using UnityEngine;

[RequireComponent(typeof(Camera))]
public class MotionBlur : MonoBehaviour
{
    [Header("Blur Settings")]
    [Range(1, 5)] public int FastFilter = 4;
    public float blurSmoothing = 2f;

    [Header("Blur Strength Ranges")]
    public float minBlurNormal = 0.05f;
    public float maxBlurNormal = 0.15f;

    public float minBlurNOS = 0.1f;
    public float maxBlurNOS = 0.3f;

    [Header("References")]
    public Material motionBlurMaterial;
    public Texture2D mask;
    public VehicleController vehicle;

    private Camera cam;

    private Matrix4x4 previousViewProjection;
    private Matrix4x4 viewProj;
    private Matrix4x4 currentToPreviousViewProjectionMatrix;

    private float smoothedSpeed = 0f;

    private static readonly int currentPrevString = Shader.PropertyToID("_CurrentToPreviousViewProjectionMatrix");
    private static readonly int distanceString = Shader.PropertyToID("_Distance");
    private static readonly int blurStrengthString = Shader.PropertyToID("_BlurStrength");
    private static readonly int blurTexString = Shader.PropertyToID("_BlurTex");

    void Start()
    {
        cam = GetComponent<Camera>();
        previousViewProjection = cam.projectionMatrix * cam.worldToCameraMatrix;
        Shader.SetGlobalTexture("_MaskTex", mask != null ? mask : Texture2D.whiteTexture);
    }

    void Update()
    {
        if (vehicle != null)
        {
            float targetSpeed = Mathf.Clamp01(vehicle.CurrentSpeed / vehicle.MaximumSpeed);
            smoothedSpeed = Mathf.Lerp(smoothedSpeed, targetSpeed, Time.deltaTime * blurSmoothing);
        }
        else
        {
            smoothedSpeed = Mathf.Lerp(smoothedSpeed, 0f, Time.deltaTime * blurSmoothing);
        }
    }

    private void OnRenderImage(RenderTexture src, RenderTexture dest)
    {
        viewProj = cam.projectionMatrix * cam.worldToCameraMatrix;
        currentToPreviousViewProjectionMatrix = previousViewProjection * viewProj.inverse;

        motionBlurMaterial.SetMatrix(currentPrevString, currentToPreviousViewProjectionMatrix);
        motionBlurMaterial.SetFloat(distanceString, 1f); // Required

        // Choose blur range based on NOS state
        float min = vehicle != null && vehicle.nosActive ? minBlurNOS : minBlurNormal;
        float max = vehicle != null && vehicle.nosActive ? maxBlurNOS : maxBlurNormal;

        float blurStrength = Mathf.Lerp(min, max, smoothedSpeed);
        motionBlurMaterial.SetFloat(blurStrengthString, blurStrength);

        previousViewProjection = viewProj;

        RenderTexture rt = RenderTexture.GetTemporary(
            Screen.width / FastFilter,
            Screen.height / FastFilter,
            0,
            src.format
        );

        Graphics.Blit(src, rt, motionBlurMaterial, 0);
        motionBlurMaterial.SetTexture(blurTexString, rt);
        RenderTexture.ReleaseTemporary(rt);

        Graphics.Blit(src, dest, motionBlurMaterial, 1);
    }
}