// Crest Ocean System

// Copyright 2020 Wave Harmonic Ltd

using UnityEngine;
using UnityEngine.Events;

#if UNITY_EDITOR
using UnityEditor;
#endif

namespace Crest.Examples
{
    /// <summary>
    /// Emits useful events (UnityEvents) based on the sampled height of the ocean surface.
    /// </summary>
    [AddComponentMenu(Crest.Internal.Constants.MENU_PREFIX_EXAMPLE + "Ocean Sample Height Events")]
    public class OceanSampleHeightEvents : CustomMonoBehaviour
    {
        /// <summary>
        /// The version of this asset. Can be used to migrate across versions. This value should
        /// only be changed when the editor upgrades the version.
        /// </summary>
        [SerializeField, HideInInspector]
#pragma warning disable 414
        int _version = 0;
#pragma warning restore 414

        [Header("Settings For All Events")]

        [Tooltip("The higher the value, the more smaller waves will be ignored when sampling the ocean surface.")]
        [SerializeField] float _minimumWaveLength = 1f;


        [Header("Distance From Ocean Surface")]

        [Tooltip("A normalised distance from ocean surface will be between zero and one.")]
        [SerializeField] bool _normaliseDistance = true;

        [Tooltip("The maximum distance passed to function. Always use a real distance value (not a normalised one).")]
        [SerializeField] float _maximumDistance = 100f;

        [Tooltip("Apply a curve to the distance passed to the function.")]
        [SerializeField] AnimationCurve _distanceCurve = AnimationCurve.Linear(0f, 0f, 1f, 1f);


        [Header("Events")]

        [SerializeField] UnityEvent _onBelowOceanSurface = new UnityEvent();
        public UnityEvent OnBelowOceanSurface => _onBelowOceanSurface;
        [SerializeField] UnityEvent _onAboveOceanSurface = new UnityEvent();
        public UnityEvent OnAboveOceanSurface => _onAboveOceanSurface;
        [SerializeField] FloatEvent _distanceFromOceanSurface = new FloatEvent();
        public FloatEvent DistanceFromOceanSurface => _distanceFromOceanSurface;

        // Store state
        bool _isAboveSurface = false;
        bool _isFirstUpdate = true;
        readonly SampleHeightHelper _sampleHeightHelper = new SampleHeightHelper();

        // Dynamic UnityEvent definitions.
        [System.Serializable] public class FloatEvent : UnityEvent<float> { }

        void Update()
        {
            _sampleHeightHelper.Init(transform.position, 2f * _minimumWaveLength);

            if (_sampleHeightHelper.Sample(out var height))
            {
                var distance = transform.position.y - height;
                var isAboveSurface = distance > 0;

                // Has the below/above ocean surface state changed?
                if (_isAboveSurface != isAboveSurface || _isFirstUpdate)
                {
                    _isAboveSurface = isAboveSurface;
                    _isFirstUpdate = false;

                    if (_isAboveSurface)
                    {
                        _onAboveOceanSurface.Invoke();
                    }
                    else
                    {
                        _onBelowOceanSurface.Invoke();
                    }
                }

                // Save some processing when not being used.
                if (_distanceFromOceanSurface.GetPersistentEventCount() > 0)
                {
                    // Normalise distance so we can use the curve.
                    var distanceFromOceanSurface = _distanceCurve.Evaluate(1f - Mathf.Abs(distance) / _maximumDistance);

                    // Restore raw distance if desired.
                    if (!_normaliseDistance)
                    {
                        distanceFromOceanSurface = _maximumDistance - distanceFromOceanSurface * _maximumDistance;
                    }

                    _distanceFromOceanSurface.Invoke(distanceFromOceanSurface);
                }
            }
        }

#if UNITY_EDITOR
        [CustomEditor(typeof(OceanSampleHeightEvents))]
        public class OceanSampleHeightEventsEditor : CustomBaseEditor
        {
            public override void OnInspectorGUI()
            {
                EditorGUILayout.Space();
                EditorGUILayout.HelpBox
                (
                    "For the Above/Below Ocean Surface Events, whenever this game object goes below or above the ocean " +
                    "surface, the appropriate event is fired once per state change. It can be used to trigger audio to " +
                    "play underwater and much more. For the Distance From Ocean Surface event, it will pass the " +
                    "distance every frame (passing normalised distance to audio volume as an example).",
                    MessageType.Info
                );
                EditorGUILayout.Space();

                base.OnInspectorGUI();
            }
        }
#endif
    }
}