using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;

namespace FileShare_EFCore.Database
{
    /// <summary>
    /// 数据库服务注册扩展 —— 在 Program.cs 中一行配置数据库。
    /// </summary>
    public static class DatabaseExtensions
    {
        /// <summary>
        /// 注册数据库上下文及相关服务。
        /// </summary>
        /// <typeparam name="TContext">继承自 AppDbContext 的业务 DbContext</typeparam>
        public static IServiceCollection AddAppDatabase<TContext>(
            this IServiceCollection services,
            DatabaseConfiguration config)
            where TContext : AppDbContext
        {
            // 注册配置
            services.AddSingleton(config);

            if (typeof(TContext) == typeof(AppDataContext))
            {
                services.AddProviderAppDataContext(config);
                services.AddScoped<DatabaseManager<TContext>>();

                return services;
            }

            // 注册 DbContext
            services.AddDbContext<TContext>(options =>
            {
                AppDbContext.ConfigureProvider(options, config);
            });

            // 注册数据库管理器
            services.AddScoped<DatabaseManager<TContext>>();

            return services;
        }

        /// <summary>
        /// 根据 <see cref="DatabaseConfiguration.Provider"/> 注册对应具体类型的 <see cref="AppDataContext"/> 实现。
        /// </summary>
        /// <param name="services">服务集合。</param>
        /// <param name="config">数据库配置。</param>
        /// <exception cref="NotSupportedException">数据库提供程序未注册时抛出。</exception>
        private static void AddProviderAppDataContext(this IServiceCollection services, DatabaseConfiguration config)
        {
            switch (config.Provider)
            {
                case DatabaseProvider.SQLite:
                    services.AddDbContext<AppDataContext, SqliteAppDataContext>(options =>
                        AppDbContext.ConfigureProvider(options, config));
                    break;
                case DatabaseProvider.SqlServer:
                    services.AddDbContext<AppDataContext, SqlServerAppDataContext>(options =>
                        AppDbContext.ConfigureProvider(options, config));
                    break;
                case DatabaseProvider.PostgreSQL:
                    services.AddDbContext<AppDataContext, PostgreSqlAppDataContext>(options =>
                        AppDbContext.ConfigureProvider(options, config));
                    break;
                case DatabaseProvider.MySQL:
                    services.AddDbContext<AppDataContext, MySqlAppDataContext>(options =>
                        AppDbContext.ConfigureProvider(options, config));
                    break;
                default:
                    throw new NotSupportedException($"数据库提供程序 {config.Provider} 未注册。");
            }
        }

        /// <summary>
        /// 初始化数据库（在应用启动时调用一次）。
        /// </summary>
        public static IServiceProvider InitializeDatabase<TContext>(
            this IServiceProvider serviceProvider,
            Action<TContext, IServiceProvider?>? seeder = null)
            where TContext : AppDbContext
        {
            using var scope = serviceProvider.CreateScope();
            var dbManager = scope.ServiceProvider.GetRequiredService<DatabaseManager<TContext>>();

            // 同步等待初始化（启动时阻塞）
            dbManager.InitializeAsync(seeder).GetAwaiter().GetResult();

            return serviceProvider;
        }
    }
}