using UnityEngine;

namespace Unheimlich.World.HouseOfLeaves
{
    /// <summary>
    /// Animates the sand terrain rising from below the corridor floor
    /// based on the player's progression through the corridor.
    ///
    /// The terrain starts buried underground and slowly emerges as the
    /// player advances, simulating sand flooding the corridor from below.
    /// </summary>
    public class SandTerrainController : MonoBehaviour
    {
        // ─────────────────────────────────────────────────────────────────────────
        // Serialized Fields
        // ─────────────────────────────────────────────────────────────────────────

        [Header("References")]
        [Tooltip("The HouseOfLeavesController driving the progression value.")]
        [SerializeField] private HouseOfLeavesController _controller;

        [Tooltip("The sand terrain Transform to animate.")]
        [SerializeField] private Transform _sandTerrain;

        [Header("Rise Settings")]
        [Tooltip("Y position of the terrain at the start (buried underground).")]
        [SerializeField] private float _startY = -4f;

        [Tooltip("Y position of the terrain at full progression (emerged).")]
        [SerializeField] private float _endY = 0.5f;

        [Tooltip("Lerp speed applied to the vertical movement each frame.")]
        [SerializeField] private float _lerpSpeed = 2f;

        [Tooltip("Animation curve mapping progression [0,1] to rise amount [0,1]. " +
                 "Use this to delay the rise until mid-corridor for example.")]
        [SerializeField] private AnimationCurve _riseCurve = AnimationCurve.EaseInOut(0f, 0f, 1f, 1f);

        // ─────────────────────────────────────────────────────────────────────────
        // Unity Messages
        // ─────────────────────────────────────────────────────────────────────────

        private void Start()
        {
            if (_controller == null)
            {
                Debug.LogError("[SandTerrainController] HouseOfLeavesController reference is missing.");
                return;
            }

            if (_sandTerrain == null)
            {
                Debug.LogError("[SandTerrainController] Sand terrain Transform is missing.");
                return;
            }

            // Initialize position immediately without lerp.
            Vector3 startPos = _sandTerrain.position;
            startPos.y       = _startY;
            _sandTerrain.position = startPos;
        }

        private void Update()
        {
            if (_controller == null || _sandTerrain == null) return;

            float t       = _riseCurve.Evaluate(_controller.Progression);
            float targetY = Mathf.Lerp(_startY, _endY, t);

            Vector3 pos = _sandTerrain.position;
            pos.y       = Mathf.Lerp(pos.y, targetY, Time.deltaTime * _lerpSpeed);
            _sandTerrain.position = pos;
        }
    }
}