use crate::*;

audio!(App: tek_jack_process, tek_jack_event);

/// Command-line configuration.
#[cfg(feature = "cli")] impl Cli {

    pub fn run (&self) -> Usually<()> {

        if let Action::Version = self.action {
            return Ok(tek_show_version())
        }

        let mut config = Config::new(None);
        config.init()?;

        if let Action::Config = self.action {
            tek_print_config(&config);
        } else if let Action::List = self.action {
            todo!("list sessions")
        } else if let Action::Resume = self.action {
            todo!("resume session")
        } else if let Action::New {
            name, bpm, tracks, scenes, sync_lead, sync_follow,
            midi_from, midi_from_re, midi_to, midi_to_re,
            left_from, right_from, left_to, right_to, ..
        } = &self.action {

            // Connect to JACK
            let name = name.as_ref().map_or("tek", |x|x.as_str());
            let jack = Jack::new(&name)?;

            // Collect MIDI IO:
            let midi_ins  = Connect::collect(&midi_from, &[] as &[&str], &midi_from_re).iter().enumerate()
                .map(|(index, connect)|jack.midi_in(&format!("M/{index}"), &[connect.clone()]))
                .collect::<Result<Vec<_>, _>>()?;
            let midi_outs = Connect::collect(&midi_to, &[] as &[&str], &midi_to_re).iter().enumerate()
                .map(|(index, connect)|jack.midi_out(&format!("{index}/M"), &[connect.clone()]))
                .collect::<Result<Vec<_>, _>>()?;

            // TODO: Collect audio IO:
            let empty        = &[] as &[&str];
            let left_froms   = Connect::collect(&left_from,  empty, empty);
            let left_tos     = Connect::collect(&left_to,    empty, empty);
            let right_froms  = Connect::collect(&right_from, empty, empty);
            let right_tos    = Connect::collect(&right_to,   empty, empty);
            let _audio_froms = &[left_froms.as_slice(), right_froms.as_slice()];
            let _audio_tos   = &[left_tos.as_slice(),   right_tos.as_slice()];

            // Create initial project:
            let clock = Clock::new(&jack, *bpm)?;
            let mut project = Arrangement::new(&jack, None, clock, vec![], vec![],
                midi_ins, midi_outs);
            project.tracks_add(tracks.unwrap_or(0), None, &[], &[])?;
            project.scenes_add(scenes.unwrap_or(0))?;

            if matches!(self.action, Action::Status) {
                // Show status and exit
                tek_print_status(&project);
                return Ok(())
            }

            // Initialize the app state
            let app = tek(&jack, project, config, ":menu");
            if matches!(self.action, Action::Headless) {
                // TODO: Headless mode (daemon + client over IPC, then over network...)
                println!("todo headless");
            } else {
                // Run the [Tui] and [Jack] threads with the [App] state.
                Tui::run(true, jack.run(move|jack|{
                    jack.sync_lead(*sync_lead, |mut state|{
                        let clock = app.clock();
                        clock.playhead.update_from_sample(state.position.frame() as f64);
                        state.position.bbt = Some(clock.bbt());
                        state.position
                    })?;
                    jack.sync_follow(*sync_follow)?;
                    Ok(app)
                })?)?;
            }
        }
        Ok(())
    }

}

impl HasJack<'static> for App {
    fn jack (&self) -> &Jack<'static> { &self.jack }
}

impl HasClipsSize     for App {
    fn clips_size (&self) -> &Measure<TuiOut> { &self.project.size_inner }
}

impl HasTrackScroll   for App {
    fn track_scroll (&self) -> usize { self.project.track_scroll() }
}

impl HasSceneScroll   for App {
    fn scene_scroll (&self) -> usize { self.project.scene_scroll() }
}

impl Default for AppCommand {
    fn default () -> Self {
        Self::Nop
    }
}

impl<T> Default for Binding<T> {
    fn default () -> Self {
        Self {
            ..Default::default()
        }
    }
}

impl ScenesView for App {
    fn w_side       (&self) -> u16 { 20 }
    fn w_mid        (&self) -> u16 { (self.measure_width() as u16).saturating_sub(self.w_side()) }
    fn h_scenes     (&self) -> u16 { (self.measure_height() as u16).saturating_sub(20) }
}
impl Default for MenuItem { fn default () -> Self { Self("".into(), Arc::new(Box::new(|_|Ok(())))) } }
impl PartialEq for MenuItem { fn eq (&self, other: &Self) -> bool { self.0 == other.0 } }
impl AsRef<Arc<[MenuItem]>> for MenuItems { fn as_ref (&self) -> &Arc<[MenuItem]> { &self.0 } }
/// Default is always empty map regardless if `E` and `C` implement [Default].
impl<E, C> Default for Bind<E, C> { fn default () -> Self { Self(Default::default()) } }
has!(Jack<'static>:      |self: App|self.jack);
has!(Pool:               |self: App|self.pool);
has!(Dialog:             |self: App|self.dialog);
has!(Clock:              |self: App|self.project.clock);
has!(Option<MidiEditor>: |self: App|self.project.editor);
has!(Selection:          |self: App|self.project.selection);
has!(Vec<MidiInput>:     |self: App|self.project.midi_ins);
has!(Vec<MidiOutput>:    |self: App|self.project.midi_outs);
has!(Vec<Scene>:         |self: App|self.project.scenes);
has!(Vec<Track>:         |self: App|self.project.tracks);
has!(Measure<TuiOut>:    |self: App|self.size);
has_clips!(              |self: App|self.pool.clips);
maybe_has!(Track: |self: App| { MaybeHas::<Track>::get(&self.project) };
                              { MaybeHas::<Track>::get_mut(&mut self.project) });
maybe_has!(Scene: |self: App| { MaybeHas::<Scene>::get(&self.project) };
                              { MaybeHas::<Scene>::get_mut(&mut self.project) });
impl_debug!(MenuItem |self, w| { write!(w, "{}", &self.0) });
impl_debug!(Condition |self, w| { write!(w, "*") });
macro_rules!primitive(($T:ty: $name:ident)=>{
    fn $name (src: impl Language) -> Perhaps<$T> {
        Ok(if let Some(src) = src.src()? { Some(to_number(src)? as $T) } else { None }) } });
primitive!(u8:    try_to_u8);
primitive!(u16:   try_to_u16);
primitive!(usize: try_to_usize);
primitive!(isize: try_to_isize);
namespace!(App: Arc<str> { literal = |dsl|Ok(dsl.src()?.map(|x|x.into())); });
namespace!(App: u8       { literal = |dsl|try_to_u8(dsl); });
namespace!(App: u16      { literal = |dsl|try_to_u16(dsl); symbol = |app| {
    ":w/sidebar"        => app.project.w_sidebar(app.editor().is_some()),
    ":h/sample-detail"  => 6.max(app.measure_height() as u16 * 3 / 9), }; });
namespace!(App: isize    { literal = |dsl|try_to_isize(dsl); });
namespace!(App: usize    { literal = |dsl|try_to_usize(dsl); symbol = |app| {
    ":scene-count"      => app.scenes().len(),
    ":track-count"      => app.tracks().len(),
    ":device-kind"      => app.dialog.device_kind().unwrap_or(0),
    ":device-kind/next" => app.dialog.device_kind_next().unwrap_or(0),
    ":device-kind/prev" => app.dialog.device_kind_prev().unwrap_or(0), }; });
// Provide boolean values.
namespace!(App: bool { symbol = |app| {
    ":mode/editor"         => app.project.editor.is_some(),
    ":focused/dialog"      => !matches!(app.dialog, Dialog::None),
    ":focused/message"     => matches!(app.dialog, Dialog::Message(..)),
    ":focused/add_device"  => matches!(app.dialog, Dialog::Device(..)),
    ":focused/browser"     => app.dialog.browser().is_some(),
    ":focused/pool/import" => matches!(app.pool.mode, Some(PoolMode::Import(..))),
    ":focused/pool/export" => matches!(app.pool.mode, Some(PoolMode::Export(..))),
    ":focused/pool/rename" => matches!(app.pool.mode, Some(PoolMode::Rename(..))),
    ":focused/pool/length" => matches!(app.pool.mode, Some(PoolMode::Length(..))),
    ":focused/clip"        => !app.editor_focused() && matches!(app.selection(), Selection::TrackClip{..}),
    ":focused/track"       => !app.editor_focused() && matches!(app.selection(), Selection::Track(..)),
    ":focused/scene"       => !app.editor_focused() && matches!(app.selection(), Selection::Scene(..)),
    ":focused/mix"         => !app.editor_focused() && matches!(app.selection(), Selection::Mix),
}; });
// TODO: provide colors here
namespace!(App: ItemTheme {});
namespace!(App: Dialog { symbol = |app| {
    ":dialog/none"          => Dialog::None,
    ":dialog/options"       => Dialog::Options,
    ":dialog/device"        => Dialog::Device(0),
    ":dialog/device/prev"   => Dialog::Device(0),
    ":dialog/device/next"   => Dialog::Device(0),
    ":dialog/help"          => Dialog::Help(0),
    ":dialog/save"          => Dialog::Browse(BrowseTarget::SaveProject,
        Browse::new(None).unwrap().into()),
    ":dialog/load"          => Dialog::Browse(BrowseTarget::LoadProject,
        Browse::new(None).unwrap().into()),
    ":dialog/import/clip"   => Dialog::Browse(BrowseTarget::ImportClip(Default::default()),
        Browse::new(None).unwrap().into()),
    ":dialog/export/clip"   => Dialog::Browse(BrowseTarget::ExportClip(Default::default()),
        Browse::new(None).unwrap().into()),
    ":dialog/import/sample" => Dialog::Browse(BrowseTarget::ImportSample(Default::default()),
        Browse::new(None).unwrap().into()),
    ":dialog/export/sample" => Dialog::Browse(BrowseTarget::ExportSample(Default::default()),
        Browse::new(None).unwrap().into()),
}; });
namespace!(App: Selection { symbol = |app| {
    ":select/scene"      => app.selection().select_scene(app.tracks().len()),
    ":select/scene/next" => app.selection().select_scene_next(app.scenes().len()),
    ":select/scene/prev" => app.selection().select_scene_prev(),
    ":select/track"      => app.selection().select_track(app.tracks().len()),
    ":select/track/next" => app.selection().select_track_next(app.tracks().len()),
    ":select/track/prev" => app.selection().select_track_prev(),
}; });
namespace!(App: Color {
    symbol     = |app| {
        ":color/bg" => Color::Rgb(28, 32, 36),
    };
    expression = |app| {
        "g"   (n: u8) => Color::Rgb(n, n, n),
        "rgb" (r: u8, g: u8, b: u8) => Color::Rgb(r, g, b),
    };
});
namespace!(App: Option<u7> { symbol = |app| {
    ":editor/pitch" => Some((app.editor().as_ref().map(|e|e.get_note_pos()).unwrap() as u8).into())
}; });
namespace!(App: Option<usize> { symbol = |app| {
    ":selected/scene" => app.selection().scene(),
    ":selected/track" => app.selection().track(),
}; });
namespace!(App: Option<Arc<RwLock<MidiClip>>> {
    symbol = |app| {
        ":selected/clip" => if let Selection::TrackClip { track, scene } = app.selection() {
            app.scenes()[*scene].clips[*track].clone()
        } else {
            None
        }
    };
});
handle!(TuiIn: |self: App, input|{
    let commands = collect_commands(self, input)?;
    let history  = execute_commands(self, commands)?;
    self.history.extend(history.into_iter());
    Ok(None)
});

impl Config {
    const CONFIG_DIR: &'static str = "tek";
    const CONFIG_SUB: &'static str = "v0";
    const CONFIG:     &'static str = "tek.edn";
    const DEFAULTS:   &'static str = include_str!("./tek.edn");
    /// Create a new app configuration from a set of XDG base directories,
    pub fn new (dirs: Option<BaseDirectories>) -> Self {
        let default = ||BaseDirectories::with_profile(Self::CONFIG_DIR, Self::CONFIG_SUB);
        let dirs = dirs.unwrap_or_else(default);
        Self { dirs, ..Default::default() }
    }
    /// Write initial contents of configuration.
    pub fn init (&mut self) -> Usually<()> {
        self.init_one(Self::CONFIG, Self::DEFAULTS, |cfgs, dsl|{
            cfgs.add(&dsl)?;
            Ok(())
        })?;
        Ok(())
    }
    /// Write initial contents of a configuration file.
    pub fn init_one (
        &mut self, path: &str, defaults: &str, mut each: impl FnMut(&mut Self, &str)->Usually<()>
    ) -> Usually<()> {
        if self.dirs.find_config_file(path).is_none() {
            //println!("Creating {path:?}");
            std::fs::write(self.dirs.place_config_file(path)?, defaults)?;
        }
        Ok(if let Some(path) = self.dirs.find_config_file(path) {
            //println!("Loading {path:?}");
            let src = std::fs::read_to_string(&path)?;
            src.as_str().each(move|item|each(self, item))?;
        } else {
            return Err(format!("{path}: not found").into())
        })
    }
    /// Add statements to configuration from [Dsl] source.
    pub fn add (&mut self, dsl: impl Language) -> Usually<&mut Self> {
        dsl.each(|item|self.add_one(item))?;
        Ok(self)
    }
    fn add_one (&self, item: impl Language) -> Usually<()> {
        if let Some(expr) = item.expr()? {
            let head = expr.head()?;
            let tail = expr.tail()?;
            let name = tail.head()?;
            let body = tail.tail()?;
            //println!("Config::load: {} {} {}", head.unwrap_or_default(), name.unwrap_or_default(), body.unwrap_or_default());
            match head {
                Some("mode") if let Some(name) = name => load_mode(&self.modes, &name, &body)?,
                Some("keys") if let Some(name) = name => load_bind(&self.binds, &name, &body)?,
                Some("view") if let Some(name) = name => load_view(&self.views, &name, &body)?,
                _ => return Err(format!("Config::load: expected view/keys/mode, got: {item:?}").into())
            }
            Ok(())
        } else {
            return Err(format!("Config::load: expected expr, got: {item:?}").into())
        }
    }
    pub fn get_mode (&self, mode: impl AsRef<str>) -> Option<Arc<Mode<Arc<str>>>> {
        self.modes.clone().read().unwrap().get(mode.as_ref()).cloned()
    }
}

// Each mode contains a view, so here we should be drawing it.
// I'm not sure what's going on with this code, though.
impl<D: Language + Ord> Draw<TuiOut> for Mode<D> {

    fn draw (&self, _to: &mut TuiOut) {
        //self.content().draw(to)
    }

}

impl Mode<Arc<str>> {

    /// Add a definition to the mode.
    ///
    /// Supported definitions:
    ///
    ///   - (name ...) -> name
    ///   - (info ...) -> description
    ///   - (keys ...) -> key bindings
    ///   - (mode ...) -> submode
    ///   - ...        -> view
    ///
    /// ```
    /// let mut mode: tek::Mode<std::sync::Arc<str>> = Default::default();
    /// mode.add("(name hello)").unwrap();
    /// ```
    pub fn add (&mut self, dsl: impl Language) -> Usually<()> {
        Ok(if let Ok(Some(expr)) = dsl.expr() && let Ok(Some(head)) = expr.head() {
            //println!("Mode::add: {head} {:?}", expr.tail());
            let tail = expr.tail()?.map(|x|x.trim()).unwrap_or("");
            match head {
                "name" => self.add_name(tail)?,
                "info" => self.add_info(tail)?,
                "keys" => self.add_keys(tail)?,
                "mode" => self.add_mode(tail)?,
                _      => self.add_view(tail)?,
            };
        } else if let Ok(Some(word)) = dsl.word() {
            self.add_view(word);
        } else {
            return Err(format!("Mode::add: unexpected: {dsl:?}").into());
        })

        //DslParse(dsl, ||Err(format!("Mode::add: unexpected: {dsl:?}").into()))
            //.word(|word|self.add_view(word))
            //.expr(|expr|expr.head(|head|{
                ////println!("Mode::add: {head} {:?}", expr.tail());
                //let tail = expr.tail()?.map(|x|x.trim()).unwrap_or("");
                //match head {
                    //"name" => self.add_name(tail),
                    //"info" => self.add_info(tail),
                    //"keys" => self.add_keys(tail)?,
                    //"mode" => self.add_mode(tail)?,
                    //_      => self.add_view(tail),
                //};
            //}))
    }

    fn add_name (&mut self, dsl: impl Language) -> Perhaps<()> {
        Ok(dsl.src()?.map(|src|self.name.push(src.into())))
    }
    fn add_info (&mut self, dsl: impl Language) -> Perhaps<()> {
        Ok(dsl.src()?.map(|src|self.info.push(src.into())))
    }
    fn add_view (&mut self, dsl: impl Language) -> Perhaps<()> {
        Ok(dsl.src()?.map(|src|self.view.push(src.into())))
    }
    fn add_keys (&mut self, dsl: impl Language) -> Perhaps<()> {
        Ok(Some(dsl.each(|expr|{
            self.keys.push(expr.trim().into());
            Ok(())
        })?))
    }
    fn add_mode (&mut self, dsl: impl Language) -> Perhaps<()> {
        Ok(Some(if let Some(id) = dsl.head()? {
            load_mode(&self.modes, &id, &dsl.tail())?;
        } else {
            return Err(format!("Mode::add: self: incomplete: {dsl:?}").into());
        }))
    }

}

impl<E: Clone + Ord, C> Bind<E, C> {

    /// Create a new event map
    pub fn new () -> Self {
        Default::default()
    }

    /// Add a binding to an owned event map.
    pub fn def (mut self, event: E, binding: Binding<C>) -> Self {
        self.add(event, binding);
        self
    }

    /// Add a binding to an event map.
    pub fn add (&mut self, event: E, binding: Binding<C>) -> &mut Self {
        if !self.0.contains_key(&event) {
            self.0.insert(event.clone(), Default::default());
        }
        self.0.get_mut(&event).unwrap().push(binding);
        self
    }

    /// Return the binding(s) that correspond to an event.
    pub fn query (&self, event: &E) -> Option<&[Binding<C>]> {
        self.0.get(event).map(|x|x.as_slice())
    }

    /// Return the first binding that corresponds to an event, considering conditions.
    pub fn dispatch (&self, event: &E) -> Option<&Binding<C>> {
        self.query(event)
            .map(|bb|bb.iter().filter(|b|b.condition.as_ref().map(|c|(c.0)()).unwrap_or(true)).next())
            .flatten()
    }

}

impl<C> Binding<C> {

    /// FIXME: Load an individual command binding from a dizzle.
    ///
    /// ```
    /// let binding = tek::Binding::<()>::from_dsl("foo bar").unwrap();
    /// ```
    pub fn from_dsl (dsl: impl Language) -> Usually<Self> {
        let command:     Option<C>            = None;
        let condition:   Option<Condition>    = None;
        let description: Option<Arc<str>>     = None;
        let source:      Option<Arc<PathBuf>> = None;
        if let Some(command) = command {
            Ok(Self { commands: [command].into(), condition, description, source })
        } else {
            Err(format!("no command in {dsl:?}").into())
        }
    }

}

impl App {

    pub fn update_clock (&self) {
        ViewCache::update_clock(&self.project.clock.view_cache, self.clock(), self.size.w() > 80)
    }

    /// Set modal dialog.
    pub fn set_dialog (&mut self, mut dialog: Dialog) -> Dialog {
        std::mem::swap(&mut self.dialog, &mut dialog);
        dialog
    }

    /// Set picked device in device pick dialog.
    pub fn device_pick (&mut self, index: usize) {
        self.dialog = Dialog::Device(index);
    }

    pub fn add_device (&mut self, index: usize) -> Usually<()> {
        match index {
            0 => {
                let name    = self.jack.with_client(|c|c.name().to_string());
                let midi    = self.project.track().expect("no active track").sequencer.midi_outs[0].port_name();
                let track   = self.track().expect("no active track");
                let port    = format!("{}/Sampler", &track.name);
                let connect = Connect::exact(format!("{name}:{midi}"));
                let sampler = if let Ok(sampler) = Sampler::new(
                    &self.jack, &port, &[connect], &[&[], &[]], &[&[], &[]]
                ) {
                    self.dialog = Dialog::None;
                    Device::Sampler(sampler)
                } else {
                    self.dialog = Dialog::Message("Failed to add device.".into());
                    return Err("failed to add device".into())
                };
                let track   = self.track_mut().expect("no active track");
                track.devices.push(sampler);
                Ok(())
            },
            1 => {
                todo!();
                Ok(())
            },
            _ => unreachable!(),
        }
    }

    /// Return reference to content browser if open.
    pub fn browser (&self) -> Option<&Browse> {
        if let Dialog::Browse(_, ref b) = self.dialog { Some(b) } else { None }
    }

    /// Is a MIDI editor currently focused?
    pub fn editor_focused (&self) -> bool {
        false
    }

    /// Toggle MIDI editor.
    pub fn toggle_editor (&mut self, value: Option<bool>) {
        //FIXME: self.editing.store(value.unwrap_or_else(||!self.is_editing()), Relaxed);
        let value = value.unwrap_or_else(||!self.editor().is_some());
        if value {
            // Create new clip in pool when entering empty cell
            if let Selection::TrackClip { track, scene } = *self.selection()
            && let Some(scene) = self.project.scenes.get_mut(scene)
            && let Some(slot)  = scene.clips.get_mut(track)
            && slot.is_none()
            && let Some(track) = self.project.tracks.get_mut(track)
            {
                let (index, mut clip) = self.pool.add_new_clip();
                // autocolor: new clip colors from scene and track color
                let color = track.color.base.mix(scene.color.base, 0.5);
                clip.write().unwrap().color = ItemColor::random_near(color, 0.2).into();
                if let Some(editor) = &mut self.project.editor {
                    editor.set_clip(Some(&clip));
                }
                *slot = Some(clip.clone());
                //Some(clip)
            } else {
                //None
            }
        } else if let Selection::TrackClip { track, scene } = *self.selection()
            && let Some(scene) = self.project.scenes.get_mut(scene)
            && let Some(slot) = scene.clips.get_mut(track)
            && let Some(clip) = slot.as_mut()
        {
            // Remove clip from arrangement when exiting empty clip editor
            let mut swapped = None;
            if clip.read().unwrap().count_midi_messages() == 0 {
                std::mem::swap(&mut swapped, slot);
            }
            if let Some(clip) = swapped {
                self.pool.delete_clip(&clip.read().unwrap());
            }
        }
    }
}

impl Dialog {
    pub fn welcome () -> Self {
        Self::Menu(1, MenuItems([
            MenuItem("Resume session".into(),     Arc::new(Box::new(|_|Ok(())))),
            MenuItem("Create new session".into(), Arc::new(Box::new(|app|Ok({
                app.dialog = Dialog::None;
                app.mode = app.config.modes.clone().read().unwrap().get(":arranger").cloned().unwrap();
            })))),
            MenuItem("Load old session".into(),   Arc::new(Box::new(|_|Ok(())))),
        ].into()))
    }
    pub fn menu_next (&self) -> Self {
        match self {
            Self::Menu(index, items) => Self::Menu(wrap_inc(*index, items.0.len()), items.clone()),
            _ => Self::None
        }
    }
    pub fn menu_prev (&self) -> Self {
        match self {
            Self::Menu(index, items) => Self::Menu(wrap_dec(*index, items.0.len()), items.clone()),
            _ => Self::None
        }
    }
    pub fn menu_selected (&self) -> Option<usize> { if let Self::Menu(selected, _) = self { Some(*selected) } else { None } }
    pub fn device_kind (&self) -> Option<usize> { if let Self::Device(index) = self { Some(*index) } else { None } }
    pub fn device_kind_next (&self) -> Option<usize> { self.device_kind().map(|index|(index + 1) % device_kinds().len()) }
    pub fn device_kind_prev (&self) -> Option<usize> { self.device_kind().map(|index|index.overflowing_sub(1).0.min(device_kinds().len().saturating_sub(1))) }
    pub fn message (&self) -> Option<&str> { todo!() }
    pub fn browser (&self) -> Option<&Arc<Browse>> { todo!() }
    pub fn browser_target (&self) -> Option<&BrowseTarget> { todo!() }
}

impl<'a> Namespace<'a, AppCommand> for App {
    symbols!('a |app| -> AppCommand {
        "x/inc"   => AppCommand::Inc { axis: ControlAxis::X },
        "x/dec"   => AppCommand::Dec { axis: ControlAxis::X },
        "y/inc"   => AppCommand::Inc { axis: ControlAxis::Y },
        "y/dec"   => AppCommand::Dec { axis: ControlAxis::Y },
        "confirm" => AppCommand::Confirm,
        "cancel"  => AppCommand::Cancel,
    });
}

impl Draw<TuiOut> for App {
    fn draw (&self, to: &mut TuiOut) {
        if let Some(e) = self.error.read().unwrap().as_ref() {
            to.place_at(to.area(), e);
        }
        for (_index, dsl) in self.mode.view.iter().enumerate() {
            if let Err(e) = self.view(to, dsl) {
                *self.error.write().unwrap() = Some(format!("{e}").into());
                break;
            }
        }
    }
}

impl View<TuiOut, ()> for App {

    fn view_expr <'a> (&'a self, to: &mut TuiOut, expr: &'a impl Expression) -> Usually<()> {
        if evaluate_output_expression(self, to, expr)?
        || evaluate_output_expression_tui(self, to, expr)? {
            Ok(())
        } else {
            Err(format!("App::view_expr: unexpected: {expr:?}").into())
        }
    }

    fn view_word <'a> (&'a self, to: &mut TuiOut, dsl: &'a impl Expression) -> Usually<()> {
        let mut frags = dsl.src()?.unwrap().split("/");
        match frags.next() {
            Some(":logo")   => to.place(&view_logo()),
            Some(":status") => to.place(&Fixed::Y(1, "TODO: Status Bar")),
            Some(":meters") => match frags.next() {
                Some("input")  => to.place(&Tui::bg(Rgb(30, 30, 30), Fill::Y(Align::s("Input Meters")))),
                Some("output") => to.place(&Tui::bg(Rgb(30, 30, 30), Fill::Y(Align::s("Output Meters")))),
                _ => panic!()
            },
            Some(":tracks") => match frags.next() {
                None            => to.place(&"TODO tracks"),
                Some("names")   => to.place(&self.project.view_track_names(self.color.clone())),//Tui::bg(Rgb(40, 40, 40), Fill::X(Align::w("Track Names")))),
                Some("inputs")  => to.place(&Tui::bg(Rgb(40, 40, 40), Fill::X(Align::w("Track Inputs")))),
                Some("devices") => to.place(&Tui::bg(Rgb(40, 40, 40), Fill::X(Align::w("Track Devices")))),
                Some("outputs") => to.place(&Tui::bg(Rgb(40, 40, 40), Fill::X(Align::w("Track Outputs")))),
                _ => panic!()
            },
            Some(":scenes") => match frags.next() {
                None                  => to.place(&"TODO scenes"),
                Some(":scenes/names") => to.place(&"TODO Scene Names"),
                _ => panic!()
            },
            Some(":editor") => to.place(&"TODO Editor"),
            Some(":dialog") => match frags.next() {
                Some("menu") => to.place(&if let Dialog::Menu(selected, items) = &self.dialog {
                    let items = items.clone();
                    let selected = selected;
                    Some(Fill::XY(Thunk::new(move|to: &mut TuiOut|{
                        for (index, MenuItem(item, _)) in items.0.iter().enumerate() {
                            to.place(&Push::Y((2 * index) as u16,
                                Tui::fg_bg(
                                    if *selected == index { Rgb(240,200,180) } else { Rgb(200, 200, 200) },
                                    if *selected == index { Rgb(80, 80, 50)  } else { Rgb(30,  30,  30)  },
                                    Fixed::Y(2, Align::n(Fill::X(item)))
                                )));
                        }
                    })))
                } else {
                    None
                }),
                _ => unimplemented!("App::view_word: {dsl:?} ({frags:?})"),
            },
            Some(":templates") => to.place(&{
                let modes  = self.config.modes.clone();
                let height = (modes.read().unwrap().len() * 2) as u16;
                Fixed::Y(height, Min::X(30, Thunk::new(move |to: &mut TuiOut|{
                    for (index, (id, profile)) in modes.read().unwrap().iter().enumerate() {
                        let bg         = if index == 0 { Rgb(70,70,70) } else { Rgb(50,50,50) };
                        let name       = profile.name.get(0).map(|x|x.as_ref()).unwrap_or("<no name>");
                        let info       = profile.info.get(0).map(|x|x.as_ref()).unwrap_or("<no info>");
                        let fg1        = Rgb(224, 192, 128);
                        let fg2        = Rgb(224, 128,  32);
                        let field_name = Fill::X(Align::w(Tui::fg(fg1, name)));
                        let field_id   = Fill::X(Align::e(Tui::fg(fg2, id)));
                        let field_info = Fill::X(Align::w(info));
                        to.place(&Push::Y((2 * index) as u16,
                            Fixed::Y(2, Fill::X(Tui::bg(bg, Bsp::s(
                                Bsp::a(field_name, field_id), field_info))))));
                    }
                })))
            }),
            Some(":sessions") => to.place(&Fixed::Y(6, Min::X(30, Thunk::new(|to: &mut TuiOut|{
                let fg = Rgb(224, 192, 128);
                for (index, name) in ["session1", "session2", "session3"].iter().enumerate() {
                    let bg = if index == 0 { Rgb(50,50,50) } else { Rgb(40,40,40) };
                    to.place(&Push::Y((2 * index) as u16,
                        &Fixed::Y(2, Fill::X(Tui::bg(bg, Align::w(Tui::fg(fg, name)))))));
                }
            })))),
            Some(":browse/title") => to.place(&Fill::X(Align::w(FieldV(ItemColor::default(),
                match self.dialog.browser_target().unwrap() {
                   BrowseTarget::SaveProject     => "Save project:",
                   BrowseTarget::LoadProject     => "Load project:",
                   BrowseTarget::ImportSample(_) => "Import sample:",
                   BrowseTarget::ExportSample(_) => "Export sample:",
                   BrowseTarget::ImportClip(_)   => "Import clip:",
                   BrowseTarget::ExportClip(_)   => "Export clip:",
                }, Shrink::X(3, Fixed::Y(1, Tui::fg(Tui::g(96), Repeat::X("🭻")))))))),
            Some(":device") => {
                let selected = self.dialog.device_kind().unwrap();
                to.place(&Bsp::s(Tui::bold(true, "Add device"), Map::south(1,
                    move||device_kinds().iter(),
                    move|_label: &&'static str, i|{
                        let bg = if i == selected { Rgb(64,128,32) } else { Rgb(0,0,0) };
                        let lb = if i == selected { "[ " } else { "  " };
                        let rb = if i == selected { " ]" } else { "  " };
                        Fill::X(Tui::bg(bg, Bsp::e(lb, Bsp::w(rb, "FIXME device name")))) })))
            },
            Some(":debug") => to.place(&Fixed::Y(1, format!("[{:?}]", to.area()))),
            Some(_) => {
                let views = self.config.views.read().unwrap();
                if let Some(dsl) = views.get(dsl.src()?.unwrap()) {
                    let dsl = dsl.clone();
                    std::mem::drop(views);
                    self.view(to, &dsl)?
                } else {
                    unimplemented!("{dsl:?}");
                }
            },
            _ => unreachable!()
        }
        Ok(())
    }

}