using Content.Shared.Access.Components;
using Content.Shared.Damage;
using Content.Shared.Doors.Components;
using Content.Shared.Examine;
using Content.Shared.Hands.Components;
using Content.Shared.Interaction;
using Content.Shared.Stunnable;
using Robust.Shared.Audio;
using Robust.Shared.GameStates;
using Robust.Shared.Physics;
using Robust.Shared.Physics.Dynamics;
using Robust.Shared.Timing;
using System.Linq;

namespace Content.Shared.Doors.Systems;

public abstract class SharedDoorSystem : EntitySystem
{
    [Dependency] private readonly SharedPhysicsSystem _physicsSystem = default!;
    [Dependency] private readonly DamageableSystem _damageableSystem = default!;
    [Dependency] private readonly SharedStunSystem _stunSystem = default!;
    [Dependency] protected readonly IGameTiming GameTiming = default!;

    /// <summary>
    ///     A body must have an intersection percentage larger than this in order to be considered as colliding with a
    ///     door. Used for safety close-blocking and crushing.
    /// </summary>
    /// <remarks>
    ///     The intersection percentage relies on WORLD AABBs. So if this is too small, and the grid is rotated 45
    ///     degrees, then an entity outside of the airlock may be crushed.
    /// </remarks>
    public const float IntersectPercentage = 0.2f;

    /// <summary>
    ///     A set of doors that are currently opening, closing, or just queued to open/close after some delay.
    /// </summary>
    private readonly HashSet<DoorComponent> _activeDoors = new();

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

        SubscribeLocalEvent<DoorComponent, ComponentInit>(OnInit);
        SubscribeLocalEvent<DoorComponent, ComponentRemove>(OnRemove);

        SubscribeLocalEvent<DoorComponent, ComponentGetState>(OnGetState);
        SubscribeLocalEvent<DoorComponent, ComponentHandleState>(OnHandleState);

        SubscribeLocalEvent<DoorComponent, ActivateInWorldEvent>(OnActivate);
        SubscribeLocalEvent<DoorComponent, ExaminedEvent>(OnExamine);

        SubscribeLocalEvent<DoorComponent, StartCollideEvent>(HandleCollide);
        SubscribeLocalEvent<DoorComponent, PreventCollideEvent>(PreventCollision);
    }

    private void OnInit(EntityUid uid, DoorComponent door, ComponentInit args)
    {
        if (door.NextStateChange != null)
            _activeDoors.Add(door);
        else
        {
            // Make sure doors are not perpetually stuck opening or closing.
            if (door.State == DoorState.Opening)
            {
                // force to open.
                door.State = DoorState.Open;
                door.Partial = false;
            }
            if (door.State == DoorState.Closing)
            {
                // force to closed.
                door.State = DoorState.Closed;
                door.Partial = false;
            }
        }

        // should this door have collision and the like enabled?
        var collidable = door.State == DoorState.Closed
            || door.State == DoorState.Closing && door.Partial
            || door.State == DoorState.Opening && !door.Partial;

        SetCollidable(uid, collidable, door);
        UpdateAppearance(uid, door);
    }

    private void OnRemove(EntityUid uid, DoorComponent door, ComponentRemove args)
    {
        _activeDoors.Remove(door);
    }

    #region StateManagement
    private void OnGetState(EntityUid uid, DoorComponent door, ref ComponentGetState args)
    {
        args.State = new DoorComponentState(door);
    }

    private void OnHandleState(EntityUid uid, DoorComponent door, ref ComponentHandleState args)
    {
        if (args.Current is not DoorComponentState state)
            return;

        door.CurrentlyCrushing = new(state.CurrentlyCrushing);
        door.State = state.DoorState;
        door.NextStateChange = state.NextStateChange;
        door.Partial = state.Partial;

        if (state.NextStateChange == null)
            _activeDoors.Remove(door);
        else
            _activeDoors.Add(door);

        RaiseLocalEvent(uid, new DoorStateChangedEvent(door.State), false);
        UpdateAppearance(uid, door);
    }

    protected void SetState(EntityUid uid, DoorState state, DoorComponent? door = null)
    {
        if (!Resolve(uid, ref door))
            return;

        switch (state)
        {
            case DoorState.Opening:
                _activeDoors.Add(door);
                door.NextStateChange = GameTiming.CurTime + door.OpenTimeOne;
                break;

            case DoorState.Closing:
                _activeDoors.Add(door);
                door.NextStateChange = GameTiming.CurTime + door.CloseTimeOne;
                break;

            case DoorState.Denying:
                _activeDoors.Add(door);
                door.NextStateChange = GameTiming.CurTime + door.DenyDuration;
                break;

            case DoorState.Emagging:
                _activeDoors.Add(door);
                door.NextStateChange = GameTiming.CurTime + door.EmagDuration;
                break;

            case DoorState.Open:
            case DoorState.Closed:
                door.Partial = false;
                if (door.NextStateChange == null)
                    _activeDoors.Remove(door);
                break;
        }

        door.State = state;
        door.Dirty();
        RaiseLocalEvent(uid, new DoorStateChangedEvent(state), false);
        UpdateAppearance(uid, door);
    }

    protected virtual void UpdateAppearance(EntityUid uid, DoorComponent? door = null)
    {
        if (!Resolve(uid, ref door))
            return;

        if (!TryComp(uid, out AppearanceComponent? appearance))
            return;

        appearance.SetData(DoorVisuals.State, door.State);
    }
    #endregion

    #region Interactions
    protected virtual void OnActivate(EntityUid uid, DoorComponent door, ActivateInWorldEvent args)
    {
        // avoid client-mispredicts, as the server will definitely handle this event
        args.Handled = true; 
    }

    private void OnExamine(EntityUid uid, DoorComponent door, ExaminedEvent args)
    {
        if (door.State == DoorState.Welded)
            args.PushText(Loc.GetString("door-component-examine-is-welded"));
    }

    /// <summary>
    ///     Update the door state/visuals and play an access denied sound when a user without access interacts with the
    ///     door.
    /// </summary>
    public void Deny(EntityUid uid, DoorComponent? door = null, EntityUid? user = null, bool predicted = false)
    {
        if (!Resolve(uid, ref door))
            return;

        if (door.State != DoorState.Closed)
            return;

        // might not be able to deny without power or some other blocker.
        var ev = new BeforeDoorDeniedEvent();
        RaiseLocalEvent(uid, ev, false);
        if (ev.Cancelled)
            return;

        SetState(uid, DoorState.Denying, door);

        if (door.DenySound != null)
            PlaySound(uid, door.DenySound.GetSound(), AudioParams.Default.WithVolume(-3), user, predicted);
    }

    public bool TryToggleDoor(EntityUid uid, DoorComponent? door = null, EntityUid? user = null, bool predicted = false)
    {
        if (!Resolve(uid, ref door))
            return false;

        if (door.State == DoorState.Closed)
        {
            return TryOpen(uid, door, user, predicted);
        }
        else if (door.State == DoorState.Open)
        {
            return TryClose(uid, door, user, predicted);
        }

        return false;
    }
    #endregion

    #region Opening
    public bool TryOpen(EntityUid uid, DoorComponent? door = null, EntityUid? user = null, bool predicted = false)
    {
        if (!Resolve(uid, ref door))
            return false;

        if (!CanOpen(uid, door, user, false))
            return false;

        StartOpening(uid, door, user, predicted);

        return true;
    }

    public bool CanOpen(EntityUid uid, DoorComponent? door = null, EntityUid? user = null, bool quiet = true)
    {
        if (!Resolve(uid, ref door))
            return false;

        if (door.State == DoorState.Welded)
            return false;

        var ev = new BeforeDoorOpenedEvent();
        RaiseLocalEvent(uid, ev, false);
        if (ev.Cancelled)
            return false;

        if (!HasAccess(uid, user))
        {
            if (!quiet)
                Deny(uid, door);
            return false;
        }

        return true;
    }

    public virtual void StartOpening(EntityUid uid, DoorComponent? door = null, EntityUid? user = null, bool predicted = false)
    {
        if (!Resolve(uid, ref door))
            return;

        SetState(uid, DoorState.Opening, door);

        if (door.OpenSound != null)
            PlaySound(uid, door.OpenSound.GetSound(), AudioParams.Default.WithVolume(-5), user, predicted);

        // I'm not sure what the intent here is/was? It plays a sound if the user is opening a door with a hands
        // component, but no actual hands!? What!? Is this the sound of them head-butting the door to get it to open??
        // I'm 99% sure something is wrong here, but I kind of want to keep it this way.

        if (user != null && TryComp(user.Value, out SharedHandsComponent? hands) && hands.Hands.Count == 0)
            PlaySound(uid, door.TryOpenDoorSound.GetSound(), AudioParams.Default.WithVolume(-2), user, predicted);
    }

    /// <summary>
    /// Called when the door is partially opened. The door becomes transparent and stops colliding with entities.
    /// </summary>
    public void OnPartialOpen(EntityUid uid, DoorComponent? door = null)
    {
        if (!Resolve(uid, ref door))
            return;

        SetCollidable(uid, false, door);
        door.Partial = true;
        door.NextStateChange = GameTiming.CurTime + door.CloseTimeTwo;
        _activeDoors.Add(door);
        door.Dirty();

    }
    #endregion

    #region Closing
    public bool TryClose(EntityUid uid, DoorComponent? door = null, EntityUid? user = null, bool predicted = false)
    {
        if (!Resolve(uid, ref door))
            return false;

        if (!CanClose(uid, door, user, false))
            return false;

        StartClosing(uid, door, user, predicted);
        return true;
    }

    public bool CanClose(EntityUid uid, DoorComponent? door = null, EntityUid? user = null, bool quiet = true)
    {
        if (!Resolve(uid, ref door))
            return false;

        var ev = new BeforeDoorClosedEvent(door.PerformCollisionCheck);
        RaiseLocalEvent(uid, ev, false);
        if (ev.Cancelled)
            return false;

        if (!HasAccess(uid, user))
            return false;

        return !ev.PerformCollisionCheck || !GetColliding(uid).Any();
    }

    public virtual void StartClosing(EntityUid uid, DoorComponent? door = null, EntityUid? user = null, bool predicted = false)
    {
        if (!Resolve(uid, ref door))
            return;

        SetState(uid, DoorState.Closing, door);

        if (door.CloseSound != null)
            PlaySound(uid, door.CloseSound.GetSound(), AudioParams.Default.WithVolume(-5), user, predicted);
    }

    /// <summary>
    /// Called when the door is partially closed. This is when the door becomes "solid". If this process fails (e.g., a
    /// mob entered the door as it was closing), then this returns false. Otherwise, returns true;
    /// </summary>
    public bool OnPartialClose(EntityUid uid, DoorComponent? door = null, PhysicsComponent? physics = null)
    {
        if (!Resolve(uid, ref door, ref physics))
            return false;

        door.Partial = true;
        door.Dirty();

        // Make sure no entity waled into the airlock when it started closing.
        if (!CanClose(uid, door))
        {
            door.NextStateChange = GameTiming.CurTime + door.OpenTimeTwo;
            door.State = DoorState.Opening;
            UpdateAppearance(uid, door);
            return false;
        }

        SetCollidable(uid, true, door, physics);
        door.NextStateChange = GameTiming.CurTime + door.CloseTimeTwo;
        _activeDoors.Add(door);

        // Crush any entities. Note that we don't check airlock safety here. This should have been checked before
        // the door closed.
        Crush(uid, door, physics);
        return true;
    }
    #endregion

    #region Collisions
    protected virtual void SetCollidable(EntityUid uid, bool collidable,
        DoorComponent? door = null,
        PhysicsComponent? physics = null,
        OccluderComponent? occluder = null)
    {
        if (!Resolve(uid, ref door))
            return;

        if (Resolve(uid, ref physics, false))
            physics.CanCollide = collidable;

        if (!collidable)
            door.CurrentlyCrushing.Clear();

        if (door.Occludes && Resolve(uid, ref occluder, false))
            occluder.Enabled = collidable;
    }

    /// <summary>
    /// Crushes everyone colliding with us by more than <see cref="IntersectPercentage"/>%.
    /// </summary>
    public void Crush(EntityUid uid, DoorComponent? door = null, PhysicsComponent? physics = null)
    {
        if (!Resolve(uid, ref door))
            return;

        if (!door.CanCrush)
            return;

        // Find entities and apply curshing effects
        var stunTime = door.DoorStunTime + door.OpenTimeOne;
        foreach (var entity in GetColliding(uid, physics))
        {
            door.CurrentlyCrushing.Add(entity);
            if (door.CrushDamage != null)
                _damageableSystem.TryChangeDamage(entity, door.CrushDamage);

            _stunSystem.TryParalyze(entity, stunTime, true);
        }

        if (door.CurrentlyCrushing.Count == 0)
            return;

        // queue the door to open so that the player is no longer stunned once it has FINISHED opening.
        door.NextStateChange = GameTiming.CurTime + door.DoorStunTime;
        door.Partial = false;
    }

    /// <summary>
    ///     Get all entities that collide with this door by more than <see cref="IntersectPercentage"/> percent.\
    /// </summary>
    public IEnumerable<EntityUid> GetColliding(EntityUid uid, PhysicsComponent? physics = null)
    {
        if (!Resolve(uid, ref physics))
            yield break;

        // TODO SLOTH fix electro's code.
        var doorAABB = physics.GetWorldAABB();

        foreach (var otherPhysics in _physicsSystem.GetCollidingEntities(Transform(uid).MapID, doorAABB))
        {
            if (otherPhysics == physics)
                continue;

            if (!otherPhysics.CanCollide)
                continue;

            if ((physics.CollisionMask & otherPhysics.CollisionLayer) == 0
                && (otherPhysics.CollisionMask & physics.CollisionLayer) == 0)
                continue;

            if (otherPhysics.GetWorldAABB().IntersectPercentage(doorAABB) < IntersectPercentage)
                continue;

            yield return otherPhysics.Owner;
        }
    }

    private void PreventCollision(EntityUid uid, DoorComponent component, PreventCollideEvent args)
    {
        if (component.CurrentlyCrushing.Contains(args.BodyB.Owner))
        {
            args.Cancel();
        }
    }

    protected virtual void HandleCollide(EntityUid uid, DoorComponent door, StartCollideEvent args)
    {
        // TODO ACCESS READER move access reader to shared and predict door opening/closing
        // Then this can be moved to the shared system without mispredicting.
    }
    #endregion

    #region Access
    public virtual bool HasAccess(EntityUid uid, EntityUid? user = null, AccessReaderComponent? access = null)
    {
        // TODO network AccessComponent for predicting doors

        // Currently all door open/close & door-bumper collision stuff is done server side.
        // so this return value means nothing.
        return true;
    }

    /// <summary>
    ///     Determines the base access behavior of all doors on the station.
    /// </summary>
    public AccessTypes AccessType = AccessTypes.Id;

    /// <summary>
    /// How door access should be handled.
    /// </summary>
    public enum AccessTypes
    {
        /// <summary> ID based door access. </summary>
        Id,
        /// <summary>
        /// Allows everyone to open doors, except external which airlocks are still handled with ID's
        /// </summary>
        AllowAllIdExternal,
        /// <summary>
        /// Allows everyone to open doors, except external airlocks which are never allowed, even if the user has
        /// ID access.
        /// </summary>
        AllowAllNoExternal,
        /// <summary> Allows everyone to open all doors. </summary>
        AllowAll
    }
    #endregion

    #region Updating
    /// <summary>
    ///     Schedule an open or closed door to progress to the next state after some time.
    /// </summary>
    /// <remarks>
    ///     If the requested delay is null or non-positive, this will make the door stay open or closed indefinitely.
    /// </remarks>
    public void SetNextStateChange(EntityUid uid, TimeSpan? delay, DoorComponent? door = null)
    {
        if (!Resolve(uid, ref door, false))
            return;

        // If the door is not currently just open or closed, it is busy doing something else (or welded shut). So in
        // that case we do nothing.
        if (door.State != DoorState.Open && door.State != DoorState.Closed)
            return;

        // Is this trying to prevent an update? (e.g., cancel an auto-close)
        if (delay == null || delay.Value <= TimeSpan.Zero)
        {
            door.NextStateChange = null;
            _activeDoors.Remove(door);
            return;
        }

        door.NextStateChange = GameTiming.CurTime + delay.Value;
        _activeDoors.Add(door);
    }

    /// <summary>
    ///     Iterate over active doors and progress them to the next state if they need to be updated.
    /// </summary>
    public override void Update(float frameTime)
    {
        var time = GameTiming.CurTime;

        foreach (var door in _activeDoors.ToList())
        {
            if (door.Deleted || door.NextStateChange == null)
            {
                _activeDoors.Remove(door);
                continue;
            }

            if (Paused(door.Owner))
                continue;

            if (door.NextStateChange.Value < time)
                NextState(door, time);
        }
    }

    /// <summary>
    ///     Makes a door proceed to the next state (if applicable).
    /// </summary>
    private void NextState(DoorComponent door, TimeSpan time)
    {
        door.NextStateChange = null;

        if (door.CurrentlyCrushing.Count > 0)
            // This is a closed door that is crushing people and needs to auto-open. Note that we don't check "can open"
            // here. The door never actually finished closing and we don't want people to get stuck inside of doors.
            StartOpening(door.Owner, door, predicted: true);

        switch (door.State)
        {
            case DoorState.Opening:
                // Either fully or partially open this door.
                if (door.Partial)
                    SetState(door.Owner, DoorState.Open, door);
                else
                    OnPartialOpen(door.Owner, door);

                break;

            case DoorState.Closing:
                // Either fully or partially close this door.
                if (door.Partial)
                    SetState(door.Owner, DoorState.Closed, door);
                else
                    OnPartialClose(door.Owner, door);

                break;

            case DoorState.Denying:
                // Finish denying entry and return to the closed state.
                SetState(door.Owner, DoorState.Closed, door);
                break;

            case DoorState.Emagging:
                StartOpening(door.Owner, door);
                break;

            case DoorState.Open:
                // This door is open, and queued for an auto-close.
                if (!TryClose(door.Owner, door, predicted: true))
                {
                    // The door failed to close (blocked?). Try again in one second.
                    door.NextStateChange = time + TimeSpan.FromSeconds(1);
                }
                break;

            case DoorState.Welded:
                // A welded door? This should never have been active in the first place.
                Logger.Error($"Welded door was in the list of active doors. Door: {ToPrettyString(door.Owner)}");
                break;
        }
    }
    #endregion

    protected abstract void PlaySound(EntityUid uid, string sound, AudioParams audioParams, EntityUid? predictingPlayer, bool predicted);
}
