using UnityEngine;

namespace GraphicsCat
{
    public class SlideRotationController : MonoBehaviour, IMGUIDockable
    {
        private const float INERTIA_THRESHOLD = 0.1f; // Threshold to stop inertia rotation

        [Header("Slide Rotation")]
        [InspectorDisplayName("Enable")]
        public bool slideRotationEnabled = false;
        [InspectorDisplayName("Sensitivity")]
        public Vector3 slideRotationSensitivity = new(0, 20, 0);
        [InspectorDisplayName("Inertia Damping")]
        [Range(0f, 1f)]
        public float inertiaDamping = 0.8f; // 0 = no inertia, 1 = maximum inertia

        [Header("Auto Rotation")]
        [InspectorDisplayName("Enable")]
        public bool autoRotationEnabled = true;
        [InspectorDisplayName("Speed")]
        public Vector3 autoRotationSpeed = new(0, 5, 0);

        [Header("Other")]
        public bool displayInGameGUI = false;

        // Input state
        private bool m_IsDragging = false;
        private Vector3 m_LastPointerPosition = Vector3.zero;
        private Vector3 m_PointerDelta = Vector3.zero;
        private Transform m_Target = null;

        // Touch input
        private Touch m_MainTouch;
        private bool m_IsTouchActive = false;

        // Auto rotation
        private bool m_WasAutoRotationEnabled;
        private bool m_IsAutoRotationPaused = false;

        // Inertia
        private Vector3 m_CurrentInertia = Vector3.zero;
        private Vector3 m_LastAngularVelocity = Vector3.zero;
        private bool m_HasAngularMovement = false; // Track if there was actual angular movement

        private void Start()
        {
            m_Target = transform;
            IMGUIDock.topRight.DockGUI(this);
        }

        private void Update()
        {
            if (!slideRotationEnabled)
                return;

            m_PointerDelta = Vector3.zero;

            HandleMouseInput();

            if (Application.isMobilePlatform)
                HandleTouchInput();
        }

        private void FixedUpdate()
        {
            Vector3 slideRotationDelta = Vector3.zero;

            if (slideRotationEnabled)
            {

                // Handle manual rotation
                if (m_PointerDelta != Vector3.zero)
                {
                    slideRotationDelta = ComputeRotationDelta(m_PointerDelta.x, m_PointerDelta.y);
                }
                // Apply inertia when not actively rotating
                else if (m_CurrentInertia.magnitude > INERTIA_THRESHOLD)
                {
                    slideRotationDelta = m_CurrentInertia;
                    m_CurrentInertia *= inertiaDamping;

                    if (m_CurrentInertia.magnitude < INERTIA_THRESHOLD)
                        m_CurrentInertia = Vector3.zero;
                }

                // Apply manual rotation or inertia
                if (slideRotationDelta != Vector3.zero)
                {
                    Quaternion deltaRotation = Quaternion.Euler(slideRotationDelta * Time.fixedDeltaTime);
                    m_Target.localRotation = deltaRotation * m_Target.localRotation;
                    m_LastAngularVelocity = slideRotationDelta;
                    m_HasAngularMovement = true; // There was actual rotation this frame
                }
                else
                {
                    // No rotation this frame
                    m_HasAngularMovement = false;
                }
            }
            
            // Apply auto rotation
            if (slideRotationDelta == Vector3.zero && autoRotationEnabled && !m_IsAutoRotationPaused)
            {
                ApplyAutoRotation();
            }
        }

        /// <summary>
        /// Apply auto rotation according to configured speed.
        /// </summary>
        private void ApplyAutoRotation()
        {
            Quaternion rotation = Quaternion.Euler(autoRotationSpeed * Time.fixedDeltaTime);
            m_Target.localRotation = rotation * m_Target.localRotation;
        }

        /// <summary>
        /// Compute rotation delta based on pointer movement.
        /// </summary>
        private Vector3 ComputeRotationDelta(float x, float y)
        {
            return Vector3.Scale(new Vector3(y, x, 0), -slideRotationSensitivity);
        }

        /// <summary>
        /// Handle mouse input for slide rotation.
        /// </summary>
        private void HandleMouseInput()
        {
            if (Input.GetMouseButtonDown(0))
            {
                if (IsPointerOverTarget(Input.mousePosition))
                {
                    m_IsDragging = true;
                    m_LastPointerPosition = Input.mousePosition;
                    m_CurrentInertia = Vector3.zero; // Reset inertia when starting drag
                    m_HasAngularMovement = false;

                    PauseAutoRotation();
                }
            }
            else if (Input.GetMouseButtonUp(0))
            {
                if (m_IsDragging)
                {
                    m_IsDragging = false;
                    // Only apply inertia if there was actual angular movement
                    if (m_HasAngularMovement)
                        ApplyInertia();
                    else
                        m_CurrentInertia = Vector3.zero; // No movement, no inertia
                    
                    ResumeAutoRotation();
                }
            }
            else if (Input.GetMouseButton(0) && m_IsDragging)
            {
                Vector3 currentPosition = Input.mousePosition;
                m_PointerDelta = currentPosition - m_LastPointerPosition;
                m_LastPointerPosition = currentPosition;
            }
            else
            {
                m_IsDragging = false;
            }
        }

        /// <summary>
        /// Handle touch input for slide rotation.
        /// </summary>
        private void HandleTouchInput()
        {
            int touchCount = Input.touchCount;
            if (touchCount <= 0)
            {
                m_IsTouchActive = false;
                return;
            }

            for (int i = 0; i < touchCount; i++)
            {
                Touch touch = Input.GetTouch(i);

                switch (touch.phase)
                {
                    case TouchPhase.Began:
                        if (IsPointerOverTarget(touch.position))
                        {
                            m_MainTouch = touch;
                            m_IsTouchActive = true;
                            m_LastPointerPosition = touch.position;
                            m_CurrentInertia = Vector3.zero; // Reset inertia when starting touch
                            m_HasAngularMovement = false;
                            PauseAutoRotation();
                        }
                        break;

                    case TouchPhase.Moved:
                        if (m_IsTouchActive && touch.fingerId == m_MainTouch.fingerId)
                        {
                            Vector3 currentTouchPosition = touch.position;
                            m_PointerDelta = currentTouchPosition - m_LastPointerPosition;
                            m_LastPointerPosition = currentTouchPosition;
                        }
                        break;

                    case TouchPhase.Ended:
                    case TouchPhase.Canceled:
                        if (m_IsTouchActive && touch.fingerId == m_MainTouch.fingerId)
                        {
                            m_IsTouchActive = false;
                            m_PointerDelta = Vector3.zero;
                            // Only apply inertia if there was actual angular movement
                            if (m_HasAngularMovement)
                                ApplyInertia();
                            else
                                m_CurrentInertia = Vector3.zero; // No movement, no inertia
                                
                            ResumeAutoRotation();
                        }
                        break;
                }
            }
        }

        /// <summary>
        /// Apply inertia based on the last angular velocity.
        /// Inertia is directly proportional to the angular velocity at the moment of release.
        /// </summary>
        private void ApplyInertia()
        {
            // Only apply inertia if there was significant angular velocity
            // This ensures inertia magnitude correlates with rotation speed at release
            if (inertiaDamping > 0 && m_LastAngularVelocity.magnitude > INERTIA_THRESHOLD)
                m_CurrentInertia = m_LastAngularVelocity * inertiaDamping;
            else
                m_CurrentInertia = Vector3.zero;
        }

        /// <summary>
        /// Temporarily pause auto rotation during user interaction.
        /// </summary>
        private void PauseAutoRotation()
        {
            if (autoRotationEnabled)
            {
                m_WasAutoRotationEnabled = autoRotationEnabled;
                autoRotationEnabled = false;
                m_IsAutoRotationPaused = true;
            }
        }

        /// <summary>
        /// Resume auto rotation after user interaction ends.
        /// </summary>
        private void ResumeAutoRotation()
        {
            if (m_IsAutoRotationPaused)
            {
                autoRotationEnabled = m_WasAutoRotationEnabled;
                m_IsAutoRotationPaused = false;
            }
        }

        /// <summary>
        /// Check if the given screen point is over this object using renderer bounds.
        /// </summary>
        private bool IsPointerOverTarget(Vector3 screenPoint)
        {
            Camera camera = Camera.main;
            if (camera == null)
                return false;

            Renderer[] renderers = m_Target.GetComponentsInChildren<Renderer>();
            if (renderers.Length == 0)
                return false;

            Ray ray = camera.ScreenPointToRay(screenPoint);
            foreach (Renderer renderer in renderers)
            {
                if (renderer.enabled && renderer.bounds.IntersectRay(ray))
                    return true;
            }

            return false;
        }

        public void OnDockGUI()
        {
            if (!displayInGameGUI)
                return;

            GUILayout.BeginHorizontal();
            if (GUILayout.Button("Slide Rotation " + (slideRotationEnabled ? "O" : "X")))
                slideRotationEnabled = !slideRotationEnabled;
            GUILayout.EndHorizontal();

            GUILayout.BeginHorizontal();
            if (GUILayout.Button("Auto Rotation " + (autoRotationEnabled ? "O" : "X")))
                autoRotationEnabled = !autoRotationEnabled;
            GUILayout.EndHorizontal();
        }
    }
}