using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;

namespace MazeGen
{
    /// <summary>
    /// Plays a fight out on a grid in its own additively-loaded scene, then throws that scene
    /// away and hands the camera back to the maze.
    ///
    /// Why this can't corrupt the maze: the fight's outcome is already fully decided before
    /// playback starts (see <see cref="CombatResolver"/>), so this class is pure animation over a
    /// finished <see cref="BattleResult"/> - it never touches a character sheet, a room, or an
    /// agent. Health bars run off a private display copy of each combatant's health. And because
    /// everything it creates lives in a separate scene which is unloaded on exit, there's nothing
    /// left behind to restore. The maze's own GameObjects are never disabled or re-created (which
    /// would kill the spawn coroutines), only hidden by suspending the maze camera; when the fight
    /// ends every agent is exactly where it was, and only the fight's result has changed.
    ///
    /// Runs on real Unity time, because the maze simulation is frozen via SimulationClock (not
    /// Time.timeScale) precisely so that this playback can still animate.
    /// </summary>
    [DisallowMultipleComponent]
    public class BattleArenaView : MonoBehaviour
    {
        [Header("Arena")]
        [Tooltip("Grid dimensions (columns x rows) of the battle floor.")]
        [SerializeField] private Vector2Int gridSize = new Vector2Int(11, 7);
        [SerializeField] private float cellSize = 1f;
        [Tooltip("Where in world space the arena scene is built. Far from the maze so the arena camera can't see maze geometry.")]
        [SerializeField] private Vector2 arenaWorldOrigin = new Vector2(0f, 10000f);

        [Header("Playback")]
        [Tooltip("Base tempo: seconds per combat event at 1x speed.")]
        [SerializeField, Min(0.02f)] private float secondsPerEvent = 0.4f;
        [SerializeField, Range(0.25f, 8f)] private float playbackSpeed = 1f;
        [Tooltip("Seconds the final result stays on screen before auto-returning to the maze (0 = wait for the button).")]
        [SerializeField, Min(0f)] private float autoReturnSeconds = 4f;

        /// <summary>Per-combatant playback state. DisplayHealth is a copy - never the real sheet.</summary>
        private class Slot
        {
            public Combatant Combatant;
            public Transform Transform;
            public SpriteRenderer Sprite;
            public Vector3 Home;
            public float DisplayHealth;
            public bool Felled;
        }

        private struct Floater
        {
            public Vector3 WorldPosition;
            public string Text;
            public Color Color;
            public float BornAt;
        }

        private readonly Dictionary<int, Slot> _slots = new Dictionary<int, Slot>();
        private readonly List<Floater> _floaters = new List<Floater>();
        private readonly List<string> _feed = new List<string>();
        private readonly List<Camera> _suspendedCameras = new List<Camera>();

        private Scene _scene;
        private bool _sceneLoaded;
        private GameObject _root;
        private Camera _camera;
        private PendingFight _fight;
        private BattleResult _result;
        private int _round;
        private bool _playbackFinished;
        private bool _skipRequested;
        private bool _returnRequested;
        private Vector2 _feedScroll;

        public bool IsBuilt => _sceneLoaded;

        /// <summary>Seconds per animation "beat" at the current playback speed.</summary>
        private float Beat => Mathf.Max(0.02f, secondsPerEvent) / Mathf.Max(0.25f, playbackSpeed);

        /// <summary>
        /// Builds the arena, replays the fight, waits for the observer, and tears everything back
        /// down. Yield on this from a coroutine; when it completes the maze is on screen again.
        /// </summary>
        public IEnumerator Play(PendingFight fight, IReadOnlyList<Combatant> combatants)
        {
            _fight = fight;
            _result = fight.Result;
            _skipRequested = false;
            _returnRequested = false;
            _playbackFinished = false;
            _round = 0;
            _feed.Clear();
            _floaters.Clear();

            Build(combatants);

            yield return Replay();

            ApplyFinalState();
            _playbackFinished = true;

            yield return WaitForObserver();

            Teardown();
        }

        // ---------------------------------------------------------------- build / teardown

        private void Build(IReadOnlyList<Combatant> combatants)
        {
            // A per-fight scene name: CreateScene refuses to make a second scene with a name
            // that's already loaded, and a previous arena may still be unloading.
            _scene = SceneManager.CreateScene($"CombatArena_{_fight.Id}_{Time.frameCount}");
            _sceneLoaded = true;

            _root = new GameObject("ArenaRoot");
            SceneManager.MoveGameObjectToScene(_root, _scene);
            _root.transform.position = arenaWorldOrigin;

            BuildFloor();
            BuildCamera();
            PlaceCombatants(combatants);
        }

        private void BuildFloor()
        {
            var floor = new GameObject("Floor");
            floor.transform.SetParent(_root.transform, false);

            for (int x = 0; x < gridSize.x; x++)
            {
                for (int y = 0; y < gridSize.y; y++)
                {
                    var tile = new GameObject($"Cell_{x}_{y}");
                    tile.transform.SetParent(floor.transform, false);
                    tile.transform.position = CellToWorld(x, y);
                    tile.transform.localScale = Vector3.one * (cellSize * 0.96f);

                    var sr = tile.AddComponent<SpriteRenderer>();
                    sr.sprite = RoomView.SharedSquareSprite;
                    sr.color = (x + y) % 2 == 0 ? new Color(0.16f, 0.17f, 0.2f) : new Color(0.21f, 0.22f, 0.26f);
                    sr.sortingOrder = 0;
                }
            }
        }

        private void BuildCamera()
        {
            var cameraGO = new GameObject("ArenaCamera");
            cameraGO.transform.SetParent(_root.transform, false);
            cameraGO.transform.position = new Vector3(arenaWorldOrigin.x, arenaWorldOrigin.y, -10f);

            _camera = cameraGO.AddComponent<Camera>();
            _camera.orthographic = true;
            _camera.backgroundColor = new Color(0.05f, 0.05f, 0.07f);
            _camera.clearFlags = CameraClearFlags.SolidColor;
            _camera.depth = 100f; // draw over anything else that somehow stays enabled

            float aspect = Mathf.Max(_camera.aspect, 0.01f);
            float halfHeight = gridSize.y * cellSize * 0.5f;
            float halfWidth = gridSize.x * cellSize * 0.5f;
            _camera.orthographicSize = Mathf.Max(halfHeight, halfWidth / aspect) * 1.35f;

            // Hide the maze by suspending its cameras rather than deactivating maze objects -
            // SetActive(false) on the maze root would permanently kill its spawn coroutines.
            _suspendedCameras.Clear();
            foreach (var cam in Camera.allCameras)
            {
                if (cam == _camera) continue;
                _suspendedCameras.Add(cam);
                cam.enabled = false;
            }
        }

        /// <summary>Agents line up on the left of the grid, monsters on the right, facing off.</summary>
        private void PlaceCombatants(IReadOnlyList<Combatant> combatants)
        {
            _slots.Clear();

            var agents = new List<Combatant>();
            var monsters = new List<Combatant>();
            foreach (var c in combatants)
                (c.Team == Combatant.TeamAgents ? agents : monsters).Add(c);

            LayoutTeam(agents, true);
            LayoutTeam(monsters, false);
        }

        private void LayoutTeam(List<Combatant> team, bool leftSide)
        {
            int rows = Mathf.Max(1, gridSize.y);

            for (int i = 0; i < team.Count; i++)
            {
                int column = i / rows;
                int indexInColumn = i % rows;
                int countInColumn = Mathf.Min(rows, team.Count - column * rows);

                int x = leftSide ? Mathf.Min(column, gridSize.x - 1) : Mathf.Max(0, gridSize.x - 1 - column);
                int y = (rows - countInColumn) / 2 + indexInColumn;

                _slots[team[i].Id] = CreateSlot(team[i], CellToWorld(x, y));
            }
        }

        private Slot CreateSlot(Combatant combatant, Vector3 position)
        {
            var go = new GameObject($"{(combatant.IsAgent ? "Agent" : "Monster")}_{combatant.Name}");
            go.transform.SetParent(_root.transform, false);
            go.transform.position = position;
            go.transform.localScale = Vector3.one * (cellSize * (combatant.IsAgent ? 0.58f : 0.5f));

            var sr = go.AddComponent<SpriteRenderer>();
            sr.sprite = RoomView.SharedSquareSprite;
            sr.color = combatant.Color;
            sr.sortingOrder = 2;

            return new Slot
            {
                Combatant = combatant,
                Transform = go.transform,
                Sprite = sr,
                Home = position,
                DisplayHealth = combatant.StartHealth
            };
        }

        private void Teardown()
        {
            foreach (var cam in _suspendedCameras)
                if (cam != null) cam.enabled = true;
            _suspendedCameras.Clear();

            _slots.Clear();
            _floaters.Clear();
            _camera = null;
            _root = null;

            if (_sceneLoaded && _scene.IsValid() && _scene.isLoaded)
                SceneManager.UnloadSceneAsync(_scene);

            _sceneLoaded = false;
            _fight = null;
            _result = null;
        }

        // ---------------------------------------------------------------- playback

        private IEnumerator Replay()
        {
            foreach (var e in _result.Events)
            {
                if (_skipRequested || _returnRequested) break;

                Feed(e.Text);

                switch (e.Kind)
                {
                    case CombatEventKind.Hit:
                    case CombatEventKind.Miss:
                        yield return Strike(e);
                        break;
                    case CombatEventKind.Death:
                        yield return Fell(e.TargetId);
                        break;
                    case CombatEventKind.RoundStart:
                        _round = e.Round;
                        yield return Hold(0.6f);
                        break;
                    default:
                        yield return Hold(1.2f);
                        break;
                }
            }
        }

        private IEnumerator Strike(CombatEvent e)
        {
            if (!_slots.TryGetValue(e.ActorId, out Slot actor) || !_slots.TryGetValue(e.TargetId, out Slot target))
            {
                yield return Hold(0.5f);
                yield break;
            }

            Vector3 lunge = Vector3.Lerp(actor.Home, target.Home, 0.5f);
            yield return Glide(actor, actor.Home, lunge, 0.45f);

            if (e.Kind == CombatEventKind.Hit)
            {
                target.DisplayHealth = Mathf.Max(0f, target.DisplayHealth - e.Amount);
                AddFloater(target, $"-{e.Amount:0.#}", new Color(1f, 0.45f, 0.4f));
                yield return Flash(target, new Color(1f, 0.35f, 0.35f));
            }
            else
            {
                AddFloater(target, "miss", new Color(0.85f, 0.85f, 0.85f));
                yield return Flash(target, Color.white);
            }

            yield return Glide(actor, lunge, actor.Home, 0.3f);
        }

        private IEnumerator Fell(int combatantId)
        {
            if (!_slots.TryGetValue(combatantId, out Slot slot)) yield break;

            slot.Felled = true;
            slot.DisplayHealth = 0f;

            Vector3 startScale = slot.Transform.localScale;
            Color startColor = slot.Sprite.color;
            float duration = Beat * 0.9f;

            for (float t = 0f; t < duration; t += Time.deltaTime)
            {
                if (_returnRequested) break;
                float k = Mathf.Clamp01(t / duration);
                slot.Transform.localScale = Vector3.Lerp(startScale, startScale * 0.35f, k);
                slot.Sprite.color = new Color(startColor.r * 0.4f, startColor.g * 0.4f, startColor.b * 0.4f, 1f - 0.65f * k);
                slot.Transform.rotation = Quaternion.Euler(0f, 0f, 90f * k);
                yield return null;
            }

            slot.Transform.localScale = startScale * 0.35f;
            slot.Sprite.color = new Color(startColor.r * 0.4f, startColor.g * 0.4f, startColor.b * 0.4f, 0.35f);
            slot.Transform.rotation = Quaternion.Euler(0f, 0f, 90f);
        }

        private IEnumerator Glide(Slot slot, Vector3 from, Vector3 to, float beats)
        {
            float duration = Beat * beats;
            for (float t = 0f; t < duration; t += Time.deltaTime)
            {
                if (_skipRequested || _returnRequested) break;
                slot.Transform.position = Vector3.Lerp(from, to, Mathf.Clamp01(t / duration));
                yield return null;
            }
            slot.Transform.position = to;
        }

        private IEnumerator Flash(Slot slot, Color flashColor)
        {
            Color original = slot.Sprite.color;
            slot.Sprite.color = flashColor;
            yield return Hold(0.35f);
            if (!slot.Felled) slot.Sprite.color = original;
        }

        private IEnumerator Hold(float beats)
        {
            float duration = Beat * beats;
            for (float t = 0f; t < duration; t += Time.deltaTime)
            {
                if (_skipRequested || _returnRequested) yield break;
                yield return null;
            }
        }

        /// <summary>
        /// Snaps every combatant to the true final state of the decided battle, so a skipped or
        /// interrupted playback still ends on an accurate picture.
        /// </summary>
        private void ApplyFinalState()
        {
            foreach (var slot in _slots.Values)
            {
                slot.DisplayHealth = slot.Combatant.Sheet.Stats.CurrentHealth;
                slot.Transform.position = slot.Home;

                if (!slot.Combatant.IsAlive && !slot.Felled)
                {
                    slot.Felled = true;
                    Color c = slot.Sprite.color;
                    slot.Sprite.color = new Color(c.r * 0.4f, c.g * 0.4f, c.b * 0.4f, 0.35f);
                    slot.Transform.localScale *= 0.35f;
                    slot.Transform.rotation = Quaternion.Euler(0f, 0f, 90f);
                }
                else if (!slot.Felled)
                {
                    slot.Sprite.color = slot.Combatant.Color;
                }
            }

            if (_skipRequested)
                Feed("(skipped to the end)");
            Feed(_result.Summary);
        }

        private IEnumerator WaitForObserver()
        {
            float waited = 0f;
            while (!_returnRequested)
            {
                if (autoReturnSeconds > 0f && waited >= autoReturnSeconds) break;
                waited += Time.deltaTime;
                yield return null;
            }
        }

        // ---------------------------------------------------------------- helpers & HUD

        private Vector3 CellToWorld(int x, int y)
        {
            float ox = (x - (gridSize.x - 1) * 0.5f) * cellSize;
            float oy = (y - (gridSize.y - 1) * 0.5f) * cellSize;
            return new Vector3(arenaWorldOrigin.x + ox, arenaWorldOrigin.y + oy, 0f);
        }

        private void AddFloater(Slot slot, string text, Color color)
        {
            _floaters.Add(new Floater
            {
                WorldPosition = slot.Home + Vector3.up * (cellSize * 0.5f),
                Text = text,
                Color = color,
                BornAt = Time.time
            });
        }

        private void Feed(string line)
        {
            if (string.IsNullOrEmpty(line)) return;
            _feed.Add(line);
            if (_feed.Count > 200) _feed.RemoveAt(0);
            _feedScroll.y = float.MaxValue; // keep pinned to the newest line
        }

        private void OnGUI()
        {
            if (!_sceneLoaded || _camera == null || _fight == null) return;

            DrawNameplates();
            DrawFloaters();
            DrawPanel();
        }

        private void DrawNameplates()
        {
            var style = new GUIStyle(GUI.skin.label) { alignment = TextAnchor.MiddleCenter, fontSize = 11 };

            foreach (var slot in _slots.Values)
            {
                Vector3 screen = _camera.WorldToScreenPoint(slot.Home);
                if (screen.z < 0f) continue;

                float max = slot.Combatant.MaxHealth;
                float fraction = Mathf.Clamp01(max > 0f ? slot.DisplayHealth / max : 0f);
                var rect = new Rect(screen.x - 55f, Screen.height - screen.y - 44f, 110f, 30f);

                GUI.color = slot.Felled ? new Color(0.6f, 0.6f, 0.6f) : Color.white;
                GUI.Label(rect, $"{slot.Combatant.Name}\n{slot.DisplayHealth:0}/{max:0}", style);
                GUI.color = Color.white;

                // Health bar under the nameplate.
                var barBack = new Rect(screen.x - 26f, Screen.height - screen.y - 16f, 52f, 5f);
                GUI.color = new Color(0f, 0f, 0f, 0.6f);
                GUI.DrawTexture(barBack, Texture2D.whiteTexture);
                GUI.color = slot.Combatant.IsAgent ? new Color(0.4f, 0.9f, 0.5f) : new Color(0.9f, 0.4f, 0.4f);
                GUI.DrawTexture(new Rect(barBack.x, barBack.y, barBack.width * fraction, barBack.height), Texture2D.whiteTexture);
                GUI.color = Color.white;
            }
        }

        private void DrawFloaters()
        {
            const float lifetime = 1.1f;
            var style = new GUIStyle(GUI.skin.label) { alignment = TextAnchor.MiddleCenter, fontStyle = FontStyle.Bold };

            for (int i = _floaters.Count - 1; i >= 0; i--)
            {
                Floater floater = _floaters[i];
                float age = Time.time - floater.BornAt;
                if (age > lifetime)
                {
                    _floaters.RemoveAt(i);
                    continue;
                }

                Vector3 screen = _camera.WorldToScreenPoint(floater.WorldPosition);
                if (screen.z < 0f) continue;

                GUI.color = new Color(floater.Color.r, floater.Color.g, floater.Color.b, 1f - age / lifetime);
                GUI.Label(new Rect(screen.x - 40f, Screen.height - screen.y - 30f - age * 25f, 80f, 20f), floater.Text, style);
                GUI.color = Color.white;
            }
        }

        private void DrawPanel()
        {
            const float width = 380f;
            GUILayout.BeginArea(new Rect(Screen.width - width - 10f, 10f, width, Screen.height - 20f), GUI.skin.box);

            GUILayout.Label($"FIGHT #{_fight.Id} - room {_fight.Room.Id}");
            GUILayout.Label(_playbackFinished
                ? _result.Summary
                : $"Round {_round} / max - {_fight.Agents.Count} agent(s) vs {_result.Combatants.Count - _fight.Agents.Count} monster(s)");

            GUILayout.BeginHorizontal();
            GUILayout.Label("Speed", GUILayout.Width(45f));
            playbackSpeed = GUILayout.HorizontalSlider(playbackSpeed, 0.25f, 8f);
            GUILayout.Label($"{playbackSpeed:0.0}x", GUILayout.Width(40f));
            GUILayout.EndHorizontal();

            if (!_playbackFinished)
            {
                if (GUILayout.Button("Skip to end")) _skipRequested = true;
            }
            else if (GUILayout.Button("Return to the maze"))
            {
                _returnRequested = true;
            }

            GUILayout.Space(6f);
            GUILayout.Label("Blow by blow:");
            _feedScroll = GUILayout.BeginScrollView(_feedScroll);
            foreach (var line in _feed)
                GUILayout.Label(line);
            GUILayout.EndScrollView();

            GUILayout.EndArea();
        }
    }
}