil)
	}

	// verify object path legal
	if drivers.IsValidObjectName(key) == false {
		return iodine.New(drivers.ObjectNameInvalid{Bucket: bucket, Object: key}, nil)
	}

	if !fs.isValidUploadID(key, uploadID) {
		return iodine.New(drivers.InvalidUploadID{UploadID: uploadID}, nil)
	}

	bucketPath := path.Join(fs.root, bucket)
	_, err := os.Stat(bucketPath)
	// check bucket exists
	if os.IsNotExist(err) {
		return iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
	}
	if err != nil {
		return iodine.New(drivers.InternalError{}, nil)
	}

	objectPath := path.Join(bucketPath, key)
	multiPartfile, err := os.OpenFile(objectPath+"$multiparts", os.O_RDWR, 0600)
	if err != nil {
		return iodine.New(err, nil)
	}

	var deserializedMultipartSession MultipartSession
	decoder := gob.NewDecoder(multiPartfile)
	err = decoder.Decode(&deserializedMultipartSession)
	if err != nil {
		return iodine.New(err, nil)
	}
	multiPartfile.Close() // close it right here, since we will delete it subsequently

	delete(fs.multiparts.ActiveSession, uploadID)
	for _, part := range deserializedMultipartSession.Parts {
		err = os.RemoveAll(objectPath + fmt.Sprintf("$%d", part.PartNumber))
		if err != nil {
			return iodine.New(err, nil)
		}
	}
	err = os.RemoveAll(objectPath + "$multiparts")
	if err != nil {
		return iodine.New(err, nil)
	}
	return nil
}