1 files changed, 343 insertions, 0 deletions
diff --git a/users/tazjin/tgsa/src/main.rs b/users/tazjin/tgsa/src/main.rs
new file mode 100644
index 000000000000..ed72569f9204
--- /dev/null
+++ b/users/tazjin/tgsa/src/main.rs
@@ -0,0 +1,343 @@
+use anyhow::{anyhow, Context, Result};
+use std::collections::HashMap;
+use std::sync::RwLock;
+use std::time::{Duration, Instant};
+
+#[derive(Clone, Debug, Eq, Hash, PartialEq)]
+struct TgLink {
+    username: String,
+    message_id: usize,
+}
+
+impl TgLink {
+    fn human_friendly_url(&self) -> String {
+        format!("t.me/{}/{}", self.username, self.message_id)
+    }
+
+    fn to_url(&self) -> String {
+        format!("https://t.me/{}/{}?embed=1", self.username, self.message_id)
+    }
+
+    fn parse(url: &str) -> Option<Self> {
+        let url = url.strip_prefix("/")?;
+        let parsed = url::Url::parse(url).ok()?;
+
+        if parsed.host()? != url::Host::Domain("t.me") {
+            // only t.me links are supported
+            return None;
+        }
+
+        let parts = parsed.path_segments()?.collect::<Vec<&str>>();
+        if parts.len() != 2 {
+            // only message links are supported
+            return None;
+        }
+
+        Some(TgLink {
+            username: parts[0].into(),
+            message_id: parts[1].parse().ok()?,
+        })
+    }
+}
+
+fn fetch_embed(link: &TgLink) -> Result<String> {
+    println!("fetching {}#{}", link.username, link.message_id);
+    let response = crimp::Request::get(&link.to_url())
+        .send()
+        .context("failed to fetch embed data")?
+        .as_string()
+        .context("failed to decode embed data")?
+        .error_for_status(|resp| {
+            anyhow!("telegram request failed: {} ({})", resp.body, resp.status)
+        })?;
+
+    Ok(response.body)
+}
+
+#[derive(Debug)]
+struct TgMessage {
+    author: String,
+    message: Option<String>,
+    photos: Vec<String>,
+    videos: Vec<String>,
+    has_audio: bool,
+}
+
+fn extract_photo_url(style: &str) -> Option<&str> {
+    let url_start = style.find("url('")? + 5;
+    let url_end = style.find("')")?;
+
+    Some(&style[url_start..url_end])
+}
+
+fn parse_tgmessage(embed: &str) -> Result<TgMessage> {
+    use scraper::{Html, Selector};
+
+    let doc = Html::parse_document(embed);
+
+    let author_sel = Selector::parse("a.tgme_widget_message_owner_name").unwrap();
+    let author = doc
+        .select(&author_sel)
+        .next()
+        .ok_or_else(|| anyhow!("failed to find message author"))?
+        .text()
+        .collect::<Vec<&str>>()
+        .concat();
+
+    let msg_sel = Selector::parse("div.tgme_widget_message_text.js-message_text").unwrap();
+
+    // The ElementRef::text() iterator does not yield newlines present
+    // in the message, so it is partially reimplemented here.
+    let message = if let Some(msg_elem) = doc.select(&msg_sel).next() {
+        use ego_tree::iter::Edge;
+        use scraper::node::Node;
+
+        let mut out = String::new();
+
+        for edge in &mut msg_elem.traverse() {
+            if let Edge::Open(node) = edge {
+                match node.value() {
+                    Node::Text(ref text) => out.push_str(&*text),
+                    Node::Element(elem) if elem.name() == "br" => out.push_str("\n"),
+                    _ => {}
+                }
+            }
+        }
+
+        Some(out)
+    } else {
+        // Not all Telegram messages have a textual message.
+        None
+    };
+
+    let photo_sel = Selector::parse("a.tgme_widget_message_photo_wrap").unwrap();
+    let mut photos = vec![];
+
+    for photo in doc.select(&photo_sel) {
+        if let Some(style) = photo.value().attr("style") {
+            if let Some(url) = extract_photo_url(style) {
+                photos.push(url.to_string())
+            }
+        }
+    }
+
+    let video_sel = Selector::parse("i.tgme_widget_message_video_thumb").unwrap();
+    let mut videos = vec![];
+
+    for video in doc.select(&video_sel) {
+        if let Some(style) = video.value().attr("style") {
+            if let Some(url) = extract_photo_url(style) {
+                videos.push(url.to_string())
+            }
+        }
+    }
+
+    let audio_sel = Selector::parse("audio.tgme_widget_message_voice.js-message_voice").unwrap();
+    let mut has_audio = false;
+    if doc.select(&audio_sel).next().is_some() {
+        has_audio = true;
+    }
+
+    Ok(TgMessage {
+        author,
+        message,
+        photos,
+        videos,
+        has_audio,
+    })
+}
+
+// create a permanent media url that tgsa can redirect if telegram
+// changes its upstream links.
+//
+// assumes that tgsa lives at tgsa.tazj.in (which it does)
+fn media_url(link: &TgLink, idx: usize) -> String {
+    format!(
+        "https://tgsa.tazj.in/img/{}/{}/{}",
+        link.username, link.message_id, idx
+    )
+}
+
+fn to_bbcode(link: &TgLink, msg: &TgMessage) -> String {
+    let mut out = String::new();
+
+    out.push_str(&format!("[quote=\"{}\"]\n", msg.author));
+
+    for video in 0..msg.videos.len() {
+        out.push_str(&format!("[url=\"{}\"]", link.to_url()));
+
+        // video thumbnail links are appended to the photos, hence the
+        // addition here
+        out.push_str(&format!(
+            "[img]{}[/img]",
+            media_url(link, video + msg.photos.len())
+        ));
+
+        out.push_str("[/url]\n");
+        out.push_str("[sub](Click thumbnail to open video)[/sub]\n")
+    }
+
+    for photo in 0..msg.photos.len() {
+        out.push_str(&format!("[timg]{}[/timg]\n", media_url(link, photo)));
+    }
+
+    if msg.has_audio {
+        out.push_str(&format!(
+            "[i]This message has audio attached. Go [url=\"{}\"]to Telegram[/url] to listen.[/i]",
+            link.to_url(),
+        ));
+    }
+
+    if let Some(message) = &msg.message {
+        out.push_str(message);
+    }
+
+    out.push_str("\n[/quote]\n");
+
+    out.push_str(&format!(
+        "[sub](from [url=\"{}\"]{}[/url], via [url=\"https://tgsa.tazj.in\"]tgsa[/url])[/sub]\n",
+        link.to_url(),
+        link.human_friendly_url(),
+    ));
+
+    out
+}
+
+// cache everything for one hour
+const CACHE_EXPIRY: Duration = Duration::from_secs(60 * 60);
+
+#[derive(Clone)]
+struct TgPost {
+    bbcode: String,
+    at: Instant,
+    media: Vec<String>,
+}
+
+type Cache = RwLock<HashMap<TgLink, TgPost>>;
+
+fn fetch_with_cache(cache: &Cache, link: &TgLink) -> Result<TgPost> {
+    if let Some(entry) = cache.read().unwrap().get(&link) {
+        if Instant::now() - entry.at < CACHE_EXPIRY {
+            println!("serving {}#{} from cache", link.username, link.message_id);
+            return Ok(entry.clone());
+        }
+    }
+
+    // limit concurrent fetching
+    // TODO(tazjin): per link?
+    let mut writer = cache.write().unwrap();
+
+    let embed = fetch_embed(&link)?;
+    let mut msg = parse_tgmessage(&embed)?;
+    let bbcode = to_bbcode(&link, &msg);
+
+    let mut media = vec![];
+    media.append(&mut msg.photos);
+    media.append(&mut msg.videos);
+
+    let post = TgPost {
+        bbcode,
+        media,
+        at: Instant::now(),
+    };
+
+    writer.insert(link.clone(), post.clone());
+
+    Ok(post)
+}
+
+fn handle_img_redirect(cache: &Cache, img_path: &str) -> Result<rouille::Response> {
+    // img_path:
+    //
+    // RWApodcast/113/1
+    // ^          ^   ^
+    // |          |   |
+    // |          |   image (0-indexed)
+    // |          post ID
+    // username
+
+    let img_parts: Vec<&str> = img_path.split("/").collect();
+
+    if img_parts.len() != 3 {
+        println!("invalid image link: {}", img_path);
+        return Err(anyhow!("not a valid image link: {}", img_path));
+    }
+
+    let link = TgLink {
+        username: img_parts[0].into(),
+        message_id: img_parts[1].parse().context("failed to parse message_id")?,
+    };
+
+    let img_idx: usize = img_parts[2].parse().context("failed to parse img_idx")?;
+    let post = fetch_with_cache(cache, &link)?;
+
+    if img_idx >= post.media.len() {
+        return Err(anyhow!(
+            "there is no {}. image in {}/{}",
+            img_idx,
+            link.username,
+            link.message_id
+        ));
+    }
+
+    Ok(rouille::Response::redirect_303(post.media[img_idx].clone()))
+}
+
+fn handle_tg_link(cache: &Cache, link: &TgLink) -> Result<rouille::Response> {
+    let post = fetch_with_cache(cache, link)?;
+    Ok(rouille::Response::text(post.bbcode))
+}
+
+fn main() {
+    crimp::init();
+
+    let cache: Cache = RwLock::new(HashMap::new());
+
+    rouille::start_server("0.0.0.0:8472", move |request| {
+        let response = loop {
+            if request.raw_url().starts_with("/img/") {
+                break handle_img_redirect(&cache, &request.raw_url()[5..]);
+            }
+
+            break match TgLink::parse(request.raw_url()) {
+                None => Ok(rouille::Response::text(
+                    r#"tgsa
+----
+
+this is a stupid program that lets you turn telegram message links
+into BBcode suitable for pasting on somethingawful dot com
+
+you can use it by putting a valid telegram message link in the url and
+waiting for some bbcode to show up.
+
+for example:
+
+  https://tgsa.tazj.in/https://t.me/RWApodcast/113
+
+yes, that looks stupid, but it works
+
+if you see this message and think you did the above correctly, you
+didn't. try again. idiot.
+
+pm me on the forums if this makes you mad or something.
+"#,
+                )),
+                Some(link) => handle_tg_link(&cache, &link),
+            };
+        };
+
+        match response {
+            Ok(resp) => resp,
+            Err(err) => {
+                println!("something failed: {}", err);
+                rouille::Response::text(format!(
+                    r#"ugh, something broke: {}
+
+nobody has been alerted about this and it has probably not been
+logged. pm me on the forums if you think it's important."#,
+                    err
+                ))
+            }
+        }
+    });
+}