using System;
using System.Collections.Generic;
using Cielonos.Settings;
using SLSUtilities.UI;
using UnityEngine;
using UnityEngine.InputSystem;
using UnityEngine.UI;

namespace Cielonos.Settings.UI
{
    /// <summary>
    /// 键位绑定二级 UIPage。
    /// <para>
    /// 从 <see cref="InputActionAsset"/> 读取所有可绑定的 Action，
    /// 为每个 Action 生成一行 <see cref="SettingsEntryKeyBinding"/>。
    /// Composite 类型的 Action（如 WASD Move）的每个 part 单独显示一行。
    /// </para>
    /// <para>
    /// 此页面是 <see cref="UIPageBase"/>，需手动关闭（Back 按钮或 ESC）。
    /// 关闭时自动将绑定覆盖保存到 <see cref="ControlsSettings.bindingOverridesJson"/>。
    /// </para>
    /// </summary>
    public class KeyBindingPage : UIPageBase
    {
        [Header("Prefabs")]
        [Tooltip("键位绑定条目预制体，需挂载 SettingsEntryKeyBinding。")]
        [SerializeField] private GameObject keyBindingEntryPrefab;

        [Tooltip("分组标题预制体（可选），用于分隔不同 ActionMap。")]
        [SerializeField] private GameObject sectionHeaderPrefab;

        [Header("Content")]
        [Tooltip("条目的父容器，应挂载 VerticalLayoutGroup。")]
        [SerializeField] private RectTransform contentContainer;

        [Header("Buttons")]
        [SerializeField] private Button resetAllButton;
        [SerializeField] private Button backButton;

        [Header("Input")]
        [Tooltip("要显示的 InputActionAsset。为空时从 GameSettingsManager 上下文获取。")]
        [SerializeField] private InputActionAsset inputActionAsset;

        [Tooltip("要显示的 Control Scheme 名称。")]
        [SerializeField] private string controlScheme = "KeyboardMouse";

        private readonly List<SettingsEntryKeyBinding> activeEntries = new();
        private readonly List<GameObject> spawnedObjects = new();

        /// <summary>当任何绑定变更时触发（供 SettingsUIPage 监听）。</summary>
        public event Action OnAnyBindingChanged;

        // ──────────────────── 生命周期 ────────────────────

        protected override void Start()
        {
            base.Start();

            resetAllButton?.onClick.AddListener(OnResetAllClicked);
            backButton?.onClick.AddListener(OnBackClicked);
        }

        /// <summary>
        /// 使用指定的 InputActionAsset 打开键位绑定页面。
        /// </summary>
        public void Open(InputActionAsset asset)
        {
            inputActionAsset = asset;
            Open();
        }

        protected override void OnPageOpened()
        {
            BuildEntries();
        }

        protected override void OnPageClosed()
        {
            SaveBindingOverrides();
            ClearAll();
        }

        // ──────────────────── 条目生成 ────────────────────

        private void BuildEntries()
        {
            ClearAll();

            if (inputActionAsset == null)
            {
                Debug.LogError("[KeyBindingPage] InputActionAsset is not assigned.");
                return;
            }

            foreach (InputActionMap map in inputActionAsset.actionMaps)
            {
                bool hasBindableAction = false;

                foreach (InputAction action in map.actions)
                {
                    if (HasBindableBindings(action))
                    {
                        hasBindableAction = true;
                        break;
                    }
                }

                if (!hasBindableAction) continue;

                // 插入 ActionMap 标题
                SpawnSectionHeader(FormatMapName(map.name));

                foreach (InputAction action in map.actions)
                {
                    SpawnEntriesForAction(action);
                }
            }
        }

        /// <summary>
        /// 为一个 Action 生成绑定条目。
        /// Composite binding 的每个 part 生成独立条目；普通 binding 生成一个条目。
        /// </summary>
        private void SpawnEntriesForAction(InputAction action)
        {
            var bindings = action.bindings;

            for (int i = 0; i < bindings.Count; i++)
            {
                InputBinding binding = bindings[i];

                // 跳过不匹配 controlScheme 的绑定
                if (!IsBindingMatchingScheme(binding))
                    continue;

                if (binding.isComposite)
                {
                    // composite 的 header，不生成条目，但后续 parts 会单独生成
                    continue;
                }

                if (binding.isPartOfComposite)
                {
                    // composite 的一个 part，显示为 "ActionName - PartName"
                    string displayName = $"{FormatActionName(action.name)} - {FormatActionName(binding.name)}";
                    SpawnKeyBindingEntry(action, i, displayName);
                }
                else
                {
                    // 普通（非 composite）binding
                    SpawnKeyBindingEntry(action, i, FormatActionName(action.name));
                }
            }
        }

        private void SpawnKeyBindingEntry(InputAction action, int bindingIndex, string displayName)
        {
            if (keyBindingEntryPrefab == null) return;

            GameObject entryObj = Instantiate(keyBindingEntryPrefab, contentContainer);
            var entry = entryObj.GetComponent<SettingsEntryKeyBinding>();
            if (entry == null)
            {
                Debug.LogError("[KeyBindingPage] keyBindingEntryPrefab is missing SettingsEntryKeyBinding.");
                Destroy(entryObj);
                return;
            }

            entry.Initialize(action, bindingIndex, displayName);
            entry.OnBindingChanged += OnEntryBindingChanged;
            activeEntries.Add(entry);
            spawnedObjects.Add(entryObj);
        }

        private void SpawnSectionHeader(string title)
        {
            if (sectionHeaderPrefab == null) return;

            GameObject headerObj = Instantiate(sectionHeaderPrefab, contentContainer);
            var headerText = headerObj.GetComponentInChildren<TMPro.TMP_Text>();
            if (headerText != null)
                headerText.text = title;

            spawnedObjects.Add(headerObj);
        }

        // ──────────────────── 绑定变更 ────────────────────

        private void OnEntryBindingChanged()
        {
            OnAnyBindingChanged?.Invoke();
        }

        /// <summary>
        /// 将当前绑定覆盖序列化到 <see cref="ControlsSettings.bindingOverridesJson"/>，
        /// 并重新初始化 <see cref="InputBindingResolver"/>。
        /// </summary>
        private void SaveBindingOverrides()
        {
            if (inputActionAsset == null) return;

            var manager = GameSettingsManager.Instance;
            if (manager != null)
            {
                manager.controls.bindingOverridesJson = inputActionAsset.SaveBindingOverridesAsJson();
                manager.Save();
            }

            // 重新初始化 glyph 解析器以反映新的绑定
            InputBindingResolver.Initialize(inputActionAsset, controlScheme);
        }

        // ──────────────────── 按钮回调 ────────────────────

        private void OnResetAllClicked()
        {
            if (inputActionAsset == null) return;

            inputActionAsset.RemoveAllBindingOverrides();

            // 重建条目以刷新显示
            BuildEntries();
            OnAnyBindingChanged?.Invoke();
        }

        private void OnBackClicked()
        {
            Close();
        }

        // ──────────────────── 工具方法 ────────────────────

        private bool HasBindableBindings(InputAction action)
        {
            foreach (InputBinding binding in action.bindings)
            {
                if (binding.isComposite) continue;
                if (IsBindingMatchingScheme(binding))
                    return true;
            }
            return false;
        }

        private bool IsBindingMatchingScheme(InputBinding binding)
        {
            if (string.IsNullOrEmpty(controlScheme)) return true;
            if (string.IsNullOrEmpty(binding.groups)) return false;
            return binding.groups.Contains(controlScheme);
        }

        private static string FormatActionName(string name)
        {
            if (string.IsNullOrEmpty(name)) return name;

            var sb = new System.Text.StringBuilder(name.Length + 4);
            sb.Append(char.ToUpper(name[0]));

            for (int i = 1; i < name.Length; i++)
            {
                char c = name[i];
                if (char.IsUpper(c) && i > 0 && char.IsLower(name[i - 1]))
                    sb.Append(' ');
                sb.Append(c);
            }

            return sb.ToString();
        }

        private static string FormatMapName(string mapName)
        {
            return FormatActionName(mapName);
        }

        // ──────────────────── 清理 ────────────────────────

        private void ClearAll()
        {
            foreach (var entry in activeEntries)
            {
                if (entry != null)
                    entry.OnBindingChanged -= OnEntryBindingChanged;
            }
            activeEntries.Clear();

            foreach (var obj in spawnedObjects)
            {
                if (obj != null)
                    Destroy(obj);
            }
            spawnedObjects.Clear();
        }
    }
}