use std::{
    ops::Range,
    time::{Duration, Instant},
};

use gpui::{
    actions,
    elements::{Flex, MouseEventHandler, Padding, Text},
    impl_internal_actions,
    platform::CursorStyle,
    Axis, Element, ElementBox, ModelHandle, MutableAppContext, RenderContext, Task, ViewContext,
};
use language::Bias;
use project::{HoverBlock, Project};
use util::TryFutureExt;

use crate::{
    display_map::ToDisplayPoint, Anchor, AnchorRangeExt, DisplayPoint, Editor, EditorSnapshot,
    EditorStyle,
};

pub const HOVER_DELAY_MILLIS: u64 = 350;
pub const HOVER_REQUEST_DELAY_MILLIS: u64 = 200;

#[derive(Clone, PartialEq)]
pub struct HoverAt {
    pub point: Option<DisplayPoint>,
}

actions!(editor, [Hover]);
impl_internal_actions!(editor, [HoverAt]);

pub fn init(cx: &mut MutableAppContext) {
    cx.add_action(hover);
    cx.add_action(hover_at);
}

/// Bindable action which uses the most recent selection head to trigger a hover
pub fn hover(editor: &mut Editor, _: &Hover, cx: &mut ViewContext<Editor>) {
    let head = editor.selections.newest_display(cx).head();
    show_hover(editor, head, true, cx);
}

/// The internal hover action dispatches between `show_hover` or `hide_hover`
/// depending on whether a point to hover over is provided.
pub fn hover_at(editor: &mut Editor, action: &HoverAt, cx: &mut ViewContext<Editor>) {
    if let Some(point) = action.point {
        show_hover(editor, point, false, cx);
    } else {
        hide_hover(editor, cx);
    }
}

/// Hides the type information popup.
/// Triggered by the `Hover` action when the cursor is not over a symbol or when the
/// selections changed.
pub fn hide_hover(editor: &mut Editor, cx: &mut ViewContext<Editor>) -> bool {
    let mut did_hide = false;

    // only notify the context once
    if editor.hover_state.popover.is_some() {
        editor.hover_state.popover = None;
        editor.hover_state.hidden_at = Some(cx.background().now());
        did_hide = true;
        cx.notify();
    }
    editor.hover_state.task = None;
    editor.hover_state.triggered_from = None;
    editor.hover_state.symbol_range = None;

    editor.clear_background_highlights::<HoverState>(cx);

    did_hide
}

/// Queries the LSP and shows type info and documentation
/// about the symbol the mouse is currently hovering over.
/// Triggered by the `Hover` action when the cursor may be over a symbol.
fn show_hover(
    editor: &mut Editor,
    point: DisplayPoint,
    ignore_timeout: bool,
    cx: &mut ViewContext<Editor>,
) {
    if editor.pending_rename.is_some() {
        return;
    }

    let snapshot = editor.snapshot(cx);
    let multibuffer_offset = point.to_offset(&snapshot.display_snapshot, Bias::Left);

    let (buffer, buffer_position) = if let Some(output) = editor
        .buffer
        .read(cx)
        .text_anchor_for_position(multibuffer_offset, cx)
    {
        output
    } else {
        return;
    };

    let excerpt_id = if let Some((excerpt_id, _, _)) = editor
        .buffer()
        .read(cx)
        .excerpt_containing(multibuffer_offset, cx)
    {
        excerpt_id
    } else {
        return;
    };

    let project = if let Some(project) = editor.project.clone() {
        project
    } else {
        return;
    };

    if !ignore_timeout {
        if let Some(range) = &editor.hover_state.symbol_range {
            if range
                .to_offset(&snapshot.buffer_snapshot)
                .contains(&multibuffer_offset)
            {
                // Hover triggered from same location as last time. Don't show again.
                return;
            } else {
                hide_hover(editor, cx);
            }
        }
    }

    // Get input anchor
    let anchor = snapshot
        .buffer_snapshot
        .anchor_at(multibuffer_offset, Bias::Left);

    // Don't request again if the location is the same as the previous request
    if let Some(triggered_from) = &editor.hover_state.triggered_from {
        if triggered_from
            .cmp(&anchor, &snapshot.buffer_snapshot)
            .is_eq()
        {
            return;
        }
    }

    let task = cx.spawn_weak(|this, mut cx| {
        async move {
            // If we need to delay, delay a set amount initially before making the lsp request
            let delay = if !ignore_timeout {
                // Construct delay task to wait for later
                let total_delay = Some(
                    cx.background()
                        .timer(Duration::from_millis(HOVER_DELAY_MILLIS)),
                );

                cx.background()
                    .timer(Duration::from_millis(HOVER_REQUEST_DELAY_MILLIS))
                    .await;
                total_delay
            } else {
                None
            };

            // query the LSP for hover info
            let hover_request = cx.update(|cx| {
                project.update(cx, |project, cx| {
                    project.hover(&buffer, buffer_position.clone(), cx)
                })
            });

            // Construct new hover popover from hover request
            let hover_popover = hover_request.await.ok().flatten().and_then(|hover_result| {
                if hover_result.contents.is_empty() {
                    return None;
                }

                // Create symbol range of anchors for highlighting and filtering
                // of future requests.
                let range = if let Some(range) = hover_result.range {
                    let start = snapshot
                        .buffer_snapshot
                        .anchor_in_excerpt(excerpt_id.clone(), range.start);
                    let end = snapshot
                        .buffer_snapshot
                        .anchor_in_excerpt(excerpt_id.clone(), range.end);

                    start..end
                } else {
                    anchor.clone()..anchor.clone()
                };

                if let Some(this) = this.upgrade(&cx) {
                    this.update(&mut cx, |this, _| {
                        this.hover_state.symbol_range = Some(range.clone());
                    });
                }

                Some(HoverPopover {
                    project: project.clone(),
                    anchor: range.start.clone(),
                    contents: hover_result.contents,
                })
            });

            if let Some(delay) = delay {
                delay.await;
            }

            if let Some(this) = this.upgrade(&cx) {
                this.update(&mut cx, |this, cx| {
                    if hover_popover.is_some() {
                        // Highlight the selected symbol using a background highlight
                        if let Some(range) = this.hover_state.symbol_range.clone() {
                            this.highlight_background::<HoverState>(
                                vec![range],
                                |theme| theme.editor.hover_popover.highlight,
                                cx,
                            );
                        }
                        this.hover_state.popover = hover_popover;
                        cx.notify();
                    } else {
                        if this.hover_state.visible() {
                            // Popover was visible, but now is hidden. Dismiss it
                            hide_hover(this, cx);
                        } else {
                            // Clear selected symbol range for future requests
                            this.hover_state.symbol_range = None;
                        }
                    }
                });
            }
            Ok::<_, anyhow::Error>(())
        }
        .log_err()
    });

    editor.hover_state.task = Some(task);
}

#[derive(Default)]
pub struct HoverState {
    pub popover: Option<HoverPopover>,
    pub hidden_at: Option<Instant>,
    pub triggered_from: Option<Anchor>,
    pub symbol_range: Option<Range<Anchor>>,
    pub task: Option<Task<Option<()>>>,
}

impl HoverState {
    pub fn visible(&self) -> bool {
        self.popover.is_some()
    }
}

#[derive(Debug, Clone)]
pub struct HoverPopover {
    pub project: ModelHandle<Project>,
    pub anchor: Anchor,
    pub contents: Vec<HoverBlock>,
}

impl HoverPopover {
    pub fn render(
        &self,
        snapshot: &EditorSnapshot,
        style: EditorStyle,
        cx: &mut RenderContext<Editor>,
    ) -> (DisplayPoint, ElementBox) {
        let element = MouseEventHandler::new::<HoverPopover, _, _>(0, cx, |_, cx| {
            let mut flex = Flex::new(Axis::Vertical).scrollable::<HoverBlock, _>(1, None, cx);
            flex.extend(self.contents.iter().map(|content| {
                let project = self.project.read(cx);
                if let Some(language) = content
                    .language
                    .clone()
                    .and_then(|language| project.languages().get_language(&language))
                {
                    let runs = language
                        .highlight_text(&content.text.as_str().into(), 0..content.text.len());

                    Text::new(content.text.clone(), style.text.clone())
                        .with_soft_wrap(true)
                        .with_highlights(
                            runs.iter()
                                .filter_map(|(range, id)| {
                                    id.style(style.theme.syntax.as_ref())
                                        .map(|style| (range.clone(), style))
                                })
                                .collect(),
                        )
                        .boxed()
                } else {
                    let mut text_style = style.hover_popover.prose.clone();
                    text_style.font_size = style.text.font_size;

                    Text::new(content.text.clone(), text_style)
                        .with_soft_wrap(true)
                        .contained()
                        .with_style(style.hover_popover.block_style)
                        .boxed()
                }
            }));
            flex.contained()
                .with_style(style.hover_popover.container)
                .boxed()
        })
        .with_cursor_style(CursorStyle::Arrow)
        .with_padding(Padding {
            bottom: 5.,
            top: 5.,
            ..Default::default()
        })
        .boxed();

        let display_point = self.anchor.to_display_point(&snapshot.display_snapshot);
        (display_point, element)
    }
}

#[cfg(test)]
mod tests {
    use futures::StreamExt;
    use indoc::indoc;

    use project::HoverBlock;

    use crate::test::EditorLspTestContext;

    use super::*;

    #[gpui::test]
    async fn test_hover_popover(cx: &mut gpui::TestAppContext) {
        let mut cx = EditorLspTestContext::new_rust(
            lsp::ServerCapabilities {
                hover_provider: Some(lsp::HoverProviderCapability::Simple(true)),
                ..Default::default()
            },
            cx,
        )
        .await;

        // Basic hover delays and then pops without moving the mouse
        cx.set_state(indoc! {"
            fn |test()
                println!();"});
        let hover_point = cx.display_point(indoc! {"
            fn test()
                print|ln!();"});

        cx.update_editor(|editor, cx| {
            hover_at(
                editor,
                &HoverAt {
                    point: Some(hover_point),
                },
                cx,
            )
        });
        assert!(!cx.editor(|editor, _| editor.hover_state.visible()));

        // After delay, hover should be visible.
        let symbol_range = cx.lsp_range(indoc! {"
            fn test()
                [println!]();"});
        let mut requests =
            cx.lsp
                .handle_request::<lsp::request::HoverRequest, _, _>(move |_, _| async move {
                    Ok(Some(lsp::Hover {
                        contents: lsp::HoverContents::Markup(lsp::MarkupContent {
                            kind: lsp::MarkupKind::Markdown,
                            value: indoc! {"
                                # Some basic docs
                                Some test documentation"}
                            .to_string(),
                        }),
                        range: Some(symbol_range),
                    }))
                });
        cx.foreground()
            .advance_clock(Duration::from_millis(HOVER_DELAY_MILLIS + 100));
        requests.next().await;

        cx.editor(|editor, _| {
            assert!(editor.hover_state.visible());
            assert_eq!(
                editor.hover_state.popover.clone().unwrap().contents,
                vec![
                    HoverBlock {
                        text: "Some basic docs".to_string(),
                        language: None
                    },
                    HoverBlock {
                        text: "Some test documentation".to_string(),
                        language: None
                    }
                ]
            )
        });

        // Mouse moved with no hover response dismisses
        let hover_point = cx.display_point(indoc! {"
            fn te|st()
                println!();"});
        cx.update_editor(|editor, cx| {
            hover_at(
                editor,
                &HoverAt {
                    point: Some(hover_point),
                },
                cx,
            )
        });
        let mut request = cx
            .lsp
            .handle_request::<lsp::request::HoverRequest, _, _>(|_, _| async move { Ok(None) });
        cx.foreground()
            .advance_clock(Duration::from_millis(HOVER_DELAY_MILLIS + 100));
        request.next().await;
        cx.editor(|editor, _| {
            assert!(!editor.hover_state.visible());
        });

        // Hover with keyboard has no delay
        cx.set_state(indoc! {"
            f|n test()
                println!();"});
        cx.update_editor(|editor, cx| hover(editor, &Hover, cx));
        let symbol_range = cx.lsp_range(indoc! {"
            [fn] test()
                println!();"});
        cx.lsp
            .handle_request::<lsp::request::HoverRequest, _, _>(move |_, _| async move {
                Ok(Some(lsp::Hover {
                    contents: lsp::HoverContents::Markup(lsp::MarkupContent {
                        kind: lsp::MarkupKind::Markdown,
                        value: indoc! {"
                            # Some other basic docs
                            Some other test documentation"}
                        .to_string(),
                    }),
                    range: Some(symbol_range),
                }))
            })
            .next()
            .await;
        cx.foreground().run_until_parked();
        cx.editor(|editor, _| {
            assert!(editor.hover_state.visible());
            assert_eq!(
                editor.hover_state.popover.clone().unwrap().contents,
                vec![
                    HoverBlock {
                        text: "Some other basic docs".to_string(),
                        language: None
                    },
                    HoverBlock {
                        text: "Some other test documentation".to_string(),
                        language: None
                    }
                ]
            )
        });
    }
}