use std::sync::Arc;

use gpui::prelude::FluentBuilder;
use gpui::{
    AnyElement, AnyView, App, AppContext, Axis, Bounds, Context, Edges, Entity, EntityId,
    EventEmitter, Focusable, InteractiveElement as _, IntoElement, ParentElement as _, Pixels,
    Render, SharedString, Styled, Subscription, WeakEntity, Window, actions, div, px,
};

use crate::ElementExt;

#[allow(clippy::module_inception)]
mod dock;
mod panel;
mod stack_panel;
mod tab_panel;

pub use dock::*;
pub use panel::*;
pub use stack_panel::*;
pub use tab_panel::*;

actions!(dock, [ToggleZoom, ClosePanel]);

pub enum DockEvent {
    /// The layout of the dock has changed, subscribers this to save the layout.
    ///
    /// This event is emitted when every time the layout of the dock has changed,
    /// So it emits may be too frequently, you may want to debounce the event.
    LayoutChanged,
}

/// The main area of the dock.
pub struct DockArea {
    pub(crate) bounds: Bounds<Pixels>,

    /// The center view of the dockarea.
    pub items: DockItem,

    /// The left dock of the dock_area.
    left_dock: Option<Entity<Dock>>,

    /// The bottom dock of the dock_area.
    bottom_dock: Option<Entity<Dock>>,

    /// The right dock of the dock_area.
    right_dock: Option<Entity<Dock>>,

    /// The entity_id of the [`TabPanel`](TabPanel) where each toggle button should be displayed,
    toggle_button_panels: Edges<Option<EntityId>>,

    /// Whether to show the toggle button.
    toggle_button_visible: bool,

    /// The top zoom view of the dock_area, if any.
    zoom_view: Option<AnyView>,

    /// Lock panels layout, but allow to resize.
    is_locked: bool,

    /// The panel style, default is [`PanelStyle::Default`](PanelStyle::Default).
    pub(crate) panel_style: PanelStyle,
    subscriptions: Vec<Subscription>,
}

/// DockItem is a tree structure that represents the layout of the dock.
#[derive(Clone)]
pub enum DockItem {
    /// Split layout
    Split {
        axis: Axis,
        items: Vec<DockItem>,
        sizes: Vec<Option<Pixels>>,
        view: Entity<StackPanel>,
    },
    /// Tab layout
    Tabs {
        items: Vec<Arc<dyn PanelView>>,
        active_ix: usize,
        view: Entity<TabPanel>,
    },
    /// Single panel layout
    Panel { view: Arc<dyn PanelView> },
}

impl DockItem {
    /// Create DockItem with split layout, each item of panel have equal size.
    pub fn split(
        axis: Axis,
        items: Vec<DockItem>,
        dock_area: &WeakEntity<DockArea>,
        window: &mut Window,
        cx: &mut App,
    ) -> Self {
        let sizes = vec![None; items.len()];

        Self::split_with_sizes(axis, items, sizes, dock_area, window, cx)
    }

    /// Create DockItem with split layout, each item of panel have specified size.
    ///
    /// Please note that the `items` and `sizes` must have the same length.
    /// Set `None` in `sizes` to make the index of panel have auto size.
    pub fn split_with_sizes(
        axis: Axis,
        items: Vec<DockItem>,
        sizes: Vec<Option<Pixels>>,
        dock_area: &WeakEntity<DockArea>,
        window: &mut Window,
        cx: &mut App,
    ) -> Self {
        let stack_panel = cx.new(|cx| {
            let mut stack_panel = StackPanel::new(axis, window, cx);

            for (i, item) in items.iter().enumerate() {
                let view = item.view();
                let size = sizes.get(i).copied().flatten();
                stack_panel.add_panel(view.clone(), size, dock_area.clone(), window, cx)
            }

            stack_panel
        });

        window.defer(cx, {
            let stack_panel = stack_panel.clone();
            let dock_area = dock_area.clone();
            move |window, cx| {
                _ = dock_area.update(cx, |this, cx| {
                    this.subscribe_panel(&stack_panel, window, cx);
                });
            }
        });

        Self::Split {
            axis,
            items,
            sizes,
            view: stack_panel,
        }
    }

    /// Create DockItem with panel layout
    pub fn panel(panel: Arc<dyn PanelView>) -> Self {
        Self::Panel { view: panel }
    }

    /// Create DockItem with tabs layout, items are displayed as tabs.
    ///
    /// The `active_ix` is the index of the active tab, if `None` the first tab is active.
    pub fn tabs(
        items: Vec<Arc<dyn PanelView>>,
        active_ix: Option<usize>,
        dock_area: &WeakEntity<DockArea>,
        window: &mut Window,
        cx: &mut App,
    ) -> Self {
        let mut new_items: Vec<Arc<dyn PanelView>> = vec![];
        for item in items.into_iter() {
            new_items.push(item)
        }
        Self::new_tabs(new_items, active_ix, dock_area, window, cx)
    }

    pub fn tab<P: Panel>(
        item: Entity<P>,
        dock_area: &WeakEntity<DockArea>,
        window: &mut Window,
        cx: &mut App,
    ) -> Self {
        Self::new_tabs(vec![Arc::new(item.clone())], None, dock_area, window, cx)
    }

    fn new_tabs(
        items: Vec<Arc<dyn PanelView>>,
        active_ix: Option<usize>,
        dock_area: &WeakEntity<DockArea>,
        window: &mut Window,
        cx: &mut App,
    ) -> Self {
        let active_ix = active_ix.unwrap_or(0);
        let tab_panel = cx.new(|cx| {
            let mut tab_panel = TabPanel::new(None, dock_area.clone(), window, cx);
            for item in items.iter() {
                tab_panel.add_panel(item.clone(), window, cx)
            }
            tab_panel.active_ix = active_ix;
            tab_panel
        });

        Self::Tabs {
            items,
            active_ix,
            view: tab_panel,
        }
    }

    /// Returns all panel ids
    pub fn panel_ids(&self, cx: &App) -> Vec<SharedString> {
        match self {
            Self::Panel { .. } => vec![],
            Self::Tabs { view, .. } => view.read(cx).panel_ids(cx),
            Self::Split { items, .. } => items
                .iter()
                .filter_map(|item| match item {
                    DockItem::Tabs { view, .. } => Some(view.read(cx).panel_ids(cx)),
                    _ => None,
                })
                .flatten()
                .collect(),
        }
    }

    /// Returns the views of the dock item.
    pub fn view(&self) -> Arc<dyn PanelView> {
        match self {
            Self::Split { view, .. } => Arc::new(view.clone()),
            Self::Tabs { view, .. } => Arc::new(view.clone()),
            Self::Panel { view, .. } => view.clone(),
        }
    }

    /// Find existing panel in the dock item.
    pub fn find_panel(&self, panel: Arc<dyn PanelView>) -> Option<Arc<dyn PanelView>> {
        match self {
            Self::Split { items, .. } => {
                items.iter().find_map(|item| item.find_panel(panel.clone()))
            }
            Self::Tabs { items, .. } => items.iter().find(|item| *item == &panel).cloned(),
            Self::Panel { view } => Some(view.clone()),
        }
    }

    /// Add a panel to the dock item.
    pub fn add_panel(
        &mut self,
        panel: Arc<dyn PanelView>,
        dock_area: &WeakEntity<DockArea>,
        window: &mut Window,
        cx: &mut App,
    ) {
        match self {
            Self::Tabs { view, items, .. } => {
                items.push(panel.clone());
                view.update(cx, |tab_panel, cx| {
                    tab_panel.add_panel(panel, window, cx);
                });
            }
            Self::Split { view, items, .. } => {
                // Iter items to add panel to the first tabs
                for item in items.iter_mut() {
                    if let DockItem::Tabs { view, .. } = item {
                        view.update(cx, |tab_panel, cx| {
                            tab_panel.add_panel(panel.clone(), window, cx);
                        });
                        return;
                    }
                }

                // Unable to find tabs, create new tabs
                let new_item = Self::tabs(vec![panel.clone()], None, dock_area, window, cx);
                items.push(new_item.clone());
                view.update(cx, |stack_panel, cx| {
                    stack_panel.add_panel(new_item.view(), None, dock_area.clone(), window, cx);
                });
            }
            Self::Panel { .. } => {}
        }
    }

    /// Set the collapsed state of the dock area
    pub fn set_collapsed(&self, collapsed: bool, window: &mut Window, cx: &mut App) {
        match self {
            DockItem::Tabs { view, .. } => {
                view.update(cx, |tab_panel, cx| {
                    tab_panel.set_collapsed(collapsed, window, cx);
                });
            }
            DockItem::Split { items, .. } => {
                // For each child item, set collapsed state
                for item in items {
                    item.set_collapsed(collapsed, window, cx);
                }
            }
            DockItem::Panel { .. } => {}
        }
    }

    /// Recursively traverses to find the left-most and top-most TabPanel.
    pub(crate) fn left_top_tab_panel(&self, cx: &App) -> Option<Entity<TabPanel>> {
        match self {
            DockItem::Tabs { view, .. } => Some(view.clone()),
            DockItem::Split { view, .. } => view.read(cx).left_top_tab_panel(true, cx),
            DockItem::Panel { .. } => None,
        }
    }

    /// Recursively traverses to find the right-most and top-most TabPanel.
    pub(crate) fn right_top_tab_panel(&self, cx: &App) -> Option<Entity<TabPanel>> {
        match self {
            DockItem::Tabs { view, .. } => Some(view.clone()),
            DockItem::Split { view, .. } => view.read(cx).right_top_tab_panel(true, cx),
            DockItem::Panel { .. } => None,
        }
    }

    pub(crate) fn focus_tab_panel(&self, window: &mut Window, cx: &mut App) {
        if let DockItem::Tabs { view, .. } = self {
            window.focus(&view.read(cx).focus_handle(cx), cx);
        }
    }
}

impl DockArea {
    pub fn new(window: &mut Window, cx: &mut Context<Self>) -> Self {
        let stack_panel = cx.new(|cx| StackPanel::new(Axis::Horizontal, window, cx));

        let dock_item = DockItem::Split {
            axis: Axis::Horizontal,
            items: vec![],
            sizes: vec![],
            view: stack_panel.clone(),
        };

        let mut this = Self {
            bounds: Bounds::default(),
            items: dock_item,
            zoom_view: None,
            toggle_button_panels: Edges::default(),
            toggle_button_visible: true,
            left_dock: None,
            right_dock: None,
            bottom_dock: None,
            is_locked: false,
            panel_style: PanelStyle::Default,
            subscriptions: vec![],
        };

        this.subscribe_panel(&stack_panel, window, cx);

        this
    }

    /// Set the panel style of the dock area.
    pub fn style(mut self, style: PanelStyle) -> Self {
        self.panel_style = style;
        self
    }

    /// The DockItem as the center of the dock area.
    ///
    /// This is used to render at the Center of the DockArea.
    pub fn set_center(&mut self, item: DockItem, window: &mut Window, cx: &mut Context<Self>) {
        self.subscribe_item(&item, window, cx);
        self.items = item;
        self.update_toggle_button_tab_panels(window, cx);
        cx.notify();
    }

    pub fn set_left_dock(
        &mut self,
        panel: DockItem,
        size: Option<Pixels>,
        open: bool,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        self.subscribe_item(&panel, window, cx);
        let weak_self = cx.entity().downgrade();
        self.left_dock = Some(cx.new(|cx| {
            let mut dock = Dock::left(weak_self.clone(), window, cx);
            if let Some(size) = size {
                dock.set_size(size, window, cx);
            }
            dock.set_panel(panel, window, cx);
            dock.set_open(open, window, cx);
            dock
        }));
        self.update_toggle_button_tab_panels(window, cx);
    }

    pub fn set_bottom_dock(
        &mut self,
        panel: DockItem,
        size: Option<Pixels>,
        open: bool,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        self.subscribe_item(&panel, window, cx);
        let weak_self = cx.entity().downgrade();
        self.bottom_dock = Some(cx.new(|cx| {
            let mut dock = Dock::bottom(weak_self.clone(), window, cx);
            if let Some(size) = size {
                dock.set_size(size, window, cx);
            }
            dock.set_panel(panel, window, cx);
            dock.set_open(open, window, cx);
            dock
        }));
        self.update_toggle_button_tab_panels(window, cx);
    }

    pub fn set_right_dock(
        &mut self,
        panel: DockItem,
        size: Option<Pixels>,
        open: bool,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        self.subscribe_item(&panel, window, cx);
        let weak_self = cx.entity().downgrade();
        self.right_dock = Some(cx.new(|cx| {
            let mut dock = Dock::right(weak_self.clone(), window, cx);
            if let Some(size) = size {
                dock.set_size(size, window, cx);
            }
            dock.set_panel(panel, window, cx);
            dock.set_open(open, window, cx);
            dock
        }));
        self.update_toggle_button_tab_panels(window, cx);
    }

    /// Reset all docks
    pub fn reset(&mut self, _window: &mut Window, cx: &mut Context<Self>) {
        self.left_dock = None;
        self.right_dock = None;
        self.bottom_dock = None;
        cx.notify();
    }

    /// Set locked state of the dock area, if locked, the dock area cannot be split or move, but allows to resize panels.
    pub fn set_locked(&mut self, locked: bool, _window: &mut Window, _cx: &mut App) {
        self.is_locked = locked;
    }

    /// Determine if the dock area is locked.
    pub fn is_locked(&self) -> bool {
        self.is_locked
    }

    /// Determine if the dock area has a dock at the given placement.
    pub fn has_dock(&self, placement: DockPlacement) -> bool {
        match placement {
            DockPlacement::Left => self.left_dock.is_some(),
            DockPlacement::Bottom => self.bottom_dock.is_some(),
            DockPlacement::Right => self.right_dock.is_some(),
            DockPlacement::Center => false,
        }
    }

    /// Determine if the dock at the given placement is open.
    pub fn is_dock_open(&self, placement: DockPlacement, cx: &App) -> bool {
        match placement {
            DockPlacement::Left => self
                .left_dock
                .as_ref()
                .map(|dock| dock.read(cx).is_open())
                .unwrap_or(false),
            DockPlacement::Bottom => self
                .bottom_dock
                .as_ref()
                .map(|dock| dock.read(cx).is_open())
                .unwrap_or(false),
            DockPlacement::Right => self
                .right_dock
                .as_ref()
                .map(|dock| dock.read(cx).is_open())
                .unwrap_or(false),
            DockPlacement::Center => false,
        }
    }

    /// Set the dock at the given placement to be open or closed.
    ///
    /// Only the left, bottom, right dock can be toggled.
    pub fn set_dock_collapsible(
        &mut self,
        collapsible_edges: Edges<bool>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        if let Some(left_dock) = self.left_dock.as_ref() {
            left_dock.update(cx, |dock, cx| {
                dock.set_collapsible(collapsible_edges.left, window, cx);
            });
        }

        if let Some(bottom_dock) = self.bottom_dock.as_ref() {
            bottom_dock.update(cx, |dock, cx| {
                dock.set_collapsible(collapsible_edges.bottom, window, cx);
            });
        }

        if let Some(right_dock) = self.right_dock.as_ref() {
            right_dock.update(cx, |dock, cx| {
                dock.set_collapsible(collapsible_edges.right, window, cx);
            });
        }
    }

    /// Determine if the dock at the given placement is collapsible.
    pub fn is_dock_collapsible(&self, placement: DockPlacement, cx: &App) -> bool {
        match placement {
            DockPlacement::Left => self
                .left_dock
                .as_ref()
                .map(|dock| dock.read(cx).collapsible)
                .unwrap_or(false),
            DockPlacement::Bottom => self
                .bottom_dock
                .as_ref()
                .map(|dock| dock.read(cx).collapsible)
                .unwrap_or(false),
            DockPlacement::Right => self
                .right_dock
                .as_ref()
                .map(|dock| dock.read(cx).collapsible)
                .unwrap_or(false),
            DockPlacement::Center => false,
        }
    }

    pub fn toggle_dock(
        &self,
        placement: DockPlacement,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let dock = match placement {
            DockPlacement::Left => &self.left_dock,
            DockPlacement::Bottom => &self.bottom_dock,
            DockPlacement::Right => &self.right_dock,
            DockPlacement::Center => return,
        };

        if let Some(dock) = dock {
            dock.update(cx, |view, cx| {
                view.toggle_open(window, cx);
            })
        }
    }

    /// Add a panel item to the dock area at the given placement.
    ///
    /// If the left, bottom, right dock is not present, it will set the dock at the placement.
    pub fn add_panel(
        &mut self,
        panel: Arc<dyn PanelView>,
        placement: DockPlacement,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let weak_self = cx.entity().downgrade();

        match placement {
            DockPlacement::Left => {
                if let Some(dock) = self.left_dock.as_ref() {
                    dock.update(cx, |dock, cx| dock.add_panel(panel, window, cx))
                } else {
                    self.set_left_dock(
                        DockItem::tabs(vec![panel], None, &weak_self, window, cx),
                        Some(px(320.)),
                        true,
                        window,
                        cx,
                    );
                }
            }
            DockPlacement::Bottom => {
                if let Some(dock) = self.bottom_dock.as_ref() {
                    dock.update(cx, |dock, cx| dock.add_panel(panel, window, cx))
                } else {
                    self.set_bottom_dock(
                        DockItem::tabs(vec![panel], None, &weak_self, window, cx),
                        None,
                        true,
                        window,
                        cx,
                    );
                }
            }
            DockPlacement::Right => {
                self.set_right_dock(
                    DockItem::tabs(vec![panel], None, &weak_self, window, cx),
                    Some(px(320.)),
                    true,
                    window,
                    cx,
                );
            }
            DockPlacement::Center => {
                self.items
                    .add_panel(panel, &cx.entity().downgrade(), window, cx);
            }
        }
    }

    /// Subscribe event on the panels
    fn subscribe_item(&mut self, item: &DockItem, window: &mut Window, cx: &mut Context<Self>) {
        match item {
            DockItem::Split { items, view, .. } => {
                for item in items {
                    self.subscribe_item(item, window, cx);
                }

                self.subscriptions.push(cx.subscribe_in(
                    view,
                    window,
                    move |_, _, event, window, cx| {
                        if let PanelEvent::LayoutChanged = event {
                            cx.spawn_in(window, async move |view, window| {
                                _ = view.update_in(window, |view, window, cx| {
                                    view.update_toggle_button_tab_panels(window, cx)
                                });
                            })
                            .detach();

                            cx.emit(DockEvent::LayoutChanged);
                        }
                    },
                ));
            }
            DockItem::Tabs { .. } => {
                // We subscribe to the tab panel event in StackPanel's insert_panel
            }
            DockItem::Panel { .. } => {
                // Not supported
            }
        }
    }

    /// Subscribe zoom event on the panel
    pub(crate) fn subscribe_panel<P: Panel>(
        &mut self,
        view: &Entity<P>,
        window: &mut Window,
        cx: &mut Context<DockArea>,
    ) {
        let subscription =
            cx.subscribe_in(
                view,
                window,
                move |_this, panel, event, window, cx| match event {
                    PanelEvent::ZoomIn => {
                        let panel = panel.clone();
                        cx.spawn_in(window, async move |view, window| {
                            view.update_in(window, |view, window, cx| {
                                view.set_zoomed_in(panel, window, cx);
                                cx.notify();
                            })
                            .ok();
                        })
                        .detach();
                    }
                    PanelEvent::ZoomOut => {
                        cx.spawn_in(window, async move |view, window| {
                            _ = view.update_in(window, |view, window, cx| {
                                view.set_zoomed_out(window, cx);
                            });
                        })
                        .detach();
                    }
                    PanelEvent::LayoutChanged => {
                        cx.spawn_in(window, async move |view, window| {
                            view.update_in(window, |view, window, cx| {
                                view.update_toggle_button_tab_panels(window, cx)
                            })
                            .ok();
                        })
                        .detach();
                        // Emit layout changed event for dock
                        cx.emit(DockEvent::LayoutChanged);
                    }
                },
            );

        self.subscriptions.push(subscription);
    }

    pub fn set_zoomed_in<P: Panel>(
        &mut self,
        panel: Entity<P>,
        _: &mut Window,
        cx: &mut Context<Self>,
    ) {
        self.zoom_view = Some(panel.into());
        cx.notify();
    }

    pub fn set_zoomed_out(&mut self, _window: &mut Window, cx: &mut Context<Self>) {
        self.zoom_view = None;
        cx.notify();
    }

    fn render_items(&self, _window: &mut Window, _cx: &mut Context<Self>) -> AnyElement {
        match &self.items {
            DockItem::Split { view, .. } => view.clone().into_any_element(),
            DockItem::Tabs { view, .. } => view.clone().into_any_element(),
            DockItem::Panel { view, .. } => view.clone().view().into_any_element(),
        }
    }

    pub fn update_toggle_button_tab_panels(
        &mut self,
        _window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        // Left toggle button
        self.toggle_button_panels.left = self
            .items
            .left_top_tab_panel(cx)
            .map(|view| view.entity_id());

        // Right toggle button
        self.toggle_button_panels.right = self
            .items
            .right_top_tab_panel(cx)
            .map(|view| view.entity_id());

        // Bottom toggle button
        self.toggle_button_panels.bottom = self
            .bottom_dock
            .as_ref()
            .and_then(|dock| dock.read(cx).panel.left_top_tab_panel(cx))
            .map(|view| view.entity_id());
    }

    pub fn focus_tab_panel(&mut self, window: &mut Window, cx: &mut App) {
        self.items.focus_tab_panel(window, cx);
    }
}

impl EventEmitter<DockEvent> for DockArea {}

impl Render for DockArea {
    fn render(&mut self, window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
        let view = cx.entity().clone();

        div()
            .id("dock-area")
            .relative()
            .size_full()
            .on_prepaint(move |bounds, _, cx| view.update(cx, |r, _| r.bounds = bounds))
            .map(|this| {
                if let Some(zoom_view) = self.zoom_view.clone() {
                    this.child(zoom_view)
                } else {
                    // render dock
                    this.child(
                        div()
                            .flex()
                            .flex_row()
                            .size_full()
                            // Left dock
                            .when_some(self.left_dock.clone(), |this, dock| {
                                this.child(div().flex().flex_none().child(dock))
                            })
                            // Center
                            .child(
                                div()
                                    .flex()
                                    .flex_1()
                                    .flex_col()
                                    // Top center
                                    .child(div().flex_1().child(self.render_items(window, cx)))
                                    // Bottom Dock
                                    .when_some(self.bottom_dock.clone(), |this, dock| {
                                        this.child(dock)
                                    }),
                            )
                            // Right Dock
                            .when_some(self.right_dock.clone(), |this, dock| {
                                this.child(div().flex().flex_none().child(dock))
                            }),
                    )
                }
            })
    }
}
