Mark chat as noticed when receiving an outgoing message (#2861)

When there is an outgoing message in a chat, mark all older messages in this chat as seen.

Android already has a similar behavior, however, this led to the issue https://github.com/deltachat/deltachat-android/issues/2163 and should be changed back.

--

From the issue description at https://github.com/deltachat/deltachat-android/issues/2163, I implemented these fixes:
> Core should take care that if the last message in a chat is not fresh|noticed, no messages in the chat can be fresh. [...] Do this [...] in a function that's called at the end of fetch_new_messages(). Then dc_receive_imf() wouldn't get slower by this and we could re-use the same function for migration.

So, I didn't do this inside `dc_receive_imf()` in order not to make it take even longer. This obviously has the downside of higher complexity.

And I think we should implement this:
> On Androd, show the unread badge when unread!=0 again (see deltachat/deltachat-android@618af02). Then the user can see that there is a chat with an unread message and click it to get rid of it. 

because it shouldn't be the UI's job to decide whether an unread badge is shown, but the core's.

src/chat.rs

@@ -1,5 +1,6 @@
 //! # Chat module.
 
+use std::collections::HashMap;
 use std::convert::{TryFrom, TryInto};
 use std::str::FromStr;
 use std::time::{Duration, SystemTime};
@@ -21,6 +22,7 @@ use crate::constants::{
 };
 use crate::contact::{addr_cmp, Contact, Origin, VerifiedStatus};
 use crate::context::Context;
+use crate::dc_receive_imf::ReceivedMsg;
 use crate::dc_tools::{
     dc_create_id, dc_create_outgoing_rfc724_mid, dc_create_smeared_timestamp,
     dc_create_smeared_timestamps, dc_get_abs_path, dc_gm2local_offset, improve_single_line_input,
@@ -2145,6 +2147,75 @@ pub async fn marknoticed_chat(context: &Context, chat_id: ChatId) -> Result<()>
     Ok(())
 }
 
+/// Marks messages preceding outgoing messages as noticed.
+///
+/// In a chat, if there is an outgoing message, it can be assumed that all previous
+/// messages were noticed. So, this function takes a Vec of messages that were
+/// just received, and for all the outgoing messages, it marks all
+/// previous messages as noticed.
+pub(crate) async fn mark_old_messages_as_noticed(
+    context: &Context,
+    mut msgs: Vec<ReceivedMsg>,
+) -> Result<()> {
+    msgs.retain(|m| m.state.is_outgoing());
+    if msgs.is_empty() {
+        return Ok(());
+    }
+
+    let mut msgs_by_chat: HashMap<ChatId, ReceivedMsg> = HashMap::new();
+    for msg in msgs {
+        let chat_id = msg.chat_id;
+        if let Some(existing_msg) = msgs_by_chat.get(&chat_id) {
+            if msg.sort_timestamp > existing_msg.sort_timestamp {
+                msgs_by_chat.insert(chat_id, msg);
+            }
+        } else {
+            msgs_by_chat.insert(chat_id, msg);
+        }
+    }
+
+    let changed_chats = context
+        .sql
+        .transaction(|transaction| {
+            let mut changed_chats = Vec::new();
+            for (_, msg) in msgs_by_chat {
+                let changed_rows = transaction.execute(
+                    "UPDATE msgs
+            SET state=?
+          WHERE state=?
+            AND hidden=0
+            AND chat_id=?
+            AND timestamp<=?;",
+                    paramsv![
+                        MessageState::InNoticed,
+                        MessageState::InFresh,
+                        msg.chat_id,
+                        msg.sort_timestamp
+                    ],
+                )?;
+                if changed_rows > 0 {
+                    changed_chats.push(msg.chat_id);
+                }
+            }
+            Ok(changed_chats)
+        })
+        .await?;
+
+    if !changed_chats.is_empty() {
+        info!(
+            context,
+            "Marking chats as noticed because there are newer outgoing messages: {:?}",
+            changed_chats
+        );
+    }
+
+    for c in changed_chats {
+        context.emit_event(EventType::MsgsNoticed(c));
+    }
+
+    Ok(())
+}
+
 pub async fn get_chat_media(
     context: &Context,
     chat_id: ChatId,