#include <psemek/ui/label.hpp>

#include <stdexcept>
#include <cctype>

namespace psemek::ui
{

	label::label(std::string text)
		: text_(std::move(text))
	{}

	void label::set_text(std::string text)
	{
		text_ = std::move(text);
		on_state_changed();
	}

	void label::set_halign(halignment value)
	{
		halign_ = value;
		on_state_changed();
	}

	void label::set_valign(valignment value)
	{
		valign_ = value;
		on_state_changed();
	}

	void label::set_multiline(multiline_mode value)
	{
		multiline_ = value;
		on_state_changed();
	}

	void label::set_overflow(overflow_mode value)
	{
		overflow_ = value;
		on_state_changed();
	}

	void label::reshape(geom::box<float, 2> const & bbox)
	{
		shape_.box = bbox;
		cached_state_.reset();
	}

	geom::box<float, 2> label::size_constraints() const
	{
		static float const inf = std::numeric_limits<float>::infinity();

		auto state = cached_state_for({{{0.f, inf}, {0.f, inf}}});

		return {{{state.size[0], inf}, {state.size[1], inf}}};
	}

	void label::draw(painter & p) const
	{
		if (!cached_state_)
			update_cached_state();

		if (!cached_state_->font) return;

		auto st = merged_own_style();
		if (!st) return;

		if (st->text_shadow_offset != geom::vector{0, 0})
			for (auto & g : cached_state_->glyphs)
				p.draw_glyph(*(cached_state_->font), g.character, g.position + geom::cast<float>(*st->text_shadow_offset), *st->shadow_color);

		for (auto & g : cached_state_->glyphs)
			p.draw_glyph(*(cached_state_->font), g.character, g.position, *st->text_color);
	}

	void label::on_state_changed()
	{
		cached_state_.reset();
		post_reshape();
	}

	static bool is_newline(char32_t c)
	{
		return (c == '\n') || (c == '\r');
	}

	void label::update_cached_state() const
	{
		cached_state_ = cached_state_for(shape_.box);
	}

	label::cached_state label::cached_state_for(geom::box<float, 2> const & bbox) const
	{
		auto state = cached_state{};

		if (text_.empty()) return state;

		auto st = merged_own_style();
		if (!st) return state;
		if (!st->font) return state;

		state.font = st->font.get();

		shape_options opts;
		opts.scale = *st->text_scale;
		auto glyphs = st->font->shape(text_, opts);

		geom::box<float, 2> raw_bbox;
		for (auto const & g : glyphs)
			raw_bbox |= g.position;

		std::size_t max_lines;

		switch (multiline_)
		{
		case multiline_mode::none:
			max_lines = 1;
			break;
		case multiline_mode::minimize_lines:
			max_lines = std::isfinite(bbox[1].length())
				? std::max<std::size_t>(1, std::floor(bbox[1].length() / st->font->size()[1] / (*st->text_scale)))
				: std::numeric_limits<std::size_t>::max();
			break;
		case multiline_mode::minimize_area:
			throw std::runtime_error("multiline_mode::minimize_area is not supported yet");
		}

		std::vector<std::pair<std::size_t, std::size_t>> lines;

		std::size_t current_glyph = 0;

		for (std::size_t line = 0; line < max_lines; ++line)
		{
			if (line != 0)
			{
				while (current_glyph < glyphs.size() && std::isspace(glyphs[current_glyph].character))
					++current_glyph;
			}

			std::size_t line_begin = current_glyph;
			std::size_t line_end = line_begin;

			geom::interval<float> x_range;
			while (line_end < glyphs.size())
			{
				if (is_newline(glyphs[line_end].character))
					break;

				x_range |= glyphs[line_end].position[0];

				if (x_range.length() > bbox[0].length())
					break;

				++line_end;
			}

			if (line_end < glyphs.size())
			{
				std::size_t space_pos = line_end;
				while (space_pos > line_begin && !std::isspace(glyphs[space_pos].character))
					--space_pos;

				if (space_pos > line_begin)
					line_end = space_pos;
			}

			if (line + 1 == max_lines && line_end < glyphs.size())
			{
				switch (overflow_)
				{
				case overflow_mode::ignore:
					line_end = glyphs.size();
					break;
				case overflow_mode::drop:
					glyphs.erase(glyphs.begin() + line_end, glyphs.end());
					break;
				case overflow_mode::ellipsis:
					{
						std::size_t el_start = std::max<std::size_t>(3, line_end) - 3;

						float x_offset = 0.f;
						if (el_start > 0)
							x_offset = glyphs[el_start - 1].position[0].max;

						char const el_str[] = "...";
						auto els = st->font->shape(el_str, opts);
						for (std::size_t i = el_start; i < line_end; ++i)
						{
							glyphs[i] = els[i - el_start];
							glyphs[i].position[0] += x_offset;
						}

						glyphs.erase(glyphs.begin() + line_end, glyphs.end());
					}
					break;
				}
			}

			current_glyph = line_end;
			lines.push_back({line_begin, line_end});
			if (line_end == glyphs.size())
				break;
		}

		float max_line_size = 0.f;

		for (std::size_t l = 0; l < lines.size(); ++l)
		{
			geom::interval<float> x_range;
			for (std::size_t i = lines[l].first; i < lines[l].second; ++i)
				x_range |= glyphs[i].position[0];

			max_line_size = std::max(max_line_size, x_range.length());

			geom::vector<float, 2> offset;

			switch (halign_)
			{
			case halignment::left:
				offset[0] = bbox[0].min - x_range.min;
				break;
			case halignment::center:
				offset[0] = bbox[0].center() - x_range.length() / 2.f - x_range.min;
				break;
			case halignment::right:
				offset[0] = bbox[0].max - x_range.length() - x_range.min;
				break;
			}

			switch (valign_)
			{
			case valignment::top:
				offset[1] = bbox[1].min + l * (*st->text_scale) * st->font->size()[1];
				break;
			case valignment::center:
				offset[1] = bbox[1].center() + (l - lines.size() / 2.f) * (*st->text_scale) * st->font->size()[1];
				break;
			case valignment::bottom:
				offset[1] = bbox[1].max + (l - lines.size() * 1.f) * (*st->text_scale) * st->font->size()[1];
				break;
			}

			for (std::size_t i = lines[l].first; i < lines[l].second; ++i)
				glyphs[i].position += offset;
		}

		state.glyphs = std::move(glyphs);
		state.size[0] = max_line_size;
		state.size[1] = lines.size() * (*st->text_scale) * st->font->size()[1];

		return state;
	}

}