// SPDX-FileCopyrightText: 2022 Erin Catto

// SPDX-FileCopyrightText: 2025 Ikpil Choi(ikpil@naver.com)

// SPDX-License-Identifier: MIT

using System;

using static Box2D.NET.B2Ids;

using static Box2D.NET.B2Geometries;

using static Box2D.NET.B2Types;

using static Box2D.NET.B2MathFunction;

using static Box2D.NET.B2Bodies;

using static Box2D.NET.B2Shapes;

using static Box2D.NET.B2Joints;

using static Box2D.NET.B2Constants;

using static Box2D.NET.B2Worlds;

using static Box2D.NET.B2Timers;

using static Box2D.NET.B2Diagnostics;

namespace Box2D.NET.Shared

{

public static class Determinism

{

public static FallingHingeData CreateFallingHinges(B2WorldId worldId)

{

{

B2BodyDef bodyDef = b2DefaultBodyDef();

bodyDef.position = new B2Vec2(0.0f, -1.0f);

B2BodyId groundId = b2CreateBody(worldId, bodyDef);

B2Polygon box = b2MakeBox(40.0f, 1.0f);

B2ShapeDef shapeDef = b2DefaultShapeDef();

b2CreatePolygonShape(groundId, shapeDef, box);

}

int columnCount = 4;

int rowCount = 20;

int bodyCount = rowCount * columnCount;

B2BodyId[] bodyIds = new B2BodyId[bodyCount];

{

float h = 0.25f;

float r = 0.1f * h;

B2Polygon box = b2MakeRoundedBox(h - r, h - r, r);

box = b2MakeSquare(h);

B2ShapeDef shapeDef = b2DefaultShapeDef();

//shapeDef.material.friction = 0.3f;

B2RevoluteJointDef jointDef = b2DefaultRevoluteJointDef();

jointDef.enableLimit = true;

jointDef.lowerAngle = -0.1f * B2_PI;

jointDef.upperAngle = 0.2f * B2_PI;

jointDef.enableSpring = true;

jointDef.hertz = 1.0f;

jointDef.dampingRatio = 1.0f;

jointDef.enableMotor = true;

jointDef.maxMotorTorque = 0.25f;

jointDef.@base.localFrameA.p = new B2Vec2(-h, h);

jointDef.@base.localFrameB.p = new B2Vec2(-h, -h);

jointDef.@base.constraintHertz = 60.0f;

jointDef.@base.constraintDampingRatio = 0.0f;

jointDef.@base.drawScale = 0.5f;

int bodyIndex = 0;

float offset = 0.4f * h;

float dx = 10.0f * h;

float xBase = -0.5f * dx * (columnCount - 1.0f);

for (int j = 0; j < columnCount; ++j)

{

float x = xBase + j * dx;

B2BodyId prevBodyId = b2_nullBodyId;

for (int i = 0; i < rowCount; ++i)

{

B2BodyDef bodyDef = b2DefaultBodyDef();

bodyDef.type = B2BodyType.b2_dynamicBody;

bodyDef.position.X = x + offset * i;

bodyDef.position.Y = h + 2.0f * h * i;

// this tests the deterministic cosine and sine functions

float angle = (i & 1) == 0 ? -0.1f : 0.1f;

bodyDef.rotation = b2MakeRot(angle);

B2BodyId bodyId = b2CreateBody(worldId, bodyDef);

if ((i & 1) == 0)

{

prevBodyId = bodyId;

}

else

{

jointDef.@base.bodyIdA = prevBodyId;

jointDef.@base.bodyIdB = bodyId;

b2CreateRevoluteJoint(worldId, jointDef);

prevBodyId = b2_nullBodyId;

}

b2CreatePolygonShape(bodyId, shapeDef, box);

B2_ASSERT(bodyIndex < bodyCount);

bodyIds[bodyIndex] = bodyId;

bodyIndex += 1;

}

}

B2_ASSERT(bodyIndex == bodyCount);

}

FallingHingeData data = new FallingHingeData();

data.bodyIds = bodyIds;

data.bodyCount = bodyCount;

data.stepCount = 0;

data.sleepStep = -1;

data.hash = 0;

return data;

}

public static bool UpdateFallingHinges(B2WorldId worldId, ref FallingHingeData data)

{

if (data.hash == 0)

{

B2BodyEvents bodyEvents = b2World_GetBodyEvents(worldId);

if (bodyEvents.moveCount == 0)

{

int awakeCount = b2World_GetAwakeBodyCount(worldId);

B2_ASSERT(awakeCount == 0);

data.hash = B2_HASH_INIT;

Span<byte> bxf = stackalloc byte[B2SizeOf<float>.Size * 4];

for (int i = 0; i < data.bodyCount; ++i)

{

B2Transform xf = b2Body_GetTransform(data.bodyIds[i]);

xf.TryWriteBytes(bxf);

data.hash = b2Hash(data.hash, bxf, bxf.Length);

}

data.sleepStep = data.stepCount;

}

}

data.stepCount += 1;

return data.hash != 0;

}

public static void DestroyFallingHinges(ref FallingHingeData data)

{

//free( data.bodyIds );

data.bodyIds = null;

}

}

}