use std::sync::Arc;

use gpui::{
    div, prelude::FluentBuilder, rems, AnchorCorner, AppContext, DefiniteLength, DismissEvent,
    DragMoveEvent, Empty, EventEmitter, FocusHandle, FocusableView, InteractiveElement as _,
    IntoElement, ParentElement, Pixels, Render, ScrollHandle, StatefulInteractiveElement, Styled,
    View, ViewContext, VisualContext as _, WeakView, WindowContext,
};
use rust_i18n::t;

use crate::{
    button::Button,
    h_flex,
    popup_menu::{PopupMenu, PopupMenuExt},
    tab::{Tab, TabBar},
    theme::ActiveTheme,
    tooltip::Tooltip,
    v_flex, AxisExt, IconName, Placement, Selectable, Sizable, StyledExt,
};

use super::{ClosePanel, DockArea, Panel, PanelView, StackPanel, ToggleZoom};

pub enum PanelEvent {
    ZoomIn,
    ZoomOut,
}

#[derive(Clone)]
pub(crate) struct DragPanel {
    pub(crate) panel: Arc<dyn PanelView>,
    pub(crate) tab_panel: View<TabPanel>,
}

impl DragPanel {
    pub(crate) fn new(panel: Arc<dyn PanelView>, tab_panel: View<TabPanel>) -> Self {
        Self { panel, tab_panel }
    }
}

impl Render for DragPanel {
    fn render(&mut self, cx: &mut ViewContext<Self>) -> impl IntoElement {
        div()
            .id("drag-panel")
            .cursor_grab()
            .py_1()
            .px_3()
            .w_24()
            .overflow_hidden()
            .whitespace_nowrap()
            .border_1()
            .border_color(cx.theme().border)
            .rounded_md()
            .bg(cx.theme().tab_active)
            .opacity(0.75)
            .child(self.panel.title(cx))
    }
}

pub struct TabPanel {
    focus_handle: FocusHandle,
    dock_area: WeakView<DockArea>,
    stack_panel: Option<View<StackPanel>>,
    panels: Vec<Arc<dyn PanelView>>,
    active_ix: usize,
    tab_bar_scroll_handle: ScrollHandle,

    is_zoomed: bool,

    /// When drag move, will get the placement of the panel to be split
    will_split_placement: Option<Placement>,
}

impl TabPanel {
    pub fn new(
        stack_panel: Option<View<StackPanel>>,
        dock_area: WeakView<DockArea>,
        cx: &mut ViewContext<Self>,
    ) -> Self {
        Self {
            focus_handle: cx.focus_handle(),
            dock_area,
            stack_panel,
            panels: Vec::new(),
            active_ix: 0,
            tab_bar_scroll_handle: ScrollHandle::new(),
            will_split_placement: None,
            is_zoomed: false,
        }
    }

    pub(super) fn set_parent(&mut self, parent: View<StackPanel>) {
        self.stack_panel = Some(parent);
    }

    /// Return current active_panel View
    pub fn active_panel(&self) -> Option<Arc<dyn PanelView>> {
        self.panels.get(self.active_ix).cloned()
    }

    fn set_active_ix(&mut self, ix: usize, cx: &mut ViewContext<Self>) {
        self.active_ix = ix;
        self.tab_bar_scroll_handle.scroll_to_item(ix);
        cx.notify();
    }

    /// Return the existing panel view by type.
    pub fn panel<P: Panel>(&self, cx: &WindowContext) -> Option<View<P>> {
        self.panels.iter().find_map(|p| {
            if let Ok(p) = p.view().downcast::<P>() {
                Some(p)
            } else {
                if let Ok(stack) = p.view().downcast::<StackPanel>() {
                    stack.read(cx).panel::<P>(cx)
                } else {
                    None
                }
            }
        })
    }

    /// Add a panel to the end of the tabs
    pub fn add_panel(&mut self, panel: Arc<dyn PanelView>, cx: &mut ViewContext<Self>) {
        if self
            .panels
            .iter()
            .any(|p| p.view().entity_id() == panel.view().entity_id())
        {
            return;
        }

        self.panels.push(panel);
        // set the active panel to the new panel
        self.set_active_ix(self.panels.len() - 1, cx);
        cx.notify();
    }

    /// Add panel to try to split
    pub fn add_panel_at(
        &mut self,
        panel: Arc<dyn PanelView>,
        placement: Placement,
        size: Option<Pixels>,
        cx: &mut ViewContext<Self>,
    ) {
        self.will_split_placement = Some(placement);
        self.split_panel(panel, placement, size, cx);
        cx.notify();
    }

    fn insert_panel_at(
        &mut self,
        panel: Arc<dyn PanelView>,
        ix: usize,
        cx: &mut ViewContext<Self>,
    ) {
        if self
            .panels
            .iter()
            .any(|p| p.view().entity_id() == panel.view().entity_id())
        {
            return;
        }

        self.panels.insert(ix, panel);
        self.set_active_ix(ix, cx);
        cx.notify();
    }

    /// Remove a panel from the tab panel
    pub fn remove_panel(&mut self, panel: Arc<dyn PanelView>, cx: &mut ViewContext<Self>) {
        self.detach_panel(panel, cx);
        self.remove_self_if_empty(cx)
    }

    fn detach_panel(&mut self, panel: Arc<dyn PanelView>, cx: &mut ViewContext<Self>) {
        let panel_view = panel.view();
        self.panels.retain(|p| p.view() != panel_view);
        if self.active_ix >= self.panels.len() {
            self.set_active_ix(self.panels.len().saturating_sub(1), cx)
        }
    }

    /// Check to remove self from the parent StackPanel, if there is no panel left
    fn remove_self_if_empty(&self, cx: &mut ViewContext<Self>) {
        if !self.panels.is_empty() {
            return;
        }

        let tab_view = cx.view().clone();
        if let Some(stack_panel) = self.stack_panel.as_ref() {
            stack_panel.update(cx, |view, cx| {
                view.remove_panel(tab_view, cx);
            })
        }
    }

    fn render_menu_button(&self, cx: &mut ViewContext<Self>) -> impl IntoElement {
        let is_zoomed = self.is_zoomed;
        let closeable = self.closeable(cx);
        let view = cx.view().clone();
        let build_popup_menu = move |this, cx: &WindowContext| view.read(cx).popup_menu(this, cx);

        h_flex()
            .gap_2()
            .occlude()
            .items_center()
            .when(self.is_zoomed, |this| {
                this.child(
                    Button::new("zoom", cx)
                        .icon(IconName::Minimize)
                        .xsmall()
                        .ghost()
                        .tooltip(t!("Dock.Zoom Out"))
                        .on_click(
                            cx.listener(|view, _, cx| view.on_action_toggle_zoom(&ToggleZoom, cx)),
                        ),
                )
            })
            .child(
                Button::new("menu", cx)
                    .icon(IconName::Ellipsis)
                    .xsmall()
                    .ghost()
                    .popup_menu(move |this, cx| {
                        build_popup_menu(this, cx)
                            .menu(
                                if is_zoomed {
                                    t!("Dock.Zoom Out")
                                } else {
                                    t!("Dock.Zoom In")
                                },
                                Box::new(ToggleZoom),
                            )
                            .when(closeable, |this| {
                                this.separator()
                                    .menu(t!("Dock.Close"), Box::new(ClosePanel))
                            })
                    })
                    .anchor(AnchorCorner::TopRight),
            )
    }

    fn render_tabs(&self, cx: &mut ViewContext<Self>) -> impl IntoElement {
        let view = cx.view().clone();

        if self.panels.len() == 1 {
            let panel = self.panels.get(0).unwrap();
            let title = panel.title(cx);

            return h_flex()
                .justify_between()
                .items_center()
                .line_height(rems(1.0))
                .pr_3()
                .child(
                    div()
                        .id("tab")
                        .py_2()
                        .px_3()
                        .min_w_16()
                        .overflow_hidden()
                        .text_ellipsis()
                        .child(title.clone())
                        .tooltip(move |cx| Tooltip::new(title.clone(), cx))
                        .on_drag(
                            DragPanel {
                                panel: panel.clone(),
                                tab_panel: view,
                            },
                            |drag, cx| {
                                cx.stop_propagation();
                                cx.new_view(|_| drag.clone())
                            },
                        ),
                )
                .child(self.render_menu_button(cx))
                .into_any_element();
        }

        let tabs_count = self.panels.len();

        TabBar::new("tab-bar")
            .track_scroll(self.tab_bar_scroll_handle.clone())
            .children(self.panels.iter().enumerate().map(|(ix, panel)| {
                let active = ix == self.active_ix;
                Tab::new(("tab", ix), panel.title(cx))
                    .py_2()
                    .selected(active)
                    .on_click(cx.listener(move |view, _, cx| {
                        view.set_active_ix(ix, cx);
                    }))
                    .on_drag(DragPanel::new(panel.clone(), view.clone()), |drag, cx| {
                        cx.stop_propagation();
                        cx.new_view(|_| drag.clone())
                    })
                    .drag_over::<DragPanel>(|this, _, cx| {
                        this.rounded_l_none()
                            .border_l_2()
                            .border_r_0()
                            .border_color(cx.theme().drag_border)
                    })
                    .on_drop(cx.listener(move |this, drag: &DragPanel, cx| {
                        this.will_split_placement = None;
                        this.on_drop(drag, Some(ix), cx)
                    }))
            }))
            .child(
                // empty space to allow move to last tab right
                div()
                    .id("tab-bar-empty-space")
                    .h_full()
                    .flex_grow()
                    .min_w_16()
                    .drag_over::<DragPanel>(|this, _, cx| this.bg(cx.theme().drop_target))
                    .on_drop(cx.listener(move |this, drag: &DragPanel, cx| {
                        this.will_split_placement = None;

                        let ix = if drag.tab_panel == view {
                            Some(tabs_count - 1)
                        } else {
                            None
                        };

                        this.on_drop(drag, ix, cx)
                    })),
            )
            .suffix(
                h_flex()
                    .items_center()
                    .top_0()
                    .right_0()
                    .border_l_1()
                    .border_b_1()
                    .h_full()
                    .border_color(cx.theme().border)
                    .bg(cx.theme().tab_bar)
                    .px_3()
                    .child(self.render_menu_button(cx)),
            )
            .into_any_element()
    }

    fn render_active_panel(&self, cx: &mut ViewContext<Self>) -> impl IntoElement {
        self.active_panel()
            .map(|panel| {
                div()
                    .id("tab-content")
                    .group("")
                    .overflow_y_scroll()
                    .overflow_x_hidden()
                    .flex_1()
                    .child(panel.view())
                    .on_drag_move(cx.listener(Self::on_panel_drag_move))
                    .child(
                        div()
                            .invisible()
                            .absolute()
                            .bg(cx.theme().drop_target)
                            .map(|this| match self.will_split_placement {
                                Some(placement) => {
                                    let size = DefiniteLength::Fraction(0.25);
                                    match placement {
                                        Placement::Left => this.left_0().top_0().bottom_0().w(size),
                                        Placement::Right => {
                                            this.right_0().top_0().bottom_0().w(size)
                                        }
                                        Placement::Top => this.top_0().left_0().right_0().h(size),
                                        Placement::Bottom => {
                                            this.bottom_0().left_0().right_0().h(size)
                                        }
                                    }
                                }
                                None => this.top_0().left_0().size_full(),
                            })
                            .group_drag_over::<DragPanel>("", |this| this.visible())
                            .on_drop(cx.listener(|this, drag: &DragPanel, cx| {
                                this.on_drop(drag, None, cx)
                            })),
                    )
                    .into_any_element()
            })
            .unwrap_or(Empty {}.into_any_element())
    }

    /// Calculate the split direction based on the current mouse position
    fn on_panel_drag_move(&mut self, drag: &DragMoveEvent<DragPanel>, cx: &mut ViewContext<Self>) {
        let bounds = drag.bounds;
        let position = drag.event.position;

        // Check the mouse position to determine the split direction
        if position.x < bounds.left() + bounds.size.width * 0.25 {
            self.will_split_placement = Some(Placement::Left);
        } else if position.x > bounds.left() + bounds.size.width * 0.75 {
            self.will_split_placement = Some(Placement::Right);
        } else if position.y < bounds.top() + bounds.size.height * 0.25 {
            self.will_split_placement = Some(Placement::Top);
        } else if position.y > bounds.top() + bounds.size.height * 0.75 {
            self.will_split_placement = Some(Placement::Bottom);
        } else {
            // center to merge into the current tab
            self.will_split_placement = None;
        }
        cx.notify()
    }

    fn on_drop(&mut self, drag: &DragPanel, ix: Option<usize>, cx: &mut ViewContext<Self>) {
        let panel = drag.panel.clone();
        let is_same_tab = drag.tab_panel == *cx.view();

        // If target is same tab, and it is only one panel, do nothing.
        if is_same_tab && ix.is_none() {
            if self.will_split_placement.is_none() {
                return;
            } else {
                if self.panels.len() == 1 {
                    return;
                }
            }
        }

        // Here is looks like remove_panel on a same item, but it differnece.
        //
        // We must to split it to remove_panel, unless it will be crash by error:
        // Cannot update ui::dock::tab_panel::TabPanel while it is already being updated
        if is_same_tab {
            self.detach_panel(panel.clone(), cx);
        } else {
            let _ = drag.tab_panel.update(cx, |view, cx| {
                view.detach_panel(panel.clone(), cx);
                view.remove_self_if_empty(cx);
            });
        }

        // Insert into new tabs
        if let Some(placement) = self.will_split_placement {
            self.split_panel(panel, placement, None, cx);
        } else {
            if let Some(ix) = ix {
                self.insert_panel_at(panel, ix, cx)
            } else {
                self.add_panel(panel, cx)
            }
        }

        self.remove_self_if_empty(cx);
    }

    /// Add panel with split placement
    fn split_panel(
        &self,
        panel: Arc<dyn PanelView>,
        placement: Placement,
        size: Option<Pixels>,
        cx: &mut ViewContext<Self>,
    ) {
        let dock_area = self.dock_area.clone();
        // wrap the panel in a TabPanel
        let new_tab_panel = cx.new_view(|cx| Self::new(None, dock_area.clone(), cx));
        new_tab_panel.update(cx, |view, cx| {
            view.add_panel(panel, cx);
        });

        let stack_panel = self.stack_panel.as_ref().unwrap();
        let parent_axis = stack_panel.read(cx).axis;
        let ix = stack_panel
            .read(cx)
            .index_of_panel(cx.view().clone())
            .unwrap_or_default();

        if parent_axis.is_vertical() && placement.is_vertical() {
            stack_panel.update(cx, |view, cx| {
                view.insert_panel_at(new_tab_panel, ix, placement, size, dock_area.clone(), cx);
            });
        } else if parent_axis.is_horizontal() && placement.is_horizontal() {
            stack_panel.update(cx, |view, cx| {
                view.insert_panel_at(new_tab_panel, ix, placement, size, dock_area.clone(), cx);
            });
        } else {
            // 1. Create new StackPanel with new axis
            // 2. Move cx.view() from parent StackPanel to the new StackPanel
            // 3. Add the new TabPanel to the new StackPanel at the correct index
            // 4. Add new StackPanel to the parent StackPanel at the correct index
            let tab_panel = cx.view().clone();

            // Try to use the old stack panel, not just create a new one, to avoid too many nested stack panels
            let new_stack_panel = if stack_panel.read(cx).panels_len() <= 1 {
                stack_panel.update(cx, |view, cx| {
                    view.remove_all_panels(cx);
                    view.set_axis(placement.axis(), cx);
                });
                stack_panel.clone()
            } else {
                cx.new_view(|cx| {
                    let mut panel = StackPanel::new(placement.axis(), cx);
                    panel.parent = Some(stack_panel.clone());
                    panel
                })
            };

            new_stack_panel.update(cx, |view, cx| match placement {
                Placement::Left | Placement::Top => {
                    view.add_panel(new_tab_panel, size, dock_area.clone(), cx);
                    view.add_panel(tab_panel.clone(), None, dock_area.clone(), cx);
                }
                Placement::Right | Placement::Bottom => {
                    view.add_panel(tab_panel.clone(), None, dock_area.clone(), cx);
                    view.add_panel(new_tab_panel, size, dock_area.clone(), cx);
                }
            });

            if *stack_panel != new_stack_panel {
                stack_panel.update(cx, |view, cx| {
                    view.replace_panel(tab_panel.clone(), new_stack_panel.clone(), cx);
                });
            }

            cx.spawn(|_, mut cx| async move {
                cx.update(|cx| tab_panel.update(cx, |view, cx| view.remove_self_if_empty(cx)))
            })
            .detach()
        }
    }

    fn on_action_toggle_zoom(&mut self, _: &ToggleZoom, cx: &mut ViewContext<Self>) {
        self.is_zoomed = !self.is_zoomed;
        if self.is_zoomed {
            cx.emit(PanelEvent::ZoomIn)
        } else {
            cx.emit(PanelEvent::ZoomOut)
        }
    }

    fn on_action_close_panel(&mut self, _: &ClosePanel, cx: &mut ViewContext<Self>) {
        if let Some(panel) = self.active_panel() {
            self.remove_panel(panel, cx);
        }
    }
}

impl Panel for TabPanel {
    fn closeable(&self, cx: &WindowContext) -> bool {
        self.active_panel()
            .map(|panel| panel.closeable(cx))
            .unwrap_or(false)
    }

    fn popup_menu(&self, menu: PopupMenu, cx: &WindowContext) -> PopupMenu {
        if let Some(panel) = self.active_panel() {
            panel.popup_menu(menu, cx)
        } else {
            menu
        }
    }
}
impl FocusableView for TabPanel {
    fn focus_handle(&self, _cx: &AppContext) -> gpui::FocusHandle {
        // FIXME: Delegate to the active panel
        self.focus_handle.clone()
    }
}
impl EventEmitter<DismissEvent> for TabPanel {}
impl EventEmitter<PanelEvent> for TabPanel {}
impl Render for TabPanel {
    fn render(&mut self, cx: &mut ViewContext<Self>) -> impl gpui::IntoElement {
        v_flex()
            .id("tab-panel")
            .track_focus(&self.focus_handle)
            .on_action(cx.listener(Self::on_action_toggle_zoom))
            .on_action(cx.listener(Self::on_action_close_panel))
            .size_full()
            .overflow_hidden()
            .bg(cx.theme().background)
            .child(self.render_tabs(cx))
            .child(self.render_active_panel(cx))
    }
}