Add custom URL prefix for HTTP URLs (#1260)

Co-authored-by: Johannes Pohl <johannes.pohl@badaix.de>

server/etc/snapserver.conf

@@ -24,8 +24,8 @@
 # Number of additional worker threads to use
 # - For values < 0 the number of threads will be 2 (on single and dual cores)
 #   or 4 (for quad and more cores)
-# - 0 will utilize just the processes main thread and might cause audio drops 
-#   in case there are a couple of longer running tasks, such as encoding 
+# - 0 will utilize just the processes main thread and might cause audio drops
+#   in case there are a couple of longer running tasks, such as encoding
 #   multiple audio streams
 #threads = -1
 
@@ -41,7 +41,7 @@
 # if empty, data dir will be
 #  - "/var/lib/snapserver/" when running as daemon
 #  - "$HOME/.config/snapserver/" when not running as daemon
-#datadir = 
+#datadir =
 
 #
 ###############################################################################
@@ -97,9 +97,13 @@ doc_root = /usr/share/snapserver/snapweb
 
 # Hostname or IP under which clients can reach this host
 # used to serve cached cover art
-# use <hostname> as placeholder for your actual host name  
+# use <hostname> as placeholder for your actual host name
 #host = <hostname>
 
+# Optional custom URL prefix for generated URLs where clients can reach
+# cached album art, to e.g. match scheme behind a reverse proxy.
+#url_prefix = https://<hostname>
+
 #
 ###############################################################################
 
@@ -170,7 +174,7 @@ source = pipe:///tmp/snapfifo?name=default
 # Start Snapserver with "--stream:codec=<codec>:?" to get codec specific options
 #codec = flac
 
-# Default source stream read chunk size [ms]. 
+# Default source stream read chunk size [ms].
 # The server will continously read this number of milliseconds from the source into buffer and pass this buffer to the encoder.
 # The encoded buffer is sent to the clients. Some codecs have a higher latency and will need more data, e.g. Flac will need ~26ms chunks
 #chunk_ms = 20
@@ -201,9 +205,9 @@ source = pipe:///tmp/snapfifo?name=default
 
 # log sink [null,system,stdout,stderr,file:<filename>]
 # when left empty: if running as daemon "system" else "stdout"
-#sink = 
+#sink =
 
-# log filter <tag>:<level>[,<tag>:<level>]* 
+# log filter <tag>:<level>[,<tag>:<level>]*
 # with tag = * or <log tag> and level = [trace,debug,info,notice,warning,error,fatal]
 #filter = *:info
 #

server/server_settings.hpp

@@ -73,6 +73,7 @@ struct ServerSettings
         std::vector<std::string> ssl_bind_to_address{{"0.0.0.0"}};
         std::string doc_root{""};
         std::string host{"<hostname>"};
+        std::string url_prefix{""};
     };
 
     struct Tcp

server/snapserver.cpp

@@ -100,6 +100,7 @@ int main(int argc, char* argv[])
                                                                 settings.http.ssl_bind_to_address.front(), &settings.http.ssl_bind_to_address[0]);
         conf.add<Implicit<string>>("", "http.doc_root", "serve a website from the doc_root location", settings.http.doc_root, &settings.http.doc_root);
         conf.add<Value<string>>("", "http.host", "Hostname or IP under which clients can reach this host", settings.http.host, &settings.http.host);
+        conf.add<Value<string>>("", "http.url_prefix", "URL prefix for generating album art URLs", settings.http.url_prefix, &settings.http.url_prefix);
 
         // TCP RPC settings
         conf.add<Value<bool>>("", "tcp.enabled", "enable TCP Json RPC)", settings.tcp.enabled, &settings.tcp.enabled);

server/streamreader/pcm_stream.cpp

@@ -541,7 +541,11 @@ void PcmStream::setProperties(const Properties& properties)
         auto md5 = ImageCache::instance().setImage(getName(), std::move(data), props.metadata->art_data->extension);
 
         std::stringstream url;
-        url << "http://" << server_settings_.http.host << ":" << server_settings_.http.port << "/__image_cache?name=" << md5;
+        if (server_settings_.http.url_prefix == "") {
+            url << "http://" << server_settings_.http.host << ":" << server_settings_.http.port << "/__image_cache?name=" << md5;
+        } else {
+            url << server_settings_.http.url_prefix << "/__image_cache?name=" << md5;
+        }
         props.metadata->art_url = url.str();
     }
     else if (!props.metadata.has_value() || !props.metadata->art_data.has_value())