using UnityEngine;

namespace AibisDream
{
    public enum SubwayCarMotionPhase
    {
        Stopped,
        Cruise,
        Braking
    }

    public sealed class SubwayCarMotion : MonoBehaviour
    {
        [Header("Cruise Jolts")]
        [SerializeField] private float calmIntervalMin = 0.7f;
        [SerializeField] private float calmIntervalMax = 2.2f;
        [SerializeField] private float joltPeakMin = 0.6f;
        [SerializeField] private float joltPeakMax = 1.4f;
        [SerializeField] private float joltDurationMin = 0.18f;
        [SerializeField] private float joltDurationMax = 0.32f;
        [SerializeField] private Vector2Int joltBurstCount = new Vector2Int(1, 3);
        [SerializeField] private float joltBurstGapMin = 0.12f;
        [SerializeField] private float joltBurstGapMax = 0.28f;
        [SerializeField] private float calmNoiseAmplitude = 0.03f;

        [Header("Braking")]
        [SerializeField] private float brakePeakAccel = 1.6f;
        [SerializeField] private AnimationCurve brakeAccelCurve = new AnimationCurve(
            new Keyframe(0f, 0f, 0f, 4f),
            new Keyframe(0.12f, 1f),
            new Keyframe(0.5f, 0.65f, -0.5f, -0.5f),
            new Keyframe(1f, 0f, -1.5f, 0f));

        [Header("Signal Filtering")]
        [SerializeField] private float accelSmoothTime = 0.025f;

        private float targetAccelX;
        private float accelVelocity;
        private float brakeDuration = 1f;
        private float brakeTimer;
        private float nextCruiseEventTime;
        private int burstRemaining;
        private float joltTimer;
        private float joltDuration = 0.2f;
        private float joltPeak = 1f;
        private float joltSign = 1f;
        private float noiseSeed;

        public float AccelX { get; private set; }

        public SubwayCarMotionPhase Phase { get; private set; } = SubwayCarMotionPhase.Cruise;

        private void Awake()
        {
            noiseSeed = Random.value * 1000f;
            ScheduleNextCruiseEvent();
        }

        private void Update()
        {
            switch (Phase)
            {
                case SubwayCarMotionPhase.Cruise:
                    UpdateCruise();
                    break;
                case SubwayCarMotionPhase.Braking:
                    UpdateBraking();
                    break;
                default:
                    targetAccelX = 0f;
                    break;
            }

            AccelX = Mathf.SmoothDamp(AccelX, targetAccelX, ref accelVelocity, accelSmoothTime);
        }

        public void BeginBraking(float duration)
        {
            ClearCruiseJolt();
            Phase = SubwayCarMotionPhase.Braking;
            brakeDuration = Mathf.Max(0.01f, duration);
            brakeTimer = 0f;
        }

        public void SetCruise()
        {
            ClearCruiseJolt();
            Phase = SubwayCarMotionPhase.Cruise;
            ScheduleNextCruiseEvent();
        }

        public void SetStopped()
        {
            ClearCruiseJolt();
            Phase = SubwayCarMotionPhase.Stopped;
            targetAccelX = 0f;
            AccelX = 0f;
            accelVelocity = 0f;
            brakeTimer = 0f;
        }

        private void UpdateCruise()
        {
            if (joltTimer > 0f)
            {
                joltTimer -= Time.deltaTime;
                float normalizedTime = Mathf.Clamp01(1f - joltTimer / joltDuration);
                targetAccelX = EvaluateBiphasicPulse(normalizedTime) * joltPeak * joltSign;

                if (joltTimer <= 0f)
                {
                    if (burstRemaining > 0)
                    {
                        nextCruiseEventTime = Time.time + Random.Range(joltBurstGapMin, joltBurstGapMax);
                    }
                    else
                    {
                        ScheduleNextCruiseEvent();
                    }
                }

                return;
            }

            float noise = (Mathf.PerlinNoise(noiseSeed, Time.time * 0.45f) - 0.5f) * 2f;
            targetAccelX = noise * calmNoiseAmplitude;

            if (Time.time >= nextCruiseEventTime)
            {
                StartJolt();
            }
        }

        private void UpdateBraking()
        {
            brakeTimer += Time.deltaTime;
            float t = Mathf.Clamp01(brakeTimer / brakeDuration);
            targetAccelX = -brakePeakAccel * brakeAccelCurve.Evaluate(t);

            if (brakeTimer >= brakeDuration)
            {
                SetStopped();
            }
        }

        private static float EvaluateBiphasicPulse(float t)
        {
            if (t < 0.5f)
            {
                return Mathf.Sin(t * Mathf.PI * 2f);
            }

            return -Mathf.Sin((t - 0.5f) * Mathf.PI * 2f);
        }

        private void StartJolt()
        {
            if (burstRemaining <= 0)
            {
                int maxExclusive = Mathf.Max(joltBurstCount.x + 1, joltBurstCount.y + 1);
                burstRemaining = Random.Range(joltBurstCount.x, maxExclusive);
            }

            burstRemaining--;
            joltTimer = Random.Range(joltDurationMin, joltDurationMax);
            joltDuration = Mathf.Max(0.01f, joltTimer);
            joltPeak = Random.Range(joltPeakMin, joltPeakMax);
            joltSign = Random.value < 0.5f ? -1f : 1f;
        }

        private void ScheduleNextCruiseEvent()
        {
            burstRemaining = 0;
            nextCruiseEventTime = Time.time + Random.Range(calmIntervalMin, calmIntervalMax);
        }

        private void ClearCruiseJolt()
        {
            burstRemaining = 0;
            joltTimer = 0f;
            targetAccelX = 0f;
        }
    }
}