AppleHillsProduction/Assets/Scripts/Common/Visual/TrajectoryPreview.cs

using Core;
using UnityEngine;

namespace Common.Visual
{
    /// <summary>
    /// Common trajectory preview component for slingshot-style mechanics.
    /// Displays a line showing the predicted arc of a launched projectile.
    /// Supports multiple API overloads for different use cases.
    /// </summary>
    [RequireComponent(typeof(LineRenderer))]
    public class TrajectoryPreview : MonoBehaviour
    {
        [Header("Trajectory Settings")]
        [Tooltip("Number of points in trajectory line")]
        [SerializeField] private int trajectoryPoints = 50;
        
        [Tooltip("Time step between trajectory points (seconds)")]
        [SerializeField] private float timeStep = 0.1f;
        
        [Tooltip("Ground level Y position (trajectory stops here)")]
        [SerializeField] private float groundLevel = -10f;
        
        [Header("Visual")]
        [Tooltip("Color of trajectory line")]
        [SerializeField] private Color lineColor = Color.yellow;
        
        [Tooltip("Width of trajectory line")]
        [SerializeField] private float lineWidth = 0.1f;
        
        private LineRenderer _lineRenderer;
        private bool _isLocked;
        private float _lockTimer;
        private float _lockDuration;
        
        #region Unity Lifecycle
        
        private void Awake()
        {
            _lineRenderer = GetComponent<LineRenderer>();
            
            if (_lineRenderer != null)
            {
                _lineRenderer.startWidth = lineWidth;
                _lineRenderer.endWidth = lineWidth;
                _lineRenderer.startColor = lineColor;
                _lineRenderer.endColor = lineColor;
                _lineRenderer.positionCount = trajectoryPoints;
                _lineRenderer.enabled = false;
            }
        }
        
        private void Update()
        {
            if (_isLocked)
            {
                _lockTimer += Time.deltaTime;
                if (_lockTimer >= _lockDuration)
                {
                    _isLocked = false;
                    Hide();
                }
            }
        }
        
        #endregion
        
        #region Public API - Visibility
        
        /// <summary>
        /// Show the trajectory preview line.
        /// Clears any existing trajectory data so nothing displays until UpdateTrajectory is called.
        /// </summary>
        public void Show()
        {
            if (_lineRenderer != null)
            {
                // Clear old trajectory data
                _lineRenderer.positionCount = 0;
                
                // Enable the line renderer
                _lineRenderer.enabled = true;
            }
        }
        
        /// <summary>
        /// Hide the trajectory preview line (unless locked)
        /// </summary>
        public void Hide()
        {
            if (_isLocked) return;
            
            if (_lineRenderer != null)
            {
                _lineRenderer.enabled = false;
            }
        }
        
        /// <summary>
        /// Lock the trajectory display for a duration (keeps showing after launch)
        /// </summary>
        public void LockTrajectory(float duration)
        {
            _isLocked = true;
            _lockTimer = 0f;
            _lockDuration = duration;
            
            if (_lineRenderer != null)
            {
                _lineRenderer.enabled = true;
            }
        }
        
        /// <summary>
        /// Force hide the trajectory immediately, clearing any lock state.
        /// Use this when transitioning turns or resetting the slingshot.
        /// </summary>
        public void ForceHide()
        {
            _isLocked = false;
            _lockTimer = 0f;
            
            if (_lineRenderer != null)
            {
                _lineRenderer.enabled = false;
            }
        }
        
        #endregion
        
        #region Public API - Update Trajectory (Multiple Overloads)
        
        /// <summary>
        /// Update trajectory from velocity and gravity directly.
        /// Most explicit - caller calculates everything.
        /// </summary>
        public void UpdateTrajectory(Vector2 startPos, Vector2 velocity, float gravity)
        {
            if (_lineRenderer == null) return;
            
            CalculateAndSetTrajectory(startPos, velocity, gravity);
        }
        
        /// <summary>
        /// Update trajectory from launch force and mass.
        /// Calculates velocity as: v = (direction * force) / mass
        /// </summary>
        public void UpdateTrajectory(Vector2 startPos, Vector2 direction, float force, float mass, float gravity)
        {
            if (_lineRenderer == null) return;
            
            if (mass <= 0f)
            {
                Logging.Warning("[TrajectoryPreview] Cannot calculate trajectory with zero or negative mass!");
                return;
            }
            
            Vector2 velocity = (direction * force) / mass;
            CalculateAndSetTrajectory(startPos, velocity, gravity);
        }
        
        /// <summary>
        /// Update trajectory from prefab's Rigidbody2D properties.
        /// Reads mass and gravityScale from prefab, calculates gravity automatically.
        /// </summary>
        public void UpdateTrajectory(Vector2 startPos, Vector2 direction, float force, GameObject prefab)
        {
            if (_lineRenderer == null || prefab == null) return;
            
            var rb = prefab.GetComponent<Rigidbody2D>();
            if (rb == null)
            {
                Logging.Warning($"[TrajectoryPreview] Prefab '{prefab.name}' has no Rigidbody2D!");
                return;
            }
            
            float mass = rb.mass;
            float gravity = Physics2D.gravity.magnitude * rb.gravityScale;
            
            if (mass <= 0f)
            {
                Logging.Warning($"[TrajectoryPreview] Prefab '{prefab.name}' has zero mass!");
                return;
            }
            
            Vector2 velocity = (direction * force) / mass;
            CalculateAndSetTrajectory(startPos, velocity, gravity);
        }
        
        #endregion
        
        #region Internal Calculation
        
        /// <summary>
        /// Calculate and set trajectory points using kinematic formula.
        /// Uses: y = y0 + v*t - 0.5*g*t^2
        /// </summary>
        private void CalculateAndSetTrajectory(Vector2 startPos, Vector2 velocity, float gravity)
        {
            Vector3[] points = new Vector3[trajectoryPoints];
            
            for (int i = 0; i < trajectoryPoints; i++)
            {
                float time = i * timeStep;
                
                // Kinematic equations
                float x = startPos.x + velocity.x * time;
                float y = startPos.y + velocity.y * time - 0.5f * gravity * time * time;
                
                points[i] = new Vector3(x, y, 0);
                
                // Stop at ground level
                if (y <= groundLevel)
                {
                    // Fill remaining points at ground level
                    for (int j = i; j < trajectoryPoints; j++)
                    {
                        float tGround = j * timeStep;
                        float xGround = startPos.x + velocity.x * tGround;
                        points[j] = new Vector3(xGround, groundLevel, 0);
                    }
                    break;
                }
            }
            
            _lineRenderer.positionCount = trajectoryPoints;
            _lineRenderer.SetPositions(points);
        }
        
        #endregion
        
        #region Configuration
        
        /// <summary>
        /// Set the number of trajectory points (for performance tuning)
        /// </summary>
        public void SetTrajectoryPoints(int points)
        {
            trajectoryPoints = Mathf.Max(5, points);
            if (_lineRenderer != null)
            {
                _lineRenderer.positionCount = trajectoryPoints;
            }
        }
        
        /// <summary>
        /// Set the time step between points
        /// </summary>
        public void SetTimeStep(float step)
        {
            timeStep = Mathf.Max(0.01f, step);
        }
        
        #endregion
    }
}