/**********************************************************************************************
*
*   Physac v1.1 - 2D Physics library for videogames
*
*   DESCRIPTION:
*
*   Physac is a small 2D physics engine written in pure C. The engine uses a fixed time-step thread loop
*   to simluate physics. A physics step contains the following phases: get collision information,
*   apply dynamics, collision solving and position correction. It uses a very simple struct for physic
*   bodies with a position vector to be used in any 3D rendering API.
*
*   CONFIGURATION:
*
*   #define PHYSAC_IMPLEMENTATION
*       Generates the implementation of the library into the included file.
*       If not defined, the library is in header only mode and can be included in other headers
*       or source files without problems. But only ONE file should hold the implementation.
*
*   #define PHYSAC_DEBUG
*       Show debug traces log messages about physic bodies creation/destruction, physic system errors,
*       some calculations results and NULL reference exceptions.
*
*   #define PHYSAC_AVOID_TIMMING_SYSTEM
*       Disables internal timming system, used by UpdatePhysics() to launch timmed physic steps,
*       it allows just running UpdatePhysics() automatically on a separate thread at a desired time step.
*       In case physics steps update needs to be controlled by user with a custom timming mechanism,
*       just define this flag and the internal timming mechanism will be avoided, in that case,
*       timming libraries are neither required by the module.
*
*   #define PHYSAC_MALLOC()
*   #define PHYSAC_CALLOC()
*   #define PHYSAC_FREE()
*       You can define your own malloc/free implementation replacing stdlib.h malloc()/free() functions.
*       Otherwise it will include stdlib.h and use the C standard library malloc()/free() function.
*
*   COMPILATION:
*
*   Use the following code to compile with GCC:
*       gcc -o $(NAME_PART).exe $(FILE_NAME) -s -static -lraylib -lopengl32 -lgdi32 -lwinmm -std=c99
*
*   VERSIONS HISTORY:
*       1.1 (20-Jan-2021) @raysan5: Library general revision 
*               Removed threading system (up to the user)
*               Support MSVC C++ compilation using CLITERAL()
*               Review DEBUG mechanism for TRACELOG() and all TRACELOG() messages
*               Review internal variables/functions naming for consistency
*               Allow option to avoid internal timming system, to allow app manage the steps
*       1.0 (12-Jun-2017) First release of the library
*
*
*   LICENSE: zlib/libpng
*
*   Copyright (c) 2016-2021 Victor Fisac (@victorfisac) and Ramon Santamaria (@raysan5)
*
*   This software is provided "as-is", without any express or implied warranty. In no event
*   will the authors be held liable for any damages arising from the use of this software.
*
*   Permission is granted to anyone to use this software for any purpose, including commercial
*   applications, and to alter it and redistribute it freely, subject to the following restrictions:
*
*     1. The origin of this software must not be misrepresented; you must not claim that you
*     wrote the original software. If you use this software in a product, an acknowledgment
*     in the product documentation would be appreciated but is not required.
*
*     2. Altered source versions must be plainly marked as such, and must not be misrepresented
*     as being the original software.
*
*     3. This notice may not be removed or altered from any source distribution.
*
**********************************************************************************************/
// Allow custom memory allocators
//----------------------------------------------------------------------------------
// Defines and Macros
//----------------------------------------------------------------------------------
//----------------------------------------------------------------------------------
// Data Types Structure Definition
//----------------------------------------------------------------------------------
typedef enum PhysicsShapeType { PHYSICS_CIRCLE = 0, PHYSICS_POLYGON } PhysicsShapeType;
// Previously defined to be used in PhysicsShape struct as circular dependencies
typedef struct PhysicsBodyData *PhysicsBody;
// Matrix2x2 type (used for polygon shape rotation matrix)
typedef struct Matrix2x2 {
    float m00;
    float m01;
    float m10;
    float m11;
} Matrix2x2;
typedef struct PhysicsVertexData {
    unsigned int vertexCount; // Vertex count (positions and normals)
    Vector2 positions[24 /* Maximum number of vertex for polygons shapes*/]; // Vertex positions vectors
    Vector2 normals[24 /* Maximum number of vertex for polygons shapes*/]; // Vertex normals vectors
} PhysicsVertexData;
typedef struct PhysicsShape {
    PhysicsShapeType type; // Shape type (circle or polygon)
    PhysicsBody body; // Shape physics body data pointer
    PhysicsVertexData vertexData; // Shape vertices data (used for polygon shapes)
    float radius; // Shape radius (used for circle shapes)
    Matrix2x2 transform; // Vertices transform matrix 2x2
} PhysicsShape;
typedef struct PhysicsBodyData {
    unsigned int id; // Unique identifier
    bool enabled; // Enabled dynamics state (collisions are calculated anyway)
    Vector2 position; // Physics body shape pivot
    Vector2 velocity; // Current linear velocity applied to position
    Vector2 force; // Current linear force (reset to 0 every step)
    float angularVelocity; // Current angular velocity applied to orient
    float torque; // Current angular force (reset to 0 every step)
    float orient; // Rotation in radians
    float inertia; // Moment of inertia
    float inverseInertia; // Inverse value of inertia
    float mass; // Physics body mass
    float inverseMass; // Inverse value of mass
    float staticFriction; // Friction when the body has not movement (0 to 1)
    float dynamicFriction; // Friction when the body has movement (0 to 1)
    float restitution; // Restitution coefficient of the body (0 to 1)
    bool useGravity; // Apply gravity force to dynamics
    bool isGrounded; // Physics grounded on other body state
    bool freezeOrient; // Physics rotation constraint
    PhysicsShape shape; // Physics body shape information (type, radius, vertices, transform)
} PhysicsBodyData;
typedef struct PhysicsManifoldData {
    unsigned int id; // Unique identifier
    PhysicsBody bodyA; // Manifold first physics body reference
    PhysicsBody bodyB; // Manifold second physics body reference
    float penetration; // Depth of penetration from collision
    Vector2 normal; // Normal direction vector from 'a' to 'b'
    Vector2 contacts[2]; // Points of contact during collision
    unsigned int contactsCount; // Current collision number of contacts
    float restitution; // Mixed restitution during collision
    float dynamicFriction; // Mixed dynamic friction during collision
    float staticFriction; // Mixed static friction during collision
} PhysicsManifoldData, *PhysicsManifold;
//----------------------------------------------------------------------------------
// Module Functions Declaration
//----------------------------------------------------------------------------------
// Physics system management
 void InitPhysics(void); // Initializes physics system
 void UpdatePhysics(void); // Update physics system
 void ResetPhysics(void); // Reset physics system (global variables)
 void ClosePhysics(void); // Close physics system and unload used memory
 void SetPhysicsTimeStep(double delta); // Sets physics fixed time step in milliseconds. 1.666666 by default
 void SetPhysicsGravity(float x, float y); // Sets physics global gravity force
// Physic body creation/destroy
 PhysicsBody CreatePhysicsBodyCircle(Vector2 pos, float radius, float density); // Creates a new circle physics body with generic parameters
 PhysicsBody CreatePhysicsBodyRectangle(Vector2 pos, float width, float height, float density); // Creates a new rectangle physics body with generic parameters
 PhysicsBody CreatePhysicsBodyPolygon(Vector2 pos, float radius, int sides, float density); // Creates a new polygon physics body with generic parameters
 void DestroyPhysicsBody(PhysicsBody body); // Destroy a physics body
// Physic body forces
 void PhysicsAddForce(PhysicsBody body, Vector2 force); // Adds a force to a physics body
 void PhysicsAddTorque(PhysicsBody body, float amount); // Adds an angular force to a physics body
 void PhysicsShatter(PhysicsBody body, Vector2 position, float force); // Shatters a polygon shape physics body to little physics bodies with explosion force
 void SetPhysicsBodyRotation(PhysicsBody body, float radians); // Sets physics body shape transform based on radians parameter
// Query physics info
 PhysicsBody GetPhysicsBody(int index); // Returns a physics body of the bodies pool at a specific index
 int GetPhysicsBodiesCount(void); // Returns the current amount of created physics bodies
 int GetPhysicsShapeType(int index); // Returns the physics body shape type (PHYSICS_CIRCLE or PHYSICS_POLYGON)
 int GetPhysicsShapeVerticesCount(int index); // Returns the amount of vertices of a physics body shape
 Vector2 GetPhysicsShapeVertex(PhysicsBody body, int vertex); // Returns transformed position of a body shape (body position + vertex transformed position)
/***********************************************************************************
*
*   PHYSAC IMPLEMENTATION
*
************************************************************************************/