/******************************************************************************
 * Spine Runtimes License Agreement
 * Last updated April 5, 2025. Replaces all prior versions.
 *
 * Copyright (c) 2013-2026, Esoteric Software LLC
 *
 * Integration of the Spine Runtimes into software or otherwise creating
 * derivative works of the Spine Runtimes is permitted under the terms and
 * conditions of Section 2 of the Spine Editor License Agreement:
 * http://esotericsoftware.com/spine-editor-license
 *
 * Otherwise, it is permitted to integrate the Spine Runtimes into software
 * or otherwise create derivative works of the Spine Runtimes (collectively,
 * "Products"), provided that each user of the Products must obtain their own
 * Spine Editor license and redistribution of the Products in any form must
 * include this license and copyright notice.
 *
 * THE SPINE RUNTIMES ARE PROVIDED BY ESOTERIC SOFTWARE LLC "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL ESOTERIC SOFTWARE LLC BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES,
 * BUSINESS INTERRUPTION, OR LOSS OF USE, DATA, OR PROFITS) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THE SPINE RUNTIMES, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *****************************************************************************/

using System;

namespace Spine {

	/// <summary>The applied local pose and world transform for a bone. This is the <see cref="Bone.Pose"/> with constraints applied and the
	/// world transform computed by <see cref="Skeleton.UpdateWorldTransform(Physics)"/> and <see cref="UpdateWorldTransform(Skeleton)"/>.
	/// <para>
	/// If the world transform is changed, call <see cref="UpdateLocalTransform(Skeleton)"/> before using the local transform. The local
	/// transform may be needed by other code (eg to apply another constraint).</para>
	/// <para>
	/// After changing the world transform, call <see cref="UpdateWorldTransform(Skeleton)"/> on every descendant bone. It may be more
	/// convenient to modify the local transform instead, then call <see cref="Skeleton.UpdateWorldTransform(Physics)"/> to update the world
	/// transforms for all bones and apply constraints.</para>
	/// </summary>
	public class BonePose : IPose<BonePose>, IUpdate {
		public Bone bone;

		internal float x, y, rotation, scaleX, scaleY, shearX, shearY;
		internal Inherit inherit;

		internal float a, b, worldX;
		internal float c, d, worldY;
		internal int world, local;

		public void Set (BonePose pose) {
			if (pose == null) throw new ArgumentNullException("pose", "pose cannot be null.");
			x = pose.x;
			y = pose.y;
			rotation = pose.rotation;
			scaleX = pose.scaleX;
			scaleY = pose.scaleY;
			shearX = pose.shearX;
			shearY = pose.shearY;
			inherit = pose.inherit;
		}

		/// <summary>The local X translation.</summary>
		public float X { get { return x; } set { x = value; } }
		/// <summary>The local Y translation.</summary>
		public float Y { get { return y; } set { y = value; } }

		/// <summary>Sets local x and y translation.</summary>
		public void SetPosition (float x, float y) {
			this.x = x;
			this.y = y;
		}

		/// <summary>The local rotation.</summary>
		public float Rotation { get { return rotation; } set { rotation = value; } }

		/// <summary>The local scaleX.</summary>
		public float ScaleX { get { return scaleX; } set { scaleX = value; } }

		/// <summary>The local scaleY.</summary>
		public float ScaleY { get { return scaleY; } set { scaleY = value; } }

		/// <summary>Sets local scaleX and scaleY.</summary>
		public void SetScale (float scaleX, float scaleY) {
			this.scaleX = scaleX;
			this.scaleY = scaleY;
		}

		/// <summary>Sets local scaleX and scaleY to the same value.</summary>
		public void SetScale (float scale) {
			scaleX = scale;
			scaleY = scale;
		}

		/// <summary>The local shearX.</summary>
		public float ShearX { get { return shearX; } set { shearX = value; } }

		/// <summary>The local shearY.</summary>
		public float ShearY { get { return shearY; } set { shearY = value; } }

		/// <summary>Determines how parent world transforms affect this bone.</summary>
		public Inherit Inherit { get { return inherit; } set { inherit = value; } }

		/// <summary>
		/// Called by <see cref="Skeleton.UpdateCache()"/> to compute the world transform, if needed.
		/// </summary>
		public void Update (Skeleton skeleton, Physics physics) {
			if (world != skeleton.update) UpdateWorldTransform(skeleton);
		}

		/// <summary>Computes the world transform using the parent bone's world transform and this applied local pose. Child bones are not
		/// updated.
		/// <para>
		/// See <a href="http://esotericsoftware.com/spine-runtime-skeletons#World-transforms">World transforms</a> in the Spine
		/// Runtimes Guide.</para></summary>
		public void UpdateWorldTransform (Skeleton skeleton) {
			if (local == skeleton.update)
				UpdateLocalTransform(skeleton);
			else
				world = skeleton.update;

			if (bone.parent == null) { // Root bone.
				float sx = skeleton.scaleX, sy = skeleton.ScaleY;
				float rx = (rotation + shearX) * MathUtils.DegRad;
				float ry = (rotation + 90 + shearY) * MathUtils.DegRad;
				a = (float)Math.Cos(rx) * scaleX * sx;
				b = (float)Math.Cos(ry) * scaleY * sx;
				c = (float)Math.Sin(rx) * scaleX * sy;
				d = (float)Math.Sin(ry) * scaleY * sy;
				worldX = x * sx + skeleton.x;
				worldY = y * sy + skeleton.y;
				return;
			}

			BonePose parent = bone.parent.appliedPose;
			float pa = parent.a, pb = parent.b, pc = parent.c, pd = parent.d;
			worldX = pa * x + pb * y + parent.worldX;
			worldY = pc * x + pd * y + parent.worldY;

			switch (inherit) {
			case Inherit.Normal: {
				float rx = (rotation + shearX) * MathUtils.DegRad;
				float ry = (rotation + 90 + shearY) * MathUtils.DegRad;
				float la = (float)Math.Cos(rx) * scaleX;
				float lb = (float)Math.Cos(ry) * scaleY;
				float lc = (float)Math.Sin(rx) * scaleX;
				float ld = (float)Math.Sin(ry) * scaleY;
				a = pa * la + pb * lc;
				b = pa * lb + pb * ld;
				c = pc * la + pd * lc;
				d = pc * lb + pd * ld;
				break;
			}
			case Inherit.OnlyTranslation: {
				float sx = skeleton.scaleX, sy = skeleton.ScaleY;
				float rx = (rotation + shearX) * MathUtils.DegRad;
				float ry = (rotation + 90 + shearY) * MathUtils.DegRad;
				a = (float)Math.Cos(rx) * scaleX * sx;
				b = (float)Math.Cos(ry) * scaleY * sx;
				c = (float)Math.Sin(rx) * scaleX * sy;
				d = (float)Math.Sin(ry) * scaleY * sy;
				break;
			}
			case Inherit.NoRotationOrReflection: {
				float sx = skeleton.scaleX, sy = skeleton.ScaleY, sxi = 1 / sx, syi = 1 / sy;
				pa *= sxi;
				pc *= syi;
				float s = pa * pa + pc * pc, r;
				if (s > MathUtils.EpsilonSq) {
					s = Math.Abs(pa * pd * syi - pb * sxi * pc) / s;
					pb = pc * s;
					pd = pa * s;
					r = rotation - MathUtils.Atan2Deg(pc, pa);
				} else {
					pa = 0;
					pc = 0;
					r = rotation - 90 + MathUtils.Atan2Deg(pd, pb);
				}
				float rx = (r + shearX) * MathUtils.DegRad;
				float ry = (r + shearY + 90) * MathUtils.DegRad;
				float la = (float)Math.Cos(rx) * scaleX;
				float lb = (float)Math.Cos(ry) * scaleY;
				float lc = (float)Math.Sin(rx) * scaleX;
				float ld = (float)Math.Sin(ry) * scaleY;
				a = (pa * la - pb * lc) * sx;
				b = (pa * lb - pb * ld) * sx;
				c = (pc * la + pd * lc) * sy;
				d = (pc * lb + pd * ld) * sy;
				break;
			}
			case Inherit.NoScale:
			case Inherit.NoScaleOrReflection: {
				float sx = skeleton.scaleX, sy = skeleton.ScaleY, sxi = 1 / sx, syi = 1 / sy;
				float r = rotation * MathUtils.DegRad, cos = (float)Math.Cos(r), sin = (float)Math.Sin(r);
				float za = (pa * cos + pb * sin) * sxi;
				float zc = (pc * cos + pd * sin) * syi;
				float s = 1 / (float)Math.Sqrt(za * za + zc * zc);
				za *= s;
				zc *= s;
				float zb = -zc, zd = za;
				if (inherit == Inherit.NoScale && pa * pd - pb * pc < 0 != (sx < 0 != sy < 0)) {
					zb = -zb;
					zd = -zd;
				}
				float rx = shearX * MathUtils.DegRad;
				float ry = (90 + shearY) * MathUtils.DegRad;
				float la = (float)Math.Cos(rx) * scaleX;
				float lb = (float)Math.Cos(ry) * scaleY;
				float lc = (float)Math.Sin(rx) * scaleX;
				float ld = (float)Math.Sin(ry) * scaleY;
				a = (za * la + zb * lc) * sx;
				b = (za * lb + zb * ld) * sx;
				c = (zc * la + zd * lc) * sy;
				d = (zc * lb + zd * ld) * sy;
				break;
			}
			}
		}

		/// <summary>
		/// Computes the local transform values from the world transform.
		/// <para>
		/// Some information is ambiguous in the world transform, such as -1,-1 scale versus 180 rotation. The local transform after
		/// calling this method is equivalent to the local transform used to compute the world transform, but may not be identical.
		/// </para></summary>
		public void UpdateLocalTransform (Skeleton skeleton) {
			local = 0;
			world = skeleton.update;

			float sx = skeleton.scaleX, sy = skeleton.ScaleY;
			if (bone.parent == null) {
				float sxi = 1 / sx, syi = 1 / sy;
				x = (worldX - skeleton.x) * sxi;
				y = (worldY - skeleton.y) * syi;
				Set(a * sxi, b * sxi, c * syi, d * syi, 0);
				return;
			}

			BonePose parent = bone.parent.appliedPose;
			float pa = parent.a, pb = parent.b, pc = parent.c, pd = parent.d;
			float pad = pa * pd - pb * pc, pid = 1 / pad;
			float ia = pd * pid, ib = pb * pid, ic = pc * pid, id = pa * pid;
			float dx = worldX - parent.worldX, dy = worldY - parent.worldY;
			x = dx * ia - dy * ib;
			y = dy * id - dx * ic;

			switch (inherit) {
			case Inherit.Normal: {
				Set(ia * a - ib * c, ia * b - ib * d, id * c - ic * a, id * d - ic * b, 0);
				break;
			}
			case Inherit.OnlyTranslation: {
				float sxi = 1 / sx, syi = 1 / sy;
				Set(a * sxi, b * sxi, c * syi, d * syi, 0);
				break;
			}
			case Inherit.NoRotationOrReflection: {
				float sxi = 1 / sx, syi = 1 / sy;
				pa *= sxi;
				pc *= syi;
				float wa = a * sxi, wb = b * sxi, wc = c * syi, wd = d * syi;
				float s = 1 / (pa * pa + pc * pc), det = 1 / Math.Abs(pad * sxi * syi);
				Set((pa * wa + pc * wc) * s, (pa * wb + pc * wd) * s, (pa * wc - pc * wa) * det, (pa * wd - pc * wb) * det,
					MathUtils.Atan2Deg(pc, pa));
				break;
			}
			case Inherit.NoScale:
			case Inherit.NoScaleOrReflection: {
				float sxi = 1 / sx, syi = 1 / sy;
				float wa = a * sxi, wb = b * sxi, wc = c * syi, wd = d * syi;
				float tx = pd * a - pb * c, ty = pa * c - pc * a;
				if (pad < 0) {
					tx = -tx;
					ty = -ty;
				}
				float r = MathUtils.Atan2Deg(ty, tx);
				rotation = r;
				r *= MathUtils.DegRad;
				float cos = (float)Math.Cos(r), sin = (float)Math.Sin(r);
				float za = (pa * cos + pb * sin) * sxi;
				float zc = (pc * cos + pd * sin) * syi;
				float s = 1 / (float)Math.Sqrt(za * za + zc * zc);
				za *= s;
				zc *= s;
				float si = inherit == Inherit.NoScale && pad < 0 != (sx < 0 != sy < 0) ? -1 : 1;
				Set(za * wa + zc * wc, za * wb + zc * wd, (za * wc - zc * wa) * si, (za * wd - zc * wb) * si);
				break;
			}
			}
		}

		private void Set (float ra, float rb, float rc, float rd) {
			float x = ra * ra + rc * rc, y = rb * rb + rd * rd;
			if (x > MathUtils.EpsilonSq) {
				shearX = MathUtils.Atan2Deg(rc, ra);
				scaleX = (float)Math.Sqrt(x);
			} else {
				shearX = 0;
				scaleX = 0;
			}
			scaleY = (float)Math.Sqrt(y);
			if (y > MathUtils.EpsilonSq) {
				shearY = MathUtils.Atan2Deg(rd, rb);
				if (ra * rd - rb * rc < 0) {
					scaleY = -scaleY;
					shearY += 90;
				} else
					shearY -= 90;
				if (shearY > 180)
					shearY -= 360;
				else if (shearY <= -180) //
					shearY += 360;
			} else
				shearY = 0;
		}

		private void Set (float ra, float rb, float rc, float rd, float ro) {
			shearX = 0;
			float x = ra * ra + rc * rc, y = rb * rb + rd * rd;
			if (x > MathUtils.EpsilonSq) {
				float r = MathUtils.Atan2Deg(rc, ra);
				rotation = r + ro;
				scaleX = (float)Math.Sqrt(x);
				scaleY = (float)Math.Sqrt(y);
				if (y > MathUtils.EpsilonSq) {
					shearY = MathUtils.Atan2Deg(rd, rb);
					if (ra * rd - rb * rc < 0) {
						scaleY = -scaleY;
						shearY += 90 - r;
					} else
						shearY -= 90 + r;
					if (shearY > 180)
						shearY -= 360;
					else if (shearY <= -180) //
						shearY += 360;
				} else
					shearY = 0;
			} else {
				scaleX = 0;
				scaleY = (float)Math.Sqrt(y);
				shearY = 0;
				rotation = y > MathUtils.EpsilonSq ? MathUtils.Atan2Deg(rd, rb) - 90 + ro : ro;
			}
		}

		/// <summary>
		/// If the world transform has been modified by constraints and the local transform no longer matches,
		/// <see cref="UpdateLocalTransform(Skeleton)"/> is called. Call this after <see cref="Skeleton.UpdateWorldTransform(Physics)"/> before
		/// using the applied local transform.
		/// </summary>
		public void ValidateLocalTransform (Skeleton skeleton) {
			if (local == skeleton.update) UpdateLocalTransform(skeleton);
		}

		internal void ModifyLocal (Skeleton skeleton) {
			if (local == skeleton.update) UpdateLocalTransform(skeleton);
			world = 0;
			ResetWorld(skeleton.update);
		}

		internal void ModifyWorld (int update) {
			local = update;
			world = update;
			ResetWorld(update);
		}

		private void ResetWorld (int update) {
			Bone[] children = bone.children.Items;
			for (int i = 0, n = bone.children.Count; i < n; i++) {
				BonePose child = children[i].appliedPose;
				if (child.world == update) {
					child.world = 0;
					child.local = 0;
					child.ResetWorld(update);
				}
			}
		}

		/// <summary>The world transform <c>[a b][c d]</c> x-axis x component.</summary>
		public float A { get { return a; } set { a = value; } }
		/// <summary>The world transform <c>[a b][c d]</c> y-axis x component.</summary>
		public float B { get { return b; } set { b = value; } }
		/// <summary>The world transform <c>[a b][c d]</c> x-axis y component.</summary>
		public float C { get { return c; } set { c = value; } }
		/// <summary>The world transform <c>[a b][c d]</c> y-axis y component.</summary>
		public float D { get { return d; } set { d = value; } }

		/// <summary>The world X position.</summary>
		public float WorldX { get { return worldX; } set { worldX = value; } }
		/// <summary>The world Y position.</summary>
		public float WorldY { get { return worldY; } set { worldY = value; } }
		/// <summary>The world rotation for the X axis, calculated using <see cref="a"/> and <see cref="c"/>. This is the direction the
		/// bone is pointing.</summary>
		public float WorldRotationX { get { return MathUtils.Atan2Deg(c, a); } }
		/// <summary>The world rotation for the Y axis, calculated using <see cref="b"/> and <see cref="d"/>.</summary>
		public float WorldRotationY { get { return MathUtils.Atan2Deg(d, b); } }

		/// <summary>Returns the magnitude (always positive) of the world scale X, calculated using <see cref="a"/> and <see cref="c"/>.</summary>
		public float WorldScaleX { get { return (float)Math.Sqrt(a * a + c * c); } }
		/// <summary>Returns the magnitude (always positive) of the world scale Y, calculated using <see cref="b"/> and <see cref="d"/>.</summary>
		public float WorldScaleY { get { return (float)Math.Sqrt(b * b + d * d); } }

		/// <summary>Transforms a point from world coordinates to the bone's local coordinates.</summary>
		public void WorldToLocal (float worldX, float worldY, out float localX, out float localY) {
			float a = this.a, b = this.b, c = this.c, d = this.d;
			float det = a * d - b * c;
			float x = worldX - this.worldX, y = worldY - this.worldY;
			localX = (x * d - y * b) / det;
			localY = (y * a - x * c) / det;
		}

		/// <summary>Transforms a point from the bone's local coordinates to world coordinates.</summary>
		public void LocalToWorld (float localX, float localY, out float worldX, out float worldY) {
			worldX = localX * a + localY * b + this.worldX;
			worldY = localX * c + localY * d + this.worldY;
		}

		/// <summary>Transforms a point from world coordinates to the parent bone's local coordinates.</summary>
		public void WorldToParent (float worldX, float worldY, out float parentX, out float parentY) {
			if (bone.parent == null) {
				parentX = worldX;
				parentY = worldY;
			} else {
				bone.parent.appliedPose.WorldToLocal(worldX, worldY, out parentX, out parentY);
			}
		}

		/// <summary>Transforms a point from the parent bone's coordinates to world coordinates.</summary>
		public void ParentToWorld (float parentX, float parentY, out float worldX, out float worldY) {
			if (bone.parent == null) {
				worldX = parentX;
				worldY = parentY;
			} else {
				bone.parent.appliedPose.LocalToWorld(parentX, parentY, out worldX, out worldY);
			}
		}

		/// <summary>Transforms a world rotation to a local rotation.</summary>
		public float WorldToLocalRotation (float worldRotation) {
			worldRotation *= MathUtils.DegRad;
			float sin = (float)Math.Sin(worldRotation), cos = (float)Math.Cos(worldRotation);
			return MathUtils.Atan2Deg(a * sin - c * cos, d * cos - b * sin) + rotation - shearX;
		}

		/// <summary>Transforms a local rotation to a world rotation.</summary>
		public float LocalToWorldRotation (float localRotation) {
			localRotation = (localRotation - rotation - shearX) * MathUtils.DegRad;
			float sin = (float)Math.Sin(localRotation), cos = (float)Math.Cos(localRotation);
			return MathUtils.Atan2Deg(cos * c + sin * d, cos * a + sin * b);
		}

		/// <summary>Rotates the world transform the specified amount.</summary>
		public void RotateWorld (float degrees) {
			degrees *= MathUtils.DegRad;
			float sin = (float)Math.Sin(degrees), cos = (float)Math.Cos(degrees);
			float ra = a, rb = b;
			a = cos * ra - sin * c;
			b = cos * rb - sin * d;
			c = sin * ra + cos * c;
			d = sin * rb + cos * d;
		}

		override public string ToString () {
			return bone.data.name;
		}
	}
}