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//! `mecha chat` — an interactive session in the terminal.
use crate::{render, setup, GlobalOpts};
use anyhow::Result;
use mecha_core::agent::Conversation;
use mecha_core::message::{Message, Usage};
use mecha_core::session::{Record, RunConfig, Session, SessionMeta};
use rustyline::error::ReadlineError;
use rustyline::DefaultEditor;
#[derive(clap::Args, Debug)]
pub struct Args {
/// Continue a saved session by id or unique prefix.
#[arg(long)]
pub resume: Option<String>,
/// Don't write a transcript.
#[arg(long)]
pub no_session: bool,
}
pub async fn execute(global: &GlobalOpts, args: Args) -> Result<()> {
let prepared = setup::prepare(global, true).await?;
let session_dir = Session::default_dir()?;
// One conversation for the whole session: the taint travels with it, so a
// hostile page read on turn one still arms the interlock on turn five.
let mut convo = Conversation::new();
let mut session = None;
if let Some(id) = &args.resume {
let path = Session::find(&session_dir, id)?;
let (meta, prior) = Session::load(&path)?;
println!("resumed {} ({} messages)", meta.id, prior.messages.len());
convo = prior;
session = Some(Session { meta, path });
} else if !args.no_session {
session = Some(Session::create(
&session_dir,
SessionMeta {
id: Session::new_id(),
created_at: chrono::Utc::now(),
provider: prepared.provider_name.clone(),
model: prepared.model.clone(),
workspace: prepared.workspace.clone(),
title: None,
},
)?);
}
// On create and on resume both: a session picked up under different flags
// is exactly what this record exists to catch.
if let Some(s) = &session {
s.append(&Record::Config(RunConfig::of(
&prepared.agent,
&prepared.config,
&prepared.provider_name,
)))?;
// Staged outbox items point back at the session that drafted them.
if let Some(route) = &prepared.agent.context().outbox {
route.set_session_id(&s.meta.id);
}
// The interactive surface is one producer, `chat`, whichever session
// is live — that is what lets an overnight trigger address it without
// knowing which session tomorrow brings. A `--no-session` chat stays
// anonymous: no identity, no mailbox, no return address.
if let Some(mb) = &prepared.mailbox {
mb.attach("chat", &s.meta.id);
// Attended surfaces default to `hold`: say what is waiting
// rather than folding it in unasked.
if !mb.delivers() {
match mb.store.pending_for("chat") {
Ok(pending) if !pending.is_empty() => println!(
"{} message(s) waiting — `mecha msg list` to read them",
pending.len()
),
_ => {}
}
}
}
}
println!(
"mecha {} · {} ({}) · {} tools · {}",
mecha_core::VERSION,
prepared.model,
prepared.provider_name,
prepared.agent.registry().len(),
prepared.workspace.display()
);
println!("/help for commands, Ctrl-D to exit.\n");
let mut editor = DefaultEditor::new()?;
// History survives the process, and it lives beside the transcripts on
// purpose: the sessions directory is owner-only, and a typed prompt
// deserves the same protection as the transcript that records it.
// Best-effort throughout — a first run has no file, and losing history
// must never lose the chat.
let history_path = {
let _ = mecha_core::create_private_dir(&session_dir);
session_dir.join("chat_history")
};
let _ = editor.load_history(&history_path);
let mut total = Usage::default();
loop {
let line = match editor.readline("› ") {
Ok(line) => line,
// Ctrl-C abandons the line; Ctrl-D ends the session.
Err(ReadlineError::Interrupted) => continue,
Err(ReadlineError::Eof) => break,
Err(e) => return Err(e.into()),
};
let input = line.trim();
if input.is_empty() {
continue;
}
let _ = editor.add_history_entry(input);
// Saved per line rather than at exit, so a killed process keeps what
// was typed before it died.
if history_path.exists() {
let _ = editor.append_history(&history_path);
} else {
let _ = editor.save_history(&history_path);
}
if let Some(command) = input.strip_prefix('/') {
match handle_command(command, &prepared, &mut convo, &total, session.as_ref()) {
Flow::Continue => continue,
Flow::Quit => break,
}
}
let user = Message::user(input);
convo.push(user.clone());
if let Some(s) = &session {
s.append(&Record::Message(user))?;
}
let recorded = convo.messages.clone();
let (tx, rx) = tokio::sync::mpsc::unbounded_channel();
let renderer = render::spawn(
rx,
render::RenderOpts {
verbose: global.verbose,
quiet: false,
},
);
let result = crate::interrupt::run_interruptible(
&prepared.agent,
prepared.agent.context(),
&mut convo,
Some(tx.clone()),
)
.await;
drop(tx);
let _ = renderer.await;
println!();
match result {
Ok(outcome) => {
total.add(&outcome.usage);
if let Some(s) = &session {
s.record_run(&recorded, &convo.messages)?;
// Persist what the conversation now knows, or resuming it
// launders the taint exactly as a turn boundary used to.
s.append(&Record::Taint(convo.taint))?;
}
}
Err(e) => {
eprintln!("error: {e:#}");
// Drop the turn so a failed request doesn't leave a dangling
// user message that the next request would resend. Restored
// from the snapshot rather than truncated: a mid-run
// compaction leaves the list shorter than it started, and
// truncating *that* keeps the dangling message this exists
// to drop.
convo.messages = recorded;
convo.messages.pop();
}
}
}
if let Some(s) = &session {
println!("\nsession {} · {}", s.meta.id, render::format_usage(&total));
if let Some(mb) = &prepared.mailbox {
mb.detach(&s.meta.id);
}
let cx = prepared.agent.context();
cx.hooks
.session_end(&s.meta.id, &s.path, &cx.tools.workspace)
.await;
}
Ok(())
}
enum Flow {
Continue,
Quit,
}
fn handle_command(
command: &str,
prepared: &setup::Prepared,
convo: &mut Conversation,
total: &Usage,
session: Option<&Session>,
) -> Flow {
let (name, _rest) = command.split_once(' ').unwrap_or((command, ""));
match name {
"exit" | "quit" | "q" => return Flow::Quit,
"help" | "h" => {
println!(
" /tools list available tools\n\
\x20 /model show the active model and provider\n\
\x20 /usage tokens used this session\n\
\x20 /clear forget the conversation so far\n\
\x20 /session show the transcript path\n\
\x20 /exit quit"
);
}
"tools" => {
for tool in prepared.agent.registry().iter() {
println!(
" {:<28} {}",
tool.name(),
tool.description().lines().next().unwrap_or("")
);
}
}
"model" => println!(" {} ({})", prepared.model, prepared.provider_name),
"usage" => println!(" {}", render::format_usage(total)),
"clear" => {
// A new conversation, taint included: nothing the old one read is
// in context any more, so nothing it read should still apply.
*convo = Conversation::new();
println!(" conversation cleared");
}
"session" => match session {
Some(s) => println!(" {} — {}", s.meta.id, s.path.display()),
None => println!(" not recording (--no-session)"),
},
other => println!(" unknown command /{other} — try /help"),
}
Flow::Continue
}