// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef B2_SHAPE_H
#define B2_SHAPE_H

#include "b2_api.h"
#include "b2_math.h"
#include "b2_collision.h"

class b2BlockAllocator;

/// This holds the mass data computed for a shape.
struct B2_API b2MassData
{
	/// The mass of the shape, usually in kilograms.
	float mass;

	/// The position of the shape's centroid relative to the shape's origin.
	b2Vec2 center;

	/// The rotational inertia of the shape about the local origin.
	float I;
};

/// A shape is used for collision detection. You can create a shape however you like.
/// Shapes used for simulation in b2World are created automatically when a b2Fixture
/// is created. Shapes may encapsulate a one or more child shapes.
class B2_API b2Shape
{
public:

	enum Type
	{
		e_circle = 0,
		e_edge = 1,
		e_polygon = 2,
		e_chain = 3,
		e_typeCount = 4
	};

	virtual ~b2Shape() {}

	/// Clone the concrete shape using the provided allocator.
	virtual b2Shape* Clone(b2BlockAllocator* allocator) const = 0;

	/// Get the type of this shape. You can use this to down cast to the concrete shape.
	/// @return the shape type.
	Type GetType() const;
	
	/// Test a point for containment in this shape. This only works for convex shapes.
	/// @param xf the shape world transform.
	/// @param p a point in world coordinates.
	virtual bool TestPoint(const b2Transform& xf, const b2Vec2& p) const = 0;

	/// Compute the distance from the current shape to the specified point. This only works for convex shapes.
	/// @param xf the shape world transform.
	/// @param p a point in world coordinates.
	/// @param distance returns the distance from the current shape.
	/// @param normal returns the direction in which the distance increases.
	virtual void ComputeDistance(const b2Transform& xf, const b2Vec2& p, float32* distance, b2Vec2* normal) const= 0;

	/// Cast a ray against a child shape.
	/// @param output the ray-cast results.
	/// @param input the ray-cast input parameters.
	/// @param transform the transform to be applied to the shape.
	/// @param childIndex the child shape index
	virtual bool RayCast(b2RayCastOutput* output, const b2RayCastInput& input,
						const b2Transform& transform) const = 0;

	/// Given a transform, compute the associated axis aligned bounding box for a child shape.
	/// @param aabb returns the axis aligned box.
	/// @param xf the world transform of the shape.
	/// @param childIndex the child shape
	virtual void ComputeAABB(b2AABB* aabb, const b2Transform& xf) const = 0;

	/// Compute the mass properties of this shape using its dimensions and density.
	/// The inertia tensor is computed about the local origin.
	/// @param massData returns the mass data for this shape.
	/// @param density the density in kilograms per meter squared.
	virtual void ComputeMass(b2MassData* massData, float density) const = 0;

	Type m_type;

	/// Radius of a shape. For polygonal shapes this must be b2_polygonRadius. There is no support for
	/// making rounded polygons.
	float m_radius;
};

inline b2Shape::Type b2Shape::GetType() const
{
	return m_type;
}

#endif