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 * Spine Runtimes License Agreement
 * Last updated July 28, 2023. Replaces all prior versions.
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 * Copyright (c) 2013-2023, Esoteric Software LLC
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#include <spine/IkConstraint.h>

#include <spine/Bone.h>
#include <spine/IkConstraintData.h>
#include <spine/Skeleton.h>

#include <spine/BoneData.h>

using namespace spine;

RTTI_IMPL(IkConstraint, Updatable)

void IkConstraint::apply(Bone &bone, float targetX, float targetY, bool compress, bool stretch, bool uniform, float alpha) {
	Bone *p = bone.getParent();
	float pa = p->_a, pb = p->_b, pc = p->_c, pd = p->_d;
	float rotationIK = -bone._ashearX - bone._arotation;
	float tx = 0, ty = 0;

	switch (bone._inherit) {
		case Inherit_OnlyTranslation:
			tx = (targetX - bone._worldX) * MathUtil::sign(bone.getSkeleton().getScaleX());
			ty = (targetY - bone._worldY) * MathUtil::sign(bone.getSkeleton().getScaleY());
			break;
		case Inherit_NoRotationOrReflection: {
			float s = MathUtil::abs(pa * pd - pb * pc) / MathUtil::max(0.0001f, pa * pa + pc * pc);
			float sa = pa / bone._skeleton.getScaleX();
			float sc = pc / bone._skeleton.getScaleY();
			pb = -sc * s * bone._skeleton.getScaleX();
			pd = sa * s * bone._skeleton.getScaleY();
			rotationIK += MathUtil::atan2Deg(sc, sa);
		}
		default:
			float x = targetX - p->_worldX, y = targetY - p->_worldY;
			float d = pa * pd - pb * pc;
			if (MathUtil::abs(d) <= 0.0001f) {
				tx = 0;
				ty = 0;
			} else {
				tx = (x * pd - y * pb) / d - bone._ax;
				ty = (y * pa - x * pc) / d - bone._ay;
			}
	}
	rotationIK += MathUtil::atan2Deg(ty, tx);
	if (bone._ascaleX < 0) rotationIK += 180;
	if (rotationIK > 180) rotationIK -= 360;
	else if (rotationIK < -180)
		rotationIK += 360;
	float sx = bone._ascaleX;
	float sy = bone._ascaleY;
	if (compress || stretch) {
		switch (bone._inherit) {
			case Inherit_NoScale:
			case Inherit_NoScaleOrReflection:
				tx = targetX - bone._worldX;
				ty = targetY - bone._worldY;
			default:;
		}

		float b = bone._data.getLength() * sx;
		if (b > 0.0001) {
			float dd = tx * tx + ty * ty;
			if ((compress && dd < b * b) || (stretch && dd > b * b)) {
				float s = (MathUtil::sqrt(dd) / b - 1) * alpha + 1;
				sx *= s;
				if (uniform) sy *= s;
			}
		}
	}
	bone.updateWorldTransform(bone._ax, bone._ay, bone._arotation + rotationIK * alpha, sx, sy, bone._ashearX,
							  bone._ashearY);
}

void IkConstraint::apply(Bone &parent, Bone &child, float targetX, float targetY, int bendDir, bool stretch, bool uniform,
						 float softness,
						 float alpha) {
	float a, b, c, d;
	float px, py, psx, psy, sx, sy;
	float cx, cy, csx, cwx, cwy;
	int o1, o2, s2, u;
	Bone *pp = parent.getParent();
	float tx, ty, dx, dy, dd, l1, l2, a1, a2, r, td, sd, p;
	float id, x, y;
	if (parent._inherit != Inherit_Normal || child._inherit != Inherit_Normal) return;
	px = parent._ax;
	py = parent._ay;
	psx = parent._ascaleX;
	psy = parent._ascaleY;
	sx = psx;
	sy = psy;
	csx = child._ascaleX;
	if (psx < 0) {
		psx = -psx;
		o1 = 180;
		s2 = -1;
	} else {
		o1 = 0;
		s2 = 1;
	}
	if (psy < 0) {
		psy = -psy;
		s2 = -s2;
	}
	if (csx < 0) {
		csx = -csx;
		o2 = 180;
	} else
		o2 = 0;
	r = psx - psy;
	cx = child._ax;
	u = (r < 0 ? -r : r) <= 0.0001f;
	if (!u || stretch) {
		cy = 0;
		cwx = parent._a * cx + parent._worldX;
		cwy = parent._c * cx + parent._worldY;
	} else {
		cy = child._ay;
		cwx = parent._a * cx + parent._b * cy + parent._worldX;
		cwy = parent._c * cx + parent._d * cy + parent._worldY;
	}
	a = pp->_a;
	b = pp->_b;
	c = pp->_c;
	d = pp->_d;
	id = a * d - b * c;
	id = MathUtil::abs(id) <= 0.0001f ? 0 : 1 / id;
	x = cwx - pp->_worldX;
	y = cwy - pp->_worldY;
	dx = (x * d - y * b) * id - px;
	dy = (y * a - x * c) * id - py;
	l1 = MathUtil::sqrt(dx * dx + dy * dy);
	l2 = child._data.getLength() * csx;
	if (l1 < 0.0001) {
		apply(parent, targetX, targetY, false, stretch, false, alpha);
		child.updateWorldTransform(cx, cy, 0, child._ascaleX, child._ascaleY, child._ashearX, child._ashearY);
		return;
	}
	x = targetX - pp->_worldX;
	y = targetY - pp->_worldY;
	tx = (x * d - y * b) * id - px;
	ty = (y * a - x * c) * id - py;
	dd = tx * tx + ty * ty;
	if (softness != 0) {
		softness *= psx * (csx + 1) * 0.5f;
		td = MathUtil::sqrt(dd);
		sd = td - l1 - l2 * psx + softness;
		if (sd > 0) {
			p = MathUtil::min(1.0f, sd / (softness * 2)) - 1;
			p = (sd - softness * (1 - p * p)) / td;
			tx -= p * tx;
			ty -= p * ty;
			dd = tx * tx + ty * ty;
		}
	}
	if (u) {
		float cosine;
		l2 *= psx;
		cosine = (dd - l1 * l1 - l2 * l2) / (2 * l1 * l2);
		if (cosine < -1) {
			cosine = -1;
			a2 = MathUtil::Pi * bendDir;
		} else if (cosine > 1) {
			cosine = 1;
			a2 = 0;
			if (stretch) {
				a = (MathUtil::sqrt(dd) / (l1 + l2) - 1) * alpha + 1;
				sx *= a;
				if (uniform) sy *= a;
			}
		} else
			a2 = MathUtil::acos(cosine) * bendDir;
		a = l1 + l2 * cosine;
		b = l2 * MathUtil::sin(a2);
		a1 = MathUtil::atan2(ty * a - tx * b, tx * a + ty * b);
	} else {
		a = psx * l2;
		b = psy * l2;
		float aa = a * a, bb = b * b, ll = l1 * l1, ta = MathUtil::atan2(ty, tx);
		float c0 = bb * ll + aa * dd - aa * bb, c1 = -2 * bb * l1, c2 = bb - aa;
		d = c1 * c1 - 4 * c2 * c0;
		if (d >= 0) {
			float q = MathUtil::sqrt(d), r0, r1;
			if (c1 < 0) q = -q;
			q = -(c1 + q) * 0.5f;
			r0 = q / c2;
			r1 = c0 / q;
			r = MathUtil::abs(r0) < MathUtil::abs(r1) ? r0 : r1;
			if (r * r <= dd) {
				y = MathUtil::sqrt(dd - r * r) * bendDir;
				a1 = ta - MathUtil::atan2(y, r);
				a2 = MathUtil::atan2(y / psy, (r - l1) / psx);
				goto break_outer;
			}
		}
		{
			float minAngle = MathUtil::Pi, minX = l1 - a, minDist = minX * minX, minY = 0;
			float maxAngle = 0, maxX = l1 + a, maxDist = maxX * maxX, maxY = 0;
			c0 = -a * l1 / (aa - bb);
			if (c0 >= -1 && c0 <= 1) {
				c0 = MathUtil::acos(c0);
				x = a * MathUtil::cos(c0) + l1;
				y = b * MathUtil::sin(c0);
				d = x * x + y * y;
				if (d < minDist) {
					minAngle = c0;
					minDist = d;
					minX = x;
					minY = y;
				}
				if (d > maxDist) {
					maxAngle = c0;
					maxDist = d;
					maxX = x;
					maxY = y;
				}
			}
			if (dd <= (minDist + maxDist) * 0.5f) {
				a1 = ta - MathUtil::atan2(minY * bendDir, minX);
				a2 = minAngle * bendDir;
			} else {
				a1 = ta - MathUtil::atan2(maxY * bendDir, maxX);
				a2 = maxAngle * bendDir;
			}
		}
	}
break_outer : {
	float os = MathUtil::atan2(cy, cx) * s2;
	a1 = (a1 - os) * MathUtil::Rad_Deg + o1 - parent._arotation;
	if (a1 > 180) a1 -= 360;
	else if (a1 < -180)
		a1 += 360;
	parent.updateWorldTransform(px, py, parent._arotation + a1 * alpha, sx, sy, 0, 0);
	a2 = ((a2 + os) * MathUtil::Rad_Deg - child._ashearX) * s2 + o2 - child._arotation;
	if (a2 > 180) a2 -= 360;
	else if (a2 < -180)
		a2 += 360;
	child.updateWorldTransform(cx, cy, child._arotation + a2 * alpha, child._ascaleX, child._ascaleY,
							   child._ashearX, child._ashearY);
}
}

IkConstraint::IkConstraint(IkConstraintData &data, Skeleton &skeleton) : Updatable(),
																		 _data(data),
																		 _bendDirection(data.getBendDirection()),
																		 _compress(data.getCompress()),
																		 _stretch(data.getStretch()),
																		 _mix(data.getMix()),
																		 _softness(data.getSoftness()),
																		 _target(skeleton.findBone(
																				 data.getTarget()->getName())),
																		 _active(false) {
	_bones.ensureCapacity(_data.getBones().size());
	for (size_t i = 0; i < _data.getBones().size(); i++) {
		BoneData *boneData = _data.getBones()[i];
		_bones.add(skeleton.findBone(boneData->getName()));
	}
}

void IkConstraint::update(Physics) {
	if (_mix == 0) return;
	switch (_bones.size()) {
		case 1: {
			Bone *bone0 = _bones[0];
			apply(*bone0, _target->getWorldX(), _target->getWorldY(), _compress, _stretch, _data._uniform, _mix);
		} break;
		case 2: {
			Bone *bone0 = _bones[0];
			Bone *bone1 = _bones[1];
			apply(*bone0, *bone1, _target->getWorldX(), _target->getWorldY(), _bendDirection, _stretch, _data._uniform,
				  _softness,
				  _mix);
		} break;
	}
}

int IkConstraint::getOrder() {
	return (int) _data.getOrder();
}

IkConstraintData &IkConstraint::getData() {
	return _data;
}

Vector<Bone *> &IkConstraint::getBones() {
	return _bones;
}

Bone *IkConstraint::getTarget() {
	return _target;
}

void IkConstraint::setTarget(Bone *inValue) {
	_target = inValue;
}

int IkConstraint::getBendDirection() {
	return _bendDirection;
}

void IkConstraint::setBendDirection(int inValue) {
	_bendDirection = inValue;
}

float IkConstraint::getMix() {
	return _mix;
}

void IkConstraint::setMix(float inValue) {
	_mix = inValue;
}

bool IkConstraint::getStretch() {
	return _stretch;
}

void IkConstraint::setStretch(bool inValue) {
	_stretch = inValue;
}

bool IkConstraint::getCompress() {
	return _compress;
}

void IkConstraint::setCompress(bool inValue) {
	_compress = inValue;
}

bool IkConstraint::isActive() {
	return _active;
}

void IkConstraint::setActive(bool inValue) {
	_active = inValue;
}

float IkConstraint::getSoftness() {
	return _softness;
}

void IkConstraint::setSoftness(float inValue) {
	_softness = inValue;
}

void IkConstraint::setToSetupPose() {
	IkConstraintData &data = this->_data;
	this->_mix = data._mix;
	this->_softness = data._softness;
	this->_bendDirection = data._bendDirection;
	this->_compress = data._compress;
	this->_stretch = data._stretch;
}