wire up the playing screen with some real data

Includes implementing song duration calculation for CBR MP3 files

1 files changed, 85 insertions, 0 deletions

diff --git a/src/audio/include/track_queue.hpp b/src/audio/include/track_queue.hpp
new file mode 100644
index 00000000..840d71ee
--- /dev/null
+++ b/src/audio/include/track_queue.hpp
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+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#pragma once
+
+#include <deque>
+#include <mutex>
+#include <vector>
+
+#include "track.hpp"
+
+namespace audio {
+
+/*
+ * Owns and manages a complete view of the playback queue. Includes the
+ * currently playing track, a truncated list of previously played tracks, and
+ * all future tracks that have been queued.
+ *
+ * In order to not use all of our memory, this class deals strictly with track
+ * ids. Consumers that need more data than this should fetch it from the
+ * database.
+ *
+ * Instances of this class are broadly safe to use from multiple tasks; each
+ * method represents an atomic operation. No guarantees are made about
+ * consistency between calls however. For example, there may be data changes
+ * between consecutive calls to AddNext() and GetUpcoming();
+ */
+class TrackQueue {
+ public:
+  TrackQueue();
+
+  /* Returns the currently playing track. */
+  auto GetCurrent() const -> std::optional<database::TrackId>;
+  /* Returns, in order, tracks that have been queued to be played next. */
+  auto GetUpcoming(std::size_t limit) const -> std::vector<database::TrackId>;
+
+  /*
+   * Enqueues a track, placing it immediately after the current track and
+   * before anything already queued.
+   *
+   * If there is no current track, the given track will begin playback.
+   */
+  auto AddNext(database::TrackId) -> void;
+  auto AddNext(const std::vector<database::TrackId>&) -> void;
+
+  /*
+   * Enqueues a track, placing it the end of all enqueued tracks.
+   *
+   * If there is no current track, the given track will begin playback.
+   */
+  auto AddLast(database::TrackId) -> void;
+  auto AddLast(const std::vector<database::TrackId>&) -> void;
+
+  /*
+   * Advances to the next track in the queue, placing the current track at the
+   * front of the 'played' queue.
+   */
+  auto Next() -> void;
+  auto Previous() -> void;
+
+  /*
+   * Removes all tracks from all queues, and stops any currently playing track.
+   */
+  auto Clear() -> void;
+  /*
+   * Removes a specific track from the queue of upcoming tracks. Has no effect
+   * on the currently playing track.
+   */
+  auto RemoveUpcoming(database::TrackId) -> void;
+
+  TrackQueue(const TrackQueue&) = delete;
+  TrackQueue& operator=(const TrackQueue&) = delete;
+
+ private:
+  mutable std::mutex mutex_;
+
+  std::deque<database::TrackId> played_;
+  std::deque<database::TrackId> upcoming_;
+  std::optional<database::TrackId> current_;
+};
+
+}  // namespace audio