using System;
using System.Collections.Generic;
using Luneraria.Core;
using UnityEngine;
using UnityEngine.Rendering;

namespace Luneraria.View
{
    /// <summary>
    /// What a unit looks like (port of AssetLibrary.instantiate_fighter): the model id is the
    /// unit definition's id (troops, monsters, heroes and champions carry their model there), the
    /// boss is the Schlundkrone. Skinned figures (Ringborke for w04, Basaltbastion for g04, ...)
    /// replace the rigid Phase-4 model of the same id, as in Godot. Rigid models keep their named
    /// parts in the FBX; at first use they are combined into one mesh per material and cached
    /// (Godot's rig groups did the same at load time).
    /// </summary>
    public sealed class LuneUnitLibrary : ScriptableObject
    {
        [Serializable]
        public sealed class UnitModel
        {
            public string Id;
            public GameObject Prefab;
            /// <summary>Set for skinned figures; rigid models have none.</summary>
            public RuntimeAnimatorController Controller;
        }

        public List<UnitModel> Models = new List<UnitModel>();
        public string BossModel = "schlundkrone";
        public string FallbackModel = "g01";
        public LuneMaterialSet Materials;
        public LuneGround Ground;
        public Mesh RingRound;
        public Mesh RingDiamond;
        public Mesh RingHexagon;
        public Mesh Quad;
        public Material[] TeamRing = new Material[3];
        public Material HeroRing;
        public Material BarBack;
        public Material[] BarFill = new Material[3];
        public Material[] Bolt = new Material[3];
        /// <summary>Wide owner ring of a deployed boss (lune_unit_view.gd, G3): round for Blau, diamond for Rot.</summary>
        public Mesh OwnerRingRound;
        public Mesh OwnerRingDiamond;
        public Material[] OwnerRing = new Material[2];
        /// <summary>Fill of the Ancients' health bars (team light colour, lune_ancient_view.gd).</summary>
        public Material[] AncientBarFill = new Material[2];

        Dictionary<string, UnitModel> _index;
        readonly Dictionary<GameObject, GameObject> _combined = new Dictionary<GameObject, GameObject>();

        public UnitModel Find(string id)
        {
            if (_index == null)
            {
                _index = new Dictionary<string, UnitModel>();
                foreach (UnitModel model in Models)
                    _index[model.Id] = model;
            }
            _index.TryGetValue(id, out UnitModel found);
            return found;
        }

        /// <summary>Model id of a unit: the boss model for bosses, otherwise the definition id.</summary>
        public string ModelId(LuneUnit unit)
        {
            return unit.Kind == "boss" ? BossModel : unit.Def.Id;
        }

        public GameObject PrefabFor(LuneUnit unit, out RuntimeAnimatorController controller)
        {
            UnitModel model = Find(ModelId(unit)) ?? Find(FallbackModel);
            controller = model.Controller;
            return controller != null ? model.Prefab : Combined(model.Prefab);
        }

        /// <summary>One-mesh template of a rigid figure (parts merged per material), built once.</summary>
        GameObject Combined(GameObject source)
        {
            if (_combined.TryGetValue(source, out GameObject template) && template != null)
                return template;
            var groups = new Dictionary<Material, List<CombineInstance>>();
            var order = new List<Material>();
            foreach (MeshFilter filter in source.GetComponentsInChildren<MeshFilter>(true))
            {
                Material[] slots = filter.GetComponent<MeshRenderer>().sharedMaterials;
                Matrix4x4 toRoot = source.transform.worldToLocalMatrix * filter.transform.localToWorldMatrix;
                for (int sub = 0; sub < filter.sharedMesh.subMeshCount; sub++)
                {
                    Material material = slots[Mathf.Min(sub, slots.Length - 1)];
                    if (!groups.TryGetValue(material, out List<CombineInstance> list))
                    {
                        groups[material] = list = new List<CombineInstance>();
                        order.Add(material);
                    }
                    list.Add(new CombineInstance { mesh = filter.sharedMesh, subMeshIndex = sub, transform = toRoot });
                }
            }
            var parts = new CombineInstance[order.Count];
            for (int i = 0; i < order.Count; i++)
            {
                var merged = new Mesh { indexFormat = IndexFormat.UInt32 };
                merged.CombineMeshes(groups[order[i]].ToArray(), true, true);
                parts[i] = new CombineInstance { mesh = merged, transform = Matrix4x4.identity };
            }
            var mesh = new Mesh { name = source.name + "_combined", indexFormat = IndexFormat.UInt32 };
            mesh.CombineMeshes(parts, false, false);
            mesh.RecalculateBounds();
            foreach (CombineInstance part in parts)
            {
                if (Application.isPlaying)
                    Destroy(part.mesh);
                else
                    DestroyImmediate(part.mesh);
            }
            template = new GameObject(source.name + "_combined") { hideFlags = HideFlags.HideAndDontSave };
            template.SetActive(false);
            template.AddComponent<MeshFilter>().sharedMesh = mesh;
            template.AddComponent<MeshRenderer>().sharedMaterials = order.ToArray();
            _combined[source] = template;
            return template;
        }
    }
}