using System;
using System.Collections.Concurrent;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using FinlyticCore.Entities.Settings;
using FinlyticCore.Models.Settings;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

namespace FinlyticCore.Services;

public interface ISettingsService<TContext> where TContext : DbContext
{
    // --- 1. Typsicherer Zugriff über SettingKey<T> (Empfohlen) ---
    Task<T> GetSettingAsync<T>(SettingKey<T> key,
        CancellationToken cancellationToken = default);

    Task SetSettingAsync<T>(SettingKey<T> key, T value,
        CancellationToken cancellationToken = default);

    // --- 2. Dynamischer Zugriff über Enum-Key ---
    Task<T> GetSettingAsync<TEnum, T>(TEnum enumKey, T defaultValue = default!,
        CancellationToken cancellationToken = default) where TEnum : struct, Enum;

    Task SetSettingAsync<TEnum, T>(TEnum enumKey, T value,
        CancellationToken cancellationToken = default) where TEnum : struct, Enum;

    // --- 3. Dynamischer Zugriff über String-Key ---
    Task<T> GetSettingAsync<T>(string key, T defaultValue = default!,
        CancellationToken cancellationToken = default);

    Task SetSettingAsync<T>(string key, T value,
        CancellationToken cancellationToken = default);
}

public class SettingsService<TContext> : ISettingsService<TContext> where TContext : DbContext
{
    private readonly Microsoft.Extensions.DependencyInjection.IServiceScopeFactory _scopeFactory;
    private readonly ILogger<SettingsService<TContext>>? _logger;

    // Fast In-Memory Cache: Key Schema: "KeyName"
    private readonly ConcurrentDictionary<string, string> _cache = new();

    public SettingsService(Microsoft.Extensions.DependencyInjection.IServiceScopeFactory scopeFactory, ILogger<SettingsService<TContext>>? logger = null)
    {
        _scopeFactory = scopeFactory;
        _logger = logger;
    }

    #region SettingKey<T> Overloads

    public Task<T> GetSettingAsync<T>(SettingKey<T> key, CancellationToken cancellationToken = default)
    {
        return GetSettingInternalAsync(key.Name, key.DefaultValue, cancellationToken);
    }

    public Task SetSettingAsync<T>(SettingKey<T> key, T value, CancellationToken cancellationToken = default)
    {
        return SetSettingInternalAsync(key.Name, value, cancellationToken);
    }

    #endregion

    #region Enum-Key Overloads

    public Task<T> GetSettingAsync<TEnum, T>(TEnum enumKey, T defaultValue = default!,
        CancellationToken cancellationToken = default)
        where TEnum : struct, Enum
    {
        var keyName = $"{typeof(TEnum).Name}.{enumKey}";
        return GetSettingInternalAsync(keyName, defaultValue, cancellationToken);
    }

    public Task SetSettingAsync<TEnum, T>(TEnum enumKey, T value, CancellationToken cancellationToken = default)
        where TEnum : struct, Enum
    {
        var keyName = $"{typeof(TEnum).Name}.{enumKey}";
        return SetSettingInternalAsync(keyName, value, cancellationToken);
    }

    #endregion

    #region String-Key Overloads

    public Task<T> GetSettingAsync<T>(string key, T defaultValue = default!,
        CancellationToken cancellationToken = default)
    {
        return GetSettingInternalAsync(key, defaultValue, cancellationToken);
    }

    public Task SetSettingAsync<T>(string key, T value, CancellationToken cancellationToken = default)
    {
        return SetSettingInternalAsync(key, value, cancellationToken);
    }

    #endregion

    #region Core Engine Logik

    private async Task<T> GetSettingInternalAsync<T>(string key, T defaultValue, CancellationToken cancellationToken)
    {
        // 1. Zuerst im In-Memory Cache prüfen
        if (_cache.TryGetValue(key, out var cachedJson))
        {
            return DeserializeValue(cachedJson, defaultValue);
        }

        try
        {
            using var scope = _scopeFactory.CreateScope();
            var dbContext = Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService<TContext>(scope.ServiceProvider);

            // 2. Aus DB der spezifischen TContext-Instanz laden
            var entity = await dbContext.Set<SettingEntity>()
                .FirstOrDefaultAsync(s => s.Key == key, cancellationToken);

            // 3. Falls noch nicht vorhanden: In DB anlegen (Seed on Demand)
            if (entity == null)
            {
                var defaultJson = JsonSerializer.Serialize(defaultValue);
                entity = new SettingEntity
                {
                    Key = key,
                    ValueJson = defaultJson,
                    LastUpdatedUtc = DateTime.UtcNow
                };

                dbContext.Set<SettingEntity>().Add(entity);
                await dbContext.SaveChangesAsync(cancellationToken);

                _cache[key] = defaultJson;
                return defaultValue;
            }

            // In Cache legen & Wert zurückgeben
            _cache[key] = entity.ValueJson;
            return DeserializeValue(entity.ValueJson, defaultValue);
        }
        catch (Exception ex)
        {
            _logger?.LogWarning(ex, "Setting '{Key}' could not be loaded or initialized in DB. Using default value in memory.", key);
            _cache[key] = JsonSerializer.Serialize(defaultValue);
            return defaultValue;
        }
    }

    private async Task SetSettingInternalAsync<T>(string key, T value, CancellationToken cancellationToken)
    {
        var jsonValue = JsonSerializer.Serialize(value);

        try
        {
            using var scope = _scopeFactory.CreateScope();
            var dbContext = Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService<TContext>(scope.ServiceProvider);

            var entity = await dbContext.Set<SettingEntity>()
                .FirstOrDefaultAsync(s => s.Key == key, cancellationToken);

            if (entity == null)
            {
                entity = new SettingEntity
                {
                    Key = key,
                    ValueJson = jsonValue,
                    LastUpdatedUtc = DateTime.UtcNow
                };
                dbContext.Set<SettingEntity>().Add(entity);
            }
            else
            {
                entity.ValueJson = jsonValue;
                entity.LastUpdatedUtc = DateTime.UtcNow;
            }

            await dbContext.SaveChangesAsync(cancellationToken);
        }
        catch (Exception ex)
        {
            _logger?.LogWarning(ex, "Setting '{Key}' could not be saved to DB.", key);
        }

        // Cache trotzdem aktualisieren
        _cache[key] = jsonValue;
    }

    private static T DeserializeValue<T>(string json, T defaultValue)
    {
        try
        {
            var result = JsonSerializer.Deserialize<T>(json);
            return result ?? defaultValue;
        }
        catch
        {
            return defaultValue;
        }
    }

    #endregion
}