From 26824e043419025cd1cab6a960bfc3355f92a29a Mon Sep 17 00:00:00 2001
From: Henrique Dias <hacdias@gmail.com>
Date: Thu, 1 Jun 2023 13:39:18 +0200
Subject: [PATCH] feat: add last segment to content disposition

---
 gateway/handler_car.go | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/gateway/handler_car.go b/gateway/handler_car.go
index 78761b5a6..a9df55dd2 100644
--- a/gateway/handler_car.go
+++ b/gateway/handler_car.go
@@ -46,7 +46,7 @@ func (i *handler) serveCAR(ctx context.Context, w http.ResponseWriter, r *http.R
 		return false
 	}
 
-	rootCid, err := getCarRootCid(imPath)
+	rootCid, lastSegment, err := getCarRootCidAndLastSegment(imPath)
 	if err != nil {
 		i.webError(w, r, err, http.StatusInternalServerError)
 		return false
@@ -59,7 +59,11 @@ func (i *handler) serveCAR(ctx context.Context, w http.ResponseWriter, r *http.R
 	if urlFilename := r.URL.Query().Get("filename"); urlFilename != "" {
 		name = urlFilename
 	} else {
-		name = rootCid.String() + ".car"
+		name = rootCid.String()
+		if lastSegment != "" {
+			name += "_" + lastSegment
+		}
+		name += ".car"
 	}
 	setContentDispositionHeader(w, name, "attachment")
 
@@ -177,19 +181,25 @@ func rangeStrToByteRange(rangeStr string) (DagEntityByteRange, error) {
 	}, nil
 }
 
-func getCarRootCid(imPath ImmutablePath) (cid.Cid, error) {
+func getCarRootCidAndLastSegment(imPath ImmutablePath) (cid.Cid, string, error) {
 	imPathStr := imPath.String()
 	if !strings.HasPrefix(imPathStr, "/ipfs/") {
-		return cid.Undef, fmt.Errorf("path does not have /ipfs/ prefix")
+		return cid.Undef, "", fmt.Errorf("path does not have /ipfs/ prefix")
 	}
 
-	firstSegment, _, _ := strings.Cut(imPathStr[6:], "/")
+	firstSegment, remainingSegments, _ := strings.Cut(imPathStr[6:], "/")
 	rootCid, err := cid.Decode(firstSegment)
 	if err != nil {
-		return cid.Undef, err
+		return cid.Undef, "", err
+	}
+
+	// Almost like path.Base(remainingSegments), but without special case for empty strings.
+	lastSegment := strings.TrimRight(remainingSegments, "/")
+	if i := strings.LastIndex(lastSegment, "/"); i >= 0 {
+		lastSegment = lastSegment[i+1:]
 	}
 
-	return rootCid, err
+	return rootCid, lastSegment, err
 }
 
 func getCarEtag(r *http.Request, imPath ImmutablePath, params CarParams, rootCid cid.Cid) string {