Add format override

Signed-off-by: Knut Ahlers <knut@ahlers.me>

README.md

@@ -70,10 +70,11 @@ GET   /job/{uuid}/download  Download the resulting archive (You may specify an
                             TAR archive or just the raw PDF.)
 ```
 
-All routes accept the `log-on-error` parameter: If set a PDF download (`Accept` header set to `application/pdf`) will return the log instead of the PDF if no PDF is found.
+Supported query parameters:
-
-Providing `report-urls` parameter to the `POST /jobs` endpoint will not redirect to the wait endpoint but report a JSON object containing the URL paths:
 
+- `format` overrides the `Accept` header detection and choses the output format (`pdf`, `tar`, `zip`) and is accepted on all endpoints
+- `log-on-error` - If set a PDF download (`Accept` header set to `application/pdf` or `format` is chosen) will return the log instead of the PDF if no PDF is found.
+- `report-urls` on the `POST /jobs` endpoint will not redirect to the wait endpoint but report a JSON object containing the URL paths:  
 ```json
 {
   "download": "/job/fb5ee7b8-679a-4bf2-951b-acabaf43b43e/download",

main.go

@@ -88,6 +88,23 @@ func main() {
 	}
 }
 
+func chooseDistribution(r *http.Request) string {
+	if dist := r.URL.Query().Get("format"); dist != "" {
+		return dist
+	}
+
+	switch r.Header.Get("Accept") {
+	case "application/tar", "application/x-tar", "application/x-gtar", "multipart/x-tar", "application/x-compress", "application/x-compressed":
+		return "tar"
+
+	case "application/pdf":
+		return "pdf"
+
+	default:
+		return "zip"
+	}
+}
+
 func downloadAssets(res http.ResponseWriter, r *http.Request) {
 	vars := mux.Vars(r)
 	uid, err := uuid.FromString(vars["uid"])
@@ -102,13 +119,13 @@ func downloadAssets(res http.ResponseWriter, r *http.Request) {
 		filename    string
 	)
 
-	switch r.Header.Get("Accept") {
+	switch dist := chooseDistribution(r); dist {
-	case "application/tar", "application/x-tar", "application/x-gtar", "multipart/x-tar", "application/x-compress", "application/x-compressed":
+	case "tar":
 		contentType = "application/tar"
 		content, err = buildAssetsTAR(uid)
 		filename = uid.String() + ".tar"
 
-	case "application/pdf":
+	case "pdf":
 		contentType = "application/pdf"
 		filename = uid.String() + ".pdf"
 		content, err = getAssetsFile(uid, ".pdf")
@@ -119,9 +136,12 @@ func downloadAssets(res http.ResponseWriter, r *http.Request) {
 			content, err = getAssetsFile(uid, ".log")
 		}
 
-	default:
+	case "zip":
 		content, err = buildAssetsZIP(uid)
 		filename = uid.String() + ".zip"
+
+	default:
+		err = errors.Errorf("unknown distribution %q", dist)
 	}
 
 	if err != nil {