using Microsoft.EntityFrameworkCore.Design;

namespace FileShare_EFCore.Database
{
    /// <summary>
    /// 设计时 DbContext 工厂，用于 EF Core 迁移工具生成迁移代码。
    /// </summary>
    public class AppDataContextFactory : IDesignTimeDbContextFactory<AppDataContext>
    {
        /// <summary>
        /// 创建用于设计时的 AppDataContext 实例，默认使用 SQLite 提供程序。
        /// </summary>
        /// <param name="args">命令行参数。</param>
        /// <returns>配置好的数据上下文实例。</returns>
        public AppDataContext CreateDbContext(string[] args)
        {
            return new AppDataContext(DesignTimeDatabaseConfiguration.Create(args));
        }
    }

    /// <summary>
    /// SQLite 迁移设计时工厂。
    /// </summary>
    public sealed class SqliteAppDataContextFactory : IDesignTimeDbContextFactory<SqliteAppDataContext>
    {
        /// <inheritdoc />
        public SqliteAppDataContext CreateDbContext(string[] args)
            => new(DesignTimeDatabaseConfiguration.Create(args, DatabaseProvider.SQLite));
    }

    /// <summary>
    /// SQL Server 迁移设计时工厂。
    /// </summary>
    public sealed class SqlServerAppDataContextFactory : IDesignTimeDbContextFactory<SqlServerAppDataContext>
    {
        /// <inheritdoc />
        public SqlServerAppDataContext CreateDbContext(string[] args)
            => new(DesignTimeDatabaseConfiguration.Create(args, DatabaseProvider.SqlServer));
    }

    /// <summary>
    /// PostgreSQL 迁移设计时工厂。
    /// </summary>
    public sealed class PostgreSqlAppDataContextFactory : IDesignTimeDbContextFactory<PostgreSqlAppDataContext>
    {
        /// <inheritdoc />
        public PostgreSqlAppDataContext CreateDbContext(string[] args)
            => new(DesignTimeDatabaseConfiguration.Create(args, DatabaseProvider.PostgreSQL));
    }

    /// <summary>
    /// MySQL 迁移设计时工厂。
    /// </summary>
    public sealed class MySqlAppDataContextFactory : IDesignTimeDbContextFactory<MySqlAppDataContext>
    {
        /// <inheritdoc />
        public MySqlAppDataContext CreateDbContext(string[] args)
            => new(DesignTimeDatabaseConfiguration.Create(args, DatabaseProvider.MySQL));
    }

    /// <summary>
    /// 为设计时工具（dotnet ef migrations）提供数据库连接配置。
    /// </summary>
    internal static class DesignTimeDatabaseConfiguration
    {
        /// <summary>
        /// 解析命令行参数中的 --provider 选项，创建对应的 <see cref="DatabaseConfiguration"/>。
        /// 未指定提供程序时默认使用 SQLite。
        /// </summary>
        /// <param name="args">命令行参数。</param>
        /// <param name="defaultProvider">未指定时的默认数据库提供程序。</param>
        /// <returns>对应数据库提供程序的配置。</returns>
        public static DatabaseConfiguration Create(string[] args, DatabaseProvider defaultProvider = DatabaseProvider.SQLite)
        {
            DatabaseProviderRegistry.RegisterDefaults();

            var provider = GetProvider(args) ?? defaultProvider;
            return provider switch
            {
                DatabaseProvider.SQLite => DatabaseConfiguration.ForSQLite("fileshare-api.db"),
                DatabaseProvider.SqlServer => DatabaseConfiguration.ForSqlServer("(localdb)\\MSSQLLocalDB", "FileShareApi"),
                DatabaseProvider.PostgreSQL => DatabaseConfiguration.ForPostgreSQL("localhost", "fileshare_api", "postgres", "postgres"),
                DatabaseProvider.MySQL => DatabaseConfiguration.ForMySQL("localhost", "fileshare_api", "root", "root"),
                _ => DatabaseConfiguration.ForSQLite("fileshare-api.db"),
            };
        }

        /// <summary>
        /// 从命令行参数中解析 --provider 选项的值。
        /// 支持 <c>--provider sqlite</c> 和 <c>--provider=sqlite</c> 两种格式。
        /// </summary>
        /// <param name="args">命令行参数。</param>
        /// <returns>解析到的数据库提供程序，未指定或无法识别时返回 null。</returns>
        private static DatabaseProvider? GetProvider(string[] args)
        {
            for (var i = 0; i < args.Length; i++)
            {
                var arg = args[i];
                string? value = null;

                if (arg.Equals("--provider", StringComparison.OrdinalIgnoreCase) && i + 1 < args.Length)
                {
                    value = args[i + 1];
                }
                else if (arg.StartsWith("--provider=", StringComparison.OrdinalIgnoreCase))
                {
                    value = arg["--provider=".Length..];
                }

                if (!string.IsNullOrWhiteSpace(value)
                    && Enum.TryParse<DatabaseProvider>(value, ignoreCase: true, out var provider))
                {
                    return provider;
                }
            }

            return null;
        }
    }
}