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Merge pull request #2610 from matrix-org/kegan/ss-bugfix

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sliding sync: handle lone DELETE and INSERT operations
This commit is contained in:
kegsay
2022-08-23 08:42:34 +01:00
committed by GitHub
parent 760eeaeed7 37f8f736e0
commit 1df329df7c
2 changed files with 221 additions and 30 deletions
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104
src/sliding-sync.ts
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@@ -532,6 +532,65 @@ export class SlidingSync extends TypedEventEmitter<SlidingSyncEvent, SlidingSync
this.emit(SlidingSyncEvent.Lifecycle, state, resp, err);
}
private shiftRight(listIndex: number, hi: number, low: number) {
// l h
// 0,1,2,3,4 <- before
// 0,1,2,2,3 <- after, hi is deleted and low is duplicated
for (let i = hi; i > low; i--) {
if (this.lists[listIndex].isIndexInRange(i)) {
this.lists[listIndex].roomIndexToRoomId[i] =
this.lists[listIndex].roomIndexToRoomId[
i - 1
];
}
}
}
private shiftLeft(listIndex: number, hi: number, low: number) {
// l h
// 0,1,2,3,4 <- before
// 0,1,3,4,4 <- after, low is deleted and hi is duplicated
for (let i = low; i < hi; i++) {
if (this.lists[listIndex].isIndexInRange(i)) {
this.lists[listIndex].roomIndexToRoomId[i] =
this.lists[listIndex].roomIndexToRoomId[
i + 1
];
}
}
}
private removeEntry(listIndex: number, index: number) {
// work out the max index
let max = -1;
for (const n in this.lists[listIndex].roomIndexToRoomId) {
if (Number(n) > max) {
max = Number(n);
}
}
if (max < 0 || index > max) {
return;
}
// Everything higher than the gap needs to be shifted left.
this.shiftLeft(listIndex, max, index);
delete this.lists[listIndex].roomIndexToRoomId[max];
}
private addEntry(listIndex: number, index: number) {
// work out the max index
let max = -1;
for (const n in this.lists[listIndex].roomIndexToRoomId) {
if (Number(n) > max) {
max = Number(n);
}
}
if (max < 0 || index > max) {
return;
}
// Everything higher than the gap needs to be shifted right, +1 so we don't delete the highest element
this.shiftRight(listIndex, max+1, index);
}
private processListOps(list: ListResponse, listIndex: number): void {
let gapIndex = -1;
list.ops.forEach((op: Operation) => {
@@ -539,6 +598,10 @@ export class SlidingSync extends TypedEventEmitter<SlidingSyncEvent, SlidingSync
case "DELETE": {
logger.debug("DELETE", listIndex, op.index, ";");
delete this.lists[listIndex].roomIndexToRoomId[op.index];
if (gapIndex !== -1) {
// we already have a DELETE operation to process, so process it.
this.removeEntry(listIndex, gapIndex);
}
gapIndex = op.index;
break;
}
@@ -553,20 +616,9 @@ export class SlidingSync extends TypedEventEmitter<SlidingSyncEvent, SlidingSync
if (this.lists[listIndex].roomIndexToRoomId[op.index]) {
// something is in this space, shift items out of the way
if (gapIndex < 0) {
logger.debug(
"cannot work out where gap is, INSERT without previous DELETE! List: ",
listIndex,
);
return;
}
// 0,1,2,3 index
// [A,B,C,D]
// DEL 3
// [A,B,C,_]
// INSERT E 0
// [E,A,B,C]
// gapIndex=3, op.index=0
if (gapIndex > op.index) {
// we haven't been told where to shift from, so make way for a new room entry.
this.addEntry(listIndex, op.index);
} else if (gapIndex > op.index) {
// the gap is further down the list, shift every element to the right
// starting at the gap so we can just shift each element in turn:
// [A,B,C,_] gapIndex=3, op.index=0
@@ -574,26 +626,13 @@ export class SlidingSync extends TypedEventEmitter<SlidingSyncEvent, SlidingSync
// [A,B,B,C] i=2
// [A,A,B,C] i=1
// Terminate. We'll assign into op.index next.
for (let i = gapIndex; i > op.index; i--) {
if (this.lists[listIndex].isIndexInRange(i)) {
this.lists[listIndex].roomIndexToRoomId[i] =
this.lists[listIndex].roomIndexToRoomId[
i - 1
];
}
}
this.shiftRight(listIndex, gapIndex, op.index);
} else if (gapIndex < op.index) {
// the gap is further up the list, shift every element to the left
// starting at the gap so we can just shift each element in turn
for (let i = gapIndex; i < op.index; i++) {
if (this.lists[listIndex].isIndexInRange(i)) {
this.lists[listIndex].roomIndexToRoomId[i] =
this.lists[listIndex].roomIndexToRoomId[
i + 1
];
}
}
this.shiftLeft(listIndex, op.index, gapIndex);
}
gapIndex = -1; // forget the gap, we don't need it anymore.
}
this.lists[listIndex].roomIndexToRoomId[op.index] = op.room_id;
break;
@@ -633,6 +672,11 @@ export class SlidingSync extends TypedEventEmitter<SlidingSyncEvent, SlidingSync
}
}
});
if (gapIndex !== -1) {
// we already have a DELETE operation to process, so process it
// Everything higher than the gap needs to be shifted left.
this.removeEntry(listIndex, gapIndex);
}
}
/**