From 5adc98258726b92a5d5632892b51c7795682f54c Mon Sep 17 00:00:00 2001
From: David Zbarsky <david.zbarsky@airtable.com>
Date: Wed, 18 Sep 2024 20:08:58 -0400
Subject: [PATCH] Support metadata

---
 services/s3/handler.go | 26 +++++++++++++++++++++++---
 services/s3/s3.go      |  4 ++++
 services/s3/types.go   |  4 ++++
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/services/s3/handler.go b/services/s3/handler.go
index 83c3576..c4339f1 100644
--- a/services/s3/handler.go
+++ b/services/s3/handler.go
@@ -74,6 +74,7 @@ func NewHandler(logger *slog.Logger, s3 *S3) func(w http.ResponseWriter, r *http
 					ServerSideEncryption: r.Form.Get("x-amz-server-side-encryption"),
 					ContentType:          r.Form.Get("Content-Type"),
 					Data:                 f,
+					Metadata:             extractMetadata(r.Header),
 				}
 				logger.Debug("Parsed input", "method", "PutObject", "input", input)
 				output, awserr := s3.PutObject(input)
@@ -128,7 +129,11 @@ func NewHandler(logger *slog.Logger, s3 *S3) func(w http.ResponseWriter, r *http
 				if r.Header.Get("x-amz-copy-source") != "" {
 					handle(w, r, logger.With("method", "CopyObject"), s3.CopyObject)
 				} else {
-					handle(w, r, logger.With("method", "PutObject"), s3.PutObject)
+					handle(w, r, logger.With("method", "PutObject"),
+						func(input PutObjectInput) (*PutObjectOutput, *awserrors.Error) {
+							input.Metadata = extractMetadata(r.Header)
+							return s3.PutObject(input)
+						})
 				}
 			case http.MethodDelete:
 				handle(w, r, logger.With("method", "DeleteObject"), s3.DeleteObject)
@@ -140,6 +145,16 @@ func NewHandler(logger *slog.Logger, s3 *S3) func(w http.ResponseWriter, r *http
 	}
 }
 
+func extractMetadata(header http.Header) map[string]string {
+	metadata := make(map[string]string)
+	for k := range header {
+		if strings.HasPrefix(strings.ToLower(k), "x-amz-meta-") {
+			metadata[k] = header.Get(k)
+		}
+	}
+	return metadata
+}
+
 func handle[Input any, Output any](
 	w http.ResponseWriter,
 	r *http.Request,
@@ -238,13 +253,18 @@ func marshal(w http.ResponseWriter, output any, awserr *awserrors.Error) {
 	v := reflect.ValueOf(output).Elem()
 	ty := v.Type()
 	for i := 0; i < ty.NumField(); i++ {
-		tag := ty.Field(i).Tag.Get("s3")
+		field := ty.Field(i)
+		tag := field.Tag.Get("s3")
 		if tag == "body" {
 			reflect.ValueOf(&body).Elem().Set(v.Field(i))
 		} else if tag == "http-status" {
 			httpStatus = int(v.Field(i).Int())
+		} else if tag == "metadata-headers" {
+			for _, mapKey := range v.Field(i).MapKeys() {
+				mapValue := v.Field(i).MapIndex(mapKey)
+				w.Header().Set(mapKey.String(), mapValue.String())
+			}
 		} else if h, ok := strings.CutPrefix(tag, "header:"); ok {
-			field := ty.Field(i)
 			switch field.Type.Kind() {
 			case reflect.Int, reflect.Int64:
 				w.Header().Set(h, strconv.Itoa(int(v.Field(i).Int())))
diff --git a/services/s3/s3.go b/services/s3/s3.go
index 5833f9e..207b018 100644
--- a/services/s3/s3.go
+++ b/services/s3/s3.go
@@ -30,6 +30,8 @@ type Object struct {
 	MD5  []byte
 	ETag string
 
+	Metadata map[string]string
+
 	ContentType   string
 	ContentLength int64
 	Parts         []Part
@@ -392,6 +394,7 @@ func (s *S3) getObject(input GetObjectInput, includeBody bool) (*GetObjectOutput
 		SSECustomerAlgorithm: object.SSECustomerAlgorithm,
 		SSECustomerKey:       object.SSECustomerKey,
 		SSEKMSKeyId:          object.SSEKMSKeyId,
+		Metadata:             object.Metadata,
 		// Bafflingly, This format is expected here.
 		LastModified: time.Now().UTC().Format(timeFormat),
 		HttpStatus:   http.StatusOK,
@@ -482,6 +485,7 @@ func (s *S3) PutObject(input PutObjectInput) (*PutObjectOutput, *awserrors.Error
 		ContentType:   input.ContentType,
 		ContentLength: contentLength,
 
+		Metadata:             input.Metadata,
 		Tagging:              input.Tagging,
 		ServerSideEncryption: input.ServerSideEncryption,
 		SSEKMSKeyId:          input.SSEKMSKeyId,
diff --git a/services/s3/types.go b/services/s3/types.go
index fbbe17a..9777d32 100644
--- a/services/s3/types.go
+++ b/services/s3/types.go
@@ -118,6 +118,8 @@ type GetObjectOutput struct {
 	SSECustomerAlgorithm string `s3:"header:x-amz-server-side-encryption-customer-algorithm"`
 	SSECustomerKey       string `s3:"header:x-amz-server-side-encryption-customer-key"`
 	LastModified         string `s3:"header:Last-Modified"`
+	// Note: Metadata is handled specially
+	Metadata map[string]string `s3:"metadata-headers"`
 	// TODO: md5
 	SSEKMSKeyId string `s3:"header:x-amz-server-side-encryption-aws-kms-key-id"`
 	//PartsCount    int    `s3:"header:x-amz-mp-parts-count"`
@@ -135,6 +137,8 @@ type PutObjectInput struct {
 	SSEKMSKeyId             string    `s3:"header:x-amz-server-side-encryption-aws-kms-key-id"`
 	SSEKMSEncryptionContext string    `s3:"header:x-amz-server-side-encryption-context"`
 	SSECustomerAlgorithm    string    `s3:"header:x-amz-server-side-encryption-customer-algorithm"`
+	// Note: Metadata is handled specially
+	Metadata map[string]string
 	// TODO: md5 check
 	SSECustomerKey   string `s3:"header:x-amz-server-side-encryption-customer-key"`
 	Tagging          string `s3:"header:x-amz-tagging"`