circular_maze.cpp

/*
 */

#include "common/sketchbook.hpp"

using namespace common;
using support::wrap;

constexpr float2 size(range2f x)
{
	return x.upper() - x.lower();
}

[[nodiscard]]
constexpr float2 rotate(float2 v, float angle)
{
	return rotate(v, protractor<>::tau(angle));
}

[[nodiscard]]
constexpr float distance(float2 a, float2 b)
{
	return support::root2(quadrance(a-b));
}

// ugh! dealing with modulo arithmetic is harder than i thought...
// could be because i chose (0,1) instead of (-1,1)?
// there has got to be a better way to do this regardless.
// maybe just mod/wrap at the last moment and otherwise work in normal arithmetic
// hint; mod_cmp used in both of below,
// fix a, consider b and (b +/- mod),
// calculate diff and abs_diff and chose min by abs_diff
// return both chosen abs_diff and corresponding diff
[[nodiscard]]
constexpr float mod_distance(float a, float b, float mod)
{
	auto minmax = std::minmax(a,b);
	return std::min( minmax.second - minmax.first, minmax.first + mod - minmax.second);
}
[[nodiscard]]
constexpr float mod_difference(float a, float b, float mod)
{
	const auto distance = mod_distance(a,b,mod);
	const auto difference = b > a ? +distance : -distance;
	return support::abs(b-a) > distance ? -difference : +difference;
}

constexpr float cord_length(float slice_angle, float radius = 1.f)
{

	// very clear - self descriptive
	// very simple - naive direct implementation
	// fast?
	// + distance can be replaced with quadrance
	return distance(
		rotate(float2::i(radius), slice_angle),
		float2::i(radius)
	);

	// // very obscure - need a picture to understand
	// // very complicated - need advanced calculus to implement
	// // slow?
	// return 2 * radius * sin(slice_angle/2 * tau);

};

constexpr range2f fit(float2 area, float2 unit)
{
	// N dimensional =)
	auto scale = area/unit;
	auto min_dimension = support::min_element(scale) - scale.begin();
	auto fit_area = scale[min_dimension] * unit;
	auto cenering_mask = float2::one() - float2::unit(min_dimension);
	return range2f{float2::zero(), fit_area}
		+ (area - fit_area)/2 * (cenering_mask);
};

class circular_maze
{
	int layers = 10;
	float2 _screen_size;
	float fov;
	rangef fov_range;
	range2f bounds;

	float corridor_radius;
	float wall_width;
	float initial_radius;

	float2 center;

	using float_NxM = std::vector<std::vector<float>>;
	float_NxM walls;
	float_NxM paths;


	std::optional<float> closest_wall(int level, float angle)
	{
		auto closest = support::min_element(walls[level], [&](auto a, auto b)
		{
			return abs(a - angle) < abs(b - angle);
		});

		if(closest != walls[level].end())
			return *closest;
		return std::nullopt;
	}

	float path_edge_proximity(int level, float angle)
	{
		float proximity = std::numeric_limits<float>::infinity();
		const float radius = corridor_radius/tau/2/(initial_radius + level * corridor_radius);
		for(auto&& path : paths[level])
		{
			proximity = std::min(mod_distance(path + radius, angle, 1.f), proximity);
			proximity = std::min(mod_distance(path - radius, angle, 1.f), proximity);
		}
		return proximity * tau * (level*corridor_radius + initial_radius);
	}

	float wall_proximity(int level, float angle)
	{
		auto closest = closest_wall(level, angle);
		return closest
			? mod_distance(*closest, angle, 1.f) * tau * (level * corridor_radius + initial_radius)
			: std::numeric_limits<float>::infinity();
	}

	float proximity(int level, float angle)
	{
		return std::min(
			path_edge_proximity(level,angle),
			wall_proximity(level,angle)
		);
	}

	public:
	float current_angle = 0;
	float player_level = -1;
	auto get_corridor_radius() const {return corridor_radius;}

	circular_maze(float2 screen_size) :
		layers(7),
		_screen_size(screen_size),
		fov(1.f/8),
		fov_range{-fov/2,+fov/2},
		bounds{fit(screen_size,{cord_length(fov),1.f})},
		corridor_radius( size(bounds).y() / (layers+2) ),
		wall_width(corridor_radius/6),
		initial_radius(corridor_radius * 2),
		center{bounds.lower()+(bounds.upper() - bounds.lower()) * float2{0.5f,1.f}}
	{
		walls.resize(layers);
		paths.resize(layers);

		for(int i = 0; i < layers * 5; ++i)
		{
			int level;
			float angle;
			int breaker = 2000;
			do
			{
				level = trand_int({0,layers});
				angle = trand_float();
			}
			while(proximity(level, angle) < corridor_radius && breaker --> 0);
			paths[level].push_back(angle);
		}

		for(int i = 0; i < layers*layers; ++i)
		{
			int level;
			float angle;
			int breaker = 2000;
			do
			{
				level = trand_int({0,layers-1});
				angle = trand_float();
			}
			while((proximity(level, angle) < corridor_radius ||
				path_edge_proximity(level + 1, angle) < corridor_radius) && breaker --> 0);
			walls[level].push_back(angle);
		}

	}

	const float2& screen_size() { return _screen_size; }

	std::optional<float> hit_test(float angle, float level, const float_NxM& elements)
	{
		if(level < 0 || level >= layers)
			return std::nullopt;

		for(auto&& element : elements[level])
		{
			const auto radius = level * corridor_radius + initial_radius;
			const auto player_position = -float2::j(radius);
			const auto element_position = rotate(float2::i(radius), wrap(angle + element, 1.f));
			if(quadrance(player_position - element_position) < corridor_radius * corridor_radius / 4)
				return element;
		}
		return std::nullopt;
	}

	std::optional<float> wall_hit_test(float angle)
	{
		return hit_test(angle, player_level, walls);
	}

	std::optional<float> path_hit_test(float angle, float level, float direction)
	{
		return hit_test(angle, level + (direction+1)/2, paths);
	}

	void circular_move(float velocity)
	{
		const auto radius = player_level * corridor_radius + initial_radius;
		const auto corridor_angle = corridor_radius/tau/radius;
		const auto max_angular_velocity = corridor_angle*0.8;
		float angular_velocity = velocity/tau/radius;
		if(abs(angular_velocity) > max_angular_velocity)
			angular_velocity = std::copysign(max_angular_velocity, angular_velocity);

		auto new_angle = wrap(current_angle + angular_velocity, 1.f);
		auto hit_wall = wall_hit_test(new_angle);
		if(!hit_wall)
		{
			current_angle = new_angle;
		}
		else
		{
			const auto offset = std::copysign(corridor_angle*0.51f, mod_difference(current_angle + *hit_wall, 3.f/4, 1.f));
			current_angle = wrap(3.f/4 - *hit_wall - offset, 1.f);
		}
	}

	void draw(vg::frame& frame)
	{
		frame.begin_sketch()
			.rectangle(rect{ frame.size })
			.fill(0x1d4151_rgb)
		;

		const auto fov_range_up = fov_range - 1.f/4;


		{auto sketch = frame.begin_sketch();
			float radius = initial_radius;
			for(int i = 0; i < layers; ++i)
			{
				sketch.arc(center, fov_range_up * tau, radius - corridor_radius/2);
				radius += corridor_radius;
			}
			sketch.line_width(wall_width).outline(0xfbfbf9_rgb);
		}

		{auto sketch = frame.begin_sketch();
		float radius = initial_radius - corridor_radius/2;
		for(size_t level = 0; level < paths.size(); ++level, radius += corridor_radius)
		{
			float path_arc_angle = (corridor_radius * 0.8)/tau/radius;
			auto path_arc_range = range{-path_arc_angle, path_arc_angle}/2;
			for(size_t angle = 0; angle < paths[level].size(); ++angle)
			{
				const auto path_angle = wrap(
					paths[level][angle] + current_angle,
				1.f);
				if(!(fov_range_up + 1.f).intersects(path_arc_range + path_angle))
					continue;

				// TODO: approximate arc with a polygon so that we don't need to convert to radians,
				// here and everywhere
				sketch.arc(center, (path_arc_range + path_angle) * tau, radius);
			}
		} sketch.line_width(wall_width + 3).outline(0x1d4151_rgb); }

		float radius = initial_radius - corridor_radius/2;
		for(size_t level = 0; level < walls.size(); ++level, radius += corridor_radius)
		{
			const float wall_arc_angle = wall_width/tau/radius;
			const auto wall_arc_range = range{-wall_arc_angle, wall_arc_angle}/2;
			for(size_t angle = 0; angle < walls[level].size(); ++angle)
			{
				const auto wall_angle = wrap(
					walls[level][angle] + current_angle,
				1.f);
				const auto intersection = (fov_range_up + 1.f).intersection(wall_arc_range + wall_angle);
				if(!intersection.valid())
					continue;

				const auto visible_wall_angle = intersection.upper() - intersection.lower();
				const auto visible_wall_width = wall_width * visible_wall_angle/wall_arc_angle;
				const auto wall_anchor = intersection.lower() == (fov_range_up + 1.f).lower() ? .5f : -.5f;

				// TODO: welp, looks like even here, polygon would be better, to render different widths with one draw call
				frame.begin_sketch()
					.line(
						center + rotate(
							float2::i(initial_radius + corridor_radius*(float(level)-0.5f)),
							wall_angle + wall_anchor * (wall_arc_angle - visible_wall_angle)
						),
						center + rotate(
							float2::i(initial_radius + corridor_radius*(float(level)+0.5f)),
							wall_angle + wall_anchor * (wall_arc_angle - visible_wall_angle)
						)
					)
					.line_width(visible_wall_width).outline(0xfbfbf9_rgb);
			}
		}

		const auto player_diameter =
			corridor_radius - wall_width -3;
		const auto player_center =
			center - float2::j(player_level * corridor_radius + initial_radius);
		frame.begin_sketch().ellipse(rect{
			float2::one(player_diameter),
			player_center,
			half
		}).fill(paint::radial_gradient(
			player_center,
			{player_diameter/2 * .3f, player_diameter/2},
			{rgba_vector(0x00feed'ff_rgba), rgba_vector(0x00000000_rgba)}));
	};

	void diagram(vg::frame& frame)
	{
		auto fov_range_up = fov_range - 1.f/4;
		auto sketch = frame.begin_sketch();
		float radius = initial_radius;
		for(int i = 0; i < layers; ++i)
		{
			sketch.arc(center, fov_range_up * tau, radius);
			radius += corridor_radius;
		}

		for(size_t level = 0; level < walls.size(); ++level)
		{
			for(size_t angle = 0; angle < walls[level].size(); ++angle)
			{
				const auto wall_angle = wrap(
					walls[level][angle] + current_angle,
				1.f);
				if(!(fov_range_up + 1.f).contains(wall_angle))
					continue;
				sketch.ellipse(rect{
					float2::one(4),
					center +
					rotate(
						float2::i(initial_radius + corridor_radius*level),
						wall_angle
					),
					half
				});
			}
		}

		for(size_t level = 0; level < paths.size(); ++level)
		{
			for(size_t angle = 0; angle < paths[level].size(); ++angle)
			{
				const auto path_angle = wrap(
					paths[level][angle] + current_angle,
				1.f);
				if(!(fov_range_up + 1.f).contains(path_angle))
					continue;

				sketch.line(
					center + rotate(
						float2::i(initial_radius + corridor_radius*level),
						path_angle
					),
					center + rotate(
						float2::i(initial_radius + corridor_radius*(float(level)-1)),
						path_angle
					)
				);
			}
		}

		sketch.ellipse(rect{
			float2::one(corridor_radius),
			center - float2::j(player_level * corridor_radius + initial_radius),
			half
		});

		sketch.line_width(1).outline(0x0_rgb);
	}

} maze(float2::one(400));

using radial_motion_t = movement<float, motion::quadratic_curve>;
using circular_motion_t = movement<float, motion::quadratic_curve>;

melody<circular_motion_t, radial_motion_t>
complex_radial_motion;
radial_motion_t simple_radial_motion;

struct radial_movement
{
	float path = 0;
	float level = 0;
};
std::queue<radial_movement> radial_movements;
void make_radial_movement(float direction)
{
	auto level = !empty(radial_movements) ? radial_movements.back().level : maze.player_level;
	auto angle = !empty(radial_movements)
	? wrap(3/4.f - radial_movements.back().path, 1.f)
	: maze.current_angle;
	auto path = maze.path_hit_test(angle, level, direction);
	if(path)
		radial_movements.push({*path, level + direction});
}

bool diagram = false;
std::optional<float2> drag = std::nullopt;
std::optional<float2> jerk = std::nullopt;
float2 possible_jerk = float2::zero();
float circular_velocity = 0.f;

void start(Program& program)
{
	program.fullscreen = true;

	program.draw_once = [](auto frame)
	{
		maze = circular_maze(frame.size);
	};

	program.key_down = [](scancode code, keycode)
	{
		switch(code)
		{
			case scancode::j:
			case scancode::down:
				make_radial_movement(-1);
			break;

			case scancode::k:
			case scancode::up:
				make_radial_movement(+1);
			break;

			case scancode::d:
				diagram = !diagram;
			break;

			default: break;
		}
	};

	program.mouse_down = [](float2, auto)
	{
		drag = float2::zero();
		circular_velocity = 0;
		possible_jerk = float2::zero();
	};

	program.mouse_up = [](auto, auto)
	{
		drag = std::nullopt;
		jerk = std::nullopt;
	};

	program.mouse_move = [](auto, float2 motion)
	{
		if(drag)
		{
			*drag += motion;

			if(!jerk)
			{
				// TODO: use mouse_motion::window_normalized_motion
				possible_jerk += motion / (maze.get_corridor_radius()/3);
				if(trunc(possible_jerk) != float2::zero())
					jerk = signum(trunc(possible_jerk));
			}
		}
	};

	program.draw_loop = [](auto frame, auto delta)
	{

		maze.draw(frame);
		if(diagram)
			maze.diagram(frame);

		if(!complex_radial_motion.done())
		{
			float unwrapped_angle = maze.current_angle;
			auto result = complex_radial_motion.move(std::forward_as_tuple(
				unwrapped_angle,
				maze.player_level)
			, delta);
			maze.current_angle = wrap(unwrapped_angle, 1.f);

			if(result.done)
			{
				radial_movements.pop();
				circular_velocity = 0;
			}
		}
		else if(!simple_radial_motion.done())
		{
			auto result = simple_radial_motion.move(maze.player_level, delta);

			if(result.done)
				radial_movements.pop();
		}
		else
		{
			if(!empty(radial_movements))
			{
				auto movement = radial_movements.front();

				auto circular_distance = mod_difference(maze.current_angle, wrap(3/4.f - movement.path, 1.f), 1.f);
				auto radial_distance = movement.level - maze.player_level;
				auto radial_motion = radial_motion_t
				{
					abs(radial_distance) * 100ms,
					maze.player_level, movement.level
				};
				if(abs(circular_distance) > 0)
				{
					complex_radial_motion = melody(
						circular_motion_t{ abs(circular_distance) * 10s,
							maze.current_angle,
							maze.current_angle + circular_distance },
						radial_motion
					);
				}
				else
					simple_radial_motion = radial_motion;
			}

			if(pressed(scancode::h) || pressed(scancode::left))
			{
				maze.circular_move(1);
				circular_velocity = 1;
			}

			if(pressed(scancode::l) || pressed(scancode::right))
			{
				maze.circular_move(-1);
				circular_velocity = -1;
			}

			if(drag)
			{
				circular_velocity += drag->x();
				maze.circular_move(drag->x()/3);

				if(jerk && (*jerk * float2::j() != float2::zero()))
				{
					make_radial_movement(-jerk->y());
					jerk = float2::zero(); // prevents further jerks on this drag TODO: should probably add some kind of a timer on this, to eventually reset back to nullopt
				}

				drag = float2::zero();
			}
			else
			{
				maze.circular_move(circular_velocity/3);
			}
			circular_velocity *= 0.8f;
		}

	};
}