From 65015e686fa6b9d2c2a566a719b5608757f352c1 Mon Sep 17 00:00:00 2001
From: Matthew Chen <matthew@signal.org>
Date: Mon, 9 Apr 2018 13:58:12 -0400
Subject: [PATCH 1/5] Tap on quoted replies.

---
 .../Cells/ConversationViewCell.h              |   2 +
 .../ConversationView/Cells/OWSMessageCell.m   |   6 +-
 .../ConversationViewController.m              | 170 ++++++++++++++++--
 .../src/Messages/Interactions/TSInteraction.h |   2 +-
 .../src/Messages/Interactions/TSInteraction.m |   4 +-
 .../src/Storage/TSDatabaseSecondaryIndexes.h  |   4 +-
 .../src/Storage/TSDatabaseSecondaryIndexes.m  |   6 +-
 7 files changed, 175 insertions(+), 19 deletions(-)

diff --git a/Signal/src/ViewControllers/ConversationView/Cells/ConversationViewCell.h b/Signal/src/ViewControllers/ConversationView/Cells/ConversationViewCell.h
index e4f5baec3..3172388f2 100644
--- a/Signal/src/ViewControllers/ConversationView/Cells/ConversationViewCell.h
+++ b/Signal/src/ViewControllers/ConversationView/Cells/ConversationViewCell.h
@@ -12,6 +12,7 @@ NS_ASSUME_NONNULL_BEGIN
 @class TSInteraction;
 @class TSMessage;
 @class TSOutgoingMessage;
+@class TSQuotedMessage;
 
 @protocol ConversationViewCellDelegate <NSObject>
 
@@ -26,6 +27,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)didTapFailedIncomingAttachment:(ConversationViewItem *)viewItem
                      attachmentPointer:(TSAttachmentPointer *)attachmentPointer;
 - (void)didTapFailedOutgoingMessage:(TSOutgoingMessage *)message;
+- (void)didTapQuotedMessage:(ConversationViewItem *)viewItem quotedMessage:(TSQuotedMessage *)quotedMessage;
 - (void)didPanWithGestureRecognizer:(UIPanGestureRecognizer *)gestureRecognizer
                            viewItem:(ConversationViewItem *)conversationItem;
 
diff --git a/Signal/src/ViewControllers/ConversationView/Cells/OWSMessageCell.m b/Signal/src/ViewControllers/ConversationView/Cells/OWSMessageCell.m
index 5e807b652..3a950c471 100644
--- a/Signal/src/ViewControllers/ConversationView/Cells/OWSMessageCell.m
+++ b/Signal/src/ViewControllers/ConversationView/Cells/OWSMessageCell.m
@@ -515,7 +515,11 @@ NS_ASSUME_NONNULL_BEGIN
             [self handleMediaTapGesture];
             break;
         case OWSMessageGestureLocation_QuotedReply:
-            // TODO:
+            if (self.message.quotedMessage) {
+                [self.delegate didTapQuotedMessage:self.viewItem quotedMessage:self.message.quotedMessage];
+            } else {
+                OWSFail(@"%@ Missing quoted message.", self.logTag)
+            }
             break;
     }
 }
diff --git a/Signal/src/ViewControllers/ConversationView/ConversationViewController.m b/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
index ef1de1c83..b83df414d 100644
--- a/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
+++ b/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
@@ -90,6 +90,7 @@
 #import <SignalServiceKit/TSQuotedMessage.h>
 #import <SignalServiceKit/Threading.h>
 #import <YapDatabase/YapDatabase.h>
+#import <YapDatabase/YapDatabaseAutoView.h>
 #import <YapDatabase/YapDatabaseViewChange.h>
 #import <YapDatabase/YapDatabaseViewConnection.h>
 
@@ -1511,32 +1512,37 @@ typedef enum : NSUInteger {
     }
     static const CGFloat kThreshold = 50.f;
     if (self.collectionView.contentOffset.y < kThreshold) {
-        [self loadMoreMessages];
+        [self loadAnotherPageOfMessages];
     }
 }
 
-- (void)loadMoreMessages
+- (void)loadAnotherPageOfMessages
 {
     BOOL hasEarlierUnseenMessages = self.dynamicInteractions.hasMoreUnseenMessages;
 
+    [self loadNMoreMessages:kYapDatabasePageSize];
+
+    // Don’t auto-scroll after “loading more messages” unless we have “more unseen messages”.
+    //
+    // Otherwise, tapping on "load more messages" autoscrolls you downward which is completely wrong.
+    if (hasEarlierUnseenMessages) {
+        [self scrollToUnreadIndicatorAnimated];
+    }
+}
+
+- (void)loadNMoreMessages:(NSUInteger)numberOfMessagesToLoad
+{
     // We want to restore the current scroll state after we update the range, update
     // the dynamic interactions and re-layout.  Here we take a "before" snapshot.
     CGFloat scrollDistanceToBottom = self.safeContentHeight - self.collectionView.contentOffset.y;
 
-    self.lastRangeLength = MIN(self.lastRangeLength + kYapDatabasePageSize, (NSUInteger) kYapDatabaseRangeMaxLength);
+    self.lastRangeLength = MIN(self.lastRangeLength + numberOfMessagesToLoad, (NSUInteger)kYapDatabaseRangeMaxLength);
 
     [self resetMappings];
 
     [self.layout prepareLayout];
 
     self.collectionView.contentOffset = CGPointMake(0, self.safeContentHeight - scrollDistanceToBottom);
-
-    // Don’t auto-scroll after “loading more messages” unless we have “more unseen messages”.
-    //
-    // Otherwise, tapping on "load more messages" autoscrolls you downward which is completely wrong.
-    if (hasEarlierUnseenMessages) {
-        [self scrollToUnreadIndicatorAnimated];
-    }
 }
 
 - (void)updateShowLoadMoreHeader
@@ -2124,6 +2130,150 @@ typedef enum : NSUInteger {
     [self handleUnsentMessageTap:message];
 }
 
+- (void)didTapQuotedMessage:(ConversationViewItem *)viewItem quotedMessage:(TSQuotedMessage *)quotedMessage
+{
+    OWSAssertIsOnMainThread();
+    OWSAssert(viewItem);
+    OWSAssert(quotedMessage);
+    OWSAssert(quotedMessage.timestamp > 0);
+    OWSAssert(quotedMessage.authorId.length > 0);
+
+    // We try to find the "quoted interaction" AND
+    // the range within the mapping that includes it.
+    __block TSInteraction *_Nullable quotedInteraction = nil;
+    // NOTE: Since the range _IS NOT_ filtered by author,
+    // and timestamp collisions are possible, it's possible
+    // for:
+    //
+    // * The range to include more than the "quoted interaction".
+    // * The range to be non-empty but NOT include the "quoted interaction",
+    //   although this would be a bug.
+    __block NSRange itemRange;
+    itemRange.location = NSNotFound;
+    __block NSUInteger threadInteractionCount = 0;
+
+    [self.uiDatabaseConnection readWithBlock:^(YapDatabaseReadTransaction *transaction) {
+        quotedInteraction = [self findInteractionInThreadByTimestamp:quotedMessage.timestamp
+                                                            authorId:quotedMessage.authorId
+                                                         transaction:transaction];
+        if (!quotedInteraction) {
+            return;
+        }
+
+        YapDatabaseAutoViewTransaction *_Nullable extension =
+            [transaction extension:TSMessageDatabaseViewExtensionName];
+        if (!extension) {
+            OWSFail(@"%@ Couldn't load view.", self.logTag);
+            return;
+        }
+
+        threadInteractionCount = [extension numberOfItemsInGroup:self.thread.uniqueId];
+
+        // See comments on YapDatabaseViewFind.
+        //
+        // Essentially we define a comparator/sort on timestamp.
+        YapDatabaseViewFind *viewFind =
+            [YapDatabaseViewFind withObjectBlock:^NSComparisonResult(NSString *collection, NSString *key, id object) {
+                if (![object isKindOfClass:[TSInteraction class]]) {
+                    OWSFail(@"%@ Unexpected type in database view.", self.logTag);
+                    return NSOrderedSame;
+                }
+
+                TSInteraction *interaction = object;
+
+                // For the findBlock, the "left operand" is the row that is passed,
+                // and the "right operand" is the desired range.
+                if (interaction.timestamp == quotedMessage.timestamp) {
+
+                    return NSOrderedSame;
+                } else if (interaction.timestamp < quotedMessage.timestamp) {
+                    // NSOrderedAscending  : The left operand is smaller than the right operand.
+                    return NSOrderedAscending;
+                } else {
+                    // NSOrderedDescending : The left operand is greater than the right operand.
+                    return NSOrderedDescending;
+                }
+            }];
+        itemRange = [extension findRangeInGroup:self.thread.uniqueId using:viewFind];
+    }];
+
+    if (itemRange.location == NSNotFound) {
+        OWSFail(@"%@ Couldn't find range of quoted reply.", self.logTag);
+        return;
+    }
+
+    NSInteger desiredWindowSize = MAX(0, 1 + (NSInteger)threadInteractionCount - (NSInteger)itemRange.location);
+    NSUInteger oldLoadWindowSize = [self.messageMappings numberOfItemsInGroup:self.thread.uniqueId];
+    NSInteger additionalItemsToLoad = MAX(0, desiredWindowSize - (NSInteger)oldLoadWindowSize);
+
+    NSInteger dstIndex = 0;
+    if (additionalItemsToLoad > 0) {
+        // Try to load more messages so that the quoted messages
+        // is in the load window.
+        //
+        // This may fail if the quoted message is very old, in which
+        // case we'll load the max number of messages.
+        [self loadNMoreMessages:(NSUInteger)additionalItemsToLoad];
+        // Scroll to the first item, which should be the quoted message,
+        // or if we couldn't load it, the oldest loadable message.
+        dstIndex = 0;
+    } else {
+        // Scroll to the quoted message, which is already in the load window.
+        dstIndex = 1 + (NSInteger)oldLoadWindowSize - desiredWindowSize;
+    }
+
+    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:dstIndex inSection:0];
+    [self.collectionView scrollToItemAtIndexPath:indexPath
+                                atScrollPosition:UICollectionViewScrollPositionTop
+                                        animated:YES];
+
+    // TODO: Highlight the quoted message?
+}
+
+- (nullable TSInteraction *)findInteractionInThreadByTimestamp:(uint64_t)timestamp
+                                                      authorId:(NSString *)authorId
+                                                   transaction:(YapDatabaseReadTransaction *)transaction
+{
+    OWSAssert(timestamp > 0);
+    OWSAssert(authorId.length > 0);
+
+    NSString *localNumber = [TSAccountManager localNumber];
+    if (localNumber.length < 1) {
+        return nil;
+    }
+
+    NSArray<TSInteraction *> *interactions =
+        [TSInteraction interactionsWithTimestamp:timestamp ofClass:[TSMessage class] withTransaction:transaction];
+
+    TSInteraction *_Nullable result = nil;
+    for (TSInteraction *interaction in interactions) {
+        NSString *_Nullable messageAuthorId = nil;
+        if ([interaction isKindOfClass:[TSIncomingMessage class]]) {
+            TSIncomingMessage *incomingMessage = (TSIncomingMessage *)interaction;
+            messageAuthorId = incomingMessage.authorId;
+        } else if ([interaction isKindOfClass:[TSOutgoingMessage class]]) {
+            messageAuthorId = localNumber;
+        }
+        if (messageAuthorId.length < 1) {
+            OWSFail(@"%@ Message missing author id.", self.logTag);
+            continue;
+        }
+        if (![authorId isEqualToString:messageAuthorId]) {
+            continue;
+        }
+        if (![interaction.uniqueThreadId isEqualToString:self.thread.uniqueId]) {
+            continue;
+        }
+        if (result) {
+            // In case of collision, take the first.
+            DDLogError(@"%@ more than one matching interaction in thread.", self.logTag);
+            continue;
+        }
+        result = interaction;
+    }
+    return result;
+}
+
 - (void)showMetadataViewForViewItem:(ConversationViewItem *)conversationItem
 {
     OWSAssertIsOnMainThread();
diff --git a/SignalServiceKit/src/Messages/Interactions/TSInteraction.h b/SignalServiceKit/src/Messages/Interactions/TSInteraction.h
index 09e28fa5b..1ea070928 100644
--- a/SignalServiceKit/src/Messages/Interactions/TSInteraction.h
+++ b/SignalServiceKit/src/Messages/Interactions/TSInteraction.h
@@ -41,7 +41,7 @@ typedef NS_ENUM(NSInteger, OWSInteractionType) {
 
 + (NSArray<TSInteraction *> *)interactionsWithTimestamp:(uint64_t)timestamp
                                                 ofClass:(Class)clazz
-                                        withTransaction:(YapDatabaseReadWriteTransaction *)transaction;
+                                        withTransaction:(YapDatabaseReadTransaction *)transaction;
 
 + (NSArray<TSInteraction *> *)interactionsWithTimestamp:(uint64_t)timestamp
                                                  filter:(BOOL (^_Nonnull)(TSInteraction *))filter
diff --git a/SignalServiceKit/src/Messages/Interactions/TSInteraction.m b/SignalServiceKit/src/Messages/Interactions/TSInteraction.m
index 7bfa746eb..b5319d9d0 100644
--- a/SignalServiceKit/src/Messages/Interactions/TSInteraction.m
+++ b/SignalServiceKit/src/Messages/Interactions/TSInteraction.m
@@ -14,7 +14,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 + (NSArray<TSInteraction *> *)interactionsWithTimestamp:(uint64_t)timestamp
                                                 ofClass:(Class)clazz
-                                        withTransaction:(YapDatabaseReadWriteTransaction *)transaction
+                                        withTransaction:(YapDatabaseReadTransaction *)transaction
 {
     OWSAssert(timestamp > 0);
 
@@ -28,7 +28,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 + (NSArray<TSInteraction *> *)interactionsWithTimestamp:(uint64_t)timestamp
                                                  filter:(BOOL (^_Nonnull)(TSInteraction *))filter
-                                        withTransaction:(YapDatabaseReadWriteTransaction *)transaction
+                                        withTransaction:(YapDatabaseReadTransaction *)transaction
 {
     OWSAssert(timestamp > 0);
 
diff --git a/SignalServiceKit/src/Storage/TSDatabaseSecondaryIndexes.h b/SignalServiceKit/src/Storage/TSDatabaseSecondaryIndexes.h
index 6d3b4b828..5db2ac8cb 100644
--- a/SignalServiceKit/src/Storage/TSDatabaseSecondaryIndexes.h
+++ b/SignalServiceKit/src/Storage/TSDatabaseSecondaryIndexes.h
@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
 //
 
 #import <YapDatabase/YapDatabaseSecondaryIndex.h>
@@ -11,6 +11,6 @@
 
 + (void)enumerateMessagesWithTimestamp:(uint64_t)timestamp
                              withBlock:(void (^)(NSString *collection, NSString *key, BOOL *stop))block
-                      usingTransaction:(YapDatabaseReadWriteTransaction *)transaction;
+                      usingTransaction:(YapDatabaseReadTransaction *)transaction;
 
 @end
diff --git a/SignalServiceKit/src/Storage/TSDatabaseSecondaryIndexes.m b/SignalServiceKit/src/Storage/TSDatabaseSecondaryIndexes.m
index f63e63366..f61055edd 100644
--- a/SignalServiceKit/src/Storage/TSDatabaseSecondaryIndexes.m
+++ b/SignalServiceKit/src/Storage/TSDatabaseSecondaryIndexes.m
@@ -1,9 +1,8 @@
 //
-//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
 //
 
 #import "TSDatabaseSecondaryIndexes.h"
-
 #import "TSInteraction.h"
 
 #define TSTimeStampSQLiteIndex @"messagesTimeStamp"
@@ -34,7 +33,8 @@
 
 + (void)enumerateMessagesWithTimestamp:(uint64_t)timestamp
                              withBlock:(void (^)(NSString *collection, NSString *key, BOOL *stop))block
-                      usingTransaction:(YapDatabaseReadWriteTransaction *)transaction {
+                      usingTransaction:(YapDatabaseReadTransaction *)transaction
+{
     NSString *formattedString = [NSString stringWithFormat:@"WHERE %@ = %lld", TSTimeStampSQLiteIndex, timestamp];
     YapDatabaseQuery *query   = [YapDatabaseQuery queryWithFormat:formattedString];
     [[transaction ext:@"idx"] enumerateKeysMatchingQuery:query usingBlock:block];

From 8b060a187ce958c9f38c0e6ebc79719ad9309d03 Mon Sep 17 00:00:00 2001
From: Matthew Chen <matthew@signal.org>
Date: Mon, 9 Apr 2018 14:22:36 -0400
Subject: [PATCH 2/5] Tap on quoted replies.

---
 .../ConversationViewController.m              | 130 +++++++++++++-----
 1 file changed, 93 insertions(+), 37 deletions(-)

diff --git a/Signal/src/ViewControllers/ConversationView/ConversationViewController.m b/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
index b83df414d..572dc31a3 100644
--- a/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
+++ b/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
@@ -2138,9 +2138,96 @@ typedef enum : NSUInteger {
     OWSAssert(quotedMessage.timestamp > 0);
     OWSAssert(quotedMessage.authorId.length > 0);
 
+    // We try to range of items within the current thread's interactions
+    // that includs the "quoted interaction".
+    // NOTE: Since the range _IS NOT_ filtered by author,
+    // and timestamp collisions are possible, it's possible
+    // for:
+    //
+    // * The range to include more than the "quoted interaction".
+    // * The range to be non-empty but NOT include the "quoted interaction",
+    //   although this would be a bug.
+    NSUInteger threadInteractionCount = 0;
+    NSRange itemRange = [self findRangeOfQuotedMessage:quotedMessage threadInteractionCount:&threadInteractionCount];
+
+    if (itemRange.location == NSNotFound) {
+        OWSFail(@"%@ Couldn't find range of quoted reply.", self.logTag);
+        return;
+    }
+
+    NSInteger desiredWindowSize = MAX(0, 1 + (NSInteger)threadInteractionCount - (NSInteger)itemRange.location);
+    NSUInteger oldLoadWindowSize = [self.messageMappings numberOfItemsInGroup:self.thread.uniqueId];
+    NSInteger additionalItemsToLoad = MAX(0, desiredWindowSize - (NSInteger)oldLoadWindowSize);
+
+    NSInteger dstIndex = 0;
+    if (additionalItemsToLoad > 0) {
+        // Try to load more messages so that the quoted message
+        // is in the load window.
+        //
+        // This may fail if the quoted message is very old, in which
+        // case we'll load the max number of messages.
+        [self loadNMoreMessages:(NSUInteger)additionalItemsToLoad];
+        
+        // Scroll to the first item, which should be the quoted message,
+        // or if we couldn't load it, the oldest loadable message.
+        //
+        // We use `indexPathRowOfQuotedMessage` instead of doing
+        // some index math because:
+        //
+        // * Resetting the mapping may integrate other pending changes.
+        // * Dynamic interactions may change.
+        dstIndex = (NSInteger)[self indexPathRowOfQuotedMessage:quotedMessage];
+    } else {
+        // Scroll to the quoted message, which is already in the load window.
+        dstIndex = 1 + (NSInteger)oldLoadWindowSize - desiredWindowSize;
+    }
+
+    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:dstIndex inSection:0];
+    [self.collectionView scrollToItemAtIndexPath:indexPath
+                                atScrollPosition:UICollectionViewScrollPositionTop
+                                        animated:YES];
+
+    // TODO: Highlight the quoted message?
+}
+
+// This method makes a best effort to determine the best scroll position
+// after loading more interactions when trying to scroll to a quoted
+// message.
+//
+// It prefers to be simple than to correctly handle edge cases like multiple
+// interactions with the same timestamp.
+- (NSUInteger)indexPathRowOfQuotedMessage:(TSQuotedMessage *)quotedMessage
+{
+    OWSAssertIsOnMainThread();
+    OWSAssert(quotedMessage);
+    OWSAssert(quotedMessage.timestamp > 0);
+    OWSAssert(quotedMessage.authorId.length > 0);
+
+    NSUInteger result = 0;
+    for (NSUInteger row = 0; row < self.viewItems.count; row++) {
+        ConversationViewItem *viewItem = self.viewItems[row];
+        if (viewItem.interaction.timestamp > quotedMessage.timestamp) {
+            break;
+        }
+        result = row;
+    }
+    return result;
+}
+
+// If result range is valid, then threadInteractionCount will have a valid value too.
+- (NSRange)findRangeOfQuotedMessage:(TSQuotedMessage *)quotedMessage
+             threadInteractionCount:(NSUInteger *)threadInteractionCount
+{
+    OWSAssertIsOnMainThread();
+    OWSAssert(quotedMessage);
+    OWSAssert(quotedMessage.timestamp > 0);
+    OWSAssert(quotedMessage.authorId.length > 0);
+    OWSAssert(threadInteractionCount);
+
+    *threadInteractionCount = 0;
+
     // We try to find the "quoted interaction" AND
     // the range within the mapping that includes it.
-    __block TSInteraction *_Nullable quotedInteraction = nil;
     // NOTE: Since the range _IS NOT_ filtered by author,
     // and timestamp collisions are possible, it's possible
     // for:
@@ -2150,12 +2237,11 @@ typedef enum : NSUInteger {
     //   although this would be a bug.
     __block NSRange itemRange;
     itemRange.location = NSNotFound;
-    __block NSUInteger threadInteractionCount = 0;
 
     [self.uiDatabaseConnection readWithBlock:^(YapDatabaseReadTransaction *transaction) {
-        quotedInteraction = [self findInteractionInThreadByTimestamp:quotedMessage.timestamp
-                                                            authorId:quotedMessage.authorId
-                                                         transaction:transaction];
+        TSInteraction *_Nullable quotedInteraction = [self findInteractionInThreadByTimestamp:quotedMessage.timestamp
+                                                                                     authorId:quotedMessage.authorId
+                                                                                  transaction:transaction];
         if (!quotedInteraction) {
             return;
         }
@@ -2167,7 +2253,7 @@ typedef enum : NSUInteger {
             return;
         }
 
-        threadInteractionCount = [extension numberOfItemsInGroup:self.thread.uniqueId];
+        *threadInteractionCount = [extension numberOfItemsInGroup:self.thread.uniqueId];
 
         // See comments on YapDatabaseViewFind.
         //
@@ -2197,37 +2283,7 @@ typedef enum : NSUInteger {
         itemRange = [extension findRangeInGroup:self.thread.uniqueId using:viewFind];
     }];
 
-    if (itemRange.location == NSNotFound) {
-        OWSFail(@"%@ Couldn't find range of quoted reply.", self.logTag);
-        return;
-    }
-
-    NSInteger desiredWindowSize = MAX(0, 1 + (NSInteger)threadInteractionCount - (NSInteger)itemRange.location);
-    NSUInteger oldLoadWindowSize = [self.messageMappings numberOfItemsInGroup:self.thread.uniqueId];
-    NSInteger additionalItemsToLoad = MAX(0, desiredWindowSize - (NSInteger)oldLoadWindowSize);
-
-    NSInteger dstIndex = 0;
-    if (additionalItemsToLoad > 0) {
-        // Try to load more messages so that the quoted messages
-        // is in the load window.
-        //
-        // This may fail if the quoted message is very old, in which
-        // case we'll load the max number of messages.
-        [self loadNMoreMessages:(NSUInteger)additionalItemsToLoad];
-        // Scroll to the first item, which should be the quoted message,
-        // or if we couldn't load it, the oldest loadable message.
-        dstIndex = 0;
-    } else {
-        // Scroll to the quoted message, which is already in the load window.
-        dstIndex = 1 + (NSInteger)oldLoadWindowSize - desiredWindowSize;
-    }
-
-    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:dstIndex inSection:0];
-    [self.collectionView scrollToItemAtIndexPath:indexPath
-                                atScrollPosition:UICollectionViewScrollPositionTop
-                                        animated:YES];
-
-    // TODO: Highlight the quoted message?
+    return itemRange;
 }
 
 - (nullable TSInteraction *)findInteractionInThreadByTimestamp:(uint64_t)timestamp

From f2b416d80042bb2f1f675977160059c4dec51643 Mon Sep 17 00:00:00 2001
From: Matthew Chen <matthew@signal.org>
Date: Tue, 10 Apr 2018 09:45:58 -0400
Subject: [PATCH 3/5] Respond to CR.

---
 .../ConversationViewController.m              | 240 +++++++-----------
 SignalMessaging/utils/ThreadUtil.h            |   8 +
 SignalMessaging/utils/ThreadUtil.m            |  46 ++++
 3 files changed, 139 insertions(+), 155 deletions(-)

diff --git a/Signal/src/ViewControllers/ConversationView/ConversationViewController.m b/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
index 572dc31a3..10e4e19b0 100644
--- a/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
+++ b/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
@@ -2138,96 +2138,15 @@ typedef enum : NSUInteger {
     OWSAssert(quotedMessage.timestamp > 0);
     OWSAssert(quotedMessage.authorId.length > 0);
 
-    // We try to range of items within the current thread's interactions
-    // that includs the "quoted interaction".
-    // NOTE: Since the range _IS NOT_ filtered by author,
-    // and timestamp collisions are possible, it's possible
-    // for:
+    // We try to find the index of the item within the current thread's
+    // interactions that includes the "quoted interaction".
+    //
+    // NOTE: There are two indices:
+    //
+    // * The "group index" of the member of the database views group at
+    //   the db conneciton's current checkpoint.
+    // * The "index row/section" in the message mapping.
     //
-    // * The range to include more than the "quoted interaction".
-    // * The range to be non-empty but NOT include the "quoted interaction",
-    //   although this would be a bug.
-    NSUInteger threadInteractionCount = 0;
-    NSRange itemRange = [self findRangeOfQuotedMessage:quotedMessage threadInteractionCount:&threadInteractionCount];
-
-    if (itemRange.location == NSNotFound) {
-        OWSFail(@"%@ Couldn't find range of quoted reply.", self.logTag);
-        return;
-    }
-
-    NSInteger desiredWindowSize = MAX(0, 1 + (NSInteger)threadInteractionCount - (NSInteger)itemRange.location);
-    NSUInteger oldLoadWindowSize = [self.messageMappings numberOfItemsInGroup:self.thread.uniqueId];
-    NSInteger additionalItemsToLoad = MAX(0, desiredWindowSize - (NSInteger)oldLoadWindowSize);
-
-    NSInteger dstIndex = 0;
-    if (additionalItemsToLoad > 0) {
-        // Try to load more messages so that the quoted message
-        // is in the load window.
-        //
-        // This may fail if the quoted message is very old, in which
-        // case we'll load the max number of messages.
-        [self loadNMoreMessages:(NSUInteger)additionalItemsToLoad];
-        
-        // Scroll to the first item, which should be the quoted message,
-        // or if we couldn't load it, the oldest loadable message.
-        //
-        // We use `indexPathRowOfQuotedMessage` instead of doing
-        // some index math because:
-        //
-        // * Resetting the mapping may integrate other pending changes.
-        // * Dynamic interactions may change.
-        dstIndex = (NSInteger)[self indexPathRowOfQuotedMessage:quotedMessage];
-    } else {
-        // Scroll to the quoted message, which is already in the load window.
-        dstIndex = 1 + (NSInteger)oldLoadWindowSize - desiredWindowSize;
-    }
-
-    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:dstIndex inSection:0];
-    [self.collectionView scrollToItemAtIndexPath:indexPath
-                                atScrollPosition:UICollectionViewScrollPositionTop
-                                        animated:YES];
-
-    // TODO: Highlight the quoted message?
-}
-
-// This method makes a best effort to determine the best scroll position
-// after loading more interactions when trying to scroll to a quoted
-// message.
-//
-// It prefers to be simple than to correctly handle edge cases like multiple
-// interactions with the same timestamp.
-- (NSUInteger)indexPathRowOfQuotedMessage:(TSQuotedMessage *)quotedMessage
-{
-    OWSAssertIsOnMainThread();
-    OWSAssert(quotedMessage);
-    OWSAssert(quotedMessage.timestamp > 0);
-    OWSAssert(quotedMessage.authorId.length > 0);
-
-    NSUInteger result = 0;
-    for (NSUInteger row = 0; row < self.viewItems.count; row++) {
-        ConversationViewItem *viewItem = self.viewItems[row];
-        if (viewItem.interaction.timestamp > quotedMessage.timestamp) {
-            break;
-        }
-        result = row;
-    }
-    return result;
-}
-
-// If result range is valid, then threadInteractionCount will have a valid value too.
-- (NSRange)findRangeOfQuotedMessage:(TSQuotedMessage *)quotedMessage
-             threadInteractionCount:(NSUInteger *)threadInteractionCount
-{
-    OWSAssertIsOnMainThread();
-    OWSAssert(quotedMessage);
-    OWSAssert(quotedMessage.timestamp > 0);
-    OWSAssert(quotedMessage.authorId.length > 0);
-    OWSAssert(threadInteractionCount);
-
-    *threadInteractionCount = 0;
-
-    // We try to find the "quoted interaction" AND
-    // the range within the mapping that includes it.
     // NOTE: Since the range _IS NOT_ filtered by author,
     // and timestamp collisions are possible, it's possible
     // for:
@@ -2235,13 +2154,15 @@ typedef enum : NSUInteger {
     // * The range to include more than the "quoted interaction".
     // * The range to be non-empty but NOT include the "quoted interaction",
     //   although this would be a bug.
-    __block NSRange itemRange;
-    itemRange.location = NSNotFound;
+    __block TSInteraction *_Nullable quotedInteraction;
+    __block NSUInteger threadInteractionCount = 0;
+    __block NSNumber *_Nullable groupIndex = nil;
 
     [self.uiDatabaseConnection readWithBlock:^(YapDatabaseReadTransaction *transaction) {
-        TSInteraction *_Nullable quotedInteraction = [self findInteractionInThreadByTimestamp:quotedMessage.timestamp
-                                                                                     authorId:quotedMessage.authorId
-                                                                                  transaction:transaction];
+        quotedInteraction = [ThreadUtil findInteractionInThreadByTimestamp:quotedMessage.timestamp
+                                                                  authorId:quotedMessage.authorId
+                                                            threadUniqueId:self.thread.uniqueId
+                                                               transaction:transaction];
         if (!quotedInteraction) {
             return;
         }
@@ -2253,81 +2174,90 @@ typedef enum : NSUInteger {
             return;
         }
 
-        *threadInteractionCount = [extension numberOfItemsInGroup:self.thread.uniqueId];
+        threadInteractionCount = [extension numberOfItemsInGroup:self.thread.uniqueId];
+
+        groupIndex = [self findGroupIndexOfThreadInteraction:quotedInteraction transaction:transaction];
+    }];
+
+    if (!quotedInteraction || !groupIndex) {
+        DDLogError(@"%@ Couldn't find message quoted in quoted reply.", self.logTag);
+        return;
+    }
+
+    NSUInteger indexRow = 0;
+    NSUInteger indexSection = 0;
+    BOOL isInMappings = [self.messageMappings getRow:&indexRow
+                                             section:&indexSection
+                                            forIndex:groupIndex.unsignedIntegerValue
+                                             inGroup:self.thread.uniqueId];
+
+    if (!isInMappings) {
+        NSInteger desiredWindowSize = MAX(0, 1 + (NSInteger)threadInteractionCount - groupIndex.integerValue);
+        NSUInteger oldLoadWindowSize = [self.messageMappings numberOfItemsInGroup:self.thread.uniqueId];
+        NSInteger additionalItemsToLoad = MAX(0, desiredWindowSize - (NSInteger)oldLoadWindowSize);
+        if (additionalItemsToLoad < 1) {
+            DDLogError(@"%@ Couldn't determine how to load quoted reply.", self.logTag);
+            return;
+        }
 
-        // See comments on YapDatabaseViewFind.
+        // Try to load more messages so that the quoted message
+        // is in the load window.
         //
-        // Essentially we define a comparator/sort on timestamp.
-        YapDatabaseViewFind *viewFind =
-            [YapDatabaseViewFind withObjectBlock:^NSComparisonResult(NSString *collection, NSString *key, id object) {
-                if (![object isKindOfClass:[TSInteraction class]]) {
-                    OWSFail(@"%@ Unexpected type in database view.", self.logTag);
-                    return NSOrderedSame;
-                }
+        // This may fail if the quoted message is very old, in which
+        // case we'll load the max number of messages.
+        [self loadNMoreMessages:(NSUInteger)additionalItemsToLoad];
 
-                TSInteraction *interaction = object;
+        // `loadNMoreMessages` will reset the mapping and possibly
+        // integrate new changes, so we need to reload the "group index"
+        // of the quoted message.
+        [self.uiDatabaseConnection readWithBlock:^(YapDatabaseReadTransaction *transaction) {
+            groupIndex = [self findGroupIndexOfThreadInteraction:quotedInteraction transaction:transaction];
+        }];
 
-                // For the findBlock, the "left operand" is the row that is passed,
-                // and the "right operand" is the desired range.
-                if (interaction.timestamp == quotedMessage.timestamp) {
+        if (!quotedInteraction || !groupIndex) {
+            DDLogError(@"%@ Failed to find quoted reply in group.", self.logTag);
+            return;
+        }
 
-                    return NSOrderedSame;
-                } else if (interaction.timestamp < quotedMessage.timestamp) {
-                    // NSOrderedAscending  : The left operand is smaller than the right operand.
-                    return NSOrderedAscending;
-                } else {
-                    // NSOrderedDescending : The left operand is greater than the right operand.
-                    return NSOrderedDescending;
-                }
-            }];
-        itemRange = [extension findRangeInGroup:self.thread.uniqueId using:viewFind];
-    }];
+        isInMappings = [self.messageMappings getRow:&indexRow
+                                            section:&indexSection
+                                           forIndex:groupIndex.unsignedIntegerValue
+                                            inGroup:self.thread.uniqueId];
+
+        if (!isInMappings) {
+            DDLogError(@"%@ Could not load quoted reply into mapping.", self.logTag);
+            return;
+        }
+    }
 
-    return itemRange;
+    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:(NSInteger)indexRow inSection:(NSInteger)indexSection];
+    [self.collectionView scrollToItemAtIndexPath:indexPath
+                                atScrollPosition:UICollectionViewScrollPositionTop
+                                        animated:YES];
+
+    // TODO: Highlight the quoted message?
 }
 
-- (nullable TSInteraction *)findInteractionInThreadByTimestamp:(uint64_t)timestamp
-                                                      authorId:(NSString *)authorId
-                                                   transaction:(YapDatabaseReadTransaction *)transaction
+- (nullable NSNumber *)findGroupIndexOfThreadInteraction:(TSInteraction *)interaction
+                                             transaction:(YapDatabaseReadTransaction *)transaction
 {
-    OWSAssert(timestamp > 0);
-    OWSAssert(authorId.length > 0);
+    OWSAssert(interaction);
+    OWSAssert(transaction);
 
-    NSString *localNumber = [TSAccountManager localNumber];
-    if (localNumber.length < 1) {
+    YapDatabaseAutoViewTransaction *_Nullable extension = [transaction extension:TSMessageDatabaseViewExtensionName];
+    if (!extension) {
+        OWSFail(@"%@ Couldn't load view.", self.logTag);
         return nil;
     }
 
-    NSArray<TSInteraction *> *interactions =
-        [TSInteraction interactionsWithTimestamp:timestamp ofClass:[TSMessage class] withTransaction:transaction];
-
-    TSInteraction *_Nullable result = nil;
-    for (TSInteraction *interaction in interactions) {
-        NSString *_Nullable messageAuthorId = nil;
-        if ([interaction isKindOfClass:[TSIncomingMessage class]]) {
-            TSIncomingMessage *incomingMessage = (TSIncomingMessage *)interaction;
-            messageAuthorId = incomingMessage.authorId;
-        } else if ([interaction isKindOfClass:[TSOutgoingMessage class]]) {
-            messageAuthorId = localNumber;
-        }
-        if (messageAuthorId.length < 1) {
-            OWSFail(@"%@ Message missing author id.", self.logTag);
-            continue;
-        }
-        if (![authorId isEqualToString:messageAuthorId]) {
-            continue;
-        }
-        if (![interaction.uniqueThreadId isEqualToString:self.thread.uniqueId]) {
-            continue;
-        }
-        if (result) {
-            // In case of collision, take the first.
-            DDLogError(@"%@ more than one matching interaction in thread.", self.logTag);
-            continue;
-        }
-        result = interaction;
+    NSUInteger groupIndex = 0;
+    BOOL foundInGroup =
+        [extension getGroup:nil index:&groupIndex forKey:interaction.uniqueId inCollection:TSInteraction.collection];
+    if (!foundInGroup) {
+        DDLogError(@"%@ Couldn't find quoted message in group.", self.logTag);
+        return nil;
     }
-    return result;
+    return @(groupIndex);
 }
 
 - (void)showMetadataViewForViewItem:(ConversationViewItem *)conversationItem
diff --git a/SignalMessaging/utils/ThreadUtil.h b/SignalMessaging/utils/ThreadUtil.h
index 12d25a510..e6cefa0d6 100644
--- a/SignalMessaging/utils/ThreadUtil.h
+++ b/SignalMessaging/utils/ThreadUtil.h
@@ -12,6 +12,7 @@ NS_ASSUME_NONNULL_BEGIN
 @class TSInteraction;
 @class TSThread;
 @class YapDatabaseConnection;
+@class YapDatabaseReadTransaction;
 
 @interface ThreadDynamicInteractions : NSObject
 
@@ -113,6 +114,13 @@ NS_ASSUME_NONNULL_BEGIN
 
 + (void)deleteAllContent;
 
+#pragma mark - Find Content
+
++ (nullable TSInteraction *)findInteractionInThreadByTimestamp:(uint64_t)timestamp
+                                                      authorId:(NSString *)authorId
+                                                threadUniqueId:(NSString *)threadUniqueId
+                                                   transaction:(YapDatabaseReadTransaction *)transaction;
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/SignalMessaging/utils/ThreadUtil.m b/SignalMessaging/utils/ThreadUtil.m
index 705dcfcb0..51c692099 100644
--- a/SignalMessaging/utils/ThreadUtil.m
+++ b/SignalMessaging/utils/ThreadUtil.m
@@ -668,6 +668,52 @@ NS_ASSUME_NONNULL_BEGIN
     DDLogInfo(@"%@ Deleted %zd/%zd objects from: %@", self.logTag, count, uniqueIds.count, collection);
 }
 
+#pragma mark - Find Content
+
+    + (nullable TSInteraction *)findInteractionInThreadByTimestamp : (uint64_t)timestamp authorId
+    : (NSString *)authorId threadUniqueId : (NSString *)threadUniqueId transaction
+    : (YapDatabaseReadTransaction *)transaction
+{
+    OWSAssert(timestamp > 0);
+    OWSAssert(authorId.length > 0);
+
+    NSString *localNumber = [TSAccountManager localNumber];
+    if (localNumber.length < 1) {
+        return nil;
+    }
+
+    NSArray<TSInteraction *> *interactions =
+        [TSInteraction interactionsWithTimestamp:timestamp ofClass:[TSMessage class] withTransaction:transaction];
+
+    TSInteraction *_Nullable result = nil;
+    for (TSInteraction *interaction in interactions) {
+        NSString *_Nullable messageAuthorId = nil;
+        if ([interaction isKindOfClass:[TSIncomingMessage class]]) {
+            TSIncomingMessage *incomingMessage = (TSIncomingMessage *)interaction;
+            messageAuthorId = incomingMessage.authorId;
+        } else if ([interaction isKindOfClass:[TSOutgoingMessage class]]) {
+            messageAuthorId = localNumber;
+        }
+        if (messageAuthorId.length < 1) {
+            OWSFail(@"%@ Message missing author id.", self.logTag);
+            continue;
+        }
+        if (![authorId isEqualToString:messageAuthorId]) {
+            continue;
+        }
+        if (![interaction.uniqueThreadId isEqualToString:threadUniqueId]) {
+            continue;
+        }
+        if (result) {
+            // In case of collision, take the first.
+            DDLogError(@"%@ more than one matching interaction in thread.", self.logTag);
+            continue;
+        }
+        result = interaction;
+    }
+    return result;
+}
+
 @end
 
 NS_ASSUME_NONNULL_END

From 6a07599e00ea4471912f04e775d223a8a294a146 Mon Sep 17 00:00:00 2001
From: Matthew Chen <matthew@signal.org>
Date: Tue, 10 Apr 2018 09:54:28 -0400
Subject: [PATCH 4/5] Respond to CR.

---
 SignalMessaging/utils/ThreadUtil.m            | 61 ++++++++++---------
 .../src/Messages/Interactions/TSInteraction.h |  2 +-
 2 files changed, 33 insertions(+), 30 deletions(-)

diff --git a/SignalMessaging/utils/ThreadUtil.m b/SignalMessaging/utils/ThreadUtil.m
index 51c692099..bb05900ba 100644
--- a/SignalMessaging/utils/ThreadUtil.m
+++ b/SignalMessaging/utils/ThreadUtil.m
@@ -672,46 +672,49 @@ NS_ASSUME_NONNULL_BEGIN
 
     + (nullable TSInteraction *)findInteractionInThreadByTimestamp : (uint64_t)timestamp authorId
     : (NSString *)authorId threadUniqueId : (NSString *)threadUniqueId transaction
-    : (YapDatabaseReadTransaction *)transaction
+    : (YapDatabaseReadTransaction *)transaction;
 {
     OWSAssert(timestamp > 0);
     OWSAssert(authorId.length > 0);
 
     NSString *localNumber = [TSAccountManager localNumber];
     if (localNumber.length < 1) {
+        OWSFail(@"%@ missing long number.", self.logTag);
         return nil;
     }
 
     NSArray<TSInteraction *> *interactions =
-        [TSInteraction interactionsWithTimestamp:timestamp ofClass:[TSMessage class] withTransaction:transaction];
-
-    TSInteraction *_Nullable result = nil;
-    for (TSInteraction *interaction in interactions) {
-        NSString *_Nullable messageAuthorId = nil;
-        if ([interaction isKindOfClass:[TSIncomingMessage class]]) {
-            TSIncomingMessage *incomingMessage = (TSIncomingMessage *)interaction;
-            messageAuthorId = incomingMessage.authorId;
-        } else if ([interaction isKindOfClass:[TSOutgoingMessage class]]) {
-            messageAuthorId = localNumber;
-        }
-        if (messageAuthorId.length < 1) {
-            OWSFail(@"%@ Message missing author id.", self.logTag);
-            continue;
-        }
-        if (![authorId isEqualToString:messageAuthorId]) {
-            continue;
-        }
-        if (![interaction.uniqueThreadId isEqualToString:threadUniqueId]) {
-            continue;
-        }
-        if (result) {
-            // In case of collision, take the first.
-            DDLogError(@"%@ more than one matching interaction in thread.", self.logTag);
-            continue;
-        }
-        result = interaction;
+        [TSInteraction interactionsWithTimestamp:timestamp
+                                          filter:^(TSInteraction *interaction) {
+                                              NSString *_Nullable messageAuthorId = nil;
+                                              if ([interaction isKindOfClass:[TSIncomingMessage class]]) {
+                                                  TSIncomingMessage *incomingMessage = (TSIncomingMessage *)interaction;
+                                                  messageAuthorId = incomingMessage.authorId;
+                                              } else if ([interaction isKindOfClass:[TSOutgoingMessage class]]) {
+                                                  messageAuthorId = localNumber;
+                                              }
+                                              if (messageAuthorId.length < 1) {
+                                                  return NO;
+                                              }
+
+                                              if (![authorId isEqualToString:messageAuthorId]) {
+                                                  return NO;
+                                              }
+                                              if (![interaction.uniqueThreadId isEqualToString:threadUniqueId]) {
+                                                  return NO;
+                                              }
+                                              return YES;
+                                          }
+                                 withTransaction:transaction];
+    if (interactions.count < 1) {
+        return nil;
     }
-    return result;
+    if (interactions.count > 1) {
+        // In case of collision, take the first.
+        DDLogError(@"%@ more than one matching interaction in thread.", self.logTag);
+        return nil;
+    }
+    return interactions[0];
 }
 
 @end
diff --git a/SignalServiceKit/src/Messages/Interactions/TSInteraction.h b/SignalServiceKit/src/Messages/Interactions/TSInteraction.h
index 1ea070928..67044af1f 100644
--- a/SignalServiceKit/src/Messages/Interactions/TSInteraction.h
+++ b/SignalServiceKit/src/Messages/Interactions/TSInteraction.h
@@ -45,7 +45,7 @@ typedef NS_ENUM(NSInteger, OWSInteractionType) {
 
 + (NSArray<TSInteraction *> *)interactionsWithTimestamp:(uint64_t)timestamp
                                                  filter:(BOOL (^_Nonnull)(TSInteraction *))filter
-                                        withTransaction:(YapDatabaseReadWriteTransaction *)transaction;
+                                        withTransaction:(YapDatabaseReadTransaction *)transaction;
 
 - (NSDate *)dateForSorting;
 - (uint64_t)timestampForSorting;

From 6ee74eaffc42bcb1e9ec51d2b6395dfd0d9477ef Mon Sep 17 00:00:00 2001
From: Matthew Chen <matthew@signal.org>
Date: Tue, 10 Apr 2018 15:56:13 -0400
Subject: [PATCH 5/5] Respond to CR.

---
 SignalMessaging/utils/ThreadUtil.m | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/SignalMessaging/utils/ThreadUtil.m b/SignalMessaging/utils/ThreadUtil.m
index bb05900ba..6437f3dc6 100644
--- a/SignalMessaging/utils/ThreadUtil.m
+++ b/SignalMessaging/utils/ThreadUtil.m
@@ -670,9 +670,10 @@ NS_ASSUME_NONNULL_BEGIN
 
 #pragma mark - Find Content
 
-    + (nullable TSInteraction *)findInteractionInThreadByTimestamp : (uint64_t)timestamp authorId
-    : (NSString *)authorId threadUniqueId : (NSString *)threadUniqueId transaction
-    : (YapDatabaseReadTransaction *)transaction;
++ (nullable TSInteraction *)findInteractionInThreadByTimestamp:(uint64_t)timestamp
+                                                      authorId:(NSString *)authorId
+                                                threadUniqueId:(NSString *)threadUniqueId
+                                                   transaction:(YapDatabaseReadTransaction *)transaction
 {
     OWSAssert(timestamp > 0);
     OWSAssert(authorId.length > 0);
@@ -712,9 +713,8 @@ NS_ASSUME_NONNULL_BEGIN
     if (interactions.count > 1) {
         // In case of collision, take the first.
         DDLogError(@"%@ more than one matching interaction in thread.", self.logTag);
-        return nil;
     }
-    return interactions[0];
+    return interactions.firstObject;
 }
 
 @end