using UnityEngine;

#if UNITY_EDITOR
using UnityEditor;
#endif

namespace Amanotes.Core
{
    /// <summary>
    /// An <see cref="ISizeListener"/> that scales a <see cref="SpriteRenderer"/> to
    /// fit inside or fill a <see cref="Widget2D"/> area.
    ///
    /// <list type="bullet">
    ///   <item><description><b>fitFill = 0</b> – uniform <em>fit</em>: entire sprite is visible (letterbox).</description></item>
    ///   <item><description><b>fitFill = 1</b> – uniform <em>fill</em>: sprite covers the full area (crops edges).</description></item>
    ///   <item><description>Values in between lerp the local scale between the two extremes.</description></item>
    /// </list>
    ///
    /// Usage: add this component to a GameObject, assign it as a listener on a
    /// <see cref="Widget2D"/> (or let the Widget2D editor scan it automatically),
    /// and set <see cref="_fitFill"/> in the inspector.
    /// </summary>
    [AddComponentMenu("Widget2D/Sprite Fit Listener")]
    public class SpriteFitListener : MonoBehaviour, ISizeListener
    {
        [SerializeField] private SpriteRenderer _spriteRenderer;

        [SerializeField]
        [Range(0f, 1f)]
        [Tooltip("0 = fit (letterbox), 1 = fill (crop). Lerps the uniform scale between the two extremes.")]
        private float _fitFill = 0f;

        /// <summary>
        /// Fit/fill ratio. 0 = fit, 1 = fill, values in between blend the two.
        /// Setting this at runtime immediately re-applies the last received size.
        /// </summary>
        public float fitFill
        {
            get => _fitFill;
            set
            {
                _fitFill = Mathf.Clamp01(value);
                if (_lastSize.sqrMagnitude > 0f) ApplyScale(_lastSize);
            }
        }

        // Serialized so it survives domain reloads and prefab instantiation.
        // Set by OnResize; used to re-apply when the sprite or fitFill changes.
        [SerializeField] private Vector2 _lastSize;

        // ─── ISizeListener ────────────────────────────────────────────────────

        /// <inheritdoc/>
        public void OnResize(Vector2 size)
        {
            _lastSize = size;
            ApplyScale(size);
        }

        // ─── Internal ─────────────────────────────────────────────────────────

        private void ApplyScale(Vector2 widgetSize)
        {
            if (_spriteRenderer == null || _spriteRenderer.sprite == null) return;
            if (widgetSize.x <= 0f || widgetSize.y <= 0f) return;

            var sprite = _spriteRenderer.sprite;
            var rect = sprite.rect;
            var ppu = sprite.pixelsPerUnit;
            var orgSize = new Vector2(rect.width / ppu, rect.height / ppu);
            var sx = widgetSize.x / orgSize.x;
            var sy = widgetSize.y / orgSize.y;
            var minS = Mathf.Min(sx, sy);
            var maxS = Mathf.Max(sx, sy);
            var s = Mathf.Lerp(minS, maxS, _fitFill);
            _spriteRenderer.transform.localScale = Vector3.one * s;
        }

        /// <summary>
        /// Re-applies the fit/fill scale using the last size received from the Widget2D.
        /// Call this after changing the sprite externally so the scale is recalculated
        /// for the new sprite's aspect ratio.
        /// </summary>
        public void Refresh()
        {
            if (_lastSize.sqrMagnitude > 0f) ApplyScale(_lastSize);
        }

        /// <summary>
        /// Swaps the target sprite and immediately refreshes the scale.
        /// Convenience wrapper around assigning <c>spriteRenderer.sprite</c> + <see cref="Refresh"/>.
        /// </summary>
        public void SetSprite(Sprite sprite)
        {
            if (_spriteRenderer == null) return;
            _spriteRenderer.sprite = sprite;
            Refresh();
        }

        // ─── Unity lifecycle ──────────────────────────────────────────────────

        private void Awake()
        {
            if (_spriteRenderer == null)
                _spriteRenderer = GetComponent<SpriteRenderer>();
        }

#if UNITY_EDITOR
        // Tracks the sprite seen last OnValidate so we can detect inspector changes.
        [System.NonSerialized] private Sprite _lastKnownSprite;

        private void OnValidate()
        {
            if (_spriteRenderer == null)
                _spriteRenderer = GetComponent<SpriteRenderer>();

            if (PrefabUtility.IsPartOfPrefabAsset(gameObject)) return;

            EditorApplication.delayCall += () =>
            {
                if (this == null) return;

                // Re-apply whenever fitFill is tweaked OR the sprite was swapped
                // in the inspector (detected by reference change).
                var currentSprite = _spriteRenderer != null ? _spriteRenderer.sprite : null;
                bool spriteChanged = currentSprite != _lastKnownSprite;
                _lastKnownSprite = currentSprite;

                if (_lastSize.sqrMagnitude > 0f)
                    Refresh();
            };
        }

        private void Reset()
        {
            _spriteRenderer = GetComponent<SpriteRenderer>();
        }
#endif
    }
}