using UnityEngine;

namespace NanoBrain.Unity.Braitenberg {

    /// <summary>
    /// A light sensor
    /// </summary>
    [HelpURL("https://passer.life/documentation/nanobrain/Documentation/html/class_nano_brain_1_1_unity_1_1_braitenberg_1_1_light_sensor.html")]
    public class LightSensor : Sensor {
        /// <summary>
        /// If true, perform occlusion checks with raycasts
        /// </summary>
        [Tooltip("If true, perform occlusion checks with raycasts.")]
        public bool useOcclusion = true;
        /// <summary>
        /// Angle in degrees for directional sensitivity; >= 180: omnidirectional.
        /// </summary>
        [Tooltip("Angle (degrees) for directional sensitivity; >=180: omnidirectional.")]
        public float sensitivityAngle = 180f;

        protected override float SampleSensor() {
            float sum = 0f;
            // Get all active lights in scene (Point lights only)
#if UNITY_6000_0_OR_NEWER
            Light[] lights = FindObjectsByType<Light>();
#else            
            Light[] lights = FindObjectsByType<Light>(FindObjectsSortMode.None);
#endif            
            Vector3 pos = transform.position;
            Vector3 forward = transform.forward;

            float halfAngleCos = Mathf.Cos(sensitivityAngle * 0.5f * Mathf.Deg2Rad);

            int lightCount = 0;
            foreach (Light light in lights) {
                if (!light.enabled || light.type != LightType.Point)
                    continue;

                // quick distance check
                float dist = Vector3.Distance(light.transform.position, pos);
                if (dist > this.sensorRange + light.range)
                    continue; // outside both sensor and light ranges

                // angular sensitivity
                Vector3 toLight = (light.transform.position - pos).normalized;
                if (sensitivityAngle < 180f) {
                    if (Vector3.Dot(forward, toLight) < halfAngleCos)
                        continue;
                }

                // compute light falloff: Unity point lights use inverse squared (physically plausible)
                // you can approximate using L.intensity and L.range
                float attenuation = 0f;
                if (dist < light.range) {
                    // inverse-square like falloff (avoid divide-by-zero)
                    attenuation = light.intensity / Mathf.Max(0.01f, dist * dist);
                    // optionally scale by (1 - dist/range) for a linear blend:
                    attenuation *= 1f - dist / light.range;
                }
                else
                    continue;

                // occlusion check
                if (useOcclusion) {
                    Vector3 dir = (light.transform.position - pos).normalized;
                    float rayDist = Mathf.Min(dist, light.range);
                    if (Physics.Raycast(pos, dir, out RaycastHit hit, rayDist, senseLayer))
                        attenuation *= 0f; // completely blocked; or reduce by factor
                }

                //Debug.DrawRay(this.transform.position, toLight * sensorRange);
                // color consideration: convert light color to luminance if needed
                float luminance = RGBToLuminance(light.color) * attenuation;
                //Debug.Log(luminance);

                sum += luminance;
                lightCount++;
            }

            if (lightCount == 0)
                return 0;
            else
                return sum / lightCount;
        }

        static float RGBToLuminance(Color c) {
            // simple Rec.709 luminance
            return 0.2126f * c.r + 0.7152f * c.g + 0.0722f * c.b;
        }
    }

}