use std::{ops::ControlFlow, path::PathBuf, sync::Arc};

use crate::TerminalView;
use collections::{HashMap, HashSet};
use db::kvp::KEY_VALUE_STORE;
use futures::future::join_all;
use gpui::{
    actions, Action, AppContext, AsyncWindowContext, DismissEvent, Entity, EventEmitter,
    ExternalPaths, FocusHandle, FocusableView, IntoElement, Model, ParentElement, Pixels, Render,
    Styled, Subscription, Task, View, ViewContext, VisualContext, WeakView, WindowContext,
};
use itertools::Itertools;
use project::{Fs, ProjectEntryId};
use search::{buffer_search::DivRegistrar, BufferSearchBar};
use serde::{Deserialize, Serialize};
use settings::Settings;
use task::{RevealStrategy, Shell, SpawnInTerminal, TaskId, TerminalWorkDir};
use terminal::{
    terminal_settings::{TerminalDockPosition, TerminalSettings},
    Terminal,
};
use ui::{
    h_flex, ButtonCommon, Clickable, ContextMenu, FluentBuilder, IconButton, IconSize, Selectable,
    Tooltip,
};
use util::{ResultExt, TryFutureExt};
use workspace::{
    dock::{DockPosition, Panel, PanelEvent},
    item::SerializableItem,
    pane,
    ui::IconName,
    DraggedTab, ItemId, NewTerminal, Pane, ToggleZoom, Workspace,
};

use anyhow::Result;

const TERMINAL_PANEL_KEY: &str = "TerminalPanel";

actions!(terminal_panel, [ToggleFocus]);

pub fn init(cx: &mut AppContext) {
    cx.observe_new_views(
        |workspace: &mut Workspace, _: &mut ViewContext<Workspace>| {
            workspace.register_action(TerminalPanel::new_terminal);
            workspace.register_action(TerminalPanel::open_terminal);
            workspace.register_action(|workspace, _: &ToggleFocus, cx| {
                if workspace
                    .panel::<TerminalPanel>(cx)
                    .as_ref()
                    .is_some_and(|panel| panel.read(cx).enabled)
                {
                    workspace.toggle_panel_focus::<TerminalPanel>(cx);
                }
            });
        },
    )
    .detach();
}

pub struct TerminalPanel {
    pane: View<Pane>,
    fs: Arc<dyn Fs>,
    workspace: WeakView<Workspace>,
    width: Option<Pixels>,
    height: Option<Pixels>,
    pending_serialization: Task<Option<()>>,
    pending_terminals_to_add: usize,
    _subscriptions: Vec<Subscription>,
    deferred_tasks: HashMap<TaskId, Task<()>>,
    enabled: bool,
}

impl TerminalPanel {
    fn new(workspace: &Workspace, cx: &mut ViewContext<Self>) -> Self {
        let pane = cx.new_view(|cx| {
            let mut pane = Pane::new(
                workspace.weak_handle(),
                workspace.project().clone(),
                Default::default(),
                None,
                NewTerminal.boxed_clone(),
                cx,
            );
            pane.set_can_split(false, cx);
            pane.set_can_navigate(false, cx);
            pane.display_nav_history_buttons(None);
            pane.set_should_display_tab_bar(|_| true);
            pane.set_render_tab_bar_buttons(cx, move |pane, cx| {
                h_flex()
                    .gap_2()
                    .child(
                        IconButton::new("plus", IconName::Plus)
                            .icon_size(IconSize::Small)
                            .on_click(cx.listener(|pane, _, cx| {
                                let focus_handle = pane.focus_handle(cx);
                                let menu = ContextMenu::build(cx, |menu, _| {
                                    menu.action(
                                        "New Terminal",
                                        workspace::NewTerminal.boxed_clone(),
                                    )
                                    .entry(
                                        "Spawn task",
                                        Some(tasks_ui::Spawn::modal().boxed_clone()),
                                        move |cx| {
                                            // We want the focus to go back to terminal panel once task modal is dismissed,
                                            // hence we focus that first. Otherwise, we'd end up without a focused element, as
                                            // context menu will be gone the moment we spawn the modal.
                                            cx.focus(&focus_handle);
                                            cx.dispatch_action(
                                                tasks_ui::Spawn::modal().boxed_clone(),
                                            );
                                        },
                                    )
                                });
                                cx.subscribe(&menu, |pane, _, _: &DismissEvent, _| {
                                    pane.new_item_menu = None;
                                })
                                .detach();
                                pane.new_item_menu = Some(menu);
                            }))
                            .tooltip(|cx| Tooltip::text("New...", cx)),
                    )
                    .when_some(pane.new_item_menu.as_ref(), |el, new_item_menu| {
                        el.child(Pane::render_menu_overlay(new_item_menu))
                    })
                    .child({
                        let zoomed = pane.is_zoomed();
                        IconButton::new("toggle_zoom", IconName::Maximize)
                            .icon_size(IconSize::Small)
                            .selected(zoomed)
                            .selected_icon(IconName::Minimize)
                            .on_click(cx.listener(|pane, _, cx| {
                                pane.toggle_zoom(&workspace::ToggleZoom, cx);
                            }))
                            .tooltip(move |cx| {
                                Tooltip::for_action(
                                    if zoomed { "Zoom Out" } else { "Zoom In" },
                                    &ToggleZoom,
                                    cx,
                                )
                            })
                    })
                    .into_any_element()
            });

            let workspace = workspace.weak_handle();
            pane.set_custom_drop_handle(cx, move |pane, dropped_item, cx| {
                if let Some(tab) = dropped_item.downcast_ref::<DraggedTab>() {
                    let item = if &tab.pane == cx.view() {
                        pane.item_for_index(tab.ix)
                    } else {
                        tab.pane.read(cx).item_for_index(tab.ix)
                    };
                    if let Some(item) = item {
                        if item.downcast::<TerminalView>().is_some() {
                            return ControlFlow::Continue(());
                        } else if let Some(project_path) = item.project_path(cx) {
                            if let Some(entry_path) = workspace
                                .update(cx, |workspace, cx| {
                                    workspace
                                        .project()
                                        .read(cx)
                                        .absolute_path(&project_path, cx)
                                })
                                .log_err()
                                .flatten()
                            {
                                add_paths_to_terminal(pane, &[entry_path], cx);
                            }
                        }
                    }
                } else if let Some(&entry_id) = dropped_item.downcast_ref::<ProjectEntryId>() {
                    if let Some(entry_path) = workspace
                        .update(cx, |workspace, cx| {
                            let project = workspace.project().read(cx);
                            project
                                .path_for_entry(entry_id, cx)
                                .and_then(|project_path| project.absolute_path(&project_path, cx))
                        })
                        .log_err()
                        .flatten()
                    {
                        add_paths_to_terminal(pane, &[entry_path], cx);
                    }
                } else if let Some(paths) = dropped_item.downcast_ref::<ExternalPaths>() {
                    add_paths_to_terminal(pane, paths.paths(), cx);
                }

                ControlFlow::Break(())
            });
            let buffer_search_bar = cx.new_view(search::BufferSearchBar::new);
            pane.toolbar()
                .update(cx, |toolbar, cx| toolbar.add_item(buffer_search_bar, cx));
            pane
        });
        let subscriptions = vec![
            cx.observe(&pane, |_, _, cx| cx.notify()),
            cx.subscribe(&pane, Self::handle_pane_event),
        ];
        let project = workspace.project().read(cx);
        let enabled = project.is_local() || project.supports_remote_terminal(cx);
        let this = Self {
            pane,
            fs: workspace.app_state().fs.clone(),
            workspace: workspace.weak_handle(),
            pending_serialization: Task::ready(None),
            width: None,
            height: None,
            pending_terminals_to_add: 0,
            deferred_tasks: HashMap::default(),
            _subscriptions: subscriptions,
            enabled,
        };
        this
    }

    pub async fn load(
        workspace: WeakView<Workspace>,
        mut cx: AsyncWindowContext,
    ) -> Result<View<Self>> {
        let serialized_panel = cx
            .background_executor()
            .spawn(async move { KEY_VALUE_STORE.read_kvp(TERMINAL_PANEL_KEY) })
            .await
            .log_err()
            .flatten()
            .map(|panel| serde_json::from_str::<SerializedTerminalPanel>(&panel))
            .transpose()
            .log_err()
            .flatten();

        let (panel, pane, items) = workspace.update(&mut cx, |workspace, cx| {
            let panel = cx.new_view(|cx| TerminalPanel::new(workspace, cx));
            let items = if let Some((serialized_panel, database_id)) =
                serialized_panel.as_ref().zip(workspace.database_id())
            {
                panel.update(cx, |panel, cx| {
                    cx.notify();
                    panel.height = serialized_panel.height.map(|h| h.round());
                    panel.width = serialized_panel.width.map(|w| w.round());
                    panel.pane.update(cx, |_, cx| {
                        serialized_panel
                            .items
                            .iter()
                            .map(|item_id| {
                                TerminalView::deserialize(
                                    workspace.project().clone(),
                                    workspace.weak_handle(),
                                    database_id,
                                    *item_id,
                                    cx,
                                )
                            })
                            .collect::<Vec<_>>()
                    })
                })
            } else {
                Vec::new()
            };
            let pane = panel.read(cx).pane.clone();
            (panel, pane, items)
        })?;

        if let Some(workspace) = workspace.upgrade() {
            panel
                .update(&mut cx, |panel, cx| {
                    panel._subscriptions.push(cx.subscribe(
                        &workspace,
                        |terminal_panel, _, e, cx| {
                            if let workspace::Event::SpawnTask(spawn_in_terminal) = e {
                                terminal_panel.spawn_task(spawn_in_terminal, cx);
                            };
                        },
                    ))
                })
                .ok();
        }

        let pane = pane.downgrade();
        let items = futures::future::join_all(items).await;
        let mut alive_item_ids = Vec::new();
        pane.update(&mut cx, |pane, cx| {
            let active_item_id = serialized_panel
                .as_ref()
                .and_then(|panel| panel.active_item_id);
            let mut active_ix = None;
            for item in items {
                if let Some(item) = item.log_err() {
                    let item_id = item.entity_id().as_u64();
                    pane.add_item(Box::new(item), false, false, None, cx);
                    alive_item_ids.push(item_id as ItemId);
                    if Some(item_id) == active_item_id {
                        active_ix = Some(pane.items_len() - 1);
                    }
                }
            }

            if let Some(active_ix) = active_ix {
                pane.activate_item(active_ix, false, false, cx)
            }
        })?;

        // Since panels/docks are loaded outside from the workspace, we cleanup here, instead of through the workspace.
        if let Some(workspace) = workspace.upgrade() {
            let cleanup_task = workspace.update(&mut cx, |workspace, cx| {
                workspace
                    .database_id()
                    .map(|workspace_id| TerminalView::cleanup(workspace_id, alive_item_ids, cx))
            })?;
            if let Some(task) = cleanup_task {
                task.await.log_err();
            }
        }

        Ok(panel)
    }

    fn handle_pane_event(
        &mut self,
        _pane: View<Pane>,
        event: &pane::Event,
        cx: &mut ViewContext<Self>,
    ) {
        match event {
            pane::Event::ActivateItem { .. } => self.serialize(cx),
            pane::Event::RemoveItem { .. } => self.serialize(cx),
            pane::Event::Remove => cx.emit(PanelEvent::Close),
            pane::Event::ZoomIn => cx.emit(PanelEvent::ZoomIn),
            pane::Event::ZoomOut => cx.emit(PanelEvent::ZoomOut),

            pane::Event::AddItem { item } => {
                if let Some(workspace) = self.workspace.upgrade() {
                    let pane = self.pane.clone();
                    workspace.update(cx, |workspace, cx| item.added_to_pane(workspace, pane, cx))
                }
            }

            _ => {}
        }
    }

    pub fn open_terminal(
        workspace: &mut Workspace,
        action: &workspace::OpenTerminal,
        cx: &mut ViewContext<Workspace>,
    ) {
        let Some(terminal_panel) = workspace.panel::<Self>(cx) else {
            return;
        };

        let terminal_work_dir = workspace
            .project()
            .read(cx)
            .terminal_work_dir_for(Some(&action.working_directory), cx);

        terminal_panel
            .update(cx, |panel, cx| {
                panel.add_terminal(terminal_work_dir, None, RevealStrategy::Always, cx)
            })
            .detach_and_log_err(cx);
    }

    fn spawn_task(&mut self, spawn_in_terminal: &SpawnInTerminal, cx: &mut ViewContext<Self>) {
        let mut spawn_task = spawn_in_terminal.clone();
        // Set up shell args unconditionally, as tasks are always spawned inside of a shell.
        let Some((shell, mut user_args)) = (match spawn_in_terminal.shell.clone() {
            Shell::System => retrieve_system_shell().map(|shell| (shell, Vec::new())),
            Shell::Program(shell) => Some((shell, Vec::new())),
            Shell::WithArguments { program, args } => Some((program, args)),
        }) else {
            return;
        };
        #[cfg(target_os = "windows")]
        let windows_shell_type = to_windows_shell_type(&shell);

        #[cfg(not(target_os = "windows"))]
        {
            spawn_task.command_label = format!("{shell} -i -c `{}`", spawn_task.command_label);
        }
        #[cfg(target_os = "windows")]
        {
            use crate::terminal_panel::WindowsShellType;

            match windows_shell_type {
                WindowsShellType::Powershell => {
                    spawn_task.command_label = format!("{shell} -C `{}`", spawn_task.command_label)
                }
                WindowsShellType::Cmd => {
                    spawn_task.command_label = format!("{shell} /C `{}`", spawn_task.command_label)
                }
                WindowsShellType::Other => {
                    spawn_task.command_label =
                        format!("{shell} -i -c `{}`", spawn_task.command_label)
                }
            }
        }

        let task_command = std::mem::replace(&mut spawn_task.command, shell);
        let task_args = std::mem::take(&mut spawn_task.args);
        let combined_command = task_args
            .into_iter()
            .fold(task_command, |mut command, arg| {
                command.push(' ');
                #[cfg(not(target_os = "windows"))]
                command.push_str(&arg);
                #[cfg(target_os = "windows")]
                command.push_str(&to_windows_shell_variable(windows_shell_type, arg));
                command
            });

        #[cfg(not(target_os = "windows"))]
        user_args.extend(["-i".to_owned(), "-c".to_owned(), combined_command]);
        #[cfg(target_os = "windows")]
        {
            use crate::terminal_panel::WindowsShellType;

            match windows_shell_type {
                WindowsShellType::Powershell => {
                    user_args.extend(["-C".to_owned(), combined_command])
                }
                WindowsShellType::Cmd => user_args.extend(["/C".to_owned(), combined_command]),
                WindowsShellType::Other => {
                    user_args.extend(["-i".to_owned(), "-c".to_owned(), combined_command])
                }
            }
        }
        spawn_task.args = user_args;
        let spawn_task = spawn_task;

        let allow_concurrent_runs = spawn_in_terminal.allow_concurrent_runs;
        let use_new_terminal = spawn_in_terminal.use_new_terminal;

        if allow_concurrent_runs && use_new_terminal {
            self.spawn_in_new_terminal(spawn_task, cx)
                .detach_and_log_err(cx);
            return;
        }

        let terminals_for_task = self.terminals_for_task(&spawn_in_terminal.full_label, cx);
        if terminals_for_task.is_empty() {
            self.spawn_in_new_terminal(spawn_task, cx)
                .detach_and_log_err(cx);
            return;
        }
        let (existing_item_index, existing_terminal) = terminals_for_task
            .last()
            .expect("covered no terminals case above")
            .clone();
        if allow_concurrent_runs {
            debug_assert!(
                !use_new_terminal,
                "Should have handled 'allow_concurrent_runs && use_new_terminal' case above"
            );
            self.replace_terminal(spawn_task, existing_item_index, existing_terminal, cx);
        } else {
            self.deferred_tasks.insert(
                spawn_in_terminal.id.clone(),
                cx.spawn(|terminal_panel, mut cx| async move {
                    wait_for_terminals_tasks(terminals_for_task, &mut cx).await;
                    terminal_panel
                        .update(&mut cx, |terminal_panel, cx| {
                            if use_new_terminal {
                                terminal_panel
                                    .spawn_in_new_terminal(spawn_task, cx)
                                    .detach_and_log_err(cx);
                            } else {
                                terminal_panel.replace_terminal(
                                    spawn_task,
                                    existing_item_index,
                                    existing_terminal,
                                    cx,
                                );
                            }
                        })
                        .ok();
                }),
            );
        }
    }

    pub fn spawn_in_new_terminal(
        &mut self,
        spawn_task: SpawnInTerminal,
        cx: &mut ViewContext<Self>,
    ) -> Task<Result<Model<Terminal>>> {
        let reveal = spawn_task.reveal;
        self.add_terminal(spawn_task.cwd.clone(), Some(spawn_task), reveal, cx)
    }

    /// Create a new Terminal in the current working directory or the user's home directory
    fn new_terminal(
        workspace: &mut Workspace,
        _: &workspace::NewTerminal,
        cx: &mut ViewContext<Workspace>,
    ) {
        let Some(terminal_panel) = workspace.panel::<Self>(cx) else {
            return;
        };

        terminal_panel
            .update(cx, |this, cx| {
                this.add_terminal(None, None, RevealStrategy::Always, cx)
            })
            .detach_and_log_err(cx);
    }

    fn terminals_for_task(
        &self,
        label: &str,
        cx: &mut AppContext,
    ) -> Vec<(usize, View<TerminalView>)> {
        self.pane
            .read(cx)
            .items()
            .enumerate()
            .filter_map(|(index, item)| Some((index, item.act_as::<TerminalView>(cx)?)))
            .filter_map(|(index, terminal_view)| {
                let task_state = terminal_view.read(cx).terminal().read(cx).task()?;
                if &task_state.full_label == label {
                    Some((index, terminal_view))
                } else {
                    None
                }
            })
            .collect()
    }

    fn activate_terminal_view(&self, item_index: usize, cx: &mut WindowContext) {
        self.pane.update(cx, |pane, cx| {
            pane.activate_item(item_index, true, true, cx)
        })
    }

    fn add_terminal(
        &mut self,
        working_directory: Option<TerminalWorkDir>,
        spawn_task: Option<SpawnInTerminal>,
        reveal_strategy: RevealStrategy,
        cx: &mut ViewContext<Self>,
    ) -> Task<Result<Model<Terminal>>> {
        if !self.enabled {
            if spawn_task.is_none()
                || !matches!(
                    spawn_task.as_ref().unwrap().cwd,
                    Some(TerminalWorkDir::Ssh { .. })
                )
            {
                return Task::ready(Err(anyhow::anyhow!(
                    "terminal not yet supported for remote projects"
                )));
            }
        }

        let workspace = self.workspace.clone();
        self.pending_terminals_to_add += 1;

        cx.spawn(|terminal_panel, mut cx| async move {
            let pane = terminal_panel.update(&mut cx, |this, _| this.pane.clone())?;
            let result = workspace.update(&mut cx, |workspace, cx| {
                let working_directory = if let Some(working_directory) = working_directory {
                    Some(working_directory)
                } else {
                    let working_directory_strategy =
                        TerminalSettings::get_global(cx).working_directory.clone();
                    crate::get_working_directory(workspace, cx, working_directory_strategy)
                };

                let window = cx.window_handle();
                let terminal = workspace.project().update(cx, |project, cx| {
                    project.create_terminal(working_directory, spawn_task, window, cx)
                })?;
                let terminal_view = Box::new(cx.new_view(|cx| {
                    TerminalView::new(
                        terminal.clone(),
                        workspace.weak_handle(),
                        workspace.database_id(),
                        cx,
                    )
                }));
                pane.update(cx, |pane, cx| {
                    let focus = pane.has_focus(cx);
                    pane.add_item(terminal_view, true, focus, None, cx);
                });

                if reveal_strategy == RevealStrategy::Always {
                    workspace.focus_panel::<Self>(cx);
                }
                Ok(terminal)
            })?;
            terminal_panel.update(&mut cx, |this, cx| {
                this.pending_terminals_to_add = this.pending_terminals_to_add.saturating_sub(1);
                this.serialize(cx)
            })?;
            result
        })
    }

    fn serialize(&mut self, cx: &mut ViewContext<Self>) {
        let mut items_to_serialize = HashSet::default();
        let items = self
            .pane
            .read(cx)
            .items()
            .filter_map(|item| {
                let terminal_view = item.act_as::<TerminalView>(cx)?;
                if terminal_view.read(cx).terminal().read(cx).task().is_some() {
                    None
                } else {
                    let id = item.item_id().as_u64();
                    items_to_serialize.insert(id);
                    Some(id)
                }
            })
            .collect::<Vec<_>>();
        let active_item_id = self
            .pane
            .read(cx)
            .active_item()
            .map(|item| item.item_id().as_u64())
            .filter(|active_id| items_to_serialize.contains(active_id));
        let height = self.height;
        let width = self.width;
        self.pending_serialization = cx.background_executor().spawn(
            async move {
                KEY_VALUE_STORE
                    .write_kvp(
                        TERMINAL_PANEL_KEY.into(),
                        serde_json::to_string(&SerializedTerminalPanel {
                            items,
                            active_item_id,
                            height,
                            width,
                        })?,
                    )
                    .await?;
                anyhow::Ok(())
            }
            .log_err(),
        );
    }

    fn replace_terminal(
        &self,
        spawn_task: SpawnInTerminal,
        terminal_item_index: usize,
        terminal_to_replace: View<TerminalView>,
        cx: &mut ViewContext<'_, Self>,
    ) -> Option<()> {
        let project = self
            .workspace
            .update(cx, |workspace, _| workspace.project().clone())
            .ok()?;

        let reveal = spawn_task.reveal;
        let window = cx.window_handle();
        let new_terminal = project.update(cx, |project, cx| {
            project
                .create_terminal(spawn_task.cwd.clone(), Some(spawn_task), window, cx)
                .log_err()
        })?;
        terminal_to_replace.update(cx, |terminal_to_replace, cx| {
            terminal_to_replace.set_terminal(new_terminal, cx);
        });

        match reveal {
            RevealStrategy::Always => {
                self.activate_terminal_view(terminal_item_index, cx);
                let task_workspace = self.workspace.clone();
                cx.spawn(|_, mut cx| async move {
                    task_workspace
                        .update(&mut cx, |workspace, cx| workspace.focus_panel::<Self>(cx))
                        .ok()
                })
                .detach();
            }
            RevealStrategy::Never => {}
        }

        Some(())
    }

    pub fn pane(&self) -> &View<Pane> {
        &self.pane
    }

    fn has_no_terminals(&self, cx: &WindowContext) -> bool {
        self.pane.read(cx).items_len() == 0 && self.pending_terminals_to_add == 0
    }
}

async fn wait_for_terminals_tasks(
    terminals_for_task: Vec<(usize, View<TerminalView>)>,
    cx: &mut AsyncWindowContext,
) {
    let pending_tasks = terminals_for_task.iter().filter_map(|(_, terminal)| {
        terminal
            .update(cx, |terminal_view, cx| {
                terminal_view
                    .terminal()
                    .update(cx, |terminal, cx| terminal.wait_for_completed_task(cx))
            })
            .ok()
    });
    let _: Vec<()> = join_all(pending_tasks).await;
}

fn add_paths_to_terminal(pane: &mut Pane, paths: &[PathBuf], cx: &mut ViewContext<'_, Pane>) {
    if let Some(terminal_view) = pane
        .active_item()
        .and_then(|item| item.downcast::<TerminalView>())
    {
        cx.focus_view(&terminal_view);
        let mut new_text = paths.iter().map(|path| format!(" {path:?}")).join("");
        new_text.push(' ');
        terminal_view.update(cx, |terminal_view, cx| {
            terminal_view.terminal().update(cx, |terminal, _| {
                terminal.paste(&new_text);
            });
        });
    }
}

impl EventEmitter<PanelEvent> for TerminalPanel {}

impl Render for TerminalPanel {
    fn render(&mut self, cx: &mut ViewContext<Self>) -> impl IntoElement {
        let mut registrar = DivRegistrar::new(
            |panel, cx| {
                panel
                    .pane
                    .read(cx)
                    .toolbar()
                    .read(cx)
                    .item_of_type::<BufferSearchBar>()
            },
            cx,
        );
        BufferSearchBar::register(&mut registrar);
        registrar.into_div().size_full().child(self.pane.clone())
    }
}

impl FocusableView for TerminalPanel {
    fn focus_handle(&self, cx: &AppContext) -> FocusHandle {
        self.pane.focus_handle(cx)
    }
}

impl Panel for TerminalPanel {
    fn position(&self, cx: &WindowContext) -> DockPosition {
        match TerminalSettings::get_global(cx).dock {
            TerminalDockPosition::Left => DockPosition::Left,
            TerminalDockPosition::Bottom => DockPosition::Bottom,
            TerminalDockPosition::Right => DockPosition::Right,
        }
    }

    fn position_is_valid(&self, _: DockPosition) -> bool {
        true
    }

    fn set_position(&mut self, position: DockPosition, cx: &mut ViewContext<Self>) {
        settings::update_settings_file::<TerminalSettings>(
            self.fs.clone(),
            cx,
            move |settings, _| {
                let dock = match position {
                    DockPosition::Left => TerminalDockPosition::Left,
                    DockPosition::Bottom => TerminalDockPosition::Bottom,
                    DockPosition::Right => TerminalDockPosition::Right,
                };
                settings.dock = Some(dock);
            },
        );
    }

    fn size(&self, cx: &WindowContext) -> Pixels {
        let settings = TerminalSettings::get_global(cx);
        match self.position(cx) {
            DockPosition::Left | DockPosition::Right => {
                self.width.unwrap_or_else(|| settings.default_width)
            }
            DockPosition::Bottom => self.height.unwrap_or_else(|| settings.default_height),
        }
    }

    fn set_size(&mut self, size: Option<Pixels>, cx: &mut ViewContext<Self>) {
        match self.position(cx) {
            DockPosition::Left | DockPosition::Right => self.width = size,
            DockPosition::Bottom => self.height = size,
        }
        self.serialize(cx);
        cx.notify();
    }

    fn is_zoomed(&self, cx: &WindowContext) -> bool {
        self.pane.read(cx).is_zoomed()
    }

    fn set_zoomed(&mut self, zoomed: bool, cx: &mut ViewContext<Self>) {
        self.pane.update(cx, |pane, cx| pane.set_zoomed(zoomed, cx));
    }

    fn set_active(&mut self, active: bool, cx: &mut ViewContext<Self>) {
        if active && self.has_no_terminals(cx) {
            self.add_terminal(None, None, RevealStrategy::Never, cx)
                .detach_and_log_err(cx)
        }
    }

    fn icon_label(&self, cx: &WindowContext) -> Option<String> {
        let count = self.pane.read(cx).items_len();
        if count == 0 {
            None
        } else {
            Some(count.to_string())
        }
    }

    fn persistent_name() -> &'static str {
        "TerminalPanel"
    }

    fn icon(&self, cx: &WindowContext) -> Option<IconName> {
        if (self.enabled || !self.has_no_terminals(cx)) && TerminalSettings::get_global(cx).button {
            Some(IconName::Terminal)
        } else {
            None
        }
    }

    fn icon_tooltip(&self, _cx: &WindowContext) -> Option<&'static str> {
        Some("Terminal Panel")
    }

    fn toggle_action(&self) -> Box<dyn gpui::Action> {
        Box::new(ToggleFocus)
    }
}

#[derive(Serialize, Deserialize)]
struct SerializedTerminalPanel {
    items: Vec<u64>,
    active_item_id: Option<u64>,
    width: Option<Pixels>,
    height: Option<Pixels>,
}

fn retrieve_system_shell() -> Option<String> {
    #[cfg(not(target_os = "windows"))]
    {
        use anyhow::Context;
        use util::ResultExt;

        return std::env::var("SHELL")
            .context("Error finding SHELL in env.")
            .log_err();
    }
    // `alacritty_terminal` uses this as default on Windows. See:
    // https://github.com/alacritty/alacritty/blob/0d4ab7bca43213d96ddfe40048fc0f922543c6f8/alacritty_terminal/src/tty/windows/mod.rs#L130
    #[cfg(target_os = "windows")]
    return Some("powershell".to_owned());
}

#[cfg(target_os = "windows")]
fn to_windows_shell_variable(shell_type: WindowsShellType, input: String) -> String {
    match shell_type {
        WindowsShellType::Powershell => to_powershell_variable(input),
        WindowsShellType::Cmd => to_cmd_variable(input),
        WindowsShellType::Other => input,
    }
}

#[cfg(target_os = "windows")]
fn to_windows_shell_type(shell: &str) -> WindowsShellType {
    if shell == "powershell" || shell.ends_with("powershell.exe") {
        WindowsShellType::Powershell
    } else if shell == "cmd" || shell.ends_with("cmd.exe") {
        WindowsShellType::Cmd
    } else {
        // Someother shell detected, the user might install and use a
        // unix-like shell.
        WindowsShellType::Other
    }
}

/// Convert `${SOME_VAR}`, `$SOME_VAR` to `%SOME_VAR%`.
#[inline]
#[cfg(target_os = "windows")]
fn to_cmd_variable(input: String) -> String {
    if let Some(var_str) = input.strip_prefix("${") {
        if var_str.find(':').is_none() {
            // If the input starts with "${", remove the trailing "}"
            format!("%{}%", &var_str[..var_str.len() - 1])
        } else {
            // `${SOME_VAR:-SOME_DEFAULT}`, we currently do not handle this situation,
            // which will result in the task failing to run in such cases.
            input
        }
    } else if let Some(var_str) = input.strip_prefix('$') {
        // If the input starts with "$", directly append to "$env:"
        format!("%{}%", var_str)
    } else {
        // If no prefix is found, return the input as is
        input
    }
}

/// Convert `${SOME_VAR}`, `$SOME_VAR` to `$env:SOME_VAR`.
#[inline]
#[cfg(target_os = "windows")]
fn to_powershell_variable(input: String) -> String {
    if let Some(var_str) = input.strip_prefix("${") {
        if var_str.find(':').is_none() {
            // If the input starts with "${", remove the trailing "}"
            format!("$env:{}", &var_str[..var_str.len() - 1])
        } else {
            // `${SOME_VAR:-SOME_DEFAULT}`, we currently do not handle this situation,
            // which will result in the task failing to run in such cases.
            input
        }
    } else if let Some(var_str) = input.strip_prefix('$') {
        // If the input starts with "$", directly append to "$env:"
        format!("$env:{}", var_str)
    } else {
        // If no prefix is found, return the input as is
        input
    }
}

#[cfg(target_os = "windows")]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum WindowsShellType {
    Powershell,
    Cmd,
    Other,
}