feat: add Misskey (misskey.io) fetch support

Fourth site adapter: POST /api/notes/show, renote-aware caption and
media normalization, DriveFile type → Illustration/Animated/Video.
Empty thumbnailUrl strings filtered out in thumbnail_for.

crates/x-media/src/site/misskey/interface.rs

@@ -0,0 +1,384 @@
+//! Site adapter for misskey.io notes: URL pattern, API fetch and
+//! normalization into [`Fetched`] (see [`crate::site::Site`]).
+
+use super::model;
+use crate::media::Media;
+use crate::site::{FetchError, Fetched, RenderData, Site, SiteFuture};
+use html_escape::{encode_double_quoted_attribute, encode_text};
+use regex::Regex;
+use std::sync::LazyLock;
+
+const API_URL: &str = "https://misskey.io/api/notes/show";
+
+/// Registry entry for the misskey.io adapter (see [`crate::site::Site`]).
+pub struct MisskeySite;
+
+impl Site for MisskeySite {
+    fn id(&self) -> &'static str {
+        "misskey"
+    }
+
+    fn pattern(&self) -> &'static Regex {
+        &PATTERN
+    }
+
+    fn cache_key(&self, url: &str) -> Option<String> {
+        cache_key(url)
+    }
+
+    fn fetch_from_url<'a>(&'a self, url: &'a str) -> SiteFuture<'a, Fetched> {
+        Box::pin(async move { fetch_from_url(url).await })
+    }
+}
+
+pub static PATTERN: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"^(?:https?://)?misskey\.io/notes/([\w.\-~]+)").unwrap());
+
+pub fn enabled() -> bool {
+    true
+}
+
+pub async fn fetch_from_url(url: &str) -> Result<Fetched, FetchError> {
+    let caps = PATTERN.captures(url).ok_or(FetchError::NotFound)?;
+    let note_id = caps.get(1).ok_or(FetchError::NotFound)?.as_str();
+    let note = fetch(note_id).await?;
+    Ok(note.into())
+}
+
+/// Cache key for a misskey URL: `"misskey:<note id>"`. The prefix is the
+/// site id used for caption-format lookup and link-cache keys.
+pub fn cache_key(url: &str) -> Option<String> {
+    PATTERN
+        .captures(url)
+        .map(|caps| format!("misskey:{}", &caps[1]))
+}
+
+/// Misskey's fetch-retry policy: transient classes only. Not-found, blocked
+/// and parse failures are permanent.
+pub fn is_retryable(err: &FetchError) -> bool {
+    matches!(err, FetchError::Http(_) | FetchError::Transient(_))
+}
+
+/// misskey.io media hosts need no extra headers (verified: direct GET works).
+pub fn media_headers(_url: &str) -> Option<Vec<(&'static str, String)>> {
+    None
+}
+
+/// Fetches a note from misskey.io by id. The API answers client failures
+/// with HTTP 400 + `{"error":{"code":...}}` (NO_SUCH_NOTE → NotFound);
+/// everything else non-success is transient and retried by [`crate::site::fetch`].
+pub async fn fetch(note_id: &str) -> Result<model::Note, FetchError> {
+    let response = crate::site::CLIENT
+        .post(API_URL)
+        .json(&serde_json::json!({ "noteId": note_id }))
+        .send()
+        .await?;
+    let status = response.status();
+    if !status.is_success() {
+        return Err(match status.as_u16() {
+            400 => not_found_or_invalid(response).await,
+            _ => FetchError::Transient(format!("misskey status {status}")),
+        });
+    }
+    response.json().await.map_err(|e| FetchError::Site {
+        site: "misskey",
+        error: Box::new(e),
+    })
+}
+
+/// Maps a 400 response: NO_SUCH_NOTE is permanent NotFound, any other 400 is
+/// a site error (permanent — retrying a rejected request cannot succeed).
+async fn not_found_or_invalid(response: reqwest::Response) -> FetchError {
+    match response.json::<serde_json::Value>().await {
+        Ok(v) if v["error"]["code"] == "NO_SUCH_NOTE" => FetchError::NotFound,
+        _ => FetchError::Site {
+            site: "misskey",
+            error: "note rejected (invalid param or private note)".into(),
+        },
+    }
+}
+
+/// The note whose content matters: a renote shell has no text/files of its
+/// own — the embedded renote carries them.
+fn effective(note: &model::Note) -> &model::Note {
+    match &note.renote {
+        Some(renote) if note.files.is_empty() => renote,
+        _ => note,
+    }
+}
+
+impl From<model::Note> for Fetched {
+    fn from(note: model::Note) -> Self {
+        let note = &note;
+        let content = effective(note);
+        let url = format!("https://misskey.io/notes/{}", note.id);
+        let author = content
+            .user
+            .name
+            .as_deref()
+            .filter(|n| !n.is_empty())
+            .unwrap_or(&content.user.username)
+            .to_string();
+        let author_url = format!("https://misskey.io/@{}", content.user.username);
+        let cw = content.cw.as_deref().unwrap_or_default();
+        // Notes carry hashtags inline in the text (no structured tags array);
+        // a CW note gets the marker prefixed so recipients see the spoiler.
+        let mut title = cw.to_string();
+        if !cw.is_empty() && !title.ends_with(' ') {
+            title.push(' ');
+        }
+        title.push_str(content.text.as_deref().unwrap_or_default().trim());
+        let title = title.trim().to_string();
+
+        let caption = caption(&url, &author_url, &author, &title);
+        let sensitive = content.cw.is_some() || content.files.iter().any(|f| f.is_sensitive);
+        let media: Vec<Media> = content.files.iter().filter_map(media_from_file).collect();
+
+        Fetched {
+            source_url: url.clone(),
+            caption,
+            title: title.clone(),
+            media,
+            sensitive,
+            site_id: "misskey",
+            render_data: Some(RenderData {
+                url,
+                author: encode_text(&author).into_owned(),
+                author_url: author_url.clone(),
+                title: encode_text(&title).into_owned(),
+                tags: String::new(),
+            }),
+            _keep_alive: None,
+        }
+    }
+}
+
+fn caption(url: &str, author_url: &str, author: &str, text: &str) -> String {
+    let url = encode_double_quoted_attribute(url);
+    let author_url = encode_double_quoted_attribute(author_url);
+    let author = encode_text(author);
+    if text.is_empty() {
+        return format!("{url}\n<a href=\"{author_url}\">{author}</a>");
+    }
+    format!(
+        "{url}\n<a href=\"{author_url}\">{author}</a>: {text}",
+        text = encode_text(text),
+    )
+}
+
+/// Maps a Misskey DriveFile to a [`Media`] item; unknown/audio/other types
+/// are skipped (twitter's `_ => {}` precedent). GIF must be matched before
+/// the generic image arm.
+fn media_from_file(file: &model::DriveFile) -> Option<Media> {
+    let title = file.name.clone();
+    match file.mime_type.as_str() {
+        "image/gif" => Some(Media::Animated {
+            title,
+            url: file.url.clone(),
+            thumbnail_url: file.thumbnail_url.clone().unwrap_or_default(),
+        }),
+        mime if mime.starts_with("image/") => Some(Media::Illustration {
+            title,
+            url: file.url.clone(),
+            thumbnail_url: file.thumbnail_url.clone(),
+            fallback_url: None,
+        }),
+        mime if mime.starts_with("video/") => Some(Media::Video {
+            title,
+            url: file.url.clone(),
+            thumbnail_url: file.thumbnail_url.clone().unwrap_or_default(),
+        }),
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn note_json(json: serde_json::Value) -> model::Note {
+        serde_json::from_value(json).unwrap()
+    }
+
+    fn base_note() -> serde_json::Value {
+        serde_json::json!({
+            "id": "aotihl10lqrs015s",
+            "text": "hello",
+            "user": { "name": "ミロン", "username": "donyan47897", "host": null },
+            "files": []
+        })
+    }
+
+    #[test]
+    fn pattern_matches_misskey_note_urls() {
+        for url in [
+            "https://misskey.io/notes/aotihl10lqrs015s",
+            "http://misskey.io/notes/aotihl10lqrs015s",
+            "misskey.io/notes/aotihl10lqrs015s",
+        ] {
+            assert!(PATTERN.is_match(url), "{url}");
+        }
+        for url in [
+            "https://misskey.io/",
+            "https://misskey.io/@user",
+            "https://misskey.io/notes/",
+            "https://x.com/user/status/123",
+        ] {
+            assert!(!PATTERN.is_match(url), "{url}");
+        }
+    }
+
+    #[test]
+    fn cache_key_normalizes_variants() {
+        assert_eq!(
+            cache_key("https://misskey.io/notes/aotihl10lqrs015s"),
+            Some("misskey:aotihl10lqrs015s".to_string())
+        );
+        assert_eq!(x_media_site_id("misskey:abc"), "misskey");
+    }
+
+    fn x_media_site_id(key: &str) -> &'static str {
+        crate::site::site_id_from_key(key)
+    }
+
+    #[test]
+    fn from_json_image_file() {
+        let mut note = base_note();
+        note["files"] = serde_json::json!([{
+            "type": "image/webp",
+            "url": "https://media.misskeyusercontent.jp/io/a.webp",
+            "thumbnailUrl": "https://media.misskeyusercontent.jp/io/t.webp",
+            "isSensitive": true,
+            "name": "pic.webp"
+        }]);
+        let fetched: Fetched = note_json(note).into();
+        assert_eq!(
+            fetched.source_url,
+            "https://misskey.io/notes/aotihl10lqrs015s"
+        );
+        assert_eq!(fetched.site_id, "misskey");
+        assert_eq!(fetched.title, "hello");
+        assert!(fetched.sensitive);
+        assert_eq!(fetched.media.len(), 1);
+        match &fetched.media[0] {
+            Media::Illustration {
+                title,
+                url,
+                thumbnail_url,
+                fallback_url,
+            } => {
+                assert_eq!(title.as_deref(), Some("pic.webp"));
+                assert_eq!(url, "https://media.misskeyusercontent.jp/io/a.webp");
+                assert_eq!(
+                    thumbnail_url.as_deref(),
+                    Some("https://media.misskeyusercontent.jp/io/t.webp")
+                );
+                assert!(fallback_url.is_none());
+            }
+            other => panic!("expected illustration, got {other:?}"),
+        }
+    }
+
+    #[test]
+    fn from_json_gif_video_and_skip_audio() {
+        let mut note = base_note();
+        note["files"] = serde_json::json!([
+            { "type": "audio/mpeg", "url": "https://m/a.mp3", "isSensitive": false },
+            { "type": "image/gif", "url": "https://m/a.gif", "isSensitive": false },
+            { "type": "video/webm", "url": "https://m/a.webm", "isSensitive": false }
+        ]);
+        let fetched: Fetched = note_json(note).into();
+        assert_eq!(fetched.media.len(), 2);
+        assert!(
+            matches!(&fetched.media[0], Media::Animated { url, .. } if url == "https://m/a.gif")
+        );
+        assert!(matches!(&fetched.media[1], Media::Video { url, .. } if url == "https://m/a.webm"));
+        // No thumbnailUrl → empty string, not a broken URL.
+        match &fetched.media[1] {
+            Media::Video { thumbnail_url, .. } => assert_eq!(thumbnail_url, ""),
+            other => panic!("expected video, got {other:?}"),
+        }
+        assert!(!fetched.sensitive);
+    }
+
+    #[test]
+    fn from_json_cw_marks_sensitive_and_prefixes_title() {
+        let mut note = base_note();
+        note["cw"] = serde_json::json!("spoiler");
+        note["text"] = serde_json::json!("body");
+        let fetched: Fetched = note_json(note).into();
+        assert!(fetched.sensitive);
+        assert_eq!(fetched.title, "spoiler body");
+    }
+
+    #[test]
+    fn from_json_author_falls_back_to_username() {
+        let mut note = base_note();
+        note["user"] = serde_json::json!({ "name": null, "username": "donyan47897", "host": null });
+        let fetched: Fetched = note_json(note).into();
+        assert!(
+            fetched.caption.contains("donyan47897"),
+            "{}",
+            fetched.caption
+        );
+        assert!(fetched.caption.contains("https://misskey.io/@donyan47897"));
+    }
+
+    #[test]
+    fn from_json_renote_uses_embedded_content() {
+        let note = serde_json::json!({
+            "id": "shell0000000000",
+            "text": null,
+            "user": { "name": "shell", "username": "shelluser", "host": null },
+            "files": [],
+            "renote": {
+                "id": "inner000000000",
+                "text": "inner text",
+                "user": { "name": "inner", "username": "inneruser", "host": null },
+                "files": [
+                    { "type": "image/png", "url": "https://m/i.png", "isSensitive": false }
+                ]
+            }
+        });
+        let fetched: Fetched = note_json(note).into();
+        assert_eq!(fetched.title, "inner text");
+        assert_eq!(fetched.media.len(), 1);
+        // The source URL still points at the renote shell the user posted.
+        assert_eq!(
+            fetched.source_url,
+            "https://misskey.io/notes/shell0000000000"
+        );
+    }
+
+    #[test]
+    fn caption_layout_matches_bsky() {
+        let fetched: Fetched = note_json(base_note()).into();
+        assert_eq!(
+            fetched.caption,
+            "https://misskey.io/notes/aotihl10lqrs015s\n<a href=\"https://misskey.io/@donyan47897\">ミロン</a>: hello"
+        );
+    }
+
+    #[test]
+    fn caption_without_text_has_no_dangling_colon() {
+        let mut note = base_note();
+        note["text"] = serde_json::json!(null);
+        let fetched: Fetched = note_json(note).into();
+        assert_eq!(
+            fetched.caption,
+            "https://misskey.io/notes/aotihl10lqrs015s\n<a href=\"https://misskey.io/@donyan47897\">ミロン</a>"
+        );
+    }
+
+    #[tokio::test]
+    #[ignore = "live network: requires outbound HTTPS to misskey.io"]
+    async fn live_fetch_reference_note() {
+        let fetched = fetch_from_url("https://misskey.io/notes/aotihl10lqrs015s")
+            .await
+            .unwrap();
+        assert_eq!(fetched.site_id, "misskey");
+        assert_eq!(fetched.media.len(), 1);
+        assert!(fetched.sensitive);
+        assert!(!fetched.caption.is_empty());
+    }
+}

crates/x-media/src/site/misskey/mod.rs

@@ -0,0 +1,6 @@
+mod interface;
+mod model;
+
+pub use interface::{
+    MisskeySite, PATTERN, cache_key, enabled, fetch_from_url, is_retryable, media_headers,
+};

crates/x-media/src/site/misskey/model.rs

@@ -0,0 +1,35 @@
+use serde::Deserialize;
+
+#[derive(Deserialize, Debug)]
+pub(crate) struct Note {
+    pub(crate) id: String,
+    pub(crate) text: Option<String>,
+    #[serde(default)]
+    pub(crate) cw: Option<String>,
+    pub(crate) user: User,
+    #[serde(default)]
+    pub(crate) files: Vec<DriveFile>,
+    /// Embedded original note when this note is a renote; the shell's own
+    /// text/files are usually empty and the content lives here.
+    #[serde(default)]
+    pub(crate) renote: Option<Box<Note>>,
+}
+
+#[derive(Deserialize, Debug)]
+pub(crate) struct User {
+    pub(crate) name: Option<String>,
+    pub(crate) username: String,
+}
+
+#[derive(Deserialize, Debug)]
+pub(crate) struct DriveFile {
+    #[serde(rename = "type")]
+    pub(crate) mime_type: String,
+    pub(crate) url: String,
+    #[serde(default, rename = "thumbnailUrl")]
+    pub(crate) thumbnail_url: Option<String>,
+    #[serde(default, rename = "isSensitive")]
+    pub(crate) is_sensitive: bool,
+    #[serde(default)]
+    pub(crate) name: Option<String>,
+}

crates/x-media/src/site/mod.rs

@@ -1,8 +1,8 @@
 //! Site fetching dispatcher and unified result types.
 //!
-//! Dispatch order: twitter → bsky → pixiv. Each site module exports a
-//! `PATTERN`, `enabled()` and `fetch_from_url()`; a future site plugs in by
-//! adding one guarded entry in [`fetch_once`].
+//! Dispatch order: twitter → bsky → misskey → pixiv. Each site module
+//! exports a `PATTERN`, `enabled()` and `fetch_from_url()`; a future site
+//! plugs in by adding one guarded entry in [`fetch_once`].
 
 use std::future::Future;
 use std::pin::Pin;
@@ -14,6 +14,7 @@ use regex::Regex;
 use thiserror::Error;
 
 pub mod bsky;
+pub mod misskey;
 pub mod pixiv;
 pub mod twitter;
 
@@ -329,6 +330,7 @@ static SITES: LazyLock<Vec<Box<dyn Site>>> = LazyLock::new(|| {
     vec![
         Box::new(twitter::TwitterSite),
         Box::new(bsky::BskySite),
+        Box::new(misskey::MisskeySite),
         Box::new(pixiv::PixivSite),
     ]
 });
@@ -531,10 +533,10 @@ mod tests {
 
     #[test]
     fn registry_lists_all_sites_in_dispatch_order() {
-        assert_eq!(site_ids(), vec!["twitter", "bsky", "pixiv"]);
+        assert_eq!(site_ids(), vec!["twitter", "bsky", "misskey", "pixiv"]);
         // Enabled sites dispatch; unsupported URLs never match.
         assert!(find_site("https://x.com/u/status/1").is_some());
-        assert!(find_site("https://bsky.app/profile/u/post/3x").is_some());
+        assert!(find_site("https://misskey.io/notes/abc").is_some());
         assert!(find_site("https://example.com/x").is_none());
         // Cache keys are pattern-driven, independent of the enabled() gate
         // (pixiv is disabled in tests without PIXIV_REFRESH_TOKEN).

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

@@ -253,7 +253,7 @@ pub(crate) async fn execute_command(
                     bot,
                     message.chat.id.0,
                     message.id,
-                    "Unknown site. Use twitter, bsky or pixiv.",
+                    "Unknown site. Use twitter, bsky, pixiv or misskey.",
                 )
                 .await?;
                 return Ok(());
@@ -294,7 +294,7 @@ pub(crate) async fn execute_command(
                             bot,
                             message.chat.id.0,
                             message.id,
-                            "Unrecognized link. Use a twitter/x, pixiv or bsky post URL.",
+                            "Unrecognized link. Use a twitter/x, pixiv, bsky or misskey post URL.",
                         )
                         .await?;
                         return Ok(());
@@ -337,7 +337,7 @@ pub(crate) async fn execute_command(
                         bot,
                         message.chat.id.0,
                         message.id,
-                        "No enabled site matches this link (twitter/x, pixiv or bsky).",
+                        "No enabled site matches this link (twitter/x, pixiv, bsky or misskey).",
                     )
                     .await?;
                 }

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

@@ -135,7 +135,12 @@ pub fn extract_urls(message: &Message) -> Vec<String> {
 fn thumbnail_for(media: &Media) -> Option<String> {
     let url = media.url();
     if url.starts_with("http://") || url.starts_with("https://") {
-        media.thumbnail_url().map(str::to_string)
+        // An empty thumbnail string (misskey video/gif files without a
+        // thumbnailUrl) must not reach Telegram; let it generate its own.
+        media
+            .thumbnail_url()
+            .map(str::to_string)
+            .filter(|t| !t.is_empty())
     } else {
         None
     }