refactor(handlers): split monolithic handlers.rs into modules

crates/xmedia-bot/src/handlers/inline.rs

@@ -0,0 +1,161 @@
+//! Inline query handling with a keystroke debounce: only a query stable for
+//! [`INLINE_DEBOUNCE`] triggers a fetch, and repeats are served by Telegram's
+//! inline cache instead of re-fetching.
+
+use super::log_key;
+use std::sync::LazyLock;
+use teloxide::RequestError;
+use teloxide::prelude::*;
+use teloxide::types::{
+    InlineQuery, InlineQueryResult, InlineQueryResultMpeg4Gif, InlineQueryResultPhoto,
+    InlineQueryResultVideo, ParseMode,
+};
+use x_media::media::Media;
+
+/// Debounce window for inline queries: Telegram fires an inline query on
+/// every keystroke, and each prefix of a pasted URL (e.g. `.../status/12`,
+/// `.../status/123`, ...) already matches the site patterns. Without a
+/// debounce every keystroke triggers a fetch (3 attempts!) of a half-typed
+/// post id. Only answer once the query has been stable for this long.
+const INLINE_DEBOUNCE: std::time::Duration = std::time::Duration::from_millis(800);
+
+/// Last seen inline query and whether it was already answered. Guards the
+/// debounce timer: a repeat of an answered query is served by Telegram's
+/// inline cache (see `cache_time`), not by another fetch.
+struct InlineDebounceState {
+    query: String,
+    answered: bool,
+}
+
+static INLINE_DEBOUNCE_STATE: LazyLock<parking_lot::Mutex<Option<InlineDebounceState>>> =
+    LazyLock::new(|| parking_lot::Mutex::new(None));
+
+pub async fn inline_query_handler(bot: Bot, query: InlineQuery) -> Result<(), RequestError> {
+    if query.query.is_empty() {
+        return respond(());
+    }
+    // Only run a fetch for something that is actually a supported post URL.
+    if x_media::site::cache_key(&query.query).is_none() {
+        return respond(());
+    }
+    // Debounce: record the query and answer only after it has been stable for
+    // INLINE_DEBOUNCE (the timer below). An already-answered repeat of the
+    // same query is left to Telegram's inline cache instead of re-fetching.
+    {
+        let mut state = INLINE_DEBOUNCE_STATE.lock();
+        if let Some(prev) = state.as_ref()
+            && prev.query == query.query
+            && prev.answered
+        {
+            return respond(());
+        }
+        *state = Some(InlineDebounceState {
+            query: query.query.clone(),
+            answered: false,
+        });
+    }
+    let query_text = query.query.clone();
+    tokio::spawn(async move {
+        tokio::time::sleep(INLINE_DEBOUNCE).await;
+        // Only the last query of a typing burst survives: earlier timers see
+        // the query changed and give up without answering.
+        {
+            let mut state = INLINE_DEBOUNCE_STATE.lock();
+            let Some(state) = state.as_mut() else {
+                return;
+            };
+            if state.query != query_text || state.answered {
+                return;
+            }
+            // Claim the answer so a repeat of the same query cannot start a
+            // second fetch; reset below when no answer was produced.
+            state.answered = true;
+        }
+        match answer_inline_query(bot, query).await {
+            Ok(true) => {}
+            // No results produced (or nothing to answer): let a repeat of the
+            // same query retry the fetch.
+            Ok(false) | Err(_) => {
+                let mut state = INLINE_DEBOUNCE_STATE.lock();
+                if let Some(state) = state.as_mut()
+                    && state.query == query_text
+                {
+                    state.answered = false;
+                }
+            }
+        }
+    });
+    respond(())
+}
+
+/// Fetches the post behind an inline query and answers it. The caller has
+/// already applied the debounce. Returns `true` when an answer was sent.
+async fn answer_inline_query(bot: Bot, query: InlineQuery) -> Result<bool, RequestError> {
+    log::debug!(
+        "inline query: {} [key={}]",
+        query.query,
+        log_key(&query.query)
+    );
+    match x_media::site::fetch(&query.query).await {
+        Ok(Some(fetched)) => {
+            let mut results: Vec<InlineQueryResult> = Vec::new();
+            // Inline results have the same 1024-char caption limit as regular
+            // messages; truncate once here for all items.
+            let caption = x_media::site::truncate_caption(&fetched.caption);
+            for (i, media) in fetched.media.iter().enumerate() {
+                let id = format!("{i}");
+                let Some(url) = url::Url::parse(media.url()).ok() else {
+                    continue;
+                };
+                let thumbnail = media
+                    .thumbnail_url()
+                    .and_then(|t| url::Url::parse(t).ok())
+                    .unwrap_or_else(|| url.clone());
+                let caption = caption.clone();
+                let result = match media {
+                    Media::Illustration { .. } => {
+                        // Inline photo results have their own (smaller) size
+                        // cap; use the reduced variant when one exists.
+                        let photo_url = media
+                            .smaller_url()
+                            .and_then(|u| url::Url::parse(u).ok())
+                            .unwrap_or_else(|| url.clone());
+                        InlineQueryResult::Photo(
+                            InlineQueryResultPhoto::new(id, photo_url, thumbnail)
+                                .caption(caption)
+                                .parse_mode(ParseMode::Html),
+                        )
+                    }
+                    Media::Video { .. } => InlineQueryResult::Video(
+                        InlineQueryResultVideo::new(
+                            id,
+                            url,
+                            "video/mp4".parse().expect("valid mime"),
+                            thumbnail,
+                            fetched.title.clone(),
+                        )
+                        .caption(caption)
+                        .parse_mode(ParseMode::Html),
+                    ),
+                    Media::Animated { .. } => InlineQueryResult::Mpeg4Gif(
+                        InlineQueryResultMpeg4Gif::new(id, url, thumbnail)
+                            .caption(caption)
+                            .parse_mode(ParseMode::Html),
+                    ),
+                };
+                results.push(result);
+            }
+            if !results.is_empty() {
+                // Explicit cache window: repeats of the same query within 5
+                // minutes are served by Telegram without hitting the bot.
+                bot.answer_inline_query(query.id, results)
+                    .cache_time(300)
+                    .await?;
+                return Ok(true);
+            }
+        }
+        Ok(None) => {}
+        Err(e) => log::error!("inline fetch {}: {e}", query.query),
+    }
+    Ok(false)
+}