using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using TMPro;
using UnityEngine;

namespace AibisDream.Framework
{
    public static class TypographyService
    {
        private static readonly HashSet<LocalizedTypography> Bindings = new();
        private static ITypographyProfileLoader loader;
        private static int switchVersion;
        private static string currentProfileKey;
        private static string latestRequestedProfileKey;
        private static TypographyProfile currentProfile;

        public static TypographyProfile CurrentProfile => currentProfile;
        public static bool IsReady => currentProfile != null;
        public static string CurrentProfileKey => currentProfileKey;

        public static void ConfigureLoader(ITypographyProfileLoader profileLoader)
        {
            loader = profileLoader ?? throw new ArgumentNullException(nameof(profileLoader));
        }

        public static bool IsActiveFor(LocaleKind localeKind) =>
            currentProfile != null &&
            string.Equals(
                currentProfileKey,
                TypographyLocaleMapping.GetProfileKey(localeKind),
                StringComparison.Ordinal);

        public static TypographyStyle Resolve(TypographyRole role) => currentProfile?.Resolve(role);

        public static bool Apply(TMP_Text text, TypographyRole role, bool applyMetrics = true)
        {
            if (text == null)
                return false;

            TypographyStyle style = Resolve(role);
            if (style == null || !style.IsUsable)
                return false;

            ApplyStyle(text, style, applyMetrics, text.fontSize, text.lineSpacing, text.characterSpacing);
            return true;
        }

        public static void Register(LocalizedTypography binding)
        {
            if (binding == null)
                return;

            Bindings.Add(binding);
            if (currentProfile != null)
                binding.ApplyProfile(currentProfile);
        }

        public static void Unregister(LocalizedTypography binding)
        {
            if (binding != null)
                Bindings.Remove(binding);
        }

        public static async Task<bool> LoadAndActivateAsync(LocaleKind localeKind)
        {
            int requestVersion = ++switchVersion;
            string profileKey = TypographyLocaleMapping.GetProfileKey(localeKind);
            latestRequestedProfileKey = profileKey;

            if (IsActiveFor(localeKind))
                return true;
            if (loader == null)
            {
                Debug.LogError("[TypographyService] 尚未配置 ITypographyProfileLoader。");
                return false;
            }

            TypographyProfile loadedProfile;
            try
            {
                loadedProfile = await loader.LoadAsync(profileKey);
            }
            catch (Exception exception)
            {
                Debug.LogError($"[TypographyService] 加载字体 Profile 失败：{profileKey}\n{exception}");
                return false;
            }

            if (requestVersion != switchVersion)
            {
                if (!string.Equals(profileKey, currentProfileKey, StringComparison.Ordinal) &&
                    !string.Equals(profileKey, latestRequestedProfileKey, StringComparison.Ordinal))
                {
                    loader.Release(profileKey);
                }
                return false;
            }
            if (loadedProfile == null)
            {
                Debug.LogError($"[TypographyService] 字体 Profile 不存在或加载失败：{profileKey}");
                return false;
            }

            string previousKey = currentProfileKey;
            loadedProfile.ApplyFallbacks();
            currentProfile = loadedProfile;
            currentProfileKey = profileKey;
            RefreshBindings();
            Canvas.ForceUpdateCanvases();

            await Task.Yield();
            if (!string.IsNullOrEmpty(previousKey) &&
                !string.Equals(previousKey, profileKey, StringComparison.Ordinal))
            {
                loader.Release(previousKey);
            }

            return true;
        }

        internal static void ApplyStyle(
            TMP_Text text,
            TypographyStyle style,
            bool applyMetrics,
            float baseFontSize,
            float baseLineSpacing,
            float baseCharacterSpacing)
        {
            text.font = style.Font;
            text.fontSharedMaterial = style.MaterialPreset != null
                ? style.MaterialPreset
                : style.Font.material;

            if (applyMetrics)
            {
                text.fontSize = baseFontSize * style.FontSizeMultiplier;
                text.lineSpacing = baseLineSpacing + style.LineSpacingOffset;
                text.characterSpacing = baseCharacterSpacing + style.CharacterSpacingOffset;
            }

            text.SetAllDirty();
            if (text.gameObject.activeInHierarchy)
                text.ForceMeshUpdate();
        }

        private static void RefreshBindings()
        {
            if (Bindings.Count == 0)
                return;

            var stale = new List<LocalizedTypography>();
            foreach (LocalizedTypography binding in Bindings)
            {
                if (binding == null)
                    stale.Add(binding);
                else
                    binding.ApplyProfile(currentProfile);
            }

            foreach (LocalizedTypography binding in stale)
                Bindings.Remove(binding);
        }

#if UNITY_EDITOR
        public static void ResetForTests()
        {
            if (loader != null && !string.IsNullOrEmpty(currentProfileKey))
                loader.Release(currentProfileKey);
            loader = null;
            currentProfile = null;
            currentProfileKey = null;
            latestRequestedProfileKey = null;
            switchVersion++;
            Bindings.Clear();
        }
#endif
    }
}