// Package swift provides a storagedriver.StorageDriver implementation to
// store blobs in Openstack Swift object storage.
//
// This package leverages the ncw/swift client library for interfacing with
// Swift.
//
// It supports both TempAuth authentication and Keystone authentication
// (up to version 3).
//
// Since Swift has no concept of directories (directories are an abstration),
// empty objects are created with the MIME type application/vnd.swift.directory.
//
// As Swift has a limit on the size of a single uploaded object (by default
// this is 5GB), the driver makes use of the Swift Large Object Support
// (http://docs.openstack.org/developer/swift/overview_large_objects.html).
// Only one container is used for both manifests and data objects. Manifests
// are stored in the 'files' pseudo directory, data objects are stored under
// 'segments'.
package swift

import (
	"bytes"
	"crypto/tls"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	gopath "path"
	"strconv"
	"strings"
	"time"

	"github.com/mitchellh/mapstructure"
	"github.com/ncw/swift"

	"github.com/docker/distribution/context"
	storagedriver "github.com/docker/distribution/registry/storage/driver"
	"github.com/docker/distribution/registry/storage/driver/base"
	"github.com/docker/distribution/registry/storage/driver/factory"
	"github.com/docker/distribution/version"
)

const driverName = "swift"

// defaultChunkSize defines the default size of a segment
const defaultChunkSize = 20 * 1024 * 1024

// minChunkSize defines the minimum size of a segment
const minChunkSize = 1 << 20

// Vendor MIME type used for objects that act as directories
const directoryMimeType = "application/vnd.swift.directory"

// Parameters A struct that encapsulates all of the driver parameters after all values have been set
type Parameters struct {
	Username           string
	Password           string
	AuthURL            string
	Tenant             string
	TenantID           string
	Domain             string
	DomainID           string
	Region             string
	Container          string
	Prefix             string
	InsecureSkipVerify bool
	ChunkSize          int
}

type swiftInfo map[string]interface{}

func init() {
	factory.Register(driverName, &swiftDriverFactory{})
}

// swiftDriverFactory implements the factory.StorageDriverFactory interface
type swiftDriverFactory struct{}

func (factory *swiftDriverFactory) Create(parameters map[string]interface{}) (storagedriver.StorageDriver, error) {
	return FromParameters(parameters)
}

type driver struct {
	Conn              swift.Connection
	Container         string
	Prefix            string
	BulkDeleteSupport bool
	ChunkSize         int
}

type baseEmbed struct {
	base.Base
}

// Driver is a storagedriver.StorageDriver implementation backed by Openstack Swift
// Objects are stored at absolute keys in the provided container.
type Driver struct {
	baseEmbed
}

// FromParameters constructs a new Driver with a given parameters map
// Required parameters:
// - username
// - password
// - authurl
// - container
func FromParameters(parameters map[string]interface{}) (*Driver, error) {
	params := Parameters{
		ChunkSize:          defaultChunkSize,
		InsecureSkipVerify: false,
	}

	if err := mapstructure.Decode(parameters, &params); err != nil {
		return nil, err
	}

	if params.Username == "" {
		return nil, fmt.Errorf("No username parameter provided")
	}

	if params.Password == "" {
		return nil, fmt.Errorf("No password parameter provided")
	}

	if params.AuthURL == "" {
		return nil, fmt.Errorf("No authurl parameter provided")
	}

	if params.Container == "" {
		return nil, fmt.Errorf("No container parameter provided")
	}

	if params.ChunkSize < minChunkSize {
		return nil, fmt.Errorf("The chunksize %#v parameter should be a number that is larger than or equal to %d", params.ChunkSize, minChunkSize)
	}

	return New(params)
}

// New constructs a new Driver with the given Openstack Swift credentials and container name
func New(params Parameters) (*Driver, error) {
	transport := &http.Transport{
		Proxy:               http.ProxyFromEnvironment,
		MaxIdleConnsPerHost: 2048,
		TLSClientConfig:     &tls.Config{InsecureSkipVerify: params.InsecureSkipVerify},
	}

	ct := swift.Connection{
		UserName:       params.Username,
		ApiKey:         params.Password,
		AuthUrl:        params.AuthURL,
		Region:         params.Region,
		UserAgent:      "distribution/" + version.Version,
		Tenant:         params.Tenant,
		TenantId:       params.TenantID,
		Domain:         params.Domain,
		DomainId:       params.DomainID,
		Transport:      transport,
		ConnectTimeout: 60 * time.Second,
		Timeout:        15 * 60 * time.Second,
	}
	err := ct.Authenticate()
	if err != nil {
		return nil, fmt.Errorf("Swift authentication failed: %s", err)
	}

	if err := ct.ContainerCreate(params.Container, nil); err != nil {
		return nil, fmt.Errorf("Failed to create container %s (%s)", params.Container, err)
	}

	d := &driver{
		Conn:              ct,
		Container:         params.Container,
		Prefix:            params.Prefix,
		BulkDeleteSupport: detectBulkDelete(params.AuthURL),
		ChunkSize:         params.ChunkSize,
	}

	return &Driver{
		baseEmbed: baseEmbed{
			Base: base.Base{
				StorageDriver: d,
			},
		},
	}, nil
}

// Implement the storagedriver.StorageDriver interface

func (d *driver) Name() string {
	return driverName
}

// GetContent retrieves the content stored at "path" as a []byte.
func (d *driver) GetContent(ctx context.Context, path string) ([]byte, error) {
	content, err := d.Conn.ObjectGetBytes(d.Container, d.swiftPath(path))
	if err != nil {
		return nil, parseError(path, err)
	}
	return content, nil
}

// PutContent stores the []byte content at a location designated by "path".
func (d *driver) PutContent(ctx context.Context, path string, contents []byte) error {
	if err := d.createParentFolders(path); err != nil {
		return err
	}
	err := d.Conn.ObjectPutBytes(d.Container, d.swiftPath(path),
		contents, d.getContentType())
	return parseError(path, err)
}

// ReadStream retrieves an io.ReadCloser for the content stored at "path" with a
// given byte offset.
func (d *driver) ReadStream(ctx context.Context, path string, offset int64) (io.ReadCloser, error) {
	headers := make(swift.Headers)
	headers["Range"] = "bytes=" + strconv.FormatInt(offset, 10) + "-"

	file, _, err := d.Conn.ObjectOpen(d.Container, d.swiftPath(path), false, headers)

	if err != nil {
		if swiftErr, ok := err.(*swift.Error); ok && swiftErr.StatusCode == http.StatusRequestedRangeNotSatisfiable {
			return ioutil.NopCloser(bytes.NewReader(nil)), nil
		}

		return nil, parseError(path, err)
	}

	return file, nil
}

// WriteStream stores the contents of the provided io.Reader at a
// location designated by the given path. The driver will know it has
// received the full contents when the reader returns io.EOF. The number
// of successfully READ bytes will be returned, even if an error is
// returned. May be used to resume writing a stream by providing a nonzero
// offset. Offsets past the current size will write from the position
// beyond the end of the file.
func (d *driver) WriteStream(ctx context.Context, path string, offset int64, reader io.Reader) (int64, error) {
	var (
		segments      []swift.Object
		multi         io.Reader
		paddingReader io.Reader
		currentLength int64
		cursor        int64
	)

	partNumber := 1
	chunkSize := int64(d.ChunkSize)
	zeroBuf := make([]byte, d.ChunkSize)

	getSegment := func() string {
		return d.swiftSegmentPath(path) + "/" + fmt.Sprintf("%016d", partNumber)
	}

	max := func(a int64, b int64) int64 {
		if a > b {
			return a
		}
		return b
	}

	info, _, err := d.Conn.Object(d.Container, d.swiftPath(path))
	if err != nil {
		if err == swift.ContainerNotFound || err == swift.ObjectNotFound {
			// Create a object manifest
			if err := d.createParentFolders(path); err != nil {
				return 0, err
			}
			manifest, err := d.createManifest(path)
			if err != nil {
				return 0, parseError(path, err)
			}
			manifest.Close()
		} else {
			return 0, parseError(path, err)
		}
	} else {
		// The manifest already exists. Get all the segments
		currentLength = info.Bytes
		segments, err = d.getAllSegments(path)
		if err != nil {
			return 0, parseError(path, err)
		}
	}

	// First, we skip the existing segments that are not modified by this call
	for i := range segments {
		if offset < cursor+segments[i].Bytes {
			break
		}
		cursor += segments[i].Bytes
		partNumber++
	}

	// We reached the end of the file but we haven't reached 'offset' yet
	// Therefore we add blocks of zeros
	if offset >= currentLength {
		for offset-currentLength >= chunkSize {
			// Insert a block a zero
			d.Conn.ObjectPut(d.Container, getSegment(),
				bytes.NewReader(zeroBuf), false, "",
				d.getContentType(), nil)
			currentLength += chunkSize
			partNumber++
		}

		cursor = currentLength
		paddingReader = bytes.NewReader(zeroBuf)
	} else if offset-cursor > 0 {
		// Offset is inside the current segment : we need to read the
		// data from the beginning of the segment to offset
		file, _, err := d.Conn.ObjectOpen(d.Container, getSegment(), false, nil)
		if err != nil {
			return 0, parseError(getSegment(), err)
		}

		defer file.Close()
		paddingReader = file
	}

	readers := []io.Reader{}
	if paddingReader != nil {
		readers = append(readers, io.LimitReader(paddingReader, offset-cursor))
	}
	readers = append(readers, io.LimitReader(reader, chunkSize-(offset-cursor)))
	multi = io.MultiReader(readers...)

	writeSegment := func(segment string) (finished bool, bytesRead int64, err error) {
		currentSegment, err := d.Conn.ObjectCreate(d.Container, segment, false, "", d.getContentType(), nil)
		if err != nil {
			return false, bytesRead, parseError(path, err)
		}

		n, err := io.Copy(currentSegment, multi)
		if err != nil {
			return false, bytesRead, parseError(path, err)
		}

		if n > 0 {
			defer currentSegment.Close()
			bytesRead += n - max(0, offset-cursor)
		}

		if n < chunkSize {
			// We wrote all the data
			if cursor+n < currentLength {
				// Copy the end of the chunk
				headers := make(swift.Headers)
				headers["Range"] = "bytes=" + strconv.FormatInt(cursor+n, 10) + "-" + strconv.FormatInt(cursor+chunkSize, 10)
				file, _, err := d.Conn.ObjectOpen(d.Container, d.swiftPath(path), false, headers)
				if err != nil {
					return false, bytesRead, parseError(path, err)
				}

				_, copyErr := io.Copy(currentSegment, file)

				if err := file.Close(); err != nil {
					return false, bytesRead, parseError(path, err)
				}

				if copyErr != nil {
					return false, bytesRead, parseError(path, copyErr)
				}
			}

			return true, bytesRead, nil
		}

		multi = io.LimitReader(reader, chunkSize)
		cursor += chunkSize
		partNumber++

		return false, bytesRead, nil
	}

	finished := false
	read := int64(0)
	bytesRead := int64(0)
	for finished == false {
		finished, read, err = writeSegment(getSegment())
		bytesRead += read
		if err != nil {
			return bytesRead, err
		}
	}

	return bytesRead, nil
}

// Stat retrieves the FileInfo for the given path, including the current size
// in bytes and the creation time.
func (d *driver) Stat(ctx context.Context, path string) (storagedriver.FileInfo, error) {
	info, _, err := d.Conn.Object(d.Container, d.swiftPath(path))
	if err != nil {
		return nil, parseError(path, err)
	}

	fi := storagedriver.FileInfoFields{
		Path:    path,
		IsDir:   info.ContentType == directoryMimeType,
		Size:    info.Bytes,
		ModTime: info.LastModified,
	}

	return storagedriver.FileInfoInternal{FileInfoFields: fi}, nil
}

// List returns a list of the objects that are direct descendants of the given path.
func (d *driver) List(ctx context.Context, path string) ([]string, error) {
	var files []string

	prefix := d.swiftPath(path)
	if prefix != "" {
		prefix += "/"
	}

	opts := &swift.ObjectsOpts{
		Prefix:    prefix,
		Delimiter: '/',
	}

	objects, err := d.Conn.Objects(d.Container, opts)
	for _, obj := range objects {
		if !obj.PseudoDirectory {
			files = append(files, strings.TrimPrefix(strings.TrimSuffix(obj.Name, "/"), d.swiftPath("/")))
		}
	}

	return files, parseError(path, err)
}

// Move moves an object stored at sourcePath to destPath, removing the original
// object.
func (d *driver) Move(ctx context.Context, sourcePath string, destPath string) error {
	err := d.Conn.ObjectMove(d.Container, d.swiftPath(sourcePath),
		d.Container, d.swiftPath(destPath))
	if err != nil {
		return parseError(sourcePath, err)
	}

	return nil
}

// Delete recursively deletes all objects stored at "path" and its subpaths.
func (d *driver) Delete(ctx context.Context, path string) error {
	opts := swift.ObjectsOpts{
		Prefix: d.swiftPath(path) + "/",
	}

	objects, err := d.Conn.Objects(d.Container, &opts)
	if err != nil {
		return parseError(path, err)
	}

	if d.BulkDeleteSupport {
		filenames := make([]string, len(objects))
		for i, obj := range objects {
			filenames[i] = obj.Name
		}
		if _, err := d.Conn.BulkDelete(d.Container, filenames); err != swift.Forbidden {
			return parseError(path, err)
		}
	}

	for _, obj := range objects {
		if obj.PseudoDirectory {
			continue
		}
		if _, headers, err := d.Conn.Object(d.Container, obj.Name); err == nil {
			manifest, ok := headers["X-Object-Manifest"]
			if ok {
				components := strings.SplitN(manifest, "/", 2)
				segContainer := components[0]
				segments, err := d.getAllSegments(components[1])
				if err != nil {
					return parseError(obj.Name, err)
				}

				for _, s := range segments {
					if err := d.Conn.ObjectDelete(segContainer, s.Name); err != nil {
						return parseError(s.Name, err)
					}
				}
			}
		} else {
			return parseError(obj.Name, err)
		}

		if err := d.Conn.ObjectDelete(d.Container, obj.Name); err != nil {
			return parseError(obj.Name, err)
		}
	}

	if _, err := d.Stat(ctx, path); err == nil {
		return parseError(path, d.Conn.ObjectDelete(d.Container, d.swiftPath(path)))
	} else if len(objects) == 0 {
		return storagedriver.PathNotFoundError{Path: path}
	}

	return nil
}

// URLFor returns a URL which may be used to retrieve the content stored at the given path.
// May return an UnsupportedMethodErr in certain StorageDriver implementations.
func (d *driver) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
	return "", storagedriver.ErrUnsupportedMethod
}

func (d *driver) swiftPath(path string) string {
	return strings.TrimLeft(strings.TrimRight(d.Prefix+"/files"+path, "/"), "/")
}

func (d *driver) swiftSegmentPath(path string) string {
	return strings.TrimLeft(strings.TrimRight(d.Prefix+"/segments"+path, "/"), "/")
}

func (d *driver) createParentFolders(path string) error {
	dir := gopath.Dir(path)
	for dir != "/" {
		_, _, err := d.Conn.Object(d.Container, d.swiftPath(dir))
		if err == swift.ContainerNotFound || err == swift.ObjectNotFound {
			_, err := d.Conn.ObjectPut(d.Container, d.swiftPath(dir), bytes.NewReader(make([]byte, 0)),
				false, "", directoryMimeType, nil)
			if err != nil {
				return parseError(dir, err)
			}
		}
		dir = gopath.Dir(dir)
	}

	return nil
}

func (d *driver) getContentType() string {
	return "application/octet-stream"
}

func (d *driver) getAllSegments(path string) ([]swift.Object, error) {
	return d.Conn.Objects(d.Container, &swift.ObjectsOpts{Prefix: d.swiftSegmentPath(path)})
}

func (d *driver) createManifest(path string) (*swift.ObjectCreateFile, error) {
	headers := make(swift.Headers)
	headers["X-Object-Manifest"] = d.Container + "/" + d.swiftSegmentPath(path)
	return d.Conn.ObjectCreate(d.Container, d.swiftPath(path), false, "",
		d.getContentType(), headers)
}

func detectBulkDelete(authURL string) (bulkDelete bool) {
	resp, err := http.Get(gopath.Join(authURL, "..", "..") + "/info")
	if err == nil {
		defer resp.Body.Close()
		decoder := json.NewDecoder(resp.Body)
		var infos swiftInfo
		if decoder.Decode(&infos) == nil {
			_, bulkDelete = infos["bulk_delete"]
		}
	}
	return
}

func parseError(path string, err error) error {
	if err == swift.ContainerNotFound || err == swift.ObjectNotFound {
		return storagedriver.PathNotFoundError{Path: path}
	}

	return err
}