using System.Collections.Generic;
using Model;
using UnityEngine;

namespace RailroaderPhysicsOverhaul;

[UnityEngine.DefaultExecutionOrder(10000)] // run after all game LateUpdates so our MPB is last to write
public class CarDebugVisualizer : MonoBehaviour
{
    public static CarDebugVisualizer Instance { get; private set; }
    public int TintedCount => _curr.Count;

    // A 1x1 white texture fed via MPB overrides _MainTex so the shader renders
    // texture*color = white*color = solid color, regardless of the car's original texture.
    Texture2D _whiteTex;
    readonly MaterialPropertyBlock _mpb = new();

    readonly Dictionary<Car, Renderer[]> _rendCache = new();
    readonly Dictionary<Car, Color>      _curr       = new();
    readonly Dictionary<Car, Color>      _prev       = new();

    static readonly Color ColFrozen   = new(1.00f, 0.90f, 0.00f); // yellow
    static readonly Color ColFastPath = new(0.00f, 1.00f, 1.00f); // cyan
    static readonly Color ColFullPath = new(1.00f, 0.00f, 1.00f); // magenta

    void Awake()
    {
        Instance = this;
        _whiteTex = new Texture2D(1, 1, TextureFormat.RGBA32, false)
            { hideFlags = HideFlags.HideAndDontSave };
        _whiteTex.SetPixel(0, 0, Color.white);
        _whiteTex.Apply();
    }

    void OnDestroy()
    {
        ClearAll();
        if (_whiteTex) Destroy(_whiteTex);
        Instance = null;
    }

    void LateUpdate()
    {
        _prev.Clear();
        foreach (var kv in _curr) _prev[kv.Key] = kv.Value;
        _curr.Clear();

        if (Main.Settings.DebugHighlightFrozen)
            Collect(ConsistFreezer.FrozenCars, ColFrozen);
        if (Main.Settings.DebugHighlightFastPath)
            Collect(ConsistLOD.FastPathCars, ColFastPath);
        if (Main.Settings.DebugHighlightFullPath)
            Collect(ConsistLOD.FullPathCars, ColFullPath);

        foreach (var (car, color) in _curr)
            ApplyTint(car, color);

        foreach (var car in _prev.Keys)
            if (!_curr.ContainsKey(car))
                ClearTint(car);

        if (Time.frameCount % 300 == 0)
            PurgeCache();
    }

    void Collect(HashSet<Car> source, Color color)
    {
        foreach (var car in source)
            if (car != null && !_curr.ContainsKey(car))
                _curr[car] = color;
    }

    void ApplyTint(Car car, Color color)
    {
        foreach (var r in GetRenderers(car))
        {
            if (r == null) continue;
            _mpb.Clear();
            _mpb.SetColor("_Color",          color);
            _mpb.SetColor("_BaseColor",      color);
            _mpb.SetTexture("_MainTex",      _whiteTex); // built-in RP
            _mpb.SetTexture("_BaseMap",      _whiteTex); // URP
            _mpb.SetTexture("_BaseColorMap", _whiteTex); // HDRP
            r.SetPropertyBlock(_mpb);
        }
    }

    void ClearTint(Car car)
    {
        foreach (var r in GetRenderers(car))
            if (r != null) r.SetPropertyBlock(null);
    }

    void ClearAll()
    {
        foreach (var car in _curr.Keys) ClearTint(car);
        foreach (var car in _prev.Keys) ClearTint(car);
        _curr.Clear();
        _prev.Clear();
        _rendCache.Clear();
    }

    Renderer[] GetRenderers(Car car)
    {
        if (!_rendCache.TryGetValue(car, out var renderers) || renderers.Length == 0)
        {
            renderers = car.BodyTransform != null
                ? car.BodyTransform.GetComponentsInChildren<Renderer>()
                : System.Array.Empty<Renderer>();
            // Don't cache empty results — retry next frame until the mesh loads
            if (renderers.Length > 0)
                _rendCache[car] = renderers;
        }
        return renderers;
    }

    void PurgeCache()
    {
        var dead = new List<Car>();
        foreach (var car in _rendCache.Keys)
            if (car == null) dead.Add(car);
        foreach (var car in dead) _rendCache.Remove(car);
    }
}