108 lines
3.9 KiB
Rust
108 lines
3.9 KiB
Rust
//! Where MCP tool calls end up: a control-channel method call.
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use std::io::{BufRead, BufReader, Write};
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use std::net::{TcpStream, ToSocketAddrs};
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use std::time::Duration;
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use serde_json::{Value, json};
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/// Something that answers control-channel methods (`engine.execute`, `document.inspect`,
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/// `ui.pointer`, `ui.render`, …). See `deckcraft_ui_egui::control` for the full list.
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pub trait Backend {
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/// Call one method. `Ok` carries the `result`, `Err` the error message.
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fn call(&mut self, method: &str, params: Value) -> Result<Value, String>;
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/// True when a real UI is attached (`ui.screenshot`, `ui.click`, dialogs… work).
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fn has_ui(&self) -> bool;
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/// Short human description ("headless", "connected to 127.0.0.1:7979").
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fn describe(&self) -> String;
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}
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/// A running DeckCraft app, reached through its loopback control port.
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pub struct Remote {
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addr: String,
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conn: Option<(BufReader<TcpStream>, TcpStream)>,
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next_id: u64,
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}
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impl Remote {
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/// Connect to `addr` (`127.0.0.1:7979`), failing fast when nothing is listening.
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pub fn connect(addr: &str) -> std::io::Result<Self> {
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let mut r = Self { addr: addr.to_string(), conn: None, next_id: 1 };
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r.reconnect()?;
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Ok(r)
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}
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pub fn addr(&self) -> &str {
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&self.addr
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}
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fn reconnect(&mut self) -> std::io::Result<()> {
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self.conn = None;
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let mut last = std::io::Error::new(std::io::ErrorKind::NotFound, format!("cannot resolve {}", self.addr));
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for sa in self.addr.to_socket_addrs()? {
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match TcpStream::connect_timeout(&sa, Duration::from_millis(800)) {
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Ok(s) => {
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s.set_nodelay(true).ok();
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// The app answers within 60 s (its own timeout); leave headroom.
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s.set_read_timeout(Some(Duration::from_secs(90))).ok();
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let read = s.try_clone()?;
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self.conn = Some((BufReader::new(read), s));
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return Ok(());
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}
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Err(e) => last = e,
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}
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}
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Err(last)
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}
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fn roundtrip(&mut self, line: &str) -> std::io::Result<String> {
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if self.conn.is_none() {
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self.reconnect()?;
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}
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let Some((reader, writer)) = self.conn.as_mut() else {
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return Err(std::io::Error::new(std::io::ErrorKind::NotConnected, "not connected"));
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};
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writer.write_all(line.as_bytes())?;
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writer.write_all(b"\n")?;
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writer.flush()?;
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let mut reply = String::new();
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if reader.read_line(&mut reply)? == 0 {
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return Err(std::io::Error::new(std::io::ErrorKind::UnexpectedEof, "control channel closed"));
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}
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Ok(reply)
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}
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}
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impl Backend for Remote {
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fn call(&mut self, method: &str, params: Value) -> Result<Value, String> {
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let id = self.next_id;
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self.next_id += 1;
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let line = json!({"id": id, "method": method, "params": params}).to_string();
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// One retry with a fresh connection (the app may have restarted).
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let reply = match self.roundtrip(&line) {
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Ok(r) => r,
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Err(_) => {
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self.conn = None;
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self.roundtrip(&line).map_err(|e| {
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self.conn = None;
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format!("DeckCraft app at {} is not reachable: {e}", self.addr)
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})?
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}
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};
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let v: Value = serde_json::from_str(reply.trim()).map_err(|e| format!("bad reply from app: {e}"))?;
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if v.get("ok").and_then(Value::as_bool) == Some(true) {
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Ok(v.get("result").cloned().unwrap_or(Value::Null))
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} else {
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Err(v.get("error").and_then(Value::as_str).unwrap_or("unknown error").to_string())
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}
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}
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fn has_ui(&self) -> bool {
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true
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}
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fn describe(&self) -> String {
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format!("connected to the DeckCraft app at {}", self.addr)
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}
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}
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