add flag to get only info/system messages of chat

useful for creating an "audit log" view of a chat that helps to find
actions like who added/removed who quickly and without endless scrolling

deltachat-ffi/deltachat.h

@@ -1000,6 +1000,7 @@ dc_msg_t*       dc_get_draft                 (dc_context_t* context, uint32_t ch
 
 
 #define         DC_GCM_ADDDAYMARKER          0x01
+#define         DC_GCM_SYSTEM_ONLY           0x02
 
 
 /**
@@ -1018,6 +1019,7 @@ dc_msg_t*       dc_get_draft                 (dc_context_t* context, uint32_t ch
  * @param flags If set to DC_GCM_ADDDAYMARKER, the marker DC_MSG_ID_DAYMARKER will
  *     be added before each day (regarding the local timezone).  Set this to 0 if you do not want this behaviour.
  *     To get the concrete time of the marker, use dc_array_get_timestamp().
+ *     If set to DC_GCM_SYSTEM_ONLY, only system messages will be returned, can be combined with DC_GCM_ADDDAYMARKER.
  * @param marker1before An optional message ID.  If set, the id DC_MSG_ID_MARKER1 will be added just
  *   before the given ID in the returned array.  Set this to 0 if you do not want this behaviour.
  * @return Array of message IDs, must be dc_array_unref()'d when no longer used.

src/chat.rs

@@ -2,6 +2,7 @@
 
 use deltachat_derive::{FromSql, ToSql};
 use std::convert::TryFrom;
+use std::str::FromStr;
 use std::time::{Duration, SystemTime};
 
 use anyhow::Context as _;
@@ -1764,14 +1765,42 @@ pub async fn get_chat_msgs(
         }
     }
 
-    let process_row =
+    let process_row = if (flags & DC_GCM_SYSTEM_ONLY) != 0 {
-        |row: &rusqlite::Row| Ok((row.get::<_, MsgId>("id")?, row.get::<_, i64>("timestamp")?));
+        |row: &rusqlite::Row| {
+            // is_info logic taken from Message.is_info()
+            let params = row.get::<_, String>("param")?;
+            let (from_id, to_id) = (row.get::<_, u32>("from_id")?, row.get::<_, u32>("to_id")?);
+            let is_info_msg: bool = from_id == DC_CONTACT_ID_INFO as u32
+                || to_id == DC_CONTACT_ID_INFO as u32
+                || match Params::from_str(&params) {
+                    Ok(p) => {
+                        let cmd = p.get_cmd();
+                        cmd != SystemMessage::Unknown && cmd != SystemMessage::AutocryptSetupMessage
+                    }
+                    _ => false,
+                };
+
+            Ok((
+                row.get::<_, MsgId>("id")?,
+                row.get::<_, i64>("timestamp")?,
+                !is_info_msg,
+            ))
+        }
+    } else {
+        |row: &rusqlite::Row| {
+            Ok((
+                row.get::<_, MsgId>("id")?,
+                row.get::<_, i64>("timestamp")?,
+                false,
+            ))
+        }
+    };
     let process_rows = |rows: rusqlite::MappedRows<_>| {
         let mut ret = Vec::new();
         let mut last_day = 0;
         let cnv_to_local = dc_gm2local_offset();
         for row in rows {
-            let (curr_id, ts) = row?;
+            let (curr_id, ts, exclude_message): (MsgId, i64, bool) = row?;
             if let Some(marker_id) = marker1before {
                 if curr_id == marker_id {
                     ret.push(ChatItem::Marker1);
@@ -1787,7 +1816,9 @@ pub async fn get_chat_msgs(
                     last_day = curr_day;
                 }
             }
-            ret.push(ChatItem::Message { msg_id: curr_id });
+            if !exclude_message {
+                ret.push(ChatItem::Message { msg_id: curr_id });
+            }
         }
         Ok(ret)
     };
@@ -1815,6 +1846,25 @@ pub async fn get_chat_msgs(
                 process_rows,
             )
             .await
+    } else if (flags & DC_GCM_SYSTEM_ONLY) != 0 {
+        context
+            .sql
+            .query_map(
+                "SELECT m.id AS id, m.timestamp AS timestamp, m.param AS param, m.from_id AS from_id, m.to_id AS to_id
+               FROM msgs m
+              WHERE m.chat_id=?
+                AND m.hidden=0
+                AND (
+                    m.param GLOB \"*S=*\"
+                    OR m.from_id == 2
+                    OR m.to_id == 2
+                )
+              ORDER BY m.timestamp, m.id;",
+                paramsv![chat_id],
+                process_row,
+                process_rows,
+            )
+            .await
     } else {
         context
             .sql

src/constants.rs

@@ -99,6 +99,7 @@ pub const DC_GCL_ADD_ALLDONE_HINT: usize = 0x04;
 pub const DC_GCL_FOR_FORWARDING: usize = 0x08;
 
 pub const DC_GCM_ADDDAYMARKER: u32 = 0x01;
+pub const DC_GCM_SYSTEM_ONLY: u32 = 0x02;
 
 pub const DC_GCL_VERIFIED_ONLY: usize = 0x01;
 pub const DC_GCL_ADD_SELF: usize = 0x02;