#include "curvesarea.h"

namespace {

	struct DrawSegment {

	private:

		const Context &context;

		const Segment &segment;

		const Real width;

		const Real precision_sqr;

		const int max_level = 16;

		int level;

		Vector p0;

		Real l0;

		Vector func(const Real &l)

			{ return segment(l) + segment.t(l).perp().norm()*width; }

		void step(const Real &l1) {

			Vector p1 = segment(l1) + segment.t(l1).perp().norm()*width;

			if (++level < max_level)

				while (greater((p1 - p0).lensqr(), precision_sqr))

					step(l0 + 0.5*(l1 - l0));

			--level;

			context.line_to(p1);

			p0 = p1; l0 = l1;

		}

	public:

		DrawSegment(const Context &context, const Segment &segment, const Real &width):

			context(context), segment(segment), width(width), precision_sqr(context.pixelsize_sqr()), level(), l0()

		{

			context.line_to(p0 = func(0));

			step(1);

		}

	};

}

CurvesArea::CurvesArea()

{

	set_size_request(500, 500);

	Vector center(250, 250);

	const Real radius = 100;

	const Real tangent_len = 50;

	const int count = 5;

	for(int i = 0; i < count; ++i) {

		Real a = 2*pi*i/count;

		Vector v = Vector::from_angle(a);

		curve.push_back(CurvePoint(center + v*radius, v*tangent_len));

		curve.back().add_to(*this);

	}

	curve.loop = true;

}

void CurvesArea::put_segment(const Context &context, const Segment &segment, const Real width) {

	if (equal(width, 0)) context.segment(segment);

		            else DrawSegment(context, segment, width);

}

void CurvesArea::put_curve(const Context &context, const Curve &curve, const Real width) {

	for(Curve::const_iterator curr = curve.begin(); curr != curve.end(); ++curr) {

		Curve::const_iterator next = curve.next(curr);

		put_segment(context, Segment(curr->get_p(), next->get_p(), curr->get_t(), next->get_t()), width);

	}

}

void CurvesArea::draw_curve(const Context &context, const Curve &curve) {

	context->save();

	Real width = 50;

	context.set_line_width_px(1);

	// tangents

	context.set_source_rgba(Color::gray());

	for(Curve::const_iterator i = curve.begin(); i != curve.end(); ++i) {

		context.move_to(i->p->position);

		context.line_to(i->t->position);

		context->stroke();

	}

	// middle line

	context.set_source_rgba(Color::black());

	put_curve(context, curve);

	context->stroke();

	// borders

	context.set_source_rgba(Color::blue());

	put_curve(context, curve, width);

	context->stroke();

	put_curve(context, curve, -width);

	context->stroke();

	context->restore();

}

void CurvesArea::on_draw_content(const Context &context) {

	draw_curve(context, curve);

}