Populate image/audio attachment body with a filename, not with text

Various clients (including newer versions of Element Web), do not like
it when the `body` field of the attachment is not a file name.

For images, a preview may not be shown and downloading the attachment
may suggest that the whole long text is used as a filename (which is odd).

There is value (improved accessibility, etc.)
in adding better descriptions (especially to generated images),
but given that it's currently problematic, I'm getting rid of it.
It's better and safer if we stick to using filenames.

src/controller/image/generation.rs

@@ -10,6 +10,7 @@ use crate::conversation::create_llm_conversation_for_matrix_thread;
 use crate::conversation::matrix::MatrixMessageProcessingParams;
 use crate::strings;
 use crate::{entity::MessageContext, Bot};
+use crate::controller::utils::mime::get_file_extension;
 
 // We may make this configurable (per room, etc.) in the future, but for now it's hardcoded.
 const STICKER_SIZE: &str = "256x256";
@@ -81,7 +82,7 @@ pub async fn handle_image(
             .await;
     }
 
-    let attachment_body_text = format!("Generated image based on: {}", actual_prompt);
+    let attachment_body_text = format!("generated-image.{}", get_file_extension(&response.mime_type));
 
     let mut event_content = matrix_link
         .media()
@@ -157,7 +158,7 @@ pub async fn handle_sticker(
         .instrument(span)
         .await?;
 
-    let attachment_body_text = format!("Generated sticker image based on: {}", original_prompt);
+    let attachment_body_text = format!("generated-sticker.{}", get_file_extension(&response.mime_type));
 
     let mut event_content = matrix_link
         .media()

src/controller/utils/mime.rs

@@ -0,0 +1,16 @@
+use mxlink::mime;
+
+pub fn get_file_extension(mime_type: &mime::Mime) -> String {
+    match (mime_type.type_(), mime_type.subtype()) {
+        (mime::AUDIO, mime::BASIC) => "au",
+        (mime::AUDIO, mime::MPEG) => "mp3",
+        (mime::AUDIO, mime::MP4) => "m4a",
+        (mime::AUDIO, mime::OGG) => "ogg",
+        (mime::IMAGE, mime::BMP) => "bmp",
+        (mime::IMAGE, mime::GIF) => "gif",
+        (mime::IMAGE, mime::JPEG) => "jpg",
+        (mime::IMAGE, mime::PNG) => "png",
+        (mime::IMAGE, mime::SVG) => "svg",
+        _ => "bin",
+    }.to_string()
+}

src/controller/utils/mod.rs

@@ -7,6 +7,7 @@ use crate::{
 
 pub mod agent;
 pub mod text_to_speech;
+pub(super) mod mime;
 
 pub async fn get_text_body_or_complain<'a>(
     bot: &Bot,

src/controller/utils/text_to_speech.rs

@@ -3,6 +3,7 @@ use mxlink::{MatrixLink, MessageResponseType};
 
 use tracing::Instrument;
 
+use crate::controller::utils::mime::get_file_extension;
 use crate::{
     agent::{provider::TextToSpeechParams, AgentInstance, AgentPurpose, ControllerTrait},
     entity::MessageContext,
@@ -117,7 +118,7 @@ async fn do_generate_and_send_tts_for_message(
         }
     };
 
-    let attachment_body_text = strings::text_to_speech::alternate_body_text();
+    let attachment_body_text = format!("generated-speech.{}", get_file_extension(&text_to_speech_result.mime_type));
 
     let event_content = matrix_link
         .media()

src/strings/text_to_speech.rs

@@ -1,7 +1,3 @@
-pub fn alternate_body_text() -> String {
-    "Generated speech from text".to_owned()
-}
-
 pub fn redaction_reason_done() -> &'static str {
     "Done with speech-to-text"
 }