twrite-gpui 0.9.0

use gpui::{Pixels, Point, TextRun, Window, point, px};
use twrite_core::Selection;

use crate::canvas::{RunFonts, build_line_text_runs};

use super::{Editor, VisibleLineLayout};

/// Finds the visible line containing vertical position `y` via binary search.
///
/// `lines` is sorted by `top` (constructed in paint order in prepaint).
pub(crate) fn find_visible_line(
    lines: &[VisibleLineLayout],
    y: Pixels,
) -> Option<&VisibleLineLayout> {
    let idx = lines.partition_point(|l| l.top <= y);
    let line = lines.get(idx.checked_sub(1)?)?;
    (y < line.bottom).then_some(line)
}

impl Editor {
    /// Scrolls the viewport upward by a given number of lines.
    pub fn scroll_up(&mut self, count: usize) {
        self.scroll_row = self.scroll_row.saturating_sub(count);
    }

    /// Scrolls the viewport downward by a given number of lines.
    pub fn scroll_down(&mut self, count: usize) {
        let total_lines = self.buffer.len_lines();
        self.scroll_row = (self.scroll_row + count).min(total_lines.saturating_sub(1));
    }

    /// Moves the cursor to `new_offset`, expanding or creating a selection if `select` is true.
    pub fn move_cursor_to(&mut self, new_offset: usize, select: bool) {
        if select {
            let anchor = self
                .selection
                .map(|s| s.anchor)
                .unwrap_or_else(|| self.buffer.cursor_offset());
            self.buffer.set_cursor_offset(new_offset);
            if anchor != new_offset {
                self.selection = Some(Selection::range(anchor, new_offset));
            } else {
                self.selection = None;
            }
        } else {
            self.buffer.set_cursor_offset(new_offset);
            self.selection = None;
        }
    }

    /// Scrolls the viewport so that the cursor is visible.
    ///
    /// Ensures a 1-line margin above and below the cursor when possible.
    pub fn scroll_to_cursor(&mut self, window: Option<&Window>) {
        let total_lines = self.buffer.len_lines();
        if total_lines == 0 {
            self.scroll_row = 0;
            return;
        }

        let cursor_row = self
            .buffer
            .cursor_point()
            .row
            .min(total_lines.saturating_sub(1));

        let margin_lines = 1;
        if cursor_row < self.scroll_row + margin_lines {
            self.scroll_row = cursor_row.saturating_sub(margin_lines);
            return;
        }

        let bounds = match self.last_bounds {
            Some(b) => b,
            None => return,
        };

        let viewport_height = bounds.size.height;
        if viewport_height <= px(0.0) {
            return;
        }

        let line_height = self.config.line_height;
        let margin = line_height * margin_lines as f32;

        if self.config.line_wrap
            && let Some(win) = window
        {
            let gutter_width = if self.config.line_numbers {
                px(48.0)
            } else {
                px(0.0)
            };
            let wrap_width = Some((bounds.size.width - gutter_width - px(24.0)).max(px(50.0)));
            let font = self.resolved_base_font(&win.text_style().font());

            let get_row_visual_lines = |row: usize| -> usize {
                let raw_line = self.buffer.line_to_string(row);
                let line_text = raw_line.trim_end_matches(['\r', '\n']);
                if line_text.is_empty() {
                    return 1;
                }
                let wraps = self
                    .highlighter
                    .as_deref()
                    .map(|h| h.should_wrap_line(&self.buffer, row))
                    .unwrap_or(true);
                if !wraps {
                    return 1;
                }
                let runs = [TextRun {
                    len: line_text.len(),
                    font: font.clone(),
                    color: self.theme.foreground,
                    background_color: None,
                    underline: None,
                    strikethrough: None,
                }];
                win.text_system()
                    .shape_text(
                        line_text.to_string().into(),
                        self.config.font_size,
                        &runs,
                        wrap_width,
                        None,
                    )
                    .ok()
                    .and_then(|mut l| l.pop())
                    .map(|l| l.wrap_boundaries.len() + 1)
                    .unwrap_or(1)
            };

            let mut accumulated = line_height * get_row_visual_lines(cursor_row) as f32;
            let mut new_scroll_row = cursor_row;

            while new_scroll_row > 0 {
                let prev_lines = get_row_visual_lines(new_scroll_row - 1);
                let prev_height = line_height * prev_lines as f32;
                if accumulated + prev_height + margin > viewport_height {
                    break;
                }
                accumulated += prev_height;
                new_scroll_row -= 1;
            }

            if new_scroll_row > self.scroll_row {
                self.scroll_row = new_scroll_row;
            }
        } else {
            let visible_lines = (viewport_height / line_height).floor() as usize;
            let effective_visible = visible_lines.saturating_sub(margin_lines).max(1);

            if cursor_row >= self.scroll_row + effective_visible {
                self.scroll_row = cursor_row.saturating_sub(effective_visible.saturating_sub(1));
            }
        }
    }

    /// Calculates the byte offset in the text buffer corresponding to a window pixel position.
    ///
    /// Shares [`crate::layout_cache::LayoutCache`] inputs with prepaint: the highlight/conceal work
    /// for the target row is a cache hit unless the buffer changed since paint.
    pub fn offset_for_position(&mut self, pos: Point<Pixels>, window: &Window) -> usize {
        let bounds = match self.last_bounds {
            Some(b) => b,
            None => return self.buffer.cursor_offset(),
        };

        let total_lines = self.buffer.len_lines();
        if total_lines == 0 {
            return 0;
        }

        if !self.visible_lines.is_empty() {
            if pos.y < self.visible_lines[0].top {
                return self.visible_lines[0].line_start_byte;
            }

            let last = self.visible_lines.last().unwrap();
            if pos.y >= last.bottom {
                return (last.line_start_byte + last.line_len_bytes).min(self.buffer.len_bytes());
            }

            let target_line = match find_visible_line(&self.visible_lines, pos.y) {
                Some(l) => l,
                None => last,
            };

            let row = target_line.row;
            let line_start_byte = target_line.line_start_byte;
            let task_state = target_line.task_state;
            let text_origin_x = target_line.text_origin_x;
            let line_top = target_line.top;
            let line_height = target_line.line_height;
            let raw_line = self.buffer.line_to_string(row);
            let line_text = raw_line.trim_end_matches(['\r', '\n']);

            if line_text.is_empty() || pos.x <= text_origin_x {
                return line_start_byte;
            }

            let cursor_row = self.buffer.cursor_point().row;
            let highlighter_rev = self.highlighter_rev;
            let host_font = window.text_style().font();
            let font = self.resolved_base_font(&host_font);
            let code_font = self.resolved_code_font(&host_font);
            let cached = self.layout_cache.cached_input(
                &self.buffer,
                self.highlighter.as_deref(),
                highlighter_rev,
                cursor_row,
                row,
                line_text,
            );
            let concealed = &cached.concealed;

            let is_checked_task =
                task_state == Some(true) && line_text.len() != concealed.display_text.len();

            let fonts = RunFonts {
                base: &font,
                code: &code_font,
            };
            let runs = build_line_text_runs(
                &concealed.display_text,
                &concealed.spans,
                None,
                &fonts,
                &self.theme,
                false,
                is_checked_task,
            );

            let wrap_width = if self.config.line_wrap && cached.allow_wrap {
                let available = bounds.size.width - (text_origin_x - bounds.left()) - px(12.0);
                Some(available.max(px(50.0)))
            } else {
                None
            };

            let text_line = window
                .text_system()
                .shape_text(
                    concealed.display_text.clone().into(),
                    self.config.font_size,
                    &runs,
                    wrap_width,
                    None,
                )
                .ok()
                .and_then(|mut l| l.pop())
                .unwrap_or_default();

            let line_rel_y = (pos.y - line_top).max(px(0.0));
            let line_rel_x = (pos.x - text_origin_x).max(px(0.0));
            let rel_pos = point(line_rel_x, line_rel_y);

            let col_display = text_line
                .closest_index_for_position(rel_pos, line_height)
                .unwrap_or_else(|idx| idx);

            let col_src = concealed.display_to_source(col_display);
            return line_start_byte + col_src.min(line_text.len());
        }

        0
    }

    /// Returns the window pixel coordinates (X, Y) at the bottom of the active cursor.
    ///
    /// This value is automatically computed and cached during each canvas render pass.
    /// Returns `None` if the editor has not yet been rendered, or if the cursor is scrolled
    /// outside the visible viewport.
    pub fn cursor_pixel_position(&self) -> Option<Point<Pixels>> {
        self.last_cursor_pixel
    }

    /// Returns the target URL if `pos` is over a hyperlink.
    pub fn link_at_position(&self, pos: Point<Pixels>) -> Option<String> {
        let bounds = self.last_bounds?;
        if !bounds.contains(&pos) {
            return None;
        }

        if let Some(line) = find_visible_line(&self.visible_lines, pos.y) {
            for link in &line.links {
                if link.bounds.contains(&pos) {
                    return Some(link.url.clone());
                }
            }
        }

        None
    }

    pub(crate) fn is_position_over_task_checkbox(
        &self,
        pos: Point<Pixels>,
        _window: &Window,
    ) -> bool {
        let bounds = match self.last_bounds {
            Some(b) => b,
            None => return false,
        };

        if !bounds.contains(&pos) {
            return false;
        }

        if let Some(line) = find_visible_line(&self.visible_lines, pos.y)
            && line.is_task_checkbox
        {
            return pos.x >= line.checkbox_box_x && pos.x <= line.checkbox_box_x + px(22.0);
        }

        false
    }
}