using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.Extensions.Localization;
using Sozsoft.Languages.Entities;
using Volo.Abp.Caching;
using Volo.Abp.DependencyInjection;
using Volo.Abp.Domain.Repositories;
using Volo.Abp.Localization;
using Volo.Abp.Threading;

namespace Sozsoft.Languages.Localization;

public class DatabaseResourceLocalizer : IDatabaseResourceLocalizer, ISingletonDependency
{
    // Her metin aramasında sözlüğün tamamı Redis'ten çekilip çözülüyordu. Süreç içi katman bunu önler.
    // Kısa ömürlüdür: metinlerin bir kısmı ham SQL ile yazılır (olay üretmez) ve diğer API örnekleri ile
    // DbMigrator ayrı süreçtir; onların temizliği buraya en geç bu süre sonunda yansır.
    private static readonly long LocalCacheDurationMs = (long)TimeSpan.FromSeconds(30).TotalMilliseconds;

    private readonly IRepository<LanguageText, Guid> languageTextRepository;
    private readonly IDistributedCache<LanguageTextCacheItem> cache;
    private readonly ConcurrentDictionary<string, (LanguageTextCacheItem Item, long ExpiresAt)> localCache = new();

    public DatabaseResourceLocalizer(
        IRepository<LanguageText, Guid> languageTextRepository,
        IDistributedCache<LanguageTextCacheItem> cache)
    {
        this.languageTextRepository = languageTextRepository;
        this.cache = cache;
    }

    public LocalizedString GetOrNull(LocalizationResourceBase resource, string cultureName, string name)
    {
        var value = GetCacheItem(resource, cultureName)?.Dictionary?.GetOrDefault(name);
        return value == null ? null : new LocalizedString(name, value);
    }

    /// <summary>Süreç içi katmanı boşaltır; dağıtık önbellek temizlendiğinde ve metin değiştiğinde çağrılır.</summary>
    public void ClearLocalCache() => localCache.Clear();

    protected LanguageTextCacheItem GetCacheItem(LocalizationResourceBase resource, string cultureName)
    {
        // culture, resource, key
        var key = LanguageTextCacheItem.CalculateCacheKey(resource.ResourceName, cultureName);
        if (TryGetLocal(key, out var local))
        {
            return local;
        }

        return SetLocal(key, cache.GetOrAdd(key, () => CreateCacheItem(resource, cultureName)));
    }

    private bool TryGetLocal(string key, out LanguageTextCacheItem item)
    {
        if (localCache.TryGetValue(key, out var entry) && entry.ExpiresAt > Environment.TickCount64)
        {
            item = entry.Item;
            return true;
        }

        item = null;
        return false;
    }

    private LanguageTextCacheItem SetLocal(string key, LanguageTextCacheItem item)
    {
        if (item != null)
        {
            localCache[key] = (item, Environment.TickCount64 + LocalCacheDurationMs);
        }

        return item;
    }

    public void Fill(LocalizationResourceBase resource, string cultureName, Dictionary<string, LocalizedString> dictionary)
    {
        var item = GetCacheItem(resource, cultureName);

        foreach (var kvp in item?.Dictionary ?? [])
        {
            dictionary[kvp.Key] = new LocalizedString(kvp.Key, kvp.Value);
        }
    }

    protected virtual LanguageTextCacheItem CreateCacheItem(LocalizationResourceBase resource, string cultureName)
    {
        var task = languageTextRepository.GetListAsync(a => a.ResourceName == resource.ResourceName && a.CultureName == cultureName);
        var texts = AsyncHelper.RunSync(() => task);

        return new LanguageTextCacheItem
        {
            Dictionary = texts.ToDictionary(a => a.Key, a => a.Value)
        };
    }

    public async Task FillAsync(LocalizationResourceBase resource, string cultureName, Dictionary<string, LocalizedString> dictionary)
    {
        var key = LanguageTextCacheItem.CalculateCacheKey(resource.ResourceName, cultureName);
        if (!TryGetLocal(key, out var item))
        {
            item = SetLocal(key, await cache.GetOrAddAsync(key, () => CreateCacheItemAsync(resource, cultureName)));
        }

        foreach (var kvp in item?.Dictionary ?? [])
        {
            dictionary[kvp.Key] = new LocalizedString(kvp.Key, kvp.Value);
        }
    }

    protected virtual async Task<LanguageTextCacheItem> CreateCacheItemAsync(LocalizationResourceBase resource, string cultureName)
    {
        var texts = await languageTextRepository.GetListAsync(a => a.ResourceName == resource.ResourceName && a.CultureName == cultureName);

        return new LanguageTextCacheItem
        {
            Dictionary = texts.ToDictionary(a => a.Key, a => a.Value)
        };
    }
}