package api

import (
	"context"
	"net/http"
	"sync"

	"github.com/google/uuid"
	"github.com/gorilla/mux"
	"github.com/nspcc-dev/neofs-s3-gw/api/auth"
	"github.com/nspcc-dev/neofs-s3-gw/api/metrics"
	"go.uber.org/zap"
	"google.golang.org/grpc/metadata"
)

type (
	// Handler is an S3 API handler interface.
	Handler interface {
		HeadObjectHandler(http.ResponseWriter, *http.Request)
		CopyObjectPartHandler(http.ResponseWriter, *http.Request)
		PutObjectPartHandler(http.ResponseWriter, *http.Request)
		ListObjectPartsHandler(http.ResponseWriter, *http.Request)
		CompleteMultipartUploadHandler(http.ResponseWriter, *http.Request)
		NewMultipartUploadHandler(http.ResponseWriter, *http.Request)
		AbortMultipartUploadHandler(http.ResponseWriter, *http.Request)
		GetObjectACLHandler(http.ResponseWriter, *http.Request)
		PutObjectACLHandler(http.ResponseWriter, *http.Request)
		GetObjectTaggingHandler(http.ResponseWriter, *http.Request)
		PutObjectTaggingHandler(http.ResponseWriter, *http.Request)
		DeleteObjectTaggingHandler(http.ResponseWriter, *http.Request)
		SelectObjectContentHandler(http.ResponseWriter, *http.Request)
		GetObjectRetentionHandler(http.ResponseWriter, *http.Request)
		GetObjectLegalHoldHandler(http.ResponseWriter, *http.Request)
		GetObjectHandler(http.ResponseWriter, *http.Request)
		CopyObjectHandler(http.ResponseWriter, *http.Request)
		PutObjectRetentionHandler(http.ResponseWriter, *http.Request)
		PutObjectLegalHoldHandler(http.ResponseWriter, *http.Request)
		PutObjectHandler(http.ResponseWriter, *http.Request)
		DeleteObjectHandler(http.ResponseWriter, *http.Request)
		GetBucketLocationHandler(http.ResponseWriter, *http.Request)
		GetBucketPolicyHandler(http.ResponseWriter, *http.Request)
		GetBucketLifecycleHandler(http.ResponseWriter, *http.Request)
		GetBucketEncryptionHandler(http.ResponseWriter, *http.Request)
		GetBucketACLHandler(http.ResponseWriter, *http.Request)
		PutBucketACLHandler(http.ResponseWriter, *http.Request)
		GetBucketCorsHandler(http.ResponseWriter, *http.Request)
		GetBucketWebsiteHandler(http.ResponseWriter, *http.Request)
		GetBucketAccelerateHandler(http.ResponseWriter, *http.Request)
		GetBucketRequestPaymentHandler(http.ResponseWriter, *http.Request)
		GetBucketLoggingHandler(http.ResponseWriter, *http.Request)
		GetBucketReplicationHandler(http.ResponseWriter, *http.Request)
		GetBucketTaggingHandler(http.ResponseWriter, *http.Request)
		DeleteBucketWebsiteHandler(http.ResponseWriter, *http.Request)
		DeleteBucketTaggingHandler(http.ResponseWriter, *http.Request)
		GetBucketObjectLockConfigHandler(http.ResponseWriter, *http.Request)
		GetBucketVersioningHandler(http.ResponseWriter, *http.Request)
		GetBucketNotificationHandler(http.ResponseWriter, *http.Request)
		ListenBucketNotificationHandler(http.ResponseWriter, *http.Request)
		ListMultipartUploadsHandler(http.ResponseWriter, *http.Request)
		ListObjectsV2MHandler(http.ResponseWriter, *http.Request)
		ListObjectsV2Handler(http.ResponseWriter, *http.Request)
		ListBucketObjectVersionsHandler(http.ResponseWriter, *http.Request)
		ListObjectsV1Handler(http.ResponseWriter, *http.Request)
		PutBucketLifecycleHandler(http.ResponseWriter, *http.Request)
		PutBucketEncryptionHandler(http.ResponseWriter, *http.Request)
		PutBucketPolicyHandler(http.ResponseWriter, *http.Request)
		PutBucketObjectLockConfigHandler(http.ResponseWriter, *http.Request)
		PutBucketTaggingHandler(http.ResponseWriter, *http.Request)
		PutBucketVersioningHandler(http.ResponseWriter, *http.Request)
		PutBucketNotificationHandler(http.ResponseWriter, *http.Request)
		CreateBucketHandler(http.ResponseWriter, *http.Request)
		HeadBucketHandler(http.ResponseWriter, *http.Request)
		PostPolicyBucketHandler(http.ResponseWriter, *http.Request)
		DeleteMultipleObjectsHandler(http.ResponseWriter, *http.Request)
		DeleteBucketPolicyHandler(http.ResponseWriter, *http.Request)
		DeleteBucketLifecycleHandler(http.ResponseWriter, *http.Request)
		DeleteBucketEncryptionHandler(http.ResponseWriter, *http.Request)
		DeleteBucketHandler(http.ResponseWriter, *http.Request)
		ListBucketsHandler(http.ResponseWriter, *http.Request)
	}

	// mimeType represents various MIME type used API responses.
	mimeType string

	logResponseWriter struct {
		sync.Once
		http.ResponseWriter

		statusCode int
	}
)

const (
	// SlashSeparator - slash separator.
	SlashSeparator = "/"

	// MimeNone means no response type.
	MimeNone mimeType = ""

	// MimeXML means response type is XML.
	MimeXML mimeType = "application/xml"
)

var _ = logErrorResponse

func (lrw *logResponseWriter) WriteHeader(code int) {
	lrw.Do(func() {
		lrw.statusCode = code
		lrw.ResponseWriter.WriteHeader(code)
	})
}

func setRequestID(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// generate random UUIDv4
		id, _ := uuid.NewRandom()

		// set request id into response header
		w.Header().Set(hdrAmzRequestID, id.String())

		// set request id into gRPC meta header
		r = r.WithContext(metadata.AppendToOutgoingContext(
			r.Context(), hdrAmzRequestID, id.String(),
		))

		// set request info into context
		r = r.WithContext(prepareContext(w, r))

		// continue execution
		h.ServeHTTP(w, r)
	})
}

func logErrorResponse(l *zap.Logger) mux.MiddlewareFunc {
	return func(h http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			lw := &logResponseWriter{ResponseWriter: w}

			// pass execution:
			h.ServeHTTP(lw, r)

			// Ignore <300 status codes
			if lw.statusCode >= http.StatusMultipleChoices {
				l.Error("something went wrong",
					zap.Int("status", lw.statusCode),
					zap.String("request_id", GetRequestID(r.Context())),
					zap.String("method", mux.CurrentRoute(r).GetName()),
					zap.String("description", http.StatusText(lw.statusCode)))

				return
			}

			l.Info("call method",
				zap.Int("status", lw.statusCode),
				zap.String("request_id", GetRequestID(r.Context())),
				zap.String("method", mux.CurrentRoute(r).GetName()),
				zap.String("description", http.StatusText(lw.statusCode)))
		})
	}
}

// GetRequestID returns request ID from response writer or context.
func GetRequestID(v interface{}) string {
	switch t := v.(type) {
	case context.Context:
		return GetReqInfo(t).RequestID
	case http.ResponseWriter:
		return t.Header().Get(hdrAmzRequestID)
	default:
		panic("unknown type")
	}
}

// Attach adds S3 API handlers from h to r for domains with m client limit using
// center authentication and log logger.
func Attach(r *mux.Router, domains []string, m MaxClients, h Handler, center auth.Center, log *zap.Logger) {
	api := r.PathPrefix(SlashSeparator).Subrouter()

	api.Use(
		// -- prepare request
		setRequestID,

		// -- logging error requests
		logErrorResponse(log),
	)

	// Attach user authentication for all S3 routes.
	AttachUserAuth(api, center, log)

	buckets := make([]*mux.Router, 0, len(domains)+1)
	buckets = append(buckets, api.PathPrefix("/{bucket}").Subrouter())

	for _, domain := range domains {
		buckets = append(buckets, api.Host("{bucket:.+}."+domain).Subrouter())
	}

	for _, bucket := range buckets {
		// Object operations
		// HeadObject
		bucket.Methods(http.MethodHead).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("headobject", h.HeadObjectHandler))).Name("HeadObject")
		// CopyObjectPart
		bucket.Methods(http.MethodPut).Path("/{object:.+}").HeadersRegexp(hdrAmzCopySource, ".*?(\\/|%2F).*?").HandlerFunc(m.Handle(metrics.APIStats("copyobjectpart", h.CopyObjectPartHandler))).Queries("partNumber", "{partNumber:[0-9]+}", "uploadId", "{uploadId:.*}").
			Name("CopyObjectPart")
		// PutObjectPart
		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("putobjectpart", h.PutObjectPartHandler))).Queries("partNumber", "{partNumber:[0-9]+}", "uploadId", "{uploadId:.*}").
			Name("PutObjectObject")
		// ListObjectParts
		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("listobjectparts", h.ListObjectPartsHandler))).Queries("uploadId", "{uploadId:.*}").
			Name("ListObjectParts")
		// CompleteMultipartUpload
		bucket.Methods(http.MethodPost).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("completemutipartupload", h.CompleteMultipartUploadHandler))).Queries("uploadId", "{uploadId:.*}").
			Name("CompleteMultipartUpload")
		// NewMultipartUpload
		bucket.Methods(http.MethodPost).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("newmultipartupload", h.NewMultipartUploadHandler))).Queries("uploads", "").
			Name("NewMultipartUpload")
		// AbortMultipartUpload
		bucket.Methods(http.MethodDelete).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("abortmultipartupload", h.AbortMultipartUploadHandler))).Queries("uploadId", "{uploadId:.*}").
			Name("AbortMultipartUpload")
		// GetObjectACL - this is a dummy call.
		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("getobjectacl", h.GetObjectACLHandler))).Queries("acl", "").
			Name("GetObjectACL")
		// PutObjectACL - this is a dummy call.
		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("putobjectacl", h.PutObjectACLHandler))).Queries("acl", "").
			Name("PutObjectACL")
		// GetObjectTagging
		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("getobjecttagging", h.GetObjectTaggingHandler))).Queries("tagging", "").
			Name("GetObjectTagging")
		// PutObjectTagging
		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("putobjecttagging", h.PutObjectTaggingHandler))).Queries("tagging", "").
			Name("PutObjectTagging")
		// DeleteObjectTagging
		bucket.Methods(http.MethodDelete).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("deleteobjecttagging", h.DeleteObjectTaggingHandler))).Queries("tagging", "").
			Name("DeleteObjectTagging")
		// SelectObjectContent
		bucket.Methods(http.MethodPost).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("selectobjectcontent", h.SelectObjectContentHandler))).Queries("select", "").Queries("select-type", "2").
			Name("SelectObjectContent")
		// GetObjectRetention
		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("getobjectretention", h.GetObjectRetentionHandler))).Queries("retention", "").
			Name("GetObjectRetention")
		// GetObjectLegalHold
		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("getobjectlegalhold", h.GetObjectLegalHoldHandler))).Queries("legal-hold", "").
			Name("GetObjectLegalHold")
		// GetObject
		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("getobject", h.GetObjectHandler))).
			Name("GetObject")
		// CopyObject
		bucket.Methods(http.MethodPut).Path("/{object:.+}").HeadersRegexp(hdrAmzCopySource, ".*?(\\/|%2F).*?").HandlerFunc(m.Handle(metrics.APIStats("copyobject", h.CopyObjectHandler))).
			Name("CopyObject")
		// PutObjectRetention
		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("putobjectretention", h.PutObjectRetentionHandler))).Queries("retention", "").
			Name("PutObjectRetention")
		// PutObjectLegalHold
		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("putobjectlegalhold", h.PutObjectLegalHoldHandler))).Queries("legal-hold", "").
			Name("PutObjectLegalHold")

		// PutObject
		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("putobject", h.PutObjectHandler))).
			Name("PutObject")
		// DeleteObject
		bucket.Methods(http.MethodDelete).Path("/{object:.+}").HandlerFunc(
			m.Handle(metrics.APIStats("deleteobject", h.DeleteObjectHandler))).
			Name("DeleteObject")

		// Bucket operations
		// GetBucketLocation
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketlocation", h.GetBucketLocationHandler))).Queries("location", "").
			Name("GetBucketLocation")
		// GetBucketPolicy
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketpolicy", h.GetBucketPolicyHandler))).Queries("policy", "").
			Name("GetBucketPolicy")
		// GetBucketLifecycle
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketlifecycle", h.GetBucketLifecycleHandler))).Queries("lifecycle", "").
			Name("GetBucketLifecycle")
		// GetBucketEncryption
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketencryption", h.GetBucketEncryptionHandler))).Queries("encryption", "").
			Name("GetBucketEncryption")

		// Dummy Bucket Calls
		// GetBucketACL -- this is a dummy call.
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketacl", h.GetBucketACLHandler))).Queries("acl", "").
			Name("GetBucketACL")
		// PutBucketACL -- this is a dummy call.
		bucket.Methods(http.MethodPut).HandlerFunc(
			m.Handle(metrics.APIStats("putbucketacl", h.PutBucketACLHandler))).Queries("acl", "").
			Name("PutBucketACL")
		// GetBucketCors - this is a dummy call.
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketcors", h.GetBucketCorsHandler))).Queries("cors", "").
			Name("GetBucketCors")
		// GetBucketWebsiteHandler - this is a dummy call.
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketwebsite", h.GetBucketWebsiteHandler))).Queries("website", "").
			Name("GetBucketWebsite")
		// GetBucketAccelerateHandler - this is a dummy call.
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketaccelerate", h.GetBucketAccelerateHandler))).Queries("accelerate", "").
			Name("GetBucketAccelerate")
		// GetBucketRequestPaymentHandler - this is a dummy call.
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketrequestpayment", h.GetBucketRequestPaymentHandler))).Queries("requestPayment", "").
			Name("GetBucketRequestPayment")
		// GetBucketLoggingHandler - this is a dummy call.
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketlogging", h.GetBucketLoggingHandler))).Queries("logging", "").
			Name("GetBucketLogging")
		// GetBucketLifecycleHandler - this is a dummy call.
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketlifecycle", h.GetBucketLifecycleHandler))).Queries("lifecycle", "").
			Name("GetBucketLifecycle")
		// GetBucketReplicationHandler - this is a dummy call.
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketreplication", h.GetBucketReplicationHandler))).Queries("replication", "").
			Name("GetBucketReplication")
		// GetBucketTaggingHandler
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbuckettagging", h.GetBucketTaggingHandler))).Queries("tagging", "").
			Name("GetBucketTagging")
		// DeleteBucketWebsiteHandler
		bucket.Methods(http.MethodDelete).HandlerFunc(
			m.Handle(metrics.APIStats("deletebucketwebsite", h.DeleteBucketWebsiteHandler))).Queries("website", "").
			Name("DeleteBucketWebsite")
		// DeleteBucketTaggingHandler
		bucket.Methods(http.MethodDelete).HandlerFunc(
			m.Handle(metrics.APIStats("deletebuckettagging", h.DeleteBucketTaggingHandler))).Queries("tagging", "").
			Name("DeleteBucketTagging")

		// GetBucketObjectLockConfig
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketobjectlockconfiguration", h.GetBucketObjectLockConfigHandler))).Queries("object-lock", "").
			Name("GetBucketObjectLockConfig")
		// GetBucketVersioning
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketversioning", h.GetBucketVersioningHandler))).Queries("versioning", "").
			Name("GetBucketVersioning")
		// GetBucketNotification
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("getbucketnotification", h.GetBucketNotificationHandler))).Queries("notification", "").
			Name("GetBucketNotification")
		// ListenBucketNotification
		bucket.Methods(http.MethodGet).HandlerFunc(metrics.APIStats("listenbucketnotification", h.ListenBucketNotificationHandler)).Queries("events", "{events:.*}").
			Name("ListenBucketNotification")
		// ListMultipartUploads
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("listmultipartuploads", h.ListMultipartUploadsHandler))).Queries("uploads", "").
			Name("ListMultipartUploads")
		// ListObjectsV2M
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("listobjectsv2M", h.ListObjectsV2MHandler))).Queries("list-type", "2", "metadata", "true").
			Name("ListObjectsV2M")
		// ListObjectsV2
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("listobjectsv2", h.ListObjectsV2Handler))).Queries("list-type", "2").
			Name("ListObjectsV2")
		// ListBucketVersions
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("listbucketversions", h.ListBucketObjectVersionsHandler))).Queries("versions", "").
			Name("ListBucketVersions")
		// ListObjectsV1 (Legacy)
		bucket.Methods(http.MethodGet).HandlerFunc(
			m.Handle(metrics.APIStats("listobjectsv1", h.ListObjectsV1Handler))).
			Name("ListObjectsV1")
		// PutBucketLifecycle
		bucket.Methods(http.MethodPut).HandlerFunc(
			m.Handle(metrics.APIStats("putbucketlifecycle", h.PutBucketLifecycleHandler))).Queries("lifecycle", "").
			Name("PutBucketLifecycle")
		// PutBucketEncryption
		bucket.Methods(http.MethodPut).HandlerFunc(
			m.Handle(metrics.APIStats("putbucketencryption", h.PutBucketEncryptionHandler))).Queries("encryption", "").
			Name("PutBucketEncryption")

		// PutBucketPolicy
		bucket.Methods(http.MethodPut).HandlerFunc(
			m.Handle(metrics.APIStats("putbucketpolicy", h.PutBucketPolicyHandler))).Queries("policy", "").
			Name("PutBucketPolicy")

		// PutBucketObjectLockConfig
		bucket.Methods(http.MethodPut).HandlerFunc(
			m.Handle(metrics.APIStats("putbucketobjectlockconfig", h.PutBucketObjectLockConfigHandler))).Queries("object-lock", "").
			Name("PutBucketObjectLockConfig")
		// PutBucketTaggingHandler
		bucket.Methods(http.MethodPut).HandlerFunc(
			m.Handle(metrics.APIStats("putbuckettagging", h.PutBucketTaggingHandler))).Queries("tagging", "").
			Name("PutBucketTagging")
		// PutBucketVersioning
		bucket.Methods(http.MethodPut).HandlerFunc(
			m.Handle(metrics.APIStats("putbucketversioning", h.PutBucketVersioningHandler))).Queries("versioning", "").
			Name("PutBucketVersioning")
		// PutBucketNotification
		bucket.Methods(http.MethodPut).HandlerFunc(
			m.Handle(metrics.APIStats("putbucketnotification", h.PutBucketNotificationHandler))).Queries("notification", "").
			Name("PutBucketNotification")
		// CreateBucket
		bucket.Methods(http.MethodPut).HandlerFunc(
			m.Handle(metrics.APIStats("createbucket", h.CreateBucketHandler))).
			Name("CreateBucket")
		// HeadBucket
		bucket.Methods(http.MethodHead).HandlerFunc(
			m.Handle(metrics.APIStats("headbucket", h.HeadBucketHandler))).
			Name("HeadBucket")
		// PostPolicy
		bucket.Methods(http.MethodPost).HeadersRegexp(hdrContentType, "multipart/form-data*").HandlerFunc(
			m.Handle(metrics.APIStats("postpolicybucket", h.PostPolicyBucketHandler))).
			Name("PostPolicyBucket")
		// DeleteMultipleObjects
		bucket.Methods(http.MethodPost).HandlerFunc(
			m.Handle(metrics.APIStats("deletemultipleobjects", h.DeleteMultipleObjectsHandler))).Queries("delete", "").
			Name("DeleteMultipleObjects")
		// DeleteBucketPolicy
		bucket.Methods(http.MethodDelete).HandlerFunc(
			m.Handle(metrics.APIStats("deletebucketpolicy", h.DeleteBucketPolicyHandler))).Queries("policy", "").
			Name("DeleteBucketPolicy")
		// DeleteBucketLifecycle
		bucket.Methods(http.MethodDelete).HandlerFunc(
			m.Handle(metrics.APIStats("deletebucketlifecycle", h.DeleteBucketLifecycleHandler))).Queries("lifecycle", "").
			Name("DeleteBucketLifecycle")
		// DeleteBucketEncryption
		bucket.Methods(http.MethodDelete).HandlerFunc(
			m.Handle(metrics.APIStats("deletebucketencryption", h.DeleteBucketEncryptionHandler))).Queries("encryption", "").
			Name("DeleteBucketEncryption")
		// DeleteBucket
		bucket.Methods(http.MethodDelete).HandlerFunc(
			m.Handle(metrics.APIStats("deletebucket", h.DeleteBucketHandler))).
			Name("DeleteBucket")
	}
	// Root operation

	// ListBuckets
	api.Methods(http.MethodGet).Path(SlashSeparator).HandlerFunc(
		m.Handle(metrics.APIStats("listbuckets", h.ListBucketsHandler))).
		Name("ListBuckets")

	// S3 browser with signature v4 adds '//' for ListBuckets request, so rather
	// than failing with UnknownAPIRequest we simply handle it for now.
	api.Methods(http.MethodGet).Path(SlashSeparator + SlashSeparator).HandlerFunc(
		m.Handle(metrics.APIStats("listbuckets", h.ListBucketsHandler))).
		Name("ListBuckets")

	// If none of the routes match add default error handler routes
	api.NotFoundHandler = metrics.APIStats("notfound", errorResponseHandler)
	api.MethodNotAllowedHandler = metrics.APIStats("methodnotallowed", errorResponseHandler)
}