use crate::*;
pub(crate) use std::fmt::Write;
pub(crate) use ::tengri::tui::ratatui::prelude::Position;

impl App {

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

#[tengri_proc::view(TuiOut)]
impl App {
    pub fn view_nil (&self) -> impl Content<TuiOut> + use<'_> {
        "nil"
    }
    pub fn view_status_v (&self) -> impl Content<TuiOut> + use<'_> {
        self.update_clock();
        let cache   = self.view_cache.read().unwrap();
        let theme   = self.color;
        let playing = self.clock().is_rolling();
        Tui::bg(theme.darkest.rgb, Fixed::xy(20, 6, Outer(true, Style::default().fg(Tui::g(96))).enclose(
            col!(
                Fill::x(Align::w(Bsp::e(
                    Align::w(Tui::bg(if playing { Rgb(0, 128, 0) } else { Rgb(128, 64, 0) },
                        Either::new(false, // TODO
                            Thunk::new(move||Fixed::x(9, Either::new(playing,
                                Tui::fg(Rgb(0, 255, 0),   " PLAYING "),
                                Tui::fg(Rgb(255, 128, 0), " STOPPED ")))
                            ),
                            Thunk::new(move||Fixed::x(5, Either::new(playing,
                                Tui::fg(Rgb(0, 255, 0),   Bsp::s(" 🭍🭑🬽 ", " 🭞🭜🭘 ",)),
                                Tui::fg(Rgb(255, 128, 0), Bsp::s(" ▗▄▖ ", " ▝▀▘ ",))))
                            )
                        )
                    )),
                    Bsp::s(
                        FieldH(theme, "Beat", cache.beat.view.clone()),
                        FieldH(theme, "Time", cache.time.view.clone()),
                    ),
                ))),
                Fill::x(Align::w(FieldH(theme, "BPM", cache.bpm.view.clone()))),
                Fill::x(Align::w(FieldH(theme, "SR ", cache.sr.view.clone()))),
                Fill::x(Align::w(FieldH(theme, "Buf", cache.buf.view.clone()))),
                Fill::x(Align::w(FieldH(theme, "Lat", cache.lat.view.clone()))),
            ))))
    }
    pub fn view_status (&self) -> impl Content<TuiOut> + use<'_> {
        self.update_clock();
        let cache = self.view_cache.read().unwrap();
        view_status(Some(self.project.selection.describe(self.tracks(), self.scenes())),
            cache.sr.view.clone(), cache.buf.view.clone(), cache.lat.view.clone())
    }
    pub fn view_transport (&self) -> impl Content<TuiOut> + use<'_> {
        self.update_clock();
        let cache = self.view_cache.read().unwrap();
        view_transport(self.project.clock.is_rolling(),
            cache.bpm.view.clone(), cache.beat.view.clone(), cache.time.view.clone())
    }
    pub fn view_editor (&self) -> impl Content<TuiOut> + use<'_> {
        self.editor()
    }
    pub fn view_editor_status (&self) -> impl Content<TuiOut> + use<'_> {
        self.editor().map(|e|Bsp::s(e.clip_status(), e.edit_status()))
    }
    pub fn view_midi_ins_status (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.get_track().map(|track|{
            let ins = track.sequencer.midi_ins.len() as u16;
            Fixed::xy(20, 1 + ins, Outer(true, Style::default().fg(Tui::g(96))).enclose(
                Fixed::xy(20, 1 + ins, FieldV(self.color, format!("MIDI ins:  "),
                    Map::south(1, ||track.sequencer.midi_ins.iter(),
                        |port, index|Fill::x(Align::w(format!(" {index} {}", port.name()))))))))
        })
    }
    pub fn view_midi_outs_status (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.get_track().map(|track|{
            let outs = track.sequencer.midi_outs.len() as u16;
            Fixed::xy(20, 1 + outs, Outer(true, Style::default().fg(Tui::g(96))).enclose(
                Fixed::xy(20, 1 + outs, FieldV(self.color, format!("MIDI outs:  "),
                    Map::south(1, ||track.sequencer.midi_outs.iter(),
                        |port, index|Fill::x(Align::w(format!(" {index} {}", port.name()))))))))
        })
    }
    pub fn view_audio_ins_status (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.get_track()
            .and_then(|track|track.devices.get(0))
            .map(|device|{
                let ins = device.audio_ins().len() as u16;
                Fixed::xy(20, 1 + ins, Outer(true, Style::default().fg(Tui::g(96))).enclose(
                    Fixed::xy(20, 1 + ins, FieldV(self.color, format!("Audio ins: "),
                        Map::south(1, ||device.audio_ins().iter(),
                            |port, index|Fill::x(Align::w(format!(" {index} {}", port.name()))))))))})
    }
    pub fn view_audio_outs_status (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.get_track()
            .and_then(|track|track.devices.last())
            .map(|device|{
                let outs = device.audio_outs().len() as u16;
                Fixed::xy(20, 1 + outs, Outer(true, Style::default().fg(Tui::g(96))).enclose(
                    Fixed::xy(20, 1 + outs, FieldV(self.color, format!("Audio outs: "),
                        Map::south(1, ||device.audio_outs().iter(),
                            |port, index|Fill::x(Align::w(format!(" {index} {}", port.name()))))))))})
    }
    pub fn view_arranger (&self) -> impl Content<TuiOut> + use<'_> {
        ArrangerView::new(&self.project, self.editor.as_ref())
    }
    pub fn view_arranger_scenes (&self) -> impl Content<TuiOut> + use<'_> {
        self.scenes_view(&self.editor)
    }
    pub fn view_arranger_scene_names <'a> (&'a self) -> impl Content<TuiOut> + use<'a> {
        let h  = self.project.scenes.len() as u16 * 2;
        let bg = self.color.darker.rgb;
        Fixed::y(h, Tui::bg(bg, Align::w(Fill::x(Map::new(
            ||self.project.scenes.iter().skip(self.project.scene_scroll),
            move|scene: &Scene, index|
                Push::y(index as u16 * 2u16, Fixed::xy(20, 2,
                    Tui::bg(scene.color.dark.rgb, Align::nw(Bsp::e(
                        format!(" {index:2} "),
                        Tui::fg(Rgb(255, 255, 255),
                            Tui::bold(true, format!("{}", scene.name)))))))))))))
    }
    pub fn view_arranger_scene_clips <'a> (&'a self) -> impl Content<TuiOut> + use<'a> {
        let h  = self.project.scenes.len() as u16 * 2;
        let bg = self.color.darker.rgb;
        Fixed::y(h, Tui::bg(bg, Align::w(Fill::x(Map::new(
            ||self.project.scenes.iter().skip(self.project.scene_scroll),
            move|scene: &'a Scene, index1|
                Push::y(index1 as u16 * 2u16, Fixed::xy(20, 2,
                    Map::new(
                        move||scene.clips.iter().skip(self.project.track_scroll),
                        move|clip: &'a Option<Arc<RwLock<MidiClip>>>, index2|{
                            let (theme, text) = if let Some(clip) = clip {
                                let clip = clip.read().unwrap();
                                (clip.color, clip.name.clone())
                            } else {
                                (scene.color, Default::default())
                            };
                            Push::x(index2 as u16 * 14, Tui::bg(theme.dark.rgb, Bsp::e(
                                format!(" {index1:2} {index2:2} "),
                                Tui::fg(Rgb(255, 255, 255),
                                    Tui::bold(true, format!("{}", text))))))
                        }))))))))
    }
    pub fn view_arranger_track_names (&self) -> impl Content<TuiOut> + use<'_> {
        let mut max_outputs = 0u16;
        for track in self.project.tracks.iter() {
            max_outputs = max_outputs.max(track.sequencer.midi_outs.len() as u16);
        }
        Bsp::w(
            Fixed::x(20, Tui::bg(self.color.darkest.rgb,
                col!(Tui::bold(true, "[t]rack"), "[T] Add"))),
            Align::w(Fixed::y(max_outputs + 1, Tui::bg(self.color.darker.rgb, Align::w(Fill::x(Map::new(
                ||self.project.tracks_with_sizes(&self.project.selection, None)
                    .skip(self.project.track_scroll),
                move|(index, track, x1, x2): (usize, &Track, usize, usize), _|
                    Push::x(index as u16 * 14, Fixed::xy(track.width as u16, max_outputs + 1,
                        Tui::bg(track.color.dark.rgb, Align::nw(Bsp::s(
                            Tui::fg(Rgb(255, 255, 255), Tui::bold(true, format!("{}", track.name))),
                            format!("{index} {x1} {x2}")))))))))))))
    }
    pub fn view_arranger_track_outputs <'a> (&'a self) -> impl Content<TuiOut> + use<'a> {
        let mut max_outputs = 0u16;
        for track in self.project.tracks.iter() {
            max_outputs = max_outputs.max(track.sequencer.midi_outs.len() as u16);
        }
        Bsp::w(
            Fixed::x(20, Tui::bg(self.color.darkest.rgb,
                col!(Tui::bold(true, "[o]utput"), "[O] Add"))),
            Align::w(Fixed::y(max_outputs + 1, Tui::bg(self.color.darker.rgb, Align::w(Fill::x(Map::new(
                ||self.project.tracks_with_sizes(&self.project.selection, None)
                    .skip(self.project.track_scroll),
                move|(index, track, x1, x2): (usize, &'a Track, usize, usize), _|
                    Push::x(x2 as u16, Tui::bg(track.color.dark.rgb, Fixed::xy(
                        track.width as u16,
                        max_outputs + 1,
                        Align::nw(Bsp::s(
                            format!("[mut] [sol]"),
                            Map::south(1, ||track.sequencer.midi_outs.iter(),
                                |port, index|Tui::fg(Rgb(255, 255, 255),
                                    format!("{index}: {}", port.name())))))))))))))))
    }
    pub fn view_arranger_track_inputs <'a> (&'a self) -> impl Content<TuiOut> + use<'a> {
        let mut max_inputs = 0u16;
        for track in self.project.tracks.iter() {
            max_inputs = max_inputs.max(track.sequencer.midi_ins.len() as u16);
        }
        Bsp::w(
            Fixed::x(20, Tui::bg(self.color.darkest.rgb,
                col!(Tui::bold(true, "[i]nputs"), "[I] Add"))),
            Fill::x(Align::w(Fixed::y(max_inputs + 1, Tui::bg(self.color.darker.rgb, Align::w(Fill::x(Map::new(
                ||self.project.tracks_with_sizes(&self.project.selection, None)
                    .skip(self.project.track_scroll),
                move|(index, track, x1, x2): (usize, &'a Track, usize, usize), _|
                    Push::x(x2 as u16, Fixed::xy(track.width as u16, max_inputs + 1,
                        Tui::bg(track.color.dark.rgb, Align::nw(Bsp::s(
                            format!("[rec] [mon]"),
                            Map::south(1, ||track.sequencer.midi_ins.iter(),
                                |port, index|Tui::fg(Rgb(255, 255, 255),
                                    format!("{index}: {}", port.name()))))))))))))))))
    }
    pub fn view_arranger_track_devices <'a> (&'a self) -> impl Content<TuiOut> + use<'a> {
        let mut max_devices = 2u16;
        for track in self.project.tracks.iter() {
            max_devices = max_devices.max(track.devices.len() as u16);
        }
        Bsp::w(
            Fixed::x(20, Tui::bg(self.color.darkest.rgb,
                col!(Tui::bold(true, "[d]evice"), "[D] Add"))),
            Fixed::y(max_devices, Tui::bg(self.color.darker.rgb, Align::w(Fill::x(Map::new(
                ||self.project.tracks_with_sizes(&self.project.selection, None)
                    .skip(self.project.track_scroll),
                move|(index, track, x1, x2): (usize, &'a Track, usize, usize), _|
                    Push::x(x2 as u16, Fixed::xy(track.width as u16, max_devices + 1,
                        Tui::bg(track.color.dark.rgb, Align::nw(Map::south(1, move||0..max_devices,
                            |_, index|format!("{index}: {}", "--------"))))))))))))
    }
    pub fn view_arranger_track_scenes <'a> (&'a self) -> impl Content<TuiOut> + use<'a> {
        let mut max_devices = 0u16;
        for track in self.project.tracks.iter() {
            max_devices = max_devices.max(track.devices.len() as u16);
        }
        Bsp::w(
            Fixed::x(20, Tui::bg(self.color.darkest.rgb,
                col!(Tui::bold(true, "Devices"), "[d] Select", "[D] Add"))),
            Fixed::y(max_devices + 1, Tui::bg(self.color.darker.rgb, Align::w(Fill::x(Map::new(
                ||self.project.tracks_with_sizes(&self.project.selection, None)
                    .skip(self.project.track_scroll),
                move|(index, track, x1, x2): (usize, &'a Track, usize, usize), _|
                    Push::x(x2 as u16, Fixed::xy(track.width as u16, max_devices + 1,
                        Align::nw(Map::south(1, ||track.devices.iter(),
                            |device, index|format!("{index}: {}", device.name())))))))))))
    }
    pub fn view_pool (&self) -> impl Content<TuiOut> + use<'_> {
        Fixed::x(20, Bsp::s(
            Fill::x(Align::w(FieldH(self.color, "Clip pool:", ""))),
            Fill::y(Align::n(Tui::bg(Rgb(0, 0, 0), Outer(true, Style::default().fg(Tui::g(96)))
                .enclose(PoolView(&self.project.pool)))))))
    }
    pub fn view_samples_keys (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.sampler().map(|s|s.view_list(true, self.editor().unwrap()))
    }
    pub fn view_samples_grid (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.sampler().map(|s|s.view_grid())
    }
    pub fn view_sample_viewer (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.sampler().map(|s|s.view_sample(self.editor().unwrap().get_note_pos()))
    }
    pub fn view_sample_info (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.sampler().map(|s|s.view_sample_info(self.editor().unwrap().get_note_pos()))
    }
    pub fn view_sample_status (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.sampler().map(|s|s.view_sample_status(self.editor().unwrap().get_note_pos()))
    }
    pub fn view_meters_input (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.sampler().map(|s|s.view_meters_input())
    }
    pub fn view_meters_output (&self) -> impl Content<TuiOut> + use<'_> {
        self.project.sampler().map(|s|s.view_meters_output())
    }
    pub fn view_dialog (&self) -> impl Content<TuiOut> + use<'_> {
        When(self.dialog.is_some(), Bsp::b( "",
            Fixed::xy(70, 23, Tui::fg_bg(Rgb(255,255,255), Rgb(16,16,16), Bsp::b(
                Repeat(" "), Outer(true, Style::default().fg(Tui::g(96)))
                    .enclose(self.dialog.as_ref().map(|dialog|match dialog {
                        Dialog::Menu(_) =>
                            self.view_dialog_menu().boxed(),
                        Dialog::Help(offset) =>
                            self.view_dialog_help(*offset).boxed(),
                        Dialog::Browser(target, browser) =>
                            self.view_dialog_browser(target, browser).boxed(),
                        Dialog::Options =>
                            self.view_dialog_options().boxed(),
                        Dialog::Device(index) =>
                            self.view_dialog_device(*index).boxed(),
                        Dialog::Message(message) =>
                            self.view_dialog_message(message).boxed(),
                    }))
            )))
        ))
    }
}

impl App {
    pub fn view_dialog_menu (&self) -> impl Content<TuiOut> {
        let options = ||["Projects", "Settings", "Help", "Quit"].iter();
        let option  = |a,i|Tui::fg(Rgb(255,255,255), format!("{}", a));
        Bsp::s(Tui::bold(true, "tek!"), Bsp::s("", Map::south(1, options, option)))
    }
    pub fn view_dialog_help <'a> (&'a self, offset: usize) -> impl Content<TuiOut> + use<'a> {
        Bsp::s(Tui::bold(true, "Help"), Bsp::s("", Map::south(1,
            move||self.config.keys.layers.iter()
                .filter_map(|a|(a.0)(self).then_some(a.1))
                .flat_map(|a|a)
                .filter_map(|x|if let Value::Exp(_, iter)=x.value{ Some(iter) } else { None })
                .skip(offset)
                .take(20),
            |mut b,i|Fixed::x(60, Align::w(Bsp::e("(", Bsp::e(
                b.next().map(|t|Fixed::x(16, Align::w(Tui::fg(Rgb(64,224,0), format!("{}", t.value))))),
                Bsp::e(" ", Align::w(format!("{}", b.0.0.trim()))))))))))
    }
    pub fn view_dialog_device (&self, index: usize) -> impl Content<TuiOut> + use<'_> {
        let choices = ||self.device_kinds().iter();
        let choice = move|label, i|
            Fill::x(Tui::bg(if i == index { Rgb(64,128,32) } else { Rgb(0,0,0) },
                Bsp::e(if i == index { "[ " } else { "  " },
                    Bsp::w(if i == index { " ]" } else { "  " },
                        label))));
        Bsp::s(Tui::bold(true, "Add device"), Map::south(1, choices, choice))
    }
    pub fn view_dialog_message <'a> (&'a self, message: &'a Message) -> impl Content<TuiOut> + use<'a> {
        Bsp::s(message, Bsp::s("", "[ OK ]"))
    }
    pub fn view_dialog_browser <'a> (&'a self, target: &BrowserTarget, browser: &'a Browser) -> impl Content<TuiOut> + use<'a> {
        Bsp::s(
            Padding::xy(3, 1, Fill::x(Align::w(FieldV(
                self.color,
                match target {
                    BrowserTarget::SaveProject     => "Save project:",
                    BrowserTarget::LoadProject     => "Load project:",
                    BrowserTarget::ImportSample(_) => "Import sample:",
                    BrowserTarget::ExportSample(_) => "Export sample:",
                    BrowserTarget::ImportClip(_)   => "Import clip:",
                    BrowserTarget::ExportClip(_)   => "Export clip:",
                },
                Shrink::x(3, Fixed::y(1, Tui::fg(Tui::g(96), RepeatH("🭻")))))))),
            Outer(true, Style::default().fg(Tui::g(96)))
                .enclose(Fill::xy(browser)))
    }
    pub fn view_dialog_load <'a> (&'a self, browser: &'a Browser) -> impl Content<TuiOut> + use<'a> {
        Bsp::s(
            Fill::x(Align::w(Margin::xy(1, 1, Bsp::e(
                Tui::bold(true, " Load project: "),
                Shrink::x(3, Fixed::y(1, RepeatH("🭻"))))))),
            Outer(true, Style::default().fg(Tui::g(96)))
                .enclose(Fill::xy(browser)))
    }
    pub fn view_dialog_export <'a> (&'a self, browser: &'a Browser) -> impl Content<TuiOut> + use<'a> {
        Bsp::s(
            Fill::x(Align::w(Margin::xy(1, 1, Bsp::e(
                Tui::bold(true, " Export: "),
                Shrink::x(3, Fixed::y(1, RepeatH("🭻"))))))),
            Outer(true, Style::default().fg(Tui::g(96)))
                .enclose(Fill::xy(browser)))
    }
    pub fn view_dialog_import <'a> (&'a self, browser: &'a Browser) -> impl Content<TuiOut> + use<'a> {
        Bsp::s(
            Fill::x(Align::w(Margin::xy(1, 1, Bsp::e(
                Tui::bold(true, " Import: "),
                Shrink::x(3, Fixed::y(1, RepeatH("🭻"))))))),
            Outer(true, Style::default().fg(Tui::g(96)))
                .enclose(Fill::xy(browser)))
    }
    pub fn view_dialog_options <'a> (&'a self) -> impl Content<TuiOut> + use<'a> {
        "TODO"
    }
}

impl ArrangerSceneRows for App {
    fn arrangement (&self) -> &Arrangement {
        self.project
    }
    fn scenes_height (&self) -> u16 {
        self.project.scenes_height
    }
    fn width_side    (&self) -> u16 {
        20
    }
    fn width_mid     (&self) -> u16 {
        self.width().saturating_sub(self.width_side() * 2)
    }
    fn scene_selected (&self) -> Option<usize> {
        self.project.selection.scene()
    }
    fn scene_last (&self) -> usize {
        self.project.scenes.len().saturating_sub(1)
    }
    fn track_selected (&self) -> Option<usize> {
        self.project.selection.track()
    }
    fn is_editing (&self) -> bool {
        self.is_editing
    }
}

pub(crate) fn heading <'a> (
    key:     &'a str,
    label:   &'a str,
    count:   usize,
    content: impl Content<TuiOut> + Send + Sync + 'a,
    editing: bool,
) -> impl Content<TuiOut> + 'a {
    let count = format!("{count}");
    Fill::xy(Align::w(Bsp::s(Fill::x(Align::w(button_3(key, label, count, editing))), content)))
}

/// Clear a pre-allocated buffer, then write into it.
#[macro_export] macro_rules! rewrite {
    ($buf:ident, $($rest:tt)*) => { |$buf,_,_|{ $buf.clear(); write!($buf, $($rest)*) } }
}

#[derive(Debug, Default)] pub(crate) struct ViewMemo<T, U> {
    pub(crate) value: T,
    pub(crate) view: Arc<RwLock<U>>
}

impl<T: PartialEq, U> ViewMemo<T, U> {
    fn new (value: T, view: U) -> Self {
        Self { value, view: Arc::new(view.into()) }
    }
    pub(crate) fn update <R> (
        &mut self,
        newval: T,
        render: impl Fn(&mut U, &T, &T)->R
    ) -> Option<R> {
        if newval != self.value {
            let result = render(&mut*self.view.write().unwrap(), &newval, &self.value);
            self.value = newval;
            return Some(result);
        }
        None
    }
}

#[derive(Debug)] pub struct ViewCache {
    pub(crate) sr:   ViewMemo<Option<(bool, f64)>, String>,
    pub(crate) buf:  ViewMemo<Option<f64>, String>,
    pub(crate) lat:  ViewMemo<Option<f64>, String>,
    pub(crate) bpm:  ViewMemo<Option<f64>, String>,
    pub(crate) beat: ViewMemo<Option<f64>, String>,
    pub(crate) time: ViewMemo<Option<f64>, String>,
    pub(crate) scns: ViewMemo<Option<(usize, usize)>, String>,
    pub(crate) trks: ViewMemo<Option<(usize, usize)>, String>,
    pub(crate) stop: Arc<str>,
    pub(crate) edit: Arc<str>,
}

impl Default for ViewCache {
    fn default () -> Self {
        let mut beat = String::with_capacity(16);
        write!(beat, "{}", Self::BEAT_EMPTY);
        let mut time = String::with_capacity(16);
        write!(time, "{}", Self::TIME_EMPTY);
        let mut bpm  = String::with_capacity(16);
        write!(bpm,  "{}", Self::BPM_EMPTY);
        Self {
            beat: ViewMemo::new(None, beat),
            time: ViewMemo::new(None, time),
            bpm:  ViewMemo::new(None, bpm),
            sr:   ViewMemo::new(None, String::with_capacity(16)),
            buf:  ViewMemo::new(None, String::with_capacity(16)),
            lat:  ViewMemo::new(None, String::with_capacity(16)),
            scns: ViewMemo::new(None, String::with_capacity(16)),
            trks: ViewMemo::new(None, String::with_capacity(16)),
            stop: "⏹".into(),
            edit: "edit".into(),
        }
    }
}

impl ViewCache {
    pub const BEAT_EMPTY: &'static str = "-.-.--";
    pub const TIME_EMPTY: &'static str = "-.---s";
    pub const BPM_EMPTY:  &'static str = "---.---";

    pub fn track_counter (cache: &Arc<RwLock<Self>>, track: usize, tracks: usize)
        -> Arc<RwLock<String>>
    {
        let data = (track, tracks);
        cache.write().unwrap().trks.update(Some(data), rewrite!(buf, "{}/{}", data.0, data.1));
        cache.read().unwrap().trks.view.clone()
    }

    pub fn scene_add (cache: &Arc<RwLock<Self>>, scene: usize, scenes: usize, is_editing: bool)
        -> impl Content<TuiOut>
    {
        let data = (scene, scenes);
        cache.write().unwrap().scns.update(Some(data), rewrite!(buf, "({}/{})", data.0, data.1));
        button_3("S", "add scene", cache.read().unwrap().scns.view.clone(), is_editing)
    }

    pub fn update_clock (cache: &Arc<RwLock<Self>>, clock: &Clock, compact: bool) {
        let rate  = clock.timebase.sr.get();
        let chunk = clock.chunk.load(Relaxed) as f64;
        let lat   = chunk / rate * 1000.;
        let delta = |start: &Moment|clock.global.usec.get() - start.usec.get();
        let mut cache = cache.write().unwrap();
        cache.buf.update(Some(chunk), rewrite!(buf, "{chunk}"));
        cache.lat.update(Some(lat),   rewrite!(buf, "{lat:.1}ms"));
        cache.sr.update(Some((compact, rate)), |buf,_,_|{
            buf.clear();
            if compact {
                write!(buf, "{:.1}kHz", rate / 1000.)
            } else {
                write!(buf, "{:.0}Hz", rate)
            }
        });
        if let Some(now) = clock.started.read().unwrap().as_ref().map(delta) {
            let pulse = clock.timebase.usecs_to_pulse(now);
            let time  = now/1000000.;
            let bpm   = clock.timebase.bpm.get();
            cache.beat.update(Some(pulse), |buf, _, _|{
                buf.clear();
                clock.timebase.format_beats_1_to(buf, pulse)
            });
            cache.time.update(Some(time), rewrite!(buf, "{:.3}s", time));
            cache.bpm.update(Some(bpm),   rewrite!(buf, "{:.3}",  bpm));
        } else {
            cache.beat.update(None, rewrite!(buf, "{}", ViewCache::BEAT_EMPTY));
            cache.time.update(None, rewrite!(buf, "{}", ViewCache::TIME_EMPTY));
            cache.bpm.update(None,  rewrite!(buf, "{}", ViewCache::BPM_EMPTY));
        }
    }
}