using System;
using System.Linq;
using Content.Shared.Physics;
using JetBrains.Annotations;
using Robust.Shared.GameObjects.Systems;
using Robust.Shared.Interfaces.GameObjects;
using Robust.Shared.Interfaces.Map;
using Robust.Shared.Interfaces.Physics;
using Robust.Shared.IoC;
using Robust.Shared.Map;
using Robust.Shared.Maths;

namespace Content.Server.GameObjects.EntitySystems
{
    /// <summary>
    /// Governs interactions during clicking on entities
    /// </summary>
    [UsedImplicitly]
    public class SharedInteractionSystem : EntitySystem
    {
        #pragma warning disable 649
        [Dependency] private readonly IMapManager _mapManager;
        [Dependency] private readonly IPhysicsManager _physicsManager;
        #pragma warning restore 649

        public const float InteractionRange = 2;
        public const float InteractionRangeSquared = InteractionRange * InteractionRange;

        /// <summary>
        ///     Checks that these coordinates are within a certain distance without any
        ///     entity that matches the collision mask obstructing them.
        ///     If the <paramref name="range"/> is zero or negative,
        ///     this method will only check if nothing obstructs the two sets of coordinates..
        /// </summary>
        /// <param name="coords">Set of coordinates to use.</param>
        /// <param name="otherCoords">Other set of coordinates to use.</param>
        /// <param name="range">maximum distance between the two sets of coordinates.</param>
        /// <param name="collisionMask">the mask to check for collisions</param>
        /// <param name="predicate">.</param>
        /// <param name="mapManager">Map manager containing the two GridIds.</param>
        /// <param name="insideBlockerValid">if coordinates inside obstructions count as obstructed or not</param>
        /// <returns>True if the two points are within a given range without being obstructed.</returns>
        public bool InRangeUnobstructed(MapCoordinates coords, Vector2 otherCoords, float range = InteractionRange,
            int collisionMask = (int)CollisionGroup.Impassable, Func<IEntity, bool> predicate = null, bool insideBlockerValid = false)
        {
            var dir = otherCoords - coords.Position;

            if (dir.LengthSquared.Equals(0f)) return true;
            if (range > 0f && !(dir.LengthSquared <= range * range)) return false;

            var ray = new CollisionRay(coords.Position, dir.Normalized, collisionMask);
            var rayResults = _physicsManager.IntersectRayWithPredicate(coords.MapId, ray, dir.Length, predicate).ToList();
            if(rayResults.Count == 0 || (insideBlockerValid && rayResults.Count > 0 && (rayResults[0].HitPos - otherCoords).Length < 1f))
            {

                if (_mapManager.TryFindGridAt(coords, out var mapGrid) && mapGrid != null)
                {
                    var srcPos = mapGrid.MapToGrid(coords);
                    var destPos = new GridCoordinates(otherCoords, mapGrid);
                    if (srcPos.InRange(_mapManager, destPos, range))
                    {
                        return true;
                    }
                }

            }
            return false;
        }

        /// <summary>
        ///     Checks that these coordinates are within a certain distance without any
        ///     entity that matches the collision mask obstructing them.
        ///     If the <paramref name="range"/> is zero or negative,
        ///     this method will only check if nothing obstructs the two sets of coordinates..
        /// </summary>
        /// <param name="coords">Set of coordinates to use.</param>
        /// <param name="otherCoords">Other set of coordinates to use.</param>
        /// <param name="range">maximum distance between the two sets of coordinates.</param>
        /// <param name="collisionMask">the mask to check for collisions</param>
        /// <param name="ignoredEnt">the entity to be ignored when checking for collisions.</param>
        /// <param name="mapManager">Map manager containing the two GridIds.</param>
        /// <param name="insideBlockerValid">if coordinates inside obstructions count as obstructed or not</param>
        /// <returns>True if the two points are within a given range without being obstructed.</returns>
        public bool InRangeUnobstructed(MapCoordinates coords, Vector2 otherCoords, float range = InteractionRange,
            int collisionMask = (int)CollisionGroup.Impassable, IEntity ignoredEnt = null, bool insideBlockerValid = false) =>
            InRangeUnobstructed(coords, otherCoords, range, collisionMask,
                ignoredEnt == null ? null : (Func<IEntity, bool>)(entity => ignoredEnt == entity), insideBlockerValid);
    }
}