# frozen_string_literal: true

# Handles physics simulation.
class Physics
  def update(actors)
    actors.each do |actor|
      [0, 1].each do |axis|
        actor.position[axis] += actor.velocity[axis]
        actor.velocity[axis] *= 0.5

        actors.each do |other|
          next unless actor != other && collide?(actor, other)

          fix_position_of(actor, other, axis)
        end
      end
    end
  end

  private

  def collide?(actor, other)
    return false unless collide_for_axis?(actor, other, 0)
    return false unless collide_for_axis?(actor, other, 1)

    actor_is_solid = actor.collide(other)
    other_is_solid = other.collide(actor)

    actor_is_solid && other_is_solid
  end

  def collide_for_axis?(actor, other, axis)
    foo = actor.position[axis]
    bar = other.position[axis]
    foo_size = actor.aabb[axis] * 0.5
    bar_size = other.aabb[axis] * 0.5

    foo - foo_size < bar + bar_size && foo + foo_size > bar - bar_size
  end

  def fix_position_of(actor, other, axis)
    offset = (actor.aabb[axis] + other.aabb[axis]) * 0.5
    offset *= -1 if actor.velocity[axis].positive?
    actor.position[axis] = other.position[axis] + offset
  end
end