/******************************************************************************
 * Spine Runtimes License Agreement
 * Last updated April 5, 2025. Replaces all prior versions.
 *
 * Copyright (c) 2013-2025, 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.
 *****************************************************************************/

import SwiftUI
import Spine

struct IKFollowing: View {
    
    @StateObject
    var model = IKFollowingModel()
        
    var body: some View {
        SpineView(
            from: .bundle(atlasFileName: "spineboy-pma.atlas", skeletonFileName: "spineboy-pro.skel"),
            controller: model.controller,
            alignment: .centerLeft
        )
        .gesture(
            DragGesture(minimumDistance: 0)
                .onChanged { gesture in
                    model.crossHairPosition = model.controller.toSkeletonCoordinates(
                        position: gesture.location
                    )
                }
        )
        .navigationTitle("IK Following")
        .navigationBarTitleDisplayMode(.inline)
    }
}

#Preview {
    if #available(iOS 15.0, *) {
        IKFollowing()
            .previewInterfaceOrientation(.landscapeLeft)
    } else {
        IKFollowing()
    }
}

final class IKFollowingModel: ObservableObject {
    
    @Published
    var controller: SpineController!
    
    @Published
    var crossHairPosition: CGPoint?
    
    init() {
        controller = SpineController(
            onInitialized: { controller in
                controller.animationState.setAnimationByName(
                    trackIndex: 0,
                    animationName: "walk",
                    loop: true
                )
                controller.animationState.setAnimationByName(
                    trackIndex: 1,
                    animationName: "aim",
                    loop: true
                )
            },
            onAfterUpdateWorldTransforms: { 
                [weak self] controller in guard let self else { return }
                guard let worldPosition = self.crossHairPosition else {
                    return
                }
                let bone = controller.skeleton.findBone(boneName: "crosshair")!
                if let parent = bone.parent {
                    let position = parent.worldToLocal(worldX: Float(worldPosition.x), worldY:  Float(worldPosition.y))
                    bone.x = position.x
                    bone.y = position.y
                }
            }
        )
    }
}