using UnityEngine;
using UnityEngine.UI;
using TMPro;

namespace BaseGames.UI.Theme
{
    /// <summary>
    /// 将 <see cref="UIThemeSO"/> 中的视觉令牌应用到当前 GameObject 及其子节点。
    ///
    /// 用法：
    ///   1. 在 Prefab 根节点挂载此组件并指定 <see cref="_theme"/>；
    ///   2. 在每个需要主题化的子节点添加 <see cref="UIThemeRole"/> 组件指定角色；
    ///   3. <see cref="Apply"/> 会被 <see cref="OnEnable"/> 自动调用一次，
    ///      也可在主题切换后手动调用。
    ///
    /// 性能：使用 <see cref="Component.GetComponentsInChildren{T}(bool)"/> 一次性收集，
    /// 仅在 Enable / 显式刷新时执行；运行时无每帧成本。
    /// </summary>
    [DisallowMultipleComponent]
    public class UIThemeApplier : MonoBehaviour
    {
        [SerializeField] private UIThemeSO _theme;
        [Tooltip("启用时自动应用一次。运行时切换主题可手动调用 Apply()。")]
        [SerializeField] private bool _applyOnEnable = true;

        private void OnEnable()
        {
            if (_applyOnEnable) Apply();
        }

        /// <summary>用当前 <see cref="_theme"/> 覆盖子节点上所有 <see cref="UIThemeRole"/> 标记。</summary>
        public void Apply()
        {
            if (_theme == null) return;

            var roles = GetComponentsInChildren<UIThemeRole>(includeInactive: true);
            for (int i = 0; i < roles.Length; i++)
                ApplyRole(roles[i], _theme);
        }

        /// <summary>运行时切换主题。</summary>
        public void SetTheme(UIThemeSO theme)
        {
            _theme = theme;
            Apply();
        }

        private static void ApplyRole(UIThemeRole role, UIThemeSO theme)
        {
            if (role == null) return;
            switch (role.Kind)
            {
                case UIThemeRoleKind.Graphic_Primary:    SetGraphicColor(role, theme.Primary);    break;
                case UIThemeRoleKind.Graphic_Secondary:  SetGraphicColor(role, theme.Secondary);  break;
                case UIThemeRoleKind.Graphic_Accent:     SetGraphicColor(role, theme.Accent);     break;
                case UIThemeRoleKind.Graphic_Background: SetGraphicColor(role, theme.Background); break;
                case UIThemeRoleKind.Graphic_Success:    SetGraphicColor(role, theme.Success);    break;
                case UIThemeRoleKind.Graphic_Warning:    SetGraphicColor(role, theme.Warning);    break;
                case UIThemeRoleKind.Graphic_Danger:     SetGraphicColor(role, theme.Danger);     break;

                case UIThemeRoleKind.Text_Primary:   SetTextStyle(role, theme.TextPrimary,   theme.BodyFont,   theme.BodyFontSize);   break;
                case UIThemeRoleKind.Text_Secondary: SetTextStyle(role, theme.TextSecondary, theme.BodyFont,   theme.SmallFontSize);  break;
                case UIThemeRoleKind.Text_Header:    SetTextStyle(role, theme.TextPrimary,   theme.HeaderFont, theme.HeaderFontSize); break;
                case UIThemeRoleKind.Text_Disabled:  SetTextStyle(role, theme.TextDisabled,  theme.BodyFont,   theme.BodyFontSize);   break;

                case UIThemeRoleKind.Button:         SetButtonColors(role, theme); break;
            }
        }

        private static void SetGraphicColor(UIThemeRole role, Color c)
        {
            var g = role.GetComponent<Graphic>();
            if (g != null) g.color = c;
        }

        private static void SetTextStyle(UIThemeRole role, Color c, TMP_FontAsset font, float size)
        {
            var tmp = role.GetComponent<TMP_Text>();
            if (tmp != null)
            {
                tmp.color = c;
                if (font != null) tmp.font = font;
                if (role.OverrideFontSize) tmp.fontSize = size;
            }
        }

        private static void SetButtonColors(UIThemeRole role, UIThemeSO theme)
        {
            var btn = role.GetComponent<Button>();
            if (btn == null) return;
            var cb = btn.colors;
            cb.normalColor      = theme.ButtonNormal;
            cb.highlightedColor = theme.ButtonHighlighted;
            cb.pressedColor     = theme.ButtonPressed;
            cb.disabledColor    = theme.ButtonDisabled;
            btn.colors = cb;
        }
    }
}