use crate::*;

/// Collection of custom view definitions.
pub type Views = Arc<RwLock<BTreeMap<Arc<str>, Arc<View<Tui, App>>>>>;

/// Custom view definition is a boxed closure emitting a [Draw]able from state `S`.
pub struct View<S: Screen, T> {
    pub source: Arc<str>,
    pub render: Arc<Box<dyn Fn(&T, &mut S)->Drawn<S::Unit> + Send + Sync>>
}

impl_debug!(<S: Screen, T> View<S, T> |self, w| { write!(w, "View({})", self.source) });

impl_display!(<S: Screen, T> View<S, T> |self, w| { write!(w, "View({})", self.source) });

impl View<Tui, App> {

    pub fn new (source: impl AsRef<str>) -> Usually<Self> {
        Ok(Self {
            source: source.as_ref().into(),
            render: Self::compile(source)?
        })
    }

    fn boxed <F: Fn(&App, &mut Tui)->Drawn<u16> + Send + Sync + 'static> (f: F)
        -> Box<dyn Fn(&App, &mut Tui)->Drawn<u16> + Send + Sync + 'static>
    {
        Box::new(f)
    }

    fn compile (source: impl AsRef<str>) ->
        Usually<Arc<Box<dyn Fn(&App, &mut Tui)->Drawn<u16> + Send + Sync>>>
    {
        let source = source.as_ref();
        let layer = if let Ok(Some(expr)) = source.expr() {
            Self::compile_expr(expr.into())?
        } else if let Ok(Some(word)) = source.word() {
            Self::compile_word(word.into())?
        } else {
            return Err(format!("not word/expr:\n{source:?}").into())
        };
        Ok(Arc::new(Box::new(move|state, screen|layer(state, screen))))
    }

    fn compile_expr (expr: Arc<str>) ->
        Usually<Arc<Box<dyn Fn(&App, &mut Tui)->Drawn<u16> + Send + Sync>>>
    {

        macro_rules! arg {
            ($src:expr, $head:expr, $index:expr, $name:expr) => {
                $src.nth($index)?
                    .ok_or_else(||Box::<dyn Error>::from(format!(
                        "{}: no arg #{} ({}) in {}", $head, $index, $name, $src
                    )))?
            };
        }

        Ok(Arc::new(if let Some(head) = expr.head()? && let Some(ns) = head.split('/').next() {

            match ns {

                "when" => {
                    let cond  = Arc::from(arg!(expr, head, 1, "condition"));
                    let cond  = move|state: &App|state.namespace(&cond)?.ok_or_else(||Box::<dyn Error>::from("when: no condition value"));
                    let thunk = Self::compile(arg!(expr, head, 2, "content"))?;
                    Self::boxed(move|state, screen|{
                        when(
                            cond(state)?,
                            draw(|screen|thunk(state, screen))
                        ).draw(screen)
                    })
                },

                "either" => {
                    let cond = Arc::from(arg!(expr, head, 1, "condition"));
                    let cond = move|state: &App|state.namespace(&cond)?.ok_or_else(||Box::<dyn Error>::from("either: no condition value"));
                    let a = Self::compile(arg!(expr, head, 2, "content A"))?;
                    let b = Self::compile(arg!(expr, head, 3, "content B"))?;
                    Self::boxed(move|state, screen|{
                        either(
                            cond(state)?,
                            draw(|screen|a(state, screen)),
                            draw(|screen|b(state, screen)),
                        ).draw(screen)
                    })
                },

                "bsp" | "split" | "stack" => {
                    let split = head.split('/').skip(1).next();
                    let split = match split {
                        Some("n") => Split::North,
                        Some("s") => Split::South,
                        Some("e") => Split::East,
                        Some("w") => Split::West,
                        Some("a") => Split::Above,
                        Some("b") => Split::Below,
                        _ => return Err(format!("invalid split: {split:?}").into())
                    };
                    let a = Self::compile(arg!(expr, head, 1, "content A"))?;
                    let b = Self::compile(arg!(expr, head, 2, "content B"))?;
                    Self::boxed(move|state, screen|split.stack(
                        draw(|screen|a(state, screen)),
                        draw(|screen|b(state, screen)),
                    ).draw(screen))
                },

                "bar" => {
                    let split = head.split('/').skip(1).next();
                    let split = match split {
                        Some("n") => Split::North,
                        Some("s") => Split::South,
                        Some("e") => Split::East,
                        Some("w") => Split::West,
                        Some("a") => Split::Above,
                        Some("b") => Split::Below,
                        _ => return Err(format!("invalid split: {split:?}").into())
                    };
                    let size = Arc::from(arg!(expr, head, 1, "size"));
                    let size = move|state: &App|state.namespace(&size)?.ok_or_else(||Box::<dyn Error>::from("bar: no size"));
                    let a = Self::compile(arg!(expr, head, 2, "content A"))?;
                    let b = Self::compile(arg!(expr, head, 3, "content B"))?;
                    Self::boxed(move|state, screen|split.bar(
                        size(state)?,
                        draw(|screen|a(state, screen)),
                        draw(|screen|b(state, screen)),
                    ).draw(screen))
                },

                "align" => {
                    let azimuth = head.split('/').skip(1).next();
                    let azimuth = match azimuth {
                        Some("n")  => Azimuth::N,
                        Some("s")  => Azimuth::S,
                        Some("e")  => Azimuth::E,
                        Some("w")  => Azimuth::W,
                        Some("ne") => Azimuth::NE,
                        Some("se") => Azimuth::SE,
                        Some("nw") => Azimuth::NW,
                        Some("sw") => Azimuth::SW,
                        Some("c")  => Azimuth::C,
                        Some("x")  => Azimuth::X,
                        Some("y")  => Azimuth::Y,
                        _ => return Err(format!("invalid azimuth: {azimuth:?}").into())
                    };
                    let thunk = Self::compile(arg!(expr, head, 1, "content"))?;
                    Self::boxed(move|state, screen|{
                        Align(
                            Some(azimuth),
                            draw(|screen|thunk(state, screen))
                        ).draw(screen)
                    })
                },

                "full" | "fill" => {
                    let thunk = Self::compile(arg!(expr, head, 1, "content"))?;
                    match head.split('/').skip(1).next() {
                        Some("w") | Some("x") => Self::boxed(move|state, screen|{
                            Full::W(draw(|screen|thunk(state, screen))).draw(screen)
                        }),
                        Some("h") | Some("y") => Self::boxed(move|state, screen|{
                            Full::H(draw(|screen|thunk(state, screen))).draw(screen)
                        }),
                        Some("wh") | Some("xy") | None => Self::boxed(move|state, screen|{
                            Full::WH(draw(|screen|thunk(state, screen))).draw(screen)
                        }),
                        _ => unreachable!()
                    }
                },

                "exact" | "min" | "max" | "push" | "pull" | "pad" => {
                    match head.split('/').skip(1).next() {
                        Some("w") | Some("x") => {
                            let value = Arc::from(arg!(expr, head, 1, "value"));
                            let value = move|state: &App|state.namespace(&value);
                            let thunk = Self::compile(arg!(expr, head, 2, "content"))?;
                            match ns {
                                "exact" => Self::boxed(move|state, screen|Exact::W(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "push"  => Self::boxed(move|state, screen|Push::X(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "pull"  => Self::boxed(move|state, screen|Pull::X(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "pad"   => Self::boxed(move|state, screen|Pad::X(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "min"   => Self::boxed(move|state, screen|Min::W(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "max"   => Self::boxed(move|state, screen|Max::W(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                _ => unreachable!()
                            }
                        },
                        Some("h") | Some("y") => {
                            let value = Arc::from(arg!(expr, head, 1, "value"));
                            let value = move|state: &App|state.namespace(&value);
                            let thunk = Self::compile(arg!(expr, head, 2, "content"))?;
                            match ns {
                                "exact" => Self::boxed(move|state, screen|Exact::H(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "push"  => Self::boxed(move|state, screen|Push::Y(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "pull"  => Self::boxed(move|state, screen|Pull::Y(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "pad"   => Self::boxed(move|state, screen|Pad::Y(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "min"   => Self::boxed(move|state, screen|Min::H(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                "max"   => Self::boxed(move|state, screen|Max::H(draw(|screen|thunk(state, screen)), value(state)?).draw(screen)),
                                _ => unreachable!()
                            }
                        },
                        Some("wh") | Some("xy") | None => {
                            let value1 = Arc::from(arg!(expr, head, 1, "value"));
                            let value1 = move|state: &App|state.namespace(&value1);
                            let value2 = Arc::from(arg!(expr, head, 2, "value"));
                            let value2 = move|state: &App|state.namespace(&value2);
                            let thunk  = Self::compile(arg!(expr, head, 3, "content"))?;
                            match ns {
                                "exact" => Self::boxed(move|state, screen|Exact::WH(draw(|screen|thunk(state, screen)), value1(state)?, value2(state)?).draw(screen)),
                                "push"  => Self::boxed(move|state, screen|Push::XY(draw(|screen|thunk(state, screen)), value1(state)?, value2(state)?).draw(screen)),
                                "pull"  => Self::boxed(move|state, screen|Pull::XY(draw(|screen|thunk(state, screen)), value1(state)?, value2(state)?).draw(screen)),
                                "pad"   => Self::boxed(move|state, screen|Pad::XY(draw(|screen|thunk(state, screen)), value1(state)?, value2(state)?).draw(screen)),
                                "min"   => Self::boxed(move|state, screen|Min::WH(draw(|screen|thunk(state, screen)), value1(state)?, value2(state)?).draw(screen)),
                                "max"   => Self::boxed(move|state, screen|Max::WH(draw(|screen|thunk(state, screen)), value1(state)?, value2(state)?).draw(screen)),
                                _ => unreachable!()
                            }
                        },
                        _ => unreachable!()
                    }
                },

                "fg" | "bg" => {
                    let color = Arc::from(arg!(expr, head, 1, "color"));
                    let color = move|state: &App|state.namespace(&color);
                    let thunk = Self::compile(arg!(expr, head, 2, "content"))?;
                    match ns {
                        "fg" => Self::boxed(move|state, screen|fg(
                            color(state)?.unwrap_or_default(), draw(|screen|thunk(state, screen))
                        ).draw(screen)),
                        "bg" => Self::boxed(move|state, screen|bg(
                            color(state)?.unwrap_or_default(), draw(|screen|thunk(state, screen))
                        ).draw(screen)),
                        _ => unreachable!()
                    }
                },

                "text" => {
                    let text: Arc<str> = Arc::from(expr.tail()?.unwrap_or_default());
                    Self::boxed(move|_state, screen|{
                        text.draw(screen)
                    })
                },

                _ => return Err(format!("compile_expr: unexpected: {expr:?}").into())

            }

        } else {
            return Err(format!("compile_expr: invalid expression: {expr:?}").into())
        }))
    }

    fn compile_word (word: Arc<str>)
        -> Usually<Arc<Box<dyn Fn(&App, &mut Tui)->Drawn<u16> + Send + Sync>>>
    {
        macro_rules! draw {
            (|$state:ident|$body:expr)=>{Self::boxed(move|$state, to|$body.draw(to))}
        }

        Ok(Arc::new(match word.split("/").next() {
            //Some(":logo")         => view_logo().draw(to),
            Some(":meters")    => match word.split("/").skip(1).next() {
                Some("input")  => Self::boxed(move|_, to|bg(Rgb(30, 30, 30), "Input Meters".align_s().full_h()).draw(to)),
                Some("output") => Self::boxed(move|_, to|bg(Rgb(30, 30, 30), "Output Meters".align_s().full_h()).draw(to)),
                _ => panic!()
            },
            Some(":tracks")     => match &word[(":tracks".len()+1)..] {
                ""              => Self::boxed(move|_, to|"TODO tracks".draw(to)),

                "names"         => draw!(|app|app.project.view_track_names(app.color.clone())),
                "names/count"   => draw!(|app|app.project.view_track_names_count()),
                "names/cells"   => draw!(|app|app.project.view_track_names_cells()),
                "names/add"     => draw!(|app|app.project.view_track_names_add()),

                "devices"       => draw!(|app|app.project.view_track_devices(app.color.clone())),
                "devices/count" => draw!(|app|app.project.view_track_device_count()),
                "devices/cells" => draw!(|app|app.project.view_track_device_cells(app.tracks_devices_height())),
                "devices/add"   => draw!(|app|app.project.view_track_device_add()),

                "inputs"        => draw!(|app|app.project.view_track_inputs(app.color.clone())),
                "inputs/count"  => draw!(|app|app.project.view_track_input_count()),
                "inputs/cells"  => draw!(|app|app.project.view_track_input_cells(app.tracks_inputs_height())),
                "inputs/add"    => draw!(|app|app.project.view_track_input_add()),

                "outputs"       => draw!(|app|app.project.view_track_outputs(app.color.clone(), 0)),
                "outputs/count" => draw!(|app|app.project.view_track_output_count()),
                "outputs/cells" => draw!(|app|app.project.view_track_output_cells()),
                "outputs/add"   => draw!(|app|app.project.view_track_output_add()),

                _ => panic!("unknown: {word}")
            },
            Some(":scenes")     => match word.split("/").skip(1).next() {
                Some("clips")   => draw!(|app|app.view_scenes_clips()),
                Some("names")   => draw!(|app|app.view_scenes_names()),
                _ => panic!()
            },
            Some(":templates")    => draw!(|app|view_templates(app)),
            Some(":browse/title") => draw!(|app|view_browse_title(app)),
            Some(":device")       => draw!(|app|view_device(app)),
            Some(":dialog")       => Self::boxed(move|state, to|draw_dialog(to, word.split("/").skip(1), state)),
            Some(":sessions")     => Self::boxed(move|_,     to|view_sessions().draw(to)),
            Some(":status")       => Self::boxed(move|state, to|draw_status_bar(to, state)),
            Some(":editor")       => Self::boxed(move|_,     to|"TODO Editor".draw(to)),
            Some(":transport")    => Self::boxed(move|_,     to|view_transport(true, "", "", "").draw(to)),
            Some(":debug")        => Self::boxed(move|_,     to|format!("[{:?}]", to.area()).exact_h(1).draw(to)),
            Some(_)               => Self::boxed(move|state, to|if let Some(view) = state.config.get_view(word.as_ref()) {
                (view.render)(state, to)
            } else {
                fg(Color::Rgb(128, 32, 32), format!("undefined: {word:?}")).draw(to)
            }),
            _ => unreachable!()
        }))
    }
}

/// Load custom view definition.
pub fn views_add <'a> (views: &Views, expr: impl Language) -> UsuallyRef<'a, ()> {
    views.try_write().unwrap().insert(
        expr.head()?.ok_or("view: missing name")?.into(),
        View::new(expr.tail()?.ok_or("view: missing body")?)?.into()
    );
    Ok(())
}