Persist partition functionality

src/StateFile.cxx

@@ -10,13 +10,17 @@
 #include "io/BufferedOutputStream.hxx"
 #include "storage/StorageState.hxx"
 #include "Partition.hxx"
+#include "config/PartitionConfig.hxx"
 #include "Instance.hxx"
 #include "SongLoader.hxx"
 #include "util/Domain.hxx"
 #include "Log.hxx"
+#include "util/StringCompare.hxx"
 
 #include <exception>
 
+#define PARTITION_STATE "partition: "
+
 static constexpr Domain state_file_domain("state_file");
 
 StateFile::StateFile(StateFileConfig &&_config,
@@ -55,14 +59,19 @@ StateFile::IsModified() const noexcept
 inline void
 StateFile::Write(BufferedOutputStream &os)
 {
-	partition.mixer_memento.SaveSoftwareVolumeState(os);
-	audio_output_state_save(os, partition.outputs);
+	for (auto &current_partition : partition.instance.partitions) {
+		if (&current_partition != &partition.instance.partitions.front())
+			os.Fmt(PARTITION_STATE "{}\n",
+			current_partition.name);
+		current_partition.mixer_memento.SaveSoftwareVolumeState(os);
+		audio_output_state_save(os, current_partition.outputs);
+
+		playlist_state_save(os, current_partition.playlist, current_partition.pc);
+	}
 
 #ifdef ENABLE_DATABASE
 	storage_state_save(os, partition.instance);
 #endif
-
-	playlist_state_save(os, partition.playlist, partition.pc);
 }
 
 inline void
@@ -106,13 +115,21 @@ try {
 	const SongLoader song_loader(nullptr, nullptr);
 #endif
 
+	Partition *current_partition = &partition;
+
+	FmtDebug(state_file_domain,
+		 "Starting main loop to read state file (initial partition: '{}')",
+		 current_partition->name);
+
 	const char *line;
 	while ((line = file.ReadLine()) != nullptr) {
-		success = partition.mixer_memento.LoadSoftwareVolumeState(line, partition.outputs) ||
-			audio_output_state_read(line, partition.outputs) ||
+		success = current_partition->mixer_memento.LoadSoftwareVolumeState(line,
+									partition.outputs) ||
+			audio_output_state_read(line, partition.outputs, current_partition) ||
 			playlist_state_restore(config, line, file, song_loader,
-					       partition.playlist,
-					       partition.pc);
+						current_partition->playlist,
+						current_partition->pc) ||
+			PartitionSwitch(line, current_partition);
 #ifdef ENABLE_DATABASE
 		success = success || storage_state_restore(line, file, partition.instance);
 #endif
@@ -140,3 +157,39 @@ StateFile::OnTimeout() noexcept
 {
 	Write();
 }
+
+/**
+ * Attempts to switch the current partition based on a state file line.
+ *
+ * @param line The line from the state file to parse
+ * @param current_partition Reference to pointer that will be updated to point
+ *                          to the target partition
+ * @return true if the line was a partition switch command, false otherwise
+ */
+bool StateFile::PartitionSwitch(const char *line,
+				Partition *&current_partition) noexcept {
+	// Check if this line contains a partition switch command
+	line = StringAfterPrefix(line, PARTITION_STATE);
+	if (line == nullptr)
+		return false;
+
+	// Try to find existing partition
+	Partition *new_partition = partition.instance.FindPartition(line);
+	if (new_partition != nullptr) {
+		current_partition = new_partition;
+		FmtDebug(state_file_domain, "Switched to existing partition '{}'",
+			 current_partition->name);
+		return true;
+	}
+
+	// Partition doesn't exist, create it
+	partition.instance.partitions.emplace_back(partition.instance, line,
+						   PartitionConfig{});
+	current_partition = &partition.instance.partitions.back();
+	current_partition->UpdateEffectiveReplayGainMode();
+
+	FmtDebug(state_file_domain, "Created and switched to partition '{}'",
+		 current_partition->name);
+
+	return true;
+}

src/StateFile.hxx

@@ -63,4 +63,10 @@ private:
 
 	/* callback for #timer_event */
 	void OnTimeout() noexcept;
+
+	/**
+	 * Handle partition lines in the state file
+	 */
+	bool PartitionSwitch(const char *line,
+			     Partition *&current_partition) noexcept;
 };

src/output/State.cxx

@@ -12,15 +12,35 @@
 #include "Log.hxx"
 #include "io/BufferedOutputStream.hxx"
 #include "util/StringCompare.hxx"
+#include "Partition.hxx"
+#include "config/PartitionConfig.hxx"
 
 #include <fmt/format.h>
 
 #include <stdlib.h>
 
 #define AUDIO_DEVICE_STATE "audio_device_state:"
+#define DEFAULT_PARTITION "default"
 
 unsigned audio_output_state_version;
 
+/**
+ * Iterate the instance and save audio output state configuration.
+ *
+ * Writes the name of the audio outputs, the partitions they are assigned to,
+ * and the state of the output.
+ *
+ * Writes a configuration line this format:
+ *   AUDIO_DEVICE_STATE<value>:<device>:<partition>
+ *
+ * Where:
+ *   <value> = 0 (disabled) or 1 (enabled)
+ *   <device> = output device name
+ *
+ * @param os The output stream
+ * @param outputs The outputs assigned to this partition
+ * @return nothing
+ */
 void
 audio_output_state_save(BufferedOutputStream &os,
 			const MultipleOutputs &outputs)
@@ -34,8 +54,25 @@ audio_output_state_save(BufferedOutputStream &os,
 	}
 }
 
+/**
+ * Parse and apply audio output state configuration.
+ *
+ * Reads a configuration line in one of these formats:
+ *   AUDIO_DEVICE_STATE<value>:<device>
+ *   AUDIO_DEVICE_STATE<value>:<device>:<partition>
+ *
+ * Where:
+ *   <value> = 0 (disabled) or 1 (enabled)
+ *   <device> = output device name
+ *   <partition> = optional partition name
+ *
+ * @param line The configuration line to parse
+ * @param outputs The collection of audio outputs to modify
+ * @param current_partition The partition to which the outputs belong
+ * @return true if the line was valid and processed, false on parse error
+ */
 bool
-audio_output_state_read(const char *line, MultipleOutputs &outputs)
+audio_output_state_read(const char *line, MultipleOutputs &outputs, Partition *current_partition)
 {
 	long value;
 	char *endptr;
@@ -49,10 +86,6 @@ audio_output_state_read(const char *line, MultipleOutputs &outputs)
 	if (*endptr != ':' || (value != 0 && value != 1))
 		return false;
 
-	if (value != 0)
-		/* state is "enabled": no-op */
-		return true;
-
 	name = endptr + 1;
 	auto *ao = outputs.FindByName(name);
 	if (ao == nullptr) {
@@ -61,7 +94,16 @@ audio_output_state_read(const char *line, MultipleOutputs &outputs)
 		return true;
 	}
 
-	ao->LockSetEnabled(false);
+	if (current_partition->name != DEFAULT_PARTITION) {
+		// Move the output to this partition
+		FmtDebug(output_domain,
+				"Moving device {:?} from default to partition {:?}",
+				name, current_partition->name);
+		current_partition->outputs.AddMoveFrom(std::move(*ao), value != 0);
+		return true;
+	}
+
+	ao->LockSetEnabled(value != 0);
 	return true;
 }
 

src/output/State.hxx

@@ -11,9 +11,10 @@
 
 class MultipleOutputs;
 class BufferedOutputStream;
+struct Partition;
 
 bool
-audio_output_state_read(const char *line, MultipleOutputs &outputs);
+audio_output_state_read(const char *line, MultipleOutputs &outputs, Partition *partition);
 
 void
 audio_output_state_save(BufferedOutputStream &os,

src/queue/PlaylistState.cxx

@@ -168,6 +168,7 @@ playlist_state_restore(const StateFileConfig &config,
 		} else if (StringStartsWith(line,
 					    PLAYLIST_STATE_FILE_PLAYLIST_BEGIN)) {
 			playlist_state_load(file, song_loader, playlist);
+			break;
 		}
 	}