hxy-view 0.1.0

//! Reusable egui hex-view widget.
//!
//! Renders bytes from a [`HexSource`] in a virtualised scroll view with a
//! configurable number of hex columns (16 by default), an address column,
//! and an ASCII sidebar. Supports click, shift-click, and drag across
//! arbitrary row boundaries to extend the selection. Highlights are
//! painted as contiguous bars across each row for readability.

#![forbid(unsafe_code)]

use egui::Align2;
use egui::Color32;
use egui::FontId;
use egui::Pos2;
use egui::Rect;
use egui::Sense;
use egui::Stroke;
use egui::StrokeKind;
use egui::TextStyle;
use egui::Ui;
use egui::Vec2;
use hxy_core::ByteLen;
use hxy_core::ByteOffset;
use hxy_core::ByteRange;
use hxy_core::ColumnCount;
use hxy_core::Error as CoreError;
use hxy_core::HexSource;
use hxy_core::Selection;

/// Where the byte-value palette should be applied.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ValueHighlight {
    /// Paint the palette as a background fill per byte. Text gets a
    /// contrast-adjusted color so it stays readable over the tint.
    Background,
    /// Tint the hex/ascii glyphs themselves; leave the background alone.
    Text,
}

/// Callback type for context menu rendering -- invoked on right-click
/// anywhere in the hex or ASCII pane.
pub type ContextMenuFn<'s> = Box<dyn FnOnce(&mut egui::Ui) + 's>;

/// Foreground + background colour choice for a single byte cell.
/// Returned by a [`ByteStylerFn`] so the consumer can fully override the
/// built-in palette's decision per byte (e.g. to highlight a matched
/// pattern, a diff, or bytes pointed to by a parsed template).
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub struct ByteStyle {
    /// Background tint for the byte cell. `None` falls back to whatever
    /// the configured palette would have chosen (or nothing, if none).
    pub bg: Option<Color32>,
    /// Text (glyph) color. `None` falls back to the default palette /
    /// theme behavior, including contrast adjustment against `bg`.
    pub fg: Option<Color32>,
}

/// Per-byte styler. Receives each byte's value and absolute file offset
/// and returns a [`ByteStyle`]. Consumers can use this to drive their
/// own colour logic (search hits, struct-field overlays, diff colours,
/// etc.) without subclassing the widget.
pub type ByteStylerFn<'s> = Box<dyn Fn(u8, ByteOffset) -> ByteStyle + 's>;

/// Formatter for address-column labels. Receives the offset of the row's
/// first byte and the width (in characters) the built-in address uses,
/// returns the string to render. Default formats as uppercase zero-padded
/// hex.
pub type AddressFormatterFn<'s> = Box<dyn Fn(ByteOffset, usize) -> String + 's>;

/// Formatter for the column-header row above the hex/ascii panes.
/// Receives the zero-based column index and returns its label. Default
/// renders an uppercase hex digit.
pub type ColumnHeaderFormatterFn<'s> = Box<dyn Fn(usize) -> String + 's>;

pub struct HexView<'s, S: HexSource + ?Sized> {
    source: &'s S,
    columns: ColumnCount,
    selection: &'s mut Option<Selection>,
    value_highlight: Option<ValueHighlight>,
    palette_override: Option<HighlightPalette>,
    byte_styler: Option<ByteStylerFn<'s>>,
    address_formatter: Option<AddressFormatterFn<'s>>,
    column_header_formatter: Option<ColumnHeaderFormatterFn<'s>>,
    context_menu: Option<ContextMenuFn<'s>>,
    minimap: bool,
    minimap_colored: bool,
    initial_scroll: Option<f32>,
    /// When set, overrides `initial_scroll` -- resolved at render
    /// time to place the row containing this byte near the top.
    scroll_to_byte: Option<ByteOffset>,
    /// Transient highlight for a byte range the consumer wants to
    /// draw attention to -- e.g. the template panel reflecting which
    /// field the pointer is over. Painted as a secondary fill that
    /// co-exists with the primary selection.
    hover_span: Option<ByteRange>,
    /// Leaf-field byte ranges from a template execution. The
    /// painter draws a thin outline around each range so the user
    /// can see field boundaries the same way 010 Editor does.
    /// Ranges must be sorted by start and must not overlap.
    field_boundaries: &'s [(ByteOffset, ByteLen)],
    /// Per-field tint, parallel to `field_boundaries`. When present
    /// and long enough, the minimap paints each hit byte with its
    /// field's colour so the user sees the same colour map in both
    /// views. Empty = no minimap override; byte-palette / grayscale
    /// is used instead.
    field_colors: &'s [Color32],
    /// Optional caller-supplied id salt; see [`HexView::id_salt`].
    id_salt: Option<egui::Id>,
}

impl<'s, S: HexSource + ?Sized> HexView<'s, S> {
    pub fn new(source: &'s S, selection: &'s mut Option<Selection>) -> Self {
        Self {
            source,
            columns: ColumnCount::DEFAULT,
            selection,
            value_highlight: None,
            palette_override: None,
            byte_styler: None,
            address_formatter: None,
            column_header_formatter: None,
            context_menu: None,
            minimap: false,
            minimap_colored: true,
            initial_scroll: None,
            scroll_to_byte: None,
            hover_span: None,
            field_boundaries: &[],
            field_colors: &[],
            id_salt: None,
        }
    }

    /// Supply leaf-field byte ranges from a template. The view paints
    /// a thin outline at each range's edges so users can see where
    /// template fields start and end without looking at the side
    /// panel. Must be sorted by start; caller guarantees no overlap.
    pub fn field_boundaries(mut self, boundaries: &'s [(ByteOffset, ByteLen)]) -> Self {
        self.field_boundaries = boundaries;
        self
    }

    /// Per-field colour, parallel to `field_boundaries`. The minimap
    /// overrides its byte-palette / grayscale fill with this colour
    /// for bytes that fall inside a field, so the overview strip
    /// matches the colouring the user sees in the main view.
    pub fn field_colors(mut self, colors: &'s [Color32]) -> Self {
        self.field_colors = colors;
        self
    }

    /// Stable seed for this view's internal widget ids. egui runs two
    /// layout passes; without a stable salt the hex body and column
    /// header -- both giant `allocate_exact_size` widgets -- get auto-
    /// ids derived from call-site position, which drifts under
    /// egui_dock's tab shuffling and triggers "Widget rect changed id
    /// between passes" warnings. Callers should pass something tied
    /// to the tab (e.g. `FileId`).
    pub fn id_salt(mut self, salt: impl std::hash::Hash) -> Self {
        self.id_salt = Some(egui::Id::new(salt));
        self
    }

    /// Tell the hex view to draw a secondary highlight over the given
    /// byte range. Consumer-driven; cleared when `None` is passed.
    pub fn hover_span(mut self, span: Option<ByteRange>) -> Self {
        self.hover_span = span;
        self
    }

    /// Install a per-byte styler. When set, the callback's returned
    /// [`ByteStyle`] takes precedence over the palette for that byte.
    /// `None` fields in the returned style fall back to the palette's
    /// choice (or theme default).
    pub fn byte_styler(mut self, f: impl Fn(u8, ByteOffset) -> ByteStyle + 's) -> Self {
        self.byte_styler = Some(Box::new(f));
        self
    }

    /// Override the address-column label formatter. Default is uppercase
    /// zero-padded hex.
    pub fn address_formatter(mut self, f: impl Fn(ByteOffset, usize) -> String + 's) -> Self {
        self.address_formatter = Some(Box::new(f));
        self
    }

    /// Override the column-header label formatter. Default is a single
    /// uppercase hex digit.
    pub fn column_header_formatter(mut self, f: impl Fn(usize) -> String + 's) -> Self {
        self.column_header_formatter = Some(Box::new(f));
        self
    }

    /// Scroll the view to `offset` (in pixels from the top of content)
    /// on this frame. Useful for restoring a saved scroll position on
    /// file reopen.
    pub fn scroll_to(mut self, offset: f32) -> Self {
        self.initial_scroll = Some(offset);
        self
    }

    /// Scroll so the row containing `byte` is near the top of the
    /// visible area. Resolved at render time using the current font
    /// and column settings; takes precedence over `scroll_to`.
    pub fn scroll_to_byte(mut self, byte: ByteOffset) -> Self {
        self.scroll_to_byte = Some(byte);
        self
    }

    /// Draw a narrow "minimap" strip on the right-hand side of the view
    /// that shows the full file colored by the current palette, with a
    /// viewport indicator, and supports click/drag to scroll.
    pub fn minimap(mut self, enabled: bool) -> Self {
        self.minimap = enabled;
        self
    }

    /// When the minimap is enabled, toggle whether bytes are painted in
    /// the highlight palette's colours or as a simple grayscale gradient
    /// keyed on byte value. Off is less busy.
    pub fn minimap_colored(mut self, colored: bool) -> Self {
        self.minimap_colored = colored;
        self
    }

    pub fn columns(mut self, cols: ColumnCount) -> Self {
        self.columns = cols;
        self
    }

    /// Toggle value-class highlighting. `None` disables, `Some(mode)`
    /// enables with either a background fill or text recoloring.
    pub fn value_highlight(mut self, mode: Option<ValueHighlight>) -> Self {
        self.value_highlight = mode;
        self
    }

    /// Override the built-in theme-based palette. Use this to plug in a
    /// class palette, a value gradient, or (later) a custom colour
    /// scheme.
    pub fn palette(mut self, palette: HighlightPalette) -> Self {
        self.palette_override = Some(palette);
        self
    }

    /// Install a context-menu callback rendered when the user
    /// right-clicks anywhere in the hex or ASCII pane. Callers use this
    /// to add per-app commands like Copy.
    pub fn context_menu(mut self, add_contents: impl FnOnce(&mut egui::Ui) + 's) -> Self {
        self.context_menu = Some(Box::new(add_contents));
        self
    }

    pub fn show(self, ui: &mut Ui) -> HexViewResponse {
        let Self {
            source,
            columns,
            selection,
            value_highlight,
            palette_override,
            byte_styler,
            address_formatter,
            column_header_formatter,
            context_menu,
            minimap,
            minimap_colored,
            initial_scroll,
            scroll_to_byte,
            hover_span,
            field_boundaries,
            field_colors,
            id_salt,
        } = self;
        let salt = id_salt.unwrap_or_else(|| ui.id().with("hxy_hex_view"));
        ui.push_id(salt, |ui| {
            let palette = value_highlight.map(|mode| {
                let palette = palette_override
                    .unwrap_or_else(|| HighlightPalette::for_theme_and_mode(ui.visuals().dark_mode, mode));
                (mode, palette)
            });
            let total_rows = row_count(source.len(), columns);
            let address_chars = address_hex_width(source.len());
            let font_id = TextStyle::Monospace.resolve(ui.style());
            let row_height = ui.text_style_height(&TextStyle::Monospace);
            let char_w = measure_char_width(ui, &font_id);
            let layout = RowLayout::compute(char_w, address_chars, columns);
            let source_len = source.len();

            let mut response = HexViewResponse::default();

            paint_column_header(ui, &layout, &font_id, row_height, column_header_formatter.as_deref());

            let scroll_id = ui.id().with("hxy_scroll");
            // Minimap click, explicit `scroll_to`, or a stashed pending value
            // from a prior frame can all drive the next scroll position.
            // `scroll_to_byte` takes precedence: compute the target row's
            // top Y from columns + row_height.
            let pending_offset = scroll_to_byte
                .map(|b| {
                    let row = b.get() / u64::from(columns.get());
                    (row as f32) * row_height
                })
                .or_else(|| ui.ctx().data_mut(|d| d.remove_temp::<f32>(scroll_id)))
                .or(initial_scroll);

            let minimap_width = if minimap { (char_w * 8.0).max(48.0) } else { 0.0 };
            let scrollbar_width = ui.style().spacing.scroll.bar_width.max(10.0);
            let avail = ui.available_rect_before_wrap();
            let hex_rect = Rect::from_min_size(
                avail.min,
                Vec2::new(avail.width() - minimap_width - scrollbar_width, avail.height()),
            );
            let minimap_rect =
                Rect::from_min_size(Pos2::new(hex_rect.right(), avail.top()), Vec2::new(minimap_width, avail.height()));
            let scrollbar_rect = Rect::from_min_size(
                Pos2::new(minimap_rect.right(), avail.top()),
                Vec2::new(scrollbar_width, avail.height()),
            );

            let hex_out = ui
                .scope_builder(egui::UiBuilder::new().max_rect(hex_rect), |ui| {
                    // Hex view owns scroll state but the visible bar lives
                    // in the rightmost column (past the minimap) as a
                    // separate widget, so we always hide the inner bar.
                    let mut area = egui::ScrollArea::vertical()
                        .auto_shrink([false, false])
                        .id_salt(scroll_id)
                        .scroll_bar_visibility(egui::scroll_area::ScrollBarVisibility::AlwaysHidden);
                    if let Some(target) = pending_offset {
                        area = area.vertical_scroll_offset(target);
                    }
                    area.show(ui, |ui| {
                        paint_and_interact(
                            ui,
                            &layout,
                            &font_id,
                            row_height,
                            total_rows,
                            source_len,
                            columns,
                            source,
                            selection,
                            palette.clone(),
                            byte_styler.as_deref(),
                            address_formatter.as_deref(),
                            context_menu,
                            hover_span,
                            field_boundaries,
                            &mut response,
                        );
                    })
                })
                .inner;

            response.scroll_offset = hex_out.state.offset.y;
            response.viewport_height = hex_out.inner_rect.height();

            if minimap {
                draw_minimap(
                    ui,
                    scroll_id,
                    minimap_rect,
                    source,
                    source_len,
                    palette,
                    minimap_colored,
                    row_height,
                    hex_out.state.offset.y,
                    hex_out.inner_rect.height(),
                    total_rows,
                    hover_span,
                    field_boundaries,
                    field_colors,
                );
            }

            draw_scrollbar(
                ui,
                scroll_id,
                scrollbar_rect,
                hex_out.state.offset.y,
                hex_out.inner_rect.height(),
                total_rows as f32 * row_height,
            );

            response
        })
        .inner
    }
}

#[derive(Default)]
pub struct HexViewResponse {
    pub hovered_offset: Option<ByteOffset>,
    pub error: Option<CoreError>,
    /// Scroll offset (in content pixels) at the end of this frame.
    pub scroll_offset: f32,
    /// Visible viewport height (in pixels).
    pub viewport_height: f32,
    /// Byte range actually rendered this frame (after clipping). Useful
    /// for consumers that want to paint overlays only over visible bytes.
    pub visible_range: Option<ByteRange>,
    /// Cursor byte offset from the current selection. Mirrors
    /// `selection.cursor`. None when no selection is set.
    pub cursor_offset: Option<ByteOffset>,
    /// Geometry info for the just-rendered frame. Lets consumers compute
    /// the screen rect of any visible byte (useful for painting overlays
    /// from outside the widget).
    pub layout: Option<HexViewLayout>,
}

/// Immutable snapshot of the HexView's per-frame geometry. Values are in
/// screen coordinates (absolute, already accounting for scroll). Only
/// valid within the current egui frame.
#[derive(Clone, Copy, Debug)]
pub struct HexViewLayout {
    block_rect: Rect,
    row_height: f32,
    columns: ColumnCount,
    source_len: ByteLen,
    inner: RowLayout,
}

impl HexViewLayout {
    /// Columns rendered per row.
    pub fn columns(&self) -> ColumnCount {
        self.columns
    }

    /// Screen rect of the hex cell for the given byte offset, if the
    /// offset is within the source. The rect may fall outside the
    /// currently-visible viewport -- callers doing overlay painting
    /// should intersect with the viewport clip.
    pub fn hex_cell_rect(&self, offset: ByteOffset) -> Option<Rect> {
        let (row_origin, col) = self.row_origin_and_col(offset)?;
        Some(self.inner.hex_cell_rect(row_origin, col, self.row_height))
    }

    /// Screen rect of the ASCII cell for the given byte offset.
    pub fn ascii_cell_rect(&self, offset: ByteOffset) -> Option<Rect> {
        let (row_origin, col) = self.row_origin_and_col(offset)?;
        Some(self.inner.ascii_cell_rect(row_origin, col, self.row_height))
    }

    /// Screen rect spanning a contiguous run of cells on a single row
    /// (from column `from` through column `to`, inclusive). Useful for
    /// drawing a bracket over an entire row's worth of selection. If
    /// the range crosses multiple rows, callers should issue one span
    /// rect per row.
    pub fn hex_span_rect(&self, row: hxy_core::RowIndex, from: usize, to: usize) -> Option<Rect> {
        let cols = usize::from(self.columns.get());
        if from >= cols || to >= cols || from > to {
            return None;
        }
        let row_origin = self.row_origin_for_row(row)?;
        Some(self.inner.hex_span_rect(row_origin, from, to, self.row_height))
    }

    fn row_origin_and_col(&self, offset: ByteOffset) -> Option<(Pos2, usize)> {
        if offset.get() >= self.source_len.get() {
            return None;
        }
        let cols = u64::from(self.columns.get());
        let row = offset.get() / cols;
        let col = (offset.get() % cols) as usize;
        Some((self.row_origin_for_row(hxy_core::RowIndex::new(row))?, col))
    }

    fn row_origin_for_row(&self, row: hxy_core::RowIndex) -> Option<Pos2> {
        let y = self.block_rect.top() + row.get() as f32 * self.row_height;
        Some(Pos2::new(self.block_rect.left(), y))
    }
}

fn row_count(len: ByteLen, columns: ColumnCount) -> usize {
    let len = len.get();
    if len == 0 {
        return 0;
    }
    let rows = len.div_ceil(columns.as_u64());
    usize::try_from(rows).unwrap_or(usize::MAX)
}

fn address_hex_width(len: ByteLen) -> usize {
    let bits_needed = 64 - len.get().saturating_sub(1).leading_zeros() as usize;
    bits_needed.div_ceil(4).max(8)
}

fn measure_char_width(ui: &Ui, font_id: &FontId) -> f32 {
    let painter = ui.painter();
    let galley = painter.layout_no_wrap("0".to_string(), font_id.clone(), Color32::WHITE);
    galley.size().x
}

/// Precomputed x-offsets for every slot in a row. Addressed in "points".
#[derive(Clone, Copy, Debug)]
struct RowLayout {
    address_w: f32,
    hex_start_x: f32,
    hex_cell_w: f32,
    hex_gap: f32,
    ascii_start_x: f32,
    ascii_cell_w: f32,
    total_width: f32,
    columns: ColumnCount,
    address_chars: usize,
}

impl RowLayout {
    fn compute(char_w: f32, address_chars: usize, columns: ColumnCount) -> Self {
        let address_w = char_w * address_chars as f32;
        let hex_gap = char_w * 0.5;
        let hex_cell_w = char_w * 2.0;
        let cols_f = f32::from(columns.get());
        let hex_total = cols_f * hex_cell_w + (cols_f - 1.0) * hex_gap;
        let section_gap = char_w * 2.0;
        let hex_start_x = address_w + section_gap;
        let ascii_cell_w = char_w;
        let ascii_start_x = hex_start_x + hex_total + section_gap;
        let ascii_total = cols_f * ascii_cell_w;
        Self {
            address_w,
            hex_start_x,
            hex_cell_w,
            hex_gap,
            ascii_start_x,
            ascii_cell_w,
            total_width: ascii_start_x + ascii_total,
            columns,
            address_chars,
        }
    }

    /// Background-tint rect for hex cell `col` that bleeds halfway into
    /// each side-gap so adjacent tints touch with no visible seam. The
    /// first/last columns clamp to the pane edges.
    fn hex_tint_rect(&self, row_origin: Pos2, col: usize, total_cols: usize, row_height: f32) -> Rect {
        let cell = self.hex_cell_rect(row_origin, col, row_height);
        let left = if col == 0 { cell.left() } else { cell.left() - self.hex_gap / 2.0 };
        let right = if col + 1 >= total_cols { cell.right() } else { cell.right() + self.hex_gap / 2.0 };
        Rect::from_min_max(Pos2::new(left, cell.top()), Pos2::new(right, cell.bottom()))
    }

    /// ASCII tint rect: ASCII cells already sit edge-to-edge, so this is
    /// just the cell rect with no rounding.
    fn ascii_tint_rect(&self, row_origin: Pos2, col: usize, _total_cols: usize, row_height: f32) -> Rect {
        self.ascii_cell_rect(row_origin, col, row_height)
    }

    fn hex_cell_rect(&self, row_origin: Pos2, col: usize, row_height: f32) -> Rect {
        let left = row_origin.x + self.hex_start_x + (col as f32) * (self.hex_cell_w + self.hex_gap);
        Rect::from_min_size(Pos2::new(left, row_origin.y), Vec2::new(self.hex_cell_w, row_height))
    }

    /// Rect spanning hex columns `from..=to` contiguously (no internal
    /// gaps between cells in the span).
    fn hex_span_rect(&self, row_origin: Pos2, from: usize, to: usize, row_height: f32) -> Rect {
        let start = self.hex_cell_rect(row_origin, from, row_height).left();
        let end = self.hex_cell_rect(row_origin, to, row_height).right();
        Rect::from_min_max(Pos2::new(start, row_origin.y), Pos2::new(end, row_origin.y + row_height))
    }

    fn ascii_cell_rect(&self, row_origin: Pos2, col: usize, row_height: f32) -> Rect {
        let left = row_origin.x + self.ascii_start_x + (col as f32) * self.ascii_cell_w;
        Rect::from_min_size(Pos2::new(left, row_origin.y), Vec2::new(self.ascii_cell_w, row_height))
    }

    fn ascii_span_rect(&self, row_origin: Pos2, from: usize, to: usize, row_height: f32) -> Rect {
        let start = self.ascii_cell_rect(row_origin, from, row_height).left();
        let end = self.ascii_cell_rect(row_origin, to, row_height).right();
        Rect::from_min_max(Pos2::new(start, row_origin.y), Pos2::new(end, row_origin.y + row_height))
    }

    fn address_rect(&self, row_origin: Pos2, row_height: f32) -> Rect {
        Rect::from_min_size(row_origin, Vec2::new(self.address_w, row_height))
    }

    /// Map a pointer position within the rendered block to `(row_in_block,
    /// column)`. `row_in_block` is clamped to `0..num_rows`; `column` is
    /// clamped to `0..columns`. Returns `None` only if the pointer's x is
    /// before the hex pane or past the ASCII pane.
    fn hit_test(&self, block_rect: Rect, pos: Pos2, row_height: f32, num_rows: usize) -> Option<HitRowCol> {
        let x = (pos.x - block_rect.left()).max(0.0);
        let y = (pos.y - block_rect.top()).clamp(0.0, num_rows.saturating_sub(1) as f32 * row_height);
        let row = ((y / row_height) as usize).min(num_rows.saturating_sub(1));

        let cols = usize::from(self.columns.get());
        if x >= self.hex_start_x && x < self.ascii_start_x {
            let local = x - self.hex_start_x;
            let stride = self.hex_cell_w + self.hex_gap;
            let col = ((local / stride) as usize).min(cols - 1);
            return Some(HitRowCol { row, col });
        }
        let ascii_end = self.ascii_start_x + (cols as f32) * self.ascii_cell_w;
        if x >= self.ascii_start_x && x < ascii_end {
            let local = x - self.ascii_start_x;
            let col = ((local / self.ascii_cell_w) as usize).min(cols - 1);
            return Some(HitRowCol { row, col });
        }
        None
    }
}

#[derive(Clone, Copy)]
struct HitRowCol {
    row: usize,
    col: usize,
}

/// Everything the painter needs that stays constant for the whole frame.
struct PaintCtx<'a> {
    layout: &'a RowLayout,
    font_id: &'a FontId,
    row_height: f32,
    columns: ColumnCount,
    palette: Option<(ValueHighlight, HighlightPalette)>,
    byte_styler: Option<&'a dyn Fn(u8, ByteOffset) -> ByteStyle>,
    address_formatter: Option<&'a dyn Fn(ByteOffset, usize) -> String>,
    colors: RowColors,
    selected_range: Option<ByteRange>,
    cursor_offset: Option<ByteOffset>,
    hover_offset: Option<ByteOffset>,
    hover_span: Option<ByteRange>,
    field_boundaries: &'a [(ByteOffset, ByteLen)],
}

/// Geometry + source metadata used for pointer hit-testing against the
/// full (scrolled) content rect.
struct HitCtx<'a> {
    layout: &'a RowLayout,
    block_rect: Rect,
    row_height: f32,
    columns: ColumnCount,
    total_rows: usize,
    source_len: ByteLen,
}

#[derive(Clone, Copy)]
struct RowColors {
    text: Color32,
    weak: Color32,
    selection_bg: Color32,
    selection_fg: Color32,
    cursor_stroke: Stroke,
    hover_stroke: Stroke,
}

#[allow(clippy::too_many_arguments)]
fn paint_and_interact<S: HexSource + ?Sized>(
    ui: &mut Ui,
    layout: &RowLayout,
    font_id: &FontId,
    row_height: f32,
    total_rows: usize,
    source_len: ByteLen,
    columns: ColumnCount,
    source: &S,
    selection: &mut Option<Selection>,
    palette: Option<(ValueHighlight, HighlightPalette)>,
    byte_styler: Option<&dyn Fn(u8, ByteOffset) -> ByteStyle>,
    address_formatter: Option<&dyn Fn(ByteOffset, usize) -> String>,
    context_menu: Option<ContextMenuFn<'_>>,
    hover_span: Option<ByteRange>,
    field_boundaries: &[(ByteOffset, ByteLen)],
    response_out: &mut HexViewResponse,
) {
    let cols = usize::from(columns.get());
    let total_height = total_rows as f32 * row_height;
    let block_size = Vec2::new(layout.total_width, total_height);
    let (block_rect, response) = ui.allocate_exact_size(block_size, Sense::click_and_drag());

    let hit = HitCtx { layout, block_rect, row_height, columns, total_rows, source_len };

    // Clip-driven visibility: paint only rows that intersect the scroll
    // area's clip rect, letting the area scroll with pixel granularity
    // rather than snapping to whole rows.
    let Some((first_visible, last_visible_exclusive)) =
        visible_rows(&block_rect, row_height, total_rows, ui.clip_rect())
    else {
        response_out.hovered_offset = None;
        if let Some(add) = context_menu {
            response.context_menu(add);
        }
        return;
    };

    let range_start = (first_visible as u64).saturating_mul(cols as u64).min(source_len.get());
    let range_end = (last_visible_exclusive as u64).saturating_mul(cols as u64).min(source_len.get());
    let Ok(read_range) = ByteRange::new(ByteOffset::new(range_start), ByteOffset::new(range_end)) else {
        return;
    };
    let bytes = match source.read(read_range) {
        Ok(b) => b,
        Err(e) => {
            response_out.error = Some(e);
            return;
        }
    };

    let weak = ui.visuals().weak_text_color();
    let colors = RowColors {
        text: ui.visuals().text_color(),
        weak,
        selection_bg: ui.visuals().selection.bg_fill,
        selection_fg: ui.visuals().selection.stroke.color,
        cursor_stroke: Stroke::new(1.5, ui.visuals().strong_text_color()),
        hover_stroke: Stroke::new(1.0, weak.gamma_multiply(0.9)),
    };

    let selected_range = selection.and_then(|s| {
        let r = s.range();
        if r.is_empty() { None } else { Some(r) }
    });
    let cursor_offset = selection.map(|s| s.cursor);
    let hover_offset = hovered_byte(ui, &response, &hit);

    let ctx = PaintCtx {
        layout,
        font_id,
        row_height,
        columns,
        palette,
        byte_styler,
        address_formatter,
        colors,
        selected_range,
        cursor_offset,
        hover_offset,
        hover_span,
        field_boundaries,
    };
    let painter = ui.painter_at(block_rect);
    paint_rows(&painter, &ctx, block_rect, first_visible, &bytes);

    apply_interaction(ui, &response, &hit, selection);

    response_out.hovered_offset = hover_offset;
    response_out.cursor_offset = cursor_offset;
    response_out.visible_range = Some(read_range);
    response_out.layout = Some(HexViewLayout { block_rect, row_height, columns, source_len, inner: *layout });

    if let Some(add) = context_menu {
        response.context_menu(add);
    }
}

fn visible_rows(block_rect: &Rect, row_height: f32, total_rows: usize, clip: Rect) -> Option<(usize, usize)> {
    if total_rows == 0 {
        return None;
    }
    let total_height = total_rows as f32 * row_height;
    let visible_top = (clip.top() - block_rect.top()).max(0.0);
    let visible_bottom = (clip.bottom() - block_rect.top()).clamp(0.0, total_height);
    if visible_bottom <= visible_top {
        return None;
    }
    let first = (visible_top / row_height).floor() as usize;
    let last = ((visible_bottom / row_height).ceil() as usize).min(total_rows);
    if first >= last { None } else { Some((first, last)) }
}

/// Paint in two passes so marker strokes (cursor/hover) end up on top of
/// every neighboring row's tint -- otherwise the cell to the right of the
/// cursor can paint its tint *over* the cursor stroke.
fn paint_rows(painter: &egui::Painter, ctx: &PaintCtx<'_>, block_rect: Rect, first_visible: usize, bytes: &[u8]) {
    let cols = usize::from(ctx.columns.get());

    for (chunk_idx, chunk) in bytes.chunks(cols).enumerate() {
        let row_idx = first_visible + chunk_idx;
        let row_origin = row_origin_for(block_rect, row_idx, ctx.row_height);
        let row_first_offset = ByteOffset::new((row_idx as u64) * (cols as u64));
        paint_row_backs_and_glyphs(painter, ctx, row_origin, row_first_offset, chunk);
    }
    for (chunk_idx, chunk) in bytes.chunks(cols).enumerate() {
        let row_idx = first_visible + chunk_idx;
        let row_origin = row_origin_for(block_rect, row_idx, ctx.row_height);
        let row_first_offset = ByteOffset::new((row_idx as u64) * (cols as u64));
        paint_row_marks(painter, ctx, row_origin, row_first_offset, chunk.len());
    }
}

fn row_origin_for(block_rect: Rect, row_idx: usize, row_height: f32) -> Pos2 {
    Pos2::new(block_rect.left(), block_rect.top() + (row_idx as f32) * row_height)
}

fn paint_row_backs_and_glyphs(
    painter: &egui::Painter,
    ctx: &PaintCtx<'_>,
    row_origin: Pos2,
    row_first_offset: ByteOffset,
    chunk: &[u8],
) {
    let cols = usize::from(ctx.columns.get());

    painter.text(
        ctx.layout.address_rect(row_origin, ctx.row_height).left_center(),
        Align2::LEFT_CENTER,
        match ctx.address_formatter {
            Some(f) => f(row_first_offset, ctx.layout.address_chars),
            None => format_address(row_first_offset, ctx.layout.address_chars),
        },
        ctx.font_id.clone(),
        ctx.colors.weak,
    );

    if let Some(range) = ctx.selected_range {
        paint_row_selection(
            painter,
            ctx.layout,
            row_origin,
            ctx.row_height,
            row_first_offset,
            chunk.len(),
            range,
            ctx.colors.selection_bg,
        );
    }
    if let Some(range) = ctx.hover_span {
        // Paint hover underneath the selection so the user's explicit
        // selection colour stays authoritative. Gamma-multiply the
        // selection background to get a softer tint that reads as a
        // secondary marker rather than a primary highlight.
        let tint = ctx.colors.selection_bg.gamma_multiply(0.45);
        paint_row_selection(
            painter,
            ctx.layout,
            row_origin,
            ctx.row_height,
            row_first_offset,
            chunk.len(),
            range,
            tint,
        );
    }

    for (i, byte) in chunk.iter().enumerate() {
        let byte_offset = ByteOffset::new(row_first_offset.get() + i as u64);
        let hex_rect = ctx.layout.hex_cell_rect(row_origin, i, ctx.row_height);
        let ascii_rect = ctx.layout.ascii_cell_rect(row_origin, i, ctx.row_height);
        let is_sel = ctx.selected_range.is_some_and(|r| r.contains(byte_offset));

        // Palette-derived defaults for this byte.
        let class_color = ctx.palette.as_ref().map(|(_, p)| p.color_for(*byte));
        let (palette_bg, palette_fg) = match ctx.palette.as_ref().map(|(m, _)| *m) {
            Some(ValueHighlight::Background) => {
                let bg = class_color;
                let fg = contrast_text_color(class_color.unwrap_or(ctx.colors.text), ctx.colors.text);
                (bg, fg)
            }
            Some(ValueHighlight::Text) => (None, class_color.unwrap_or(ctx.colors.text)),
            None => (None, ctx.colors.text),
        };

        // Per-byte styler overrides; `None` fields fall back to palette.
        let user_style = ctx.byte_styler.map(|f| f(*byte, byte_offset));
        let bg = user_style.and_then(|s| s.bg).or(palette_bg);
        let fg_override = user_style.and_then(|s| s.fg);

        if let Some(color) = bg.filter(|_| !is_sel) {
            let hex_tint = ctx.layout.hex_tint_rect(row_origin, i, cols, ctx.row_height);
            let ascii_tint = ctx.layout.ascii_tint_rect(row_origin, i, cols, ctx.row_height);
            painter.rect_filled(hex_tint, 0.0, color);
            painter.rect_filled(ascii_tint, 0.0, color);
        }

        let fg = if is_sel {
            ctx.colors.selection_fg
        } else if let Some(f) = fg_override {
            f
        } else if let Some(color) = bg {
            // Styler supplied a bg but no fg -- pick a contrast color.
            contrast_text_color(color, ctx.colors.text)
        } else {
            palette_fg
        };

        painter.text(hex_rect.center(), Align2::CENTER_CENTER, format!("{byte:02X}"), ctx.font_id.clone(), fg);
        let ch = if (0x20..0x7f).contains(byte) { *byte as char } else { '.' };
        painter.text(ascii_rect.center(), Align2::CENTER_CENTER, ch.to_string(), ctx.font_id.clone(), fg);
    }
}

fn paint_row_marks(
    painter: &egui::Painter,
    ctx: &PaintCtx<'_>,
    row_origin: Pos2,
    row_first_offset: ByteOffset,
    chunk_len: usize,
) {
    let cols = usize::from(ctx.columns.get());
    paint_row_field_outlines(painter, ctx, row_origin, row_first_offset, chunk_len, cols);
    for i in 0..chunk_len.min(cols) {
        let byte_offset = ByteOffset::new(row_first_offset.get() + i as u64);
        let hex_rect = ctx.layout.hex_cell_rect(row_origin, i, ctx.row_height);
        let ascii_rect = ctx.layout.ascii_cell_rect(row_origin, i, ctx.row_height);
        let hex_mark = hex_rect.expand2(Vec2::new(ctx.layout.hex_gap * 0.35, 2.0));
        let ascii_mark = ascii_rect.expand2(Vec2::new(0.5, 2.0));
        if ctx.cursor_offset == Some(byte_offset) {
            painter.rect_stroke(hex_mark, 2.0, ctx.colors.cursor_stroke, StrokeKind::Middle);
            painter.rect_stroke(ascii_mark, 2.0, ctx.colors.cursor_stroke, StrokeKind::Middle);
        } else if ctx.hover_offset == Some(byte_offset) {
            painter.rect_stroke(hex_mark, 2.0, ctx.colors.hover_stroke, StrokeKind::Middle);
            painter.rect_stroke(ascii_mark, 2.0, ctx.colors.hover_stroke, StrokeKind::Middle);
        }
    }
}

/// Paint hairline outlines around every template-field span that
/// overlaps this row. One rect per field per row; adjacent fields
/// meet edge-to-edge (the hex-cell gap is split down the middle so
/// their vertical edges share a column). Stroke endpoints are
/// snapped to physical pixel centres so 1px lines stay crisp.
fn paint_row_field_outlines(
    painter: &egui::Painter,
    ctx: &PaintCtx<'_>,
    row_origin: Pos2,
    row_first_offset: ByteOffset,
    chunk_len: usize,
    cols: usize,
) {
    if ctx.field_boundaries.is_empty() || chunk_len == 0 {
        return;
    }
    let stroke = Stroke::new(1.0, ctx.colors.weak.gamma_multiply(0.7));
    let row_first = row_first_offset.get();
    let row_last_exclusive = row_first + chunk_len.min(cols) as u64;
    let row_visible_cols = chunk_len.min(cols);

    let first_idx =
        ctx.field_boundaries.partition_point(|(start, len)| start.get().saturating_add(len.get()) <= row_first);

    for (start, len) in &ctx.field_boundaries[first_idx..] {
        let field_start = start.get();
        let field_end = field_start.saturating_add(len.get());
        if field_start >= row_last_exclusive {
            break;
        }
        let seg_start = field_start.max(row_first);
        let seg_end = field_end.min(row_last_exclusive);
        if seg_start >= seg_end {
            continue;
        }
        let first_col = (seg_start - row_first) as usize;
        let last_col = (seg_end - row_first - 1) as usize;

        let top_edge = field_start == seg_start;
        let bottom_edge = field_end == seg_end;
        let left_edge = field_start == seg_start;
        let right_edge = field_end == seg_end;

        let hex_rect = hex_outline_rect(ctx.layout, row_origin, ctx.row_height, first_col, last_col, row_visible_cols);
        let ascii_rect =
            ascii_outline_rect(ctx.layout, row_origin, ctx.row_height, first_col, last_col, row_visible_cols);

        for rect in [hex_rect, ascii_rect] {
            paint_rect_edges(painter, rect, stroke, top_edge, bottom_edge, left_edge, right_edge);
        }
    }
}

/// Rect covering hex columns `[first_col..=last_col]` with each side
/// bleeding halfway into the adjacent inter-cell gap -- matches the
/// tint-rect geometry so outlines and field tints coincide exactly.
/// First / last columns of the row clamp to the pane edges so two
/// rows' worth of outlines don't step sideways at the wrap.
fn hex_outline_rect(
    layout: &RowLayout,
    row_origin: Pos2,
    row_height: f32,
    first_col: usize,
    last_col: usize,
    total_cols: usize,
) -> Rect {
    let left_cell = layout.hex_cell_rect(row_origin, first_col, row_height);
    let right_cell = layout.hex_cell_rect(row_origin, last_col, row_height);
    let half_gap = layout.hex_gap * 0.5;
    let left = if first_col == 0 { left_cell.left() } else { left_cell.left() - half_gap };
    let right = if last_col + 1 >= total_cols { right_cell.right() } else { right_cell.right() + half_gap };
    Rect::from_min_max(Pos2::new(left, row_origin.y), Pos2::new(right, row_origin.y + row_height))
}

/// ASCII cells already sit edge-to-edge, so the span rect needs no
/// gap fudging -- the tint-rect math is just `cell_rect` union.
fn ascii_outline_rect(
    layout: &RowLayout,
    row_origin: Pos2,
    row_height: f32,
    first_col: usize,
    last_col: usize,
    _total_cols: usize,
) -> Rect {
    let left = layout.ascii_cell_rect(row_origin, first_col, row_height).left();
    let right = layout.ascii_cell_rect(row_origin, last_col, row_height).right();
    Rect::from_min_max(Pos2::new(left, row_origin.y), Pos2::new(right, row_origin.y + row_height))
}

fn paint_rect_edges(
    painter: &egui::Painter,
    rect: Rect,
    stroke: Stroke,
    top: bool,
    bottom: bool,
    left: bool,
    right: bool,
) {
    let ppp = painter.pixels_per_point();
    let snap_x = |x: f32| (x * ppp).round() / ppp + 0.5 / ppp;
    let snap_y = |y: f32| (y * ppp).round() / ppp + 0.5 / ppp;
    let l = snap_x(rect.left());
    let r = snap_x(rect.right());
    let t = snap_y(rect.top());
    let b = snap_y(rect.bottom());
    if top {
        painter.line_segment([Pos2::new(l, t), Pos2::new(r, t)], stroke);
    }
    if bottom {
        painter.line_segment([Pos2::new(l, b), Pos2::new(r, b)], stroke);
    }
    if left {
        painter.line_segment([Pos2::new(l, t), Pos2::new(l, b)], stroke);
    }
    if right {
        painter.line_segment([Pos2::new(r, t), Pos2::new(r, b)], stroke);
    }
}

#[allow(clippy::too_many_arguments)]
fn paint_row_selection(
    painter: &egui::Painter,
    layout: &RowLayout,
    row_origin: Pos2,
    row_height: f32,
    row_first_offset: ByteOffset,
    chunk_len: usize,
    selection: ByteRange,
    bg: Color32,
) {
    let cols = usize::from(layout.columns.get());
    let row_start = row_first_offset.get();
    let row_end = row_start + chunk_len as u64;

    let sel_start = selection.start().get();
    let sel_end = selection.end().get();
    if sel_end <= row_start || sel_start >= row_end {
        return;
    }

    let local_from = (sel_start.saturating_sub(row_start)) as usize;
    let local_to_exclusive = (sel_end.min(row_end).saturating_sub(row_start)) as usize;
    if local_to_exclusive == 0 || local_from >= cols {
        return;
    }
    let local_to = local_to_exclusive.saturating_sub(1);

    let hex_bar = layout.hex_span_rect(row_origin, local_from, local_to, row_height);
    let ascii_bar = layout.ascii_span_rect(row_origin, local_from, local_to, row_height);
    painter.rect_filled(hex_bar, 2.0, bg);
    painter.rect_filled(ascii_bar, 2.0, bg);
}

fn apply_interaction(ui: &Ui, response: &egui::Response, hit: &HitCtx<'_>, selection: &mut Option<Selection>) {
    let cols = usize::from(hit.columns.get());
    let shift = ui.input(|i| i.modifiers.shift);
    let active = response.dragged() || response.drag_started() || response.clicked();
    if !active {
        return;
    }

    let pos = response.interact_pointer_pos().or_else(|| ui.ctx().input(|i| i.pointer.interact_pos()));
    let Some(pos) = pos else { return };
    let Some(rc) = hit.layout.hit_test(hit.block_rect, pos, hit.row_height, hit.total_rows) else {
        return;
    };
    let Some(hit_offset) = hit_to_offset(rc, cols, hit.source_len) else { return };

    if response.drag_started() {
        *selection = Some(match (shift, *selection) {
            (true, Some(existing)) => Selection { anchor: existing.anchor, cursor: hit_offset },
            _ => Selection::caret(hit_offset),
        });
    } else if response.dragged() {
        match selection.as_mut() {
            Some(s) => s.cursor = hit_offset,
            None => *selection = Some(Selection::caret(hit_offset)),
        }
    } else if response.clicked() {
        *selection = Some(match (shift, *selection) {
            (true, Some(existing)) => Selection { anchor: existing.anchor, cursor: hit_offset },
            _ => Selection::caret(hit_offset),
        });
    }
}

fn hit_to_offset(hit: HitRowCol, cols: usize, source_len: ByteLen) -> Option<ByteOffset> {
    let offset = (hit.row as u64).checked_mul(cols as u64)?.checked_add(hit.col as u64)?;
    if offset >= source_len.get() {
        if source_len.get() == 0 {
            return None;
        }
        return Some(ByteOffset::new(source_len.get() - 1));
    }
    Some(ByteOffset::new(offset))
}

#[allow(clippy::too_many_arguments)]
fn hovered_byte(ui: &Ui, response: &egui::Response, hit: &HitCtx<'_>) -> Option<ByteOffset> {
    let pos = response.hover_pos().or_else(|| {
        response.is_pointer_button_down_on().then(|| ui.ctx().input(|i| i.pointer.latest_pos())).flatten()
    })?;
    if !hit.block_rect.contains(pos) {
        return None;
    }
    let rc = hit.layout.hit_test(hit.block_rect, pos, hit.row_height, hit.total_rows)?;
    hit_to_offset(rc, usize::from(hit.columns.get()), hit.source_len)
}

/// Colour source for byte-value tinting. Plugins can hand a fully-
/// specified 256-entry table via [`Self::Custom`] so a template run
/// can override the user's default palette for the duration.
#[derive(Clone, Debug)]
pub enum HighlightPalette {
    Class(BytePalette),
    Value(ValueGradient),
    /// Plugin-supplied palette: one colour per byte value, held
    /// behind an `Arc` so cloning the enum is cheap.
    Custom(std::sync::Arc<[Color32; 256]>),
}

impl HighlightPalette {
    pub fn for_theme_and_mode(dark: bool, mode: ValueHighlight) -> Self {
        Self::Class(BytePalette::for_theme_and_mode(dark, mode))
    }

    pub fn color_for(&self, byte: u8) -> Color32 {
        match self {
            Self::Class(p) => p.color_for(byte),
            Self::Value(g) => g.color_for(byte),
            Self::Custom(table) => table[byte as usize],
        }
    }
}

/// Every byte value gets a unique colour from a fixed HSL hue wheel.
/// Saturation and lightness are tuned per theme/mode so the resulting
/// colours stay readable under the view's fixed text contrast rules.
#[derive(Clone, Copy, Debug)]
pub struct ValueGradient {
    pub saturation: f32,
    pub lightness: f32,
}

impl ValueGradient {
    pub const BG_DARK: Self = Self { saturation: 0.55, lightness: 0.32 };
    pub const BG_LIGHT: Self = Self { saturation: 0.5, lightness: 0.78 };
    pub const TEXT_DARK: Self = Self { saturation: 0.75, lightness: 0.68 };
    pub const TEXT_LIGHT: Self = Self { saturation: 0.7, lightness: 0.4 };

    pub fn for_theme_and_mode(dark: bool, mode: ValueHighlight) -> Self {
        match (dark, mode) {
            (true, ValueHighlight::Background) => Self::BG_DARK,
            (false, ValueHighlight::Background) => Self::BG_LIGHT,
            (true, ValueHighlight::Text) => Self::TEXT_DARK,
            (false, ValueHighlight::Text) => Self::TEXT_LIGHT,
        }
    }

    pub fn color_for(&self, byte: u8) -> Color32 {
        let hue = (f32::from(byte) / 256.0) * 360.0;
        hsl_to_rgb(hue, self.saturation, self.lightness)
    }
}

fn hsl_to_rgb(h: f32, s: f32, l: f32) -> Color32 {
    let c = (1.0 - (2.0 * l - 1.0).abs()) * s;
    let h_norm = h / 60.0;
    let x = c * (1.0 - (h_norm.rem_euclid(2.0) - 1.0).abs());
    let (r1, g1, b1) = match h_norm as u32 {
        0 => (c, x, 0.0),
        1 => (x, c, 0.0),
        2 => (0.0, c, x),
        3 => (0.0, x, c),
        4 => (x, 0.0, c),
        _ => (c, 0.0, x),
    };
    let m = l - c / 2.0;
    let cv = |v: f32| ((v + m).clamp(0.0, 1.0) * 255.0).round() as u8;
    Color32::from_rgb(cv(r1), cv(g1), cv(b1))
}

/// Palette for byte-class tinting. Each variant of [`ByteClass`] maps
/// to one colour. Rendered text remains readable via the view's
/// contrast-adjustment.
#[derive(Clone, Copy, Debug)]
pub struct BytePalette {
    pub null: Color32,
    pub all_bits: Color32,
    pub whitespace: Color32,
    pub printable: Color32,
    pub control: Color32,
    pub extended: Color32,
}

impl BytePalette {
    /// Pick a palette variant appropriate for the theme and highlight
    /// mode. Background mode uses muted semi-transparent tints;
    /// text mode uses saturated opaque colors readable against the theme
    /// background.
    pub fn for_theme_and_mode(dark: bool, mode: ValueHighlight) -> Self {
        match (dark, mode) {
            (true, ValueHighlight::Background) => Self::BG_DARK,
            (false, ValueHighlight::Background) => Self::BG_LIGHT,
            (true, ValueHighlight::Text) => Self::TEXT_DARK,
            (false, ValueHighlight::Text) => Self::TEXT_LIGHT,
        }
    }

    pub const BG_DARK: Self = Self {
        null: Color32::from_rgb(60, 60, 64),
        all_bits: Color32::from_rgb(200, 150, 40),
        whitespace: Color32::from_rgb(50, 90, 140),
        printable: Color32::from_rgb(40, 120, 60),
        control: Color32::from_rgb(150, 60, 60),
        extended: Color32::from_rgb(120, 60, 140),
    };

    pub const BG_LIGHT: Self = Self {
        null: Color32::from_rgb(220, 220, 220),
        all_bits: Color32::from_rgb(245, 215, 110),
        whitespace: Color32::from_rgb(180, 210, 240),
        printable: Color32::from_rgb(190, 235, 200),
        control: Color32::from_rgb(240, 190, 190),
        extended: Color32::from_rgb(225, 195, 240),
    };

    pub const TEXT_DARK: Self = Self {
        null: Color32::from_rgb(140, 140, 140),
        all_bits: Color32::from_rgb(255, 200, 80),
        whitespace: Color32::from_rgb(120, 180, 240),
        printable: Color32::from_rgb(120, 220, 140),
        control: Color32::from_rgb(240, 130, 130),
        extended: Color32::from_rgb(210, 140, 230),
    };

    pub const TEXT_LIGHT: Self = Self {
        null: Color32::from_rgb(120, 120, 120),
        all_bits: Color32::from_rgb(180, 120, 20),
        whitespace: Color32::from_rgb(30, 90, 180),
        printable: Color32::from_rgb(30, 130, 60),
        control: Color32::from_rgb(180, 50, 50),
        extended: Color32::from_rgb(130, 40, 170),
    };

    pub fn color_for(&self, byte: u8) -> Color32 {
        match ByteClass::of(byte) {
            ByteClass::Null => self.null,
            ByteClass::AllBits => self.all_bits,
            ByteClass::Whitespace => self.whitespace,
            ByteClass::Printable => self.printable,
            ByteClass::Control => self.control,
            ByteClass::Extended => self.extended,
        }
    }
}

/// Pick a glyph color for text painted on top of `bg`. Brighter
/// backgrounds get a darker grey; darker backgrounds get near-white. The
/// `default_fg` is returned unchanged when `bg` is transparent.
fn contrast_text_color(bg: Color32, default_fg: Color32) -> Color32 {
    if bg.a() == 0 {
        return default_fg;
    }
    let luminance = 0.299 * f32::from(bg.r()) + 0.587 * f32::from(bg.g()) + 0.114 * f32::from(bg.b());
    let t = (luminance / 255.0).clamp(0.0, 1.0);
    let white = 240.0_f32;
    let gray = 30.0_f32;
    let v = (white * (1.0 - t) + gray * t).round() as u8;
    Color32::from_rgb(v, v, v)
}

/// Coarse categorization of a byte value for palette lookup.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub(crate) enum ByteClass {
    Null,
    AllBits,
    Whitespace,
    Printable,
    Control,
    Extended,
}

impl ByteClass {
    pub(crate) fn of(byte: u8) -> Self {
        match byte {
            0x00 => Self::Null,
            0xFF => Self::AllBits,
            b'\t' | b'\n' | b'\r' => Self::Whitespace,
            0x01..=0x1F | 0x7F => Self::Control,
            0x20..=0x7E => Self::Printable,
            0x80..=0xFE => Self::Extended,
        }
    }
}

#[allow(clippy::too_many_arguments)]
fn draw_minimap<S: HexSource + ?Sized>(
    ui: &mut Ui,
    scroll_id: egui::Id,
    minimap_rect: Rect,
    source: &S,
    source_len: ByteLen,
    palette: Option<(ValueHighlight, HighlightPalette)>,
    colored: bool,
    row_height: f32,
    current_offset: f32,
    viewport_height: f32,
    total_rows: usize,
    hover_span: Option<ByteRange>,
    field_boundaries: &[(ByteOffset, ByteLen)],
    field_colors: &[Color32],
) {
    if minimap_rect.width() < 1.0 || minimap_rect.height() < 1.0 || source_len.get() == 0 {
        return;
    }
    let cols = 16usize;
    let response = ui.allocate_rect(minimap_rect, Sense::click_and_drag());
    let painter = ui.painter_at(minimap_rect);
    painter.rect_filled(minimap_rect, 0.0, ui.visuals().extreme_bg_color);

    let cell_w = (minimap_rect.width() / cols as f32).max(1.0);
    // Fixed zoom: each hex row gets a constant number of minimap pixels
    // regardless of file size. The minimap is a window onto the file
    // that scrolls with the main viewport, not a whole-file overview.
    let cell_h = 2.0_f32;

    let minimap_capacity_rows = (minimap_rect.height() / cell_h).floor() as usize;
    if minimap_capacity_rows == 0 {
        return;
    }
    let fallback = ui.visuals().text_color();
    let len = source_len.get();
    let dark = ui.visuals().dark_mode;

    // Map the minimap window's top row linearly to the file's scroll
    // fraction. That way the viewport indicator travels the full height
    // of the minimap as you scroll from start to end -- like a regular
    // scrollbar -- instead of pinning itself to the middle.
    let viewport_top_row_f = (current_offset / row_height).max(0.0);
    let viewport_rows_f = (viewport_height / row_height).max(1.0);
    let capacity_f = minimap_capacity_rows as f32;
    let content_height = total_rows as f32 * row_height;
    let max_scroll = (content_height - viewport_height).max(0.0);
    let scroll_frac = if max_scroll > 0.0 { (current_offset / max_scroll).clamp(0.0, 1.0) } else { 0.0 };
    let max_top = (total_rows as f32 - capacity_f).max(0.0);
    let window_top_f = scroll_frac * max_top;
    let window_top_row = window_top_f.floor() as u64;
    let shown_rows = minimap_capacity_rows.min(total_rows.saturating_sub(window_top_row as usize));

    // Single contiguous read for all rows visible in the window.
    let read_start = window_top_row.saturating_mul(cols as u64).min(len);
    let read_end = read_start.saturating_add(shown_rows as u64 * cols as u64).min(len);
    let bytes = ByteRange::new(ByteOffset::new(read_start), ByteOffset::new(read_end))
        .ok()
        .and_then(|r| source.read(r).ok())
        .unwrap_or_default();

    let field_override = !field_boundaries.is_empty() && !field_colors.is_empty();
    for i in 0..shown_rows {
        let chunk_start = i * cols;
        if chunk_start >= bytes.len() {
            break;
        }
        let chunk_end = (chunk_start + cols).min(bytes.len());
        let chunk = &bytes[chunk_start..chunk_end];
        let y = minimap_rect.top() + i as f32 * cell_h;
        let row_base_offset = read_start + (i as u64) * cols as u64;
        for (c, byte) in chunk.iter().enumerate() {
            let x = minimap_rect.left() + c as f32 * cell_w;
            let offset = row_base_offset + c as u64;
            let field_color =
                if field_override { field_color_for(field_boundaries, field_colors, offset) } else { None };
            let color = field_color.unwrap_or_else(|| {
                if colored {
                    palette.as_ref().map(|(_, p)| p.color_for(*byte)).unwrap_or(fallback)
                } else {
                    grayscale_for_byte(*byte, dark)
                }
            });
            painter.rect_filled(Rect::from_min_size(Pos2::new(x, y), Vec2::new(cell_w, cell_h)), 0.0, color);
        }
    }

    // Viewport indicator at its absolute position inside the scrolled
    // window. High-contrast outline + accent bracket for readability
    // over any palette.
    let indicator_top_y = minimap_rect.top() + (viewport_top_row_f - window_top_f) * cell_h;
    let indicator_height = viewport_rows_f * cell_h;
    let indicator = Rect::from_min_max(
        Pos2::new(minimap_rect.left(), indicator_top_y.max(minimap_rect.top())),
        Pos2::new(minimap_rect.right(), (indicator_top_y + indicator_height).min(minimap_rect.bottom())),
    );
    let (fill, outline) = if dark {
        (Color32::from_rgba_unmultiplied(255, 255, 255, 70), Color32::WHITE)
    } else {
        (Color32::from_rgba_unmultiplied(0, 0, 0, 70), Color32::from_rgb(20, 20, 20))
    };
    painter.rect_filled(indicator, 0.0, fill);
    painter.rect_stroke(indicator, 0.0, Stroke::new(2.0, outline), StrokeKind::Inside);
    let accent = ui.visuals().selection.bg_fill;
    let bracket = Rect::from_min_max(indicator.left_top(), Pos2::new(indicator.left() + 4.0, indicator.bottom()));
    painter.rect_filled(bracket, 0.0, accent);

    // Hover-span marker: mirrors the secondary highlight the hex view
    // draws when the template panel is pointing at a field. When the
    // span is outside the currently-shown minimap window, draw a
    // small caret at the top/bottom edge so the user still has a
    // direction to scroll.
    if let Some(span) = hover_span {
        paint_hover_span_on_minimap(
            &painter,
            minimap_rect,
            span,
            cols as u64,
            cell_h,
            window_top_row,
            shown_rows as u64,
            accent,
        );
    }

    // Click/drag maps pointer y to a position in the *whole file* so a
    // top->bottom drag on the minimap scrolls from file start to end in
    // one motion, regardless of how much content the fixed-zoom window
    // happens to be showing right now.
    let pointer = response
        .interact_pointer_pos()
        .or_else(|| response.hover_pos().filter(|_| response.is_pointer_button_down_on()));
    if let Some(pos) = pointer.filter(|_| response.dragged() || response.clicked() || response.drag_started()) {
        let y = (pos.y - minimap_rect.top()).clamp(0.0, minimap_rect.height());
        let frac = y / minimap_rect.height();
        let target_scroll = (frac * max_scroll).clamp(0.0, max_scroll);
        ui.ctx().data_mut(|d| d.insert_temp(scroll_id, target_scroll));
        ui.ctx().request_repaint();
    }
}

/// Paint the template-panel's hover span on the minimap. Splits into
/// two cases: the span intersects the currently-visible minimap
/// window (-> highlight the matching rows), or the span is off-screen
/// (-> small caret at the top or bottom edge pointing toward it).
#[allow(clippy::too_many_arguments)]
fn paint_hover_span_on_minimap(
    painter: &egui::Painter,
    minimap_rect: Rect,
    span: ByteRange,
    cols: u64,
    cell_h: f32,
    window_top_row: u64,
    shown_rows: u64,
    accent: Color32,
) {
    let start = span.start().get();
    let end_exclusive = span.end().get();
    if end_exclusive <= start || cols == 0 {
        return;
    }
    let span_first_row = start / cols;
    let span_last_row_inclusive = (end_exclusive - 1) / cols;
    let window_end_row = window_top_row.saturating_add(shown_rows);

    // Out-of-window markers: draw a thin caret at the edge the span
    // lies beyond so the user knows which way to scroll.
    if span_last_row_inclusive < window_top_row {
        let top = minimap_rect.top();
        let caret = Rect::from_min_size(Pos2::new(minimap_rect.right() - 6.0, top), Vec2::new(6.0, 4.0));
        painter.rect_filled(caret, 0.0, accent);
        return;
    }
    if span_first_row >= window_end_row {
        let bottom = minimap_rect.bottom();
        let caret = Rect::from_min_size(Pos2::new(minimap_rect.right() - 6.0, bottom - 4.0), Vec2::new(6.0, 4.0));
        painter.rect_filled(caret, 0.0, accent);
        return;
    }

    // Span intersects the window -- shade the overlap rows.
    let shaded_top_row = span_first_row.max(window_top_row);
    let shaded_bot_row_inclusive = span_last_row_inclusive.min(window_end_row.saturating_sub(1));
    let rel_top = (shaded_top_row - window_top_row) as f32 * cell_h;
    let rel_bot = ((shaded_bot_row_inclusive + 1) - window_top_row) as f32 * cell_h;
    let rect = Rect::from_min_max(
        Pos2::new(minimap_rect.left(), minimap_rect.top() + rel_top),
        Pos2::new(minimap_rect.right(), minimap_rect.top() + rel_bot),
    );
    // Translucent fill on top of the minimap cells, plus an accent
    // line along the left edge so single-row spans still register.
    painter.rect_filled(rect, 0.0, accent.gamma_multiply(0.35));
    let edge = Rect::from_min_size(rect.left_top(), Vec2::new(2.0, rect.height()));
    painter.rect_filled(edge, 0.0, accent);
}

/// Custom vertical scrollbar rendered in the strip to the right of the
/// minimap. The inner scroll area's own bar is hidden, so this is the
/// only visible scroll indicator. Click/drag maps pointer y linearly to
/// the file's full scroll range, like the minimap's interaction.
fn draw_scrollbar(
    ui: &mut Ui,
    scroll_id: egui::Id,
    rect: Rect,
    current_offset: f32,
    viewport_height: f32,
    content_height: f32,
) {
    if rect.width() < 1.0 || rect.height() < 1.0 {
        return;
    }
    let response = ui.allocate_rect(rect, Sense::click_and_drag());
    let painter = ui.painter_at(rect);

    let track_color = ui.visuals().extreme_bg_color;
    painter.rect_filled(rect, 3.0, track_color);

    if content_height <= viewport_height {
        return;
    }

    let viewport_frac = (viewport_height / content_height).clamp(0.05, 1.0);
    let max_scroll = (content_height - viewport_height).max(1.0);
    let scroll_frac = (current_offset / max_scroll).clamp(0.0, 1.0);

    let thumb_h = (viewport_frac * rect.height()).max(18.0);
    let thumb_top = rect.top() + scroll_frac * (rect.height() - thumb_h);
    let thumb_rect =
        Rect::from_min_size(Pos2::new(rect.left() + 2.0, thumb_top), Vec2::new(rect.width() - 4.0, thumb_h));

    let widget_visuals = if response.is_pointer_button_down_on() {
        ui.visuals().widgets.active
    } else if response.hovered() {
        ui.visuals().widgets.hovered
    } else {
        ui.visuals().widgets.inactive
    };
    painter.rect_filled(thumb_rect, 3.0, widget_visuals.bg_fill);

    let pointer = response
        .interact_pointer_pos()
        .or_else(|| response.hover_pos().filter(|_| response.is_pointer_button_down_on()));
    if let Some(pos) = pointer.filter(|_| response.dragged() || response.clicked() || response.drag_started()) {
        let y = (pos.y - rect.top() - thumb_h * 0.5).clamp(0.0, rect.height() - thumb_h);
        let frac = if rect.height() > thumb_h { y / (rect.height() - thumb_h) } else { 0.0 };
        let target = (frac * max_scroll).clamp(0.0, max_scroll);
        ui.ctx().data_mut(|d| d.insert_temp(scroll_id, target));
        ui.ctx().request_repaint();
    }
}

/// Uncoloured minimap fallback. Byte value 0x00 maps to the theme's
/// darkest content shade and 0xFF to near-white (or the opposite on
/// light mode), giving a faint brightness gradient that still reveals
/// structure without dragging in the palette.
/// Look up the template-field colour for `byte_offset` by binary-
/// searching the sorted `boundaries`. Returns `None` when the offset
/// doesn't fall inside any field or when `colors` is too short.
fn field_color_for(boundaries: &[(ByteOffset, ByteLen)], colors: &[Color32], byte_offset: u64) -> Option<Color32> {
    let idx = boundaries.partition_point(|(start, _)| start.get() <= byte_offset);
    if idx == 0 {
        return None;
    }
    let (start, len) = boundaries[idx - 1];
    let end = start.get().saturating_add(len.get());
    if byte_offset < end { colors.get(idx - 1).copied() } else { None }
}

fn grayscale_for_byte(byte: u8, dark: bool) -> Color32 {
    let t = f32::from(byte) / 255.0;
    let (lo, hi) = if dark { (40.0, 230.0) } else { (40.0, 220.0) };
    let v = (lo * (1.0 - t) + hi * t).round() as u8;
    Color32::from_rgb(v, v, v)
}

/// Paint a one-row header with column indices ("0" through "f" in a 16-
/// column view) aligned with each hex cell. Rendered outside the scroll
/// area so it stays in view while scrolling.
fn paint_column_header(
    ui: &mut Ui,
    layout: &RowLayout,
    font_id: &FontId,
    row_height: f32,
    formatter: Option<&dyn Fn(usize) -> String>,
) {
    let cols = usize::from(layout.columns.get());
    let header_height = row_height * 0.75;
    let (header_rect, _) = ui.allocate_exact_size(Vec2::new(layout.total_width, header_height), Sense::empty());
    let painter = ui.painter_at(header_rect);
    let color = ui.visuals().weak_text_color();
    let origin = header_rect.min;
    for col in 0..cols {
        let label = match formatter {
            Some(f) => f(col),
            None => format!("{col:X}"),
        };
        let cell = layout.hex_cell_rect(origin, col, header_height);
        painter.text(cell.center(), Align2::CENTER_CENTER, &label, font_id.clone(), color);
        let ascii_cell = layout.ascii_cell_rect(origin, col, header_height);
        painter.text(ascii_cell.center(), Align2::CENTER_CENTER, &label, font_id.clone(), color);
    }
    let divider_y = header_rect.bottom();
    painter.line_segment(
        [Pos2::new(header_rect.left(), divider_y), Pos2::new(header_rect.right(), divider_y)],
        Stroke::new(1.0, ui.visuals().weak_text_color().gamma_multiply(0.5)),
    );
}

fn format_address(offset: ByteOffset, width: usize) -> String {
    format!("{:0width$X}", offset.get(), width = width)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn address_width_scales_with_length() {
        assert_eq!(address_hex_width(ByteLen::new(0)), 8);
        assert_eq!(address_hex_width(ByteLen::new(256)), 8);
        assert_eq!(address_hex_width(ByteLen::new(1u64 << 32)), 8);
        assert_eq!(address_hex_width(ByteLen::new((1u64 << 32) + 1)), 9);
    }

    #[test]
    fn row_count_handles_partial_row() {
        let cols = ColumnCount::new(16).unwrap();
        assert_eq!(row_count(ByteLen::new(0), cols), 0);
        assert_eq!(row_count(ByteLen::new(1), cols), 1);
        assert_eq!(row_count(ByteLen::new(16), cols), 1);
        assert_eq!(row_count(ByteLen::new(17), cols), 2);
    }

    #[test]
    fn format_address_zero_pads() {
        assert_eq!(format_address(ByteOffset::new(0x1a), 8), "0000001A");
    }

    #[test]
    fn hex_span_covers_contiguous_columns() {
        let cols = ColumnCount::new(16).unwrap();
        let layout = RowLayout::compute(10.0, 8, cols);
        let origin = Pos2::ZERO;
        let span = layout.hex_span_rect(origin, 3, 7, 20.0);
        let c3 = layout.hex_cell_rect(origin, 3, 20.0);
        let c7 = layout.hex_cell_rect(origin, 7, 20.0);
        assert_eq!(span.left(), c3.left());
        assert_eq!(span.right(), c7.right());
    }

    #[test]
    fn hit_test_clamps_row_past_last_visible() {
        let cols = ColumnCount::new(16).unwrap();
        let layout = RowLayout::compute(10.0, 8, cols);
        let block = Rect::from_min_size(Pos2::ZERO, Vec2::new(layout.total_width, 60.0));
        // Pointer below the last row should clamp to last row (num_rows=3).
        let below = Pos2::new(layout.hex_start_x + 5.0, 1000.0);
        let hit = layout.hit_test(block, below, 20.0, 3).unwrap();
        assert_eq!(hit.row, 2);
    }
}