#include "TextRenderer.hpp"

#include <algorithm>
#include <cassert>
#include <chrono>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <limits>
#include <mutex>
#include <optional>
#include <string>
#include <string_view>
#include <unordered_map>
#include <utility>
#include <vector>

#include <fontconfig/fontconfig.h>

#include <raylib.h>
#include <rlgl.h>

#undef BLACK
#undef WHITE
#undef RED
#undef GREEN
#undef BLUE
#undef YELLOW
#undef MAGENTA

#include <ft2build.h>
#include FT_FREETYPE_H
#include FT_GLYPH_H
#include <hb-ft.h>
#include <hb.h>

#include <ext/import-font.h>
#include <msdfgen.h>

namespace {

constexpr int ATLAS_DIMENSION = 1024;
constexpr int ATLAS_PADDING = 2;
constexpr float DEFAULT_EM_SCALE = 48.0f;

constexpr float hb_to_em(hb_position_t value, unsigned upem)
{
	return static_cast<float>(value)
	    / (64.0f * static_cast<float>(upem ? upem : 1));
}

auto ft_library() -> FT_Library
{
	static FT_Library library = nullptr;
	static std::once_flag once;
	std::call_once(once, [] {
		if (FT_Init_FreeType(&library) != 0)
			library = nullptr;
		else
			std::atexit([] {
				if (library)
					FT_Done_FreeType(library);
			});
	});
	return library;
}

struct CodepointSpan {
	uint32_t codepoint {};
	usize start {};
	usize end {};
};

auto decode_utf8(std::string_view text) -> std::vector<CodepointSpan>
{
	std::vector<CodepointSpan> spans;
	usize i = 0;
	while (i < text.size()) {
		u8 const byte = static_cast<u8>(text[i]);
		usize const start = i;
		usize length = 1;
		uint32_t cp = 0xFFFD;
		if (byte < 0x80) {
			cp = byte;
		} else if ((byte & 0xE0) == 0xC0) {
			if (i + 1 < text.size()) {
				u8 const b1 = static_cast<u8>(text[i + 1]);
				if ((b1 & 0xC0) == 0x80) {
					uint32_t t = ((byte & 0x1F) << 6)
					    | (static_cast<uint32_t>(b1) & 0x3F);
					if (t >= 0x80) {
						cp = t;
						length = 2;
					}
				}
			}
		} else if ((byte & 0xF0) == 0xE0) {
			if (i + 2 < text.size()) {
				u8 const b1 = static_cast<u8>(text[i + 1]);
				u8 const b2 = static_cast<u8>(text[i + 2]);
				if ((b1 & 0xC0) == 0x80 && (b2 & 0xC0) == 0x80) {
					uint32_t t = ((byte & 0x0F) << 12)
					    | ((static_cast<uint32_t>(b1) & 0x3F) << 6)
					    | (static_cast<uint32_t>(b2) & 0x3F);
					if (t >= 0x800 && (t < 0xD800 || t > 0xDFFF)) {
						cp = t;
						length = 3;
					}
				}
			}
		} else if ((byte & 0xF8) == 0xF0) {
			if (i + 3 < text.size()) {
				u8 const b1 = static_cast<u8>(text[i + 1]);
				u8 const b2 = static_cast<u8>(text[i + 2]);
				u8 const b3 = static_cast<u8>(text[i + 3]);
				if ((b1 & 0xC0) == 0x80 && (b2 & 0xC0) == 0x80
				    && (b3 & 0xC0) == 0x80) {
					uint32_t t = ((byte & 0x07) << 18)
					    | ((static_cast<uint32_t>(b1) & 0x3F) << 12)
					    | ((static_cast<uint32_t>(b2) & 0x3F) << 6)
					    | (static_cast<uint32_t>(b3) & 0x3F);
					if (t >= 0x10000 && t <= 0x10FFFF) {
						cp = t;
						length = 4;
					}
				}
			}
		}

		spans.push_back(CodepointSpan {
		    .codepoint = cp,
		    .start = start,
		    .end = std::min(text.size(), start + length),
		});
		i += length;
	}
	return spans;
}

} // namespace

auto TextRenderer::flush_font(FontRuntime &rt, FontData &fd) -> void
{
	rt.glyph_cache.clear();
	fd.glyphs.clear();
	rt.pen_x = ATLAS_PADDING;
	rt.pen_y = ATLAS_PADDING;
	rt.row_height = 0;
	if (fd.atlas_img.data)
		ImageClearBackground(&fd.atlas_img, BLANK);
	if (fd.atlas.id != 0 && fd.atlas_img.data)
		UpdateTexture(fd.atlas, fd.atlas_img.data);
}

auto TextRenderer::allocate_region(FontRuntime &rt, FontData &fd, int width,
    int height) -> std::optional<std::pair<int, int>>
{
	(void)fd;
	int padded_w = width + ATLAS_PADDING;
	if (padded_w > rt.atlas_width || height + ATLAS_PADDING > rt.atlas_height)
		return std::nullopt;
	if (rt.pen_x + padded_w > rt.atlas_width) {
		rt.pen_x = ATLAS_PADDING;
		rt.pen_y += rt.row_height;
		rt.row_height = 0;
	}
	if (rt.pen_y + height + ATLAS_PADDING > rt.atlas_height)
		return std::nullopt;
	int x = rt.pen_x;
	int y = rt.pen_y;
	rt.pen_x += padded_w;
	rt.row_height = std::max(rt.row_height, height + ATLAS_PADDING);
	return std::pair { x, y };
}

auto TextRenderer::upload_region(FontData &fd, int dst_x, int dst_y, int width,
    int height, std::vector<Color> const &buffer) -> void
{
	Rectangle rec { static_cast<float>(dst_x), static_cast<float>(dst_y),
		static_cast<float>(width), static_cast<float>(height) };
	if (fd.atlas.id != 0)
		UpdateTextureRec(fd.atlas, rec, buffer.data());
	if (!fd.atlas_img.data)
		return;
	auto *pixels = static_cast<Color *>(fd.atlas_img.data);
	for (int row = 0; row < height; ++row) {
		auto *dst = pixels + (dst_y + row) * fd.atlas_img.width + dst_x;
		std::memcpy(dst, buffer.data() + row * width, sizeof(Color) * width);
	}
}

auto TextRenderer::generate_glyph(FontRuntime &rt, FontData &fd,
    u32 glyph_index) -> std::optional<GlyphCacheEntry>
{
	auto const gen_start = std::chrono::steady_clock::now();
	msdfgen::Shape shape;
	double advance_em = 0.0;
	msdfgen::GlyphIndex const index(glyph_index);
	if (!rt.msdf_font
	    || !msdfgen::loadGlyph(shape, rt.msdf_font, index,
	        msdfgen::FONT_SCALING_EM_NORMALIZED, &advance_em))
		return std::nullopt;
	shape.normalize();
	// FIXME: Figure out shader
	// msdfgen::edgeColoringInkTrap(shape, 3.0);
	auto bounds = shape.getBounds();
	float const width_em = static_cast<float>(bounds.r - bounds.l);
	float const height_em = static_cast<float>(bounds.t - bounds.b);
	double const scale = rt.em_scale;
	int bmp_w = std::max(
	    1, static_cast<int>(std::ceil(width_em * scale + 2.0 * rt.px_range)));
	int bmp_h = std::max(
	    1, static_cast<int>(std::ceil(height_em * scale + 2.0 * rt.px_range)));

	if (bmp_w + ATLAS_PADDING > rt.atlas_width
	    || bmp_h + ATLAS_PADDING > rt.atlas_height) {
		TraceLog(LOG_WARNING, "Glyph %u bitmap %dx%d exceeds atlas %dx%d",
		    glyph_index, bmp_w, bmp_h, rt.atlas_width, rt.atlas_height);
		GlyphCacheEntry too_large {};
		too_large.width = 0;
		too_large.height = 0;
		return too_large;
	}

	auto place = allocate_region(rt, fd, bmp_w, bmp_h);
	if (!place) {
		TraceLog(LOG_INFO, "Atlas full, flushing before glyph %u", glyph_index);
		flush_font(rt, fd);
		place = allocate_region(rt, fd, bmp_w, bmp_h);
		if (!place)
			return std::nullopt;
	}

	msdfgen::Bitmap<float, 3> msdf_bitmap(bmp_w, bmp_h);
	msdfgen::Vector2 scale_vec(scale, scale);
	double const inv_scale = 1.0 / scale;
	msdfgen::Vector2 translate(-bounds.l + rt.px_range * inv_scale,
	    -bounds.b + rt.px_range * inv_scale);
	msdfgen::generateMSDF(
	    msdf_bitmap, shape, rt.px_range, scale_vec, translate);

	std::vector<Color> buffer(static_cast<usize>(bmp_w) * bmp_h);
	// FIXME: Figure out shader
	// for (int y = 0; y < bmp_h; ++y) {
	//	int const dst_y = bmp_h - 1 - y;
	//	for (int x = 0; x < bmp_w; ++x) {
	//		float const *px = msdf_bitmap(x, y);
	//		auto const r = msdfgen::pixelFloatToByte(px[0]);
	//		auto const g = msdfgen::pixelFloatToByte(px[1]);
	//		auto const b = msdfgen::pixelFloatToByte(px[2]);
	//		buffer[static_cast<usize>(dst_y) * bmp_w + x]
	//		    = Color { r, g, b, 255 };
	//	}
	//}

	auto c1 { (int)std::round(msdf_bitmap(0, 0)[3]) };
	auto c4 { (int)std::round(msdf_bitmap(bmp_w - 1, bmp_h - 1)[3]) };

	auto sum_white = 0;
	auto sum_black = 0;
	for (int y = 0; y < bmp_h; ++y) {
		for (int x = 0; x < bmp_w; ++x) {
			float const *px = msdf_bitmap(x, y);
			auto const r = msdfgen::pixelFloatToByte(px[0]);
			if (r > 127) {
				sum_white++;
			} else {
				sum_black++;
			}
		}
	}
	bool flip { sum_white > sum_black && (float)bmp_w / (float)bmp_h > 0.6 };
	if (c1 == c4) {
		flip = false;
	}

	// This really isn't the most accurate thing in the world but should work
	// for now. Things like commas might be fucked.
	for (int y = 0; y < bmp_h; ++y) {
		int const dst_y = bmp_h - 1 - y;
		for (int x = 0; x < bmp_w; ++x) {
			float const *px = msdf_bitmap(x, y);
			auto const r = msdfgen::pixelFloatToByte(px[0]);
			if (flip) {
				buffer[static_cast<usize>(dst_y) * bmp_w + x] = Color { 255,
					255, 255, static_cast<unsigned char>(255 - r) };
			} else {
				buffer[static_cast<usize>(dst_y) * bmp_w + x]
				    = Color { 255, 255, 255, r };
			}
		}
	}

	upload_region(fd, place->first, place->second, bmp_w, bmp_h, buffer);

	GlyphCacheEntry entry;
	entry.atlas_x = place->first;
	entry.atlas_y = place->second;
	entry.width = bmp_w;
	entry.height = bmp_h;

	entry.glyph.advance = static_cast<float>(advance_em);
	entry.glyph.plane_bounds.left = static_cast<float>(bounds.l);
	entry.glyph.plane_bounds.right = static_cast<float>(bounds.r);
	entry.glyph.plane_bounds.top = static_cast<float>(bounds.t);
	entry.glyph.plane_bounds.bottom = static_cast<float>(bounds.b);
	entry.glyph.glyph_bounds.left = static_cast<float>(entry.atlas_x);
	entry.glyph.glyph_bounds.top = static_cast<float>(entry.atlas_y);
	entry.glyph.glyph_bounds.right
	    = static_cast<float>(entry.atlas_x + entry.width);
	entry.glyph.glyph_bounds.bottom
	    = static_cast<float>(entry.atlas_y + entry.height);

	auto const gen_end = std::chrono::steady_clock::now();
	auto const gen_ms
	    = std::chrono::duration<double, std::milli>(gen_end - gen_start)
	          .count();
	if (gen_ms > 2.0)
		TraceLog(LOG_INFO, "Generated glyph %u in %.2f ms (%dx%d texels)",
		    glyph_index, gen_ms, entry.width, entry.height);
	return entry;
}

auto TextRenderer::ensure_glyph(FontRuntime &rt, FontData &fd, u32 glyph_index,
    bool mark_usage) -> GlyphCacheEntry *
{
	auto it = rt.glyph_cache.find(glyph_index);
	if (it != rt.glyph_cache.end()) {
		if (mark_usage)
			it->second.stamp = rt.frame_stamp;
		return &it->second;
	}
	auto entry = generate_glyph(rt, fd, glyph_index);
	if (!entry)
		return nullptr;
	auto [inserted_it, ok]
	    = rt.glyph_cache.emplace(glyph_index, std::move(*entry));
	if (!ok)
		return nullptr;
	inserted_it->second.stamp
	    = mark_usage ? rt.frame_stamp : inserted_it->second.stamp;
	fd.glyphs[glyph_index] = inserted_it->second.glyph;
	return &inserted_it->second;
}

TextRenderer::TextRenderer()
{
	static char const msdf_vs_data[] {
#embed "base.vert"
		, 0 // cppcheck-suppress syntaxError
	};
	static char const msdf_fs_data[] {
#embed "msdf.frag"
		, 0 // cppcheck-suppress syntaxError
	};
	m_msdf_shader = LoadShaderFromMemory(msdf_vs_data, msdf_fs_data);
	assert(IsShaderValid(m_msdf_shader));
	m_px_range_uniform = GetShaderLocation(m_msdf_shader, "pxRange");
}

TextRenderer::~TextRenderer()
{
	for (usize i = 0; i < m_font_sets.size(); ++i) {
		FontHandle handle;
		handle.id = i;
		unload_font(handle);
	}
	// Not unloading the shader... I have no clue why, but there's some sort of
	// double free. I love C interop!!!!
}

auto TextRenderer::measure_text(FontHandle const font,
    std::string_view const text, int const size) -> Vector2
{
	usize const handle_id = font();
	if (handle_id >= m_font_sets.size())
		return Vector2 { 0.0f, 0.0f };
	auto const &font_set = m_font_sets[handle_id];
	if (font_set.font_indices.empty())
		return Vector2 { 0.0f, 0.0f };

	auto placements = shape_text(font, text);

	auto primary_runtime_index = font_set.font_indices.front();
	if (placements.empty()) {
		if (primary_runtime_index >= m_font_runtime.size()
		    || !m_font_runtime[primary_runtime_index])
			return Vector2 { 0.0f, 0.0f };
		auto const &rt_primary = *m_font_runtime[primary_runtime_index];
		float height_em = rt_primary.ascent - rt_primary.descent;
		return Vector2 { 0.0f, height_em * static_cast<float>(size) };
	}

	float advance_em = 0.0f;
	float min_x_em = 0.0f;
	float max_x_em = 0.0f;
	bool first = true;
	bool have_metrics = false;
	float max_ascent = 0.0f;
	float min_descent = 0.0f;

	for (auto const &placement : placements) {
		usize const runtime_index = placement.runtime_index;
		if (runtime_index >= m_font_runtime.size()
		    || !m_font_runtime[runtime_index])
			continue;
		auto &rt = *m_font_runtime[runtime_index];
		auto &fd = m_font_data[runtime_index];
		auto *entry = ensure_glyph(rt, fd, placement.glyph_index, false);
		if (!entry || entry->width == 0 || entry->height == 0)
			continue;
		float const x_offset_em = hb_to_em(placement.x_offset, rt.units_per_em);
		float const left
		    = advance_em + x_offset_em + entry->glyph.plane_bounds.left;
		float const right
		    = advance_em + x_offset_em + entry->glyph.plane_bounds.right;
		if (first) {
			min_x_em = left;
			max_x_em = right;
			first = false;
		} else {
			min_x_em = std::min(min_x_em, left);
			max_x_em = std::max(max_x_em, right);
		}
		if (!have_metrics) {
			max_ascent = rt.ascent;
			min_descent = rt.descent;
			have_metrics = true;
		} else {
			max_ascent = std::max(max_ascent, rt.ascent);
			min_descent = std::min(min_descent, rt.descent);
		}
		advance_em += hb_to_em(placement.x_advance, rt.units_per_em);
	}

	if (first) {
		if (primary_runtime_index >= m_font_runtime.size()
		    || !m_font_runtime[primary_runtime_index])
			return Vector2 { 0.0f, 0.0f };
		auto const &rt = *m_font_runtime[primary_runtime_index];
		float height_em = rt.ascent - rt.descent;
		return Vector2 { 0.0f, height_em * static_cast<float>(size) };
	}

	float width_em = std::max(max_x_em, advance_em) - min_x_em;
	float height_em = 0.0f;
	if (have_metrics) {
		height_em = max_ascent - min_descent;
	} else if (primary_runtime_index < m_font_runtime.size()
	    && m_font_runtime[primary_runtime_index]) {
		auto const &rt = *m_font_runtime[primary_runtime_index];
		height_em = rt.ascent - rt.descent;
	}

	return Vector2 { width_em * static_cast<float>(size),
		height_em * static_cast<float>(size) };
}

auto TextRenderer::draw_text(FontHandle const font, std::string_view const text,
    Vector2 const pos, int const size, Color const color) -> void
{
	auto const draw_start = std::chrono::steady_clock::now();
	int const pos_x = pos.x;
	int const pos_y = pos.y;
	usize const handle_id = font();
	if (handle_id >= m_font_sets.size())
		return;
	auto const &font_set = m_font_sets[handle_id];
	if (font_set.font_indices.empty())
		return;

	auto placements = shape_text(font, text);
	if (placements.empty())
		return;

	float const size_f = static_cast<float>(size);
	float pen_x_em = 0.0f;
	float pen_y_em = 0.0f;
	std::vector<usize> updated_stamp;
	updated_stamp.reserve(font_set.font_indices.size());

	for (auto const &placement : placements) {
		usize const runtime_index = placement.runtime_index;
		if (runtime_index >= m_font_runtime.size()
		    || !m_font_runtime[runtime_index])
			continue;
		auto &rt = *m_font_runtime[runtime_index];
		auto &fd = m_font_data[runtime_index];
		if (std::find(updated_stamp.begin(), updated_stamp.end(), runtime_index)
		    == updated_stamp.end()) {
			rt.frame_stamp++;
			updated_stamp.push_back(runtime_index);
		}

		auto *entry = ensure_glyph(rt, fd, placement.glyph_index, true);
		if (!entry || entry->width == 0 || entry->height == 0)
			continue;

		float const advance_em = hb_to_em(placement.x_advance, rt.units_per_em);
		float const x_offset_em = hb_to_em(placement.x_offset, rt.units_per_em);
		float const y_offset_em = hb_to_em(placement.y_offset, rt.units_per_em);
		float const x_base_em = pen_x_em + x_offset_em;
		float const y_base_em = pen_y_em + y_offset_em;
		float const scale_px = size_f / static_cast<float>(rt.em_scale);
		float const margin_px = static_cast<float>(rt.px_range) * scale_px;
		float const dest_x = pos_x
		    + (x_base_em + entry->glyph.plane_bounds.left) * size_f - margin_px;
		float const dest_y = pos_y
		    - (y_base_em + entry->glyph.plane_bounds.top) * size_f - margin_px;
		float const dest_w = static_cast<float>(entry->width) * scale_px;
		float const dest_h = static_cast<float>(entry->height) * scale_px;

		Rectangle source {
			entry->glyph.glyph_bounds.left,
			entry->glyph.glyph_bounds.top,
			static_cast<float>(entry->width),
			static_cast<float>(entry->height),
		};
		Rectangle dest { dest_x, dest_y, dest_w, dest_h };
		DrawTexturePro(
		    fd.atlas, source, dest, Vector2 { 0.0f, 0.0f }, 0.0f, color);

		pen_x_em += advance_em;
		pen_y_em += hb_to_em(placement.y_advance, rt.units_per_em);
	}

	auto const draw_end = std::chrono::steady_clock::now();
	auto const draw_ms
	    = std::chrono::duration<double, std::milli>(draw_end - draw_start)
	          .count();
	if (draw_ms > 5.0)
		TraceLog(LOG_INFO, "draw_text took %.2f ms for %zu glyphs", draw_ms,
		    placements.size());
}

auto TextRenderer::load_single_font(std::filesystem::path const &path)
    -> std::optional<usize>
{
	FT_Library const ft = ft_library();
	if (!ft)
		return std::nullopt;

	FT_Face face = nullptr;
	if (FT_New_Face(ft, path.string().c_str(), 0, &face) != 0)
		return std::nullopt;
	if (FT_Select_Charmap(face, FT_ENCODING_UNICODE) != 0) {
		FT_Done_Face(face);
		return std::nullopt;
	}

	auto runtime = std::make_unique<FontRuntime>();
	runtime->face = face;
	runtime->atlas_width = ATLAS_DIMENSION;
	runtime->atlas_height = ATLAS_DIMENSION;
	runtime->pen_x = ATLAS_PADDING;
	runtime->pen_y = ATLAS_PADDING;
	runtime->row_height = 0;
	runtime->px_range = 0.05; // kDefaultPxRange;
	runtime->em_scale = DEFAULT_EM_SCALE;
	runtime->frame_stamp = 0;
	runtime->units_per_em
	    = static_cast<unsigned>(face->units_per_EM ? face->units_per_EM : 2048);
	runtime->ascent = static_cast<float>(face->ascender)
	    / (64.0f * static_cast<float>(runtime->units_per_em));
	runtime->descent = static_cast<float>(face->descender)
	    / (64.0f * static_cast<float>(runtime->units_per_em));
	float line_height = static_cast<float>(face->height)
	    / (64.0f * static_cast<float>(runtime->units_per_em));
	float adv_height = runtime->ascent - runtime->descent;
	runtime->line_gap = std::max(0.0f, line_height - adv_height);

	runtime->hb_face = hb_ft_face_create_referenced(face);
	if (!runtime->hb_face) {
		FT_Done_Face(face);
		return std::nullopt;
	}
	runtime->hb_font = hb_ft_font_create_referenced(face);
	if (!runtime->hb_font) {
		hb_face_destroy(runtime->hb_face);
		FT_Done_Face(face);
		return std::nullopt;
	}
	hb_font_set_scale(runtime->hb_font,
	    static_cast<int>(runtime->units_per_em) << 6,
	    static_cast<int>(runtime->units_per_em) << 6);
	hb_ft_font_set_funcs(runtime->hb_font);

	runtime->msdf_font = msdfgen::adoptFreetypeFont(face);
	if (!runtime->msdf_font) {
		hb_font_destroy(runtime->hb_font);
		hb_face_destroy(runtime->hb_face);
		FT_Done_Face(face);
		return std::nullopt;
	}

	FontData font_data {};
	font_data.font_path = path;
	font_data.atlas_img
	    = GenImageColor(runtime->atlas_width, runtime->atlas_height, BLANK);
	if (!font_data.atlas_img.data) {
		msdfgen::destroyFont(runtime->msdf_font);
		runtime->msdf_font = nullptr;
		hb_font_destroy(runtime->hb_font);
		hb_face_destroy(runtime->hb_face);
		return std::nullopt;
	}
	font_data.atlas = LoadTextureFromImage(font_data.atlas_img);
	if (font_data.atlas.id == 0) {
		UnloadImage(font_data.atlas_img);
		msdfgen::destroyFont(runtime->msdf_font);
		runtime->msdf_font = nullptr;
		hb_font_destroy(runtime->hb_font);
		hb_face_destroy(runtime->hb_face);
		return std::nullopt;
	}
	SetTextureFilter(font_data.atlas, TEXTURE_FILTER_BILINEAR);
	SetTextureWrap(font_data.atlas, TEXTURE_WRAP_CLAMP);
	flush_font(*runtime, font_data);

	m_font_data.emplace_back(std::move(font_data));
	m_font_runtime.emplace_back(std::move(runtime));
	return m_font_data.size() - 1;
}

auto TextRenderer::load_font(std::filesystem::path const &path,
    std::span<std::filesystem::path const> fallback_fonts)
    -> std::optional<FontHandle>
{
	auto primary_index = load_single_font(path);
	if (!primary_index)
		return std::nullopt;

	FontSet set;
	set.font_indices.push_back(*primary_index);

	for (auto const &fallback_path : fallback_fonts) {
		auto fallback_index = load_single_font(fallback_path);
		if (!fallback_index) {
			TraceLog(LOG_WARNING, "Failed to load fallback font: %s",
			    fallback_path.string().c_str());
			continue;
		}
		set.font_indices.push_back(*fallback_index);
	}

	m_font_sets.emplace_back(std::move(set));
	FontHandle handle;
	handle.id = m_font_sets.size() - 1;
	return handle;
}

auto TextRenderer::shape_text(FontHandle const font,
    std::string_view const text) -> std::vector<GlyphPlacement>
{
	std::vector<GlyphPlacement> shaped;
	if (text.empty())
		return shaped;

	usize const handle_id = font();
	if (handle_id >= m_font_sets.size())
		return shaped;
	auto const &font_set = m_font_sets[handle_id];
	if (font_set.font_indices.empty())
		return shaped;

	auto codepoints = decode_utf8(text);
	if (codepoints.empty())
		return shaped;

	constexpr usize kNoFont = std::numeric_limits<usize>::max();
	std::vector<usize> selections(codepoints.size(), kNoFont);
	for (usize i = 0; i < codepoints.size(); ++i) {
		bool matched = false;
		for (usize candidate = 0; candidate < font_set.font_indices.size();
		    ++candidate) {
			usize runtime_index = font_set.font_indices[candidate];
			if (runtime_index >= m_font_runtime.size())
				continue;
			auto const &runtime_ptr = m_font_runtime[runtime_index];
			if (!runtime_ptr || !runtime_ptr->face)
				continue;
			FT_UInt glyph
			    = FT_Get_Char_Index(runtime_ptr->face, codepoints[i].codepoint);
			if (glyph != 0) {
				selections[i] = candidate;
				matched = true;
				break;
			}
		}
		if (!matched)
			selections[i] = kNoFont;
	}

	usize idx = 0;
	while (idx < codepoints.size()) {
		usize font_choice = selections[idx];
		if (font_choice == kNoFont) {
			++idx;
			continue;
		}
		if (font_choice >= font_set.font_indices.size())
			font_choice = 0;
		usize runtime_index = font_set.font_indices[font_choice];
		if (runtime_index >= m_font_runtime.size()
		    || !m_font_runtime[runtime_index]
		    || !m_font_runtime[runtime_index]->hb_font) {
			++idx;
			continue;
		}

		usize segment_start = codepoints[idx].start;
		usize segment_end = codepoints[idx].end;
		usize end_idx = idx + 1;
		while (
		    end_idx < codepoints.size() && selections[end_idx] == font_choice) {
			segment_end = codepoints[end_idx].end;
			++end_idx;
		}

		if (segment_end <= segment_start) {
			idx = end_idx;
			continue;
		}

		std::string_view segment
		    = text.substr(segment_start, segment_end - segment_start);
		if (segment.empty()) {
			idx = end_idx;
			continue;
		}

		hb_buffer_t *buffer = hb_buffer_create();
		hb_buffer_add_utf8(buffer, segment.data(),
		    static_cast<int>(segment.size()), 0,
		    static_cast<int>(segment.size()));
		hb_buffer_guess_segment_properties(buffer);
		hb_shape(m_font_runtime[runtime_index]->hb_font, buffer, nullptr, 0);

		unsigned length = hb_buffer_get_length(buffer);
		auto *infos = hb_buffer_get_glyph_infos(buffer, nullptr);
		auto *positions = hb_buffer_get_glyph_positions(buffer, nullptr);
		for (unsigned i = 0; i < length; ++i) {
			GlyphPlacement placement;
			placement.runtime_index = runtime_index;
			placement.glyph_index = infos[i].codepoint;
			placement.x_advance = positions[i].x_advance;
			placement.y_advance = positions[i].y_advance;
			placement.x_offset = positions[i].x_offset;
			placement.y_offset = positions[i].y_offset;
			shaped.emplace_back(placement);
		}
		hb_buffer_destroy(buffer);
		idx = end_idx;
	}

	return shaped;
}

auto TextRenderer::unload_font(FontHandle const font) -> void
{
	usize const handle_id = font();
	if (handle_id >= m_font_sets.size())
		return;

	auto &font_set = m_font_sets[handle_id];
	for (usize runtime_index : font_set.font_indices) {
		if (runtime_index >= m_font_runtime.size())
			continue;

		if (auto &runtime_ptr = m_font_runtime[runtime_index]) {
			auto &rt = *runtime_ptr;
			rt.glyph_cache.clear();
			// No freeing here because they are already cleaned up somewhere...
			// idk. fml.
			rt.face = nullptr;
		}
		m_font_runtime[runtime_index].reset();

		if (runtime_index < m_font_data.size()) {
			auto &fd = m_font_data[runtime_index];
			if (fd.atlas.id != 0)
				UnloadTexture(fd.atlas);
			if (fd.atlas_img.data)
				UnloadImage(fd.atlas_img);
			fd.atlas = Texture2D {};
			fd.atlas_img = Image {};
			fd.glyphs.clear();
		}
	}
	font_set.font_indices.clear();
}

auto find_font_path(std::string_view path)
    -> std::optional<std::filesystem::path>
{
	static std::once_flag fc_once;
	std::call_once(fc_once, []() {
		if (FcInit())
			std::atexit([] { FcFini(); });
	});

	static std::mutex m;
	static std::unordered_map<std::string, std::optional<std::string>> cache;

	std::string const key(path);

	{
		std::scoped_lock lock(m);
		if (auto it = cache.find(key); it != cache.end())
			return it->second;
	}

	FcPattern *pattern
	    = FcNameParse(reinterpret_cast<FcChar8 const *>(key.c_str()));
	if (!pattern) {
		std::scoped_lock lock(m);
		return cache[key] = std::nullopt;
	}

	FcConfigSubstitute(nullptr, pattern, FcMatchPattern);
	FcDefaultSubstitute(pattern);

	FcResult result;
	FcPattern *font = FcFontMatch(nullptr, pattern, &result);

	std::optional<std::string> final_path;
	if (font) {
		FcChar8 *file;
		if (FcPatternGetString(font, FC_FILE, 0, &file) == FcResultMatch)
			final_path = reinterpret_cast<char *>(file);
		FcPatternDestroy(font);
	}

	FcPatternDestroy(pattern);

	{
		std::scoped_lock lock(m);
		cache[key] = final_path;
	}
	return final_path;
}