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strip out old streams when they are no longer present #186

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strip out old streams when they are no longer present #186

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53 changes: 34 additions & 19 deletions src/react/useDeltaStreams.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -103,36 +103,51 @@ export function useDeltaStreams<
| undefined;

const newDeltas = cursorQuery?.streams.deltas;
if (newDeltas?.length && streamMessages) {
if (streamMessages) {
const newDeltasByStreamId = new Map<string, StreamDelta[]>();
for (const delta of newDeltas) {
const oldCursor = cursors[delta.streamId];
if (oldCursor && delta.start < oldCursor) continue;
const existing = newDeltasByStreamId.get(delta.streamId);
if (existing) {
const previousEnd = existing.at(-1)!.end;
assert(
previousEnd === delta.start,
`Gap found in deltas for ${delta.streamId} jumping to ${delta.start} from ${previousEnd}`,
);
existing.push(delta);
} else {
assert(
!oldCursor || oldCursor === delta.start,
`Gap found - first delta after ${oldCursor} is ${delta.start} for stream ${delta.streamId}`,
);
newDeltasByStreamId.set(delta.streamId, [delta]);
if (newDeltas?.length) {
for (const delta of newDeltas) {
const oldCursor = cursors[delta.streamId];
if (oldCursor && delta.start < oldCursor) continue;
const existing = newDeltasByStreamId.get(delta.streamId);
if (existing) {
const previousEnd = existing.at(-1)!.end;
assert(
previousEnd === delta.start,
`Gap found in deltas for ${delta.streamId} jumping to ${delta.start} from ${previousEnd}`,
);
existing.push(delta);
} else {
assert(
!oldCursor || oldCursor === delta.start,
`Gap found - first delta after ${oldCursor} is ${delta.start} for stream ${delta.streamId}`,
);
newDeltasByStreamId.set(delta.streamId, [delta]);
}
}
}
const newCursors: Record<string, number> = {};
let cursorsChanged = false;
for (const { streamId } of streamMessages) {
const cursor =
newDeltasByStreamId.get(streamId)?.at(-1)?.end ?? cursors[streamId];
if (cursor !== undefined) {
newCursors[streamId] = cursor;
if (cursors[streamId] !== cursor) {
cursorsChanged = true;
}
}
}
setCursors(newCursors);
// Also check if any streams were removed from cursors
for (const streamId in cursors) {
if (!(streamId in newCursors)) {
cursorsChanged = true;
break;
}
}
if (cursorsChanged) {
setCursors(newCursors);
}

// we defensively create a new object so object identity matches contents
state.deltaStreams = streamMessages.map((streamMessage) => {
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