effectcraft/crates/engine/src/cmd/effect.rs

//! Effect menu and Effect Controls gestures.

use effectcraft_project::build::Ids;
use effectcraft_project::{GroupKind, Layer, LayerId, PropGroup, Uid};
use effectcraft_time::Tick;
use serde_json::{Value, json};

use super::{CommandSpec, b_p, bad, f_p, has_layers, layer_mut, layers_p, str_p};
use crate::{EngineError, Result, Session, cmd};

/// `effect.plugins.list`: the registered plug-in effects (WebAssembly or Rust).
fn plugins_list(s: &mut Session, _: &Value) -> Result<Value> {
    use effectcraft_effects::plugin;
    let list: Vec<Value> = plugin::plugins()
        .into_iter()
        .map(|spec| {
            let p = plugin::plugin(spec.id);
            let m = p.as_ref().map(|p| p.manifest().clone());
            json!({
                "id": spec.id,
                "name": spec.name,
                "category": spec.category,
                "version": m.as_ref().map(|m| m.version.clone()),
                "author": m.as_ref().map(|m| m.author.clone()),
                "description": m.as_ref().map(|m| m.description.clone()),
                "source": p.map(|p| p.source()),
                "error": plugin::plugin_error(spec.id),
                "params": spec.params.iter().map(|p| p.id).collect::<Vec<_>>(),
            })
        })
        .collect();
    Ok(json!({"api": plugin::PLUGIN_API_VERSION, "wasm": s.plugin_loader.is_some(), "helpers": s.helpers.is_some(), "plugins": list}))
}

/// `effect.plugins.load`: load WebAssembly effect plug-ins (a file, or every `.wasm` in a
/// folder) through the host's loader ([`Session::plugin_loader`]).
fn plugins_load(s: &mut Session, p: &Value) -> Result<Value> {
    let c = "effect.plugins.load";
    let loader = s.plugin_loader.ok_or_else(|| EngineError::Other("WebAssembly effect plug-ins are not available in this build".into()))?;
    let files: Vec<String> = match (str_p(p, "path"), str_p(p, "folder")) {
        (Some(path), _) => vec![path.to_string()],
        (None, Some(dir)) => {
            let mut v: Vec<String> = std::fs::read_dir(dir)
                .map_err(|e| bad(c, format!("cannot list {dir}: {e}")))?
                .flatten()
                .map(|e| e.path())
                .filter(|p| p.extension().is_some_and(|x| x.eq_ignore_ascii_case("wasm")))
                .map(|p| p.to_string_lossy().to_string())
                .collect();
            v.sort();
            v
        }
        _ => return Err(bad(c, "give `path` or `folder`")),
    };
    let (mut loaded, mut errors) = (vec![], vec![]);
    for f in &files {
        let r = s.services.read_file(f).map_err(|e| format!("cannot read {f}: {e}")).and_then(|bytes| loader(&bytes, f));
        match r {
            Ok(v) => loaded.push(v),
            Err(e) => errors.push(json!({"path": f, "error": e})),
        }
    }
    if str_p(p, "path").is_some()
        && let Some(e) = errors.first()
    {
        return Err(EngineError::Other(format!("{}: {}", files[0], e["error"].as_str().unwrap_or("failed"))));
    }
    if !loaded.is_empty() {
        s.toast(format!("Loaded {} effect plug-in(s)", loaded.len()));
    }
    Ok(json!({"loaded": loaded, "errors": errors}))
}

/// The settings-folder name the desktop app scans for WebAssembly effect plug-ins on start.
/// The scan uses this constant ([`apps/effectcraft/src/main.rs`]), so the two cannot drift.
pub const PLUGINS_DIR: &str = "Plug-ins";

/// The most one installed file may be: a plug-in is a compiled effect, a panel is script text.
/// Above this the install refuses rather than reading an unbounded file into memory and copying
/// it into a folder the app loads at every start.
const MAX_INSTALL_BYTES: u64 = 64 << 20;

/// `effect.plugins.install`: install WebAssembly effect plug-ins so they load on every start,
/// not only in this session (Load Effect Plug-in keeps the file where it is and just loads it).
/// `path` installs one `.wasm`; `folder` installs a bundle in one go: every `.wasm` at its top
/// level is copied into the Plug-ins folder and every `.jsx` becomes a ScriptUI panel. What
/// installs also loads in this session at once, so the effect menu has it immediately. A `.wasm`
/// that fails to load is not copied: a broken plug-in must not fail every start.
fn plugins_install(s: &mut Session, p: &Value) -> Result<Value> {
    let c = "effect.plugins.install";
    let loader = s.plugin_loader.ok_or_else(|| EngineError::Other("WebAssembly effect plug-ins are not available in this build".into()))?;
    let cfg = s.config.clone().ok_or_else(|| EngineError::Other("this session has no settings folder to install plug-ins into".into()))?;
    let root = cfg.dir().ok_or_else(|| EngineError::Other("this session has no settings folder to install plug-ins into".into()))?;
    // The folder the Plug-in Library installs next to (`Session::plugins_dir`: the host's, else
    // `Plug-ins` next to the settings), so both kinds of install live in one place.
    let plug_dir = s.plugins_dir().unwrap_or_else(|| root.join(PLUGINS_DIR));
    let single = str_p(p, "path").is_some();
    let mut listing_errors: Vec<Value> = Vec::new();
    let sources: Vec<std::path::PathBuf> = match (str_p(p, "path"), str_p(p, "folder")) {
        (Some(path), _) => vec![std::path::PathBuf::from(path)],
        (None, Some(dir)) => {
            let read = std::fs::read_dir(dir).map_err(|e| bad(c, format!("cannot list {dir}: {e}")))?;
            let mut v = Vec::new();
            for entry in read {
                match entry {
                    Ok(e) => match e.path().metadata() {
                        Ok(m) if m.is_file() => v.push(e.path()),
                        // A vanished or unreadable entry is a bundle problem: report it rather
                        // than installing a bundle that silently misses files. (`is_file()`
                        // alone would treat unreadable metadata as "not a file" and skip it.)
                        Err(e) => listing_errors.push(json!({"error": format!("cannot read the bundle folder: {e}")})),
                        Ok(_) => {}
                    },
                    Err(e) => listing_errors.push(json!({"error": format!("cannot read the bundle folder: {e}")})),
                }
            }
            v.sort();
            v
        }
        _ => return Err(bad(c, "give `path` (a .wasm plug-in) or `folder` (a plug-in bundle)")),
    };
    let mut errors = listing_errors;
    let mut installed = Vec::new();
    let mut loaded = Vec::new();
    let mut panels = Vec::new();
    for src in &sources {
        let name = src.file_name().map(|n| n.to_string_lossy().to_string()).unwrap_or_default();
        if name.is_empty() || name.starts_with('.') {
            // A bundle's hidden files (`.DS_Store`, `._x.wasm` resource forks) are skipped; a
            // single install must not report success for a file it skipped.
            if single {
                return Err(bad(c, format!("`{}` is not a plug-in file name (hidden files are not installed)", src.display())));
            }
            continue;
        }
        let is_wasm = src.extension().is_some_and(|x| x.eq_ignore_ascii_case("wasm"));
        let is_panel = src.extension().is_some_and(|x| x.eq_ignore_ascii_case("jsx"));
        if single {
            if !is_wasm {
                return Err(bad(c, "an effect plug-in install is a `.wasm` file"));
            }
        } else if !is_wasm && !is_panel {
            continue; // a bundle may carry readmes, manifests and source: skip them
        }
        let body: std::result::Result<(), String> = (|| {
            // The name the installed file gets, so it must be one the Scripts menu lists and
            // `file.uninstallScript` accepts (like `file.installScript`'s): one bare component,
            // and on Windows not a device name or one Windows rewrites.
            if !super::scripts::is_bare_name(&name) || (cfg!(windows) && super::scripts::windows_unsafe_name(&name)) {
                return Err(format!("`{name}` is not a file name that can be installed"));
            }
            // Never silently replace an installed file: a name collision is either a re-install
            // the user did not ask to overwrite or a bundle that would shadow a working plug-in,
            // and the update path is explicit (remove the old one first).
            if is_panel {
                let key = format!("{}/{name}", super::scripts::PANELS_DIR);
                // Listed, not read: an existing panel whose text cannot be read is still a panel
                // and must not be replaced (reading it would report it as absent). Compared
                // ignoring case and checked on disk too: on Windows and macOS `my panel.jsx` is
                // `My Panel.jsx`, and writing it would replace that panel.
                let lower = name.to_lowercase();
                if cfg.list(super::scripts::PANELS_DIR).iter().any(|n| n.to_lowercase() == lower) || cfg.files().is_file(&root.join(&key)) {
                    return Err(format!("{name} is already installed as a ScriptUI panel; remove it from the Scripts/ScriptUI Panels folder first to update"));
                }
                let bytes = s.services.read_file_bounded(&src.to_string_lossy(), MAX_INSTALL_BYTES).map_err(|e| format!("cannot read it: {e}"))?;
                let code = String::from_utf8(bytes).map_err(|_| "panels are UTF-8 text (.jsx)".to_string())?;
                cfg.write(&key, &code).map_err(|e| format!("cannot install panel: {e}"))?;
                panels.push(json!(name));
                return Ok(());
            }
            let target = plug_dir.join(&name);
            if cfg.files().is_file(&target) {
                return Err(format!("{name} is already installed; remove it from the Plug-ins folder first to update"));
            }
            let bytes = s.services.read_file_bounded(&src.to_string_lossy(), MAX_INSTALL_BYTES).map_err(|e| format!("cannot read it: {e}"))?;
            cfg.files().write(&target, &bytes).map_err(|e| format!("cannot write into the Plug-ins folder: {e}"))?;
            // Load in-session now: a plug-in that cannot load is rolled back, so a broken
            // plug-in never makes every start fail.
            // Its source is the installed copy (what `effect.plugins.list` shows and the next
            // start loads), not the file it was installed from.
            match loader(&bytes, &target.to_string_lossy()) {
                Ok(v) => {
                    loaded.push(v);
                    installed.push(json!(name));
                    Ok(())
                }
                Err(e) => match cfg.files().remove(&target) {
                    Ok(()) => Err(format!("it does not load, nothing was installed: {e}")),
                    // Never say "nothing was installed" when the invalid copy is still there:
                    // every start would report it and a re-install would say "already installed".
                    Err(re) => Err(format!(
                        "it does not load and its copy could not be removed from the Plug-ins folder ({re}): delete `{name}` there, or every start reports it; {e}"
                    )),
                },
            }
        })();
        match body {
            Ok(()) => {}
            Err(e) => {
                if single {
                    return Err(bad(c, format!("{name}: {e}")));
                }
                errors.push(json!({"file": name, "error": e}));
            }
        }
    }
    if !panels.is_empty() {
        s.scripts_changed();
    }
    if !installed.is_empty() || !panels.is_empty() {
        let mut toast = format!("Installed {} effect plug-in(s)", installed.len());
        if !panels.is_empty() {
            toast.push_str(&format!(" and {} ScriptUI panel(s)", panels.len()));
        }
        toast.push_str(": they load on every start");
        s.toast(toast);
    }
    Ok(json!({"installed": installed, "panels": panels, "loaded": loaded, "errors": errors}))
}

/// External effect helpers need a host that runs them.
fn has_helpers(s: &Session) -> std::result::Result<(), String> {
    if s.helpers.is_some() { Ok(()) } else { Err("effect helpers are not available in this build".into()) }
}

/// The host's helper hooks, for the commands that start helpers. Helpers run native code, so a
/// script may start them only with Allow Scripts to Write Files and Access Network on (as for
/// File.execute()).
fn helper_hooks(s: &Session, c: &str) -> Result<crate::HelperHooks> {
    if s.running_for_script() && !s.prefs.scripting.allow_scripts_write_files {
        return Err(bad(
            c,
            "scripts can't start effect helpers unless Settings ▸ Scripting & Expressions ▸ Allow Scripts to Write Files and Access Network is on",
        ));
    }
    s.helpers.ok_or_else(|| EngineError::Other("effect helpers are not available in this build".into()))
}

/// `effect.helpers.list`: the external effect helpers and their state.
fn helpers_list(s: &mut Session, _: &Value) -> Result<Value> {
    Ok(match s.helpers {
        Some(h) => (h.list)(),
        None => json!({"helpers": [], "blocked": [], "available": false}),
    })
}

/// `effect.helpers.scan`: start the installed helpers that aren't running and register their
/// effects. One bad helper doesn't stop the rest; `retry: true` turns blocked effects back on.
fn helpers_scan(s: &mut Session, p: &Value) -> Result<Value> {
    let h = helper_hooks(s, "effect.helpers.scan")?;
    let r = (h.scan)(b_p(p, "retry").unwrap_or(false));
    let n = r["loaded"].as_array().map_or(0, Vec::len);
    if n > 0 {
        s.toast(format!("{n} effect(s) from effect helpers"));
    }
    Ok(r)
}

/// `effect.helpers.load`: load a file or folder through the helpers that accept it (an OpenFX
/// helper takes `.ofx` plug-ins, for example).
fn helpers_load(s: &mut Session, p: &Value) -> Result<Value> {
    let c = "effect.helpers.load";
    let h = helper_hooks(s, c)?;
    let path = str_p(p, "path").ok_or_else(|| bad(c, "missing `path`"))?;
    let r = (h.load)(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
    let n = r["loaded"].as_array().map_or(0, Vec::len);
    if n > 0 {
        s.toast(format!("Loaded {n} effect(s) through a helper"));
    }
    Ok(r)
}

fn apply(s: &mut Session, p: &Value) -> Result<Value> {
    let name = str_p(p, "effect").ok_or_else(|| bad("effect.apply", "missing `effect` (id or name)"))?;
    let spec = effectcraft_effects::lookup(name).ok_or_else(|| bad("effect.apply", format!("unknown effect `{name}`")))?;
    let (cid, ids) = layers_p(s, p)?;
    if ids.is_empty() {
        return Err(bad("effect.apply", "no layer"));
    }
    let sizes: Vec<_> = {
        let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
        ids.iter().filter_map(|id| comp.layer(*id)).map(|l| (l.id, effectcraft_render::effect_bounds(&s.project, comp, l).0)).collect()
    };
    let uids = s.edit(&format!("Apply {}", spec.name), None, |proj, st| {
        let mut out = vec![];
        for (lid, size) in &sizes {
            let mut next = proj.next_id;
            let l = layer_mut(proj, cid, *lid)?;
            let fx = l.props.sub_mut("effects").ok_or_else(|| bad("effect.apply", "this layer type has no effects"))?;
            let same = fx.groups().filter(|g| g.match_id == spec.id).count();
            let name = if same == 0 { spec.name.to_string() } else { format!("{} {}", spec.name, same + 1) };
            let g = effectcraft_effects::instantiate(spec, &mut Ids(&mut next), &name, *size);
            out.push(g.uid);
            fx.children.push(g.into());
            proj.next_id = next;
            st.selected_props = vec![(*lid, *out.last().unwrap_or(&0))];
        }
        st.last_effect = Some(spec.id.to_string());
        Ok(out)
    })?;
    // Each instance's property path prefix (`effects/#2`), ready for prop.set paths.
    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
    let paths: Vec<Value> = sizes
        .iter()
        .zip(&uids)
        .map(|((lid, _), uid)| {
            let n = comp.layer(*lid).and_then(|l| l.props.group("effects")).and_then(|fx| fx.children.iter().position(|c| c.uid() == *uid));
            json!(n.map(|n| format!("effects/#{}", n + 1)))
        })
        .collect();
    Ok(json!({"effects": uids, "paths": paths, "effect": spec.id}))
}

fn find_fx(s: &Session, p: &Value, cmd: &str) -> Result<(effectcraft_project::ItemId, effectcraft_project::LayerId, Uid)> {
    let (cid, lid) = super::layer_p(s, p, cmd)?;
    let layer = s.project.comp(cid).and_then(|c| c.layer(lid)).ok_or(EngineError::NoComp)?;
    let fx = layer.effects().ok_or_else(|| bad(cmd, "no effects"))?;
    let g = match p.get("effect") {
        Some(Value::Number(n)) => {
            let n = n.as_u64().unwrap_or(0);
            fx.groups().find(|g| g.uid == n).or_else(|| usize::try_from(n.saturating_sub(1)).ok().and_then(|i| fx.groups().nth(i)))
        }
        Some(Value::String(name)) => fx.groups().find(|g| &g.name == name || g.match_id == *name),
        _ => s.state.selected_props.iter().find_map(|(l, u)| (*l == lid).then(|| fx.groups().find(|g| g.uid == *u)).flatten()),
    }
    .ok_or_else(|| bad(cmd, "no such effect"))?;
    Ok((cid, lid, g.uid))
}

/// `effect.warning`: what Effect Controls warns about an effect (a custom OCIO config it can't
/// read, or transforms it passes through), `null` when it renders as asked.
fn warning(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "effect.warning";
    let (cid, lid, uid) = find_fx(s, p, cmd)?;
    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
    let layer = comp.layer(lid).ok_or(EngineError::NoComp)?;
    let g = layer.effects().and_then(|fx| fx.groups().find(|g| g.uid == uid)).ok_or_else(|| bad(cmd, "no such effect"))?;
    let t = super::time_p(s, p, Some(comp));
    let ctx = effectcraft_render::EvalCtx {
        project: &s.project,
        comp_id: cid,
        comp,
        time: t,
        expr: s.expr.as_deref(),
        footage: None,
        property_overrides: &[],
        media_overrides: &[],
    };
    Ok(json!({"effect": uid, "warning": effectcraft_effects::warning(g, &mut |pr| ctx.value(layer, pr))}))
}

/// A colour parameter's eyedropper on a keyer (Effect Controls): the colour of the effect's input
/// (the layer's pixels before this effect, so a keyed screen can still be picked) at a
/// layer-space point, set on the parameter. `average` takes the 5 × 5 pixels around it.
fn pick_color(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "effect.pickColor";
    let (cid, lid, fx_uid) = find_fx(s, p, cmd)?;
    let (Some(x), Some(y)) = (f_p(p, "x"), f_p(p, "y")) else { return Err(bad(cmd, "missing `x` / `y` (layer pixels)")) };
    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
    let layer = comp.layer(lid).ok_or(EngineError::NoComp)?;
    let fx = layer.effects().ok_or_else(|| bad(cmd, "no effects"))?;
    let index = fx.groups().position(|g| g.uid == fx_uid).ok_or_else(|| bad(cmd, "no such effect"))?;
    let g = fx.groups().nth(index).ok_or_else(|| bad(cmd, "no such effect"))?;
    let prop = match (p.get("prop").and_then(Value::as_u64), str_p(p, "param")) {
        (Some(uid), _) => g.find(uid),
        (None, Some(path)) => g.prop(path),
        _ => return Err(bad(cmd, "missing `param` (e.g. `screenColour`) or `prop` (uid)")),
    }
    .filter(|pr| pr.ui == effectcraft_project::ParamUi::Color)
    .ok_or_else(|| bad(cmd, "not a colour parameter of this effect"))?;
    let t = super::time_p(s, p, Some(comp));
    let ctx = effectcraft_render::EvalCtx {
        project: &s.project,
        comp_id: cid,
        comp,
        time: t,
        expr: s.expr.as_deref(),
        footage: None,
        property_overrides: &[],
        media_overrides: &[],
    };
    let mut r = effectcraft_render::Renderer::new(&s.project, &*s.footage, effectcraft_render::RenderOpts::default());
    r.expr = s.expr.as_deref();
    r.cache = Some(&s.layer_cache);
    let buf = r.layer_input(&ctx, layer, index).ok_or_else(|| bad(cmd, "this layer has no pixels"))?;
    let (px, py) = buf.to_px([x, y]);
    let (cx, cy) = (px.floor() as i64, py.floor() as i64);
    let rad = if b_p(p, "average") == Some(true) { 2 } else { 0 };
    let mut sum = [0.0f32; 4];
    for yy in cy.saturating_sub(rad)..=cy.saturating_add(rad) {
        for xx in cx.saturating_sub(rad)..=cx.saturating_add(rad) {
            // Outside the layer reads as transparent.
            let c = buf.img.get(xx, yy);
            (0..4).for_each(|i| sum[i] += c[i]);
        }
    }
    if sum[3] <= 1e-6 {
        return Err(bad(cmd, "nothing to sample there (transparent or outside the layer)"));
    }
    // Straight colour of the (averaged) premultiplied pixels.
    let color: Vec<f64> = (0..3).map(|i| (sum[i] / sum[3]).clamp(0.0, 1.0) as f64).chain([1.0]).collect();
    let uid = prop.uid;
    s.execute("prop.set", json!({"comp": cid.0, "layer": lid.0, "prop": uid, "value": color}))?;
    Ok(json!({"prop": uid, "color": color}))
}

/// What a Cryptomatte effect has at a layer-space point: the ID with the most coverage in its
/// Cryptomatte layer, with the aux channels (for the manifest) and the effect's Selection.
struct CryptoHit {
    at: (effectcraft_project::ItemId, LayerId, Tick),
    probe: std::sync::Arc<CryptoProbe>,
    aux: std::sync::Arc<effectcraft_raster::AuxChannels>,
    layer: String,
    hash: u32,
    selection: String,
    prop: Uid,
    /// The Selection has an expression: setting its value wouldn't change what it reads.
    driven: bool,
}

impl CryptoHit {
    fn manifest(&self) -> Option<&[(String, u32)]> {
        self.aux.manifests.iter().find(|(l, _)| *l == self.layer).map(|(_, m)| m.as_slice())
    }
    fn reply(&self, sel: &str) -> Value {
        let selected = effectcraft_effects::selection_hashes(sel, self.manifest()).contains(&self.hash);
        let name = self.aux.manifest_name(&self.layer, self.hash);
        json!({"name": name, "hash": format!("{:08x}", self.hash), "layer": self.layer, "selected": selected})
    }
}

/// What a pick at one frame needs besides the point: the aux channels the Cryptomatte effect
/// reads, its layer, and the effect's input buffer grid (scale, offset). Building it can render
/// (a precomp's ID pass, the effects before the Cryptomatte effect); a point lookup in it is a
/// few array reads. The session keeps the last one (see [`Session::crypto_probe_job`]).
pub struct CryptoProbe {
    key: ProbeKey,
    grid: std::result::Result<ProbeGrid, String>,
}

#[derive(Clone)]
struct ProbeGrid {
    aux: std::sync::Arc<effectcraft_raster::AuxChannels>,
    layer: String,
    scale: f64,
    offset: [f64; 2],
}

/// What a probe depends on: the project revision, the effect (and its index), the frame, the
/// scale and the render prefs ([`Session::render_opts`]: nested switches, draft shadows).
#[derive(Clone, Copy, PartialEq, Debug)]
struct ProbeKey {
    revision: u64,
    at: (effectcraft_project::ItemId, LayerId, Uid, usize),
    frame: ProbeFrame,
    scale: f64,
    prefs: (bool, bool),
}

/// The frame a probe reads. On footage whose masks and effects up to the Cryptomatte effect
/// don't change over time, its source frame: a still has one, held or remapped frames share
/// theirs. Otherwise the comp time.
#[derive(Clone, Copy, PartialEq, Debug)]
enum ProbeFrame {
    Source(i64),
    Comp(Tick),
}

/// The session's kept probe, and the generation of the latest request: a build stores its
/// result only while no newer request or edit came since.
#[derive(Default)]
pub struct CryptoProbeSlot {
    probe: Option<std::sync::Arc<CryptoProbe>>,
    want: Option<ProbeKey>,
    generation: u64,
    /// Jobs run (each on its thread), and those that built (not cancelled before they began).
    jobs: u64,
    builds: u64,
}

impl CryptoProbeSlot {
    /// Drop the kept probe and cancel builds in flight.
    pub(crate) fn clear(&mut self) {
        (self.probe, self.want) = (None, None);
        self.generation += 1;
    }
    pub(crate) fn kept(&self) -> bool {
        self.probe.is_some()
    }
    pub(crate) fn builds(&self) -> (u64, u64) {
        (self.jobs, self.builds)
    }
}

/// A probe built off the UI thread into the session's slot.
pub type CryptoProbeJob = Box<dyn FnOnce() + Send>;

const NO_CRYPTO: &str = "this layer has no Cryptomatte channels (a multi-layer OpenEXR with Cryptomatte, or a 3D precomp)";

impl CryptoProbe {
    /// `None` when `live` turns false between its stages (a newer request or an edit since):
    /// a cancelled build stops early and lets go of what it read.
    fn build(r: &effectcraft_render::Renderer, key: ProbeKey, time: Tick, live: &dyn Fn() -> bool) -> Option<CryptoProbe> {
        let (cid, lid, _, pos) = key.at;
        let build = || -> std::result::Result<Option<ProbeGrid>, String> {
            let comp = r.project.comp(cid).ok_or("no composition")?;
            let layer = comp.layer(lid).ok_or("no such layer")?;
            let g = layer.effects().and_then(|fx| fx.groups().nth(pos)).ok_or("no such effect")?;
            let ctx = effectcraft_render::EvalCtx {
                project: r.project,
                comp_id: cid,
                comp,
                time,
                expr: r.expr,
                footage: None,
                property_overrides: &[],
                media_overrides: &[],
            };
            let params = effectcraft_effects::flatten_params(g, &mut |pr| ctx.value(layer, pr));
            let aux = r.layer_aux(&ctx, layer).ok_or(NO_CRYPTO)?;
            if !live() {
                return Ok(None);
            }
            let layer_name = effectcraft_effects::crypto_layer_named(&aux, params.s("layerName"), params.e("layer") as usize).ok_or(NO_CRYPTO)?;
            // The grid of the effect's input buffer (footage keeps native pixels from 3/4 scale
            // up, proxies have their own size, earlier effects can pad it), rendered and cached.
            if !live() {
                return Ok(None);
            }
            let b = r.layer_input(&ctx, layer, pos).ok_or("this layer has no pixels")?;
            Ok(Some(ProbeGrid { aux, layer: layer_name, scale: b.scale, offset: b.offset }))
        };
        // On another thread no command guard runs: a panic becomes the probe's error.
        let grid = crate::guard::guarded("Reading the Cryptomatte IDs", || Ok(build())).unwrap_or_else(|e| Err(e.to_string()));
        Some(CryptoProbe { key, grid: grid.transpose()? })
    }
}

/// Whether a property in `g` other than `skip` changes over time (keyframes or an expression).
fn moves(g: &PropGroup, skip: Option<Uid>) -> bool {
    g.children.iter().any(|c| match c {
        effectcraft_project::Node::Prop(p) => Some(p.uid) != skip && (p.is_animated() || p.has_expression()),
        effectcraft_project::Node::Group(g) => moves(g, skip),
    })
}

/// [`ProbeFrame`] of the effect at index `pos` of `layer`.
fn probe_frame(ctx: &effectcraft_render::EvalCtx, layer: &Layer, pos: usize) -> ProbeFrame {
    let comp = ProbeFrame::Comp(ctx.time);
    let effectcraft_project::LayerSource::Footage { item } = layer.source else { return comp };
    let Some(effectcraft_project::ItemKind::Footage(f)) = ctx.project.item(item).map(|i| &i.kind) else { return comp };
    let fx = layer.effects().into_iter().flat_map(|fx| fx.groups().take(pos + 1));
    let time_fx = |g: &PropGroup| matches!(&g.kind, GroupKind::Effect { effect } if effect.starts_with("ec.time."));
    let still = f.kind == effectcraft_project::FootageKind::Still;
    let blend = !still && ctx.comp.enable_frame_blending && layer.switches.frame_blend != effectcraft_project::FrameBlend::Off;
    // The Cryptomatte effect's own Selection isn't read by the probe: animated, it keeps it.
    let own = |i: usize, g: &PropGroup| if i == pos { g.prop("selection").map(|p| p.uid) } else { None };
    if blend || layer.masks().is_some_and(|m| moves(m, None)) || fx.enumerate().any(|(i, g)| moves(g, own(i, g)) || time_fx(g)) {
        return comp;
    }
    ProbeFrame::Source(if still { 0 } else { effectcraft_render::frame_position(ctx.source_time(layer), f.frame_rate).0 })
}

/// The Cryptomatte effect `{layer?, effect?, scale?, time?}` names: its probe key, the comp
/// time, its layer, group and Selection property.
#[allow(clippy::type_complexity)]
fn probe_key<'a>(s: &'a Session, p: &Value, cmd: &str) -> Result<(ProbeKey, Tick, &'a Layer, &'a PropGroup, &'a effectcraft_project::Property)> {
    let (cid, lid, fx_uid) = find_fx(s, p, cmd)?;
    let scale = f_p(p, "scale").unwrap_or(1.0);
    if !(scale.is_finite() && scale > 0.0 && scale <= 1.0) {
        return Err(bad(cmd, "`scale` is the preview's resolution factor, above 0 and at most 1"));
    }
    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
    let layer = comp.layer(lid).ok_or(EngineError::NoComp)?;
    let fx = layer.effects().ok_or_else(|| bad(cmd, "no effects"))?;
    let pos = fx.groups().position(|g| g.uid == fx_uid).ok_or_else(|| bad(cmd, "no such effect"))?;
    let g = fx.groups().nth(pos).ok_or_else(|| bad(cmd, "no such effect"))?;
    let prop = g.prop("selection").filter(|_| g.match_id == "ec.3d.cryptomatte").ok_or_else(|| bad(cmd, "not a Cryptomatte effect"))?;
    let time = super::time_p(s, p, Some(comp));
    let ctx = effectcraft_render::EvalCtx {
        project: &s.project,
        comp_id: cid,
        comp,
        time,
        expr: s.expr.as_deref(),
        footage: None,
        property_overrides: &[],
        media_overrides: &[],
    };
    let frame = probe_frame(&ctx, layer, pos);
    let o = s.render_opts(Default::default());
    let prefs = (o.nested_switches, o.draft_shadows);
    Ok((ProbeKey { revision: s.revision, at: (cid, lid, fx_uid, pos), frame, scale, prefs }, time, layer, g, prop))
}

/// The kept probe if it answers for the current revision, for [`keep_crypto_probe`] (taken
/// before an undo, redo or history jump).
pub(crate) fn kept_crypto_probe(s: &Session) -> Option<std::sync::Arc<CryptoProbe>> {
    s.crypto_probe.lock().ok()?.probe.clone().filter(|p| p.key.revision == s.revision)
}

/// After an undo, redo or history jump from `before` (which dropped the probe): `kept`, the
/// probe from before, still answers when only Cryptomatte Selections changed, which the probe
/// doesn't read (undoing a pick, as the pick itself keeps it).
pub(crate) fn keep_crypto_probe(s: &Session, kept: Option<std::sync::Arc<CryptoProbe>>, before: &effectcraft_project::Project) {
    let Some(p) = kept else { return };
    if !only_crypto_selections_differ(before, &s.project) {
        return;
    }
    if let Ok(mut slot) = s.crypto_probe.lock()
        && slot.probe.is_none()
    {
        slot.probe = Some(std::sync::Arc::new(CryptoProbe { key: ProbeKey { revision: s.revision, ..p.key }, grid: p.grid.clone() }));
    }
}

/// Whether projects `a` and `b` differ at most in the Selections of Cryptomatte effects.
fn only_crypto_selections_differ(a: &effectcraft_project::Project, b: &effectcraft_project::Project) -> bool {
    let mut x = a.clone();
    for (cid, it) in x.items.iter_mut() {
        let effectcraft_project::ItemKind::Comp(c) = &mut it.kind else { continue };
        let sels: Vec<(LayerId, Uid)> = c
            .layers
            .iter()
            .flat_map(|l| {
                l.effects()
                    .into_iter()
                    .flat_map(|fx| fx.groups())
                    .filter(|g| g.match_id == "ec.3d.cryptomatte")
                    .filter_map(move |g| g.get("selection").map(|p| (l.id, p.uid)))
            })
            .collect();
        if sels.is_empty() {
            continue;
        }
        let Some(bc) = b.comp(*cid) else { return false };
        let c = std::sync::Arc::make_mut(c);
        for (lid, uid) in sels {
            let Some(src) = bc.layer(lid).and_then(|l| l.props.find(uid)) else { return false };
            if let Some(dst) = c.layer_mut(lid).and_then(|l| l.props.find_mut(uid)) {
                *dst = src.clone();
            }
        }
    }
    x.same_content(b)
}

/// The session's probe when it has `key`'s.
fn cached_probe(s: &Session, key: ProbeKey) -> Option<std::sync::Arc<CryptoProbe>> {
    s.crypto_probe.lock().ok()?.probe.clone().filter(|p| p.key == key)
}

/// [`Session::crypto_probe_ready`].
pub(crate) fn crypto_probe_ready(s: &Session, p: &Value) -> Result<bool> {
    let (key, ..) = probe_key(s, p, "effect.cryptomatteAt")?;
    Ok(cached_probe(s, key).is_some())
}

/// [`Session::crypto_probe_job`].
pub(crate) fn crypto_probe_job(s: &Session, p: &Value) -> Result<Option<CryptoProbeJob>> {
    let (key, time, ..) = probe_key(s, p, "effect.cryptomatteAt")?;
    let generation = {
        let mut slot = s.crypto_probe.lock().map_err(|_| EngineError::Other("the Cryptomatte probe is unavailable".into()))?;
        if slot.probe.as_ref().is_some_and(|p| p.key == key) {
            return Ok(None);
        }
        // A request for another probe cancels the one in flight.
        if slot.want != Some(key) {
            (slot.want, slot.generation) = (Some(key), slot.generation + 1);
        }
        slot.generation
    };
    let (project, footage, expr, cache, accel, slot) =
        (s.project.clone(), s.footage.clone(), s.expr.clone(), s.layer_cache.clone(), s.accel.clone(), s.crypto_probe.clone());
    let opts = s.render_opts(effectcraft_render::RenderOpts { scale: key.scale, ..Default::default() });
    // The slot while this is still the newest request.
    fn current(slot: &std::sync::Mutex<CryptoProbeSlot>, generation: u64) -> Option<std::sync::MutexGuard<'_, CryptoProbeSlot>> {
        slot.lock().ok().filter(|s| s.generation == generation)
    }
    Ok(Some(Box::new(move || {
        match slot.lock() {
            Ok(mut s) if s.generation == generation => (s.jobs, s.builds) = (s.jobs + 1, s.builds + 1),
            Ok(mut s) => return s.jobs += 1,
            Err(_) => return,
        }
        let mut r = effectcraft_render::Renderer::new(&project, footage.as_ref(), opts);
        r.expr = expr.as_deref();
        r.cache = Some(&cache);
        r.accel = accel.as_deref();
        // Checked between its stages too: a superseded build stops at the next one.
        let Some(probe) = CryptoProbe::build(&r, key, time, &|| current(&slot, generation).is_some()) else { return };
        let probe = std::sync::Arc::new(probe);
        // Only the newest request's result, and never over a newer probe.
        if let Some(mut s) = current(&slot, generation)
            && s.probe.as_ref().is_none_or(|p| p.key.revision <= key.revision)
        {
            s.probe = Some(probe);
        }
    })))
}

/// [`Session::crypto_coverage`].
pub(crate) fn crypto_coverage(s: &Session, p: &Value, hash: u32, max_side: usize) -> Option<CryptoCoverage> {
    let (key, ..) = probe_key(s, p, "effect.cryptomatteAt").ok()?;
    let probe = cached_probe(s, key)?;
    let b = probe.grid.as_ref().ok()?;
    let (aw, ah) = (b.aux.width as usize, b.aux.height as usize);
    if aw == 0 || ah == 0 {
        return None;
    }
    let step = aw.max(ah).div_ceil(max_side.max(1)).max(1);
    let (w, h) = (aw.div_ceil(step), ah.div_ceil(step));
    let planes = b.aux.crypto_rank_planes(&b.layer);
    let sample = |j: usize| {
        planes.iter().filter(|(id, _)| id.get(j).is_some_and(|v| v.to_bits() == hash)).map(|(_, c)| c.get(j).map_or(0.0, |c| c.max(0.0))).sum::<f32>().min(1.0)
    };
    // Each sample at the centre of its step × step cell; the last cells are cut by the layer.
    let at = |x: usize, y: usize| sample((y * step + step / 2).min(ah - 1) * aw + (x * step + step / 2).min(aw - 1));
    let coverage = (0..w * h).map(|i| at(i % w, i / w)).collect();
    let (size, uv) = ([aw as f64 / b.aux.scale, ah as f64 / b.aux.scale], [aw as f64 / (w * step) as f64, ah as f64 / (h * step) as f64]);
    Some(CryptoCoverage { width: w, height: h, coverage, size, uv })
}

/// An ID's coverage over a layer, for the eyedropper's hover highlight: `width` × `height`
/// samples (row-major, 0..1). The layer, `size` effect-space pixels from its origin, shows the
/// texture from (0, 0) to `uv`.
pub struct CryptoCoverage {
    pub width: usize,
    pub height: usize,
    pub coverage: Vec<f32>,
    pub size: [f64; 2],
    pub uv: [f64; 2],
}

/// What a pick finds at a point.
enum Hit {
    /// `probeOnly` and the probe isn't built yet.
    Pending,
    Nothing,
    Id(CryptoHit),
}

/// The ID under `{x, y}` (effect space, which is layer space on footage and precomp layers) for
/// the Cryptomatte effect `{layer?, effect?}`, from the aux channels its render reads. The point
/// snaps to the centre of the pixel the effect's input buffer samples in a render at `scale`
/// (the viewer's resolution). Without a kept probe it builds one, unless `probeOnly`.
fn crypto_hit(s: &Session, p: &Value, cmd: &str) -> Result<Hit> {
    let (key, time, layer, g, prop) = probe_key(s, p, cmd)?;
    let (Some(x), Some(y)) = (f_p(p, "x"), f_p(p, "y")) else { return Err(bad(cmd, "missing `x` / `y` (layer pixels)")) };
    let probe = match cached_probe(s, key) {
        Some(probe) => probe,
        None if b_p(p, "probeOnly").unwrap_or(false) => return Ok(Hit::Pending),
        None => {
            let r = s.renderer(effectcraft_render::RenderOpts { scale: key.scale, ..Default::default() });
            if let Ok(mut slot) = s.crypto_probe.lock() {
                slot.clear();
                slot.builds += 1;
            }
            // (Never cancelled here: nothing else runs on this thread.)
            let Some(probe) = CryptoProbe::build(&r, key, time, &|| true).map(std::sync::Arc::new) else { return Ok(Hit::Pending) };
            if let Ok(mut slot) = s.crypto_probe.lock() {
                slot.probe = Some(probe.clone());
            }
            probe
        }
    };
    let b = probe.grid.as_ref().map_err(|e| bad(cmd, e.clone()))?;
    let (bs, o) = (b.scale, b.offset);
    // The centre of its pixel under the point, at the aux point the effect reads there.
    let [ax, ay] = effectcraft_effects::aux_point(bs, o, [(x * bs + o[0]).floor() + 0.5, (y * bs + o[1]).floor() + 0.5]);
    let Some(hash) = b.aux.index_at(ax, ay).and_then(|i| b.aux.crypto_id_at(&b.layer, i)) else { return Ok(Hit::Nothing) };
    let (cid, lid, ..) = key.at;
    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
    let ctx = effectcraft_render::EvalCtx {
        project: &s.project,
        comp_id: cid,
        comp,
        time,
        expr: s.expr.as_deref(),
        footage: None,
        property_overrides: &[],
        media_overrides: &[],
    };
    let selection = effectcraft_effects::flatten_params(g, &mut |pr| ctx.value(layer, pr)).s("selection").to_string();
    let driven = prop.expr.as_ref().is_some_and(|e| e.enabled);
    let (aux, layer_name) = (b.aux.clone(), b.layer.clone());
    Ok(Hit::Id(CryptoHit { at: (cid, lid, time), probe: probe.clone(), aux, layer: layer_name, hash, selection, prop: prop.uid, driven }))
}

/// `effect.cryptomatteAt`: the ID under a point, for the viewer's hover hint. The first call per
/// frame renders the effect's input to learn its pixel grid (kept afterwards); with `probeOnly`
/// it answers `{pending: true}` instead.
fn crypto_at(s: &mut Session, p: &Value) -> Result<Value> {
    Ok(match crypto_hit(s, p, "effect.cryptomatteAt")? {
        Hit::Pending => json!({"pending": true}),
        Hit::Nothing => Value::Null,
        Hit::Id(h) => h.reply(&h.selection),
    })
}

/// The Cryptomatte eyedropper: replace the effect's Selection with the ID under a point, add it
/// or remove it, in one undo step at the time it was read (none when its meaning stays).
fn pick_crypto(s: &mut Session, p: &Value) -> Result<Value> {
    use effectcraft_effects::crypto_select::{PickMode, edit_selection, token_for};
    let cmd = "effect.pickCryptomatte";
    let mode = match str_p(p, "mode").unwrap_or("replace") {
        "replace" => PickMode::Replace,
        "add" => PickMode::Add,
        "remove" => PickMode::Remove,
        m => return Err(bad(cmd, format!("unknown `mode` {m:?} (replace, add or remove)"))),
    };
    let h = match crypto_hit(s, p, cmd)? {
        Hit::Id(h) => h,
        Hit::Pending => return Ok(json!({"pending": true, "changed": false})),
        Hit::Nothing => return Err(bad(cmd, "no Cryptomatte ID there (empty or outside the layer)")),
    };
    if h.driven {
        return Err(bad(cmd, "the Selection is driven by an expression; disable it to pick"));
    }
    let m = h.manifest();
    let sel = edit_selection(&h.selection, &token_for(h.aux.manifest_name(&h.layer, h.hash), h.hash, m), h.hash, mode, m);
    let changed = sel != h.selection;
    if changed {
        let (cid, lid, t) = h.at;
        s.execute("prop.set", json!({"comp": cid.0, "layer": lid.0, "prop": h.prop, "value": sel, "time": t.seconds(), "timeBase": "comp"}))?;
        // The step says what made it (Edit ▸ Undo Pick Cryptomatte, the History panel), not
        // "Change Property" like any other edit. (A changed Selection is always a new step.)
        if let Some(step) = s.history.undo.last_mut() {
            step.0 = "Pick Cryptomatte".into();
        }
        // Only the Selection changed, which the probe doesn't read: the next hover keeps it.
        // (The edit dropped it; a probe built since is newer.)
        if let Ok(mut slot) = s.crypto_probe.lock()
            && slot.probe.is_none()
        {
            let key = ProbeKey { revision: s.revision, ..h.probe.key };
            slot.probe = Some(std::sync::Arc::new(CryptoProbe { key, grid: h.probe.grid.clone() }));
        }
    }
    let mut out = h.reply(&sel);
    out["selection"] = json!(sel);
    out["changed"] = json!(changed);
    Ok(out)
}

fn remove(s: &mut Session, p: &Value) -> Result<Value> {
    let cid = super::comp_id(s, p)?;
    let fx = effects_p(s, p, "effect.remove")?;
    let label = if fx.len() == 1 { "Remove Effect" } else { "Remove Effects" };
    s.edit(label, None, |proj, st| {
        for (lid, uid) in &fx {
            let l = layer_mut(proj, cid, *lid)?;
            if let Some(fx) = l.props.sub_mut("effects") {
                fx.children.retain(|c| c.uid() != *uid);
            }
            st.selected_props.retain(|(_, u)| u != uid);
        }
        Ok(())
    })?;
    Ok(json!(fx.len()))
}

fn remove_all(s: &mut Session, p: &Value) -> Result<Value> {
    let (cid, ids) = layers_p(s, p)?;
    s.edit("Remove All Effects", None, |proj, _| {
        for lid in &ids {
            if let Some(fx) = layer_mut(proj, cid, *lid)?.props.sub_mut("effects") {
                fx.children.clear();
            }
        }
        Ok(())
    })?;
    Ok(Value::Null)
}

fn toggle(s: &mut Session, p: &Value) -> Result<Value> {
    let (cid, lid, uid) = find_fx(s, p, "effect.toggle")?;
    let v = b_p(p, "value");
    let r = s.edit("Toggle Effect", None, |proj, _| {
        let l = layer_mut(proj, cid, lid)?;
        let g = l.props.find_group_mut(uid).ok_or_else(|| bad("effect.toggle", "gone"))?;
        g.enabled = v.unwrap_or(!g.enabled);
        Ok(g.enabled)
    })?;
    Ok(json!(r))
}

/// `effect.setLabel`: the effect's colour label (None clears it).
fn set_label(s: &mut Session, p: &Value) -> Result<Value> {
    let c = "effect.setLabel";
    let (cid, lid, uid) = find_fx(s, p, c)?;
    let lab = match p.get("label") {
        Some(Value::Number(n)) => n.as_u64().and_then(|i| effectcraft_color::Label::ALL.get(usize::try_from(i).ok()?).copied()),
        Some(Value::String(name)) => s.prefs.label_from_name(name),
        _ => None,
    }
    .ok_or_else(|| bad(c, "missing or unknown `label` (name or index 0-16; 0 / None clears it)"))?;
    s.edit("Effect Label", None, |proj, _| {
        let l = layer_mut(proj, cid, lid)?;
        let g = l.props.find_group_mut(uid).ok_or_else(|| bad(c, "gone"))?;
        g.label = (lab != effectcraft_color::Label::None).then_some(lab);
        Ok(())
    })?;
    Ok(Value::Null)
}

fn reorder(s: &mut Session, p: &Value) -> Result<Value> {
    let (cid, lid, uid) = find_fx(s, p, "effect.reorder")?;
    let to = p.get("index").and_then(Value::as_u64).ok_or_else(|| bad("effect.reorder", "missing `index` (1-based)"))? as usize;
    s.edit("Reorder Effect", None, |proj, _| {
        let fx = layer_mut(proj, cid, lid)?.props.sub_mut("effects").ok_or_else(|| bad("effect.reorder", "no effects"))?;
        let Some(i) = fx.children.iter().position(|c| c.uid() == uid) else { return Ok(()) };
        let g = fx.children.remove(i);
        let to = to.saturating_sub(1).min(fx.children.len());
        fx.children.insert(to, g);
        Ok(())
    })?;
    Ok(Value::Null)
}

fn duplicate(s: &mut Session, p: &Value) -> Result<Value> {
    let (cid, lid, uid) = find_fx(s, p, "effect.duplicate")?;
    let r = s.edit("Duplicate Effect", None, |proj, st| {
        let mut next = proj.next_id;
        let fx = layer_mut(proj, cid, lid)?.props.sub_mut("effects").ok_or_else(|| bad("effect.duplicate", "no effects"))?;
        let Some(i) = fx.children.iter().position(|c| c.uid() == uid) else { return Ok(0) };
        let mut g = fx.children[i].as_group().cloned().ok_or_else(|| bad("effect.duplicate", "not a group"))?;
        g.reassign_uids(&mut next);
        g.name = unique_name(fx, &g.name);
        let u = g.uid;
        fx.children.insert(i + 1, g.into());
        proj.next_id = next + 1;
        st.selected_props = vec![(lid, u)];
        Ok(u)
    })?;
    Ok(json!(r))
}

/// Effect groups selected in Effect Controls / the timeline: (layer, effect uid), in stack order.
pub(crate) fn selected_effects(s: &Session) -> Vec<(LayerId, Uid)> {
    let Some(c) = s.active_comp() else { return vec![] };
    let mut out = vec![];
    for l in &c.layers {
        let Some(fx) = l.effects() else { continue };
        for g in fx.groups() {
            if s.state.selected_props.iter().any(|(sl, u)| *sl == l.id && *u == g.uid) {
                out.push((l.id, g.uid));
            }
        }
    }
    out
}

/// Effects named by `effect` / `effects` (uids, names or 1-based indexes), else the selection.
fn effects_p(s: &Session, p: &Value, cmd: &str) -> Result<Vec<(LayerId, Uid)>> {
    if p.get("effect").is_some() {
        let (_, lid, uid) = find_fx(s, p, cmd)?;
        return Ok(vec![(lid, uid)]);
    }
    if let Some(Value::Array(a)) = p.get("effects") {
        let mut out = vec![];
        for v in a {
            let mut q = p.clone();
            if let Some(o) = q.as_object_mut() {
                o.remove("effects");
                o.insert("effect".into(), v.clone());
            }
            let (_, lid, uid) = find_fx(s, &q, cmd)?;
            out.push((lid, uid));
        }
        return Ok(out);
    }
    let sel = selected_effects(s);
    if sel.is_empty() {
        return Err(bad(cmd, "no effect selected"));
    }
    Ok(sel)
}

pub(crate) fn effect_time_error(cmd: &str) -> EngineError {
    bad(cmd, "an effect keyframe converts outside the supported time range")
}

/// Validate before Layer's saturating conversions, so a bad stretch or time never silently
/// moves a copied key to another frame. Normal-speed layers keep their exact integer ticks.
fn effect_time(layer: &Layer, time: Tick, to_comp: bool, cmd: &str) -> Result<Tick> {
    if !layer.stretch.is_finite() || layer.stretch == 0.0 {
        return Err(bad(cmd, "the layer has an invalid time stretch"));
    }
    let in_range = |t: i64| (Tick::MIN.0..=Tick::MAX.0).contains(&t);
    if !in_range(time.0) {
        return Err(effect_time_error(cmd));
    }
    let offset = if to_comp { time.0 } else { time.0.checked_sub(layer.start_time.0).ok_or_else(|| effect_time_error(cmd))? };
    let scaled = if (layer.stretch - 100.0).abs() < 1e-9 {
        offset
    } else {
        let scaled = if to_comp { offset as f64 * layer.stretch / 100.0 } else { offset as f64 * 100.0 / layer.stretch };
        if !scaled.is_finite() || scaled < Tick::MIN.0 as f64 || scaled > Tick::MAX.0 as f64 {
            return Err(effect_time_error(cmd));
        }
        scaled as i64
    };
    if !in_range(scaled) {
        return Err(effect_time_error(cmd));
    }
    let time = if to_comp { layer.start_time.0.checked_add(scaled).ok_or_else(|| effect_time_error(cmd))? } else { scaled };
    if !in_range(time) {
        return Err(effect_time_error(cmd));
    }
    Ok(Tick(time))
}

/// Change the key time coordinate system throughout an effect, including nested controls.
/// Ease speeds are per second in that coordinate system; reversed time swaps the key sides.
pub(crate) fn retime_effect(group: &mut PropGroup, scale: f64, cmd: &str, mut time: impl FnMut(Tick) -> Result<Tick>) -> Result<()> {
    let mut result = Ok(());
    group.walk_mut(&mut |pr| {
        if result.is_err() {
            return;
        }
        for key in &mut pr.keys {
            let mapped = time(key.time).and_then(|t| {
                if !scale.is_finite() || scale == 0.0 {
                    return Err(effect_time_error(cmd));
                }
                // Spatial paths and non-numeric values ease along positive progress;
                // numeric components instead store a signed value derivative.
                let speed_scale = if pr.spatial || key.value.dims() == 0 { scale.abs() } else { scale };
                for ease in key.in_ease.iter_mut().chain(&mut key.out_ease) {
                    ease.speed /= speed_scale;
                    if !ease.speed.is_finite() {
                        return Err(bad(cmd, "an effect keyframe ease converts outside the supported range"));
                    }
                }
                if scale < 0.0 {
                    std::mem::swap(&mut key.in_interp, &mut key.out_interp);
                    std::mem::swap(&mut key.in_ease, &mut key.out_ease);
                    std::mem::swap(&mut key.spatial_in, &mut key.spatial_out);
                }
                Ok(t)
            });
            match mapped {
                Ok(t) => key.time = t,
                Err(e) => {
                    result = Err(e);
                    return;
                }
            }
        }
        pr.keys.sort_by_key(|key| key.time);
        if pr.keys.windows(2).any(|pair| pair[0].time == pair[1].time) {
            result = Err(bad(cmd, "the layer's time stretch maps effect keyframes to the same tick"));
        }
    });
    result
}

/// Edit ▸ Copy with effects selected: times on the clipboard are comp-time offsets from the
/// earliest copied key, shared by all copied effects and their parameters (#989).
fn copy(s: &mut Session, p: &Value) -> Result<Value> {
    const CMD: &str = "effect.copy";
    let fx = effects_p(s, p, "effect.copy")?;
    let comp = s.active_comp().ok_or(EngineError::NoComp)?;
    let mut groups = Vec::new();
    let mut earliest: Option<Tick> = None;
    for (lid, uid) in fx {
        let layer = comp.layer(lid).ok_or(EngineError::NoComp)?;
        let mut group = layer.effects().and_then(|fx| fx.groups().find(|g| g.uid == uid)).cloned().ok_or_else(|| bad(CMD, "the effect no longer exists"))?;
        retime_effect(&mut group, layer.stretch / 100.0, CMD, |t| {
            let t = effect_time(layer, t, true, CMD)?;
            earliest = Some(earliest.map_or(t, |first| first.min(t)));
            Ok(t)
        })?;
        groups.push(group);
    }
    if let Some(first) = earliest {
        for group in &mut groups {
            retime_effect(group, 1.0, CMD, |t| Ok(Tick(t.0.checked_sub(first.0).ok_or_else(|| effect_time_error(CMD))?)))?;
        }
    }
    s.state.clipboard.clear();
    s.state.key_clipboard.clear();
    s.state.keyframe_text = None;
    s.state.contents_clipboard.clear();
    s.state.mask_clipboard.clear();
    s.state.link_clipboard = None;
    s.state.clip_is_keys = false;
    let n = groups.len();
    s.state.effect_clipboard = groups;
    Ok(json!({"effects": n}))
}

/// A unique instance name among `fx`'s effects (`Gaussian Blur`, `Gaussian Blur 2`…).
pub(crate) fn unique_name(fx: &PropGroup, base: &str) -> String {
    if !fx.groups().any(|g| g.name == base) {
        return base.to_string();
    }
    let stem = base.rsplit_once(' ').filter(|(_, n)| n.parse::<u32>().is_ok()).map(|(s, _)| s).unwrap_or(base);
    (2..).map(|i| format!("{stem} {i}")).find(|n| !fx.groups().any(|g| &g.name == n)).unwrap_or_else(|| base.to_string())
}

/// Edit ▸ Paste with effects on the clipboard: adds copies to every target layer, after the
/// layer's selected effect when it has one, else at the end of its stack. The earliest copied
/// key lands at the destination comp's CTI; all other keys keep their comp-time offsets.
fn paste(s: &mut Session, p: &Value) -> Result<Value> {
    const CMD: &str = "effect.paste";
    let clip = s.state.effect_clipboard.clone();
    if clip.is_empty() {
        return Err(bad("effect.paste", "no effects on the clipboard"));
    }
    let (cid, ids) = layers_p(s, p)?;
    if ids.is_empty() {
        return Err(bad("effect.paste", "select a layer to paste effects onto"));
    }
    let sel = selected_effects(s);
    let cti = s.time_of(cid);
    let label = if clip.len() == 1 { format!("Paste {}", clip[0].name) } else { "Paste Effects".to_string() };
    let uids = s.edit(&label, None, |proj, st| {
        let mut out = vec![];
        let mut next = proj.next_id;
        let mut new_sel = vec![];
        for lid in &ids {
            let l = layer_mut(proj, cid, *lid)?;
            let mut groups = clip.clone();
            for group in &mut groups {
                retime_effect(group, 100.0 / l.stretch, CMD, |offset| {
                    let t = Tick(cti.0.checked_add(offset.0).ok_or_else(|| effect_time_error(CMD))?);
                    effect_time(l, t, false, CMD)
                })?;
            }
            let Some(fx) = l.props.sub_mut("effects") else { continue };
            let at = sel
                .iter()
                .filter(|(sl, _)| sl == lid)
                .filter_map(|(_, u)| fx.children.iter().position(|c| c.uid() == *u))
                .max()
                .map(|i| i + 1)
                .unwrap_or(fx.children.len());
            for (k, mut g) in groups.into_iter().enumerate() {
                g.reassign_uids(&mut next);
                g.name = unique_name(fx, &g.name);
                out.push(g.uid);
                new_sel.push((*lid, g.uid));
                fx.children.insert(at + k, g.into());
            }
        }
        proj.next_id = next + 1;
        st.selected_props = new_sel;
        Ok(out)
    })?;
    Ok(json!({"effects": uids}))
}

/// Effect Controls' Reset: every parameter back to its default. Animated parameters get a
/// keyframe at the current time with the default value (as in After Effects); static ones
/// change their value.
fn reset(s: &mut Session, p: &Value) -> Result<Value> {
    let (cid, lid, uid) = find_fx(s, p, "effect.reset")?;
    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
    let layer = comp.layer(lid).ok_or(EngineError::NoComp)?;
    let size = effectcraft_render::effect_bounds(&s.project, comp, layer).0;
    let lt = layer.layer_time(s.time());
    let g = layer.effects().and_then(|fx| fx.groups().find(|g| g.uid == uid)).ok_or_else(|| bad("effect.reset", "gone"))?;
    let spec = match &g.kind {
        GroupKind::Effect { effect } => effectcraft_effects::find(effect),
        _ => None,
    }
    .ok_or_else(|| bad("effect.reset", "unknown effect"))?;
    let name = g.name.clone();
    s.edit(&format!("Reset {name}"), None, |proj, _| {
        let g = layer_mut(proj, cid, lid)?.props.find_group_mut(uid).ok_or_else(|| bad("effect.reset", "gone"))?;
        for ps in &spec.params {
            // (`group/param` ids live in twirl-down groups.)
            if let Some(pr) = g.prop_mut(ps.id) {
                pr.set_value_at(lt, effectcraft_effects::default_value(ps, size));
            }
        }
        Ok(())
    })?;
    Ok(Value::Null)
}

/// Tint's Swap Colors button edits both swatches at the CTI in one undo step. Like Reset,
/// it keys animated parameters without moving their existing keys or replacing expressions.
fn swap_tint_colors(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "effect.swapTintColors";
    if !p.is_object() || p.get("effect").is_some_and(|v| !v.is_string() && v.as_u64().is_none_or(|n| n == 0)) {
        return Err(bad(cmd, "effect must be a positive index, uid or name"));
    }
    let (cid, lid, uid) = find_fx(s, p, cmd)?;
    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
    let layer = comp.layer(lid).ok_or(EngineError::NoComp)?;
    let g = layer.props.find_group(uid).filter(|g| g.match_id == "ec.color.tint").ok_or_else(|| bad(cmd, "not a Tint effect"))?;
    let lt = layer.layer_time(s.time_of(cid));
    let color = |id| {
        g.prop(id)
            .map(|pr| pr.value_at(lt))
            .filter(|v| matches!(v, effectcraft_keyframe::Value::Color(_)))
            .ok_or_else(|| bad(cmd, "Tint is missing a colour parameter"))
    };
    let (black, white) = (color("black")?, color("white")?);
    s.edit("Swap Tint Colors", None, |proj, _| {
        let g = layer_mut(proj, cid, lid)?.props.find_group_mut(uid).ok_or_else(|| bad(cmd, "effect gone"))?;
        for (id, value) in [("black", white), ("white", black)] {
            g.prop_mut(id).ok_or_else(|| bad(cmd, "Tint is missing a colour parameter"))?.set_value_at(lt, value);
        }
        Ok(())
    })?;
    Ok(json!({"effect": uid}))
}

fn last(s: &mut Session, p: &Value) -> Result<Value> {
    let id = s.state.last_effect.clone().ok_or_else(|| bad("effect.applyLast", "no effect applied yet"))?;
    let mut q = p.clone();
    if let Some(o) = q.as_object_mut() {
        o.insert("effect".into(), json!(id));
    } else {
        q = json!({"effect": id});
    }
    apply(s, &q)
}

fn list(_: &mut Session, p: &Value) -> Result<Value> {
    let filter = str_p(p, "filter").map(str::to_lowercase);
    let v: Vec<Value> = effectcraft_effects::all()
        .into_iter()
        .filter(|e| {
            filter.as_ref().is_none_or(|f| effectcraft_effects::name_matches(e, f) || e.id.contains(f.as_str()) || e.category.to_ascii_lowercase().contains(f))
        })
        .map(|e| {
            json!({"id": e.id, "name": e.name, "category": e.category, "gpu": e.gpu, "float": e.float, "params": e.params.iter().map(|p| {
                let mut out = json!({"id": p.id, "name": p.name, "type": p.default.kind_name(), "default": p.default.to_json()});
                match &p.ui {
                    effectcraft_project::ParamUi::Popup { options } => {
                        out["options"] = super::popup_options(options);
                    }
                    effectcraft_project::ParamUi::Slider { min, max, slider_min, slider_max, decimals } => {
                        out["min"] = json!(min);
                        out["max"] = json!(max);
                        out["sliderMin"] = json!(slider_min);
                        out["sliderMax"] = json!(slider_max);
                        out["decimals"] = json!(decimals);
                    }
                    _ => {}
                }
                out
            }).collect::<Vec<_>>()})
        })
        .collect();
    Ok(json!(v))
}

impl Session {
    /// The named channels of layer `lid` in the active comp at the current time: its
    /// multi-layer OpenEXR footage's layers and channels (`diffuse.R`, `depth.Z`, …), which
    /// EXtractoR and the 3D Channel effects read. `None` for other layers.
    pub fn layer_channels(&self, lid: LayerId) -> Option<std::sync::Arc<effectcraft_raster::AuxChannels>> {
        let layer = self.active_comp()?.layer(lid)?;
        let effectcraft_project::LayerSource::Footage { item } = layer.source else { return None };
        let effectcraft_project::ItemKind::Footage(f) = &self.project.item(item)?.kind else { return None };
        self.footage.aux(item, f, layer.layer_time(self.time()))
    }
}

/// `layer.channels`: the layers and channels of a layer's multi-layer OpenEXR footage, and
/// what each layer shows in red, green, blue and alpha (EXtractoR's popups).
fn channels(s: &mut Session, p: &Value) -> Result<Value> {
    let (_, lid) = super::layer_p(s, p, "layer.channels")?;
    let Some(aux) = s.layer_channels(lid) else { return Ok(json!({"channels": [], "layers": []})) };
    let layers: Vec<Value> = aux.layers().into_iter().map(|l| json!({"name": l, "rgba": aux.layer_rgba(l)})).collect();
    Ok(json!({"channels": aux.names(), "layers": layers}))
}

pub fn specs() -> Vec<CommandSpec> {
    vec![
        cmd!("effect.apply", "Apply Effect", [], None, "{effect: id|name (e.g. Gaussian Blur), layers?}", has_layers, apply),
        crate::query!(
            "layer.channels",
            "Layer Channels",
            "{layer?} → {channels: [name], layers: [{name, rgba: [r, g, b, a channel]}]} — a multi-layer OpenEXR layer's channels (EXtractoR's red / green / blue / alpha take these names)",
            channels
        ),
        cmd!(
            "effect.pickColor",
            "Pick Effect Colour",
            [],
            None,
            "{layer?, effect?: index|uid|name, param: id (e.g. screenColour) | prop: uid, x, y (effect space), average?: bool (5×5), time?} — the colour of the effect's input there",
            has_layers,
            pick_color
        ),
        cmd!(
            "effect.pickCryptomatte",
            "Pick Cryptomatte",
            [],
            None,
            "{layer?, effect?: index|uid|name, x, y (effect space), mode?: replace|add|remove (default replace), scale? (preview resolution, default 1), time?, probeOnly?} → {name, hash, layer, selection, changed, selected} | {pending} — edits the Cryptomatte effect's Selection with the ID under the point",
            has_layers,
            pick_crypto
        ),
        crate::query!(
            "effect.cryptomatteAt",
            "Cryptomatte At",
            "{layer?, effect?: index|uid|name, x, y (effect space), scale?, time?, probeOnly?: bool (don't build the probe)} → {name, hash, layer, selected} | {pending} | null — the Cryptomatte ID under the point",
            crypto_at
        ),
        cmd!("effect.applyLast", "Last Effect", ["Effect"], Some("Cmd+Alt+Shift+E"), "{layers?}", has_layers, last),
        cmd!("effect.removeAll", "Remove All", ["Effect"], Some("Cmd+Shift+E"), "{layers?}", has_layers, remove_all),
        cmd!("effect.remove", "Remove Effect", [], None, "{layer?, effect: index|uid|name}", has_layers, remove),
        cmd!("effect.toggle", "Toggle Effect", [], None, "{layer?, effect, value?}", has_layers, toggle),
        cmd!("effect.setLabel", "Effect Label", [], None, "{layer?, effect, label: name|index 0-16 (None clears)}", has_layers, set_label),
        cmd!("effect.reorder", "Reorder Effect", [], None, "{layer?, effect, index}", has_layers, reorder),
        cmd!("effect.duplicate", "Duplicate Effect", [], None, "{layer?, effect}", has_layers, duplicate),
        cmd!("effect.copy", "Copy Effects", [], None, "{layer?, effect? | effects?: [uid|name|index]} (default: the selected effects)", has_layers, copy),
        cmd!("effect.paste", "Paste Effects", [], None, "{layers?} — adds the copied effects to the layers", has_layers, paste),
        cmd!("effect.reset", "Reset Effect", [], None, "{layer?, effect}", has_layers, reset),
        cmd!(
            "effect.swapTintColors",
            "Swap Tint Colors",
            [],
            None,
            "{comp?, layer?, effect?: index|uid|name} — swaps Tint's Map Black To and Map White To at the current layer time in one undo step",
            has_layers,
            swap_tint_colors
        ),
        crate::query!(
            "effect.list",
            "List Effects",
            "{filter?} → [{params: [{id, name, type, default, options?, min?, max?, sliderMin?, sliderMax?, decimals?}]}]; popup indices are zero-based (JSX uses one-based values)",
            list
        ),
        crate::query!(
            "effect.warning",
            "Effect Warning",
            "{layer?, effect?: index|uid|name (default: the selected effect), time?} → {effect, warning: string|null} — what Effect Controls warns about (an OCIO config it can't read, transforms it passes through)",
            warning
        ),
        crate::query!(
            "effect.plugins.list",
            "List Effect Plug-ins",
            "{} → {api, wasm, helpers, plugins: [{id, name, category, version, author, source, params, error}]}",
            plugins_list
        ),
        cmd!(
            "effect.plugins.load",
            "Load Effect Plug-in...",
            [],
            None,
            "{path (.wasm / .wat plug-in, API v1) | folder (loads every .wasm in it)}",
            super::always,
            plugins_load
        ),
        cmd!(
            "effect.plugins.install",
            "Install Effect Plug-in...",
            [],
            None,
            "{path (.wasm plug-in: copied into the Plug-ins folder and loaded on every start) | folder (a plug-in bundle: every .wasm goes into the Plug-ins folder and every .jsx becomes a ScriptUI panel), bundle? (the menu: ask for a folder)}",
            super::always,
            plugins_install
        ),
        crate::query!(
            "effect.helpers.list",
            "List Effect Helpers",
            "{} → {helpers: [{program, name, version, loads, running, effects, restarts, error}], blocked: [effect ids]}",
            helpers_list
        ),
        cmd!(
            "effect.helpers.scan",
            "Scan for Effect Helpers",
            [],
            None,
            "{retry?} → {paths, helpers, loaded, errors}: starts the effect helpers installed in helpers/ next to the app, helpers/ in the settings folder and EFFECTCRAFT_HELPER_PATH, and adds their effects; retry turns effects that kept stopping their helper back on",
            has_helpers,
            helpers_scan
        ),
        cmd!(
            "effect.helpers.load",
            "Load Plug-ins Through Helper...",
            [],
            None,
            "{path (a file or folder an installed helper accepts, e.g. a folder of .ofx plug-ins for an OpenFX helper; the menu asks for a folder)} → {loaded: [{id, name, category, helper}], errors}",
            has_helpers,
            helpers_load
        ),
    ]
}

#[cfg(test)]
mod list_metadata_tests {
    use super::*;

    #[test]
    fn effect_list_exposes_popup_labels_and_numeric_slider_limits() {
        let mut s = Session::default();
        let menus = s.execute("effect.list", json!({"filter": "ec.control.dropdown"})).unwrap();
        assert_eq!(menus.as_array().map(Vec::len), Some(1));
        let menu = &menus[0]["params"][0];
        assert_eq!(menu["type"], "enum");
        assert_eq!(menu["default"], 0);
        assert_eq!(
            menu["options"],
            json!([
                {"value": 0, "label": "Item 1"},
                {"value": 1, "label": "Item 2"},
                {"value": 2, "label": "Item 3"}
            ])
        );
        let sliders = s.execute("effect.list", json!({"filter": "ec.control.slider"})).unwrap();
        assert_eq!(sliders.as_array().map(Vec::len), Some(1));
        let slider = &sliders[0]["params"][0];
        assert_eq!(slider["type"], "scalar");
        assert_eq!(slider["min"], -1_000_000.0);
        assert_eq!(slider["max"], 1_000_000.0);
        assert_eq!(slider["sliderMin"], 0.0);
        assert_eq!(slider["sliderMax"], 100.0);
        assert_eq!(slider["decimals"], 2);
        assert!(slider["options"].is_null());
    }
}