text_context.rs

use super::{Font, FontCache, TypesettingConfig};
use core::cell::RefCell;
use core_types::table::Table;
use glam::DVec2;
use parley::fontique::{Blob, FamilyId, FontInfo};
use parley::{AlignmentOptions, FontContext, Layout, LayoutContext, LineHeight, PositionedLayoutItem, StyleProperty};
use std::collections::HashMap;
use vector_types::Vector;

use super::path_builder::PathBuilder;

thread_local! {
	static THREAD_TEXT: RefCell<TextContext> = RefCell::new(TextContext::default());
}

/// Unified thread-local text processing context that combines font and layout management
/// for efficient text rendering operations.
#[derive(Default)]
pub struct TextContext {
	font_context: FontContext,
	layout_context: LayoutContext<()>,
	/// Cached font metadata for performance optimization
	font_info_cache: HashMap<Font, (FamilyId, FontInfo)>,
}

impl TextContext {
	/// Access the thread-local TextContext instance for text processing operations
	pub fn with_thread_local<F, R>(f: F) -> R
	where
		F: FnOnce(&mut TextContext) -> R,
	{
		THREAD_TEXT.with_borrow_mut(f)
	}

	/// Resolve a font and return its data as a Blob if available
	fn resolve_font_data<'a>(&self, font: &'a Font, font_cache: &'a FontCache) -> Option<(Blob<u8>, &'a Font)> {
		font_cache.get_blob(font)
	}

	/// Get or cache font information for a given font
	fn get_font_info(&mut self, font: &Font, font_data: &Blob<u8>) -> Option<(String, FontInfo)> {
		// Check if we already have the font info cached
		if let Some((family_id, font_info)) = self.font_info_cache.get(font)
			&& let Some(family_name) = self.font_context.collection.family_name(*family_id)
		{
			return Some((family_name.to_string(), font_info.clone()));
		}

		// Register the font and cache the info
		let families = self.font_context.collection.register_fonts(font_data.clone(), None);

		families.first().and_then(|(family_id, fonts_info)| {
			fonts_info.first().and_then(|font_info| {
				self.font_context.collection.family_name(*family_id).map(|family_name| {
					// Cache the font info for future use
					self.font_info_cache.insert(font.clone(), (*family_id, font_info.clone()));
					(family_name.to_string(), font_info.clone())
				})
			})
		})
	}

	/// Create a text layout using the specified font and typesetting configuration
	fn layout_text(&mut self, text: &str, font: &Font, font_cache: &FontCache, typesetting: TypesettingConfig) -> Option<Layout<()>> {
		// Note that the actual_font may not be the desired font if that font is not yet loaded.
		// It is important not to cache the default font under the name of another font.
		let (font_data, actual_font) = self.resolve_font_data(font, font_cache)?;
		let (font_family, font_info) = self.get_font_info(actual_font, &font_data)?;

		const DISPLAY_SCALE: f32 = 1.;
		let mut builder = self.layout_context.ranged_builder(&mut self.font_context, text, DISPLAY_SCALE, false);

		builder.push_default(StyleProperty::FontSize(typesetting.font_size as f32));
		builder.push_default(StyleProperty::LetterSpacing(typesetting.character_spacing as f32));
		builder.push_default(StyleProperty::FontStack(parley::FontStack::Single(parley::FontFamily::Named(std::borrow::Cow::Owned(font_family)))));
		builder.push_default(StyleProperty::FontWeight(font_info.weight()));
		builder.push_default(StyleProperty::FontStyle(font_info.style()));
		builder.push_default(StyleProperty::FontWidth(font_info.width()));
		builder.push_default(LineHeight::FontSizeRelative(typesetting.line_height_ratio as f32));

		let mut layout: Layout<()> = builder.build(text);

		layout.break_all_lines(typesetting.max_width.map(|mw| mw as f32));
		layout.align(typesetting.max_width.map(|max_w| max_w as f32), typesetting.align.into(), AlignmentOptions::default());

		Some(layout)
	}

	/// Convert text to vector paths using the specified font and typesetting configuration
	pub fn to_path<Upstream: Default + 'static>(&mut self, text: &str, font: &Font, font_cache: &FontCache, typesetting: TypesettingConfig, per_glyph_instances: bool) -> Table<Vector<Upstream>> {
		let Some(layout) = self.layout_text(text, font, font_cache, typesetting) else {
			return Table::new_from_element(Vector::default());
		};

		let alignment_width = typesetting.max_width.map(|w| w as f32).unwrap_or_else(|| layout.full_width());
		let last_line_correction = typesetting.align.last_line_correction();

		let mut path_builder = PathBuilder::new(per_glyph_instances, layout.scale() as f64);

		for line in layout.lines() {
			let range = line.text_range();
			let is_last_para_line = range.end == text.len() || text.get(range.clone()).map(|s| s.ends_with('\n')).unwrap_or(false) || text.as_bytes().get(range.end) == Some(&b'\n');

			let (x_offset, space_extra) = if let (true, Some(correction)) = (is_last_para_line, last_line_correction) {
				let metrics = line.metrics();
				let content_advance = metrics.advance - metrics.trailing_whitespace;
				let free_space = alignment_width - content_advance;

				match correction {
					parley::Alignment::Center => (free_space as f64 * 0.5, 0_f32),
					parley::Alignment::Right => (free_space as f64, 0_f32),
					parley::Alignment::Justify => {
						let line_text = text.get(range.clone()).unwrap_or("");
						let trailing_len = line_text.len() - line_text.trim_end().len();
						let visible_end_index = range.end - trailing_len;

						let space_count: usize = line
							.runs()
							.map(|run| run.clusters().filter(|c| c.is_space_or_nbsp() && c.text_range().start < visible_end_index).count())
							.sum();
						let extra = if space_count > 0 { free_space / space_count as f32 } else { 0. };
						(0_f64, extra)
					}
					_ => (0_f64, 0_f32),
				}
			} else {
				(0_f64, 0_f32)
			};

			for item in line.items() {
				if let PositionedLayoutItem::GlyphRun(glyph_run) = item
					&& typesetting.max_height.filter(|&max_height| glyph_run.baseline() > max_height as f32).is_none()
				{
					path_builder.render_glyph_run(&glyph_run, typesetting.tilt, per_glyph_instances, x_offset, space_extra);
				}
			}
		}

		path_builder.finalize()
	}

	/// Calculate the bounding box of text using the specified font and typesetting configuration
	pub fn bounding_box(&mut self, text: &str, font: &Font, font_cache: &FontCache, typesetting: TypesettingConfig, for_clipping_test: bool) -> DVec2 {
		let Some(layout) = self.layout_text(text, font, font_cache, typesetting) else {
			return DVec2::ZERO;
		};

		let layout_width = layout.full_width() as f64;
		let layout_height = layout.height() as f64;

		if for_clipping_test {
			return DVec2::new(layout_width, layout_height);
		}

		let width = typesetting.max_width.unwrap_or(layout_width);
		let height = typesetting.max_height.unwrap_or(layout_height);

		DVec2::new(width, height)
	}

	/// Check if text lines are being clipped due to height constraints
	pub fn lines_clipping(&mut self, text: &str, font: &Font, font_cache: &FontCache, typesetting: TypesettingConfig) -> bool {
		let Some(max_height) = typesetting.max_height else { return false };
		let bounds = self.bounding_box(text, font, font_cache, typesetting, true);
		max_height < bounds.y
	}
}