feat: receive pre-messages and adapt download on demand

deltachat-ffi/deltachat.h

@@ -481,11 +481,11 @@ char*           dc_get_blobdir               (const dc_context_t* context);
  *                    0=use IMAP IDLE if the server supports it.
  *                    This is a developer option used for testing polling used as an IDLE fallback.
  * - `download_limit` = Messages up to this number of bytes are downloaded automatically.
- *                    For larger messages, only the header is downloaded and a placeholder is shown.
+ *                    For messages with large attachements, two messages are sent:
+ *                    a Pre-Message containing metadata and a Post-Message containing the attachment.
+ *                    Pre-Messages are always downloaded and show a placeholder message 
  *                    These messages can be downloaded fully using dc_download_full_msg() later.
- *                    The limit is compared against raw message sizes, including headers.
- *                    The actually used limit may be corrected
- *                    to not mess up with non-delivery-reports or read-receipts.
+ *                    Post-Messages are automatically downloaded if they are smaller than the download_limit.
  *                    0=no limit (default).
  *                    Changes affect future messages only.
  * - `protect_autocrypt` = Enable Header Protection for Autocrypt header.
@@ -4283,7 +4283,8 @@ char*             dc_msg_get_webxdc_info      (const dc_msg_t* msg);
 
 /**
  * Get the size of the file. Returns the size of the file associated with a
- * message, if applicable.
+ * message, if applicable. 
+ * If message is a pre-message, then this returns size of the to be downloaded file.
  *
  * Typically, this is used to show the size of document files, e.g. a PDF.
  *

deltachat-jsonrpc/src/api/types/message.rs

@@ -92,6 +92,8 @@ pub struct MessageObject {
 
     file: Option<String>,
     file_mime: Option<String>,
+    /// Returns the size of the file in bytes, if applicable.
+    /// If message is a pre-message, then this returns size of the to be downloaded file.
     file_bytes: u64,
     file_name: Option<String>,
 

deltachat-rpc-client/tests/test_something.py

@@ -11,7 +11,7 @@
 import pytest
 
 from deltachat_rpc_client import Contact, EventType, Message, events
-from deltachat_rpc_client.const import DownloadState, MessageState
+from deltachat_rpc_client.const import MessageState
 from deltachat_rpc_client.pytestplugin import E2EE_INFO_MSGS
 from deltachat_rpc_client.rpc import JsonRpcError
 

src/chat.rs

@@ -12,6 +12,7 @@ use std::time::Duration;
 use anyhow::{Context as _, Result, anyhow, bail, ensure};
 use chrono::TimeZone;
 use deltachat_contact_tools::{ContactAddress, sanitize_bidi_characters, sanitize_single_line};
+use humansize::{BINARY, format_size};
 use mail_builder::mime::MimePart;
 use serde::{Deserialize, Serialize};
 use strum_macros::EnumIter;
@@ -2735,10 +2736,10 @@ async fn prepare_send_msg(
     Ok(row_ids)
 }
 
-/// Renders the message or Full-Message and Pre-Message.
+/// Renders the Message or splits it into Post-Message and Pre-Message.
 ///
-/// Pre-Message is a small message with metadata which announces a larger Full-Message.
-/// Full messages are not downloaded in the background.
+/// Pre-Message is a small message with metadata which announces a larger Post-Message.
+/// Post-Messages are not downloaded in the background.
 ///
 /// If pre-message is not nessesary this returns a normal message instead.
 async fn render_mime_message_and_pre_message(
@@ -2755,9 +2756,14 @@ async fn render_mime_message_and_pre_message(
             > PRE_MSG_ATTACHMENT_SIZE_THRESHOLD;
 
     if needs_pre_message {
-        let mut mimefactory_full_msg = mimefactory.clone();
-        mimefactory_full_msg.set_as_full_message();
-        let rendered_msg = mimefactory_full_msg.render(context).await?;
+        info!(
+            context,
+            "Message is large and will be split into a pre- and a post-message.",
+        );
+
+        let mut mimefactory_post_msg = mimefactory.clone();
+        mimefactory_post_msg.set_as_post_message();
+        let rendered_msg = mimefactory_post_msg.render(context).await?;
 
         let mut mimefactory_pre_msg = mimefactory;
         mimefactory_pre_msg.set_as_pre_message_for(&rendered_msg);
@@ -2861,6 +2867,21 @@ pub(crate) async fn create_send_msg_jobs(context: &Context, msg: &mut Message) -
             }
         }?;
 
+    if let (post_msg, Some(pre_msg)) = (&rendered_msg, &rendered_pre_msg) {
+        info!(
+            context,
+            "Message Sizes: Pre-Message {}; Post-Message: {}",
+            format_size(pre_msg.message.len(), BINARY),
+            format_size(post_msg.message.len(), BINARY)
+        );
+    } else {
+        info!(
+            context,
+            "Message will be sent as normal message (no pre- and post message). Size: {}",
+            format_size(rendered_msg.message.len(), BINARY)
+        );
+    }
+
     if needs_encryption && !rendered_msg.is_encrypted {
         /* unrecoverable */
         message::set_msg_failed(

src/context.rs

@@ -591,7 +591,7 @@ impl Context {
                     convert_folder_meaning(self, folder_meaning).await?
                 {
                     connection
-                        .fetch_move_delete(self, &mut session, &watch_folder, folder_meaning)
+                        .fetch_move_delete(self, &mut session, true, &watch_folder, folder_meaning)
                         .await?;
                 }
             }
@@ -605,6 +605,12 @@ impl Context {
                     warn!(self, "Failed to update quota: {err:#}.");
                 }
             }
+
+            // OPTIONAL TODO: if time left start downloading messages
+            // while (msg = download_when_normal_starts) {
+            //  if not time_left {break;}
+            //  connection.download_message(msg) }
+            // }
         }
 
         info!(
@@ -1061,13 +1067,6 @@ impl Context {
                 .await?
                 .to_string(),
         );
-        res.insert(
-            "fail_on_receiving_full_msg",
-            self.sql
-                .get_raw_config("fail_on_receiving_full_msg")
-                .await?
-                .unwrap_or_default(),
-        );
 
         let elapsed = time_elapsed(&self.creation_time);
         res.insert("uptime", duration_to_str(elapsed));

src/context/context_tests.rs

@@ -297,7 +297,7 @@ async fn test_get_info_completeness() {
         "encrypted_device_token",
         "stats_last_update",
         "stats_last_old_contact_id",
-        "simulate_receive_imf_error",
+        "simulate_receive_imf_error", // only used in tests
     ];
     let t = TestContext::new().await;
     let info = t.get_info().await.unwrap();