DbConnectionFactory.cs

namespace Open.Database.Extensions;

/// <summary>
/// DbConnection factory implementation that accepts a factory function.
/// </summary>
public class DbConnectionFactory : IDbConnectionFactory
{
	/// <summary>
	/// Constructs a DbConnectionFactory.
	/// </summary>
	/// <param name="factory">The factory function.</param>
	protected DbConnectionFactory(Func<IDbConnection> factory)
	{
		_factory = factory ?? throw new ArgumentNullException(nameof(factory));
		Contract.EndContractBlock();
	}

	readonly Func<IDbConnection> _factory;

	/// <summary>
	/// Creates a connection of from the underlying factory function.
	/// </summary>
	public IDbConnection Create() => _factory();

	/// <summary>
	/// Creates a Non-Generic DbConnectionFactory.
	/// </summary>
	/// <param name="factory">The factory function.</param>
	/// <returns>A Non-Generic DbConnectionFactory</returns>
	public static DbConnectionFactory<TConnection> Create<TConnection>(Func<TConnection> factory)
		where TConnection : IDbConnection
		=> new(factory);

	/// <summary>
	/// Implicitly converts a connection factory function to a connection factory instance.
	/// </summary>
	/// <param name="factory">The factory function.</param>
	public static implicit operator DbConnectionFactory(Func<IDbConnection> factory)
		=> Create(factory);
}

/// <summary>
/// Generic connection factory implementation that accepts a factory function.
/// </summary>
/// <typeparam name="TConnection">The connection type.</typeparam>
public class DbConnectionFactory<TConnection>
	: DbConnectionFactory, IDbConnectionFactory<TConnection>
	where TConnection : IDbConnection
{
	readonly Func<TConnection> _factory;

	/// <summary>
	/// Constructs a DbConnectionFactory.
	/// </summary>
	/// <param name="factory">The factory function.</param>
	public DbConnectionFactory(Func<TConnection> factory)
		: base(() => factory())
	{
		_factory = factory ?? throw new ArgumentNullException(nameof(factory));
		Contract.EndContractBlock();
	}

	IDbConnection IDbConnectionFactory.Create() => Create();

	/// <summary>
	/// Creates a connection of from the underlying factory function.
	/// </summary>
	public new TConnection Create() => _factory();

	/// <summary>
	/// Implicitly converts a connection factory function to a genetic-typed connection factory instance.
	/// </summary>
	/// <param name="factory"></param>
	public static implicit operator DbConnectionFactory<TConnection>(Func<TConnection> factory)
		=> Create(factory);
}