using System.Text;

namespace Connected.Data.Schema.Sql
{
    internal class ColumnDrop : ColumnTransaction
	{
		public ColumnDrop(ISchemaColumn column, ExistingSchema existing) : base(column)
		{
			Existing = existing;
		}

		private ExistingSchema Existing { get; }

		protected override async Task OnExecute()
		{
			if (!string.IsNullOrWhiteSpace(Column.DefaultValue))
				await new DefaultDrop(Column).Execute(Context);

			var indexes = Existing.ResolveIndexes(Column.Name);

			foreach (var index in indexes)
				await new IndexDrop(index).Execute(Context);

			await Context.Execute(CommandText);
		}

		private string CommandText
		{
			get
			{
				var text = new StringBuilder();

				text.AppendLine($"ALTER TABLE {Escape(Context.Schema.SchemaName(), Context.Schema.Name)} DROP COLUMN {Column.Name};");

				return text.ToString();
			}
		}
	}
}