using System.Diagnostics.CodeAnalysis;
using System.Numerics;
using Content.Shared.Administration.Logs;
using Content.Shared.Alert;
using Content.Shared.Audio;
using Content.Shared.Damage.Components;
using Content.Shared.Database;
using Content.Shared.Gravity;
using Content.Shared.Hands;
using Content.Shared.Inventory;
using Content.Shared.Inventory.Events;
using Content.Shared.Item.ItemToggle.Components;
using Content.Shared.Popups;
using Content.Shared.Projectiles;
using Content.Shared.Standing;
using Content.Shared.Weapons.Ranged.Components;
using Content.Shared.Weapons.Ranged.Events;
using Robust.Shared.Audio.Systems;
using Robust.Shared.Network;
using Robust.Shared.Physics.Components;
using Robust.Shared.Physics.Systems;
using Robust.Shared.Random;
using Robust.Shared.Timing;

namespace Content.Shared.Weapons.Reflect;

/// <summary>
/// This handles reflecting projectiles and hitscan shots.
/// </summary>
public sealed class ReflectSystem : EntitySystem
{
    [Dependency] private readonly INetManager _netManager = default!;
    [Dependency] private readonly IRobustRandom _random = default!;
    [Dependency] private readonly ISharedAdminLogManager _adminLogger = default!;
    [Dependency] private readonly IGameTiming _gameTiming = default!;
    [Dependency] private readonly SharedPopupSystem _popup = default!;
    [Dependency] private readonly SharedPhysicsSystem _physics = default!;
    [Dependency] private readonly SharedAudioSystem _audio = default!;
    [Dependency] private readonly SharedTransformSystem _transform = default!;
    [Dependency] private readonly InventorySystem _inventorySystem = default!;
    [Dependency] private readonly SharedGravitySystem _gravity = default!;
    [Dependency] private readonly StandingStateSystem _standing = default!;
    [Dependency] private readonly AlertsSystem _alerts = default!;

    [ValidatePrototypeId<AlertPrototype>]
    private const string DeflectingAlert = "Deflecting";

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

        SubscribeLocalEvent<ReflectComponent, ProjectileReflectAttemptEvent>(OnObjectReflectProjectileAttempt);
        SubscribeLocalEvent<ReflectComponent, HitScanReflectAttemptEvent>(OnObjectReflectHitscanAttempt);
        SubscribeLocalEvent<ReflectComponent, GotEquippedEvent>(OnReflectEquipped);
        SubscribeLocalEvent<ReflectComponent, GotUnequippedEvent>(OnReflectUnequipped);
        SubscribeLocalEvent<ReflectComponent, GotEquippedHandEvent>(OnReflectHandEquipped);
        SubscribeLocalEvent<ReflectComponent, GotUnequippedHandEvent>(OnReflectHandUnequipped);
        SubscribeLocalEvent<ReflectComponent, ItemToggledEvent>(OnToggleReflect);

        SubscribeLocalEvent<ReflectUserComponent, ProjectileReflectAttemptEvent>(OnUserProjectileReflectAttempt);
        SubscribeLocalEvent<ReflectUserComponent, HitScanReflectAttemptEvent>(OnUserHitscanReflectAttempt);
    }

    private void OnUserHitscanReflectAttempt(Entity<ReflectUserComponent> user, ref HitScanReflectAttemptEvent args)
    {
        if (args.Reflected)
            return;

        if (!UserCanReflect(user, out var bestReflectorUid))
            return;

        if (!TryReflectHitscan(user.Owner, bestReflectorUid.Value, args.Shooter, args.SourceItem, args.Direction, out var dir))
            return;

        args.Direction = dir.Value;
        args.Reflected = true;
    }

    private void OnUserProjectileReflectAttempt(Entity<ReflectUserComponent> user, ref ProjectileReflectAttemptEvent args)
    {
        if (args.Cancelled)
            return;

        if (!TryComp<ReflectiveComponent>(args.ProjUid, out var reflectiveComponent))
            return;

        if (!UserCanReflect(user, out var bestReflectorUid, (args.ProjUid, reflectiveComponent)))
            return;

        if (!TryReflectProjectile(user, bestReflectorUid.Value, (args.ProjUid, args.Component)))
            return;

        args.Cancelled = true;
    }

    private void OnObjectReflectHitscanAttempt(Entity<ReflectComponent> obj, ref HitScanReflectAttemptEvent args)
    {
        if (args.Reflected || (obj.Comp.Reflects & args.Reflective) == 0x0)
            return;

        if (!TryReflectHitscan(obj, obj, args.Shooter, args.SourceItem, args.Direction, out var dir))
            return;

        args.Direction = dir.Value;
        args.Reflected = true;
    }

    private void OnObjectReflectProjectileAttempt(Entity<ReflectComponent> obj, ref ProjectileReflectAttemptEvent args)
    {
        if (args.Cancelled)
            return;

        if (!TryReflectProjectile(obj, obj, (args.ProjUid, args.Component)))
            return;

        args.Cancelled = true;
    }

    /// <summary>
    /// Can a user reflect something that's hit them? Returns true if so, and the best reflector available in the user's equipment.
    /// </summary>
    private bool UserCanReflect(Entity<ReflectUserComponent> user, [NotNullWhen(true)] out Entity<ReflectComponent>? bestReflector, Entity<ReflectiveComponent>? projectile = null)
    {
        bestReflector = null;

        foreach (var entityUid in _inventorySystem.GetHandOrInventoryEntities(user.Owner, SlotFlags.WITHOUT_POCKET))
        {
            if (!TryComp<ReflectComponent>(entityUid, out var comp))
                continue;

            if (!comp.Enabled)
                continue;

            if (bestReflector != null && bestReflector.Value.Comp.ReflectProb >= comp.ReflectProb)
                continue;

            if (projectile != null && (comp.Reflects & projectile.Value.Comp.Reflective) == 0x0)
                continue;

            bestReflector = (entityUid, comp);
        }

        return bestReflector != null;
    }

    private bool TryReflectProjectile(EntityUid user, Entity<ReflectComponent> reflector, Entity<ProjectileComponent> projectile)
    {
        if (
            // Is it on?
            !reflector.Comp.Enabled ||
            // Is the projectile deflectable?
            !TryComp<ReflectiveComponent>(projectile, out var reflective) ||
            // Does the deflector deflect the type of projecitle?
            (reflector.Comp.Reflects & reflective.Reflective) == 0x0 ||
            // Is the projectile correctly set up with physics?
            !TryComp<PhysicsComponent>(projectile, out var physics) ||
            // If the user of the reflector is a mob with stamina, is it capable of deflecting?
            TryComp<StaminaComponent>(user, out var staminaComponent) && staminaComponent.Critical ||
            _standing.IsDown(reflector)
        )
            return false;

        // If this dice roll fails, the shot isn't deflected
        if (!_random.Prob(GetReflectChance(reflector)))
            return false;

        // Below handles what happens after being deflected.
        var rotation = _random.NextAngle(-reflector.Comp.Spread / 2, reflector.Comp.Spread / 2).Opposite();
        var existingVelocity = _physics.GetMapLinearVelocity(projectile, component: physics);
        var relativeVelocity = existingVelocity - _physics.GetMapLinearVelocity(user);
        var newVelocity = rotation.RotateVec(relativeVelocity);

        // Have the velocity in world terms above so need to convert it back to local.
        var difference = newVelocity - existingVelocity;

        _physics.SetLinearVelocity(projectile, physics.LinearVelocity + difference, body: physics);

        var locRot = Transform(projectile).LocalRotation;
        var newRot = rotation.RotateVec(locRot.ToVec());
        _transform.SetLocalRotation(projectile, newRot.ToAngle());

        if (_netManager.IsServer)
        {
            _popup.PopupEntity(Loc.GetString("reflect-shot"), user);
            _audio.PlayPvs(reflector.Comp.SoundOnReflect, user, AudioHelpers.WithVariation(0.05f, _random));
        }

        _adminLogger.Add(LogType.BulletHit, LogImpact.Medium, $"{ToPrettyString(user)} reflected {ToPrettyString(projectile)} from {ToPrettyString(projectile.Comp.Weapon)} shot by {projectile.Comp.Shooter}");

        projectile.Comp.Shooter = user;
        projectile.Comp.Weapon = user;
        Dirty(projectile);

        return true;
    }

    private bool TryReflectHitscan(
        EntityUid user,
        Entity<ReflectComponent> reflector,
        EntityUid? shooter,
        EntityUid shotSource,
        Vector2 direction,
        [NotNullWhen(true)] out Vector2? newDirection)
    {
        if (
            // Is the reflector enabled?
            !reflector.Comp.Enabled ||
            // If the user is a mob with stamina, is it capable of deflecting?
            TryComp<StaminaComponent>(user, out var staminaComponent) && staminaComponent.Critical ||
            _standing.IsDown(user))
        {
            newDirection = null;
            return false;
        }

        // If this dice roll fails, the shot is not deflected.
        if (!_random.Prob(GetReflectChance(reflector)))
        {
            newDirection = null;
            return false;
        }

        // Below handles what happens after being deflected.
        if (_netManager.IsServer)
        {
            _popup.PopupEntity(Loc.GetString("reflect-shot"), user);
            _audio.PlayPvs(reflector.Comp.SoundOnReflect, user, AudioHelpers.WithVariation(0.05f, _random));
        }

        var spread = _random.NextAngle(-reflector.Comp.Spread / 2, reflector.Comp.Spread / 2);
        newDirection = -spread.RotateVec(direction);

        if (shooter != null)
            _adminLogger.Add(LogType.HitScanHit, LogImpact.Medium, $"{ToPrettyString(user)} reflected hitscan from {ToPrettyString(shotSource)} shot by {ToPrettyString(shooter.Value)}");
        else
            _adminLogger.Add(LogType.HitScanHit, LogImpact.Medium, $"{ToPrettyString(user)} reflected hitscan from {ToPrettyString(shotSource)}");

        return true;
    }

    private float GetReflectChance(Entity<ReflectComponent> reflector)
    {
        /*
         *  The rules of deflection are as follows:
         *  If you innately reflect things via magic, biology etc., you always have a full chance.
         *  If you are standing up and standing still, you're prepared to deflect and have full chance.
         *  If you have velocity, your deflection chance depends on your velocity, clamped.
         *  If you are floating, your chance is the minimum value possible.
         */

        if (reflector.Comp.Innate)
            return reflector.Comp.ReflectProb;

        if (_gravity.IsWeightless(reflector))
            return reflector.Comp.MinReflectProb;

        if (!TryComp<PhysicsComponent>(reflector, out var reflectorPhysics))
            return reflector.Comp.ReflectProb;

        return MathHelper.Lerp(
            reflector.Comp.MinReflectProb,
            reflector.Comp.ReflectProb,
            // Inverse progression between velocities fed in as progression between probabilities. We go high -> low so the output here needs to be _inverted_.
            1 - Math.Clamp((reflectorPhysics.LinearVelocity.Length() - reflector.Comp.VelocityBeforeNotMaxProb) / (reflector.Comp.VelocityBeforeMinProb - reflector.Comp.VelocityBeforeNotMaxProb), 0, 1)
        );
    }

    private void OnReflectEquipped(Entity<ReflectComponent> reflector, ref GotEquippedEvent args)
    {
        if (_gameTiming.ApplyingState)
            return;

        EnsureComp<ReflectUserComponent>(args.Equipee);

        if (reflector.Comp.Enabled)
            EnableAlert(args.Equipee);
    }

    private void OnReflectUnequipped(Entity<ReflectComponent> reflector, ref GotUnequippedEvent args)
    {
        RefreshReflectUser(args.Equipee);
    }

    private void OnReflectHandEquipped(Entity<ReflectComponent> reflector, ref GotEquippedHandEvent args)
    {
        if (_gameTiming.ApplyingState)
            return;

        EnsureComp<ReflectUserComponent>(args.User);

        if (reflector.Comp.Enabled)
            EnableAlert(args.User);
    }

    private void OnReflectHandUnequipped(Entity<ReflectComponent> reflector, ref GotUnequippedHandEvent args)
    {
        RefreshReflectUser(args.User);
    }

    private void OnToggleReflect(Entity<ReflectComponent> reflector, ref ItemToggledEvent args)
    {
        reflector.Comp.Enabled = args.Activated;
        Dirty(reflector);

        if (args.User == null)
            return;

        if (reflector.Comp.Enabled)
            EnableAlert(args.User.Value);
        else
            DisableAlert(args.User.Value);
    }

    /// <summary>
    /// Refreshes whether someone has reflection potential, so we can raise directed events on them.
    /// </summary>
    private void RefreshReflectUser(EntityUid user)
    {
        foreach (var ent in _inventorySystem.GetHandOrInventoryEntities(user, SlotFlags.WITHOUT_POCKET))
        {
            if (!HasComp<ReflectComponent>(ent))
                continue;

            EnsureComp<ReflectUserComponent>(user);
            EnableAlert(user);

            return;
        }

        RemCompDeferred<ReflectUserComponent>(user);
        DisableAlert(user);
    }

    private void EnableAlert(EntityUid alertee)
    {
        _alerts.ShowAlert(alertee, DeflectingAlert);
    }

    private void DisableAlert(EntityUid alertee)
    {
        _alerts.ClearAlert(alertee, DeflectingAlert);
    }
}