# include <Siv3D.hpp> // OpenSiv3D v0.3.2


class Bullet : public Circle
{
private:
	Vec2 m_vel;
	bool m_is_friend;

public:
	Bullet(Vec2 pos, Vec2 vel, bool is_friend = false)
		: Circle(pos, 5)
		, m_vel(vel)
		, m_is_friend(is_friend)
	{}

	bool isFriend() const { return m_is_friend; }
	bool isOut() const { return !intersects(Window::ClientRect().stretched(100)); }
	void update() { moveBy(m_vel); }
	void draw() const { Circle::draw(ColorF(m_is_friend ? 0.8 : 0.6)); }
};


class Item : public RectF
{
private:
	static Array<String> m_Label;
	int m_category;

public:
	Item(Vec2 pos, int category)
		: RectF(pos, 40.0)
		, m_category(Min(category, getCategoryNum()))
	{}

	String getLabel() const { return m_Label.at(m_category); }
	static int getCategoryNum() { return m_Label.count() - 1; }
	bool isOut() const { return !RectF::intersects(Window::ClientRect().stretched(100)); }
	void update() { RectF::moveBy(Vec2::Down(100.0 * System::DeltaTime())); }

	void draw() const
	{
		rotated(Periodic::Sine0_1(3.0s) * Math::TwoPi)
			.draw(HSV(220).lerp(HSV(330), (double)m_category / getCategoryNum()))
			.drawFrame(1.0, ColorF(0.0));
		FontAsset(U"item")(m_Label.at(m_category)).drawAt(center());
	}
};
Array<String> Item::m_Label({ U"HP", U"S", U"R", U"W" });


class Shooter
{
protected:
	double m_Max_health;
	double m_health;
	Stopwatch m_cooldown;

public:
	Shooter(double Max_health = 100.0)
		: m_Max_health(Max_health)
		, m_health(Max_health)
		, m_cooldown(true)
	{}

	bool isDead() const { return m_health <= 0.0; }
	void damage(double amount) { m_health = Max(0.0, m_health - amount); }
	void heal(double amout) { m_health = Min(m_Max_health, m_health + amout); }
};


class Player : public Triangle, public Shooter
{
private:
	double m_speed_factor;
	double m_reload_factor;
	int m_way;
	Font m_font;

public:
	Player(double health = 1000.0)
		: Triangle(Window::Width() / 2, Window::Height() * 4 / 5, 30.0)
		, Shooter(health)
		, m_speed_factor(1.0)
		, m_reload_factor(1.0)
		, m_way(1)
		, m_font(100)
	{}

	void addSpeed(double amount = 0.3) { m_speed_factor += amount; }
	void addReload(double amount = 0.3) { m_reload_factor += amount; }
	void addWay(int amount = 1) { m_way += amount; }

	Array<Bullet> GenerateBullets() const
	{
		Array<Bullet> generate;
		if (m_way == 1)
		{
			generate << Bullet(centroid(), Vec2::Up(5.0), true);
			return generate;
		}
		const double theta_base = 30_deg / Math::Pow((double)(m_way - 1), 0.8);
		for (int i : step(m_way))
		{
			const double theta = (i - (double)(m_way - 1) / 2) * theta_base;
			generate << Bullet(centroid(), Circular(5.0, theta), true);
		}
		return generate;
	}

	bool update()
	{
		Vec2 Key_input(KeyD.pressed() - KeyA.pressed(), KeyS.pressed() - KeyW.pressed());
		if (Key_input.length() > 1.0) Key_input.normalize();
		const double speed = (KeyShift.pressed() ? 0.5 : 1.0) * m_speed_factor * 100.0 * System::DeltaTime();
		const Vec2 pos = centroid().movedBy(Key_input * speed);
		setCentroid(pos.clamped(Window::ClientRect()));

		if (KeySpace.pressed() && m_cooldown.msF() > 200.0 / m_reload_factor)
		{
			m_cooldown.restart();
			return true;
		}
		return false;
	}

	void drawStatus(int score) const
	{
		const int baseX = Window::Width() / 6, baseY = Window::Height() / 6;
		Transformer2D t0(Mat3x2::Translate(baseX, baseY));
		m_font(U"Score {:d}"_fmt(score)).draw(0, 0, ColorF(1.0, 0.2));
		Transformer2D t1(Mat3x2::Translate(0, baseY));
		m_font(U"Speed {:.1f}"_fmt(m_speed_factor)).draw(0, 0, ColorF(1.0, 0.2));
		Transformer2D t2(Mat3x2::Translate(0, baseY));
		m_font(U"Reload {:.1f}"_fmt(m_reload_factor)).draw(0, 0, ColorF(1.0, 0.2));
		Transformer2D t3(Mat3x2::Translate(0, baseY));
		m_font(U"Way {:d}"_fmt(m_way)).draw(0, 0, ColorF(1.0, 0.2));
		Transformer2D t4(Mat3x2::Translate(0, baseY));
		const double e = Max(0.0, m_health) / m_Max_health;
		const HSV color = HSV(0, 0.2).lerp(HSV(120, 0.2), e);
		m_font(U"HP {:.1f}%"_fmt(100.0 * e)).draw(0, 0, color);
	}

	void draw() const
	{
		Triangle::draw(ColorF(0.5, 0.5, 1.0));
	}
};


class Enemy : public Circle, public Shooter
{
private:
	Vec2 m_start;
	Vec2 m_dest;
	Transition m_transition;

public:
	Enemy(double health = 100.0)
		: Circle(20)
		, Shooter(health)
		, m_transition(3.0s)
	{
		m_dest = RandomVec2(Window::Width(), Window::Height() * 0.3);
		m_start = m_dest + Vec2(m_dest - Window::Center());
		setPos(m_start);
	}

	bool update()
	{
		m_transition.update(true);
		setPos(m_start.lerp(m_dest, m_transition.easeOut()));

		if (m_cooldown > 2.0s)
		{
			m_cooldown.restart();
			return true;
		}
		return false;
	}

	void draw() const
	{
		const double e = Max(0.0, m_health) / m_Max_health;
		Circle::draw(ColorF(1.0, 0.5, 0.5))
			.drawFrame(1.0, ColorF(0.0))
			.drawPie(-Math::Pi * e, Math::TwoPi * e, HSV(0).lerp(HSV(120), e));
		Line({ 0, 0 }, Circular(r,  Math::Pi * e)).movedBy(center).draw(ColorF(0.0, EaseOutExpo(1.0 - e)));
		Line({ 0, 0 }, Circular(r, -Math::Pi * e)).movedBy(center).draw(ColorF(0.0, EaseOutExpo(1.0 - e)));
		Circle::scaled(0.7).draw(ColorF(1.0, 0.5, 0.5))
			.drawArc(-Math::Pi * e, Math::TwoPi * e, 1.0, 0.0, ColorF(0.0));
	}
};


void Main()
{
	Window::Resize(800, 800);

	Player player;
	int score = 0;
	Array<Enemy> enemies(10);
	Array<Bullet> bullets;
	Array<Item> items;
	FontAsset::Register(U"item", 24);

	System::Sleep(5.0s);

	while (System::Update())
	{
		if (player.update())
			bullets.append(player.GenerateBullets());
		if (RandomBool(2.0 * System::DeltaTime()))
			enemies << Enemy();
		for (auto it = enemies.begin(); it != enemies.end();)
		{
			if (it->isDead())
			{
				score++;
				if (RandomBool()) items << Item(it->center, Random(Item::getCategoryNum()));
				it = enemies.erase(it);
				continue;
			}
			if (it->update())
				bullets << Bullet(it->center, Circular(3.0, Random(160_deg, 200_deg)));
			it++;
		}
		for (auto it = bullets.begin(); it != bullets.end();)
		{
			it->update();
			bool is_hit = false;
			if (it->isFriend())
			{
				Optional<int> enemy_index;
				enemies.each_index([&](int i, auto & e) { if (it->intersects(e)) enemy_index = i; });
				if (enemy_index)
				{
					enemies.at(enemy_index.value()).damage(Random(20.0, 60.0));
					is_hit = true;
				}
			}
			else {
				if (it->intersects(player))
				{
					player.damage(Random(8.0, 12.0));
					is_hit = true;
				}
			}
			if (it->isOut() || is_hit)
				it = bullets.erase(it);
			else
				it++;
		}
		for (auto it = items.begin(); it != items.end();)
		{
			it->update();
			if (it->intersects(player))
			{
				if (it->getLabel() == U"HP") player.heal(50.0);
				if (it->getLabel() == U"S") player.addSpeed();
				if (it->getLabel() == U"R") player.addReload();
				if (it->getLabel() == U"W") player.addWay();
				it = items.erase(it);
			}
			else if (it->isOut())
				it = items.erase(it);
			else
				it++;
		}

		player.drawStatus(score);
		bullets.each([](const auto & b) { b.draw(); });
		items.each([](const auto & i) { i.draw(); });
		enemies.each([](const auto & e) { e.draw(); });
		player.draw();
	}
}