UNTESTED: note trailing zeros in /recordings reply

design/api.md

@@ -332,6 +332,13 @@ arbitrary order. Each recording object has the following properties:
 *   `videoSamples`: the number of samples (aka frames) of video in this
     recording.
 *   `sampleFileBytes`: the number of bytes of video in this recording.
+*   `hasTrailingZero`: the final frame of the final recording id described by
+    this row (`endId` if present, otherwise `startId`) has a duration of 0.
+    A frame's duration is calculated by subtracting its timestamp from the
+    following frame's timestamp. When a run ends, there's no following frame
+    and Moonfire NVR fills in a duration of 0. When using `/view.mp4`, it's
+    not possible to append additional segments after such frames, as noted
+    below.
 
 Under the property `videoSampleEntries`, an object mapping ids to objects with
 the following properties:
@@ -456,8 +463,9 @@ Bugs and limitations:
 *   The final recording in every "run" ends with a frame that has duration 0.
     It's not possible to append additional segments after such a frame;
     the server will return an error like `Invalid argument: unable to append
-    recording 2/16672 after recording 2/16671 with trailing zero`.
-    (See [#178](https://github.com/scottlamb/moonfire-nvr/issues/178).)
+    recording 2/16672 after recording 2/16671 with trailing zero`. See also
+    `hasTrailingZero` above, and
+    [#178](https://github.com/scottlamb/moonfire-nvr/issues/178).
 
 ### `GET /api/cameras/<uuid>/<stream>/view.mp4.txt`
 

server/db/db.rs

@@ -208,6 +208,7 @@ pub struct ListAggregatedRecordingsRow {
     pub open_id: u32,
     pub first_uncommitted: Option<i32>,
     pub growing: bool,
+    pub has_trailing_zero: bool,
 }
 
 impl ListAggregatedRecordingsRow {
@@ -231,6 +232,7 @@ impl ListAggregatedRecordingsRow {
                 None
             },
             growing,
+            has_trailing_zero: (row.flags & RecordingFlags::TrailingZero as i32) != 0,
         }
     }
 }
@@ -1352,6 +1354,7 @@ impl LockedDatabase {
             let run_start_id = recording_id - row.run_offset;
             let uncommitted = (row.flags & RecordingFlags::Uncommitted as i32) != 0;
             let growing = (row.flags & RecordingFlags::Growing as i32) != 0;
+            let has_trailing_zero = (row.flags & RecordingFlags::TrailingZero as i32) != 0;
             use std::collections::btree_map::Entry;
             match aggs.entry(run_start_id) {
                 Entry::Occupied(mut e) => {
@@ -1396,6 +1399,7 @@ impl LockedDatabase {
                             a.first_uncommitted = a.first_uncommitted.or(Some(recording_id));
                         }
                         a.growing = growing;
+                        a.has_trailing_zero = has_trailing_zero;
                     }
                 }
                 Entry::Vacant(e) => {

server/src/json.rs

@@ -493,6 +493,9 @@ pub struct Recording {
 
     #[serde(skip_serializing_if = "Not::not")]
     pub growing: bool,
+
+    #[serde(skip_serializing_if = "Not::not")]
+    pub has_trailing_zero: bool,
 }
 
 #[derive(Debug, Serialize)]

server/src/web.rs

@@ -765,6 +765,7 @@ impl Service {
                 video_samples: row.video_samples,
                 video_sample_entry_id: row.video_sample_entry_id,
                 growing: row.growing,
+                has_trailing_zero: row.has_trailing_zero,
             });
             if !out
                 .video_sample_entries