using UnityEngine;
using Vanguard.Battle;

namespace Vanguard.Board3D
{
    /// <summary>
    /// Стрелка атаки на столе: линия от атакующего к цели и наконечник.
    /// Точки обновляются каждый кадр, поэтому стрелка едет за картами.
    /// </summary>
    public sealed class AttackArrowView
    {
        private const float ShaftWidth = 0.075f;
        private const float HeadWidth = 0.17f;
        private const float HeadLength = 0.38f;

        private GameObject _root;
        private LineRenderer _shaft;
        private LineRenderer _head;
        private Material _material;
        private AnimationConfig _config;
        private Vector3 _from;
        private Vector3 _to;
        private bool _visible;
        private float _alpha;
        private float _widthScale = 1f;

        public bool IsVisible => _visible || _alpha > 0.001f;

        public void Build(Transform parent, AnimationConfig config)
        {
            _config = config;
            _root = new GameObject("Attack Arrow");
            _root.transform.SetParent(parent, false);

            var shader = Shader.Find("Sprites/Default");
            if (shader == null)
                shader = Shader.Find("Unlit/Color");

            _material = shader != null ? new Material(shader) : null;
            _shaft = CreateLine("Shaft", ShaftWidth);
            _head = CreateLine("Head", ShaftWidth * 0.7f);
            _head.positionCount = 3;
            _root.SetActive(false);
        }

        public void SetConfig(AnimationConfig config)
        {
            _config = config;
        }

        public void Show(Vector3 from, Vector3 to)
        {
            SetPoints(from, to);
            _visible = true;

            if (_root != null)
                _root.SetActive(true);
        }

        public void Hide()
        {
            _visible = false;
        }

        public void HideImmediate()
        {
            _visible = false;
            _alpha = 0f;
            if (_root != null)
                _root.SetActive(false);
        }

        public void SetPoints(Vector3 from, Vector3 to)
        {
            _from = from;
            _to = to;
            UpdateGeometry();
        }

        public void Tick(float deltaTime)
        {
            if (_root == null)
                return;

            var target = _visible ? 1f : 0f;
            var duration = _visible
                ? (_config != null ? _config.arrowShowDuration : 0.25f)
                : (_config != null ? _config.arrowHideDuration : 0.2f);
            _alpha = Mathf.MoveTowards(
                _alpha,
                target,
                deltaTime / Mathf.Max(0.01f, duration));

            if (!_visible && _alpha <= 0.001f)
            {
                _root.SetActive(false);
                return;
            }

            _root.SetActive(true);
            _widthScale = 0.55f + (_alpha * 0.45f);
            UpdateGeometry();
            ApplyColor();
        }

        public void Dispose()
        {
            if (_root != null)
            {
                if (Application.isPlaying)
                    Object.Destroy(_root);
                else
                    Object.DestroyImmediate(_root);
                _root = null;
            }

            if (_material != null)
            {
                if (Application.isPlaying)
                    Object.Destroy(_material);
                else
                    Object.DestroyImmediate(_material);
                _material = null;
            }
        }

        private LineRenderer CreateLine(string name, float width)
        {
            var go = new GameObject(name);
            go.transform.SetParent(_root.transform, false);
            var line = go.AddComponent<LineRenderer>();
            line.useWorldSpace = false;
            line.positionCount = 2;
            line.widthMultiplier = width;
            line.numCapVertices = 4;
            line.numCornerVertices = 4;
            line.alignment = LineAlignment.View;
            line.textureMode = LineTextureMode.Stretch;
            line.shadowCastingMode = UnityEngine.Rendering.ShadowCastingMode.Off;
            line.receiveShadows = false;
            if (_material != null)
                line.material = _material;
            return line;
        }

        private void UpdateGeometry()
        {
            if (_shaft == null || _head == null)
                return;

            var direction = _to - _from;
            if (direction.sqrMagnitude < 0.0001f)
                direction = Vector3.forward;
            direction.Normalize();

            _shaft.SetPosition(0, _from);
            _shaft.SetPosition(1, _to);
            _shaft.widthMultiplier = ShaftWidth * _widthScale;

            var tip = _to;
            var back = _to - (direction * HeadLength);
            var side = Vector3.Cross(Vector3.up, direction).normalized;
            if (side.sqrMagnitude < 0.0001f)
                side = Vector3.right;
            var half = side * (HeadWidth * _widthScale);
            _head.SetPosition(0, back + half);
            _head.SetPosition(1, tip);
            _head.SetPosition(2, back - half);
            _head.widthMultiplier = ShaftWidth * 0.7f * _widthScale;
        }

        private void ApplyColor()
        {
            var color = new Color(1f, 0.72f, 0.26f, _alpha * 0.92f);
            foreach (var line in new[] { _shaft, _head })
            {
                if (line == null)
                    continue;

                line.startColor = color;
                line.endColor = color;
            }
        }
    }
}