using System.Linq;
using System.Numerics;
using Content.Client.Decals.Overlays;
using Content.Shared.Decals;
using Content.Shared.Maps;
using Robust.Client.GameObjects;
using Robust.Client.Graphics;
using Robust.Shared.GameStates;
using Robust.Shared.Map;
using Robust.Shared.Map.Components;

namespace Content.Client.Decals
{
    public sealed partial class DecalSystem : SharedDecalSystem
    {
        [Dependency] private IOverlayManager _overlayManager = default!;
        [Dependency] private SpriteSystem _sprites = default!;
        [Dependency] private SharedMapSystem _mapSystem = default!;
        [Dependency] private SharedTransformSystem _transform = default!;
        [Dependency] private TurfSystem _turf = default!;
        [Dependency] private EntityQuery<MapGridComponent> _gridQuery;

        private DecalOverlay? _overlay;

        public override void Initialize()
        {
            base.Initialize();

            _overlay = new DecalOverlay(_sprites, EntityManager, ProtoMan);
            _overlayManager.AddOverlay(_overlay);
        }

        [SubscribeLocalEvent]
        private void OnDecalAfterState(EntityUid uid, DecalChunkComponent component, ref AfterAutoHandleStateEvent args)
        {
            component.NextPredictedDecal = ushort.MaxValue;
        }

        protected override void OnDecalPlacementRequest(RequestDecalPlacementEvent ev, EntitySessionEventArgs eventArgs)
        {
            var coordinates = GetCoordinates(ev.Coordinates);
            if (!coordinates.IsValid(EntityManager))
                return;

            TryAddDecal(ev.Decal, coordinates, out _);
        }

        public override bool TryAddDecal(Decal decal, EntityCoordinates coordinates, out DecalIndex decalId)
        {
            decalId = default;

            if (!ProtoMan.HasIndex<DecalPrototype>(decal.Id))
                return false;

            var gridUid = _transform.GetGrid(coordinates);
            if (gridUid == null || !_gridQuery.TryComp(gridUid.Value, out var grid))
                return false;

            if (_turf.IsSpace(_mapSystem.GetTileRef(gridUid.Value, grid, coordinates)))
                return false;

            var chunk = ChunkEntities.GetOrCreateChunk(gridUid.Value, ChunkEntitySystem.GetChunkIndices(decal.Coordinates));
            var decals = EnsureComp<DecalChunkComponent>(chunk.Owner);

            if (!TryAllocatePredictedDecalId(decals, out var predictedDecalId))
                return false;

            decals.Decals[predictedDecalId] = decal;
            DirtyField(chunk.Owner, decals, nameof(DecalChunkComponent.Decals));
            decalId = new DecalIndex(ChunkEntitySystem.GetChunkIndices(decal.Coordinates), predictedDecalId);
            return true;
        }

        protected override void OnDecalRemovalRequest(RequestDecalRemovalEvent ev, EntitySessionEventArgs eventArgs)
        {
            var coordinates = GetCoordinates(ev.Coordinates);
            if (!coordinates.IsValid(EntityManager))
                return;

            var gridUid = _transform.GetGrid(coordinates);
            if (gridUid == null)
                return;

            foreach (var (decalId, _) in GetDecalsInRange(gridUid.Value, ev.Coordinates.Position))
            {
                RemoveDecal(gridUid.Value, decalId);
            }
        }

        private bool TryAllocatePredictedDecalId(DecalChunkComponent decals, out ushort decalId)
        {
            // Iterate top-down to find next free index.
            for (var i = 0; i < DecalChunkComponent.PredictedDecalCount; i++)
            {
                var next = decals.NextPredictedDecal;
                decals.NextPredictedDecal = next == DecalChunkComponent.MinPredictedDecalId
                    ? ushort.MaxValue
                    : (ushort) (next - 1);

                if (decals.Decals.ContainsKey(next))
                    continue;

                decalId = next;
                return true;
            }

            decalId = default;
            return false;
        }

        public override bool RemoveDecal(EntityUid gridId, DecalIndex decal)
        {
            if (!ChunkEntities.TryGetChunk(gridId, decal.Chunk, out var chunkEnt) ||
                !DecalChunkQuery.TryComp(chunkEnt.Value.Owner, out var decals) ||
                !decals.Decals.Remove(decal.Id))
            {
                return false;
            }

            DirtyField(chunkEnt.Value.Owner, decals, nameof(DecalChunkComponent.Decals));
            return true;
        }

        public void ToggleOverlay()
        {
            if (_overlay == null)
                return;

            if (_overlayManager.HasOverlay<DecalOverlay>())
            {
                _overlayManager.RemoveOverlay(_overlay);
            }
            else
            {
                _overlayManager.AddOverlay(_overlay);
            }
        }

        public override void Shutdown()
        {
            base.Shutdown();

            if (_overlay == null)
                return;

            _overlayManager.RemoveOverlay(_overlay);
        }
    }
}