// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

using Microsoft.MixedReality.Toolkit.Utilities;
using Microsoft.MixedReality.Toolkit.Utilities.Solvers;
using System.Collections;
using UnityEngine;
using UnityEngine.Events;

namespace Microsoft.MixedReality.Toolkit.UI
{
    /// <summary>
    /// A utility script for toggling the 'Follow Me' behavior by activating/deactivating the Radial View Solver.
    /// This script also provides optional toggle at specified distance.
    /// </summary>
    [RequireComponent(typeof(RadialView))]
    [AddComponentMenu("Scripts/MRTK/SDK/FollowMeToggle")]
    public class FollowMeToggle : MonoBehaviour
    {
        /// <summary>
        /// An enum specifying how the optional interactable should behave once the FollowMe behavior was changed.
        /// </summary>
        public enum FollowMeBehaviorToInteractablesToggleState
        {
            ToggledWhenFollowing,
            UntoggledWhenFollowing,
            Manual
        }

        /// <summary>
        /// An optional object for visualizing the 'Follow Me' mode state.
        /// </summary>
        public GameObject VisualizationObject
        {
            get { return visualizationObject; }
            set { visualizationObject = value; }
        }

        [SerializeField]
        [Tooltip("An optional object for visualizing the 'Follow Me' mode state.")]
        private GameObject visualizationObject = null;

        /// <summary>
        /// An optional Interactable to select/deselect when toggling the follow behavior.
        /// </summary>
        public Interactable InteractableObject
        {
            get { return interactableObject; }
            set { interactableObject = value; }
        }

        [SerializeField]
        [Tooltip("An optional Interactable to select/deselect when toggling the follow behavior.")]
        private Interactable interactableObject = null;

        /// <summary>
        /// A way to indicate how should interactable react to the follow behavior state.
        /// </summary>
        public FollowMeBehaviorToInteractablesToggleState ButtonBehavior
        {
            get { return buttonBehavior; }
            set { buttonBehavior = value; }
        }

        [SerializeField]
        [Tooltip("Should following be automatically enabled when the user is further than a certain distance away?")]
        private FollowMeBehaviorToInteractablesToggleState buttonBehavior = FollowMeBehaviorToInteractablesToggleState.ToggledWhenFollowing;

        /// <summary>
        /// Should following be automatically enabled when the user is further than a certain distance away?
        /// </summary>
        public bool AutoFollowAtDistance
        {
            get { return autoFollowAtDistance; }
            set
            {
                autoFollowAtDistance = value;

                if (!enabled || !gameObject.activeInHierarchy)
                {
                    return;
                }

                if (autoFollowAtDistance)
                {
                    if (autoFollowDistanceCheck == null)
                    {
                        autoFollowDistanceCheck = StartCoroutine(AutoFollowDistanceCheck());
                    }
                }
                else
                {
                    if (autoFollowDistanceCheck != null)
                    {
                        StopCoroutine(autoFollowDistanceCheck);
                        autoFollowDistanceCheck = null;
                        SetFollowMeBehavior(false);
                    }
                }
            }
        }

        [SerializeField]
        [Tooltip("Should following be automatically enabled when the user is further than a certain distance away?")]
        private bool autoFollowAtDistance = false;

        /// <summary>
        /// If autoFollowAtDistance is enabled, what distance to trigger auto following at.
        /// </summary>
        public float AutoFollowDistance
        {
            get { return autoFollowDistance; }
            set { autoFollowDistance = value; }
        }

        [SerializeField]
        [Tooltip("If autoFollowAtDistance is enabled, what distance to trigger auto following at.")]
        private float autoFollowDistance = 2.0f;

        /// <summary>
        /// Optional transform to use when using autoFollowAtDistance. If not specified the local transform is used.
        /// </summary>
        public Transform AutoFollowTransformTarget
        {
            get { return autoFollowTransformTarget; }
            set
            {
                autoFollowTransformTarget = value;

                if (autoFollowTransformTarget == null)
                {
                    autoFollowTransformTarget = transform;
                }
            }
        }

        [SerializeField]
        [Tooltip("Optional transform to use when using autoFollowAtDistance. If not specified the local transform is used.")]
        private Transform autoFollowTransformTarget = null;

        private RadialView radialView = null;
        private Coroutine autoFollowDistanceCheck = null;

        [SerializeField]
        [Tooltip("Event that gets fired when auto follow is triggered.")]
        private UnityEvent autoFollowTriggered = new UnityEvent();
        /// <summary>
        /// Event that gets fired when auto follow is triggered.
        /// </summary>
        public UnityEvent AutoFollowTriggered
        {
            get => autoFollowTriggered;
            set => autoFollowTriggered = value;
        }


        #region MonoBehaviour Implementation

        private void Awake()
        {
            radialView = GetComponent<RadialView>();

            if (autoFollowTransformTarget == null)
            {
                autoFollowTransformTarget = transform;
            }

            // Begin the follow coroutine if requested at the beginning.
            AutoFollowAtDistance = autoFollowAtDistance;
        }

        private void OnValidate()
        {
            // When playing make sure the coroutine starts and stops based on inspector updates.
            if (Application.isPlaying)
            {
                AutoFollowAtDistance = autoFollowAtDistance;
            }
        }

        private void OnEnable()
        {
            // Begin the follow coroutine when enabled.
            AutoFollowAtDistance = autoFollowAtDistance;
        }
        
        private void OnDisable()
        {
            autoFollowDistanceCheck = null;
        }

        #endregion MonoBehaviour Implementation

        /// <summary>
        /// Toggles the current follow behavior of the solver.
        /// </summary>
        public void ToggleFollowMeBehavior()
        {
            if (radialView != null)
            {
                SetFollowMeBehavior(!radialView.enabled);
            }
        }

        /// <summary>
        /// Enables or disables the solver based on the follow parameter.
        /// </summary>
        /// <param name="follow">True if the solver should be active.</param>
        public void SetFollowMeBehavior(bool follow)
        {
            if (radialView != null && radialView.enabled != follow)
            {
                // Toggle Radial Solver component
                // You can tweak the detailed positioning behavior such as offset, lerping time, orientation type in the Inspector panel
                radialView.enabled = follow;

                if (visualizationObject != null)
                {
                    visualizationObject.SetActive(follow);
                }

                if (interactableObject != null)
                {
                    switch (ButtonBehavior)
                    {
                        case FollowMeBehaviorToInteractablesToggleState.ToggledWhenFollowing:
                            interactableObject.IsToggled = follow;
                            break;
                        case FollowMeBehaviorToInteractablesToggleState.UntoggledWhenFollowing:
                            interactableObject.IsToggled = !follow;
                            break;
                        case FollowMeBehaviorToInteractablesToggleState.Manual:
                            break;
                    }
                }
            }
        }

        /// <summary>
        /// Coroutine which checks how far away this transform is from the user and enables the follow behavior at a specified distance.
        /// </summary>
        /// <returns>Coroutine enumerator.</returns>
        private IEnumerator AutoFollowDistanceCheck()
        {
            while (true)
            {
                var mainCamera = CameraCache.Main;

                if (mainCamera != null)
                {
                    float autoFollowDistanceSq = autoFollowDistance * autoFollowDistance;

                    if (autoFollowTransformTarget != null)
                    {
                        if ((mainCamera.transform.position - autoFollowTransformTarget.position).sqrMagnitude >= autoFollowDistanceSq)
                        {
                            SetFollowMeBehavior(true);
                            AutoFollowTriggered?.Invoke();
                        }
                    }
                }
                yield return null;
            }
        }
    }
}