From 299abe3e7eabed950e1c305d81e4d5981ce85444 Mon Sep 17 00:00:00 2001
From: Danila Fedorin <danila.fedorin@gmail.com>
Date: Tue, 7 Sep 2021 13:17:44 -0700
Subject: [PATCH] Extract some gap filling functionality into a helper method

---
 src/matrix/room/BaseRoom.js | 96 ++++++++++++++++++++-----------------
 1 file changed, 52 insertions(+), 44 deletions(-)

diff --git a/src/matrix/room/BaseRoom.js b/src/matrix/room/BaseRoom.js
index 4a8f50b4..2d401a65 100644
--- a/src/matrix/room/BaseRoom.js
+++ b/src/matrix/room/BaseRoom.js
@@ -266,6 +266,53 @@ export class BaseRoom extends EventEmitter {
         }
     } 
 
+    async _fetchEvents(callback, log) {
+        const txn = await this._storage.readWriteTxn([
+            this._storage.storeNames.pendingEvents,
+            this._storage.storeNames.timelineEvents,
+            this._storage.storeNames.timelineRelations,
+            this._storage.storeNames.timelineFragments,
+        ]);
+        let extraGapFillChanges;
+        let gapResult;
+        try {
+            const relationWriter = new RelationWriter({
+                roomId: this._roomId,
+                fragmentIdComparer: this._fragmentIdComparer,
+                ownUserId: this._user.id,
+            });
+            const gapWriter = new GapWriter({
+                roomId: this._roomId,
+                storage: this._storage,
+                fragmentIdComparer: this._fragmentIdComparer,
+                relationWriter
+            });
+            const callbackResult = await callback(txn, gapWriter);
+            extraGapFillChanges = callbackResult.extraGapFillChanges;
+            gapResult = callbackResult.gapResult;
+        } catch (err) {
+            txn.abort();
+            throw err;
+        }
+        await txn.complete();
+        if (this._roomEncryption) {
+            const decryptRequest = this._decryptEntries(DecryptionSource.Timeline, gapResult.entries, null, log);
+            await decryptRequest.complete();
+        }
+        // once txn is committed, update in-memory state & emit events
+        for (const fragment of gapResult.fragments) {
+            this._fragmentIdComparer.add(fragment);
+        }
+        if (extraGapFillChanges) {
+            this._applyGapFill(extraGapFillChanges);
+        }
+        if (this._timeline) {
+            // these should not be added if not already there
+            this._timeline.replaceEntries(gapResult.updatedEntries);
+            this._timeline.addEntries(gapResult.entries);
+        }
+    }
+
     /** @public */
     fillGap(fragmentEntry, amount, log = null) {
         // TODO move some/all of this out of BaseRoom
@@ -287,51 +334,12 @@ export class BaseRoom extends EventEmitter {
                 }
             }, {log}).response();
 
-            const txn = await this._storage.readWriteTxn([
-                this._storage.storeNames.pendingEvents,
-                this._storage.storeNames.timelineEvents,
-                this._storage.storeNames.timelineRelations,
-                this._storage.storeNames.timelineFragments,
-            ]);
-            let extraGapFillChanges;
-            let gapResult;
-            try {
+            await this._fetchEvents(async (txn, gapWriter) => {
                 // detect remote echos of pending messages in the gap
-                extraGapFillChanges = await this._writeGapFill(response.chunk, txn, log);
-                // write new events into gap
-                const relationWriter = new RelationWriter({
-                    roomId: this._roomId,
-                    fragmentIdComparer: this._fragmentIdComparer,
-                    ownUserId: this._user.id,
-                });
-                const gapWriter = new GapWriter({
-                    roomId: this._roomId,
-                    storage: this._storage,
-                    fragmentIdComparer: this._fragmentIdComparer,
-                    relationWriter
-                });
-                gapResult = await gapWriter.writeFragmentFill(fragmentEntry, response, txn, log);
-            } catch (err) {
-                txn.abort();
-                throw err;
-            }
-            await txn.complete();
-            if (this._roomEncryption) {
-                const decryptRequest = this._decryptEntries(DecryptionSource.Timeline, gapResult.entries, null, log);
-                await decryptRequest.complete();
-            }
-            // once txn is committed, update in-memory state & emit events
-            for (const fragment of gapResult.fragments) {
-                this._fragmentIdComparer.add(fragment);
-            }
-            if (extraGapFillChanges) {
-                this._applyGapFill(extraGapFillChanges);
-            }
-            if (this._timeline) {
-                // these should not be added if not already there
-                this._timeline.replaceEntries(gapResult.updatedEntries);
-                this._timeline.addEntries(gapResult.entries);
-            }
+                const extraGapFillChanges = await this._writeGapFill(response.chunk, txn, log);
+                const gapResult = await gapWriter.writeFragmentFill(fragmentEntry, response, txn, log);
+                return { extraGapFillChanges, gapResult };
+            }, log);
         });
     }