// Portfolio reconstruction, 2026. Not original production source.
// Based on the Notion parachute-attraction CSV ghost replay description.
using System;
using System.Globalization;
using System.Collections.Generic;
using UnityEngine;

public sealed class GhostReplay : MonoBehaviour
{
    [Serializable] public struct Sample
    {
        public float time;
        public Vector3 position;
        public Quaternion rotation;
    }
    [SerializeField] TextAsset csv; // time,x,y,z,qx,qy,qz,qw; header required
    [SerializeField] Transform player;
    [SerializeField, Min(1)] float catchUpDistance = 40;
    [SerializeField, Min(0)] float speed = 1;
    readonly List<Sample> samples = new List<Sample>();
    float clock;
    int cursor;

    void Start()
    {
        try { Load(csv == null ? null : csv.text); }
        catch (Exception error) { Debug.LogError(error.Message, this); enabled = false; }
    }

    public void Load(string text)
    {
        if (string.IsNullOrWhiteSpace(text)) throw new ArgumentException("CSV is empty.");
        var parsed = new List<Sample>();
        var rows = text.Split('\n');
        for (int i = 1; i < rows.Length; i++)
        {
            if (string.IsNullOrWhiteSpace(rows[i])) continue;
            var cells = rows[i].Trim().Split(',');
            if (cells.Length != 8) throw new FormatException("Expected 8 columns at row " + (i + 1));
            float[] v = new float[8];
            for (int j = 0; j < v.Length; j++)
                if (!float.TryParse(cells[j], NumberStyles.Float, CultureInfo.InvariantCulture, out v[j])
                    || float.IsNaN(v[j]) || float.IsInfinity(v[j]))
                    throw new FormatException("Invalid finite number at row " + (i + 1));
            if (v[0] < 0 || (parsed.Count > 0 && v[0] <= parsed[parsed.Count - 1].time))
                throw new FormatException("Timestamps must increase strictly.");
            var q = new Quaternion(v[4], v[5], v[6], v[7]);
            if (Quaternion.Dot(q, q) < 0.000001f) throw new FormatException("Zero quaternion.");
            parsed.Add(new Sample { time = v[0], position = new Vector3(v[1], v[2], v[3]), rotation = q.normalized });
        }
        if (parsed.Count < 2) throw new FormatException("At least two samples are required.");
        samples.Clear(); samples.AddRange(parsed); cursor = 0; clock = samples[0].time;
        Apply();
    }

    void Update()
    {
        if (samples.Count < 2) return;
        clock = Mathf.Min(clock + Time.deltaTime * Mathf.Max(0, speed), samples[samples.Count - 1].time);
        Apply();
        if (player != null && (transform.position - player.position).sqrMagnitude > catchUpDistance * catchUpDistance)
            SeekNearest(player.position);
    }

    public void SeekNearest(Vector3 position)
    {
        if (samples.Count == 0) return;
        int nearest = 0; float best = float.PositiveInfinity;
        for (int i = 0; i < samples.Count; i++)
        {
            float distance = (samples[i].position - position).sqrMagnitude;
            if (distance < best) { best = distance; nearest = i; }
        }
        clock = samples[nearest].time; cursor = Mathf.Min(nearest, samples.Count - 2); Apply();
    }

    void Apply()
    {
        while (cursor < samples.Count - 2 && samples[cursor + 1].time < clock) cursor++;
        Sample a = samples[cursor], b = samples[cursor + 1];
        float t = Mathf.InverseLerp(a.time, b.time, clock);
        transform.SetPositionAndRotation(Vector3.Lerp(a.position, b.position, t), Quaternion.Slerp(a.rotation, b.rotation, t));
    }
}