//! Permanent passive decoration around the existing editor. Draw uses current
//! geometry; only the source index is cached, never pointer hitboxes or messages.
//! Current-frame tooltip paragraphs stay owned until deferred renderer preparation.
use super::Index;
use iced::advanced::text::Paragraph as _;
use iced::{
    Element, Event, Font, Length, Padding, Point, Rectangle, Size, Theme, Vector,
    advanced::{
        Clipboard, Layout, Shell, Widget, graphics, layout, overlay, renderer, text, widget,
    },
    alignment, mouse,
    widget::text_editor,
};
use oa_core::{Id, source_project::SourceDiagnostic, validation::Severity};
use std::{cell::RefCell, sync::Arc};

pub(crate) struct Decorations<'a, Message, R: text::Renderer> {
    child: Element<'a, Message, Theme, R>,
    content: &'a text_editor::Content<R>,
    snapshot: Option<Snapshot<'a>>,
    padding: Padding,
    hover_enabled: bool,
}

/// Supplied only after the App admits a current diagnostic publication for the
/// displayed draft. Absence keeps the editor mounted with no annotations.
pub(crate) struct Snapshot<'a> {
    pub publication: Id,
    pub source: Arc<str>,
    pub path: &'a str,
    pub diagnostics: &'a [SourceDiagnostic],
}

impl<'a, Message, R: text::Renderer> Decorations<'a, Message, R> {
    pub fn new(
        child: impl Into<Element<'a, Message, Theme, R>>,
        content: &'a text_editor::Content<R>,
        snapshot: Option<Snapshot<'a>>,
        padding: Padding,
        hover_enabled: bool,
    ) -> Self {
        Self {
            child: child.into(),
            content,
            snapshot,
            padding,
            hover_enabled,
        }
    }
}

struct Cached {
    publication: Id,
    path: String,
    source: Arc<str>,
    index: Index,
}
#[derive(Default)]
struct State {
    index: RefCell<Option<Cached>>,
    details: RefCell<Option<DetailsParagraphs>>,
}

// WGPU queues weak paragraph references during draw and upgrades them later.
// This is render-resource ownership, not a cache authorizing future hover hits.
struct DetailsParagraphs {
    _body: graphics::text::Paragraph,
    _footer: graphics::text::Paragraph,
}

impl<Message, R> Widget<Message, Theme, R> for Decorations<'_, Message, R>
where
    R: text::Renderer<
            Font = Font,
            Editor = graphics::text::Editor,
            Paragraph = graphics::text::Paragraph,
        >,
{
    fn tag(&self) -> widget::tree::Tag {
        widget::tree::Tag::of::<State>()
    }
    fn state(&self) -> widget::tree::State {
        widget::tree::State::new(State::default())
    }
    fn children(&self) -> Vec<widget::Tree> {
        vec![widget::Tree::new(&self.child)]
    }
    fn diff(&self, tree: &mut widget::Tree) {
        // A publication change only replaces the read-only index. The editor's
        // existing Tree and hidden selection/IME/scroll state remain mounted.
        tree.diff_children(std::slice::from_ref(&self.child));
    }
    fn size(&self) -> Size<Length> {
        self.child.as_widget().size()
    }
    fn size_hint(&self) -> Size<Length> {
        self.child.as_widget().size_hint()
    }
    fn layout(
        &mut self,
        tree: &mut widget::Tree,
        renderer: &R,
        limits: &layout::Limits,
    ) -> layout::Node {
        self.child
            .as_widget_mut()
            .layout(&mut tree.children[0], renderer, limits)
    }
    fn operate(
        &mut self,
        tree: &mut widget::Tree,
        layout: Layout<'_>,
        renderer: &R,
        operation: &mut dyn widget::Operation,
    ) {
        self.child
            .as_widget_mut()
            .operate(&mut tree.children[0], layout, renderer, operation);
    }
    fn update(
        &mut self,
        tree: &mut widget::Tree,
        event: &Event,
        layout: Layout<'_>,
        cursor: mouse::Cursor,
        renderer: &R,
        clipboard: &mut dyn Clipboard,
        shell: &mut Shell<'_, Message>,
        viewport: &Rectangle,
    ) {
        if matches!(
            event,
            Event::Mouse(mouse::Event::CursorMoved { .. } | mouse::Event::CursorLeft)
        ) {
            // Movement within a focused editor need not change stock status.
            // Request painting, but do not capture or publish any input action.
            shell.request_redraw();
        }
        self.child.as_widget_mut().update(
            &mut tree.children[0],
            event,
            layout,
            cursor,
            renderer,
            clipboard,
            shell,
            viewport,
        );
    }
    fn draw(
        &self,
        tree: &widget::Tree,
        renderer: &mut R,
        theme: &Theme,
        style: &renderer::Style,
        layout: Layout<'_>,
        cursor: mouse::Cursor,
        viewport: &Rectangle,
    ) {
        self.child.as_widget().draw(
            &tree.children[0],
            renderer,
            theme,
            style,
            layout,
            cursor,
            viewport,
        );
        let state = tree.state.downcast_ref::<State>();
        // Revoke the preceding frame's text even on every early/hidden path.
        // Current source admission and current geometry alone decide new text.
        let mut details = state.details.borrow_mut();
        *details = None;
        let mut cache = state.index.borrow_mut();
        let Some(snapshot) = &self.snapshot else {
            *cache = None;
            return;
        };
        let inner = layout.bounds().shrink(self.padding);
        let Some(clip) = inner
            .intersection(viewport)
            .filter(|clip| clip.width > 0. && clip.height > 0.)
        else {
            return;
        };
        if cache.as_ref().is_none_or(|cached| {
            cached.publication != snapshot.publication
                || cached.path != snapshot.path
                || !Arc::ptr_eq(&cached.source, &snapshot.source)
        }) {
            *cache = Some(Cached {
                publication: snapshot.publication,
                path: snapshot.path.into(),
                source: snapshot.source.clone(),
                index: Index::new(snapshot.source.clone(), snapshot.path, snapshot.diagnostics),
            });
        }
        // Child draw has now applied the actual syntax highlighter. Release the
        // Content borrow before further renderer work; no callback reentrancy.
        let mut bands = self.content.with_editor(|editor| {
            cache
                .as_ref()
                .unwrap()
                .index
                .bands(editor.buffer(), inner.position(), clip)
        });
        bands.sort_by_key(
            |band| match snapshot.diagnostics[band.diagnostic].diagnostic.severity {
                Severity::Warning => 0,
                Severity::Error => 1,
            },
        );
        let palette = theme.palette();
        renderer.start_layer(clip);
        for band in &bands {
            let color = match snapshot.diagnostics[band.diagnostic].diagnostic.severity {
                Severity::Warning => palette.warning,
                Severity::Error => palette.danger,
            };
            renderer.fill_quad(
                renderer::Quad {
                    bounds: band.underline,
                    ..Default::default()
                },
                color,
            );
        }
        if self.hover_enabled
            && let Some(point) = cursor.position_over(clip)
        {
            let mut hits: Vec<_> = bands
                .iter()
                .filter(|band| band.bounds.contains(point))
                .map(|band| band.diagnostic)
                .collect();
            hits.sort_unstable();
            hits.dedup();
            hits.sort_by_key(|ordinal| {
                (
                    match snapshot.diagnostics[*ordinal].diagnostic.severity {
                        Severity::Error => 0,
                        Severity::Warning => 1,
                    },
                    *ordinal,
                )
            });
            if !hits.is_empty() {
                *details = draw_details(renderer, theme, snapshot.diagnostics, &hits, point, clip);
            }
        }
        renderer.end_layer();
    }
    fn mouse_interaction(
        &self,
        tree: &widget::Tree,
        layout: Layout<'_>,
        cursor: mouse::Cursor,
        viewport: &Rectangle,
        renderer: &R,
    ) -> mouse::Interaction {
        self.child.as_widget().mouse_interaction(
            &tree.children[0],
            layout,
            cursor,
            viewport,
            renderer,
        )
    }
    fn overlay<'b>(
        &'b mut self,
        tree: &'b mut widget::Tree,
        layout: Layout<'b>,
        renderer: &R,
        viewport: &Rectangle,
        translation: Vector,
    ) -> Option<overlay::Element<'b, Message, Theme, R>> {
        self.child.as_widget_mut().overlay(
            &mut tree.children[0],
            layout,
            renderer,
            viewport,
            translation,
        )
    }
}

impl<'a, Message: 'a, R> From<Decorations<'a, Message, R>> for Element<'a, Message, Theme, R>
where
    R: text::Renderer<
            Font = Font,
            Editor = graphics::text::Editor,
            Paragraph = graphics::text::Paragraph,
        > + 'a,
{
    fn from(value: Decorations<'a, Message, R>) -> Self {
        Element::new(value)
    }
}

fn draw_details<R: text::Renderer<Font = Font, Paragraph = graphics::text::Paragraph>>(
    renderer: &mut R,
    theme: &Theme,
    diagnostics: &[SourceDiagnostic],
    hits: &[usize],
    point: Point,
    clip: Rectangle,
) -> Option<DetailsParagraphs> {
    const PAD: f32 = 8.;
    if clip.width < 100. || clip.height < 80. {
        return None;
    }
    let width = 520_f32.min(clip.width);
    let mut details = Vec::new();
    for ordinal in hits.iter().take(4) {
        let issue = &diagnostics[*ordinal];
        let d = &issue.diagnostic;
        let severity = match d.severity {
            Severity::Error => "Error",
            Severity::Warning => "Warning",
        };
        let raw = format!(
            "{severity} [{}] · {}:{}\n{}",
            d.code, d.line, d.column, d.message
        );
        let mut value: String = raw.chars().take(1000).collect();
        if value.len() < raw.len() {
            value.push('…');
        }
        if !issue.related.is_empty() {
            value.push_str(&format!(
                "\n{} related location(s) in Problems",
                issue.related.len()
            ));
        }
        details.push(value);
    }
    let content = details.join("\n\n");
    let paragraph = graphics::text::Paragraph::with_text(text::Text {
        content: content.as_str(),
        bounds: Size::new(width - PAD * 2., f32::INFINITY),
        size: 12.into(),
        line_height: text::LineHeight::Relative(1.3),
        font: renderer.default_font(),
        align_x: text::Alignment::Left,
        align_y: alignment::Vertical::Top,
        shaping: text::Shaping::Advanced,
        wrapping: text::Wrapping::WordOrGlyph,
    });
    let remaining = hits.len().saturating_sub(4);
    let footer = if remaining > 0 {
        format!(
            "4 of {} shown · {remaining} more\nFull text: Actions → Source problems",
            hits.len()
        )
    } else {
        "Full text and locations: Actions → Source problems".into()
    };
    let footer_paragraph = graphics::text::Paragraph::with_text(text::Text {
        content: footer.as_str(),
        bounds: Size::new(width - PAD * 2., f32::INFINITY),
        size: 11.into(),
        line_height: text::LineHeight::Relative(1.2),
        font: renderer.default_font(),
        align_x: text::Alignment::Left,
        align_y: alignment::Vertical::Top,
        shaping: text::Shaping::Advanced,
        wrapping: text::Wrapping::WordOrGlyph,
    });
    let footer_height = footer_paragraph.min_bounds().height;
    let available_body = clip.height - PAD * 2. - footer_height - 4.;
    if available_body < 16. {
        return None;
    }
    let max_body_height =
        (clip.height * 0.6 - PAD * 2. - footer_height - 4.).clamp(16., available_body);
    let body_height = paragraph.min_bounds().height.min(max_body_height);
    let height = PAD * 2. + body_height + 4. + footer_height;
    let x = point.x.min(clip.x + clip.width - width).max(clip.x);
    let y = if point.y + 18. + height <= clip.y + clip.height {
        point.y + 18.
    } else {
        (point.y - 18. - height).max(clip.y)
    };
    let bounds = Rectangle::new(Point::new(x, y), Size::new(width, height));
    let palette = theme.extended_palette();
    renderer.fill_quad(
        renderer::Quad {
            bounds,
            border: iced::Border {
                color: palette.background.strong.color,
                width: 1.,
                radius: 4.into(),
            },
            ..Default::default()
        },
        palette.background.weak.color,
    );
    let body = Rectangle::new(
        Point::new(x + PAD, y + PAD),
        Size::new(width - PAD * 2., body_height),
    );
    renderer.fill_paragraph(
        &paragraph,
        body.position(),
        palette.background.weak.text,
        body,
    );
    let footer_bounds = Rectangle::new(
        Point::new(x + PAD, body.y + body.height + 4.),
        Size::new(width - PAD * 2., footer_height),
    );
    renderer.fill_paragraph(
        &footer_paragraph,
        footer_bounds.position(),
        palette.background.weak.text,
        footer_bounds,
    );
    Some(DetailsParagraphs {
        _body: paragraph,
        _footer: footer_paragraph,
    })
}

#[cfg(all(test, debug_assertions))]
pub(crate) mod tests;