feat: add API to get similar chats

deltachat-ffi/deltachat.h

@@ -1334,6 +1334,20 @@ int             dc_get_msg_cnt               (dc_context_t* context, uint32_t ch
 int             dc_get_fresh_msg_cnt         (dc_context_t* context, uint32_t chat_id);
 
 
+/**
+ * Returns a list of similar chats.
+ *
+ * @warning This is an experimental API which may change or be removed in the future.
+ *
+ * @memberof dc_context_t
+ * @param context The context object as returned from dc_context_new().
+ * @param chat_id The ID of the chat for which to find similar chats.
+ * @return The list of similar chats.
+ *     On errors, NULL is returned.
+ *     Must be freed using dc_chatlist_unref() when no longer used.
+ */
+dc_chatlist_t*     dc_get_similar_chatlist   (dc_context_t* context, uint32_t chat_id);
+
 
 /**
  * Estimate the number of messages that will be deleted

deltachat-ffi/src/lib.rs

@@ -1260,6 +1260,30 @@ pub unsafe extern "C" fn dc_get_fresh_msg_cnt(
     })
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn dc_get_similar_chatlist(
+    context: *mut dc_context_t,
+    chat_id: u32,
+) -> *mut dc_chatlist_t {
+    if context.is_null() {
+        eprintln!("ignoring careless call to dc_get_similar_chatlist()");
+        return ptr::null_mut();
+    }
+    let ctx = &*context;
+
+    let chat_id = ChatId::new(chat_id);
+    match block_on(chat_id.get_similar_chatlist(ctx))
+        .context("failed to get similar chatlist")
+        .log_err(ctx)
+    {
+        Ok(list) => {
+            let ffi_list = ChatlistWrapper { context, list };
+            Box::into_raw(Box::new(ffi_list))
+        }
+        Err(_) => ptr::null_mut(),
+    }
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn dc_estimate_deletion_cnt(
     context: *mut dc_context_t,