#include "BaseBattle.h"

#include <algorithm>
#include <cmath>

#include <entt/entity/registry.hpp>
#include <entt/signal/dispatcher.hpp>

#include <kurator/campaign/Scenario.h>
#include <kurator/sim/components.h>
#include <kurator/sim/events.h>
#include <kurator/universe.h>

#include "Builder.h"


namespace kurator
{
namespace sim
{


BaseBattle::BaseBattle(const campaign::Scenario& scenario) :
	_registry {},
	spawner {scenario.total_teams(), scenario.radius, 0.1}
{
	const auto repo = universe::load_sample();
	Builder build {_registry, spawner};
	for (const auto& ship : scenario.ships) {
		const auto entity = build(repo->ship_type(ship.type), ship.team);
		for (const auto& turret_type : ship.turrets)
			build(repo->turret_type(turret_type), entity);
		manager.add(ship.team, entity);  // registry supports on construction events
	}
}


entt::registry&
BaseBattle::registry()
{
	return _registry;
}


entt::dispatcher&
BaseBattle::dispatcher()
{
	return _dispatcher;
}


void
BaseBattle::update(const float dt)
{
	pick_random_targets();
	keep_at_range();
	floating_movement(dt);
	turrets(dt);
	kill_off_dead();
	manager.clear(_registry);  // registry supports on destructions events
}


void
BaseBattle::pick_random_targets()
{
	auto view = _registry.view<Team, AIState>();
	for (auto&& [entity, team, ai] : view.each()) {
		if (!_registry.valid(ai.target))
			ai.target = manager.random((team.id + 1) % 2);  // FIXME
	}
}


void
BaseBattle::keep_at_range()
{
	auto view = _registry.view<Transform, AIState>();
	for (auto&& [entity, self, ai] : view.each()) {
		if (!_registry.valid(ai.target))
			continue;
		const auto target = _registry.get<Transform>(ai.target);
		const Point offset = target.position - self.position;
		ai.destination = target.position - offset.normalized().scale(6000.0);
	}
}


void
BaseBattle::floating_movement(const float dt)
{
	auto view = _registry.view<Transform, FloatingMovement, AIState>();
	for (auto&& [entity, transform, movement, ai] : view.each()) {
		const auto offset = ai.destination - transform.position;
		const auto at_destination = offset.magnitude() > movement.destination_boundary;
		const auto acceleration =
			at_destination ?
			offset.normalized().scale(movement.acceleration * dt) :
			offset.normalized().scale(-1 * movement.deceleration * dt);
		movement.speed.x += acceleration.x;
		movement.speed.y += acceleration.y;
		if (movement.speed.magnitude() > movement.max_speed)
			movement.speed = movement.speed.normalized().scale(movement.max_speed);
		const auto speed = movement.speed.scale(dt);
		transform.position.x += speed.x;
		transform.position.y += speed.y;
		transform.angle = speed.angle();
	}
}


double
effective_damage(const universe::TurretType& def, const double distance)
{
	const auto overflow = distance - def.optimal_range;
	const auto falloff = std::max(0.0, overflow / def.optimal_range / def.falloff_modifier);
	return def.base_damage * std::round(std::pow(def.falloff_intensity, std::pow(falloff, 2)) * 1000) / 1000;
}


void
BaseBattle::turrets(const float dt)
{
	auto view = _registry.view<TurretControl, universe::TurretType>();
	for (auto&& [entity, control, def] : view.each()) {
		if (!_registry.valid(control.owner)) {
			_registry.destroy(entity);
			continue;
		}
		const auto& [state, transform] = _registry.get<AIState, Transform>(control.owner);  // no checks
		if (!_registry.valid(state.target))
			continue;
		if (control.reload > 0.0)
			control.reload -= dt;
		if (control.reload <= 0.0) {
			auto& target_points = _registry.get<HitPoints>(state.target);
			const auto& target = _registry.get<Transform>(state.target);
			const auto distance = transform.position - target.position;
			const auto damage = effective_damage(def, distance.magnitude());
			if (damage > 0.0) {
				target_points.health -= damage;
				_dispatcher.trigger(Hit{damage, control.owner, state.target});
			}
			control.reload = def.rate_of_fire;
		}
	}
}


void
BaseBattle::kill_off_dead()
{
	auto view = _registry.view<HitPoints>();
	for (auto&& [entity, points] : view.each()) {
		if (points.health <= 0.0)
			_registry.destroy(entity);
	}
}


}  // namespace sim
}  // namespace kurator