1 files changed, 65 insertions, 0 deletions
diff --git a/src/tangara/audio/stream_cues.cpp b/src/tangara/audio/stream_cues.cpp
new file mode 100644
index 00000000..7a6a1426
--- /dev/null
+++ b/src/tangara/audio/stream_cues.cpp
@@ -0,0 +1,65 @@
+/*
+ * Copyright 2024 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "audio/stream_cues.hpp"
+
+#include <cstdint>
+#include <memory>
+
+namespace audio {
+
+StreamCues::StreamCues() : now_(0) {}
+
+auto StreamCues::update(uint32_t sample) -> void {
+  if (sample < now_) {
+    // The current time must have overflowed. Deal with any cues between now_
+    // and UINT32_MAX, then proceed as normal.
+    while (!upcoming_.empty() && upcoming_.front().start_at > now_) {
+      current_ = upcoming_.front();
+      upcoming_.pop_front();
+    }
+  }
+  now_ = sample;
+
+  while (!upcoming_.empty() && upcoming_.front().start_at <= now_) {
+    current_ = upcoming_.front();
+    upcoming_.pop_front();
+  }
+}
+
+auto StreamCues::addCue(std::shared_ptr<TrackInfo> track, uint32_t sample)
+    -> void {
+  if (sample == now_) {
+    current_ = {track, now_};
+  } else {
+    upcoming_.push_back(Cue{
+        .track = track,
+        .start_at = sample,
+    });
+  }
+}
+
+auto StreamCues::current() -> std::pair<std::shared_ptr<TrackInfo>, uint32_t> {
+  if (!current_) {
+    return {};
+  }
+
+  uint32_t duration;
+  if (now_ < current_->start_at) {
+    // now_ overflowed since this track started.
+    duration = now_ + (UINT32_MAX - current_->start_at);
+  } else {
+    duration = now_ - current_->start_at;
+  }
+
+  return {current_->track, duration};
+}
+
+auto StreamCues::hasStream() -> bool {
+  return current_ || !upcoming_.empty();
+}
+
+}  // namespace audio