pdfcraft/apps/pdfcraft-cli/src/main.rs

//! pdfcraft-cli — headless PdfCraft.
//!
//! ```text
//! pdfcraft-cli info   <file.pdf> [--password PW]            document summary as JSON
//! pdfcraft-cli render <file.pdf> --page N [--dpi 96] --out x.pam
//! pdfcraft-cli text   <file.pdf> [--page N]                  extracted text (pages separated by form feeds)
//! pdfcraft-cli edit   <in.pdf> --out out.pdf [--rotate 1,3:90] [--delete 2,4] [--move 5:1]
//!                       [--insert-blank 1] [--title T] [--author A] [--full]
//! pdfcraft-cli combine <a.pdf> <b.pdf> … --out combined.pdf
//! pdfcraft-cli extract <in.pdf> --pages 1,3,5 --out out.pdf
//! pdfcraft-cli split   <in.pdf> (--every N | --before 3,7) [--out-dir DIR]
//! pdfcraft-cli check  <files or dirs…> [--timeout 20] [--dpi 36] [--json out.json]
//! pdfcraft-cli tools                                       automation tools and their JSON Schemas
//! pdfcraft-cli run    <tool> [key=value …] [--root DIR] [--out image.png]
//! pdfcraft-cli run    --script steps.json [--root DIR]      [{"tool": "doc_open", "args": {…}}, …]
//! pdfcraft-cli mcp    [--root DIR]                          MCP server on stdin/stdout (opt-in)
//! pdfcraft-cli ui     --control FILE <method> [key=value …] [--out shot.png]
//!                                                            drive a running app started with --control FILE
//! ```
//!
//! `run` and `mcp` drive the same tool table (`pdfcraft-automation`). In `run`, values parse as
//! JSON when they can (`pages=[1,3]`, `degrees=90`) and are strings otherwise. A script runs its
//! steps in one session, so `doc_open` returns id 1, the next document id 2, and so on. A step's
//! `"out"` (like `--out`) saves its image there. With `--root DIR`, every path a tool or step
//! names, `"out"` included, must be inside DIR, and relative paths resolve inside it.
//!
//! The MCP server never starts on its own: it runs only when this command is launched (normally
//! by an agent configured to use it), talks only over stdio, and exits when stdin closes.
//!
//! `check` is the robustness harness: every file is opened, inspected and fully rendered in a
//! *separate child process* with a wall-clock timeout, so hangs, panics and aborts in any
//! dependency are observed and reported instead of taking the harness down.

#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]

use std::io::Write;
use std::path::{Path, PathBuf};
use std::process::{Command, ExitCode, Stdio};
use std::sync::Arc;
use std::time::{Duration, Instant};

use pdfcraft_render::{PageRenderer, RenderConfig, RenderRequest, RequestKind, inspect};

fn main() -> ExitCode {
    let args: Vec<String> = std::env::args().skip(1).collect();
    let result =
        match args.first().map(String::as_str) {
            Some("info") => info(&args[1..]),
            Some("render") => render(&args[1..]),
            Some("text") => text(&args[1..]),
            Some("edit") => edit(&args[1..]),
            Some("combine") => combine(&args[1..]),
            Some("extract") => extract(&args[1..]),
            Some("split") => split(&args[1..]),
            Some("check") => check(&args[1..]),
            Some("check-one") => check_one(&args[1..]),
            Some("tools") => tools(),
            Some("run") => run(&args[1..]),
            Some("ui") => ui(&args[1..]),
            #[cfg(feature = "mcp")]
            Some("mcp") => mcp(&args[1..]),
            Some("--version") => {
                println!("pdfcraft-cli {}", env!("CARGO_PKG_VERSION"));
                println!("Discord: {}  (help and feedback)", pdfcraft_engine::links::DISCORD);
                println!("Web:     {}", pdfcraft_engine::links::APP_PAGE);
                println!("Source:  {}", pdfcraft_engine::links::GITHUB);
                Ok(())
            }
            _ => Err("usage: pdfcraft-cli <info|render|text|edit|combine|extract|split|check|tools|run|mcp|ui> …  (see source header for options)\nhelp and feedback: https://discord.gg/artcraft"
                .into()),
        };
    match result {
        Ok(()) => ExitCode::SUCCESS,
        Err(e) => {
            eprintln!("pdfcraft-cli: {e}");
            ExitCode::FAILURE
        }
    }
}

fn flag<'a>(args: &'a [String], name: &str) -> Option<&'a str> {
    args.iter().position(|a| a == name).and_then(|i| args.get(i + 1)).map(String::as_str)
}

fn positional(args: &[String]) -> Vec<&str> {
    let mut out = Vec::new();
    let mut skip = false;
    for a in args {
        if skip {
            skip = false;
            continue;
        }
        if a.starts_with("--") {
            skip = true;
            continue;
        }
        out.push(a.as_str());
    }
    out
}

fn read(path: &str) -> Result<Arc<Vec<u8>>, String> {
    std::fs::read(path).map(Arc::new).map_err(|e| format!("{path}: {e}"))
}

fn info(args: &[String]) -> Result<(), String> {
    let path = *positional(args).first().ok_or("info: missing file")?;
    let info = inspect(read(path)?, flag(args, "--password")).map_err(|e| e.to_string())?;
    let json = serde_json::json!({
        "file": path,
        "pdf_version": info.pdf_version,
        "file_size": info.file_size,
        "pages": info.pages.len(),
        "first_page_pt": info.pages.first().map(|p| [p.width, p.height]),
        "title": info.title, "author": info.author, "producer": info.producer, "creator": info.creator,
        "encrypted": info.encrypted, "tagged": info.tagged, "javascript": info.has_javascript,
        "xfa": info.xfa.map(|x| match x { pdfcraft_render::Xfa::Static => "static", pdfcraft_render::Xfa::Dynamic => "dynamic" }),
        "bookmarks": info.outline.len(), "annotations": info.annotations.len(), "fields": info.fields.len(),
        "links": info.links.len(), "layers": info.layers.len(), "attachments": info.attachments.len(),
        "page_labels": info.pages.iter().take(8).map(|p| p.label.clone()).collect::<Vec<_>>(),
        "warnings": info.warnings,
    });
    println!("{}", serde_json::to_string_pretty(&json).unwrap_or_default());
    Ok(())
}

fn text(args: &[String]) -> Result<(), String> {
    let path = *positional(args).first().ok_or("text: missing file")?;
    let mut r = PageRenderer::new(read(path)?, RenderConfig { password: flag(args, "--password").map(Arc::from), ..Default::default() });
    let pages: Vec<usize> = match flag(args, "--page") {
        Some(p) => vec![p.parse::<usize>().map_err(|_| "bad --page")?.saturating_sub(1)],
        None => (0..r.page_count()).collect(),
    };
    let mut failed: Vec<usize> = Vec::new();
    for (n, p) in pages.iter().enumerate() {
        let out = r.render(RenderRequest { page: *p, kind: RequestKind::Text, tile: None, scale: 1.0, tag: 0 });
        if let Some(e) = out.error {
            eprintln!("page {}: {e}", p + 1);
            failed.push(p + 1);
            continue;
        }
        if n > 0 {
            println!("\u{c}");
        }
        println!("{}", out.text.map(|t| t.plain_text()).unwrap_or_default());
    }
    if failed.is_empty() {
        Ok(())
    } else {
        Err(format!("text: page(s) {} could not be read", failed.iter().map(usize::to_string).collect::<Vec<_>>().join(", ")))
    }
}

/// 1-based page list ("1,3,5") → 0-based indices.
fn page_list(s: &str) -> Result<Vec<usize>, String> {
    s.split(',').map(|p| p.trim().parse::<usize>().ok().filter(|n| *n > 0).map(|n| n - 1).ok_or(format!("bad page number {p:?}"))).collect()
}

/// Apply page and metadata edits through the engine and save (incrementally unless `--full`).
fn edit(args: &[String]) -> Result<(), String> {
    use pdfcraft_engine::{Edit, Session};
    let path = *positional(args).first().ok_or("edit: missing file")?;
    let out = flag(args, "--out").ok_or("edit: missing --out")?;
    let mut session = Session::new();
    let id = session.open(path, Some(path.to_string()), read(path)?, flag(args, "--password")).map_err(|e| e.to_string())?;
    let mut edits = Vec::new();
    let mut i = 0;
    while i < args.len() {
        let value = args.get(i + 1).map(String::as_str).unwrap_or("");
        match args[i].as_str() {
            "--rotate" => {
                let (pages, deg) = value.split_once(':').ok_or("--rotate PAGES:DEGREES")?;
                edits.push(Edit::RotatePages { pages: page_list(pages)?, degrees: deg.parse().map_err(|_| "bad degrees")? });
            }
            "--delete" => edits.push(Edit::DeletePages { pages: page_list(value)? }),
            "--move" => {
                let (pages, to) = value.split_once(':').ok_or("--move PAGES:TO")?;
                let to: usize = to.parse().map_err(|_| "bad target")?;
                edits.push(Edit::MovePages { pages: page_list(pages)?, to: to.saturating_sub(1) });
            }
            "--insert-blank" => {
                let at: usize = value.parse().map_err(|_| "bad position")?;
                edits.push(Edit::InsertBlankPage { at: at.saturating_sub(1), width: 612.0, height: 792.0 });
            }
            "--title" => edits.push(Edit::SetInfo { key: "Title".into(), value: value.into() }),
            "--author" => edits.push(Edit::SetInfo { key: "Author".into(), value: value.into() }),
            _ => {}
        }
        i += 1;
    }
    for e in edits {
        session.apply(id, e).map_err(|e| e.to_string())?;
    }
    let bytes = if args.iter().any(|a| a == "--full") { session.save_full_bytes(id) } else { session.save_bytes(id) }.map_err(|e| e.to_string())?;
    std::fs::write(out, bytes.as_slice()).map_err(|e| format!("{out}: {e}"))
}

fn file_stem(path: &str) -> String {
    Path::new(path).file_stem().map(|s| s.to_string_lossy().into_owned()).unwrap_or_else(|| path.to_string())
}

fn combine(args: &[String]) -> Result<(), String> {
    let out = flag(args, "--out").ok_or("combine: missing --out")?;
    let inputs = positional(args);
    if inputs.len() < 2 {
        return Err("combine: give at least two input files".into());
    }
    let sources = inputs.iter().map(|p| Ok((file_stem(p), read(p)?))).collect::<Result<Vec<_>, String>>()?;
    let bytes = pdfcraft_engine::Session::new().combine(&sources).map_err(|e| e.to_string())?;
    std::fs::write(out, bytes.as_slice()).map_err(|e| format!("{out}: {e}"))
}

fn extract(args: &[String]) -> Result<(), String> {
    let path = *positional(args).first().ok_or("extract: missing file")?;
    let out = flag(args, "--out").ok_or("extract: missing --out")?;
    let pages = page_list(flag(args, "--pages").ok_or("extract: missing --pages")?)?;
    let mut session = pdfcraft_engine::Session::new();
    let id = session.open(path, None, read(path)?, flag(args, "--password")).map_err(|e| e.to_string())?;
    let bytes = session.extract(id, &pages).map_err(|e| e.to_string())?;
    std::fs::write(out, bytes.as_slice()).map_err(|e| format!("{out}: {e}"))
}

fn split(args: &[String]) -> Result<(), String> {
    use pdfcraft_engine::SplitBy;
    let path = *positional(args).first().ok_or("split: missing file")?;
    let by = match (flag(args, "--every"), flag(args, "--before")) {
        (Some(n), None) => SplitBy::PageCount(n.parse().map_err(|_| "bad --every")?),
        (None, Some(list)) => SplitBy::Before(page_list(list)?),
        _ => return Err("split: give either --every N or --before PAGES".into()),
    };
    let dir = PathBuf::from(flag(args, "--out-dir").unwrap_or("."));
    let mut session = pdfcraft_engine::Session::new();
    let id = session.open(path, None, read(path)?, flag(args, "--password")).map_err(|e| e.to_string())?;
    let stem = file_stem(path);
    for (a, b, bytes) in session.split(id, &by).map_err(|e| e.to_string())? {
        let name = dir.join(if a == b { format!("{stem}-p{a}.pdf") } else { format!("{stem}-p{a}-{b}.pdf") });
        std::fs::write(&name, bytes.as_slice()).map_err(|e| format!("{}: {e}", name.display()))?;
        println!("{}", name.display());
    }
    Ok(())
}

fn render(args: &[String]) -> Result<(), String> {
    let path = *positional(args).first().ok_or("render: missing file")?;
    let page: usize = flag(args, "--page").unwrap_or("1").parse().map_err(|_| "bad --page")?;
    let dpi: f32 = flag(args, "--dpi").unwrap_or("96").parse().map_err(|_| "bad --dpi")?;
    let out = flag(args, "--out").ok_or("render: missing --out (.pam)")?;
    let mut r = PageRenderer::new(read(path)?, RenderConfig { password: flag(args, "--password").map(Arc::from), ..Default::default() });
    let p = r.render(RenderRequest { page: page.saturating_sub(1), kind: RequestKind::Pixels, tile: None, scale: dpi / 72.0, tag: 0 });
    if let Some(e) = p.error {
        return Err(e);
    }
    // PAM (netpbm RGB_ALPHA) keeps this tool dependency-free; convert with any image tool.
    let mut f = std::fs::File::create(out).map_err(|e| e.to_string())?;
    write!(f, "P7\nWIDTH {}\nHEIGHT {}\nDEPTH 4\nMAXVAL 255\nTUPLTYPE RGB_ALPHA\nENDHDR\n", p.width, p.height).map_err(|e| e.to_string())?;
    f.write_all(&p.rgba).map_err(|e| e.to_string())?;
    eprintln!("rendered page {page} at {dpi} dpi: {}×{} px in {} ms", p.width, p.height, p.millis);
    Ok(())
}

/// Child-process body for `check`: prints one JSON line.
fn check_one(args: &[String]) -> Result<(), String> {
    let path = *positional(args).first().ok_or("check-one: missing file")?;
    let dpi: f32 = flag(args, "--dpi").unwrap_or("36").parse().map_err(|_| "bad --dpi")?;
    let start = Instant::now();
    let bytes = read(path)?;
    let (status, pages, failed, detail, warnings) = match inspect(bytes.clone(), None) {
        Err(e) => (format!("open-error:{}", short(&e.to_string())), 0, 0, e.to_string(), 0),
        Ok(info) => {
            let mut r = PageRenderer::new(bytes, RenderConfig::default());
            let mut failed = Vec::new();
            for i in 0..info.pages.len().min(500) {
                let p = r.render(RenderRequest { page: i, kind: RequestKind::Pixels, tile: None, scale: dpi / 72.0, tag: 0 });
                if let Some(e) = r.render(RenderRequest { page: i, kind: RequestKind::Text, tile: None, scale: 1.0, tag: 0 }).error {
                    failed.push(format!("p{} text: {e}", i + 1));
                }
                if let Some(e) = p.error {
                    failed.push(format!("p{}: {e}", i + 1));
                }
            }
            let status = if failed.is_empty() { "ok".to_string() } else { "page-errors".to_string() };
            (status, info.pages.len(), failed.len(), failed.join(" | "), info.warnings.len())
        }
    };
    // `--edit` (fuzzing): also run our own object layer end to end, with no panic safety net,
    // so a panic in cos shows up as a crash of this process.
    if args.iter().any(|a| a == "--edit") {
        edit_round_trip(&std::fs::read(path).map_err(|e| e.to_string())?);
    }
    let line = serde_json::json!({ "file": path, "status": status, "pages": pages, "failed_pages": failed, "warnings": warnings,
        "ms": start.elapsed().as_millis() as u64, "detail": detail.chars().take(400).collect::<String>() });
    println!("{line}");
    Ok(())
}

/// Open with cos, touch every object, edit the catalog, save incrementally and in full (both
/// output styles), and reopen each result. Errors are fine; panics, hangs and aborts are bugs.
fn edit_round_trip(bytes: &[u8]) {
    use pdfcraft_cos::{Document, Object, SaveOptions, write_full, write_incremental};
    let Ok(mut doc) = Document::open(Arc::new(bytes.to_vec())) else { return };
    for num in doc.object_numbers().into_iter().take(20_000) {
        if let Ok(o) = doc.try_get(num)
            && let Object::Stream(s) = &*o
        {
            let _ = s.decoded();
        }
    }
    if let Some(root) = doc.root() {
        let _ = doc.update_dict(root, |d| d.set(b"PdfCraftFuzz".to_vec(), Object::Bool(true)));
    }
    let classic = SaveOptions { object_streams: false, ..SaveOptions::default() };
    for out in [write_incremental(&doc, &SaveOptions::default()), write_full(&doc, &SaveOptions::default()), write_full(&doc, &classic)]
        .into_iter()
        .flatten()
    {
        if let Ok(again) = Document::open(Arc::new(out)) {
            let _ = again.root().map(|r| again.get(r));
        }
    }
}

fn short(s: &str) -> String {
    s.split(|c: char| !c.is_alphanumeric()).filter(|w| !w.is_empty()).take(4).collect::<Vec<_>>().join("-").to_lowercase()
}

fn collect(paths: &[&str]) -> Vec<PathBuf> {
    let mut out = Vec::new();
    let mut stack: Vec<PathBuf> = paths.iter().map(PathBuf::from).collect();
    while let Some(p) = stack.pop() {
        if p.is_dir() {
            if let Ok(rd) = std::fs::read_dir(&p) {
                stack.extend(rd.flatten().map(|e| e.path()));
            }
        } else if p.extension().and_then(|e| e.to_str()).is_some_and(|e| e.eq_ignore_ascii_case("pdf")) {
            out.push(p);
        }
    }
    out.sort();
    out
}

fn check(args: &[String]) -> Result<(), String> {
    let files = collect(&positional(args));
    if files.is_empty() {
        return Err("check: no PDF files found".into());
    }
    let timeout = Duration::from_secs(flag(args, "--timeout").unwrap_or("20").parse().map_err(|_| "bad --timeout")?);
    let dpi = flag(args, "--dpi").unwrap_or("36").to_string();
    let exe = std::env::current_exe().map_err(|e| e.to_string())?;
    let mut results = Vec::new();
    let mut counts: std::collections::BTreeMap<String, usize> = Default::default();
    for (n, f) in files.iter().enumerate() {
        let r = run_child(&exe, f, &dpi, timeout);
        let status = r["status"].as_str().unwrap_or("?").to_string();
        *counts.entry(status.split(':').next().unwrap_or("?").to_string()).or_default() += 1;
        if status != "ok" {
            eprintln!(
                "[{}/{}] {status:<28} {}  {}",
                n + 1,
                files.len(),
                f.display(),
                r["detail"].as_str().unwrap_or("").chars().take(160).collect::<String>()
            );
        }
        results.push(r);
    }
    eprintln!("\nchecked {} files: {:?}", files.len(), counts);
    if let Some(out) = flag(args, "--json") {
        std::fs::write(out, serde_json::to_string_pretty(&results).unwrap_or_default()).map_err(|e| e.to_string())?;
    }
    Ok(())
}

fn run_child(exe: &Path, file: &Path, dpi: &str, timeout: Duration) -> serde_json::Value {
    let file_s = file.to_string_lossy().to_string();
    let child = Command::new(exe).args(["check-one", &file_s, "--dpi", dpi]).stdout(Stdio::piped()).stderr(Stdio::null()).spawn();
    let mut child = match child {
        Ok(c) => c,
        Err(e) => return serde_json::json!({ "file": file_s, "status": "harness-error", "detail": e.to_string() }),
    };
    let start = Instant::now();
    loop {
        match child.try_wait() {
            Ok(Some(status)) => {
                let mut out = String::new();
                if let Some(mut so) = child.stdout.take() {
                    use std::io::Read;
                    let _ = so.read_to_string(&mut out);
                }
                return match serde_json::from_str::<serde_json::Value>(out.trim()) {
                    Ok(v) => v,
                    Err(_) => serde_json::json!({ "file": file_s, "status": "crash", "detail": format!("child exited with {status}") }),
                };
            }
            Ok(None) if start.elapsed() > timeout => {
                let _ = child.kill();
                let _ = child.wait();
                return serde_json::json!({ "file": file_s, "status": "timeout", "detail": format!("exceeded {}s", timeout.as_secs()) });
            }
            Ok(None) => std::thread::sleep(Duration::from_millis(20)),
            Err(e) => return serde_json::json!({ "file": file_s, "status": "harness-error", "detail": e.to_string() }),
        }
    }
}

// ---- automation --------------------------------------------------------------------------------

fn automation(args: &[String]) -> Result<pdfcraft_automation::Automation, String> {
    let a = pdfcraft_automation::Automation::new();
    match flag(args, "--root") {
        Some(root) => a.with_root(root).map_err(|e| format!("--root {root}: {e}")),
        None => Ok(a),
    }
}

fn tools() -> Result<(), String> {
    let list: Vec<serde_json::Value> = pdfcraft_automation::tools()
        .iter()
        .map(|t| serde_json::json!({ "name": t.name, "description": t.description, "read_only": t.read_only, "command": t.command, "input_schema": t.input_schema }))
        .collect();
    println!("{}", serde_json::to_string_pretty(&list).unwrap_or_default());
    Ok(())
}

/// Print a tool's result: JSON as JSON; images go to `--out` (or are summarised). The image is
/// written like a tool's own output, so `--root` confines it too.
fn print_output(auto: &pdfcraft_automation::Automation, content: Vec<pdfcraft_automation::Content>, out: Option<&str>) -> Result<(), String> {
    for c in content {
        match c {
            pdfcraft_automation::Content::Json(v) => println!("{}", serde_json::to_string_pretty(&v).unwrap_or_default()),
            pdfcraft_automation::Content::Png { data, width, height } => match out {
                Some(path) => {
                    let written = auto.write_output(path, &data).map_err(|e| e.to_string())?;
                    println!("{}", serde_json::json!({ "image": written.to_string_lossy(), "width": width, "height": height }));
                }
                None => println!(
                    "{}",
                    serde_json::json!({ "image": "png", "width": width, "height": height, "bytes": data.len(), "hint": "pass --out file.png to save it" })
                ),
            },
        }
    }
    Ok(())
}

fn run(args: &[String]) -> Result<(), String> {
    let mut auto = automation(args)?;
    if let Some(script) = flag(args, "--script") {
        let text = std::fs::read_to_string(script).map_err(|e| format!("{script}: {e}"))?;
        let steps: Vec<serde_json::Value> = serde_json::from_str(&text).map_err(|e| format!("{script}: {e}"))?;
        for (i, step) in steps.iter().enumerate() {
            let tool = step["tool"].as_str().ok_or(format!("step {}: missing \"tool\"", i + 1))?;
            let content = auto.call(tool, &step["args"]).map_err(|e| format!("step {} ({tool}): {e}", i + 1))?;
            print_output(&auto, content, step["out"].as_str()).map_err(|e| format!("step {} ({tool}): {e}", i + 1))?;
        }
        return Ok(());
    }
    let tool = *positional(args).first().ok_or("run: missing tool name (see `pdfcraft-cli tools`)")?;
    let mut obj = serde_json::Map::new();
    for kv in positional(args).iter().skip(1) {
        let (k, v) = kv.split_once('=').ok_or(format!("run: expected key=value, got {kv:?}"))?;
        let value = serde_json::from_str(v).unwrap_or_else(|_| serde_json::Value::String(v.to_string()));
        obj.insert(k.to_string(), value);
    }
    let content = auto.call(tool, &serde_json::Value::Object(obj)).map_err(|e| e.to_string())?;
    print_output(&auto, content, flag(args, "--out"))
}

#[cfg(feature = "mcp")]
fn mcp(args: &[String]) -> Result<(), String> {
    let mut server = pdfcraft_automation::mcp::McpServer::new(automation(args)?);
    eprintln!("pdfcraft-cli: MCP server on stdio (protocol {}); close stdin to stop", pdfcraft_automation::mcp::PROTOCOL_VERSIONS[0]);
    server.serve(std::io::stdin().lock(), std::io::stdout().lock()).map_err(|e| e.to_string())
}

// ---- UI control channel client -----------------------------------------------------------------

/// One request to a running app's control channel (`pdfcraft --control FILE`).
fn ui(args: &[String]) -> Result<(), String> {
    use std::io::{BufRead, BufReader, Write as _};
    let file = flag(args, "--control").ok_or("ui: missing --control FILE (start the app with `pdfcraft --control FILE`)")?;
    let info: serde_json::Value =
        serde_json::from_str(&std::fs::read_to_string(file).map_err(|e| format!("{file}: {e}"))?).map_err(|e| format!("{file}: {e}"))?;
    let port = info["port"].as_u64().ok_or(format!("{file}: no port"))?;
    let token = info["token"].as_str().ok_or(format!("{file}: no token"))?;
    let pos = positional(args);
    let method = *pos.first().ok_or("ui: missing method (state, inspect, click, drag, type, key, command, commands, set, open, screenshot)")?;
    let method = if method.starts_with("ui.") { method.to_string() } else { format!("ui.{method}") };
    let mut params = serde_json::Map::new();
    for kv in pos.iter().skip(1) {
        let (k, v) = kv.split_once('=').ok_or(format!("ui: expected key=value, got {kv:?}"))?;
        params.insert(k.to_string(), serde_json::from_str(v).unwrap_or_else(|_| serde_json::Value::String(v.to_string())));
    }
    let stream = std::net::TcpStream::connect(("127.0.0.1", port as u16))
        .map_err(|e| format!("can't reach the app on port {port}: {e} (is it still running?)"))?;
    stream.set_read_timeout(Some(Duration::from_secs(40))).map_err(|e| e.to_string())?;
    let mut write = stream.try_clone().map_err(|e| e.to_string())?;
    let mut lines = BufReader::new(stream).lines();
    let mut rpc = |id: u64, method: &str, params: serde_json::Value| -> Result<serde_json::Value, String> {
        writeln!(write, "{}", serde_json::json!({ "jsonrpc": "2.0", "id": id, "method": method, "params": params })).map_err(|e| e.to_string())?;
        let line = lines.next().ok_or("the app closed the connection")?.map_err(|e| e.to_string())?;
        let reply: serde_json::Value = serde_json::from_str(&line).map_err(|e| e.to_string())?;
        match reply.get("error") {
            Some(e) => Err(e["message"].as_str().unwrap_or("error").to_string()),
            None => Ok(reply["result"].clone()),
        }
    };
    rpc(1, "auth", serde_json::json!({ "token": token }))?;
    let mut result = rpc(2, &method, serde_json::Value::Object(params))?;
    if let (Some(out), Some(data)) = (flag(args, "--out"), result.get("png_base64").and_then(|d| d.as_str())) {
        use base64::Engine as _;
        let png = base64::engine::general_purpose::STANDARD.decode(data).map_err(|e| e.to_string())?;
        std::fs::write(out, png).map_err(|e| format!("{out}: {e}"))?;
        result["png_base64"] = serde_json::json!(format!("written to {out}"));
    }
    println!("{}", serde_json::to_string_pretty(&result).unwrap_or_default());
    Ok(())
}