use crate::{
    display_map::ToDisplayPoint, link_go_to_definition::hide_link_definition,
    movement::surrounding_word, Anchor, Autoscroll, Editor, Event, ExcerptId, MultiBuffer,
    MultiBufferSnapshot, NavigationData, ToPoint as _, FORMAT_TIMEOUT,
};
use anyhow::{anyhow, Context, Result};
use futures::FutureExt;
use gpui::{
    elements::*, geometry::vector::vec2f, AppContext, Entity, ModelHandle, MutableAppContext,
    RenderContext, Subscription, Task, View, ViewContext, ViewHandle, WeakViewHandle,
};
use language::{Bias, Buffer, File as _, OffsetRangeExt, Point, SelectionGoal};
use project::{File, FormatTrigger, Project, ProjectEntryId, ProjectPath};
use rpc::proto::{self, update_view};
use settings::Settings;
use smallvec::SmallVec;
use std::{
    borrow::Cow,
    cmp::{self, Ordering},
    fmt::Write,
    ops::Range,
    path::{Path, PathBuf},
};
use text::Selection;
use util::TryFutureExt;
use workspace::{
    item::{FollowableItem, Item, ItemEvent, ItemHandle, ProjectItem},
    searchable::{Direction, SearchEvent, SearchableItem, SearchableItemHandle},
    ItemId, ItemNavHistory, Pane, StatusItemView, ToolbarItemLocation, Workspace, WorkspaceId,
};

pub const MAX_TAB_TITLE_LEN: usize = 24;

impl FollowableItem for Editor {
    fn from_state_proto(
        pane: ViewHandle<workspace::Pane>,
        project: ModelHandle<Project>,
        state: &mut Option<proto::view::Variant>,
        cx: &mut MutableAppContext,
    ) -> Option<Task<Result<ViewHandle<Self>>>> {
        let state = if matches!(state, Some(proto::view::Variant::Editor(_))) {
            if let Some(proto::view::Variant::Editor(state)) = state.take() {
                state
            } else {
                unreachable!()
            }
        } else {
            return None;
        };

        let buffer = project.update(cx, |project, cx| {
            project.open_buffer_by_id(state.buffer_id, cx)
        });
        Some(cx.spawn(|mut cx| async move {
            let buffer = buffer.await?;
            let editor = pane
                .read_with(&cx, |pane, cx| {
                    pane.items_of_type::<Self>().find(|editor| {
                        editor.read(cx).buffer.read(cx).as_singleton().as_ref() == Some(&buffer)
                    })
                })
                .unwrap_or_else(|| {
                    pane.update(&mut cx, |_, cx| {
                        cx.add_view(|cx| Editor::for_buffer(buffer, Some(project), cx))
                    })
                });
            editor.update(&mut cx, |editor, cx| {
                let excerpt_id;
                let buffer_id;
                {
                    let buffer = editor.buffer.read(cx).read(cx);
                    let singleton = buffer.as_singleton().unwrap();
                    excerpt_id = singleton.0.clone();
                    buffer_id = singleton.1;
                }
                let selections = state
                    .selections
                    .into_iter()
                    .map(|selection| {
                        deserialize_selection(&excerpt_id, buffer_id, selection)
                            .ok_or_else(|| anyhow!("invalid selection"))
                    })
                    .collect::<Result<Vec<_>>>()?;
                if !selections.is_empty() {
                    editor.set_selections_from_remote(selections, cx);
                }

                if let Some(anchor) = state.scroll_top_anchor {
                    editor.set_scroll_top_anchor(
                        Anchor {
                            buffer_id: Some(state.buffer_id as usize),
                            excerpt_id,
                            text_anchor: language::proto::deserialize_anchor(anchor)
                                .ok_or_else(|| anyhow!("invalid scroll top"))?,
                        },
                        vec2f(state.scroll_x, state.scroll_y),
                        cx,
                    );
                }

                Ok::<_, anyhow::Error>(())
            })?;
            Ok(editor)
        }))
    }

    fn set_leader_replica_id(
        &mut self,
        leader_replica_id: Option<u16>,
        cx: &mut ViewContext<Self>,
    ) {
        self.leader_replica_id = leader_replica_id;
        if self.leader_replica_id.is_some() {
            self.buffer.update(cx, |buffer, cx| {
                buffer.remove_active_selections(cx);
            });
        } else {
            self.buffer.update(cx, |buffer, cx| {
                if self.focused {
                    buffer.set_active_selections(
                        &self.selections.disjoint_anchors(),
                        self.selections.line_mode,
                        self.cursor_shape,
                        cx,
                    );
                }
            });
        }
        cx.notify();
    }

    fn to_state_proto(&self, cx: &AppContext) -> Option<proto::view::Variant> {
        let buffer_id = self.buffer.read(cx).as_singleton()?.read(cx).remote_id();
        Some(proto::view::Variant::Editor(proto::view::Editor {
            buffer_id,
            scroll_top_anchor: Some(language::proto::serialize_anchor(
                &self.scroll_top_anchor.text_anchor,
            )),
            scroll_x: self.scroll_position.x(),
            scroll_y: self.scroll_position.y(),
            selections: self
                .selections
                .disjoint_anchors()
                .iter()
                .map(serialize_selection)
                .collect(),
        }))
    }

    fn add_event_to_update_proto(
        &self,
        event: &Self::Event,
        update: &mut Option<proto::update_view::Variant>,
        _: &AppContext,
    ) -> bool {
        let update =
            update.get_or_insert_with(|| proto::update_view::Variant::Editor(Default::default()));

        match update {
            proto::update_view::Variant::Editor(update) => match event {
                Event::ScrollPositionChanged { .. } => {
                    update.scroll_top_anchor = Some(language::proto::serialize_anchor(
                        &self.scroll_top_anchor.text_anchor,
                    ));
                    update.scroll_x = self.scroll_position.x();
                    update.scroll_y = self.scroll_position.y();
                    true
                }
                Event::SelectionsChanged { .. } => {
                    update.selections = self
                        .selections
                        .disjoint_anchors()
                        .iter()
                        .chain(self.selections.pending_anchor().as_ref())
                        .map(serialize_selection)
                        .collect();
                    true
                }
                _ => false,
            },
        }
    }

    fn apply_update_proto(
        &mut self,
        message: update_view::Variant,
        cx: &mut ViewContext<Self>,
    ) -> Result<()> {
        match message {
            update_view::Variant::Editor(message) => {
                let buffer = self.buffer.read(cx);
                let buffer = buffer.read(cx);
                let (excerpt_id, buffer_id, _) = buffer.as_singleton().unwrap();
                let excerpt_id = excerpt_id.clone();
                drop(buffer);

                let selections = message
                    .selections
                    .into_iter()
                    .filter_map(|selection| {
                        deserialize_selection(&excerpt_id, buffer_id, selection)
                    })
                    .collect::<Vec<_>>();

                if !selections.is_empty() {
                    self.set_selections_from_remote(selections, cx);
                    self.request_autoscroll_remotely(Autoscroll::newest(), cx);
                } else if let Some(anchor) = message.scroll_top_anchor {
                    self.set_scroll_top_anchor(
                        Anchor {
                            buffer_id: Some(buffer_id),
                            excerpt_id,
                            text_anchor: language::proto::deserialize_anchor(anchor)
                                .ok_or_else(|| anyhow!("invalid scroll top"))?,
                        },
                        vec2f(message.scroll_x, message.scroll_y),
                        cx,
                    );
                }
            }
        }
        Ok(())
    }

    fn should_unfollow_on_event(event: &Self::Event, _: &AppContext) -> bool {
        match event {
            Event::Edited => true,
            Event::SelectionsChanged { local } => *local,
            Event::ScrollPositionChanged { local } => *local,
            _ => false,
        }
    }
}

fn serialize_selection(selection: &Selection<Anchor>) -> proto::Selection {
    proto::Selection {
        id: selection.id as u64,
        start: Some(language::proto::serialize_anchor(
            &selection.start.text_anchor,
        )),
        end: Some(language::proto::serialize_anchor(
            &selection.end.text_anchor,
        )),
        reversed: selection.reversed,
    }
}

fn deserialize_selection(
    excerpt_id: &ExcerptId,
    buffer_id: usize,
    selection: proto::Selection,
) -> Option<Selection<Anchor>> {
    Some(Selection {
        id: selection.id as usize,
        start: Anchor {
            buffer_id: Some(buffer_id),
            excerpt_id: excerpt_id.clone(),
            text_anchor: language::proto::deserialize_anchor(selection.start?)?,
        },
        end: Anchor {
            buffer_id: Some(buffer_id),
            excerpt_id: excerpt_id.clone(),
            text_anchor: language::proto::deserialize_anchor(selection.end?)?,
        },
        reversed: selection.reversed,
        goal: SelectionGoal::None,
    })
}

impl Item for Editor {
    fn navigate(&mut self, data: Box<dyn std::any::Any>, cx: &mut ViewContext<Self>) -> bool {
        if let Ok(data) = data.downcast::<NavigationData>() {
            let newest_selection = self.selections.newest::<Point>(cx);
            let buffer = self.buffer.read(cx).read(cx);
            let offset = if buffer.can_resolve(&data.cursor_anchor) {
                data.cursor_anchor.to_point(&buffer)
            } else {
                buffer.clip_point(data.cursor_position, Bias::Left)
            };

            let scroll_top_anchor = if buffer.can_resolve(&data.scroll_top_anchor) {
                data.scroll_top_anchor
            } else {
                buffer.anchor_before(
                    buffer.clip_point(Point::new(data.scroll_top_row, 0), Bias::Left),
                )
            };

            drop(buffer);

            if newest_selection.head() == offset {
                false
            } else {
                let nav_history = self.nav_history.take();
                self.scroll_position = data.scroll_position;
                self.scroll_top_anchor = scroll_top_anchor;
                self.change_selections(Some(Autoscroll::fit()), cx, |s| {
                    s.select_ranges([offset..offset])
                });
                self.nav_history = nav_history;
                true
            }
        } else {
            false
        }
    }

    fn tab_description<'a>(&'a self, detail: usize, cx: &'a AppContext) -> Option<Cow<'a, str>> {
        match path_for_buffer(&self.buffer, detail, true, cx)? {
            Cow::Borrowed(path) => Some(path.to_string_lossy()),
            Cow::Owned(path) => Some(path.to_string_lossy().to_string().into()),
        }
    }

    fn tab_content(
        &self,
        detail: Option<usize>,
        style: &theme::Tab,
        cx: &AppContext,
    ) -> ElementBox {
        Flex::row()
            .with_child(
                Label::new(self.title(cx).into(), style.label.clone())
                    .aligned()
                    .boxed(),
            )
            .with_children(detail.and_then(|detail| {
                let path = path_for_buffer(&self.buffer, detail, false, cx)?;
                let description = path.to_string_lossy();
                Some(
                    Label::new(
                        if description.len() > MAX_TAB_TITLE_LEN {
                            description[..MAX_TAB_TITLE_LEN].to_string() + "…"
                        } else {
                            description.into()
                        },
                        style.description.text.clone(),
                    )
                    .contained()
                    .with_style(style.description.container)
                    .aligned()
                    .boxed(),
                )
            }))
            .boxed()
    }

    fn project_path(&self, cx: &AppContext) -> Option<ProjectPath> {
        let buffer = self.buffer.read(cx).as_singleton()?;
        let file = buffer.read(cx).file();
        File::from_dyn(file).map(|file| ProjectPath {
            worktree_id: file.worktree_id(cx),
            path: file.path().clone(),
        })
    }

    fn project_entry_ids(&self, cx: &AppContext) -> SmallVec<[ProjectEntryId; 3]> {
        self.buffer
            .read(cx)
            .files(cx)
            .into_iter()
            .filter_map(|file| File::from_dyn(Some(file))?.project_entry_id(cx))
            .collect()
    }

    fn is_singleton(&self, cx: &AppContext) -> bool {
        self.buffer.read(cx).is_singleton()
    }

    fn clone_on_split(&self, cx: &mut ViewContext<Self>) -> Option<Self>
    where
        Self: Sized,
    {
        Some(self.clone(cx))
    }

    fn set_nav_history(&mut self, history: ItemNavHistory, _: &mut ViewContext<Self>) {
        self.nav_history = Some(history);
    }

    fn deactivated(&mut self, cx: &mut ViewContext<Self>) {
        let selection = self.selections.newest_anchor();
        self.push_to_nav_history(selection.head(), None, cx);
    }

    fn workspace_deactivated(&mut self, cx: &mut ViewContext<Self>) {
        hide_link_definition(self, cx);
        self.link_go_to_definition_state.last_mouse_location = None;
    }

    fn is_dirty(&self, cx: &AppContext) -> bool {
        self.buffer().read(cx).read(cx).is_dirty()
    }

    fn has_conflict(&self, cx: &AppContext) -> bool {
        self.buffer().read(cx).read(cx).has_conflict()
    }

    fn can_save(&self, cx: &AppContext) -> bool {
        !self.buffer().read(cx).is_singleton() || self.project_path(cx).is_some()
    }

    fn save(
        &mut self,
        project: ModelHandle<Project>,
        cx: &mut ViewContext<Self>,
    ) -> Task<Result<()>> {
        self.report_event("save editor", cx);

        let buffer = self.buffer().clone();
        let buffers = buffer.read(cx).all_buffers();
        let mut timeout = cx.background().timer(FORMAT_TIMEOUT).fuse();
        let format = project.update(cx, |project, cx| {
            project.format(buffers, true, FormatTrigger::Save, cx)
        });
        cx.spawn(|_, mut cx| async move {
            let transaction = futures::select_biased! {
                _ = timeout => {
                    log::warn!("timed out waiting for formatting");
                    None
                }
                transaction = format.log_err().fuse() => transaction,
            };

            buffer
                .update(&mut cx, |buffer, cx| {
                    if let Some(transaction) = transaction {
                        if !buffer.is_singleton() {
                            buffer.push_transaction(&transaction.0);
                        }
                    }

                    buffer.save(cx)
                })
                .await?;
            Ok(())
        })
    }

    fn save_as(
        &mut self,
        project: ModelHandle<Project>,
        abs_path: PathBuf,
        cx: &mut ViewContext<Self>,
    ) -> Task<Result<()>> {
        let buffer = self
            .buffer()
            .read(cx)
            .as_singleton()
            .expect("cannot call save_as on an excerpt list");

        project.update(cx, |project, cx| {
            project.save_buffer_as(buffer, abs_path, cx)
        })
    }

    fn reload(
        &mut self,
        project: ModelHandle<Project>,
        cx: &mut ViewContext<Self>,
    ) -> Task<Result<()>> {
        let buffer = self.buffer().clone();
        let buffers = self.buffer.read(cx).all_buffers();
        let reload_buffers =
            project.update(cx, |project, cx| project.reload_buffers(buffers, true, cx));
        cx.spawn(|this, mut cx| async move {
            let transaction = reload_buffers.log_err().await;
            this.update(&mut cx, |editor, cx| {
                editor.request_autoscroll(Autoscroll::fit(), cx)
            });
            buffer.update(&mut cx, |buffer, _| {
                if let Some(transaction) = transaction {
                    if !buffer.is_singleton() {
                        buffer.push_transaction(&transaction.0);
                    }
                }
            });
            Ok(())
        })
    }

    fn git_diff_recalc(
        &mut self,
        _project: ModelHandle<Project>,
        cx: &mut ViewContext<Self>,
    ) -> Task<Result<()>> {
        self.buffer().update(cx, |multibuffer, cx| {
            multibuffer.git_diff_recalc(cx);
        });
        Task::ready(Ok(()))
    }

    fn to_item_events(event: &Self::Event) -> Vec<ItemEvent> {
        let mut result = Vec::new();
        match event {
            Event::Closed => result.push(ItemEvent::CloseItem),
            Event::Saved | Event::TitleChanged => {
                result.push(ItemEvent::UpdateTab);
                result.push(ItemEvent::UpdateBreadcrumbs);
            }
            Event::Reparsed => {
                result.push(ItemEvent::UpdateBreadcrumbs);
            }
            Event::SelectionsChanged { local } if *local => {
                result.push(ItemEvent::UpdateBreadcrumbs);
            }
            Event::DirtyChanged => {
                result.push(ItemEvent::UpdateTab);
            }
            Event::BufferEdited => {
                result.push(ItemEvent::Edit);
                result.push(ItemEvent::UpdateBreadcrumbs);
            }
            _ => {}
        }
        result
    }

    fn as_searchable(&self, handle: &ViewHandle<Self>) -> Option<Box<dyn SearchableItemHandle>> {
        Some(Box::new(handle.clone()))
    }

    fn breadcrumb_location(&self) -> ToolbarItemLocation {
        ToolbarItemLocation::PrimaryLeft { flex: None }
    }

    fn breadcrumbs(&self, theme: &theme::Theme, cx: &AppContext) -> Option<Vec<ElementBox>> {
        let cursor = self.selections.newest_anchor().head();
        let multibuffer = &self.buffer().read(cx);
        let (buffer_id, symbols) =
            multibuffer.symbols_containing(cursor, Some(&theme.editor.syntax), cx)?;
        let buffer = multibuffer.buffer(buffer_id)?;

        let buffer = buffer.read(cx);
        let filename = buffer
            .snapshot()
            .resolve_file_path(
                cx,
                self.project
                    .as_ref()
                    .map(|project| project.read(cx).visible_worktrees(cx).count() > 1)
                    .unwrap_or_default(),
            )
            .map(|path| path.to_string_lossy().to_string())
            .unwrap_or_else(|| "untitled".to_string());

        let mut breadcrumbs = vec![Label::new(filename, theme.breadcrumbs.text.clone()).boxed()];
        breadcrumbs.extend(symbols.into_iter().map(|symbol| {
            Text::new(symbol.text, theme.breadcrumbs.text.clone())
                .with_highlights(symbol.highlight_ranges)
                .boxed()
        }));
        Some(breadcrumbs)
    }

    fn serialized_item_kind() -> Option<&'static str> {
        // TODO: Some("Editor")
        None
    }

    fn deserialize(
        project: ModelHandle<Project>,
        _workspace: WeakViewHandle<Workspace>,
        _workspace_id: WorkspaceId,
        _item_id: ItemId,
        cx: &mut ViewContext<Pane>,
    ) -> Task<Result<ViewHandle<Self>>> {
        // Look up the path with this key associated, create a self with that path
        let path = Path::new(".");
        if let Some(project_item) = project.update(cx, |project, cx| {
            let (worktree, path) = project.find_local_worktree(path, cx)?;
            let project_path = ProjectPath {
                worktree_id: worktree.read(cx).id(),
                path: path.into(),
            };

            Some(project.open_path(project_path, cx))
        }) {
            cx.spawn(|pane, mut cx| async move {
                let (_, project_item) = project_item.await?;
                let buffer = project_item
                    .downcast::<Buffer>()
                    .context("Project item at stored path was not a buffer")?;

                Ok(cx.update(|cx| {
                    cx.add_view(pane, |cx| Editor::for_buffer(buffer, Some(project), cx))
                }))
            })
        } else {
            Task::ready(Err(anyhow!("Could not load file from stored path")))
        }
    }
}

impl ProjectItem for Editor {
    type Item = Buffer;

    fn for_project_item(
        project: ModelHandle<Project>,
        buffer: ModelHandle<Buffer>,
        cx: &mut ViewContext<Self>,
    ) -> Self {
        Self::for_buffer(buffer, Some(project), cx)
    }
}

enum BufferSearchHighlights {}
impl SearchableItem for Editor {
    type Match = Range<Anchor>;

    fn to_search_event(event: &Self::Event) -> Option<SearchEvent> {
        match event {
            Event::BufferEdited => Some(SearchEvent::MatchesInvalidated),
            Event::SelectionsChanged { .. } => Some(SearchEvent::ActiveMatchChanged),
            _ => None,
        }
    }

    fn clear_matches(&mut self, cx: &mut ViewContext<Self>) {
        self.clear_background_highlights::<BufferSearchHighlights>(cx);
    }

    fn update_matches(&mut self, matches: Vec<Range<Anchor>>, cx: &mut ViewContext<Self>) {
        self.highlight_background::<BufferSearchHighlights>(
            matches,
            |theme| theme.search.match_background,
            cx,
        );
    }

    fn query_suggestion(&mut self, cx: &mut ViewContext<Self>) -> String {
        let display_map = self.snapshot(cx).display_snapshot;
        let selection = self.selections.newest::<usize>(cx);
        if selection.start == selection.end {
            let point = selection.start.to_display_point(&display_map);
            let range = surrounding_word(&display_map, point);
            let range = range.start.to_offset(&display_map, Bias::Left)
                ..range.end.to_offset(&display_map, Bias::Right);
            let text: String = display_map.buffer_snapshot.text_for_range(range).collect();
            if text.trim().is_empty() {
                String::new()
            } else {
                text
            }
        } else {
            display_map
                .buffer_snapshot
                .text_for_range(selection.start..selection.end)
                .collect()
        }
    }

    fn activate_match(
        &mut self,
        index: usize,
        matches: Vec<Range<Anchor>>,
        cx: &mut ViewContext<Self>,
    ) {
        self.unfold_ranges([matches[index].clone()], false, cx);
        self.change_selections(Some(Autoscroll::fit()), cx, |s| {
            s.select_ranges([matches[index].clone()])
        });
    }

    fn match_index_for_direction(
        &mut self,
        matches: &Vec<Range<Anchor>>,
        mut current_index: usize,
        direction: Direction,
        cx: &mut ViewContext<Self>,
    ) -> usize {
        let buffer = self.buffer().read(cx).snapshot(cx);
        let cursor = self.selections.newest_anchor().head();
        if matches[current_index].start.cmp(&cursor, &buffer).is_gt() {
            if direction == Direction::Prev {
                if current_index == 0 {
                    current_index = matches.len() - 1;
                } else {
                    current_index -= 1;
                }
            }
        } else if matches[current_index].end.cmp(&cursor, &buffer).is_lt() {
            if direction == Direction::Next {
                current_index = 0;
            }
        } else if direction == Direction::Prev {
            if current_index == 0 {
                current_index = matches.len() - 1;
            } else {
                current_index -= 1;
            }
        } else if direction == Direction::Next {
            if current_index == matches.len() - 1 {
                current_index = 0
            } else {
                current_index += 1;
            }
        };
        current_index
    }

    fn find_matches(
        &mut self,
        query: project::search::SearchQuery,
        cx: &mut ViewContext<Self>,
    ) -> Task<Vec<Range<Anchor>>> {
        let buffer = self.buffer().read(cx).snapshot(cx);
        cx.background().spawn(async move {
            let mut ranges = Vec::new();
            if let Some((_, _, excerpt_buffer)) = buffer.as_singleton() {
                ranges.extend(
                    query
                        .search(excerpt_buffer.as_rope())
                        .await
                        .into_iter()
                        .map(|range| {
                            buffer.anchor_after(range.start)..buffer.anchor_before(range.end)
                        }),
                );
            } else {
                for excerpt in buffer.excerpt_boundaries_in_range(0..buffer.len()) {
                    let excerpt_range = excerpt.range.context.to_offset(&excerpt.buffer);
                    let rope = excerpt.buffer.as_rope().slice(excerpt_range.clone());
                    ranges.extend(query.search(&rope).await.into_iter().map(|range| {
                        let start = excerpt
                            .buffer
                            .anchor_after(excerpt_range.start + range.start);
                        let end = excerpt
                            .buffer
                            .anchor_before(excerpt_range.start + range.end);
                        buffer.anchor_in_excerpt(excerpt.id.clone(), start)
                            ..buffer.anchor_in_excerpt(excerpt.id.clone(), end)
                    }));
                }
            }
            ranges
        })
    }

    fn active_match_index(
        &mut self,
        matches: Vec<Range<Anchor>>,
        cx: &mut ViewContext<Self>,
    ) -> Option<usize> {
        active_match_index(
            &matches,
            &self.selections.newest_anchor().head(),
            &self.buffer().read(cx).snapshot(cx),
        )
    }
}

pub fn active_match_index(
    ranges: &[Range<Anchor>],
    cursor: &Anchor,
    buffer: &MultiBufferSnapshot,
) -> Option<usize> {
    if ranges.is_empty() {
        None
    } else {
        match ranges.binary_search_by(|probe| {
            if probe.end.cmp(cursor, &*buffer).is_lt() {
                Ordering::Less
            } else if probe.start.cmp(cursor, &*buffer).is_gt() {
                Ordering::Greater
            } else {
                Ordering::Equal
            }
        }) {
            Ok(i) | Err(i) => Some(cmp::min(i, ranges.len() - 1)),
        }
    }
}

pub struct CursorPosition {
    position: Option<Point>,
    selected_count: usize,
    _observe_active_editor: Option<Subscription>,
}

impl Default for CursorPosition {
    fn default() -> Self {
        Self::new()
    }
}

impl CursorPosition {
    pub fn new() -> Self {
        Self {
            position: None,
            selected_count: 0,
            _observe_active_editor: None,
        }
    }

    fn update_position(&mut self, editor: ViewHandle<Editor>, cx: &mut ViewContext<Self>) {
        let editor = editor.read(cx);
        let buffer = editor.buffer().read(cx).snapshot(cx);

        self.selected_count = 0;
        let mut last_selection: Option<Selection<usize>> = None;
        for selection in editor.selections.all::<usize>(cx) {
            self.selected_count += selection.end - selection.start;
            if last_selection
                .as_ref()
                .map_or(true, |last_selection| selection.id > last_selection.id)
            {
                last_selection = Some(selection);
            }
        }
        self.position = last_selection.map(|s| s.head().to_point(&buffer));

        cx.notify();
    }
}

impl Entity for CursorPosition {
    type Event = ();
}

impl View for CursorPosition {
    fn ui_name() -> &'static str {
        "CursorPosition"
    }

    fn render(&mut self, cx: &mut RenderContext<Self>) -> ElementBox {
        if let Some(position) = self.position {
            let theme = &cx.global::<Settings>().theme.workspace.status_bar;
            let mut text = format!("{},{}", position.row + 1, position.column + 1);
            if self.selected_count > 0 {
                write!(text, " ({} selected)", self.selected_count).unwrap();
            }
            Label::new(text, theme.cursor_position.clone()).boxed()
        } else {
            Empty::new().boxed()
        }
    }
}

impl StatusItemView for CursorPosition {
    fn set_active_pane_item(
        &mut self,
        active_pane_item: Option<&dyn ItemHandle>,
        cx: &mut ViewContext<Self>,
    ) {
        if let Some(editor) = active_pane_item.and_then(|item| item.downcast::<Editor>()) {
            self._observe_active_editor = Some(cx.observe(&editor, Self::update_position));
            self.update_position(editor, cx);
        } else {
            self.position = None;
            self._observe_active_editor = None;
        }

        cx.notify();
    }
}

fn path_for_buffer<'a>(
    buffer: &ModelHandle<MultiBuffer>,
    height: usize,
    include_filename: bool,
    cx: &'a AppContext,
) -> Option<Cow<'a, Path>> {
    let file = buffer.read(cx).as_singleton()?.read(cx).file()?;
    path_for_file(file, height, include_filename, cx)
}

fn path_for_file<'a>(
    file: &'a dyn language::File,
    mut height: usize,
    include_filename: bool,
    cx: &'a AppContext,
) -> Option<Cow<'a, Path>> {
    // Ensure we always render at least the filename.
    height += 1;

    let mut prefix = file.path().as_ref();
    while height > 0 {
        if let Some(parent) = prefix.parent() {
            prefix = parent;
            height -= 1;
        } else {
            break;
        }
    }

    // Here we could have just always used `full_path`, but that is very
    // allocation-heavy and so we try to use a `Cow<Path>` if we haven't
    // traversed all the way up to the worktree's root.
    if height > 0 {
        let full_path = file.full_path(cx);
        if include_filename {
            Some(full_path.into())
        } else {
            Some(full_path.parent()?.to_path_buf().into())
        }
    } else {
        let mut path = file.path().strip_prefix(prefix).ok()?;
        if !include_filename {
            path = path.parent()?;
        }
        Some(path.into())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use gpui::MutableAppContext;
    use std::{
        path::{Path, PathBuf},
        sync::Arc,
    };

    #[gpui::test]
    fn test_path_for_file(cx: &mut MutableAppContext) {
        let file = TestFile {
            path: Path::new("").into(),
            full_path: PathBuf::from(""),
        };
        assert_eq!(path_for_file(&file, 0, false, cx), None);
    }

    struct TestFile {
        path: Arc<Path>,
        full_path: PathBuf,
    }

    impl language::File for TestFile {
        fn path(&self) -> &Arc<Path> {
            &self.path
        }

        fn full_path(&self, _: &gpui::AppContext) -> PathBuf {
            self.full_path.clone()
        }

        fn as_local(&self) -> Option<&dyn language::LocalFile> {
            todo!()
        }

        fn mtime(&self) -> std::time::SystemTime {
            todo!()
        }

        fn file_name<'a>(&'a self, _: &'a gpui::AppContext) -> &'a std::ffi::OsStr {
            todo!()
        }

        fn is_deleted(&self) -> bool {
            todo!()
        }

        fn save(
            &self,
            _: u64,
            _: language::Rope,
            _: clock::Global,
            _: project::LineEnding,
            _: &mut MutableAppContext,
        ) -> gpui::Task<anyhow::Result<(clock::Global, String, std::time::SystemTime)>> {
            todo!()
        }

        fn as_any(&self) -> &dyn std::any::Any {
            todo!()
        }

        fn to_proto(&self) -> rpc::proto::File {
            todo!()
        }
    }
}