using System;
using System.Collections;
using System.Collections.Generic;
using UniRx;
using CultMath;
using CultMath.UnityBridge;
using UnityEngine;
using static CultMath.math;

public class GuidedProjectileManager : InstantWeaponEffectManager
{
    // Presentation follows the committed shot (FireControl): the round retargets to the burst point the commit
    // names and bursts when the shot resolves, rather than predicting either from its own homing.
    private static void Bind(GuidedProjectile p, Zone zone, int shotId)
    {
        Vector3 At(ShotOutcome o) => new Vector3(o.BurstPoint.x, p.transform.position.y, o.BurstPoint.y);
        var bindings = new CompositeDisposable();
        zone.ShotCommitted.Where(o => o.ShotId == shotId && o.HasBurstPoint).Subscribe(o => p.BurstAt(At(o))).AddTo(bindings);
        zone.ShotResolved.Where(o => o.ShotId == shotId)
            .Subscribe(o => p.Resolve(o.Result == ShotResult.Hit || o.Result == ShotResult.Burst, o.HasBurstPoint ? At(o) : (Vector3?) null,
                ActionGameManager.DrawsAt(o.Target)))
            .AddTo(bindings);
        // The binding outlives a fade-out until the shot's own arrival (the moment the simulation resolves it), plus a
        // second of margin; a shot no longer pending has nothing left to resolve.
        p.BindingLifetime = zone.TryGetShot(shotId, out var shot) ? max(0f, shot.ArrivalTime - zone.Time) + 1f : 0f;
        p.Binding = bindings; // replaces, and so disposes, any binding the projectile already had
    }

    public Prototype ProjectilePrototype;

    public Subject<(Entity source, Transform target, GuidedProjectile missile)> OnFireGuided = new Subject<(Entity source, Transform target, GuidedProjectile missile)>();

    public override void Fire(InstantWeapon weapon, EquippedItem item, EntityInstance source, EntityInstance target, int shotId)
    {
        if(weapon.Data is LauncherData launcher)
        {
            // A round the simulation fired at no target (FireControl.Fire: a fused round with no valid targeting
            // data, or out of arc) flies to the point it bursts at; one with no target and no burst is not a shot.
            PendingShot shot = default;
            if (target == null && !(source.Entity.Zone.TryGetShot(shotId, out shot) && shot.Fuse != null)) return;
            var burst = shot.BurstPosition.ToUnity();
            var p = ProjectilePrototype.Instantiate<GuidedProjectile>();
            p.ShotId = shotId;
            p.Source = source.transform;
            p.SourceEntity = source.Entity;
            if (target != null) p.Target = target.transform;
            else p.TargetPosition = () => burst;
            p.Frequency = item.Evaluate(MunitionParts.Of<MunitionControlData>(item).EvasionFrequency);
            var hp = item.Hardpoint;
            var barrel = source.GetBarrel(hp);
            p.StartPosition = (p.transform.position = barrel.position).ToCultMath();
            p.Range = weapon.Range;
            p.GuidanceCurve = launcher.GuidanceCurve.ToCurve();
            p.LiftCurve = launcher.LiftCurve.ToCurve();
            p.ThrustCurve = launcher.ThrustCurve.ToCurve();
            p.Velocity = barrel.forward * weapon.Velocity;
            p.Thrust = item.Evaluate(MunitionParts.Of<MunitionThrusterData>(item).Acceleration);
            p.TopSpeed = item.Evaluate(MunitionParts.Of<MunitionThrusterData>(item).MaxSpeed);
            Bind(p, source.Entity.Zone, shotId);
            // A round with no target (a fused round fired at none) has no transform to hand a listener.
            OnFireGuided.OnNext((source.Entity, target != null ? target.transform : null, p));
        }
        else if(weapon.Data is GuidedWeaponData guidance)
        {
            var p = ProjectilePrototype.Instantiate<GuidedProjectile>();
            p.ShotId = shotId;
            p.Source = source.transform;
            p.SourceEntity = source.Entity;
            p.Frequency = item.Evaluate(MunitionParts.Of<MunitionControlData>(item).EvasionFrequency);
            var hp = item.Hardpoint;
            var barrel = source.GetBarrel(hp);
            p.StartPosition = (p.transform.position = barrel.position).ToCultMath();
            p.Range = weapon.Range;
            p.GuidanceCurve = guidance.GuidanceCurve.ToCurve();
            p.LiftCurve = guidance.LiftCurve.ToCurve();
            p.ThrustCurve = guidance.ThrustCurve.ToCurve();
            p.Velocity = barrel.forward * weapon.Velocity;
            p.Thrust = item.Evaluate(MunitionParts.Of<MunitionThrusterData>(item).Acceleration);
            p.TopSpeed = item.Evaluate(MunitionParts.Of<MunitionThrusterData>(item).MaxSpeed);
            p.TargetPosition = () => (source.Entity.Position + length(source.LookAtPoint.position.ToCultMath() - source.Entity.Position) * source.Entity.Aim).ToUnity();
            Bind(p, source.Entity.Zone, shotId);
        }
        else Debug.LogError($"Weapon {item.Data.Name} linked to {name} effect, but is not a Launcher!");
    }
}