/// ---------------------------------------------
/// Ultimate Character Controller
/// Copyright (c) Opsive. All Rights Reserved.
/// https://www.opsive.com
/// ---------------------------------------------

namespace Opsive.UltimateCharacterController.Objects
{
    using Opsive.Shared.Game;
    using Opsive.UltimateCharacterController.Audio;
    using Opsive.UltimateCharacterController.Game;
    using Opsive.UltimateCharacterController.Events;
    using Opsive.UltimateCharacterController.Objects.ItemAssist;
    using Opsive.UltimateCharacterController.Traits;
    using Opsive.UltimateCharacterController.Utility;
    using System.Collections.Generic;
    using UnityEngine;

    using EventHandler = Opsive.Shared.Events.EventHandler;

    /// <summary>
    /// Creates an explosion which applies a force and damage to any object that is within the specified radius.
    /// </summary>
    public class Explosion : MonoBehaviour
    {
        [Tooltip("Should the object explode when the object is enabled?")]
        [SerializeField] protected bool m_ExplodeOnEnable;
        [Tooltip("Determines how far out the explosion affects other objects.")]
        [SerializeField] protected float m_Radius = 5;
        [Tooltip("The maximum amount of damage the explosion applies to objects with the Health component.")]
        [SerializeField] protected float m_DamageAmount = 10;
        [Tooltip("The maximum amount of force the explosion applies to nearby Rigidbody/IForceObject objects.")]
        [SerializeField] protected float m_ImpactForce = 2;
        [Tooltip("The number of frames to add the impact force to.")]
        [SerializeField] protected int m_ImpactForceFrames = 1;
        [Tooltip("The layers that the explosion can affect.")]
        [SerializeField] protected LayerMask m_ImpactLayers = ~(1 << LayerManager.IgnoreRaycast | 1 << LayerManager.Water | 1 << LayerManager.SubCharacter | 1 << LayerManager.Overlay | 
                                                                1 << LayerManager.VisualEffect);
        [Tooltip("Does the explosion require line of sight in order to damage the hit object?")]
        [SerializeField] protected bool m_LineOfSight;
        [Tooltip("The duration of the explosion.")]
        [SerializeField] protected float m_Lifespan = 3;
        [Tooltip("The maximum number of objects that the explosions can detect.")]
        [SerializeField] protected int m_MaxCollisionCount = 100;
        [Tooltip("A set of AudioClips that can be played when the explosion occurs.")]
        [SerializeField] protected AudioClipSet m_ExplosionAudioClipSet = new AudioClipSet();
        [Tooltip("Unity event invoked when the explosion hits another object.")]
        [SerializeField] protected UnityFloatVector3Vector3GameObjectEvent m_OnImpactEvent;

        public bool ExplodeOnEnable { get { return m_ExplodeOnEnable; } set { m_ExplodeOnEnable = value; } }
        public float Radius { get { return m_Radius; } set { m_Radius = value; } }
        public float DamageAmount { get { return m_DamageAmount; } set { m_DamageAmount = value; } }
        public float ImpactForce { get { return m_ImpactForce; } set { m_ImpactForce = value; } }
        public int ImpactForceFrames { get { return m_ImpactForceFrames; } set { m_ImpactForceFrames = value; } }
        public LayerMask ImpactLayers { get { return m_ImpactLayers; } set { m_ImpactLayers = value; } }
        public bool LineOfSight { get { return m_LineOfSight; } set { m_LineOfSight = value; } }
        public float Lifespan { get { return m_Lifespan; } set { m_Lifespan = value; } }
        public AudioClipSet ExplosionAudioClipSet { get { return m_ExplosionAudioClipSet; } set { m_ExplosionAudioClipSet = value; } }
        public UnityFloatVector3Vector3GameObjectEvent OnImpactEvent { get { return m_OnImpactEvent; } set { m_OnImpactEvent = value; } }

        private GameObject m_GameObject;
        private Transform m_Transform;
        private HashSet<object> m_ObjectExplosions = new HashSet<object>();
        private Collider[] m_CollidersHit;
        private RaycastHit m_RaycastHit;

        /// <summary>
        /// Initialize the default values.
        /// </summary>
        private void Awake()
        {
            m_GameObject = gameObject;
            m_Transform = transform;
            m_CollidersHit = new Collider[m_MaxCollisionCount];
            AudioManager.Register(m_GameObject);
        }

        /// <summary>
        /// Explode if requested when the component is enabled.
        /// </summary>
        private void OnEnable()
        {
            if (m_ExplodeOnEnable) {
                Explode(m_DamageAmount, m_ImpactForce, m_ImpactForceFrames, null);
            }
        }

        /// <summary>
        /// Do the explosion.
        /// </summary>
        public void Explode()
        {
            Explode(m_DamageAmount, m_ImpactForce, m_ImpactForceFrames, null);
        }

        /// <summary>
        /// Do the explosion.
        /// </summary>
        /// <param name="damageAmount">The amount of damage to apply to the hit objects.</param>
        public void Explode(GameObject originator)
        {
            Explode(m_DamageAmount, m_ImpactForce, m_ImpactForceFrames, originator);
        }

        /// <summary>
        /// Do the explosion.
        /// </summary>
        /// <param name="damageAmount">The amount of damage to apply to the hit objects.</param>
        /// <param name="impactForce">The amount of force to apply to the hit object.</param>
        /// <param name="impactForceFrames">The number of frames to add the force to.</param>
        /// <param name="originator">The originator of the object.</param>
        public void Explode(float damageAmount, float impactForce, int impactForceFrames, GameObject originator)
        {
            Health health = null;
            Rigidbody colliderRigidbody = null;
            IForceObject forceObject = null;
            var hitCount = Physics.OverlapSphereNonAlloc(m_Transform.position, m_Radius, m_CollidersHit, m_ImpactLayers, QueryTriggerInteraction.Ignore);
#if UNITY_EDITOR
            if (hitCount == m_MaxCollisionCount) {
                Debug.LogWarning("Warning: The maximum number of colliders have been hit by " + m_GameObject.name + ". Consider increasing the Max Collision Count value.");
            }
#endif
            for (int i = 0; i < hitCount; ++i) {
                // A GameObject can contain multiple colliders. Prevent the explosion from occurring on the same GameObject multiple times.
                if (m_ObjectExplosions.Contains(m_CollidersHit[i].gameObject)) {
                    continue;
                }
                m_ObjectExplosions.Add(m_CollidersHit[i].gameObject);
                // The base character GameObject should only be checked once.
                if ((forceObject = m_CollidersHit[i].gameObject.GetCachedParentComponent<IForceObject>()) != null) {
                    if (m_ObjectExplosions.Contains(forceObject)) {
                        continue;
                    }
                    m_ObjectExplosions.Add(forceObject);
                }

                // OverlapSphere can return objects that are in a different room. Perform a cast to ensure the object is within the explosion range.
                if (m_LineOfSight) {
                    // Add a slight vertical offset to prevent a floor collider from getting in the way of the cast.
                    var position = m_Transform.TransformPoint(0, 0.1f, 0);
                    var direction = m_CollidersHit[i].transform.position - position;
                    if (Physics.Raycast(position - direction.normalized * 0.1f, direction, out m_RaycastHit, direction.magnitude, m_ImpactLayers, QueryTriggerInteraction.Ignore) &&
                        !(m_RaycastHit.transform.IsChildOf(m_CollidersHit[i].transform)
#if FIRST_PERSON_CONTROLLER
                        // The cast should not hit any colliders who are a child of the camera.
                        || m_RaycastHit.transform.gameObject.GetCachedParentComponent<FirstPersonController.Character.FirstPersonObjects>() != null
#endif
                        )) {
                        // If the collider is part of a character then ensure the head can't be hit.
                        var parentAnimator = m_CollidersHit[i].transform.gameObject.GetCachedParentComponent<Animator>();
                        if (parentAnimator != null && parentAnimator.isHuman) {
                            var head = parentAnimator.GetBoneTransform(HumanBodyBones.Head);
                            direction = head.position - position;
                            if (Physics.Raycast(position, direction, out m_RaycastHit, direction.magnitude, m_ImpactLayers, QueryTriggerInteraction.Ignore) &&
                                !m_RaycastHit.transform.IsChildOf(m_CollidersHit[i].transform) && !m_CollidersHit[i].transform.IsChildOf(m_RaycastHit.transform) &&
                                m_RaycastHit.transform.IsChildOf(m_Transform)
#if FIRST_PERSON_CONTROLLER
                                // The cast should not hit any colliders who are a child of the camera.
                                && m_RaycastHit.transform.gameObject.GetCachedParentComponent<FirstPersonController.Character.FirstPersonObjects>() == null
#endif
                                ) {
                                continue;
                            }
                        } else {
                            continue;
                        }
                    }
                }

                // The shield can absorb some (or none) of the damage from the explosion.
                var hitDamageAmount = damageAmount;
#if ULTIMATE_CHARACTER_CONTROLLER_MELEE
                ShieldCollider shieldCollider;
                if ((shieldCollider = m_CollidersHit[i].transform.gameObject.GetCachedComponent<ShieldCollider>()) != null) {
                    hitDamageAmount = shieldCollider.Shield.Damage(this, hitDamageAmount);
                }
#endif

                // ClosestPoint only works with a subset of collider types.
                Vector3 closestPoint;
                if (m_CollidersHit[i] is BoxCollider || m_CollidersHit[i] is SphereCollider || m_CollidersHit[i] is CapsuleCollider || (m_CollidersHit[i] is MeshCollider && (m_CollidersHit[i] as MeshCollider).convex)) {
                    closestPoint = m_CollidersHit[i].ClosestPoint(m_Transform.position);
                } else {
                    closestPoint = m_CollidersHit[i].ClosestPointOnBounds(m_Transform.position);
                }
                var hitDirection = closestPoint - m_Transform.position;

                // Allow a custom event to be received.
                EventHandler.ExecuteEvent<float, Vector3, Vector3, GameObject, object, Collider>(m_CollidersHit[i].transform.gameObject, "OnObjectImpact", hitDamageAmount, closestPoint, hitDirection * m_ImpactForce, originator, this, m_CollidersHit[i]);
                if (m_OnImpactEvent != null) {
                    m_OnImpactEvent.Invoke(hitDamageAmount, closestPoint, hitDirection * m_ImpactForce, originator);
                }

                // If the shield didn't absorb all of the damage then it should be applied to the character.
                if (hitDamageAmount > 0) {
                    // If the Health component exists it will apply an explosive force to the character/character in addition to deducting the health.
                    // Otherwise just apply the force to the character/rigidbody. 
                    if ((health = m_CollidersHit[i].gameObject.GetCachedParentComponent<Health>()) != null) {
                        // The further out the collider is, the less it is damaged.
                        var damageModifier = Mathf.Max(1 - (hitDirection.magnitude / m_Radius), 0.01f);
                        health.Damage(hitDamageAmount * damageModifier, m_Transform.position, hitDirection.normalized, impactForce * damageModifier, impactForceFrames, m_Radius, originator, this, null);
                    } else if (forceObject != null) {
                        var damageModifier = Mathf.Max(1 - (hitDirection.magnitude / m_Radius), 0.01f);
                        forceObject.AddForce(hitDirection.normalized * impactForce * damageModifier);
                    } else if ((colliderRigidbody = m_CollidersHit[i].gameObject.GetCachedComponent<Rigidbody>()) != null) {
                        colliderRigidbody.AddExplosionForce(impactForce * MathUtility.RigidbodyForceMultiplier, m_Transform.position, m_Radius);
                    }
                }
            }
            m_ObjectExplosions.Clear();

            // An audio clip can play when the object explodes.
            m_ExplosionAudioClipSet.PlayAudioClip(m_GameObject);

            Scheduler.Schedule(m_Lifespan, Destroy);
        }

        /// <summary>
        /// Place the object back in the ObjectPool.
        /// </summary>
        private void Destroy()
        {
            ObjectPool.Destroy(gameObject);
        }
    }
}