using System;
using System.Collections.Generic;
using System.IO;
using UnityEngine;

namespace MSCO
{
    /// <summary>
    /// Verkehr (NPC-Autos): Der Spieler mit der kleinsten ID (Welt-Autorität, gibt auch Uhrzeit/Wetter vor)
    /// simuliert den Verkehr und schickt die Positionen. Bei allen anderen fahren die Autos dann nur noch nach
    /// (kinematisch) - so stehen sie überall an derselben Stelle und man kann sich gemeinsam darüber ärgern.
    /// </summary>
    public class TrafficSync
    {
        static readonly string[] Roots = { "TRAFFIC", "NPC_CARS" };

        const float ScanInterval = 10f;
        const float SendInterval = 0.1f;
        const float Stale = 1.5f;          // so lange ohne Daten: wieder selbst simulieren
        const float Smoothing = 12f;
        const float MaxExtrapolation = 0.3f;

        class Car
        {
            public int Key;
            public Rigidbody Rb;
            public bool WasKinematic;
            public bool Following;
            public Vector3 TargetPos, TargetVel;
            public Quaternion TargetRot;
            public float TargetTime = -100f;
        }

        readonly Dictionary<int, Car> cars = new Dictionary<int, Car>();
        readonly HashSet<Rigidbody> seen = new HashSet<Rigidbody>();
        float nextScan, sendTimer;

        public int Count { get { return cars.Count; } }

        public void Reset()
        {
            foreach (Car c in cars.Values) StopFollowing(c);
            cars.Clear();
            seen.Clear();
            nextScan = 0f;
        }

        public void Update(bool authority, float dt, Action<MsgType, byte[]> send)
        {
            if (Time.time >= nextScan)
            {
                nextScan = Time.time + ScanInterval;
                Scan();
            }

            if (!authority)
            {
                foreach (Car c in cars.Values)
                    if (c.Following && Time.time - c.TargetTime > Stale) StopFollowing(c);
                return;
            }

            // Wir simulieren: eventuell noch nachfahrende Autos freigeben, Positionen senden
            foreach (Car c in cars.Values) if (c.Following) StopFollowing(c);
            sendTimer += dt;
            if (sendTimer < SendInterval) return;
            sendTimer = 0f;

            var list = new List<Car>();
            foreach (Car c in cars.Values)
                if (c.Rb != null && c.Rb.gameObject.activeInHierarchy) list.Add(c);
            if (list.Count == 0) return;
            send(MsgType.TrafficStates, NetSession.Build(w =>
            {
                w.Write(list.Count);
                foreach (Car c in list)
                {
                    Vector3 p = c.Rb.position, v = c.Rb.velocity;
                    Quaternion q = c.Rb.rotation;
                    w.Write(c.Key);
                    w.Write(p.x); w.Write(p.y); w.Write(p.z);
                    w.Write(q.x); w.Write(q.y); w.Write(q.z); w.Write(q.w);
                    w.Write(v.x); w.Write(v.y); w.Write(v.z);
                }
            }));
        }

        public void Handle(BinaryReader r, bool authority)
        {
            int count = r.ReadInt32();
            for (int i = 0; i < count; i++)
            {
                int key = r.ReadInt32();
                var p = new Vector3(r.ReadSingle(), r.ReadSingle(), r.ReadSingle());
                var q = new Quaternion(r.ReadSingle(), r.ReadSingle(), r.ReadSingle(), r.ReadSingle());
                var v = new Vector3(r.ReadSingle(), r.ReadSingle(), r.ReadSingle());
                Car c;
                if (authority || !cars.TryGetValue(key, out c) || c.Rb == null) continue;
                if (float.IsNaN(p.x) || float.IsNaN(q.w) || p.sqrMagnitude > 1e8f || v.sqrMagnitude > 1e4f) continue;
                c.TargetPos = p;
                c.TargetRot = q;
                c.TargetVel = v;
                c.TargetTime = Time.time;
                if (!c.Following)
                {
                    c.WasKinematic = c.Rb.isKinematic;
                    c.Rb.isKinematic = true;
                    c.Rb.position = p;
                    c.Rb.rotation = q;
                    c.Following = true;
                }
            }
        }

        public void FixedUpdate()
        {
            foreach (Car c in cars.Values)
            {
                if (!c.Following || c.Rb == null) continue;
                float ahead = Mathf.Min(Time.time - c.TargetTime, MaxExtrapolation);
                Vector3 goal = c.TargetPos + c.TargetVel * ahead;
                float t = Mathf.Clamp01(Time.fixedDeltaTime * Smoothing);
                if ((c.Rb.position - goal).sqrMagnitude > 25f) { c.Rb.position = goal; c.Rb.rotation = c.TargetRot; continue; }
                c.Rb.MovePosition(Vector3.Lerp(c.Rb.position, goal, t));
                c.Rb.MoveRotation(Quaternion.Slerp(c.Rb.rotation, c.TargetRot, t));
            }
        }

        static void StopFollowing(Car c)
        {
            if (!c.Following) return;
            c.Following = false;
            if (c.Rb != null) c.Rb.isKinematic = c.WasKinematic;
        }

        void Scan()
        {
            int before = cars.Count;
            foreach (Rigidbody rb in UnityEngine.Object.FindObjectsOfType<Rigidbody>())
            {
                if (rb == null || !seen.Add(rb)) continue;
                if (Array.IndexOf(Roots, rb.transform.root.name) < 0) continue;
                // nur das oberste Rigidbody je Auto (keine Räder/Türen)
                Transform parent = rb.transform.parent;
                if (parent != null && parent.GetComponentInParent<Rigidbody>() != null) continue;
                int key = Hash(FsmSync.PathOf(rb.transform));
                if (cars.ContainsKey(key)) continue;
                cars[key] = new Car { Key = key, Rb = rb };
            }
            if (cars.Count != before) MscoLog.Info("[MSCO] Traffic: " + cars.Count + " cars synced");
        }

        static int Hash(string s)
        {
            unchecked
            {
                uint h = 2166136261;
                foreach (char c in s) { h ^= c; h *= 16777619; }
                return (int)h;
            }
        }
    }
}