Connected.Framework/Connected.Data/Schema/Sql/TableRecreate.cs

namespace Connected.Data.Schema.Sql
{
    internal class TableRecreate : TableTransaction
	{
		public TableRecreate(ExistingSchema existing)
		{
			Existing = existing;
		}

		private ExistingSchema Existing { get; }

		protected override async Task OnExecute()
		{
			var add = new TableCreate(true);

			await add.Execute(Context);

			await ExecuteDefaults(add.TemporaryName);

			if (HasIdentity)
				await new IdentityInsert(add.TemporaryName, true).Execute(Context);

			await new DataCopy(Existing, add.TemporaryName).Execute(Context);

			if (HasIdentity)
				await new IdentityInsert(add.TemporaryName, false).Execute(Context);

			await new TableDrop().Execute(Context);
			await new TableRename(add.TemporaryName).Execute(Context);

			await ExecutePrimaryKey();
			await ExecuteIndexes();
		}

		private bool HasIdentity
		{
			get
			{
				foreach (var column in Context.Schema.Columns)
				{
					if (column.IsPrimaryKey && column.IsIdentity)
						return true;
				}

				return false;
			}
		}

		private async Task ExecutePrimaryKey()
		{
			var pk = Context.Schema.Columns.FirstOrDefault(f => f.IsPrimaryKey);

			if (pk != null)
				await new PrimaryKeyAdd(pk).Execute(Context);
		}

		private async Task ExecuteDefaults(string tableName)
		{
			foreach (var column in Context.Schema.Columns)
			{
				if (!string.IsNullOrWhiteSpace(column.DefaultValue))
					await new DefaultAdd(column, tableName).Execute(Context);
			}
		}

		private async Task ExecuteIndexes()
		{
			var indexes = ParseIndexes(Context.Schema);

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