fix: Filter DeleteMessage when computing the oldest loaded message [WPB-3506]

[atomrc]

WPB-3506 [Web] Conversation list is not updated with new messages

The bug

loading a conversation that contains a DeleteMessage that hasn't been seen yet by the user will not show messages after this deleted message

The problem

When messages arrives for a conversation that is not currently viewed by the user, we stack those messages in the messages property of the conversation.

When the user clicks on a conversation to view, these are the steps that are triggered to load the messages we want to display to them:

• we check what is the oldest message that we have in the messages list;
• starting from this oldest message, we load 30 messages from DB in reverse chronology (so messages that were sent before this oldest message that we have loaded)
• those loaded messages are added to the messages list
• the conversation can finally be showed to the user

This logic works pretty fine, except for DeleteMessage which can have a timestamp in the past.
Since delete messages timestamp are actually the timestamp of the message that was deleted.

An example

let's say we have a conversation between user1 and user2 with those messages:

• message1 by user2 (sent at timestamp 0)
• message2 by user2 (sent at timestamp 2)
• message3 by user2(sent at timestamp 3)

user1, is not currently looking at this conversation (so no messages are loaded into memory).

• user2, now deletes message1.
• user1 receives the delete event and store it in the messages list
• the oldest message that user1 has loaded is the delete message for message1 which has a timestamp of 0.
• user1 tries to load the conversation
• we try to load all messages in the conversation from timestamp 0

• we end-up not loading message2 and message3.

The fix

We computing the oldest message, we should not consider delete messages as we cannot trust their timestamp

[codecov]

Codecov Report

Merging #15686 (0e6c6d4) into dev (36d7231) will increase coverage by 0.00%.
The diff coverage is 88.88%.

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+ Hits         9940     9944    +4     
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  Partials     1250     1250           

[PatrykBuniX]

Amazing 🚀 Very nice explained, what a deep dive it was!

[tlebon]

great that you left some info for anyone reading this in the future