// Copyright 2018 The Go Cloud Development Kit Authors
//
// 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
//
//     https://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 s3blob provides a blob implementation that uses S3. Use OpenBucket
// to construct a *blob.Bucket.
//
// # URLs
//
// For blob.OpenBucket, s3blob registers for the scheme "s3".
// The default URL opener will use an AWS session with the default credentials
// and configuration; see https://docs.aws.amazon.com/sdk-for-go/api/aws/session/
// for more details.
// Use "awssdk=v1" or "awssdk=v2" to force a specific AWS SDK version.
// To customize the URL opener, or for more details on the URL format,
// see URLOpener.
// See https://gocloud.dev/concepts/urls/ for background information.
//
// # Escaping
//
// Go CDK supports all UTF-8 strings; to make this work with services lacking
// full UTF-8 support, strings must be escaped (during writes) and unescaped
// (during reads). The following escapes are performed for s3blob:
//   - Blob keys: ASCII characters 0-31 are escaped to "__0x<hex>__".
//     Additionally, the "/" in "../" is escaped in the same way.
//   - Metadata keys: Escaped using URL encoding, then additionally "@:=" are
//     escaped using "__0x<hex>__". These characters were determined by
//     experimentation.
//   - Metadata values: Escaped using URL encoding.
//
// # As
//
// s3blob exposes the following types for As:
//   - Bucket: (V1) *s3.S3; (V2) *s3v2.Client
//   - Error: (V1) awserr.Error; (V2) any error type returned by the service, notably smithy.APIError
//   - ListObject: (V1) s3.Object for objects, s3.CommonPrefix for "directories"; (V2) typesv2.Object for objects, typesv2.CommonPrefix for "directories"
//   - ListOptions.BeforeList: (V1) *s3.ListObjectsV2Input or *s3.ListObjectsInput
//     when Options.UseLegacyList == true; (V2) *s3v2.ListObjectsV2Input or *[]func(*s3v2.Options), or *s3v2.ListObjectsInput
//     when Options.UseLegacyList == true
//   - Reader: (V1) s3.GetObjectOutput; (V2) s3v2.GetObjectInput
//   - ReaderOptions.BeforeRead: (V1) *s3.GetObjectInput; (V2) *s3v2.GetObjectInput or *[]func(*s3v2.Options)
//   - Attributes: (V1) s3.HeadObjectOutput; (V2)s3v2.HeadObjectOutput
//   - CopyOptions.BeforeCopy: *(V1) s3.CopyObjectInput; (V2) s3v2.CopyObjectInput
//   - WriterOptions.BeforeWrite: (V1) *s3manager.UploadInput, *s3manager.Uploader; (V2) *s3v2.PutObjectInput, *s3v2manager.Uploader
//   - SignedURLOptions.BeforeSign:
//     (V1) *s3.GetObjectInput; (V2) *s3v2.GetObjectInput, when Options.Method == http.MethodGet, or
//     (V1) *s3.PutObjectInput; (V2) *s3v2.PutObjectInput, when Options.Method == http.MethodPut, or
//     (V1) *s3.DeleteObjectInput; (V2) [not supported] when Options.Method == http.MethodDelete
package s3blob // import "gocloud.dev/blob/s3blob"

import (
	"context"
	"encoding/base64"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"sort"
	"strconv"
	"strings"

	s3managerv2 "github.com/aws/aws-sdk-go-v2/feature/s3/manager"
	s3v2 "github.com/aws/aws-sdk-go-v2/service/s3"
	typesv2 "github.com/aws/aws-sdk-go-v2/service/s3/types"
	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/awserr"
	"github.com/aws/aws-sdk-go/aws/client"
	"github.com/aws/aws-sdk-go/aws/request"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/aws/aws-sdk-go/service/s3/s3manager"
	"github.com/aws/smithy-go"
	"github.com/google/wire"
	gcaws "gocloud.dev/aws"
	"gocloud.dev/blob"
	"gocloud.dev/blob/driver"
	"gocloud.dev/gcerrors"
	"gocloud.dev/internal/escape"
	"gocloud.dev/internal/gcerr"
)

const defaultPageSize = 1000

func init() {
	blob.DefaultURLMux().RegisterBucket(Scheme, new(urlSessionOpener))
}

// Set holds Wire providers for this package.
var Set = wire.NewSet(
	wire.Struct(new(URLOpener), "ConfigProvider"),
)

type urlSessionOpener struct{}

func (o *urlSessionOpener) OpenBucketURL(ctx context.Context, u *url.URL) (*blob.Bucket, error) {
	if gcaws.UseV2(u.Query()) {
		opener := &URLOpener{UseV2: true}
		return opener.OpenBucketURL(ctx, u)
	}
	sess, rest, err := gcaws.NewSessionFromURLParams(u.Query())
	if err != nil {
		return nil, fmt.Errorf("open bucket %v: %v", u, err)
	}
	opener := &URLOpener{
		ConfigProvider: sess,
	}
	u.RawQuery = rest.Encode()
	return opener.OpenBucketURL(ctx, u)
}

// Scheme is the URL scheme s3blob registers its URLOpener under on
// blob.DefaultMux.
const Scheme = "s3"

// URLOpener opens S3 URLs like "s3://mybucket".
//
// The URL host is used as the bucket name.
//
// Use "awssdk=v1" to force using AWS SDK v1, "awssdk=v2" to force using AWS SDK v2,
// or anything else to accept the default.
//
// For V1, see gocloud.dev/aws/ConfigFromURLParams for supported query parameters
// for overriding the aws.Session from the URL.
// For V2, see gocloud.dev/aws/V2ConfigFromURLParams.
type URLOpener struct {
	// UseV2 indicates whether the AWS SDK V2 should be used.
	UseV2 bool

	// ConfigProvider must be set to a non-nil value if UseV2 is false.
	ConfigProvider client.ConfigProvider

	// Options specifies the options to pass to OpenBucket.
	Options Options
}

const (
	sseTypeParamKey  = "ssetype"
	kmsKeyIdParamKey = "kmskeyid"
)

func toServerSideEncryptionType(value string) (typesv2.ServerSideEncryption, error) {
	for _, sseType := range typesv2.ServerSideEncryptionAes256.Values() {
		if strings.EqualFold(string(sseType), value) {
			return sseType, nil
		}
	}
	return "", fmt.Errorf("%q is not a valid value for %q", value, sseTypeParamKey)
}

// OpenBucketURL opens a blob.Bucket based on u.
func (o *URLOpener) OpenBucketURL(ctx context.Context, u *url.URL) (*blob.Bucket, error) {
	q := u.Query()

	if sseTypeParam := q.Get(sseTypeParamKey); sseTypeParam != "" {
		q.Del(sseTypeParamKey)

		sseType, err := toServerSideEncryptionType(sseTypeParam)
		if err != nil {
			return nil, err
		}

		o.Options.EncryptionType = sseType
	}

	if kmsKeyID := q.Get(kmsKeyIdParamKey); kmsKeyID != "" {
		q.Del(kmsKeyIdParamKey)
		o.Options.KMSEncryptionID = kmsKeyID
	}

	if o.UseV2 {
		cfg, err := gcaws.V2ConfigFromURLParams(ctx, q)
		if err != nil {
			return nil, fmt.Errorf("open bucket %v: %v", u, err)
		}
		clientV2 := s3v2.NewFromConfig(cfg)

		return OpenBucketV2(ctx, clientV2, u.Host, &o.Options)
	}
	configProvider := &gcaws.ConfigOverrider{
		Base: o.ConfigProvider,
	}
	overrideCfg, err := gcaws.ConfigFromURLParams(q)
	if err != nil {
		return nil, fmt.Errorf("open bucket %v: %v", u, err)
	}
	configProvider.Configs = append(configProvider.Configs, overrideCfg)

	return OpenBucket(ctx, configProvider, u.Host, &o.Options)
}

// Options sets options for constructing a *blob.Bucket backed by fileblob.
type Options struct {
	// UseLegacyList forces the use of ListObjects instead of ListObjectsV2.
	// Some S3-compatible services (like CEPH) do not currently support
	// ListObjectsV2.
	UseLegacyList bool

	// EncryptionType sets the encryption type headers when making write or
	// copy calls. This is required if the bucket has a restrictive bucket
	// policy that enforces a specific encryption type
	EncryptionType typesv2.ServerSideEncryption

	// KMSEncryptionID sets the kms key id header for write or copy calls.
	// This is required when a bucket policy enforces the use of a specific
	// KMS key for uploads
	KMSEncryptionID string
}

// openBucket returns an S3 Bucket.
func openBucket(ctx context.Context, useV2 bool, sess client.ConfigProvider, clientV2 *s3v2.Client, bucketName string, opts *Options) (*bucket, error) {
	if bucketName == "" {
		return nil, errors.New("s3blob.OpenBucket: bucketName is required")
	}
	if opts == nil {
		opts = &Options{}
	}
	var client *s3.S3
	if useV2 {
		if clientV2 == nil {
			return nil, errors.New("s3blob.OpenBucketV2: client is required")
		}
	} else {
		if sess == nil {
			return nil, errors.New("s3blob.OpenBucket: sess is required")
		}
		client = s3.New(sess)
	}
	return &bucket{
		useV2:          useV2,
		name:           bucketName,
		client:         client,
		clientV2:       clientV2,
		useLegacyList:  opts.UseLegacyList,
		kmsKeyId:       opts.KMSEncryptionID,
		encryptionType: opts.EncryptionType,
	}, nil
}

// OpenBucket returns a *blob.Bucket backed by S3.
// AWS buckets are bound to a region; sess must have been created using an
// aws.Config with Region set to the right region for bucketName.
// See the package documentation for an example.
//
// Deprecated: AWS no longer supports their V1 API. Please migrate to OpenBucketV2.
func OpenBucket(ctx context.Context, sess client.ConfigProvider, bucketName string, opts *Options) (*blob.Bucket, error) {
	drv, err := openBucket(ctx, false, sess, nil, bucketName, opts)
	if err != nil {
		return nil, err
	}
	return blob.NewBucket(drv), nil
}

// OpenBucketV2 returns a *blob.Bucket backed by S3, using AWS SDK v2.
func OpenBucketV2(ctx context.Context, client *s3v2.Client, bucketName string, opts *Options) (*blob.Bucket, error) {
	drv, err := openBucket(ctx, true, nil, client, bucketName, opts)
	if err != nil {
		return nil, err
	}
	return blob.NewBucket(drv), nil
}

// reader reads an S3 object. It implements io.ReadCloser.
type reader struct {
	useV2 bool
	body  io.ReadCloser
	attrs driver.ReaderAttributes
	raw   *s3.GetObjectOutput
	rawV2 *s3v2.GetObjectOutput
}

func (r *reader) Read(p []byte) (int, error) {
	return r.body.Read(p)
}

// Close closes the reader itself. It must be called when done reading.
func (r *reader) Close() error {
	return r.body.Close()
}

func (r *reader) As(i interface{}) bool {
	if r.useV2 {
		p, ok := i.(*s3v2.GetObjectOutput)
		if !ok {
			return false
		}
		*p = *r.rawV2
	} else {
		p, ok := i.(*s3.GetObjectOutput)
		if !ok {
			return false
		}
		*p = *r.raw
	}
	return true
}

func (r *reader) Attributes() *driver.ReaderAttributes {
	return &r.attrs
}

// writer writes an S3 object, it implements io.WriteCloser.
type writer struct {
	// Ends of an io.Pipe, created when the first byte is written.
	pw *io.PipeWriter
	pr *io.PipeReader

	// Alternatively, upload is set to true when Upload was
	// used to upload data.
	upload bool

	ctx   context.Context
	useV2 bool
	// v1
	uploader *s3manager.Uploader
	req      *s3manager.UploadInput
	// v2
	uploaderV2 *s3managerv2.Uploader
	reqV2      *s3v2.PutObjectInput

	donec chan struct{} // closed when done writing
	// The following fields will be written before donec closes:
	err error
}

// Write appends p to w.pw. User must call Close to close the w after done writing.
func (w *writer) Write(p []byte) (int, error) {
	// Avoid opening the pipe for a zero-length write;
	// the concrete can do these for empty blobs.
	if len(p) == 0 {
		return 0, nil
	}
	if w.pw == nil {
		// We'll write into pw and use pr as an io.Reader for the
		// Upload call to S3.
		w.pr, w.pw = io.Pipe()
		w.open(w.pr, true)
	}
	return w.pw.Write(p)
}

// Upload reads from r. Per the driver, it is guaranteed to be the only
// write call for this writer.
func (w *writer) Upload(r io.Reader) error {
	w.upload = true
	w.open(r, false)
	return nil
}

// r may be nil if we're Closing and no data was written.
// If closePipeOnError is true, w.pr will be closed if there's an
// error uploading to S3.
func (w *writer) open(r io.Reader, closePipeOnError bool) {
	// This goroutine will keep running until Close, unless there's an error.
	go func() {
		defer close(w.donec)

		if r == nil {
			// AWS doesn't like a nil Body.
			r = http.NoBody
		}
		var err error
		if w.useV2 {
			w.reqV2.Body = r
			_, err = w.uploaderV2.Upload(w.ctx, w.reqV2)
		} else {
			w.req.Body = r
			_, err = w.uploader.UploadWithContext(w.ctx, w.req)
		}
		if err != nil {
			if closePipeOnError {
				w.pr.CloseWithError(err)
				w.pr = nil
			}
			w.err = err
		}
	}()
}

// Close completes the writer and closes it. Any error occurring during write
// will be returned. If a writer is closed before any Write is called, Close
// will create an empty file at the given key.
func (w *writer) Close() error {
	if !w.upload {
		if w.pr != nil {
			defer w.pr.Close()
		}
		if w.pw == nil {
			// We never got any bytes written. We'll write an http.NoBody.
			w.open(nil, false)
		} else if err := w.pw.Close(); err != nil {
			return err
		}
	}
	<-w.donec
	return w.err
}

// bucket represents an S3 bucket and handles read, write and delete operations.
type bucket struct {
	name          string
	useV2         bool
	client        *s3.S3
	clientV2      *s3v2.Client
	useLegacyList bool

	encryptionType typesv2.ServerSideEncryption
	kmsKeyId       string
}

func (b *bucket) Close() error {
	return nil
}

func (b *bucket) ErrorCode(err error) gcerrors.ErrorCode {
	var code string
	if b.useV2 {
		var ae smithy.APIError
		var oe *smithy.OperationError
		if errors.As(err, &oe) && strings.Contains(oe.Error(), "301") {
			// V2 returns an OperationError with a missing redirect for invalid buckets.
			code = "NoSuchBucket"
		} else if errors.As(err, &ae) {
			code = ae.ErrorCode()
		} else {
			return gcerrors.Unknown
		}
	} else {
		e, ok := err.(awserr.Error)
		if !ok {
			return gcerrors.Unknown
		}
		code = e.Code()
	}
	switch {
	case code == "NoSuchBucket" || code == "NoSuchKey" || code == "NotFound" || code == s3.ErrCodeObjectNotInActiveTierError:
		return gcerrors.NotFound
	default:
		return gcerrors.Unknown
	}
}

// ListPaged implements driver.ListPaged.
func (b *bucket) ListPaged(ctx context.Context, opts *driver.ListOptions) (*driver.ListPage, error) {
	pageSize := opts.PageSize
	if pageSize == 0 {
		pageSize = defaultPageSize
	}
	if b.useV2 {
		in := &s3v2.ListObjectsV2Input{
			Bucket:  aws.String(b.name),
			MaxKeys: aws.Int32(int32(pageSize)),
		}
		if len(opts.PageToken) > 0 {
			in.ContinuationToken = aws.String(string(opts.PageToken))
		}
		if opts.Prefix != "" {
			in.Prefix = aws.String(escapeKey(opts.Prefix))
		}
		if opts.Delimiter != "" {
			in.Delimiter = aws.String(escapeKey(opts.Delimiter))
		}
		resp, err := b.listObjectsV2(ctx, in, opts)
		if err != nil {
			return nil, err
		}
		page := driver.ListPage{}
		if resp.NextContinuationToken != nil {
			page.NextPageToken = []byte(*resp.NextContinuationToken)
		}
		if n := len(resp.Contents) + len(resp.CommonPrefixes); n > 0 {
			page.Objects = make([]*driver.ListObject, n)
			for i, obj := range resp.Contents {
				obj := obj
				page.Objects[i] = &driver.ListObject{
					Key:     unescapeKey(aws.StringValue(obj.Key)),
					ModTime: *obj.LastModified,
					Size:    aws.Int64Value(obj.Size),
					MD5:     eTagToMD5(obj.ETag),
					AsFunc: func(i interface{}) bool {
						p, ok := i.(*typesv2.Object)
						if !ok {
							return false
						}
						*p = obj
						return true
					},
				}
			}
			for i, prefix := range resp.CommonPrefixes {
				prefix := prefix
				page.Objects[i+len(resp.Contents)] = &driver.ListObject{
					Key:   unescapeKey(aws.StringValue(prefix.Prefix)),
					IsDir: true,
					AsFunc: func(i interface{}) bool {
						p, ok := i.(*typesv2.CommonPrefix)
						if !ok {
							return false
						}
						*p = prefix
						return true
					},
				}
			}
			if len(resp.Contents) > 0 && len(resp.CommonPrefixes) > 0 {
				// S3 gives us blobs and "directories" in separate lists; sort them.
				sort.Slice(page.Objects, func(i, j int) bool {
					return page.Objects[i].Key < page.Objects[j].Key
				})
			}
		}
		return &page, nil
	} else {
		in := &s3.ListObjectsV2Input{
			Bucket:  aws.String(b.name),
			MaxKeys: aws.Int64(int64(pageSize)),
		}
		if len(opts.PageToken) > 0 {
			in.ContinuationToken = aws.String(string(opts.PageToken))
		}
		if opts.Prefix != "" {
			in.Prefix = aws.String(escapeKey(opts.Prefix))
		}
		if opts.Delimiter != "" {
			in.Delimiter = aws.String(escapeKey(opts.Delimiter))
		}
		resp, err := b.listObjects(ctx, in, opts)
		if err != nil {
			return nil, err
		}
		page := driver.ListPage{}
		if resp.NextContinuationToken != nil {
			page.NextPageToken = []byte(*resp.NextContinuationToken)
		}
		if n := len(resp.Contents) + len(resp.CommonPrefixes); n > 0 {
			page.Objects = make([]*driver.ListObject, n)
			for i, obj := range resp.Contents {
				obj := obj
				page.Objects[i] = &driver.ListObject{
					Key:     unescapeKey(aws.StringValue(obj.Key)),
					ModTime: *obj.LastModified,
					Size:    *obj.Size,
					MD5:     eTagToMD5(obj.ETag),
					AsFunc: func(i interface{}) bool {
						p, ok := i.(*s3.Object)
						if !ok {
							return false
						}
						*p = *obj
						return true
					},
				}
			}
			for i, prefix := range resp.CommonPrefixes {
				prefix := prefix
				page.Objects[i+len(resp.Contents)] = &driver.ListObject{
					Key:   unescapeKey(aws.StringValue(prefix.Prefix)),
					IsDir: true,
					AsFunc: func(i interface{}) bool {
						p, ok := i.(*s3.CommonPrefix)
						if !ok {
							return false
						}
						*p = *prefix
						return true
					},
				}
			}
			if len(resp.Contents) > 0 && len(resp.CommonPrefixes) > 0 {
				// S3 gives us blobs and "directories" in separate lists; sort them.
				sort.Slice(page.Objects, func(i, j int) bool {
					return page.Objects[i].Key < page.Objects[j].Key
				})
			}
		}
		return &page, nil
	}
}

func (b *bucket) listObjectsV2(ctx context.Context, in *s3v2.ListObjectsV2Input, opts *driver.ListOptions) (*s3v2.ListObjectsV2Output, error) {
	if !b.useLegacyList {
		var varopt []func(*s3v2.Options)
		if opts.BeforeList != nil {
			asFunc := func(i interface{}) bool {
				if p, ok := i.(**s3v2.ListObjectsV2Input); ok {
					*p = in
					return true
				}
				if p, ok := i.(**[]func(*s3v2.Options)); ok {
					*p = &varopt
					return true
				}
				return false
			}
			if err := opts.BeforeList(asFunc); err != nil {
				return nil, err
			}
		}
		return b.clientV2.ListObjectsV2(ctx, in, varopt...)
	}

	// Use the legacy ListObjects request.
	legacyIn := &s3v2.ListObjectsInput{
		Bucket:       in.Bucket,
		Delimiter:    in.Delimiter,
		EncodingType: in.EncodingType,
		Marker:       in.ContinuationToken,
		MaxKeys:      in.MaxKeys,
		Prefix:       in.Prefix,
		RequestPayer: in.RequestPayer,
	}
	if opts.BeforeList != nil {
		asFunc := func(i interface{}) bool {
			p, ok := i.(**s3v2.ListObjectsInput)
			if !ok {
				return false
			}
			*p = legacyIn
			return true
		}
		if err := opts.BeforeList(asFunc); err != nil {
			return nil, err
		}
	}
	legacyResp, err := b.clientV2.ListObjects(ctx, legacyIn)
	if err != nil {
		return nil, err
	}

	var nextContinuationToken *string
	if legacyResp.NextMarker != nil {
		nextContinuationToken = legacyResp.NextMarker
	} else if aws.BoolValue(legacyResp.IsTruncated) {
		nextContinuationToken = aws.String(aws.StringValue(legacyResp.Contents[len(legacyResp.Contents)-1].Key))
	}
	return &s3v2.ListObjectsV2Output{
		CommonPrefixes:        legacyResp.CommonPrefixes,
		Contents:              legacyResp.Contents,
		NextContinuationToken: nextContinuationToken,
	}, nil
}

func (b *bucket) listObjects(ctx context.Context, in *s3.ListObjectsV2Input, opts *driver.ListOptions) (*s3.ListObjectsV2Output, error) {
	if !b.useLegacyList {
		if opts.BeforeList != nil {
			asFunc := func(i interface{}) bool {
				if p, ok := i.(**s3.ListObjectsV2Input); ok {
					*p = in
					return true
				}
				return false
			}
			if err := opts.BeforeList(asFunc); err != nil {
				return nil, err
			}
		}
		return b.client.ListObjectsV2WithContext(ctx, in)
	}

	// Use the legacy ListObjects request.
	legacyIn := &s3.ListObjectsInput{
		Bucket:       in.Bucket,
		Delimiter:    in.Delimiter,
		EncodingType: in.EncodingType,
		Marker:       in.ContinuationToken,
		MaxKeys:      in.MaxKeys,
		Prefix:       in.Prefix,
		RequestPayer: in.RequestPayer,
	}
	if opts.BeforeList != nil {
		asFunc := func(i interface{}) bool {
			p, ok := i.(**s3.ListObjectsInput)
			if !ok {
				return false
			}
			*p = legacyIn
			return true
		}
		if err := opts.BeforeList(asFunc); err != nil {
			return nil, err
		}
	}
	legacyResp, err := b.client.ListObjectsWithContext(ctx, legacyIn)
	if err != nil {
		return nil, err
	}

	var nextContinuationToken *string
	if legacyResp.NextMarker != nil {
		nextContinuationToken = legacyResp.NextMarker
	} else if aws.BoolValue(legacyResp.IsTruncated) {
		nextContinuationToken = aws.String(aws.StringValue(legacyResp.Contents[len(legacyResp.Contents)-1].Key))
	}
	return &s3.ListObjectsV2Output{
		CommonPrefixes:        legacyResp.CommonPrefixes,
		Contents:              legacyResp.Contents,
		NextContinuationToken: nextContinuationToken,
	}, nil
}

// As implements driver.As.
func (b *bucket) As(i interface{}) bool {
	if b.useV2 {
		p, ok := i.(**s3v2.Client)
		if !ok {
			return false
		}
		*p = b.clientV2
	} else {
		p, ok := i.(**s3.S3)
		if !ok {
			return false
		}
		*p = b.client
	}
	return true
}

// As implements driver.ErrorAs.
func (b *bucket) ErrorAs(err error, i interface{}) bool {
	if b.useV2 {
		return errors.As(err, i)
	}
	switch v := err.(type) {
	case awserr.Error:
		if p, ok := i.(*awserr.Error); ok {
			*p = v
			return true
		}
	}
	return false
}

// Attributes implements driver.Attributes.
func (b *bucket) Attributes(ctx context.Context, key string) (*driver.Attributes, error) {
	key = escapeKey(key)
	if b.useV2 {
		in := &s3v2.HeadObjectInput{
			Bucket: aws.String(b.name),
			Key:    aws.String(key),
		}
		resp, err := b.clientV2.HeadObject(ctx, in)
		if err != nil {
			return nil, err
		}

		md := make(map[string]string, len(resp.Metadata))
		for k, v := range resp.Metadata {
			// See the package comments for more details on escaping of metadata
			// keys & values.
			md[escape.HexUnescape(escape.URLUnescape(k))] = escape.URLUnescape(v)
		}
		return &driver.Attributes{
			CacheControl:       aws.StringValue(resp.CacheControl),
			ContentDisposition: aws.StringValue(resp.ContentDisposition),
			ContentEncoding:    aws.StringValue(resp.ContentEncoding),
			ContentLanguage:    aws.StringValue(resp.ContentLanguage),
			ContentType:        aws.StringValue(resp.ContentType),
			Metadata:           md,
			// CreateTime not supported; left as the zero time.
			ModTime: aws.TimeValue(resp.LastModified),
			Size:    aws.Int64Value(resp.ContentLength),
			MD5:     eTagToMD5(resp.ETag),
			ETag:    aws.StringValue(resp.ETag),
			AsFunc: func(i interface{}) bool {
				p, ok := i.(*s3v2.HeadObjectOutput)
				if !ok {
					return false
				}
				*p = *resp
				return true
			},
		}, nil
	} else {
		in := &s3.HeadObjectInput{
			Bucket: aws.String(b.name),
			Key:    aws.String(key),
		}
		resp, err := b.client.HeadObjectWithContext(ctx, in)
		if err != nil {
			return nil, err
		}

		md := make(map[string]string, len(resp.Metadata))
		for k, v := range resp.Metadata {
			// See the package comments for more details on escaping of metadata
			// keys & values.
			md[escape.HexUnescape(escape.URLUnescape(k))] = escape.URLUnescape(aws.StringValue(v))
		}
		return &driver.Attributes{
			CacheControl:       aws.StringValue(resp.CacheControl),
			ContentDisposition: aws.StringValue(resp.ContentDisposition),
			ContentEncoding:    aws.StringValue(resp.ContentEncoding),
			ContentLanguage:    aws.StringValue(resp.ContentLanguage),
			ContentType:        aws.StringValue(resp.ContentType),
			Metadata:           md,
			// CreateTime not supported; left as the zero time.
			ModTime: aws.TimeValue(resp.LastModified),
			Size:    aws.Int64Value(resp.ContentLength),
			MD5:     eTagToMD5(resp.ETag),
			ETag:    aws.StringValue(resp.ETag),
			AsFunc: func(i interface{}) bool {
				p, ok := i.(*s3.HeadObjectOutput)
				if !ok {
					return false
				}
				*p = *resp
				return true
			},
		}, nil
	}
}

// NewRangeReader implements driver.NewRangeReader.
func (b *bucket) NewRangeReader(ctx context.Context, key string, offset, length int64, opts *driver.ReaderOptions) (driver.Reader, error) {
	key = escapeKey(key)
	var byteRange *string
	if offset > 0 && length < 0 {
		byteRange = aws.String(fmt.Sprintf("bytes=%d-", offset))
	} else if length == 0 {
		// AWS doesn't support a zero-length read; we'll read 1 byte and then
		// ignore it in favor of http.NoBody below.
		byteRange = aws.String(fmt.Sprintf("bytes=%d-%d", offset, offset))
	} else if length >= 0 {
		byteRange = aws.String(fmt.Sprintf("bytes=%d-%d", offset, offset+length-1))
	}
	if b.useV2 {
		in := &s3v2.GetObjectInput{
			Bucket: aws.String(b.name),
			Key:    aws.String(key),
			Range:  byteRange,
		}
		var varopt []func(*s3v2.Options)
		if opts.BeforeRead != nil {
			asFunc := func(i interface{}) bool {
				if p, ok := i.(**s3v2.GetObjectInput); ok {
					*p = in
					return true
				}
				if p, ok := i.(**[]func(*s3v2.Options)); ok {
					*p = &varopt
					return true
				}
				return false
			}
			if err := opts.BeforeRead(asFunc); err != nil {
				return nil, err
			}
		}
		resp, err := b.clientV2.GetObject(ctx, in, varopt...)
		if err != nil {
			return nil, err
		}
		body := resp.Body
		if length == 0 {
			body = http.NoBody
		}
		return &reader{
			useV2: true,
			body:  body,
			attrs: driver.ReaderAttributes{
				ContentType: aws.StringValue(resp.ContentType),
				ModTime:     aws.TimeValue(resp.LastModified),
				Size:        getSize(aws.Int64Value(resp.ContentLength), aws.StringValue(resp.ContentRange)),
			},
			rawV2: resp,
		}, nil
	} else {
		in := &s3.GetObjectInput{
			Bucket: aws.String(b.name),
			Key:    aws.String(key),
			Range:  byteRange,
		}
		if opts.BeforeRead != nil {
			asFunc := func(i interface{}) bool {
				if p, ok := i.(**s3.GetObjectInput); ok {
					*p = in
					return true
				}
				return false
			}
			if err := opts.BeforeRead(asFunc); err != nil {
				return nil, err
			}
		}
		resp, err := b.client.GetObjectWithContext(ctx, in)
		if err != nil {
			return nil, err
		}
		body := resp.Body
		if length == 0 {
			body = http.NoBody
		}
		return &reader{
			useV2: false,
			body:  body,
			attrs: driver.ReaderAttributes{
				ContentType: aws.StringValue(resp.ContentType),
				ModTime:     aws.TimeValue(resp.LastModified),
				Size:        getSize(aws.Int64Value(resp.ContentLength), aws.StringValue(resp.ContentRange)),
			},
			raw: resp,
		}, nil
	}
}

// etagToMD5 processes an ETag header and returns an MD5 hash if possible.
// S3's ETag header is sometimes a quoted hexstring of the MD5. Other times,
// notably when the object was uploaded in multiple parts, it is not.
// We do the best we can.
// Some links about ETag:
// https://docs.aws.amazon.com/AmazonS3/latest/API/RESTCommonResponseHeaders.html
// https://github.com/aws/aws-sdk-net/issues/815
// https://teppen.io/2018/06/23/aws_s3_etags/
func eTagToMD5(etag *string) []byte {
	if etag == nil {
		// No header at all.
		return nil
	}
	// Strip the expected leading and trailing quotes.
	quoted := *etag
	if len(quoted) < 2 || quoted[0] != '"' || quoted[len(quoted)-1] != '"' {
		return nil
	}
	unquoted := quoted[1 : len(quoted)-1]
	// Un-hex; we return nil on error. In particular, we'll get an error here
	// for multi-part uploaded blobs, whose ETag will contain a "-" and so will
	// never be a legal hex encoding.
	md5, err := hex.DecodeString(unquoted)
	if err != nil {
		return nil
	}
	return md5
}

func getSize(contentLength int64, contentRange string) int64 {
	// Default size to ContentLength, but that's incorrect for partial-length reads,
	// where ContentLength refers to the size of the returned Body, not the entire
	// size of the blob. ContentRange has the full size.
	size := contentLength
	if contentRange != "" {
		// Sample: bytes 10-14/27 (where 27 is the full size).
		parts := strings.Split(contentRange, "/")
		if len(parts) == 2 {
			if i, err := strconv.ParseInt(parts[1], 10, 64); err == nil {
				size = i
			}
		}
	}
	return size
}

// escapeKey does all required escaping for UTF-8 strings to work with S3.
func escapeKey(key string) string {
	return escape.HexEscape(key, func(r []rune, i int) bool {
		c := r[i]
		switch {
		// S3 doesn't handle these characters (determined via experimentation).
		case c < 32:
			return true
		// For "../", escape the trailing slash.
		case i > 1 && c == '/' && r[i-1] == '.' && r[i-2] == '.':
			return true
		// Escape \.
		case c == '\\':
			return true
		}
		return false
	})
}

// unescapeKey reverses escapeKey.
func unescapeKey(key string) string {
	return escape.HexUnescape(key)
}

// NewTypedWriter implements driver.NewTypedWriter.
func (b *bucket) NewTypedWriter(ctx context.Context, key, contentType string, opts *driver.WriterOptions) (driver.Writer, error) {
	key = escapeKey(key)
	if b.useV2 {
		uploaderV2 := s3managerv2.NewUploader(b.clientV2, func(u *s3managerv2.Uploader) {
			if opts.BufferSize != 0 {
				u.PartSize = int64(opts.BufferSize)
			}
			if opts.MaxConcurrency != 0 {
				u.Concurrency = opts.MaxConcurrency
			}
		})
		md := make(map[string]string, len(opts.Metadata))
		for k, v := range opts.Metadata {
			// See the package comments for more details on escaping of metadata
			// keys & values.
			k = escape.HexEscape(url.PathEscape(k), func(runes []rune, i int) bool {
				c := runes[i]
				return c == '@' || c == ':' || c == '='
			})
			md[k] = url.PathEscape(v)
		}
		reqV2 := &s3v2.PutObjectInput{
			Bucket:      aws.String(b.name),
			ContentType: aws.String(contentType),
			Key:         aws.String(key),
			Metadata:    md,
		}
		if opts.CacheControl != "" {
			reqV2.CacheControl = aws.String(opts.CacheControl)
		}
		if opts.ContentDisposition != "" {
			reqV2.ContentDisposition = aws.String(opts.ContentDisposition)
		}
		if opts.ContentEncoding != "" {
			reqV2.ContentEncoding = aws.String(opts.ContentEncoding)
		}
		if opts.ContentLanguage != "" {
			reqV2.ContentLanguage = aws.String(opts.ContentLanguage)
		}
		if len(opts.ContentMD5) > 0 {
			reqV2.ContentMD5 = aws.String(base64.StdEncoding.EncodeToString(opts.ContentMD5))
		}
		if b.encryptionType != "" {
			reqV2.ServerSideEncryption = b.encryptionType
		}
		if b.kmsKeyId != "" {
			reqV2.SSEKMSKeyId = aws.String(b.kmsKeyId)
		}
		if opts.BeforeWrite != nil {
			asFunc := func(i interface{}) bool {
				// Note that since the Go CDK Blob
				// abstraction does not expose AWS's
				// Uploader concept, there does not
				// appear to be any utility in
				// exposing the options list to the v2
				// Uploader's Upload() method.
				// Instead, applications can
				// manipulate the exposed *Uploader
				// directly, including by setting
				// ClientOptions if needed.
				if p, ok := i.(**s3managerv2.Uploader); ok {
					*p = uploaderV2
					return true
				}
				if p, ok := i.(**s3v2.PutObjectInput); ok {
					*p = reqV2
					return true
				}
				return false
			}
			if err := opts.BeforeWrite(asFunc); err != nil {
				return nil, err
			}
		}
		return &writer{
			ctx:        ctx,
			useV2:      true,
			uploaderV2: uploaderV2,
			reqV2:      reqV2,
			donec:      make(chan struct{}),
		}, nil
	} else {
		uploader := s3manager.NewUploaderWithClient(b.client, func(u *s3manager.Uploader) {
			if opts.BufferSize != 0 {
				u.PartSize = int64(opts.BufferSize)
			}
			if opts.MaxConcurrency != 0 {
				u.Concurrency = opts.MaxConcurrency
			}
		})
		md := make(map[string]*string, len(opts.Metadata))
		for k, v := range opts.Metadata {
			// See the package comments for more details on escaping of metadata
			// keys & values.
			k = escape.HexEscape(url.PathEscape(k), func(runes []rune, i int) bool {
				c := runes[i]
				return c == '@' || c == ':' || c == '='
			})
			md[k] = aws.String(url.PathEscape(v))
		}
		req := &s3manager.UploadInput{
			Bucket:      aws.String(b.name),
			ContentType: aws.String(contentType),
			Key:         aws.String(key),
			Metadata:    md,
		}
		if opts.CacheControl != "" {
			req.CacheControl = aws.String(opts.CacheControl)
		}
		if opts.ContentDisposition != "" {
			req.ContentDisposition = aws.String(opts.ContentDisposition)
		}
		if opts.ContentEncoding != "" {
			req.ContentEncoding = aws.String(opts.ContentEncoding)
		}
		if opts.ContentLanguage != "" {
			req.ContentLanguage = aws.String(opts.ContentLanguage)
		}
		if len(opts.ContentMD5) > 0 {
			req.ContentMD5 = aws.String(base64.StdEncoding.EncodeToString(opts.ContentMD5))
		}
		if b.encryptionType != "" {
			req.ServerSideEncryption = aws.String(string(b.encryptionType))
		}
		if b.kmsKeyId != "" {
			req.SSEKMSKeyId = aws.String(b.kmsKeyId)
		}
		if opts.BeforeWrite != nil {
			asFunc := func(i interface{}) bool {
				pu, ok := i.(**s3manager.Uploader)
				if ok {
					*pu = uploader
					return true
				}
				pui, ok := i.(**s3manager.UploadInput)
				if ok {
					*pui = req
					return true
				}
				return false
			}
			if err := opts.BeforeWrite(asFunc); err != nil {
				return nil, err
			}
		}
		return &writer{
			ctx:      ctx,
			uploader: uploader,
			req:      req,
			donec:    make(chan struct{}),
		}, nil
	}
}

// Copy implements driver.Copy.
func (b *bucket) Copy(ctx context.Context, dstKey, srcKey string, opts *driver.CopyOptions) error {
	dstKey = escapeKey(dstKey)
	srcKey = escapeKey(srcKey)
	srcKeyWithBucketEscaped := url.QueryEscape(b.name + "/" + srcKey)
	if b.useV2 {
		input := &s3v2.CopyObjectInput{
			Bucket:     aws.String(b.name),
			CopySource: aws.String(srcKeyWithBucketEscaped),
			Key:        aws.String(dstKey),
		}
		if b.encryptionType != "" {
			input.ServerSideEncryption = b.encryptionType
		}
		if b.kmsKeyId != "" {
			input.SSEKMSKeyId = aws.String(b.kmsKeyId)
		}
		if opts.BeforeCopy != nil {
			asFunc := func(i interface{}) bool {
				switch v := i.(type) {
				case **s3v2.CopyObjectInput:
					*v = input
					return true
				}
				return false
			}
			if err := opts.BeforeCopy(asFunc); err != nil {
				return err
			}
		}
		_, err := b.clientV2.CopyObject(ctx, input)
		return err
	} else {
		input := &s3.CopyObjectInput{
			Bucket:     aws.String(b.name),
			CopySource: aws.String(srcKeyWithBucketEscaped),
			Key:        aws.String(dstKey),
		}
		if b.encryptionType != "" {
			input.ServerSideEncryption = aws.String(string(b.encryptionType))
		}
		if b.kmsKeyId != "" {
			input.SSEKMSKeyId = aws.String(b.kmsKeyId)
		}
		if opts.BeforeCopy != nil {
			asFunc := func(i interface{}) bool {
				switch v := i.(type) {
				case **s3.CopyObjectInput:
					*v = input
					return true
				}
				return false
			}
			if err := opts.BeforeCopy(asFunc); err != nil {
				return err
			}
		}
		_, err := b.client.CopyObjectWithContext(ctx, input)
		return err
	}
}

// Delete implements driver.Delete.
func (b *bucket) Delete(ctx context.Context, key string) error {
	if _, err := b.Attributes(ctx, key); err != nil {
		return err
	}
	key = escapeKey(key)
	if b.useV2 {
		input := &s3v2.DeleteObjectInput{
			Bucket: aws.String(b.name),
			Key:    aws.String(key),
		}
		_, err := b.clientV2.DeleteObject(ctx, input)
		return err
	} else {
		input := &s3.DeleteObjectInput{
			Bucket: aws.String(b.name),
			Key:    aws.String(key),
		}
		_, err := b.client.DeleteObjectWithContext(ctx, input)
		return err
	}
}

func (b *bucket) SignedURL(ctx context.Context, key string, opts *driver.SignedURLOptions) (string, error) {
	key = escapeKey(key)
	var req *request.Request
	switch opts.Method {
	case http.MethodGet:
		if b.useV2 {
			in := &s3v2.GetObjectInput{
				Bucket: aws.String(b.name),
				Key:    aws.String(key),
			}
			if opts.BeforeSign != nil {
				asFunc := func(i interface{}) bool {
					v, ok := i.(**s3v2.GetObjectInput)
					if ok {
						*v = in
					}
					return ok
				}
				if err := opts.BeforeSign(asFunc); err != nil {
					return "", err
				}
			}
			p, err := s3v2.NewPresignClient(b.clientV2, s3v2.WithPresignExpires(opts.Expiry)).PresignGetObject(ctx, in)
			if err != nil {
				return "", err
			}
			return p.URL, nil
		} else {
			in := &s3.GetObjectInput{
				Bucket: aws.String(b.name),
				Key:    aws.String(key),
			}
			if opts.BeforeSign != nil {
				asFunc := func(i interface{}) bool {
					v, ok := i.(**s3.GetObjectInput)
					if ok {
						*v = in
					}
					return ok
				}
				if err := opts.BeforeSign(asFunc); err != nil {
					return "", err
				}
			}
			req, _ = b.client.GetObjectRequest(in)
			// fall through with req
		}
	case http.MethodPut:
		if b.useV2 {
			in := &s3v2.PutObjectInput{
				Bucket: aws.String(b.name),
				Key:    aws.String(key),
			}
			if opts.EnforceAbsentContentType || opts.ContentType != "" {
				// https://github.com/aws/aws-sdk-go-v2/issues/1475
				return "", gcerr.New(gcerr.Unimplemented, nil, 1, "s3blob: AWS SDK v2 does not supported enforcing ContentType in SignedURLs for PUT")
			}
			if opts.BeforeSign != nil {
				asFunc := func(i interface{}) bool {
					v, ok := i.(**s3v2.PutObjectInput)
					if ok {
						*v = in
					}
					return ok
				}
				if err := opts.BeforeSign(asFunc); err != nil {
					return "", err
				}
			}
			p, err := s3v2.NewPresignClient(b.clientV2, s3v2.WithPresignExpires(opts.Expiry)).PresignPutObject(ctx, in)
			if err != nil {
				return "", err
			}
			return p.URL, nil
		} else {
			in := &s3.PutObjectInput{
				Bucket: aws.String(b.name),
				Key:    aws.String(key),
			}
			if opts.EnforceAbsentContentType || opts.ContentType != "" {
				in.ContentType = aws.String(opts.ContentType)
			}
			if opts.BeforeSign != nil {
				asFunc := func(i interface{}) bool {
					v, ok := i.(**s3.PutObjectInput)
					if ok {
						*v = in
					}
					return ok
				}
				if err := opts.BeforeSign(asFunc); err != nil {
					return "", err
				}
			}
			req, _ = b.client.PutObjectRequest(in)
			// fall through with req
		}
	case http.MethodDelete:
		if b.useV2 {
			// https://github.com/aws/aws-sdk-java-v2/issues/2520
			return "", gcerr.New(gcerr.Unimplemented, nil, 1, "s3blob: AWS SDK v2 does not support SignedURL for DELETE")
		}
		in := &s3.DeleteObjectInput{
			Bucket: aws.String(b.name),
			Key:    aws.String(key),
		}
		if opts.BeforeSign != nil {
			asFunc := func(i interface{}) bool {
				v, ok := i.(**s3.DeleteObjectInput)
				if ok {
					*v = in
				}
				return ok
			}
			if err := opts.BeforeSign(asFunc); err != nil {
				return "", err
			}
		}
		req, _ = b.client.DeleteObjectRequest(in)
	default:
		return "", fmt.Errorf("unsupported Method %q", opts.Method)
	}
	return req.Presign(opts.Expiry)
}
