cctop 0.9.0

//! `cctop why` — why a session's row says what it says.
//!
//! Every other output is a verdict. The table shows a dot, `-j` shows
//! `"running": false`, and neither says how that was reached — so a row that is
//! wrong is a row with nothing to argue with. This prints the reasoning:
//! every agent process on the machine, the session each was given to, and the
//! rule that gave it.
//!
//! It exists because of one bug worth remembering. `claude --resume X` does not
//! reopen X; it forks, writing a new transcript that records X as the id it was
//! launched from. cctop read the command line literally, so the live agent was
//! attributed to a conversation nobody was in — the running session showed as
//! stopped and its CPU landed on a dead row. Diagnosing that took a process
//! table, `/proc/<pid>/cwd`, and a JSONL field nobody had documented. It should
//! have taken one command.
//!
//! Read-only: it walks sessions and processes and prints. Nothing here can
//! change a session, a file, or a process.

use crate::loader::Loader;
use crate::pricing::Plan;

pub const HELP: &str = "\
cctop why — why cctop thinks a session is running, or is not

USAGE:
  cctop why [SESSION_ID]

With no argument it explains every process it can see. With one, it explains
that session: whether a process was matched to it, which one, and by which rule
— and, when nothing was, what else claimed the processes nearby.

A session id may be shortened, as long as it is unambiguous.
";

pub fn run(argv: &[String]) -> i32 {
    if argv.iter().any(|a| a == "-h" || a == "--help") {
        print!("{HELP}");
        return 0;
    }
    let wanted = argv.iter().find(|a| !a.starts_with('-'));

    let mut loader = Loader::new();
    // A full walk, because the question is about attribution and attribution is
    // done over every session on the machine — a subset would change the answer.
    let sessions = loader.load(Plan::Retail);
    let attributions = loader.attributions().to_vec();

    let matching: Vec<_> = match wanted {
        None => sessions.iter().collect(),
        Some(id) => sessions
            .iter()
            .filter(|s| s.session_id.starts_with(id.as_str()))
            .collect(),
    };
    if let Some(id) = wanted
        && matching.is_empty()
    {
        println!("No session here starts with {id}.");
        println!("`cctop -l` lists them; `cctop doctor` says where they are read from.");
        return 1;
    }

    println!("{} agent process(es) attributed:", attributions.len());
    if attributions.is_empty() {
        println!("  (none — nothing on this machine looks like a running agent)");
    }
    for a in &attributions {
        println!("\n  pid {} → {}", a.pid, a.key);
        println!("    rule    {}", a.rule);
        if !a.matched.is_empty() {
            println!("    matched {}", a.matched);
        }
        if !a.argv.is_empty() {
            println!("    argv    {}", crate::util::truncate(&a.argv, 100));
        }
    }

    println!();
    for session in matching {
        let key = session.key();
        let mine: Vec<_> = attributions.iter().filter(|a| a.key == key).collect();
        let running = session.is_running();
        println!("{key}");
        println!(
            "  running   {}",
            match (running, session.process.is_some()) {
                (true, true) => "yes, a process was matched to it",
                // Cursor and Cowork have no per-session process; a growing
                // transcript is the only signal there is.
                (true, false) => "yes, inferred from a transcript still growing",
                (false, _) => "no",
            }
        );
        if session.launched_as() != session.session_id {
            // The half that explains most wrong answers.
            println!(
                "  resumed   this transcript was forked from {}, which is the id \
                 its process names",
                session.launched_as()
            );
        }
        println!("  last      {}", session.last_active);
        println!("  cwd       {}", session.label_source);
        for a in &mine {
            println!("  pid {}     {}", a.pid, a.rule);
        }
        if mine.is_empty() && !running {
            // Say what else took the processes in this directory, which is the
            // next question every time.
            let neighbours: Vec<_> = attributions
                .iter()
                .filter(|a| a.matched == session.label_source || a.key != key)
                .take(3)
                .collect();
            match neighbours.is_empty() {
                true => println!("  nothing on this machine looked like its process"),
                false => {
                    println!("  no process was matched to it. What took the others:");
                    for a in neighbours {
                        println!("    pid {} → {} ({})", a.pid, a.key, a.rule);
                    }
                }
            }
        }
        println!();
    }
    0
}